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Introduction

Psoriasis is a chronic, immune-mediated inflammatory skin disease, with a global prevalence of approximately 2% to 3%. It is often associated with significant physical, psychological, and social burdens.¹ It typically follows a course of remission and recurrence; many patients only experience mild rash flares, but some may have a longer disease duration before receiving more intensive treatment.² The present treatment approach uses a step-up regimen—starting with topical drugs, progressing to phototherapy, and reserving systemic drugs for patients with poor control under conventional treatment.^3,4 This method minimizes overtreatment of mild disease but often delays effective systemic intervention until the disease has persisted for a longer duration. This raises the question whether early systemic treatment could yield better outcomes?

In recent years, systemic therapy, including traditional drugs such as methotrexate and acitretin, as well as biologics targeting specific inflammatory pathways, have significantly improved patients’ symptoms.^5–9 However, the response to systemic therapy varies greatly among individuals, influenced by multiple factors including disease severity, comorbidities, age of onset, treatment history, and family history.^10–12 In other chronic immune-mediated inflammatory diseases, like Crohn’s disease and rheumatoid arthritis, researchers have reported the role of disease duration on treatment response, with early use of systemic treatments leading to better clinical outcomes.^13,14 Similar to psoriasis, earlier systemic therapy may have greater advantages. However, there is still a lack of study data on the impact of disease duration on systemic therapy outcomes in psoriasis.

To our knowledge, large-scale, real-world studies specifically designed to investigate the influence of psoriasis disease duration on treatment outcomes are lacking. Previous studies have not addressed whether the duration of psoriasis affects treatment efficacy in clinical practice. Additionally, it is unclear whether the chronicity of the disease alters the efficacy of specific systemic therapies. This lack of evidence limits the development of personalized treatment strategies, particularly for patients with long-term disease.

To address this issue, this multicenter prospective observational study utilized data from the SPEECH registry to explore whether early systemic therapy truly improves clinical or patients reported outcomes. Patients with moderate-to-severe psoriasis were stratified into three groups based on disease duration at enrollment: short duration (<2 years), medium duration (2–10 years), and long duration (>10 years). Participants received various systemic therapies, including biologics, methotrexate, and acitretin. Although treatment switching may occur in clinical practice, our analyses focused on patients who maintained a single systemic therapy for at least six months, thereby ensuring reliable evaluation of treatment response. Furthermore, we examined potential contributors to disease progression, including treatment type, patient demographics, and clinical characteristics, to explore whether specific therapies were associated with greater disease stability or risk of deterioration. This study provides novel insights into the relationship between psoriasis disease course and systemic therapy efficacy in real clinical settings.

Material and Methods

Study Design

The SPEECH registry is a multicenter prospective observational study that records the clinical features of psoriasis in the Chinese population and the safety and efficacy of different treatment methods such as biologics, conventional systemic therapy, and phototherapy.¹⁵ The SPEECH registry is registered at seven dermatology centers in Shanghai, China. All data were prospectively collected at each visit using standardized case report forms and entered into a central electronic database by trained dermatology staff to ensure data completeness and accuracy. This study received ethical approval from the Institutional Review Board of Shanghai Dermatology Hospital (#2020-36), along with approvals from the ethics committees of all other participating centers.

Participants

All participants in this study are selected from the SPEECH cohort and met the following inclusion criteria: 1. Adults diagnosed with moderate-to-severe plaque psoriasis who were treated with biologic agents (such as guselkumab, ustekinumab, ixekizumab, secukinumab, or adalimumab), methotrexate, or acitretin; 2. Treatment was administered according to established protocols without modifications in dosage or treatment intervals. To ensure reliable evaluation of treatment response, only patients who remained on a single systemic therapy for at least six months were included in the analysis. Key exclusion criteria are the absence of baseline information on disease duration (Figure 1).

Data Collection and Outcome Measures

Demographic and clinical data were drawn from all participants at baseline, including age, gender, education level, disease duration, family history of psoriasis, BMI, lifestyle (smoking, drinking), early-onset psoriasis (age of onset <40 years), comorbidities (obesity, psoriatic arthritis, hyperlipidemia, and hypertension). To ensure consistency, treatment adherence and clinical assessments were regularly recorded and reviewed at each visit by om-site investigators.

Additionally, disease characteristics were assessed using measures such as Psoriasis Area and Severity Index (PASI), Body Surface Area (BSA), Dermatology Life Quality Index (DLQI), Physician Global Assessment (PGA), Patient Global Assessment (PtGA), Hospital Anxiety and Depression Scale – Anxiety (HADS-A) and Depression (HADS-D). Treatment efficacy was assessed at 3 months (12 weeks) and 6 months (28 weeks) after treatment, using criteria such as the PASI 75 (≥75% improvement in PASI), BSA <1/3 (clear to almost clear), PGA 0/1 (clear to almost clear), DLQI 0/1 (little to no impact on life), PtGA 0/1 (clear to almost clear), and HADS-A or HADS-D = 0 (complete resolution of anxiety or depression symptoms) at 3 months and 6 months post-treatment.

Statistical Analyses

The primary analysis used a modified intention-to-treat (mITT) dataset and employed multiple imputation to fill in the missing treatment efficacy data. By grouping patients according to disease duration (<2 years, 2~10 years, and ≥10 years). Continuous variable hypothesis Follow a normal distribution, represented by the mean (SD), and statistical comparisons are conducted using the Student’s t-test. Non-normally distributed continuous variables are represented as median (interquartile range) and compared using the Mann–Whitney U-test. Categorical variables are expressed as n (%), and analyzed using the χ2 test or Fisher’s exact probability method. Using the group with a disease duration of <2 years as a reference, logistic regression analysis was employed to evaluate the treatment response of patients with different disease durations. The adjusted odds ratio (aOR) and its 95% confidence interval (CI) were computed. To visualize response trends, line charts were generated, and intergroup differences were assessed using the Kruskal–Wallis and Dwass–Steel–Critchlow–Fligner (DSCF) tests. Additionally, subgroup analyses were performed to investigate potential interactions and factors. Sensitivity analysis was conducted based on the per-protocol (PP) dataset to further validate the robustness of the study findings. All statistical models were adjusted for potential confounders, such as gender, age, education level, early-onset psoriasis, family history of psoriasis, psoriatic arthritis (PsA), obese (BMI>28), baseline PASI, BSA score, different categories of treatment drugs, the hospital to which the patient belonged, and prior systemic therapy history. Statistical analyses were performed with R software version 4.2.2, and results with p-value <0.05 were deemed statistically significant.

Results

Clinical Characteristics According to Disease Duration

Among the initially registered 2470 patients, 1947 fulfilled the inclusion criteria for this analysis. Due to incomplete baseline information, 39 patients were excluded, leaving 1908 patients eligible for the final analysis (Figure 1). Participants were divided into three groups based on the duration of the disease: <2 years, 2~10 years, and ≥10 years. In the comparison of baseline characteristics across the three patient groups, it was noted that patients in the short disease duration group (<2 years) had more females (29.1% vs 18.3% vs 25.0%), higher education levels, more obesity (24.1% vs 19.0% vs 16.8%). In addition, patients in the short disease duration group had lower baseline PASI and BSA scores. Moreover, patients in the long disease duration group (≥10 years) were more likely to receive biologic therapy and had early-onset psoriasis (p <0.05). There were no significant differences in the remaining covariates (Table 1).

Table 1 Demographic and Patient Characteristics of the Study Cohort

Comparison of Treatment Efficacy

Using univariate logistic regression analysis to compare the efficacy outcomes among the three disease duration groups. In the unadjusted analysis, at 3 months, there were no significant differences in the proportions of the three different disease duration groups achieving BSA <1/3, PGA 0/1, PASI 75, DLQI 0/1, PtGA 0/1, HADS-A = 0, and HADS-D = 0. Even after adjusting for relevant covariates, these results remained non-significant (Table 2). Moreover, the results of the above at 6 months were similar, except that the PASI75 response rate was lower in the long disease duration group, but the adjusted OR showed no significant difference (Table 3).

Table 2 Comparison of Clinical Efficacy and Psychological Outcome of Systemic Therapy in Different Disease Duration at 3 Months

Table 3 Compare of Clinical Efficacy and Psychological Outcome of Systemic Therapy in Different Disease Duration at 6 Months

The Kruskal–Wallis and DSCF tests were used to assess intergroup differences, and line graphs were used to illustrate the changes of various treatment outcomes over time in the three groups (Figure 2). The results showed that, except for the baseline, there were almost no significant differences in the outcomes at each time point among the three groups. Moreover, all three groups exhibited downtrend of the outcomes over time, reinforcing the consistency of treatment efficacy irrespective of disease duration. This underscored the stability of systemic therapy outcomes across different disease durations.

Figure 2 Line graphs comparing treatment outcomes over time among three groups. (A) Line graphs of PSAI score and time; (B) Line graphs of BSA score and time; (C) Line graphs of DLQI score and time; (D) Line graphs of PGA score and time; (E) PASI, Line graphs of PtGA score and time. **, p<0.01; ***, p<0.001. Abbreviations: PASI, Psoriasis Area and Severity Index; BSA, Body Surface Area; DLQI, Dermatology Life Quality Index; PGA, Physician’s Global Assessment. PtGA, Patient Global Assessment.

When using PASI75 as the primary efficacy endpoint, subgroup analyses showed no significant interaction between baseline variables and disease duration categories (p for interaction >0.05; Figures S1 and S2). Similarly, no significant interaction was observed between treatment type or prior systemic therapy history and disease duration in terms of treatment outcomes, indicating that the efficacy of systemic therapy is not affected by disease duration. These results support the robustness and consistency of our primary analysis.

Sensitivity Analysis

Sensitivity analysis was also performed to verify the reliability of our results using the PP dataset. Disease duration was categorized into two groups based on the median: <15 years and ≥15 years. Both univariate and multivariate logistic regression analyses showed no significant difference in efficacy between the two groups (Tables S1 and S2). Furthermore, we conducted a hierarchical analysis according to treatment type (traditional agents vs biologics) and prior systemic therapy exposure. As presented in Tables S3 and S4, the results showed no significant differences in PASI75 response among different disease duration groups within eachstratum. The Mantel-Haenszel pooled estimates further demonstrated no significant heterogeneity across strata. The results showed that disease duration did not affect the efficacy of systemic therapies, regardless of treatment type or prior systemic therapy, supporting the robustness and consistency of our primary analysis.

Discussion

This large-scale, prospective, multicenter study provides valuable evidence on psoriasis management and treatment patterns, with patients receiving systemic therapy in routine clinical settings at seven hospitals in Shanghai, China. This study provides valuable insights into how disease duration affects clinical features and treatment outcomes of systemic therapy in Chinese psoriasis patients. Patients were divided into three groups based on disease duration: <2 years, 2–10 years, and ≥10 years. A key finding of our study is that our study showed no significant correlation between disease duration and treatment response in terms of clinical efficacy (PASI75, PGA 0/1, BSA <3) and patients reported outcomes (DLQI 0/1, PtGA 0/1, HADS-A=0, HADS-D=0) at both 3 months and 6 months. This conclusion remained robust after adjusting for relevant covariates, and sensitivity analysis further verified the reliability of the results.

We observed that patients with a short disease duration (<2 years) had higher education levels, more female patients, more obese patients, and lower baseline PASI and BSA scores. However, these characteristics did not affect the treatment outcomes. Notably, patients with a longer disease duration were more likely to receive biological therapy and present with early-onset psoriasis, both of which usually associated with increased disease severity or longer treatment exposure. This is consistent with the findings from the British Association of Dermatologists Biologic Interventions Register (BADBIR), where longer disease duration was observed with biologics compared to traditional systemic therapy (23 vs 19 years, p <0.001).¹⁶

Our findings were consistent with prior clinical studies indicating that disease duration cannot independently predict the response to systemic or biological therapy. Most available studies have focused on biologics, consistently showing that treatment response is unaffected by disease duration. For instance, a prospective cohort study of 118 patients receiving etanercept found no significant difference in PASI improvement at week 24 between between patients with disease durations <20 years versus ≥20 years (p = 0.170).¹⁷ Similarly, in another retrospective cohort study involving 135 patients receiving guselkumab, Hung et al reported no correlation between PASI 75 response and disease duration at week 36 (OR: 0.99, 95% CI 0.94–1.05), with comparable mean durations among responders and non-responders (18.42 vs 18.91 years).¹⁸ Post-hoc analysis of large RCTs, including the NAVIGATE and VOYAGE trials (n = 1678), indicated that the disease duration (<15 years vs ≥15 years) was not significantly associated with the PASI 90 response at week 40 (OR: 1.13, 95% CI: 0.88–1.47).¹⁹ Furthermore, a recent meta-analysis including 4,649 patients found that disease duration was not significantly associated with biologic treatment response (OR 0.99, 95% CI 0.98–1.00, p=0.17), reinforcing that systemic therapy efficacy is generally independent of disease duration.²⁰

Evidence regarding traditional systemic therapies is comparatively limited, but appears to suggest a similar trend. In our subgroup analyses, disease duration did not significantly influence treatment outcomes with methotrexate or acitretin. Although real-world evidence from prior studies has demonstrated the effectiveness of traditional systemic therapies in patients with moderate-to-severe psoriasis, they did not specifically evaluate whether disease duration influences treatment response. The BADBIR cohort identified predictors of reduced treatment effectiveness, including prior systemic exposure, male sex, comorbidities, and alcohol consumption, but disease duration was not among them.²¹ Similarly, a systematic review of traditional systemic therapies found no evidence that disease duration significantly modified treatment response.²² Additional analysis of treatment-switch patterns reported that disease duration did not affect the transition between traditional drugs and biologics.²³ Recent data further suggest that prior use of traditional drugs such as methotrexate or acitretin does not compromise the efficacy or drug survival of subsequent biologic therapy.²⁴ Collectively, these findings indicate that disease duration is not a major determinant of treatment outcomes for either traditional systemic agents or biologics. Importantly, prior exposure to traditional therapy does not diminish the effectiveness of subsequent biologics, thereby supporting the rationale for a step-up therapeutic strategy in clinical practice.

Although our research results indicated that early systemic therapy does not improve treatment outcomes in actual clinical settings, some studies report that early systemic treatment can actively control systemic inflammation to prevent or delay damage related to comorbidities, including psoriatic arthritis (PsA) and cardiovascular diseases.^25–29 Two different cohort studies indicated that compared to patients receiving phototherapy or topical medication, those undergoing systemic treatment have a significantly reduced risk of developing PsA.^25,26 Furthermore, new evidence suggested that biological therapy is beneficial in reversing the potential pathogenic processes of cardiovascular diseases, such as endothelial dysfunction and the progression of atherosclerotic plaques. In a large retrospective study, Song WJ et al found that compared to phototherapy, biologic therapy and non-biologic systemic therapy reduce the risk of new-onset MACE in psoriasis patients.²⁷ In order to determine whether early systemic intervention has a protective effect on psoriatic arthritis, or cardiovascular diseases, as well as whether these potential benefits make it worthwhile to upgrade treatment earlier, more long-term longitudinal studies are necessary in the future.

This study indicated that the early effectiveness of systemic therapy for psoriasis remains consistent, regardless of the disease duration, which may be related to the ability of biologics to modulate chronic inflammatory pathways and resident memory T cells in long-standing disease.^30,31 This suggests that even patients with long-standing psoriasis or delayed treatment initiation can achieve meaningful clinical responses, supporting the use of systemic therapy irrespective of disease duration.

Our research underscore that initiating systemic therapy early does not lead to better outcomes, and this observation supports the widely accepted step-up treatment strategy in current clinical practice.³² Using systemic therapy for patients with poor response to topical treatment and phototherapy reduces unnecessary systemic drug exposure and its associated costs and risks.⁴ In the absence of aggressive disease characteristics or rapid progression of joint involvement, systemic therapy may not need to be initiated immediately based solely on the disease duration. Conversely, the severity of the disease, the burden of symptoms, and the impairment of quality of life still be the main factors influencing clinical judgements. These findings provided clinical practice evidence, highlighting the importance of gradually and individually escalating systemic therapy regimens in the management of psoriasis.

It is important to recognize the limitations inherent in our study. First, like many observational studies, our analysis may be susceptible to various biases, including selection bias and unmeasured confounding factors. Second, the study cohort only included Chinese patients, which limits the generalizability of the results. Third, although a follow-up period of 6 months offers notable findings on early responses to treatment, it does not provide information on the long-term efficacy of systemic therapy or the potential effects of disease duration on outcomes such as comorbidities. Therefore, extended longitudinal follow-up is necessary to evaluate these crucial aspects.

Conclusion

Our research findings demonstrates that the short-term efficacy of systemic therapy is consistent across different disease durations, supporting the “step-up” treatment strategy in psoriasis management. This multicenter evidence adds new insights by comparing traditional agents and biologics, showing that disease duration does not alter systemic therapy response. However, emerging evidence suggests that early systemic therapy may provide long-term benefits in preventing psoriatic arthritis and major cardiovascular events. Future long-term prospective studies are needed to determine whether early systemic interventions have a protective effect on comorbidities and to refine personalized treatment plans to balance the benefits for skin and quality of life with the prevention of systemic comorbidities.

Data Sharing Statement

The dataset supporting this research can be obtained from the corresponding author upon reasonable request.

Ethics Statement

This study was approved by the medical ethics committees of the following institutions: Shanghai Skin Disease Hospital (approval No. 2020-36), Shanghai Sixth People’s Hospital (approval No.2020-KY-047K), Shanghai Changzheng Hospital (approval No.2020-27), and Shanghai Tenth People’s Hospital (approval No.20KT110). All participants provided written informed consent for the publication of their clinical data. The study was conducted in accordance with the principles of the Declaration of Helsinki.

Author Contributions

Min Dai, Yuxiong Jiang, Yujing Xi and Lezhen Xu are co-first authors. All authors made a significant contribution to the work reported, whether in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising, or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Funding

This work was sponsored by grants from the National Key Research and Development Program of China (2023YFC2508106), National Natural Science Foundation of China (No. 82430101, 82273510), Innovation Program of Shanghai Municipal Education Commission (No. 2025GDZKZD06), Shanghai Dermatology Research Center (2023ZZ02017), Clinical Research Plan of SHDC (No. SHDC22022302).

Disclosure

The authors declare no conflicts of interest.

References

1. Griffiths CEM, Armstrong AW, Gudjonsson JE, Barker JNWN. Psoriasis. Lancet. 2021;397(10281):1301–1315. doi:10.1016/S0140-6736(20)32549-6

2. Ma LF. Inflammatory memory in psoriasis: from remission to recurrence. J Allergy Clin Immunol. 2024;154(1):1.

3. Gisondi P, Del Giglio M, Girolomoni G. Treatment Approaches to Moderate to Severe Psoriasis. Int J Mol Sci. 2017;18(11):2427. doi:10.3390/ijms18112427

4. Chinese Society of Dermatology, China Dermatologist Association, Dermatology & Venereology Specialized Committee of Chinese Association of Integrative Medicine. Guidelines for the treatment of psoriasis with biologics and small-molecule drugs in China (2024). Chin J Dermatol. 2024;57(11):976–997.

5. Sugumaran D, Yong ACH, Stanslas J. Advances in psoriasis research: from pathogenesis to therapeutics. Life Sci. 2024;355:122991. doi:10.1016/j.lfs.2024.122991

6. Lebwohl M. Advances in biologic therapy of psoriasis. J Eur Acad Dermatol Venereol. 2023;37(9):1689–1690. doi:10.1111/jdv.19287

7. Lee HJ, Kim M. Challenges and Future Trends in the Treatment of Psoriasis. Int J Mol Sci. 2023;24(17):13313. doi:10.3390/ijms241713313

8. Alabas OA, Mason KJ, Yiu ZZN, et al. Effectiveness and survival of methotrexate versus Adalimumab in patients with moderate-to-severe psoriasis: a cohort study from the British Association of Dermatologists Biologics and Immunomodulators Register (BADBIR). Br J Dermatol. 2023;189(3):271–278. doi:10.1093/bjd/ljad179

9. Armstrong AW, Pathophysiology RC. Clinical Presentation, and Treatment of Psoriasis: a Review. JAMA. 2020;323(19):1945–1960. doi:10.1001/jama.2020.4006

10. Huang D, Zhong X, Jiang Y, et al. Insulin resistance impairs biologic agent response in moderate-to-severe plaque psoriasis: insights from a prospective cohort study in China. Br J Dermatol. 2024;191(4):616–623. doi:10.1093/bjd/ljae147

11. Jiang Y, Liu X, Ma R, et al. The Impact of Family History on Clinical Presentation and Biologic Treatment Response in Patients with Psoriasis: a Multicenter Prospective Cohort Study. Am J Clin Dermatol. 2025;26(2):291–300. doi:10.1007/s40257-025-00918-y

12. Jiang Y, Chen Y, Yu Q, Shi Y. Biologic and Small-Molecule Therapies for Moderate-to-Severe Psoriasis: focus on Psoriasis Comorbidities. BioDrugs. 2023;37(1):35–55. doi:10.1007/s40259-022-00569-z

13. Deane KD, Holers VM. Rheumatoid Arthritis Pathogenesis, Prediction, and Prevention: an Emerging Paradigm Shift. Arthritis Rheumatol. 2021;73(2):181–193. doi:10.1002/art.41417

14. Berg DR, Colombel JF, Ungaro R. The Role of Early Biologic Therapy in Inflammatory Bowel Disease. Inflamm Bowel Dis. 2019;25(12):1896–1905. doi:10.1093/ibd/izz059

15. Yu N, Peng C, Zhou J, et al. Measurement properties of the patient global assessment numerical rating scale in moderate-to-severe psoriasis. Br J Dermatol. 2023;189(4):437–446. doi:10.1093/bjd/ljad188

16. Iskandar IYK, Ashcroft DM, Warren RB, et al. Demographics and disease characteristics of patients with psoriasis enrolled in the British Association of Dermatologists Biologic Interventions Register. Br J Dermatol. 2015;173(2):510–518. doi:10.1111/bjd.13908

17. Antoniou C, Dessinioti C, Stratigos A, Avgerinou G, Stavropoulos P, Katsambas A. Etanercept in severe, recalcitrant psoriasis: clinical response, safety profile and predictors of response based on a single institution’s experience. J Eur Acad Dermatol Venereol. 2009;23(8):979–982. doi:10.1111/j.1468-3083.2009.03093.x

18. Hung YT, Lin YJ, Chiu HY, Huang YH. Impact of previous biologic use and body weight on the effectiveness of guselkumab in moderate-to-severe plaque psoriasis: a real-world practice. Ther Adv Chronic Dis. 2021;12:20406223211046685. doi:10.1177/20406223211046685

19. Diels J, Thilakarathne P, Cameron C, McElligott S, Schubert A, Puig L. Adjusted treatment COMPArisons between guSelkumab and uStekinumab for treatment of moderate-to-severe plaque psoriasis: the COMPASS analysis. Br J Dermatol. 2020;183(2):276–284. doi:10.1111/bjd.18634

20. Hjort G, Schwarz CW, Skov L, et al. Clinical characteristics associated with response to biologics in the treatment of psoriasis: a meta-analysis. JAMA Dermatol. 2024;160(8):830–837. doi:10.1001/jamadermatol.2024.1677

21. Warren RB, Smith CH, Yiu ZZN, et al. Effectiveness and persistence of Acitretin, ciclosporin, fumaric acid esters and methotrexate for patients with moderate-to-severe psoriasis: a cohort study from BADBIR. Br J Dermatol. 2015;172(2):337–346. doi:10.1111/bjd.13225

22. Iskandar IYK, Ashcroft DM, Warren RB, et al. Persistence and effectiveness of nonbiologic systemic therapies for moderate-to-severe psoriasis in adults: a systematic review. Br J Dermatol. 2016;174(3):606–617.

23. Tabolli S, Giannantoni P, Paradisi A, Abeni D. The ‘switcher’ patient profile in psoriasis treatment: from traditional to biological and from biological to traditional systemic drugs. Br J Dermatol. 2015;173(1):256–258. doi:10.1111/bjd.13560

24. Piaserico S, Cazzaniga S, Gisondi P, et al. “Full-naïve” patients: the impact of previous methotrexate, cyclosporine, and Acitretin on first-line biologics response in the treatment of moderate-to-severe psoriasis—a monocentric retrospective study. J Eur Acad Dermatol Venereol. 2021;35(5):e327–e330.

25. Gisondi P, Bellinato F, Targher G, Idolazzi L, Girolomoni G. Biological disease-modifying antirheumatic drugs may mitigate the risk of psoriatic arthritis in patients with chronic plaque psoriasis. Ann Rheum Dis. 2022;81(1):68–73. doi:10.1136/annrheumdis-2021-219961

26. Felquer MLA, LoGiudice L, Galimberti ML, Rosa J, Mazzuoccolo L, Soriano ER. Treating the skin with biologics in patients with psoriasis decreases the incidence of psoriatic arthritis. Ann Rheumatic Dis. 2022;81(1):74–79. doi:10.1136/annrheumdis-2021-220865

27. Rosenthal YS, Schwartz N, Sagy I, Pavlovsky L. Incidence of Psoriatic Arthritis Among Patients Receiving Biologic Treatments for Psoriasis: a Nested Case–Control Study. Arthritis Rheumatol. 2022;74(2):237–243. doi:10.1002/art.41946

28. Song WJ, Oh S, Yoon HS. Association between biologic and nonbiologic systemic therapy for psoriasis and psoriatic arthritis and the risk of new-onset and recurrent major adverse cardiovascular events: a retrospective cohort study. J Am Acad Dermatol. 2025;93(1):S0190–9622(25)00524–9. doi:10.1016/j.jaad.2025.03.055

29. Reich K, Griffiths CEM, Gordon KB, et al. Maintenance of clinical response and consistent safety profile with up to 3 years of continuous treatment with guselkumab: results from the VOYAGE 1 and VOYAGE 2 trials. J Am Acad Dermatol. 2020;82(4):936–945. doi:10.1016/j.jaad.2019.11.040

30. Iversen L, Conrad C, Eidsmo L, et al. Secukinumab demonstrates superiority over narrow-band ultraviolet B phototherapy in new-onset moderate to severe plaque psoriasis patients: week 52 results from the STEPIn study. J Eur Acad Dermatol Venereol. 2023;37(5):1004–1016. doi:10.1111/jdv.18846

31. Schäkel K, Reich K, Asadullah K, et al. Early disease intervention with guselkumab in psoriasis leads to a higher rate of stable complete skin clearance (‘clinical super response’): week 28 results from the ongoing phase IIIb randomized, double-blind, parallel-group, GUIDE study. J Eur Acad Dermatol Venereol. 2023;37(10):2016–2027. doi:10.1111/jdv.19236

32. Committee on Psoriasis. Chinese Society of Dermatology. Guideline for the diagnosis and treatment of psoriasis in China (2023 edition). Chin Jl of Dermatology. 2023;56(7):573–625.

Introduction

V-pattern strabismus is one of the most common alphabetic patterns.¹ It involves a more convergent (or less divergent) horizontal deviation in downgaze than in upgaze and becomes clinically significant when vertical incomitance exceeds 15 prism diopters (Δ).²

Undoubtedly, in most cases, the V-pattern is associated with the presence of inferior oblique muscles overaction (IOOA), which leads not only to vertical and horizontal deviations but also to excyclodeviation. Excyclotorsion resulting from inferior oblique overaction is thought to contribute to the development of V-pattern strabismus by inducing extorsional displacement of the globes, thereby increasing horizontal divergence in downgaze.^3–5

Most V-patterns are, however, congenital or develop early in life, allowing suppression or anomalous retinal correspondence to prevent subjective awareness of excyclodeviation. Despite this, objective excyclotorsion in patients with V-pattern strabismus can be observed in fundus photographs, as shown in Figure 1.

Objective cyclotorsion is the measurable rotation of the eye around its visual axis, assessed using landmarks like the fovea and optic disc. The disc-foveal angle (DFA) is commonly measured via fundus photography, scanning laser ophthalmoscopy, or automated software, with studies comparing their accuracy and clinical utility.^6–9 In 2021 our team developed Cyclocheck, a web-based diagnostic tool (freely available at www.cyclocheck.com) for measuring objective cyclotorsion in both clinical and research settings and proved it to be a repeatable and reliable method for office based DFA assessment.^10,11 Figure 2 shows a screenshot of the Cyclocheck software interface.

Figure 2 Cyclocheck software interface.

Bilateral graded recession of the inferior oblique muscles effectively corrects V-pattern strabismus across varying degrees of their overaction.^12,13 It allows tailoring the surgical dosage according to IOOA severity and extent of V pattern, reducing both vertical and horizontal incomitance.^14–16 It has also been proven to have prominent incyclorotating effect in patients with various types of strabismus associated with IOOA.¹⁷ However, to the best of our knowledge, no study to date has evaluated the effect of bilateral inferior oblique graded recession on objective cyclotorsion asymmetry, specifically comparing the impact of symmetric and asymmetric surgeries.

This study aims to evaluate changes in objective cyclotorsion using Cyclocheck following bilateral graded inferior oblique recession in patients with V-pattern strabismus and inferior oblique overaction. It also aims to investigate the impact of symmetric and asymmetric surgeries on cyclotorsion asymmetry between the eyes.

Materials and Methods

This retrospective study analyzed consecutive cases of patients presenting (eso/exo) V-pattern strabismus (≥15 prism diopters difference in measurement between upgaze and downgaze) with IOOA who underwent bilateral inferior oblique muscle graded recession, with or without concurrent horizontal rectus surgery. Eligible participants demonstrated binocular vision and had no history of strabismus surgeries, including procedures on other vertically acting muscles. Informed consent was obtained from each participant. The recorded data included age, gender and the amount of V-pattern, defined as the difference between down- and upgaze. It also covered the amount of inferior oblique (IO) muscle recession in millimeters for each eye separately, the total recession for both eyes combined, and pre- and post-operative objective cyclotorsion measured by Cyclocheck using fundus photographs. Digital fundus photographs of both eyes of all study subjects were obtained using a DRS nonmydriatic fundus camera (CenterVue DRS Automatic Retinal Camera, Welch Allyn). All measurements were made before and 3 months following the surgery. Photographs were taken under binocular viewing conditions while the subject looked at an internal fixation target. A chin and forehead rest with side marks were used as a guide to ensure proper head position. The disc-foveal angle was calculated using a web-based diagnostic tool for assessing objective cyclotorsion named Cyclocheck.

The inferior oblique recession was classified as “symmetrical” when the same degree of recession was performed on both eyes, provided the vertical deviation in the primary position was less than 5 prism diopters. If hypertropia ranged from 5 to 10 prism diopters, the recession in the more hypertropic eye was increased by 2 mm; for 10 to 15 prism diopters, by 4 mm; and for 15 or more prism diopters, by 6 mm. The amount of inferior oblique muscle recession was determined based on the severity of overelevation in adduction: +1 IOOA corresponded to 8 mm of recession, +2 IOOA to 10 mm, +3 IOOA to 12 mm, and +4 IOOA to 14 mm.

All procedures performed in studies involving human participants conformed to all local laws and were by the ethical standards of the Bioethical Committee of the Medical University in Lodz, Poland and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. The study was approved by the Bioethical Committee of the Medical University in Lodz, Poland (RNN/260/23/KE).

Statistical Analysis

Comparisons were made using paired t-test and Wilcoxon signed-rank test. Normality of data distribution was assessed using the Shapiro–Wilk test. Paired t-tests were used for normally distributed variables, while non-normally distributed variables were analyzed using the Wilcoxon signed-rank test. Correlations between the variables were evaluated using the Pearson correlation coefficient (r). A Fisher’s z-test was used to examine the difference between two correlation coefficients. Statistical analysis was conducted using Python (Python Software Foundation, Netherlands). A p-value of ≤ 0.05 was considered statistically significant.

Results

A total of 50 patients (100 eyes) were included in the study. The gender distribution was comparable, with 26 females and 24 males. The mean age was 10.46 years. V-pattern esotropia was observed in 22 patients (44%), and exotropia in 28 patients (56%). All the patients enrolled in the study underwent uneventful bilateral inferior oblique muscle graded recession of 8, 10, 12 and 14 mm as detailed in the methodology section. The procedure was symmetrical in 21 cases and asymmetrical in 29 cases (22 by 2 mm, 5 by 4 mm and 2 by 6 mm). The mean inferior oblique recession in millimeters was 10.92±1.81 in the right eye and 10.92±1.94 in the left eye, with the bilateral absolute amount of 21.84±3.04. The amount of V-pattern decreased significantly in all cases, but a residual V-pattern was observed in 4 cases (8%) – 5-10 PD of vertical incomitance in 3 cases and 25PD in one case (the patient had preoperative V-pattern of 50PD). Clinical characteristics of the study participants are presented in Table 1.

Table 1 Clinical Characteristics of the Study Participants

A positive correlation was observed between the preoperative amount of V-pattern and preoperative absolute objective cyclotorsion (r=0.36, p=0.0093). This was no more valid postoperatively when absolute objective cyclotorsion had a light negative correlation with remnant V-pattern (r= −0.09, p=0.0001). A positive correlation was observed between the amount of IO recession and the change in absolute objective cyclotorsion (r = 0.46, p = 0.00), as shown in Figure 3. The mean reduction of objective cyclotorsion was 2.52° of cyclotorsion/ per 2 mm of recessed inferior oblique muscle. As shown in Figure 4, the total change of absolute objective cyclotorsion was moderately correlated with the reduction of the V-pattern (r=0.38, p=0.0032).

Figure 3 The correlation between the amount of inferior oblique recession and change in absolute objective cyclotorsion.

Figure 4 The correlation between the total change in absolute objective cyclotorsion and the reduction of the V-pattern.

A linear relationship was observed between the amount of inferior oblique recession in each eye separately and the change in objective cyclotorsion of the respective eye (right eye: r=0.37, p=0.0083; left eye: r=0.37, p=0.0087). The correlations were less evident than the one for both eyes, but they did not differ significantly (Fisher’s z-test 0.72 p=0.47). There was a positive correlation between the amount of preoperative objective cyclotorsion and the surgically induced change in objective cyclotorsion for each separate eye (Wilcoxon signed-rank test z= 6.452, p= <0.0001, Paired t test t= 5.1309, df= 54, p= <0.0001).

We also examined symmetric and asymmetric surgeries to assess their impact on cyclotorsion asymmetry between the eyes. Overall, the mean cyclotorsion asymmetry was significantly lower postoperatively (preoperative: 5.50°±3.40° vs postoperative: 4.00°±3.00°, p<0.001). However, this was independent of whether the surgery was symmetric or asymmetric. The influence on the amount of cyclotorsion asymmetry was similar in both groups (RE/LE difference: symmetric group 1.55°±4.15° and asymmetric group 1.47°±3.30°; p=0.938).

Discussion

Inferior oblique overaction (IOOA) and associated V-pattern strabismus present significant challenges in strabismus management, often requiring surgical intervention to restore ocular alignment and minimize torsional deviations. Our study contributes to the growing body of evidence supporting graded inferior oblique recession as an effective approach for reducing both objective cyclotorsion and V-pattern deviation.^14,17,18

Multiple studies have investigated the effect of inferior oblique muscle weakening procedures on ocular torsion. As early as 1986, Kushner, in his research evaluating cyclotorsional effects, noted that weakening the inferior oblique or tightening the superior oblique resulted in long-term incyclorotation (clockwise for right eyes and counterclockwise for left eyes) of the axis of astigmatism by approximately 10°.¹⁹ Sharma et al²⁰ compared Fink’s recession with modified Elliot and Nankin’s anteropositioning, both of which resulted in a comparable degree of intorsional shift (+2.5° and +4.7°, respectively), with no statistically significant difference between the two techniques. The mean preoperative extorsion was 9.8° in patients undergoing Fink’s recession and 11.4° in those undergoing modified Elliot and Nankin’s anteropositioning. A study by Farid et al²¹ evaluated the effect of inferior oblique anterior transposition (IOAT) on fundus torsion and detected significant decrease from 12.67±8.13° preoperatively to 3.40±5.06° postoperatively. Sethi et al¹⁷ compared various inferior-oblique weakening procedures achieving mean reduction in excyclotorsion 3.65° in group treated with inferior oblique recession.

The mean preoperative objective cyclotorsion in our study was 13.48°±6.36° in the right eye and 11.50°±6.71° in the left eye, consistent with the expected presence of excyclotorsion in patients with V-pattern strabismus and inferior oblique overaction.^22–24 Notably, the mean disc-foveal angle (DFA) reported by Sethi et al¹⁷ for patients undergoing inferior oblique weakening for primary or secondary inferior oblique overaction was 11.52°±7.15°, a value closely aligning with our findings, further supporting the reproducibility of these measurements in similar patient populations. Similarly, a study by Lee et al¹⁸ investigating objective excyclotorsion following graded inferior oblique recession in patients with primary and secondary inferior oblique overaction (IOOA) reported a mean preoperative torsional angle of 13.25°±6.74° in patients with primary IOOA and 16.91°±7.57° in those with secondary IOOA.

A moderate positive correlation was found between the preoperative amount of V-pattern and absolute objective cyclotorsion (r=0.36, p=0.0093). However, postoperatively, this relationship was no longer observed, as absolute objective cyclotorsion showed a slight negative correlation with the remaining V-pattern (r= −0.09, p=0.0001), showing that V-pattern improvement is largely independent of the degree of torsional correction. A possible explanation for this result is that the surgical correction of the V-pattern strabismus and inferior oblique overaction disrupted the preoperative relationship between the magnitude of the V-pattern and objective cyclotorsion. Postoperatively, as the V-pattern was significantly reduced, the remaining variation in cyclotorsion may have been influenced by other factors, such as individual differences in muscle elasticity, neural adaptation, or residual oblique muscle function. Additionally, the slight negative correlation could suggest a compensatory mechanism, where some patients with minimal residual V-pattern exhibited greater postoperative cyclotorsion adjustments due to neural adaptation or changes in extraocular muscle dynamics. These mechanisms were examined in the study by Schworm et al, which analyzes the underlying factors contributing to the well-documented long-term postoperative subjective cyclotorsional changes.²⁵

Following surgery, our study population showed a significant reduction in objective cyclotorsion (right eye: 5.99°±4.50°; left eye: 8.39°±3.82°), ultimately aligning closely with the levels observed in normal subjects. The average disc-foveal angle, as reported in the literature and confirmed by our previous research, typically ranges between 5° and 7.5°.^7,11,26–29

The average excyclotorsion reduction observed in our study population was 2.52° for every 2 mm of inferior oblique muscle recession. These results are consistent with Harada et al³⁰ estimated a 1° change for every 1 mm of recessed inferior oblique muscle. Lee et al¹⁸ reported Lee et al¹⁸ reported a statistically significant change in cyclorotation, but did not establish a correlation between the degree of recession and the change in cyclorotation, making it impossible to directly relate our results to his findings.

Moreover, we observed a positive correlation between the amount of inferior oblique recession and the change in absolute objective cyclotorsion (r=0.46, p=0.00), indicating that greater recession generally resulted in a more significant reduction in cyclotorsion. A similar observation was made by Sethi et al.¹⁷ A linear relationship was also detected when analyzing each eye separately, with similar correlation coefficients for the right (r=0.37, p=0.0083) and left eye (r=0.37, p=0.0087). Although these correlations were slightly weaker when considering both eyes together, the difference was not statistically significant (Fisher’s z-test 0.72, p=0.47). This suggests that while inferior oblique recession influences cyclotorsion at the individual eye level, the overall binocular effect remains consistent, reinforcing the effectiveness of this procedure in managing torsional misalignment.

Interestingly, we found a positive correlation between preoperative objective cyclotorsion and the change in postoperative objective cyclotorsion in each eye. This suggests that the eye with greater preoperative excyclotorsion undergoes a greater change in objective cyclotorsion following surgery. Our results align with those of Sethi et al¹⁷ who suggested that, at the pooled data level, this correlation might partly stem from the graded approach to inferior oblique weakening. In this approach, the choice of surgical procedure depends on the degree of inferior oblique overaction and the V pattern, with more powerful weakening procedures typically performed in eyes with greater baseline excyclotorsion. Additionally, they propose a possible “self-adjusting” mechanism in inferior oblique weakening procedures, in which the degree of preoperative excyclotorsion influences postoperative changes in excyclotorsion, regardless of the final anatomical position of the inferior oblique – an idea that warrants further examination.

We observed a significant reduction in the mean V-pattern, decreasing from 18.62Δ±9.77Δ to 2.26Δ±5.76Δ(p<0.0001). Sethi et al¹⁷ also reported a significant reduction in V-pattern, from 19.20Δ±6.31Δ to 6.45Δ±4.05Δ. However, these values represent all procedures evaluated in their study (including inferior oblique recession, recession and anteropositioning, anterior transposition, and anterior and nasal transposition), making direct comparison with our results difficult.

The procedure demonstrated a high success rate, with complete resolution of the V-pattern in 46 cases included in our study, accounting for 92% of the study population. The total change of absolute objective cyclotorsion was moderately correlated with the reduction of the V-pattern (r=0.38, p=0.0032). Taken together, these results support the role of graded inferior oblique muscle recession as an effective surgical option for the management of V-pattern strabismus. As stated in the introduction, no study to date has assessed the effect of bilateral inferior oblique graded recession on cyclotorsion asymmetry, particularly in terms of comparing the impact of symmetric and asymmetric surgeries. Postoperatively, we observed a significant reduction in cyclotorsion asymmetry between the eyes. However, our analysis detected that this reduction occurred regardless of whether the surgery was performed symmetrically or asymmetrically. Both surgical approaches demonstrated a comparable impact on cyclotorsion asymmetry, with the RE/LE difference measuring 1.55°±4.15° in the symmetric group and 1.47°±3.30° in the asymmetric group (p=0.938).

A study by Yilmaz et al³¹ examined the effects of unilateral and bilateral inferior oblique myectomy (IOM) on fundus torsion in patients with primary and secondary IOOA. Their findings demonstrated that bilateral IOM significantly reduced both the mean disc-foveal angle (DFA) and DFA asymmetry between the eyes across all patient groups. However, due to the fact that with this procedure, the remaining muscle is released freely into the Tenon’s capsule, the exact location where the muscle will reattach is unpredictable and thus difficult to compare among patients. This is why, direct comparison of the above-mentioned study with our results is limited.

Undoubtedly, our findings suggest that the symmetry of the procedure is not a determining factor in postoperative cyclotorsion alignment. Instead, other factors may play a more significant role in the observed improvements, highlighting the need for further investigation.

Possible limitation of our study is the retrospective design of this study, which may have led to potential bias in establishing causation. Additionally, the follow-up period was limited to 3 months, which may not capture long-term changes in cyclotorsion; however, based on our clinical experience and previous observations, the effect appears to be long-lasting. The relatively small sample size without a formal power analysis may limit the reliability of subgroup findings. An additional limitation of this study is that concurrent horizontal rectus muscle surgery was performed in some patients, which may have acted as a confounding factor and influenced the postoperative changes in ocular alignment or cyclotorsion.

Conclusion

Graded inferior oblique muscle recession is an effective surgical technique for reducing objective cyclotorsion and V-pattern deviation. Our findings demonstrate a significant correlation between the total amount of muscle recession and the overall change in absolute cyclotorsion. However, changes in cyclotorsion of individual eyes were not reliably predicted by the amount of recession in each eye. Additionally, postoperative reduction in interocular cyclotorsional asymmetry occurred regardless of whether the surgery was performed symmetrically or asymmetrically.

Acknowledgments

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Disclosure

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

References

1. Zhu B, Wang X, Fu L, Yan J. Pattern strabismus in a tertiary hospital in Southern China: a retrospective review. Medicina. 2022;58(8):1018. doi:10.3390/medicina58081018

2. Saxena R, Dhiman R. Pattern strabismus. American academy of ophthalmology. Available from: https://www.aao.org/disease-review/pattern-strabismus. Accessed September 13, 2022.

3. Knapp P. Vertically incomitant horizontal strabismus, the so-called A and V syndromes. Trans Am Ophthalmol Soc. 1959;57:666.

4. Phillips PH, Hunter DG. Evaluation of ocular torsion and principles of management. In: Rosenbaum AL, Santiago AP, editors. Clinical Strabismus Management, Principles and Surgical Techniques. Philadelphia: WB Saunders; 1999:52–72.

5. Guyton DL. Ocular torsion: sensorimotor principles. Graefes Arch Clin Exp Ophthalmol. 1988;266(3):241–245. doi:10.1007/BF02181189

6. Jonas RA, Wang YX, Yang H, et al. Optic disc – fovea angle: the Beijing eye study. PLoS One. 2015;10(11):e0141771. doi:10.1371/journal.pone.0141771

7. Vélez Escolà L, Galán Terraza A, Lagrèze WA, et al. Disc-foveal angle and ocular counterrolling as a key in its interpretation. Arch Soc Esp Oftalmol. 2019;94(12):585–590. doi:10.1016/j.oftal.2019.05.019

8. Kanku MS, Sele S, Held U, et al. Cyclotorsion measurement on scanning laser ophthalmoscopy imaging compared with fundus photography in patients with fourth nerve palsy and healthy controls: cySLO-IV study. J Neuroophthalmol. 2012;41(4):e612–e618. doi:10.1097/WNO.0000000000000996

9. Jethani J, Dave P. A technique for standardizing disk foveal angle measurement. J AAPOS. 2015;19(1):77–78. doi:10.1016/j.jaapos.2014.08.015

10. Simiera J, Loba P. Cyclocheck: a new web-based software for the assessment of objective cyclodeviation. J AAPOS. 2017;21(4):305–308. doi:10.1016/j.jaapos.2017.02.009

11. Simiera J, Ordon AJ, Loba P. Objective cyclodeviation measurement in normal subjects by means of Cyclocheck^® application. Eur J Ophthalmol. 2021;31(2):704–708. doi:10.1177/1120672120905312

12. Sokeer SH, Caldeira JA. V-pattern esotropia: a review; and a study of the outcome after bilateral recession of the inferior oblique muscle: a retrospective study of 78 consecutive patients. Binocul Vis Strabismus Q. 2023;18(1):35–48.

13. Caldeira JA. Some clinical characteristics of V-pattern exotropia and surgical outcome after bilateral recession of the inferior oblique muscle: a retrospective study of 22 consecutive patients and a comparison with V-pattern esotropia. Binocul Vis Strabismus Q. 2004;19(3):139–150.

14. Sokeer SH, Ali AL, Arafa ES, Awara AM, Shafik HM. Evaluation of graded recession of inferior oblique muscle for correction of different grades of V-pattern strabismus. BMC Ophthalmol. 2023;23(1):462. doi:10.1186/s12886-023-03210-x

15. Mostafa AM, Kassem RR. Comparative study of unilateral versus bilateral inferior oblique recession/anteriorization in unilateral inferior oblique overaction. Eur J Ophthalmol. 2017;28(3):272–278. doi:10.5301/ejo.5001062

16. Huang YT, Chen JJ-Y, Wu M-Y, et al. The effects of modified graded recession, anteriorization and myectomy of inferior oblique muscles on superior oblique muscle palsy. J Clin Med. 2021;10(19):4433. doi:10.3390/jcm10194433

17. Sethi A, Dhiman R, Mahalingam K, et al. Evaluation of change in objective cyclotorsion after various inferior oblique-weakening procedures. J AAPOS. 2023;27(6):345. doi:10.1016/j.jaapos.2023.08.016

18. Lee D, Kim WJ, Kim MM. Comparison of excyclotorsion following graded inferior oblique recession for primary versus secondary inferior oblique overaction. Int J Ophthalmol. 2020;13(8):1281–1286. doi:10.18240/ijo.2020.08.15

19. Kushner BJ. The effect of oblique muscle surgery on the axis of astigmatism. J Pediatr Ophthalmol Strabismus. 1986;23(6):277–280. doi:10.3928/0191-3913-19861101-05

20. Sharma P, Thanikachalam S, Kedar S, Bhola R. Evaluation of subjective and objective cyclodeviation following oblique muscle weakening procedures. Indian J Ophthalmol. 2008;56(1):39–43. doi:10.4103/0301-4738.37594

21. Farid MF, Sherin Bayoumy A, Seada M. Changes in fundus torsion following anterior transposition surgery of the inferior oblique muscle. BMFJ. 2023;40(surgical issue):55–67.

22. Cho SY, Lee SY, Lee CY. Clinical evaluation of excyclotorsion in patients with primary inferior oblique overaction. J Korean Ophthalmol Soc. 2012;53(9):1324–1329. doi:10.3341/jkos.2012.53.9.1324

23. Na KS, Lee SY, Lee YC. Ocular torsion in unilateral superior oblique palsy. J Korean Ophthalmol Soc. 2007;48(10):1388. doi:10.3341/jkos.2007.48.10.1388

24. Kushner BJ. A”, “V”, and other alphabet pattern strabismus. In: Taylor D, Hoyt CS, editors. Pediatric Ophthalmology and Strabismus. 3rd ed. London: Elsevier Saunders; 2005:922–931.

25. Schworm HD, Eithoff S, Schaumberger M, Boergen KP. Investigations on subjective and objective cyclorotatory changes after inferior oblique muscle recession. Invest Ophthalmol Vis Sci. 1997;38(2):405–412.

26. Lengwiler F, Rappoport D, Jaggi GP, Landau K, Traber GL. Reliability of cyclotorsion measurements using scanning laser ophthalmoscopy imaging in healthy subjects: the CySLO study. Br J Ophthalmol. 2018;102(4):535–538. doi:10.1136/bjophthalmol-2017-310396

27. Williams TD, Wilkinson JM. Position of the fovea centralis with respect to the optic nerve head. Optom Vis Sci. 1992;69(5):369–377. doi:10.1097/00006324-199205000-00006

28. Bixenman WW, von Noorden GK. Apparent foveal displacement in normal subjects and in cyclotropia. Ophthalmology. 1982;89(1):58–62. doi:10.1016/S0161-6420(82)34862-9

29. Miyata M, Yoshikawa M, Ohtsuki H, et al. Age-related change and sex difference over 60s in disc-fovea angle in Japanese population: the Nagahama Study. Acta Ophthalmol. 2018;96(7):840–845. doi:10.1111/aos.13642

30. Harada M, Ito Y. Surgical correction of cyclotropia. Jpn J Ophthalmol. 1960;8:88–96.

31. Yilmaz OF, Oguz H. Evaluation of the effect of unilateral and bilateral inferior oblique myectomy on fundus torsion in primary and secondary inferior oblique overaction. North Clin Istanb. 2023;10(5):657–665. doi:10.14744/nci.2023.74875