PURPOSE-To assess corneal microarchitecture and regional epithelial thickness profile in eyes with keratoconus, postoperative corneal ectasia, and normal unoperated eyes using spectraldomain optical coherence tomography (SD OCT). METHODS-Regional corneal epithelial thickness profiles of eyes with keratoconus (KC) and postoperative corneal ectasia (Ectasia)were measured with anterior segment SC OCT (Optovue RTVue-100, Optovue Inc., Fremont, CA) and compared retrospectively to those of normal eyes (Control). Epithelial thickness was assessed at 21 points, 0.5 mm apart, across the central 6-mm of the corneal apex in the horizontal and vertical meridians.RESULTS-One hundred twenty eyes were evaluated, including 49 eyes from 29 patients with KC, 32 eyes from 16 patients with Ectasia, and 39 eyes from 21 control patients. Average epithelial thickness at the corneal apex was 41.18±6.47μm (range 30 to 51 μm) in eyes with KC, 46.5±6.72μm in eyes with ectasia (range 34 to 60 μm), and 50.45±3.92 μm in normal eyes (range 42 to 55 μm). Apical epithelial thickness was significantly thinner in eyes with KC (p <.0001) and ectasia (p=.0007) than it was in controls. Epithelial thickness ranges in all other areas varied widely for KC (SD, range 21 to 101 μm) and ectasia (SD, range 30 to 82 μm) compared to controls (SD, range 43 to 64), p = .0063 CONCLUSION-Central epithelial thickness was, on average, significantly thinner in ectatic corneas compared to controls; however, both central and regional epithelial thickness was highly irregular and variable in corneas with keratoconus and postoperative corneal ectasia. These thickness variations may alter preoperative topographic features and measurements in unpredictable ways, especially steepest K values. Regional epithelial thickness cannot be assumed to be uniform in ectatic corneas and therefore may require direct measurement when considering New treatment modalities are demonstrating significant potential efficacy for ectatic corneal disorders such as keratoconus and postoperative corneal ectasia, including corneal collagen cross linking (CXL), intracorneal ring segments (ICRS), and limited topography-guided laser ablation, with variable success rates. 1-7 While these ectatic diseases comprise a heterogeneous population, the end stage histopathological changes are quite similar. 8 Histopathologic analysis of corneal ectasia have shown thinning of the epithelium, usually overlying the steepest portion of the cornea, breaks in Descemet's membrane, fragmentation of Bowman layer, and scarring. 8,9 The corneal epithelium has a rapid cell turnover and is highly reactive to asymmetries in the shape of the underlying stromal surface. Epithelial layer remodeling may therefore have a significant impact in corneal topographic measurements, corneal warpage patterns, and early detection of corneal ectatic processes. 10,11 CXL and ICRS both require a minimum corneal depth to prevent corneal endothelial damage for CXL or segment extrusion for ICRS. In both procedures, corneal thickness i...

Significant epithelial remodeling occurs after CXL in eyes with keratoconus and corneal ectasia, creating a similar, more regularized thickness profile in all meridians in the early postoperative period. This pattern of remodeling may facilitate interpretation of corneal curvature and thickness changes after CXL and may be related to visual acuity after CXL.