Keratoconus research review – lessons for Aotearoa

March 2, 2026 Drs Zung Mai and Akilesh Gokul

Accelerated CXL versus accelerated contact-lens-assisted CXL treatment for progressive keratoconus – a three-year retrospective comparative follow-up
Lin YJ, et al
J Clin Med. 14(3):507. doi: 10.3390/jcm14030507

 

Review: This three-year retrospective comparative study evaluated the efficacy and safety of accelerated contact-lens-assisted CXL (CACXL) versus standard accelerated epithelium-off CXL in patients with progressive keratoconus (KC). The study included 66 eyes (33 in each group), with the CACXL group comprising patients with corneal thickness under the 400μm threshold, typically ineligible for standard protocols. Both groups underwent crosslinking using 9mW/cm² irradiance over 10 minutes (total energy 5.4J/cm²), with a UV-filter-free soft contact lens applied in the CACXL group to achieve safe intraoperative thickness.

 

Over three years, best-corrected visual acuity (BCVA) improved significantly in both groups, with no statistical difference between them at any time point. Kmax flattened by an average of 2.4D in the standard CXL group and 1.8D in the CACXL group. Progression occurred in 15.2% of standard CXL eyes vs 24.2% in CACXL, though this difference was not statistically significant. No serious complications – such as corneal melt, infection, or endothelial decompensation – were observed.

 

Comment: This paper is highly relevant in New Zealand, since access to CXL often hinges on minimum corneal thickness criteria and CACXL offers a practical extension for treating thinner corneas that would otherwise be excluded. Optometrists referring patients for CXL should understand the referral thresholds (eg. 400μm thinnest point cutoff) and can confidently advocate for CACXL as a safe, long-term option for eligible patients with thin corneas and progressive disease. This is particularly useful when moderately severe, progressive disease is noted in younger Māori or Pasifika patients, where KC tends to be more aggressive.

 

 

Comparison of tear film quantity parameters between keratoconus and normal eyes
Suwan Y, et al
Sci Rep. 13, 23342. doi: 10.1038/s41598-023-50611-w

 

Review: This cross-sectional, comparative study investigated tear film parameters in 60 eyes with KC versus 40 eyes from age-matched healthy controls. Using non-invasive and standard clinical tests, the authors assessed non-invasive tear breakup time (NIBUT), fluorescein TBUT and Schirmer I test values.

 

In the KC group, mean NIBUT was 5.34 ± 1.1 seconds, significantly lower than the control group's 9.02 ± 1.3 seconds (p<0.001). Similar trends were observed with TBUT (3.8 ± 0.9 seconds in KC vs 7.9 ± 1.2 seconds) and Schirmer scores (12.3 ± 2.4mm vs 18.5 ± 2.6mm), indicating that patients with KC have reduced tear-film stability and aqueous production, even in its early stages. Notably, none of the KC patients were contact lens wearers, ruling out lens-induced DED as a confounding factor.

 

These findings suggest an underlying ocular surface dysfunction in KC, potentially related to chronic eye rubbing, inflammatory mediators and structural changes in lid function and corneal curvature.

 

Comment: This study reinforces the need for routine tear-film assessment in KC suspects, especially given that DED can skew Placido-based corneal topography (the most common type of topographer in primary care in Aotearoa) affecting a practitioner’s ability to make a diagnosis and monitor disease progression. Since topography and contact lens fitting rely on tear-film stability, assessing TBUT and treating evaporative DED can improve the accuracy of KC diagnosis, monitoring progression, referral decisions and contact lens tolerance. Given the increasing availability of meibography and NIBUT in the nation’s optometry practices, routine ocular surface evaluation in all suspect KC patients should become standard, particularly in younger males where DED might otherwise be missed.

 

 

Six-month longitudinal analysis of visual, tomographic and densitometric changes after corneal collagen crosslinking in keratoconus
Karatas E, Koksaldi S, Utine CA
Med Hypothesis Discov Innov Optom. 6(3):92–103. doi: 10.51329/mehdioptometry228

 

Review: This prospective study followed 24 eyes from patients aged 18–30 years with progressive KC undergoing epithelium-off accelerated corneal crosslinking (9mW/cm² for 10 minutes). It evaluated longitudinal changes in BCVA, tomographic parameters (Kmax, Kflat, Kmean), pachymetry and corneal densitometry – a marker of postoperative stromal haze.

 

At six months, average BCVA improved by 0.1 logMAR, with corresponding flattening of Kmax by 1.9D, consistent with therapeutic efficacy. Densitometry peaked at one month post-op, particularly in the anterior 120μm zone, and gradually regressed by six months. Importantly, there was a moderate negative correlation between densitometry and visual acuity at one month (r=−0.54, p<0.05), but this correlation disappeared at six months, supporting the temporary and reversible nature of early haze. The authors concluded that the six-month post-op mark is a reliable clinical endpoint for evaluating functional and structural CXL outcomes.

 

Comment: This paper is a highly valuable study for ophthalmologists and optometrists involved in post-CXL follow-up. It finds that haze-related visual fluctuation at early review is common, particularly at one month, when stromal haze peaks. By six months, this should resolve and visual acuity should improve in parallel; however, it does not imply spectacle refraction or contact lens fitting should be delayed until the six-month mark. Visual rehabilitation should be initiated as soon as is practical, ie. contact lens fitting can proceed once epithelial healing permits, especially in functionally impaired patients. However, it is important to counsel patients that outcomes may continue to improve as haze clears and follow-up contact lens adjustment may be needed at three to six months. In the meantime, supportive healing, such as UV protection and lubricants, should be continued and topography at three and six months should be continued as standard of care to monitor visual and structural outcomes.

 

 

Dr Zung Mai is the current cornea and crosslinking junior research fellow at the Department of Ophthalmology, University of Auckland. 

 

Dr Akilesh Gokul is a clinician-scientist who works as a postdoctoral clinical research fellow in the Department of Ophthalmology, University of Auckland and in clinical practice.