Ocular surface symptoms and tear-film parameters in keratoconus: a systematic review and meta-analysis
- 1Department of Ophthalmology, The First Hospital of Hunan University of Chinese Medicine , ,
- 2First Clinical College of Traditional Chinese Medicine, Hunan University of Chinese Medicine , ,
Abstract
Background
Ocular-surface abnormalities are increasingly recognized in keratoconus (KC), but the magnitude and consistency of these changes remain uncertain. We evaluated ocular-surface symptoms, tear-function parameters, and dry-eye-related categorical outcomes in patients with KC compared with non-KC controls.Methods
PubMed, Embase, Web of Science, and the Cochrane Library were searched from inception through September 1, 2026. Comparative studies reporting the Ocular Surface Disease Index (OSDI), fluorescein tear break-up time (TBUT), noninvasive TBUT (NITBUT), the Schirmer I test (SIT), or a defined dry eye disease (DED) classification were eligible. Meibomian gland dysfunction (MGD) and meibomian gland atrophy (MGA), when reported by otherwise eligible studies, were summarized as secondary ocular-surface findings. Two reviewers independently screened studies, extracted data, and assessed methodological quality using an adapted Newcastle-Ottawa Scale (NOS). Continuous outcomes were quantitatively pooled when the analysis unit and measurement methods were sufficiently defined and comparable; otherwise, study-level findings were summarized without calculating a pooled estimate. Random-effects models were estimated by restricted maximum likelihood with Hartung-Knapp adjustment.Results
Seven studies involving 359 participants with KC and 333 controls were included. OSDI scores were significantly higher in KC (MD, 19.45 points; 95% CI, 12.27 to 26.63; I² = 79.9%). Fluorescein TBUT was shorter, although the pooled difference was not statistically significant (MD, -2.74 s; 95% CI, -7.81 to 2.32; I² = 93.8%). All three studies reporting NITBUT found lower values in KC, but eye selection or data aggregation was unclear in two studies; therefore, a pooled NITBUT estimate was not calculated. SIT findings varied across studies, and a pooled estimate was not calculated because statistical independence of eye-level data and sufficiently comparable testing procedures could not be established across an adequate number of studies. The OSDI finding remained robust across sensitivity and leave-one-out analyses.Conclusions
Patients with KC had higher OSDI scores. The pooled difference in fluorescein TBUT was not statistically significant. Lower NITBUT and SIT values were reported in several studies, but pooled estimates for these outcomes were not calculated because of limitations in eye-level data handling and measurement comparability. Larger prospective multicenter studies using clearly defined analysis units and standardized tear-testing protocols are needed.Systematic review registration
https://www.crd.york.ac.uk/PROSPERO/, identifier CRD420261282391.
Related
- Efficacy of umbilical cord serum in ocular surface diseases: a systematic review
- Changes in Visual Acuity and Dry Eye Parameters Following One Month of Scleral Lens Wear in Patients with Keratoconus: A Prospective Observational Study from Saudi Arabia.
- Beyond Ocular Symptoms: Chronic Progressive External Ophthalmoplegia With Coexisting Facial Palsy and T-wave Inversion
- Systematic review finds keratoconus AI unproven in fellow eyes with normal topography and tomography
- Clinical outcomes of scleral lenses in keratoconus: a systematic review and Meta-analysis
BibTeX
@article{cao2026ocular,
title = {{Ocular surface symptoms and tear-film parameters in keratoconus: a systematic review and meta-analysis}},
author = {Yang Cao and Yue Yang and Wei Deng and Nan Yang},
journal = {Frontiers in medicine},
year = {2026},
month = oct,
doi = {10.3389/fmed.2026.1797492},
url = {https://europepmc.org/article/PMC/PMC13716560},
note = {CC BY},
}
RIS
TY - JOUR
TI - Ocular surface symptoms and tear-film parameters in keratoconus: a systematic review and meta-analysis
AU - Yang Cao
AU - Yue Yang
AU - Wei Deng
AU - Nan Yang
PY - 2026
DA - 2026/10/15
JO - Frontiers in medicine
DO - 10.3389/fmed.2026.1797492
UR - https://europepmc.org/article/PMC/PMC13716560
AB - Background Ocular-surface abnormalities are increasingly recognized in keratoconus (KC), but the magnitude and consistency of these changes remain uncertain. We evaluated ocular-surface symptoms, tear-function parameters, and dry-eye-related categorical outcomes in patients with KC compared with non-KC controls.Methods PubMed, Embase, Web of Science, and the Cochrane Library were searched from inception through September 1, 2026. Comparative studies reporting the Ocular Surface Disease Index (OSDI), fluorescein tear break-up time (TBUT), noninvasive TBUT (NITBUT), the Schirmer I test (SIT), or a defined dry eye disease (DED) classification were eligible. Meibomian gland dysfunction (MGD) and meibomian gland atrophy (MGA), when reported by otherwise eligible studies, were summarized as secondary ocular-surface findings. Two reviewers independently screened studies, extracted data, and assessed methodological quality using an adapted Newcastle-Ottawa Scale (NOS). Continuous outcomes were quantitatively pooled when the analysis unit and measurement methods were sufficiently defined and comparable; otherwise, study-level findings were summarized without calculating a pooled estimate. Random-effects models were estimated by restricted maximum likelihood with Hartung-Knapp adjustment.Results Seven studies involving 359 participants with KC and 333 controls were included. OSDI scores were significantly higher in KC (MD, 19.45 points; 95% CI, 12.27 to 26.63; I² = 79.9%). Fluorescein TBUT was shorter, although the pooled difference was not statistically significant (MD, -2.74 s; 95% CI, -7.81 to 2.32; I² = 93.8%). All three studies reporting NITBUT found lower values in KC, but eye selection or data aggregation was unclear in two studies; therefore, a pooled NITBUT estimate was not calculated. SIT findings varied across studies, and a pooled estimate was not calculated because statistical independence of eye-level data and sufficiently comparable testing procedures could not be established across an adequate number of studies. The OSDI finding remained robust across sensitivity and leave-one-out analyses.Conclusions Patients with KC had higher OSDI scores. The pooled difference in fluorescein TBUT was not statistically significant. Lower NITBUT and SIT values were reported in several studies, but pooled estimates for these outcomes were not calculated because of limitations in eye-level data handling and measurement comparability. Larger prospective multicenter studies using clearly defined analysis units and standardized tear-testing protocols are needed.Systematic review registration https://www.crd.york.ac.uk/PROSPERO/, identifier CRD420261282391.
SN - 2296-858X
ER -