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Purpose To define the optical coherence tomography (OCT) corneal changes predisposing to acute corneal hydrops among patients with advanced keratoconus. Design Retrospective cohort study. Participants A total of 191 advanced keratoconic eyes from 191 patients with advanced keratoconus cases were studied. Methods Data collected from patients with advanced keratoconus cases were studied during a minimum period of 24 months of follow-up. High-resolution Fourier-domain corneal OCT (5 μm of axial resolution) and corneal topography were performed every 4 months during the follow-up. Several anatomic features at the keratoconus cone were analyzed with OCT, including epithelial and stromal thicknesses, the aspect of Bowman's layer, the presence of Vogt's striae, and stromal opacities. A comparative analysis between anatomic corneal features in eyes that developed corneal hydrops and those that did not develop this complication during the follow-up was performed. Main Outcome Measures Evaluation of anatomic corneal changes at risk of developing a corneal hydrops on the basis of OCT findings. Results Eleven cases of corneal hydrops (5.8%) occurred in our series during a mean follow-up of 30 months (24–36 months). All of these patients were male and younger (23.7±5.9 years) than patients with no acute keratoconus (32.7±11.3 years). Increased epithelial thickening with stromal thinning at the conus and the presence of anterior hyperreflectives at the Bowman's layer level were significantly associated with corneal hydrops, whereas the presence of corneal scarring was a preventive factor. At the healing stage, a pan-stromal scar occurs, with a significant stromal thickening and cornea flattening. Conclusions Increased epithelial thickening, stromal thinning at the keratoconus cone, anterior hyperreflectives at the Bowman's layer level, and the absence of stromal scarring are associated with a high risk of developing corneal hydrops. These aspects should be taken into account by the clinician in the evaluation of keratoconus eyes and in the planning of corneal keratoplasty.

Objective To study corneal morphologic changes in a large keratoconic population and to establish a structural optical coherence tomography (OCT) classification. Design Cross-sectional, observational study. Participants A total of 218 keratoconic eyes from 218 patients and 34 eyes from 34 normal subjects. Methods A Fourier-domain OCT system with 5-μm axial resolution was used. For each patient, 3 high-resolution scans were made across the keratoconus cone. All scans were analyzed by keratoconus specialists who were not given access to patients' clinical and topographic data, and who established an OCT classification. The reproducibility of the classification and its correlation with clinical and paraclinical characteristics of patients with keratoconus were evaluated. The OCT examinations were performed every 4 months to follow up structural corneal changes. Main Outcome Measures Evaluation of the structural corneal changes occurring in keratoconus cases with various stages of severity based on OCT findings. Results Fourier-domain OCT classification containing 5 distinct keratoconus stages is proposed. Stage 1 demonstrates thinning of apparently normal epithelial and stromal layers at the conus. Stage 2 demonstrates hyperreflective anomalies occurring at the Bowman's layer level with epithelial thickening at the conus. Stage 3 demonstrates posterior displacement of the hyperreflective structures occurring at the Bowman's layer level with increased epithelial thickening and stromal thinning. Stage 4 demonstrates pan-stromal scar. Stage 5 demonstrates hydrops; 5a, acute onset: Descemet's membrane rupture and dilaceration of collagen lamellae with large fluid-filled intrastromal cysts; 5b, healing stage: pan-stromal scarring with a remaining aspect of Descemet's membrane rupture. The reproducibility of the classification was very high between the corneal specialist observers. Clinical and paraclinical characteristics of keratoconus, including visual acuity, corneal epithelium and stromal thickness changes, corneal topography, biomechanical corneal characteristics, and microstructural changes observed on confocal microscopy, were concordant with our OCT grading. Conclusions Optical coherence tomography provides an accurate assessment of structural changes occurring in keratoconus eyes. These changes were correlated with clinical and paraclinical characteristics of patients. The established classification not only allows structural follow-up of patients with keratoconus but also provides insight into the pathogenesis of keratoconus and treatment strategies for future research. Financial Disclosure(s) The author(s) have no proprietary or commercial interest in any materials discussed in this article.

To assess the effects of 360-degree laser retinopexy on human corneal subbasal nerve plexus and to investigate correlations among corneal subbasal nerve plexus density, corneal epithelial thickness, and corneal sensitivity.Prospective, observational, nonrandomized study.A total of 15 eyes of 15 patients who underwent pars plana vitrectomy (PPV) with 360-degree laser retinopexy for retinal detachment (RD) and 15 eyes of 15 patients who underwent PPV for macular hole (MH) without laser treatment.Corneal sensation, corneal epithelial thickness, and corneal subbasal nerve plexus density were assessed before surgery and 6 months after surgery via in vivo confocal microscopy, anterior segment optical coherence tomography (AS-OCT), and Cochet-Bonnet esthesiometry (Luneau Ophthalmologie, Paris, France).Corneal subbasal nerve plexus density, corneal epithelium thickness, and central corneal sensitivity.Compared with baselines values, the mean subbasal nerve density (P0.001), mean corneal epithelium thickness (P = 0.006), and mean corneal sensitivity (P0.001) in the RD group were significantly decreased 6 months after surgery by 74.3%, 4.7%, and 56.6%, respectively. Conversely, in the MH group there were no significant differences in the mean subbasal nerve density (P = 0.34), mean corneal epithelial thickness (P = 0.19), and mean corneal sensitivity (P = 0.42) between preoperative and 6-month postoperative values (0.7%, 0.4%, and 0.8%, respectively). The postoperative decrease in corneal subbasal nerve density after laser retinopexy was associated with a decrease in corneal epithelium thickness (r(2) = 0.42; P = 0.006) and a decrease in corneal sensitivity (r(2) = 0.48; P = 0.004). The postoperative decrease in corneal sensitivity poorly correlated with the decrease in corneal epithelial thickness (r(2) = 0.24; P = 0.045). Postoperative corneal nerve density decreased as total laser energy increased (r(2) = 0.51; P = 0.002).Subbasal corneal nerve plexus density decreases after 360-degree laser retinopexy and is accompanied by epithelium thinning and decreased corneal sensation. Surgeons should eschew heavy confluent retinal laser treatment, and corneal sensitivity should be assessed postoperatively to determine whether significant anesthesia has occurred. In such instances, prophylactic measures may be warranted against the development of neurotrophic ulcers.

To define the optical coherence tomography (OCT) corneal changes predisposing to acute corneal hydrops among patients with advanced keratoconus.Retrospective cohort study.A total of 191 advanced keratoconic eyes from 191 patients with advanced keratoconus cases were studied.Data collected from patients with advanced keratoconus cases were studied during a minimum period of 24 months of follow-up. High-resolution Fourier-domain corneal OCT (5 μm of axial resolution) and corneal topography were performed every 4 months during the follow-up. Several anatomic features at the keratoconus cone were analyzed with OCT, including epithelial and stromal thicknesses, the aspect of Bowman's layer, the presence of Vogt's striae, and stromal opacities. A comparative analysis between anatomic corneal features in eyes that developed corneal hydrops and those that did not develop this complication during the follow-up was performed.Evaluation of anatomic corneal changes at risk of developing a corneal hydrops on the basis of OCT findings.Eleven cases of corneal hydrops (5.8%) occurred in our series during a mean follow-up of 30 months (24-36 months). All of these patients were male and younger (23.7±5.9 years) than patients with no acute keratoconus (32.7±11.3 years). Increased epithelial thickening with stromal thinning at the conus and the presence of anterior hyperreflectives at the Bowman's layer level were significantly associated with corneal hydrops, whereas the presence of corneal scarring was a preventive factor. At the healing stage, a pan-stromal scar occurs, with a significant stromal thickening and cornea flattening.Increased epithelial thickening, stromal thinning at the keratoconus cone, anterior hyperreflectives at the Bowman's layer level, and the absence of stromal scarring are associated with a high risk of developing corneal hydrops. These aspects should be taken into account by the clinician in the evaluation of keratoconus eyes and in the planning of corneal keratoplasty.

To study corneal morphologic changes in a large keratoconic population and to establish a structural optical coherence tomography (OCT) classification.Cross-sectional, observational study.A total of 218 keratoconic eyes from 218 patients and 34 eyes from 34 normal subjects.A Fourier-domain OCT system with 5-μm axial resolution was used. For each patient, 3 high-resolution scans were made across the keratoconus cone. All scans were analyzed by keratoconus specialists who were not given access to patients' clinical and topographic data, and who established an OCT classification. The reproducibility of the classification and its correlation with clinical and paraclinical characteristics of patients with keratoconus were evaluated. The OCT examinations were performed every 4 months to follow up structural corneal changes.Evaluation of the structural corneal changes occurring in keratoconus cases with various stages of severity based on OCT findings.Fourier-domain OCT classification containing 5 distinct keratoconus stages is proposed. Stage 1 demonstrates thinning of apparently normal epithelial and stromal layers at the conus. Stage 2 demonstrates hyperreflective anomalies occurring at the Bowman's layer level with epithelial thickening at the conus. Stage 3 demonstrates posterior displacement of the hyperreflective structures occurring at the Bowman's layer level with increased epithelial thickening and stromal thinning. Stage 4 demonstrates pan-stromal scar. Stage 5 demonstrates hydrops; 5a, acute onset: Descemet's membrane rupture and dilaceration of collagen lamellae with large fluid-filled intrastromal cysts; 5b, healing stage: pan-stromal scarring with a remaining aspect of Descemet's membrane rupture. The reproducibility of the classification was very high between the corneal specialist observers. Clinical and paraclinical characteristics of keratoconus, including visual acuity, corneal epithelium and stromal thickness changes, corneal topography, biomechanical corneal characteristics, and microstructural changes observed on confocal microscopy, were concordant with our OCT grading.Optical coherence tomography provides an accurate assessment of structural changes occurring in keratoconus eyes. These changes were correlated with clinical and paraclinical characteristics of patients. The established classification not only allows structural follow-up of patients with keratoconus but also provides insight into the pathogenesis of keratoconus and treatment strategies for future research.