BACKGROUND:To investigate interactions between iris colour and low-concentration atropine on outcomes relevant to clinical myopia management METHODS: A post-hoc, exploratory meta-analysis of three randomised clinical trials investigating atropine 0.01% or 0.05% eye drops vs placebo: the Western Australian Atropine Treatment of Myopia study, the Myopia Treatment Study and the Myopia Outcome Study of Atropine in Children. Iris colour was graded as brown or not brown (including blue/green/hazel). Change in accommodative amplitude, pupil diameter, spherical equivalent refraction (SER) and axial length were assessed using linear mixed models. RESULTS:In participants (baseline ages 5-16 years) using atropine 0.01% (n = 396), pupil diameter change did not differ by iris colour (p ≥ 0.15), while accommodative amplitude decreased more in not brown vs brown iris colour groups at month 12 (adjusted difference = -1.07D, 95% CI: -2.02, -0.12, p = 0.03), but not at month 24 (p = 0.76). Change in pupil and accommodative outcomes with 0.05% atropine (n = 66) did not differ by iris colour (p ≥ 0.10). Among not brown iris colour participants, myopia progression was lower in the atropine 0.01% vs placebo group at 24 months (SER: +0.17D, 95% CI: 0.07, 0.26, p < 0.001; axial length: -0.09 mm, 95% CI: -0.12, -0.05, p < 0.001), but not among brown iris colour participants (SER: -0.08D, 95% CI: -0.20, 0.05; axial length: +0.03 mm, 95% CI: -0.02, 0.07). CONCLUSION:Change in pupil diameter and accommodative amplitude with low-concentration atropine largely did not differ between iris colour groups. Among participants using 0.01% atropine eye drops, there was less 24-month myopia progression compared to placebo in participants with blue/green irides, but not with brown irides.

Importance Additional data are required regarding atropine treatment regimens for control of myopia progression. Objective To investigate the efficacy and safety of different atropine regimens for myopia in children. Design, Setting, and Participants This was a secondary analysis of the 3-year results of the 24-Month Myopia Outcome Study of Atropine in Children (MOSAIC) trial, called the MOSAIC2 trial. The MOSAIC trial was an investigator-led, double-masked, randomized clinical trial of different atropine concentrations and regimens. The MOSAIC2 study took place at the Centre for Eye Research Ireland, in Dublin, Ireland, and included children and adolescents with myopia from the MOSAIC trial. Data analysis was conducted from November 2023 to February 2024. Interventions Participants were randomly assigned to the following cohorts: group 1, nightly placebo for 2 years then 0.05% atropine eye drops for 1 year and group 2, nightly 0.01% atropine eye drops for 2 years then rerandomization to placebo nightly, tapering placebo, or tapering of 0.01% atropine eye drops for 1 year. Main Outcomes and Measures Observed changes in cycloplegic spherical equivalent refraction and axial length from month 24, or baseline, to month 36. Results A total of 199 children with myopia (mean [SD] age, 13.9 [2.4] years; 121 female [60.8%]) of the 250 children and adolescents from the MOSAIC trial were included in the MOSAIC2 trial analysis. Of 83 participants assigned to group 1, 66 (79.5%) reconsented to year 3, and 61 (73.5%) completed the trial. Of 167 participants assigned to group 2, 133 (79.6%) continued to year 3, and 121 (72.5%) completed the trial (0.01% atropine, then nightly placebo: n = 31 and n = 29 [93.5%]; 0.01% atropine, then tapering placebo: n = 29 and n = 25 [86.2%]; 0.01% atropine then tapering 0.01% atropine: n = 73 and n = 67 [91.8%], respectively). Compared with the group taking placebo then 0.05% atropine, the combined atropine then placebo groups had more spherical equivalent progression (adjusted difference, −0.13 diopters [D]; 95% CI, −0.22 to −0.04 D; P = .01) and axial elongation (adjusted difference, 0.06 mm; 95% CI, 0.02-0.09 mm; P = .008), and the group taking 0.01% atropine then tapering 0.01% atropine had more axial elongation (adjusted difference, 0.04 mm; 95% CI, 0.009-0.07 mm; P = .04). In the group taking placebo then 0.05% atropine, 15% (n = 10) and 8% (n = 5) reported blurred near vision and photophobia, respectively, during year 3, compared with 3% (n = 2) and 0%, respectively, in the group taking 0.01% atropine then tapering 0.01% atropine, and no reports in both placebo groups. Conclusions and Relevance Despite more adverse events, participants using 0.05% atropine during year 3 had no differences in treatment completion rates and exhibited 0.13-D less myopia progression and 0.06-mm less axial elongation, compared with participants using placebo, supporting consideration of treatment as given to the group taking 0.05% atropine in this European population. Trial Registration isrctn.org Identifier: ISRCTN36732601

Objectives: To investigate the referral and management patterns of patients with keratoconus among primary eye care practitioners in Ghana and Nigeria. Methods: A questionnaire adapted from previous studies was modified and created using Google Forms. The online survey was distributed to prospective participants using e-mails and other social media platforms. Data were analyzed using the Statistical Product and Service Solutions software (version 25.0; IBM Corp, Armonk, NY; Released 2017). Results: One hundred and sixty-nine optometrists responded to the survey (61.54% from Nigeria and 38.46% from Ghana). Most (88.6%) practiced without corneal topographers. Most respondents (77.7%, n=136) reported not fitting rigid gas-permeable (RGP) contact lenses in a year and 68% were willing to refer for contact lens fitting to another practitioner. The major barriers to RGP fitting were lack of experience (44.4%, n=72), cost to practice (15.4%, n=25), and other reasons (12.4%), whereas 27.8% (n=45) preferred not to answer. Seventy-six percent of respondents (n=133) were willing to fit RGPs if the respondents received the training to do so. About half of the respondents (53.8%) reported progression of cornea signs as the reason for referral to an ophthalmologist. Half of the respondents (n=51.4%) did not have a cornea surgeon in the area the respondents practiced, and 76.3% reported not comanaging patients at all with ophthalmologists. Conclusion: This study highlights the current standard of care of patients with keratoconus in West Africa. The findings from this study suggest that clinical guidelines and further training of eye care practitioners in West Africa are needed to better manage patients with keratoconus.

Importance:Additional data are required regarding atropine treatment regimens for control of myopia progression. Objective:To investigate the efficacy and safety of different atropine regimens for myopia in children. Design, Setting, and Participants:This was a secondary analysis of the 3-year results of the 24-Month Myopia Outcome Study of Atropine in Children (MOSAIC) trial, called the MOSAIC2 trial. The MOSAIC trial was an investigator-led, double-masked, randomized clinical trial of different atropine concentrations and regimens. The MOSAIC2 study took place at the Centre for Eye Research Ireland, in Dublin, Ireland, and included children and adolescents with myopia from the MOSAIC trial. Data analysis was conducted from November 2023 to February 2024. Interventions:Participants were randomly assigned to the following cohorts: group 1, nightly placebo for 2 years then 0.05% atropine eye drops for 1 year and group 2, nightly 0.01% atropine eye drops for 2 years then rerandomization to placebo nightly, tapering placebo, or tapering of 0.01% atropine eye drops for 1 year. Main Outcomes and Measures:Observed changes in cycloplegic spherical equivalent refraction and axial length from month 24, or baseline, to month 36. Results:A total of 199 children with myopia (mean [SD] age, 13.9 [2.4] years; 121 female [60.8%]) of the 250 children and adolescents from the MOSAIC trial were included in the MOSAIC2 trial analysis. Of 83 participants assigned to group 1, 66 (79.5%) reconsented to year 3, and 61 (73.5%) completed the trial. Of 167 participants assigned to group 2, 133 (79.6%) continued to year 3, and 121 (72.5%) completed the trial (0.01% atropine, then nightly placebo: n = 31 and n = 29 [93.5%]; 0.01% atropine, then tapering placebo: n = 29 and n = 25 [86.2%]; 0.01% atropine then tapering 0.01% atropine: n = 73 and n = 67 [91.8%], respectively). Compared with the group taking placebo then 0.05% atropine, the combined atropine then placebo groups had more spherical equivalent progression (adjusted difference, -0.13 diopters [D]; 95% CI, -0.22 to -0.04 D; P = .01) and axial elongation (adjusted difference, 0.06 mm; 95% CI, 0.02-0.09 mm; P = .008), and the group taking 0.01% atropine then tapering 0.01% atropine had more axial elongation (adjusted difference, 0.04 mm; 95% CI, 0.009-0.07 mm; P = .04). In the group taking placebo then 0.05% atropine, 15% (n = 10) and 8% (n = 5) reported blurred near vision and photophobia, respectively, during year 3, compared with 3% (n = 2) and 0%, respectively, in the group taking 0.01% atropine then tapering 0.01% atropine, and no reports in both placebo groups. Conclusions and Relevance:Despite more adverse events, participants using 0.05% atropine during year 3 had no differences in treatment completion rates and exhibited 0.13-D less myopia progression and 0.06-mm less axial elongation, compared with participants using placebo, supporting consideration of treatment as given to the group taking 0.05% atropine in this European population. Trial Registration:isrctn.org Identifier: ISRCTN36732601.

OBJECTIVE:A thin choroid is a recognized risk factor for myopia-associated complications and visual impairment in later life. This study aims to develop a clinical tool to identify individuals whose choroidal thickness varies from that expected for their age, sex and refraction, and who might therefore be at higher or lower risk of future myopic complications. DESIGN:Post-hoc patient-level meta-analysis SUBJECTS: Participants aged 6-30 years from four clinical studies: Myopia Outcome Study of Myopia in Children (MOSAIC), Treatment Optimization of Atropine Study (TOAST), Western Australia Atropine for the Treatment of Myopia study (WAATOM), Kidskin-Young Adult Myopia Study. METHODS:Spherical equivalent refraction (SER) was measured by cycloplegic autorefraction and axial length (AXL) by partial coherence interferometry. Choroidal thickness (ChT) was measured by Swept Source-OCT (Triton Plus, Topcon) or Spectral Domain-OCT (Spectralis, Heidelberg). Multiple linear regression and Machine Learning approaches were applied to create prediction models for ChT as a function of age, sex, SER and AXL. MAIN OUTCOME MEASURES:Deviation of subfoveal ChT from the expected value a function of age, sex, SER and AXL. RESULTS:Ordinary least square (OLS) regression with restricted cubic splines and a linear mixed model with non-linear spline terms for age and AXL both estimated ChT well, explaining over 44% of the variance. Of the remaining variance, approximately 50% was due to inter-individual differences in ChT (likely reflecting genetic, environmental or lifestyle factors), with 44% of participants having a ChT that was >50 µm thicker or thinner than expected. A clinical nomogram was generated from the OLS model to facilitate comparison of the observed ChT with that expected on the basis of SER, AXL and demographic factors. CONCLUSIONS:ChT is a known myopia biomarker that is not fully utilised to inform clinical practice. The resultant clinical ChT nomogram is a simple, visual clinical tool that provides an objective method to gauge and potentially track a myopic child's risk of myopia-related complications, such as myopic maculopathy, based on the mismatch between their measured and expected choroidal thickness.

Aims/Purpose: Assessing axial eye growth is a key component in myopia management; however, access to biometry is limited in primary eye care settings. This study evaluated choroidal thickness, compared to spherical equivalent refraction, as a potential biomarker of axial elongation. Methods: The Myopia Outcome Study of Atropine in Children (MOSAIC) is a double‐blind, randomized controlled trial of 0.01% atropine eye drops. Irish myopic participants aged 6–16 years used either 0.01% atropine or placebo eye drops nightly for 2 years. Spherical equivalent refraction (SER) was measured by cycloplegic autorefraction, axial length (AL) by partial coherence interferometry and choroidal thickness (ChT) by Swept Source‐OCT. The respective 12‐month changes in both eyes were included in mixed linear regression analysis, while controlling for treatment group and within‐subject correlation. ROC analysis was conducted to assess the ability of ChT and/or SER to identify eyes in the top 25% (fast progressors) of AL change. Results: Of the 250 participants enrolled in MOSAIC (mean age 11.8 years, 62% female), 217 (87%) completed the 12‐month visit. Mean 12‐month change in AL, ChT and SER were 0.268 ± 0.19 mm, −3.62 ± 33.3 um and −0.437 ± 0.346 DS respectively. Analysis revealed a significant association between change in ChT and AL (−0.01 ± 0.002 mm per 10 μm; p < 0.001) and change in SER and AL (−0.28 ± 0.02 mm per 1D; p < 0.001). When both SER and ChT were combined in a single model, a 1D myopic change in SER and a 10um decrease in ChT were associated with a 0.27 mm ( p < 0.001) and 0.007 mm increase in AL ( p = 0.002), respectively. ROC analysis revealed that change in ChT was a stronger predictor of fast AL progression (AUC = 0.77) compared to SER change (AUC = 0.72), with the combined model performing better than either variable alone (AUC = 0.80). Conclusions: ChT change was significantly associated with AL change over 12 months and better than SER alone at identifying fast AL progressors, with a combined SER and ChT model achieving the best results.

PURPOSE:To investigate 2-year changes in macular choroidal thickness (ChT) in children receiving 0.01% atropine eyedrops and its relationship with spherical equivalent refraction (SER) progression and axial length (AL) elongation. METHODS:A total of 250 myopic children aged 6-16 years (167%-0.01% atropine, 83-placebo) were enrolled in the MOSAIC (ISRCTN36732601) clinical trial. Participants with complete 2-year ChT (Topcon Triton Swept-Source OCT), SER, and AL data were included in this study. Changes in macular ChT at 2 years and associations with changes in SER and AL elongation were analysed using linear mixed models. RESULTS:A total of 187 children (126%-0.01% atropine, 61-placebo) were included in the analysis. Choroidal thickness over 2 years was stable in the 0.01% atropine compared with placebo group, which exhibited consistent thinning in subfoveal (mean ± SE: 0.49 ± 2.22 μm vs. -9.46 ± 2.69 μm; p = 0.034), parafoveal (1.40 ± 1.73 μm vs. -8.11 ± 2.08 μm; p = 0.002), and perifoveal (0.80 ± 1.25 vs. -6.17 ± 1.69; p = 0.002) macular subfields. Choroidal thickening was observed in participants with slower axial eye growth and myopia progression, regardless of their treatment group. Mediation analysis indicated that atropine 0.01% had a significant effect on ChT, with 68.3% of the effect being direct and 31.7% mediated through axial length changes. For SER, the direct effect on ChT was 80%, with the remaining 20% mediated by SER changes. CONCLUSIONS:Myopic participants treated with 0.01% atropine exhibited stable ChT over 2 years, whereas the placebo group showed consistent thinning. The effect of atropine 0.01% on ChT was only partially explained by axial length and SER changes, indicating a direct effect of atropine treatment on the choroid.

Background/Objectives Axial length, a key measurement in myopia management, is not accessible in many settings. We aimed to develop and assess machine learning models to estimate the axial length of young myopic eyes. Subjects/Methods Linear regression, symbolic regression, gradient boosting and multilayer perceptron models were developed using age, sex, cycloplegic spherical equivalent refraction (SER) and corneal curvature. Training data were from 8135 (28% myopic) children and adolescents from Ireland, Northern Ireland and China. Model performance was tested on an additional 300 myopic individuals using traditional metrics alongside the estimated axial length vs age relationship. Linear regression and receiver operator characteristics (ROC) curves were used for statistical analysis. The contribution of the effective crystalline lens power to error in axial length estimation was calculated to define the latter’s physiological limits. Results Axial length estimation models were applicable across all testing regions ( p ≥ 0.96 for training by testing region interaction). The linear regression model performed best based on agreement metrics (mean absolute error [MAE] = 0.31 mm, coefficient of repeatability = 0.79 mm) and a smooth, monotonic estimated axial length vs age relationship. This model was better at identifying high-risk eyes (axial length >98th centile) than SER alone (area under the curve 0.89 vs 0.79, respectively). Without knowing lens power, the calculated limits of axial length estimation were 0.30 mm for MAE and 0.75 mm for coefficient of repeatability. Conclusions In myopic eyes, we demonstrated superior axial length estimation with a linear regression model utilising age, sex and refractive metrics and showed its clinical utility as a risk stratification tool.

SIGNIFICANCE Contact lenses are an increasingly popular option for correcting pediatric refractive error due to increased awareness of interventions to slow myopia progression. With limited information on the safety profiles of contact lenses in children, it is important to characterize the current understanding and promote this device's safe and effective use. PURPOSE This scoping review evaluates characteristics of the current literature that have examined the safety of contact lenses in pediatric patients. It provides future directions for systematic reviews and identifies any gaps in the current literature or areas for future research. METHODS Literature searches in MEDLINE via PubMed, EMBASE, The Cochrane Library, trial registries, and U.S. Food and Drug Administration clinical trial documentation were performed. Included studies (i.e., experimental and quasi-experimental studies; observational studies including prospective and retrospective cohort, case-control, and analytical cross-sectional studies, and case series of 30 or more participants) reported safety and/or complications of the use of any contact lens for correcting refractive error in children (0 to 18 years). Two independent reviewers first screened the titles and abstracts, and then full-text reports for eligibility. Conflicts in eligibility were resolved by discussions with a third reviewer. Two independent reviewers extracted data, including details about the participants, context, study methods, and key findings relevant to the review question. RESULTS This scoping review included 73 studies from 10 countries using different contact lens modalities, primarily orthokeratology and soft contact lenses, in children (6 to 18 years). The most common adverse event reported by the studies was corneal staining (60% orthokeratology, 45% soft contact lens). CONCLUSIONS The need for uniform reporting standards for adverse events poses challenges for comprehensive data synthesis. However, this scoping review identified a sufficient number of studies for a future systematic review to quantify the risks associated with orthokeratology and soft contact lens use in children.

Eye strain when performing tasks reliant on a digital environment can cause discomfort, affecting productivity and quality of life. Digital eye strain (the preferred terminology) was defined as "the development or exacerbation of recurrent ocular symptoms and/or signs related specifically to digital device screen viewing". Digital eye strain prevalence of up to 97% has been reported, due to no previously agreed definition/diagnostic criteria and limitations of current questionnaires which fail to differentiate such symptoms from those arising from non-digital tasks. Objective signs such as blink rate or critical flicker frequency changes are not 'diagnostic' of digital eye strain nor validated as sensitive. The mechanisms attributed to ocular surface disease exacerbation are mainly reduced blink rate and completeness, partial/uncorrected refractive error and/or underlying binocular vision anomalies, together with the cognitive demand of the task and differences in position, size, brightness and glare compared to an equivalent non-digital task. In general, interventions are not well established; patients experiencing digital eye strain should be provided with a full refractive correction for the appropriate working distances. Improving blinking, optimizing the work environment and encouraging regular breaks may help. Based on current, best evidence, blue-light blocking interventions do not appear to be an effective management strategy. More and larger clinical trials are needed to assess artificial tear effectiveness for relieving digital eye strain, particularly comparing different constituents; a systematic review within the report identified use of secretagogues and warm compress/humidity goggles/ambient humidifiers as promising strategies, along with nutritional supplementation (such as omega-3 fatty acid supplementation and berry extracts).

PURPOSE:Dry eye disease has public health and economic significance. Platelet-rich plasma is rich in anti-inflammatory agents and growth factors, both beneficial for ocular surface repair. This study aimed to conduct a systematic review and meta-analysis to summarize the benefits of platelet-rich plasma for treating dry eye disease and its adverse effects. METHODS:Prospective comparative studies using platelet-rich plasma as monotherapy for dry eye disease were included for efficacy assessment. Before-after studies were included for adverse events assessment. Data sources included PubMed, Google Scholar, Web of Science, and Scopus. A systematic review and meta-analysis protocol was pre-registered on PROSPERO (CRD42022347982). PRISMA guidelines were followed. The National Health Institute (NIH) quality assessment tool for before-after studies, the Cochrane risk of bias tool (RoB2), and the methodological index for non-randomized studies were used to assess the risk of bias. Heterogeneity was assessed using the I2 statistic. RESULTS:19 studies (10 comparative and 9 before-after) were included in the systematic review and meta-analysis. The occurrence rate of adverse effects was 2.6 % (95 % CI: 0.5 - 4.7). The pooled standardized mean difference (SMD) for dry eye symptoms was 0.81 (95 % CI: 0.25 - 1.37; I2 = 82 %; p < 0.00001; Z = 2.84, p = 0.004); tear quality was 0.44 (95 % CI: 0.06 - 0.81; I2 = 67 %; p = 0.003; Z = 2.26, p = 0.02); tear quantity was 0.45 (95 % CI: 0.03 - 0.88; I2 = 74 %; p = 0.0003; Z = 2.10, p = 0.04); and corneal staining 0.72 (95 % CI: 0.14 - 1.30; I2 = 85 %; p < 0.00001; Z = 2.43, p = 0.02). CONCLUSION:The current study shows that platelet-rich plasma is efficacious in managing dry eye disease, significantly reducing dry eye signs and symptoms. Such significant improvements could translate to improved quality of life.

PURPOSE:The Myopia Outcome Study of Atropine in Children (MOSAIC) is an investigator-led, double-masked, randomized controlled trial investigating the efficacy and safety of 0.01% atropine eye drops for managing myopia progression in a predominantly White, European population.METHODS:Children aged 6-16 years with myopia were randomly allocated 2:1 to nightly 0.01% atropine or placebo eye drops in both eyes for 2 years. The primary outcome was cycloplegic spherical equivalent (SE) progression at 24 months. Secondary outcomes included axial length (AL) change, safety and acceptability. Linear mixed models with random intercepts were used for statistical analyses.RESULTS:Of 250 participants enrolled, 204 (81.6%) completed the 24-month visit (136 (81.4%) treatment, 68 (81.9%) placebo). Baseline characteristics, drop-out and adverse event rates were similar between treatment and control groups. At 24 months, SE change was not significantly different between 0.01% atropine and placebo groups (effect = 0.10 D, p = 0.07), but AL growth was lower in the 0.01% atropine group, compared to the placebo group (-0.07 mm, p = 0.007). Significant treatment effects on SE (0.14 D, p = 0.049) and AL (-0.11 mm, p = 0.002) were observed in children of White, but not non-White (SE = 0.05 D, p = 0.89; AL = 0.008 mm, p = 0.93), ethnicity at 24 months. A larger treatment effect was observed in subjects least affected by COVID-19 restrictions (SE difference = 0.37 D, p = 0.005; AL difference = -0.17 mm, p = 0.001).CONCLUSIONS:Atropine 0.01% was safe, well-tolerated and effective in slowing axial elongation in this European population. Treatment efficacy varied by ethnicity and eye colour, and potentially by degree of COVID-19 public health restriction exposure during trial participation.

ABSTRACT SIGNIFICANCE This study addresses the lack of choroidal thickness (ChT) profile information available in European children and provides a baseline for further evaluation of longitudinal changes in ChT profiles in myopic children as a potential biomarker for myopia treatment and identifying children at risk of myopic progression. PURPOSE This study aimed to investigate ChT profiles and associated factors in myopic children. METHODS Baseline data of 250 myopic children aged 6 to 16 years in the Myopia Outcome Study of Atropine in Children clinical trial were analyzed. Choroidal thickness images were obtained using swept-source optical coherence tomography (DRI-OCT Triton Plus; Topcon Corporation, Tokyo, Japan). The macula was divided into nine Early Treatment of Diabetic Retinopathy Study locations with diameters of 1, 3, and 6 mm corresponding to the central fovea, parafoveal, and perifoveal regions. Multiple linear regression models were used to investigate determinants of ChT. RESULTS Choroidal thickness varied across the macular Early Treatment of Diabetic Retinopathy Study locations (P < .001): thickest in the perifoveal superior region (mean ± standard deviation, 249.0 ± 60.8 μm) and thinnest in the perifoveal nasal region (155.1 ± 50.3 μm). On average, ChT was greater in all parafoveal (231.8 ± 57.8 μm) compared with perifoveal (218.1 ± 49.1 μm) regions except superiorly where the ChT was greater in the perifoveal region. Longer axial length and higher myopic spherical equivalent refraction were consistently associated with thinner ChT at all locations in the multiple linear regression models. Asian race was significantly associated with thinner ChT only at parafoveal and perifoveal superior regions after Bonferroni correction (P = .004 and P = .001, respectively). CONCLUSIONS Choroidal thickness was thinnest in the nasal macular region and varied systematically across all macular locations, with axial length and spherical equivalent refraction being the strongest determinants of ChT. Longitudinal evidence will need to evaluate whether any differences in ChT profiles are predictive of myopic progression and to determine the role of ChT measurements in identifying myopic children most in need of myopia control treatment.

BACKGROUND To investigate the short-term effects of cyclopentolate and tropicamide eyedrops on choroidal thickness (ChT) in myopic children using placebo or low-dose atropine eyedrops. METHODS The analysis included 242 myopic individuals (7-19 years) enrolled in two randomised placebo-controlled clinical trials of low-dose atropine eyedrops. Cycloplegia was induced using either one drop of 1% cyclopentolate (n = 161), two drops of 1% cyclopentolate (n = 32) or two drops of 1% tropicamide (n = 49). ChT measurements were taken using swept-source optical coherence tomography before and 30 min after administering the cycloplegic eye drops. A subset of 51 participants underwent test-retest measurements prior to cycloplegia. RESULTS Mean changes in subfoveal ChT after two drops of tropicamide and one and two drops of cyclopentolate were -2.5 μm (p = 0.10), -4.3 μm (p < 0.001) and -9.6 μm (p < 0.001), respectively. Subfoveal ChT changes after one and two drops of cyclopentolate were significantly greater than the test-retest changes (test-retest mean change: -3.1 μm; p < 0.05), while the tropicamide group was not significantly different (p = 0.64). Choroidal thinning post-cyclopentolate was not significantly different between atropine and placebo treatment groups (p > 0.05 for all macular locations). The coefficient of repeatability (CoR) in the tropicamide group (range: 8.2-14.4 μm) was similar to test-retest (range: 7.5-12.2 μm), whereas greater CoR values were observed in the cyclopentolate groups (one drop: range: 10.8-15.3 μm; two drops: range: 12.2-24.6 μm). CONCLUSIONS Cyclopentolate eye drops caused dose-dependent choroidal thinning and increased variation in pre- to post-cycloplegia measurements compared with test-retest variability, whereas tropicamide did not. These findings have practical implications for ChT measurements when cyclopentolate is used, particularly for successive measurements.