PURPOSE:To evaluate the effects of orthokeratology lenses (Paragon CRT® 100 [CRT 100] and CRT Dual Axis® [CRT-E], Paragon Vision Sciences, a CooperVision company) on vision and corneal curvature in myopic Chinese children and adults. METHODS:This was a 12-month, multi-centre, bilateral-dispensing, single-arm clinical trial. Subjects were eligible for enrolment if both eyes had -0.50 to -4.00 DS, up to -1.50 DC, and no corneal abnormality. Uncorrected distance visual acuity (UDVA), manifest refraction spherical equivalent (MRSE), and corneal curvature were assessed at baseline and at follow-up visits after lens-wear periods of 1 day, 1 week, 2 weeks, and 1, 3, 6, 9, and 12 months. RESULTS:Four sites in China enrolled 254 subjects aged 8 to 43 years (median: 11 years). Data were collected from both eyes of all subjects. Mean UDVA and MRSE were significantly improved compared to baseline values at all follow-up visits (P < 0.05). Mean UDVA improved by 0.44 ± 0.25 logMAR at Day 1 and 0.68 ± 0.20 logMAR at 1 month compared to baseline (0.65 ± 0.27 logMAR). Mean MRSE improved by 1.66 ± 0.92 D at Day 1 and 2.64 ± 0.69 D at 1 month compared to baseline (-2.66 ± 0.94 D). At 1 month, 94% of eyes had UDVA of ≤0.1 logMAR and - 0.50 D < MRSE < +0.50 D (472/502 eyes, 95%CI: 92-96%). Compared to baseline values, mean corneal curvatures (both steep and flat meridians) were significantly flatter at all follow-up visits (P < 0.001), and mean corneal astigmatism was slightly but significantly lower from the 1-week visit onward (P ≤ 0.007). There were no significant ocular adverse events. CONCLUSIONS:The CRT® orthokeratology lenses are able to temporarily flatten the cornea during overnight wear, temporarily correct myopia, and effectively improve UDVA after lens removal in a large proportion of predominantly paediatric Chinese eyes.
PURPOSE:This study aimed to develop and validate OcuTOP, a novel handheld corneal topography device designed to overcome the limitations of conventional desktop systems. By incorporating software-based misalignment correction, OcuTOP seeks to provide accurate corneal curvature measurements without need for bulky mechanical alignment mechanisms. Validation was performed using a reference surface with known geometry to assess device accuracy and robustness. METHODS:The OcuTOP device (75 g; 85 × 60 × 60 mm) was evaluated using a reference button with a known curvature (43.3 D). Controlled misalignments were introduced in longitudinal (Z: 42.5-43.5 mm), lateral (X: ±2 mm), and vertical (Y: ±2 mm) directions, generating 243 test cases. Images acquired by the device were analysed using neural network algorithms to estimate misalignment parameters, which were subsequently used to correct axial and tangential curvature maps and estimate button diameter, analogous to white-to-white corneal diameter. RESULTS:OcuTOP demonstrated strong agreement with reference curvature values across all misalignment conditions (P for K1 & K2 = 0.365, 0.385 at Z = 42.5 mm; 0.606, 0.907 at Z = 43.0 mm; 0.297, 0.462 at Z = 43.5 mm). Even at maximum displacement (±2 mm in X and Y), central curvature predictions remained within 2% of true values, with mean astigmatism artifacts limited to <0.2 D at the apex of the surface. However, the errors in estimating curvature values increased progressively towards the periphery. Neural network estimation of Z distance achieved a mean error of 0.06 ± 0.05 mm, with no significant influence on the ability of the device to estimate curvature. WTW predictions were also consistent, with a mean value of 11.66 mm, differing by <1.5% from the reference diameter. CONCLUSIONS:OcuTOP's software-based correction reliably compensates for translational and longitudinal misalignments, showing promising results for future studies enabling accurate corneal surface measurements without mechanical stabilisation.
PURPOSE:Routine orthokeratology (Ortho-K) lens replacement often requires short-term treatment disruption, which may lead to an increase in axial elongation. This study aimed toevaluate axial length (AL) alterations during short-term Ortho-K discontinuation for routine lens replacement in long-term paediatric wearers and examined if adjunctive low-dose atropine mitigates this axial elongation. METHODS:This retrospective cohort study included 126 children with myopia undergoing routine Ortho-K lens replacement at approximately 2-year intervals. AL was measured at the time of lens discontinuation and 1 week after Ortho-K wear resumption. Participants were classified into atropine-bridge (AB) or non-bridge (NB) groups based on the use of 0.01% atropine during discontinuation. Changes in AL across replacement cycles were analysed, and generalised estimating equation models were used to identify factors associated with axial elongation while considering repeated measures. RESULTS:The AL increased significantly during the first discontinuation period (mean 0.039 ± 0.078 mm, p < 0.001); AL did not change significantly during the subsequent replacement cycles. At initial interruption, axial elongation magnitude exceeded the average monthly AL growth during active Ortho-K wear and age-matched normative data. Furthermore, AL change did not significantly differ between the AB and NB groups. In multivariable analyses, longer cumulative Ortho-K wearing duration was associated with less axial elongation during short- term Ortho-K discontinuation, whereas age, sex, baseline refractive status, baseline AL, and atropine use were not significant predictors. CONCLUSIONS:Short-term Ortho-K discontinuation for initial lens replacement is associated with a transient increase in axial elongation that diminishes with longer cumulative lens wear. Furthermore, short-term bridging with 0.01% atropine did not provide a clear additional protective effect. Maintaining continuity of effective Ortho-K treatment and minimising unnecessary interruption, specifically during early replacement cycles, is crucial to optimise long-term myopia control.
PURPOSE:To compare the effects of blue light-filtering and non-blue light-filtering senofilcon A daily disposable contact lenses on color discrimination and contrast sensitivity in healthy young adults with myopia. METHODS:This comparative study included 68 eyes of 34 myopic adults with best-corrected visual acuity of 0.0 logMAR. All participants were evaluated while wearing blue light-filtering and non-blue light-filtering senofilcon A daily disposable contact lenses. Color discrimination was assessed binocularly using the Farnsworth-Munsell 100 Hue test, with blue-yellow axis local error score (LES), red-green axis LES, and total error score (TES) recorded. Contrast sensitivity was evaluated monocularly using the Spaeth-Richman Contrast Sensitivity (SPARCS) test, and central, peripheral, and total SPARCS scores were compared between the two lens types. RESULTS:No statistically significant differences were observed between blue light-filtering and non-blue light-filtering contact lenses in blue-yellow axis LES (p = 0.130), red-green axis LES (p = 0.275), or TES (p = 0.090). Contrast sensitivity scores were significantly higher with blue light-filtering lenses than with non-blue light-filtering lenses in the central area (p = 0.009), superotemporal area (p = 0.024), inferotemporal area (p = 0.013), and in the total SPARCS score (p = 0.016). No significant differences were found in the superonasal or inferonasal areas. CONCLUSIONS:Blue light-filtering senofilcon A daily disposable contact lenses were associated with higher contrast sensitivity in central and selected peripheral visual field regions, without a measurable effect on color discrimination.
PURPOSE:Prolonged digital device use can result in digital eye strain which may be exacerbated by uncorrected astigmatism. This study explored how sustained smartphone reading impacts on visual function and symptoms when astigmatism is corrected with disposable soft toric contact lenses. METHODS:30 adult contact lens wearers (mean age 23 ± 4 years, mean astigmatism 1.12 ± 0.35 D) habitually using digital devices for ≥10 h/day were fitted with Delefilcon A daily disposable toric contact lenses for 14-days. High and low contrast near visual acuity (VA) were assessed before and after a prolonged smartphone reading task on day 1 and day 14 of lens wear. The severity of digital eye strain symptoms were reported using a 0-100 visual analogue scale following the reading task. Contact lens dry eye symptoms were assessed using the 8-item Contact Lens Dry Eye Questionnaire (CLDEQ-8). RESULTS:At baseline, the mean high and low contrast near VAs were - 0.08 ± 0.05 and + 0.04 ± 0.08 logMAR, respectively, which did not decline significantly following the prolonged reading task, or after 14 days of lens wear. The average reading speed was not significantly different between day 1 and day 14 of lens wear (251 ± 85 words-per-minute vs 252 ± 80 words-per-minute, p = 0.47). Digital eyestrain symptoms following the reading task (mean of all symptom scores: 13 ± 21) remained stable over the 14-days of lens wear (all p > 0.05), and > 75% of the reported symptoms were ranked as <15/100 in severity. The mean CLDEQ-8 score was 15.2 ± 8.8. CONCLUSION:The correction of astigmatism with disposable toric contact lenses provided stable functional visual performance, with minimal digital eye strain during a prolonged smartphone reading task. However, over half of participants, reported significant dryness/discomfort (CLDEQ-8, ≥12) during 2-weeks of wear, highlighting a disconnect between short-term digital task symptoms and overall daily lens comfort in participants habitually using digital devices for ≥10 h/day.
PURPOSE:To evaluate the effect of Intense pulsed light (IPL) therapy on eyelid microbiota in symptomatic contact lens (CL) wearers. METHODS:This was a prospective, randomised, double masked clinical trial. Participants with Contact Lens Dry Eye Questionnaire (CLDEQ-8) score ≥ 12 were enrolled and received two IPL/sham treatments at three-week intervals. The sham group underwent simulated light exposure using a torch while the IPL device remained inactive. Meibomian gland expression was performed for both groups after each session. Eyelid margin swabs (right eye only) were collected at baseline (day 0), after two treatment sessions (day 42), and at the final visit (day 90). RESULTS:Eighteen CL wearers completed the study (IPL: n = 10; 90% female, aged 35.3 ± 13.2 years; sham: n = 8; 50% female, aged 28.9 ± 6.3 years). The IPL group demonstrated a significant reduction in bacterial load (colony forming units (CFU)/swab) from day 0 to day 42 for total gram-positive cocci (174.0 ± 11.5 to 122.0 ± 8.4; p < 0.001), total gram-positive rods (174.0 ± 8.2 to 126.0 ± 8.2; p < 0.001), coagulase-negative staphylococci (174.0 ± 12.2 to 122.0 ± 10.0; p < 0.001), and Bacillus spp. 172.0 ± 8.2 to 122.0 ± 9.9; p < 0.001). However, by day 90, bacterial count had increased relative to day 42 and was partially rebounded towards baseline numbers. The sham group showed no significant changes in bacterial load at any follow-up time point. CONCLUSION:IPL therapy significantly reduced eyelid bacterial load after two treatment sessions in symptomatic CL wearers. However, this antimicrobial effect diminished by day 90, suggesting that sustained microbiological benefit may require optimized IPL treatment protocols.
PURPOSE:To describe global clinical practice patterns in diagnostic and subtype classification testing for dry eye disease, and explore evolution in practices over a 5-year period, based on responses to an open survey of international eye care practitioners. METHODS:An anonymous online survey seeking to establish opinions and practices regarding clinical tests for the diagnosis and subtype classification of dry eye disease was developed in consultation with dry eye subspecialists, translated into 14 languages, and distributed to eye care practitioners around the world in 2018-2019 and again in 2023-2024. RESULTS:A total of 2044 survey responses from 54 countries were received across the 2018-2019 and 2023-2024 survey periods. The battery of clinical tests most frequently cited as critical for diagnosis of dry eye disease (a median of seven tests) did not significantly differ between the two time points, and included verbal symptoms (69% versus 74%, p = 0.07), fluorescein breakup time (67% versus 68%, p = 0.90), and corneal staining (64% versus 67%, p = 0.51). The use of validated symptomology questionnaires (37 to 42%, p = 0.03) and non-invasive tear film stability (44 to 50%, p = 0.02) increased between 2018-2019 and 2023-2024 (both p < 0.05), although both of these tests were considered 'critical' by less than 50% of respondents at both time points. No single clinical test was used by more than 40% of participants to aid subtype classification, although lipid layer interferometry and meibography both became more commonly used in 2023-2024 than in 2018-2019 (both p < 0.01). CONCLUSIONS:There was almost no agreement in the test battery for dry eye diagnosis and considerable variation and limited agreement in subclassification testing among eye care practitioners at both time points. Greater uptake of streamlined, evidence-based diagnostic algorithms may reduce perceived complexity and support more consistent diagnostic practice, but this remains to be formally tested.
PURPOSE:To investigate the effect of peripheral scleral lens landing zone modifications upon short-term regional variations in corneal oedema. METHODS:Nine healthy participants wore different scleral lens designs ((1) spherical landing zone, (2) toric landing zone, (3) peripheral notches, and (4) peripheral channels) in a randomised order on four separate days for 100 min. Stromal oedema was quantified using high-resolution optical coherence tomography across the central, mid-peripheral, and peripheral cornea with the lens in situ. Eye Surface Profiler (ESP) images were also captured following the application of 10 μL of 2% sodium fluorescein, over a period of 100 min. Central and peripheral fluorescent intensity data were extracted from the ESP images and analysed using customised software to quantify tear exchange. RESULTS:The channel lens design displayed less central oedema compared to the toric design (1.57 ± 0.45% less oedema, p = 0.04). In the corneal periphery, the magnitude of oedema was less for both the toric lens (2.66 ± 0.66% less oedema, p = 0.02) and the channel design (3.39 ± 0.97% less oedema, p = 0.04) in comparison to the spherical lens design. A highly significant correlation was observed between the magnitude of peripheral tear exchange after 90 min of lens wear and the magnitude of peripheral oedema (r = -0.61, p < 0.001). CONCLUSIONS:Scleral lenses with either a toric landing zone or peripheral channels exhibited less peripheral corneal oedema than a spherical landing zone design, due to enhanced peripheral tear exchange.
PURPOSE:To characterize the cellular and molecular composition of the scleral lens (SL) fluid reservoir (FR) in keratoconus and determine whether this compartment reflects disease-specific inflammation. METHODS:This cross-sectional study analyzed post-lens FR samples from habitual SL wearers with keratoconus and from normal eyes undergoing standardized short-term SL wear. Samples were collected after ≥2 h of lens wear. Leukocytes were quantified using an automated hematology analyzer, and 19 cytokines, chemokines, and growth factors were measured using multiplex bead-based immunoassays. Anterior segment optical coherence tomography (AS-OCT) was used to assess FR characteristics. Group differences were evaluated using Kruskal-Wallis testing with Benjamini-Hochberg false discovery rate (FDR) correction; correlations between outcomes were assessed using the Spearman rank test. RESULTS:Thirty-seven participants were included, 21 in the keratoconus group and 16 in the normal group. All immune cell counts within the FR were greater in keratoconus compared to normal (p = 0.02), and keratoconus eyes demonstrated a distinct pro-inflammatory cytokine profile with significantly elevated eotaxin, IL-4, IL-15, MIP-1β, and TNF-α compared to normal eyes. Conversely, IL-7 and IFN-γ were higher in normal eyes. Several additional mediators (e.g., IL-6, IL-8, MCP-1) trended higher in keratoconus but did not remain significant after FDR correction. CONCLUSIONS:The FR beneath a SL represents a biologically active and disease-sensitive microenvironment. Keratoconus eyes exhibited a distinct pro-inflammatory cytokine signature within the FR, suggesting increased cellular infiltration and localized inflammatory signaling. These findings support the concept that the FR can sequester and concentrate disease-related mediators, highlighting its potential as a novel in vivo sampling compartment and a target for therapeutic modulation in SL wear.
PURPOSE:The global increase in overnight orthokeratology (ortho-k) lens use for myopia control among children and adolescents has been accompanied by a concerning rise in Acanthamoeba keratitis (AK), a rare but sight-threatening complication. Modifiable behavioral risk factors in this population remain insufficiently characterized. This study aimed to identify and quantify key modifiable behavioral risk factors for AK among ortho-k lens wearers. METHODS:A case-control study was conducted. Cases were ortho-k lens wearers diagnosed with AK between January 1, 2021, and November 19, 2025. Controls were active ortho-k lens wearers with no history of AK, matched by age and sex at a variable ratio of 1:1 to 1:5, and recruited between April 15, 2025, and December 21, 2025. Data on demographics, lens wear history, and detailed lens care behaviors were collected using a standardized questionnaire. Univariable conditional logistic regression was used to estimate matched odds ratios (ORs) and 95% confidence intervals (CIs) and to identify risk factors. RESULTS:A total of 79 participants were analyzed (median age, 13.0-14.0 years; 68.3% female), including 20 AK cases and 59 matched controls. Inadequate hand hygiene was associated with the highest risk (OR, 26.46; 95% CI, 3.29-212.79; p < 0.001). Adding solution to the lens case without discarding the old solution (topping off) was strongly associated with AK (OR, 17.40; 95% CI, 2.03-149.34; p < 0.001). Lens-related discomfort (OR, 14.52; 95% CI, 1.64-128.12; p = 0.004) and delayed lens case replacement (OR, 13.04; 95% CI, 1.49-114.00; p = 0.005) were also significant. Cleaning lenses with tap water was associated with a 9-fold increased risk (OR, 9.09; 95% CI, 0.97-85.61; p = 0.028). Omitting the rubbing step during lens cleaning and self-handling without parental supervision were observed exclusively in cases (OR undefined). Additional significant factors included eye discomfort during wear, showering while experiencing discomfort, and irregular follow-up visits (all p < 0.05). CONCLUSIONS:Multiple modifiable hygiene and lens care behaviors are strongly associated with AK among pediatric and adolescent ortho-k lens wearers. Prevention strategies should emphasize strict adherence to proper hand hygiene, avoidance of tap water, mandatory rubbing during cleaning procedures, avoidance of topping off the care solution, timely lens case replacement, and prompt professional evaluation for ocular discomfort.
OBJECTIVE:This study aimed to analyse the agreement in the clinical classification of keratoconus using four grading systems based exclusively on anterior corneal surface topographic parameters. MATERIALS AND METHODS:A retrospective, descriptive, analytical, cross-sectional study was conducted to evaluate agreement and differences among the keratometric scale, Amsler-Krumeich (A-K), Alió-Shabayek (A-S), and Keratoconus Severity Score (KSS) classifications. Retrospective, anonymised data were obtained from anterior corneal surface tomography, including keratometry, pachymetry, corneal aberrations, and the location of the thinnest corneal point, measured with a corneal tomographer (Pentacam®, Oculus Optikgeräte GmbH, Wetzlar, Germany). Agreement between each pair of ordinal scales was assessed using weighted Cohen's kappa coefficient with quadratic weights. RESULTS:A total of 455 eyes with keratoconus were analysed. The mean age was 39.3 ± 12.2 years, with no significant sex differences (p > 0.05). Mean keratometry was 46.5 ± 5.9 D and mean pachymetry was 474.8 ± 70.2 μm. Only 111 eyes could be simultaneously classified across all four systems. Pairwise agreement analysis using weighted kappa revealed generally low concordance between classification systems. The highest agreement was observed between the keratometric and Amsler-Krumeich classifications (moderate agreement), whereas comparisons involving aberration-based systems showed weak to slight agreement. When classifications were based solely on each system's differential parameter, a similar pattern was observed, with moderate agreement between keratometric and pachymetry-based classifications and fair agreement in the remaining comparisons. CONCLUSION:Keratoconus classification systems based on anterior corneal surface parameters show significant discrepancies and cannot be used interchangeably. Even when reduced to their primary defining parameters, agreement remains limited, indicating that these systems capture different dimensions of keratoconus severity.
PURPOSE:To compare the efficacy of orthokeratology (OK) and extended depth-of-focus (EDOF) soft contact lenses in controlling myopia progression over a 12-month period. METHODS:Ambispective comparative study including 56 eyes from 28 myopic patients aged 6 to 16 years. Thirty eyes were fitted with EDOF soft contact lenses (prospective cohort), and 26 eyes with OK lenses (retrospective cohort). Axial length (AXL), spherical equivalent (SE), and binocular visual acuity (VA) were assessed at baseline, 6 months, and 12 months. Corneal parameters, including keratometry (K1,K2) and anterior chamber volume (ACV), were also evaluated. RESULTS:AXL increased significantly over time in both groups (p < 0.001), with no significant differences between groups at any follow-up visit (all p > 0.05). Mean axial elongation at 12 months was 0.05 ± 0.09 mm in the EDOF group and 0.11 ± 0.10 mm in the OK group. These values are lower than those reported in untreated myopic children. A small but statistically significant myopic shift in SE was observed in the EDOF group over time (p < 0.001), whereas no significant refractive changes were detected in the OK group. Visual acuity remained stable in both groups throughout follow-up. Significant corneal changes were observed exclusively in the OK group, including reductions in K1 and K2 (p < 0.001) and a decrease in ACV (p < 0.05). Correlation analysis revealed that, in the OK group, baseline AXL and SE were significantly associated with axial elongation (p < 0.05), indicating a baseline-dependent treatment response. CONCLUSION:Both OK and EDOF soft contact lenses were associated with reduced axial elongation over a 12-month period, with no significant differences in efficacy between treatments. OK demonstrated a distinct profile characterized by corneal remodelling and a response influenced by baseline ocular parameters, whereas EDOF lenses showed a structurally neutral and more consistent effect across patients.
PURPOSE:To evaluate which ocular and contact lens (CL)-related dimensions, and their interactions, contribute most to CL discomfort (CLD), and to determine a set of clinical parameters for CLD assessment. METHODS:Cross-sectional study of consecutive CL wearers was performed. Variables were grouped into six dimensions (personal factors, CL characteristics, symptoms, cornea and conjunctiva, tear film, and lid margin and Meibomian glands). Within each dimension composite indices (0-100) were generated with a principal component analysis (mixed data). A structural equation model (SEM) was used to define the latent construct "CLD", followed by unsupervised hierarchical agglomerative clustering. Cluster membership was subsequently predicted using a Least Absolute Shrinkage and Selection Operator (LASSO)-regularized logistic regression model with an 80/20 train-validation split. A simplified model intended for clinical use was developed. RESULTS:One hundred and fifty CL wearers (97 female; 34.4 ± 12.6 years) were included. SEM indicated a multidimensional structure in which the CL and symptom dimensions contributed most to latent CLD. Clustering yielded two distinct phenotypes that differed (p ≤ 0.043) in age, CL type and replacement schedule, daily wearing time, symptom severity, and several ocular surface parameters. A simplified predictor model (daily wearing time, CL replacement, Contact Lens Dry Eye Questionnaire-8, NIBUT, and tarsal hyperemia) predicted membership in the CLD phenotype with 85% accuracy and area under the curve of 0.956 in the validation set. CONCLUSIONS:Modeling CLD as a latent, multidimensional construct integrating subjective and objective measures allows identification of clinically meaningful phenotypes and supports the development of an easy-to-use classifier with excellent discrimination.
PURPOSE:Warming eye masks, provide relief from symptoms of dry eye associated with meibomian gland disease along with other related eye conditions such as blepharitis, hordeolum and meibomian cysts. Certain eye mask designs use head straps to potentially improve mask retention on the face and heat transfer to the eyelids. Straps may increase pressure on the eye, the chance of tissue damage from direct heating, or pose a vision hazard for the user if they move around with the mask in place. This study investigated whether the presence of a strap clinically influences the performance of such eye masks. METHODS:The surface temperature decline of a Blepha EyeBag® eye mask (Théa Pharmaceuticals Limited,UK) placed on the facial area of a composite manikin head was measured with a thermographer following heating in a domestic microwave for 30, 45 and 60 s at a 800mw settings. Thermographic images were analyzed based on scale intensity using ImageJ software, and variations in facial temperature were plotted. RESULTS:Using a strap significantly (F = 40.451, p < 0.001) decreased the temperature of the manikin upper eyelid by on average 1.4 ± 1.9 °C and lower eyelid by 2.5 ± 2.2 °C. The upper and lower eyelids heated to a similar temperature (on average 31.1 ± 5.1 °C vs 31.2 ± 5.4 °C, respectively; F = 0.064, p = 0.805), with temperate systematically increasing with Blepha EyeBag® heating time (F = 74.027, p < 0.001). The temperature dropped with time following heating (F = 56.483, p < 0.001) in a similar manner with and without the strap in place F = 1.949, p = 0.221). CONCLUSION:The temperature transference to the eyelid surfaces was higher without the strap (on average by 1.9 ± 2.2 °C) possibly because the mask could conform to the contours of the face better when it wasn't pulled tight.
Objective To systematically evaluate structural and functional alterations of the subbasal corneal nerve plexus (SBCNP) in adults with migraine using in vivo confocal microscopy (IVCM) and corneal sensitivity testing, and to explore differences according to migraine subtype. Methods PubMed, Embase, Ovid, LILACS, VHL, and MedRxiv were searched through May 24, 2025, for studies assessing IVCM or corneal sensitivity in adults with migraine. Eligible designs included case-control and cross-sectional studies. Outcomes included corneal total branch density (CTBD), nerve fiber density (NFD), nerve fiber length (NFL), nerve branch density (NBD), tortuosity coefficient (TC), and corneal sensitivity. Risk of bias was assessed using tools designed for each study type, and Certainty of evidence was graded using the GRADE framework adapted to observational studies. Due to substantial methodological heterogeneity across studies, including differences in IVCM acquisition protocols, image analysis software, and mathematical definitions of nerve parameters, findings were synthesized narratively. The protocol was registered in PROSPERO (CRD420251105525). Results Eight studies, including 370 participants with migraine, met eligibility criteria. Most studies evaluating chronic migraine populations reported lower CTBD, NFD, and NFL compared with healthy controls, although findings remained heterogeneous across studies. Studies of episodic migraine showed contradictory findings, including preserved nerve parameters or isolated increases in TC. Two studies using different neurophysiological approaches to measure corneal sensitivity suggested altered peripheral and central trigeminal sensory processing in migraine individuals. Conclusion Available evidence suggests that chronic migraine may be associated with structural alterations of the SBCNP, whereas episodic migraine demonstrates more variable findings, including possible increases in nerve tortuosity. Functional studies suggest altered peripheral and central trigeminal sensory processing in migraine.
