Clinical context

Visual acuity alone is insufficient when judging corneal disease or surgery. Topography and tomography, surface regularity, biomechanics, endothelial cell density, quality of vision and stability all matter. After refractive procedures, epithelial healing, dry eye, haze, ectasia and the need for enhancement should be assessed separately.

What was studied

In keratoconus, customized TransPRK can reduce irregularity while cross-linking aims to stabilize the cornea. The procedures may be combined or staged. This prospective observational study included 119 eyes: 91 received combined TransPRK and accelerated CXL, while 28 underwent TransPRK a median 36 months after CXL. One surgeon used the same SCHWIND Amaris platform. Mitomycin was omitted in combined cases but applied at 0.02% for 20 seconds sequentially. Propensity matching on six variables produced 27 eyes per group.

How the evidence was produced

A cohort study describes how outcomes are associated with an exposure or treatment in an observed clinical population. This design is useful for routine practice, uncommon events and longer follow-up, but it remains vulnerable to confounding by indication, baseline risk differences and missing data. An association should not automatically be interpreted as a causal effect.

Key result At 12 months, both matched groups gained two corrected-distance lines on average, without a significant between-group difference. Kmax fell from 51.94±4.96 to 48.91±3.86 D in combined eyes and from 49.37±2.90 to 47.49±3.47 D sequentially, P=.001 within both groups; flattening was comparable. Total corneal coma improved by about 0.50 D in both groups, P<.001, without a between-group difference. OCT reflectivity rose and then declined. Combined treatment had an earlier anterior increase, while sequential treatment had higher subepithelial reflectivity at six months. By 12 months the profiles converged, with no clinically meaningful late-haze difference.

How to interpret the result

Under these protocols, both strategies produced similar one-year visual, tomographic and aberrometric outcomes. This does not establish interchangeability: matching balances measured variables only, while mitomycin use and procedure selection remained systematically different. Combined treatment reduces the number of procedures; staging permits assessment of stability after CXL. Choice should consider progression, thickness and shape, ablation depth, age, visual goals and the local safety protocol.

Clinical applicability

The study may refine technique selection and informed discussion, but its conclusions depend on baseline corneal shape, stromal thickness, equipment, nomogram and surgeon experience. Applicability requires comparison of these factors and attention to variability, uncommon complications and follow-up duration rather than mean values alone.

Limitations

The study was nonrandomized, single-surgeon and included only 54 matched eyes. Initial groups were unequal, and treatment selection may reflect clinical risk. Mitomycin was used only sequentially, so timing cannot be separated from haze prophylaxis. Convergence at 12 months does not exclude earlier or later differences, and rare complications cannot be assessed. Verify keratoconus and stability criteria, ablation depth, CXL protocol, attrition, fellow-eye handling, the OCT/ML algorithm, post-match balance, refraction, adverse events, funding and conflicts.

What to verify in the source

Use the DOI below to verify complete methods, result tables, funding and conflicts of interest.