Spectral-Domain Optical Coherence Tomography for Determination of Retinal Thickness in Pediatric Patients with Mild-To-Moderate Chronic Kidney Disease: A Cross-Sectional Study.

OBJECTIVE: Children with chronic kidney diseases (CKD) are at risk for neurological diseases at early adulthood. Spectral-domain optical coherence tomography (SD-OCT) of the retina is especially suitable for determination of intraretinal layer thickness. We wonder whether retinal thinning is already present in pediatric patients with mild-to-moderate CKD. PATIENTS AND METHODS: Children (n = 15; 14.9 ± 2.4 years) with mild-to-moderate CKD (median eGFR of 95ml/min/1.73m2; range: 28-187ml/min/1.73m2) due to glomerulopathy, congenital anomalies of kidney and urinary tract (CAKUT), or haemolytic uremic syndrome (HUS) underwent a detailed ophthalmologic examination including high-resolution SD-OCT. Three OCT scans were obtained from the right eyes of all patients. Within each scan, retinal layers were separated and the mean thickness was determined at the foveal, parafoveal, and perifoveal area. The results were compared to those we obtained previously from healthy children. RESULTS: At the parafoveal area, thickness (median, range) of the total retina (ALL), ganglion cell layer (GCL), and inner plexiform layer (IPL) were reduced compared to healthy volunteers (339µm, (288-361µm) vs. 348µm, (320-385µm); 49.8µm (30.5-56.6µm) vs. 53.5µm (49.5-60.5µm) and 41.0µm (29.4-43.7µm) vs. 43.46µm (39.5-46.3µm); each p < 0.05). The intraretinal thickness measurements at the foveal and perifoveal areas revealed no statistically significant differences between patients and controls. CONCLUSION: Distinct changes within the parafoveal area of the total retina, GCL, and IPL are present in children with mild-to-moderate CKD. Prospective studies are required to assess the clinical significance of our findings.

Characteristic quantities of corneal epithelial structures in confocal laser scanning microscopic volume data sets.

PURPOSE: Fully automated quantification of the morphologic features of different epithelial cell layers in healthy human corneas. METHODS: In vivo confocal laser scanning microscopy was performed on the unilateral eyes of 6 healthy volunteers. Stacks of 160 images (400 × 400 µm) with an interslice distance of 0.4 µm were used to generate full thickness volume data sets of the epithelium. Size and shape factors of basal (BC) and intermediate cell (IC) layers were quantified using appropriate image analysis algorithms. Evaluated parameters include mean area, compactness, solidity, major and minor diameter, and maximum boundary distance. RESULTS: Mean area of BC and IC demonstrated a linear increase from 80 to 160 µm². A similar trend was noted with major and minor diameter and maximum boundary distance. Major diameters of BC and IC measured between 13.2 and 17.0 µm, whereas minor diameter of these cells measured between 8.6 and 12.4 µm. The maximum boundary distance of BC and IC ranged from 7.0 to 9.1 µm. Compactness of epithelial cells clustered around 1.45 and 1.5, whereas cell solidity measured between 1.0 and 1.03. CONCLUSION: Several characteristic morphologic quantities can be calculated using this methodology without manual intervention. Our study demonstrated promising results and suggests that this fully automated morphologic quantification can be successfully applied to assess microstructural changes of the epithelium in normal and various corneal disorders.

Corneal responses to eye rubbing with spectral domain optical coherence tomography.

PURPOSE: Surprisingly, a significant reduction (18.4%) in epithelial thickness was found after 15 seconds of eye rubbing measured using Holden-Payor optical pachometer reported in the literature. Hence, we aimed at studying the effects of compressive and shearing pressure associated with eye rubbing on total corneal, epithelial and Bowman's membrane thickness using spectral domain OCT (SD-OCT). METHODS: SD-OCT (Spectralis; Heidelberg Engineering) was used to acquire cross-sectional images of the cornea. Central total-corneal thickness (TCT), epithelial thickness (ET) and Bowman's membrane thickness (BMT) was measured on 20 eyes of 10 subjects with normal corneas without any ocular pathology using in-house developed MATLAB (Mathworks, Inc.) program. Two different measurement methods (distance between inflection points and peak to peak distance) were performed on luminance graph to obtain thickness profile of the corneas. Baseline measurements were compared with the measurements obtained immediately after 30 seconds of circular eye rubbing over the closed eye lid with contra lateral eye at a primary gaze position. RESULTS: We have found that the mean difference in TCT, ET and BMT to be 0.44 ± 6.00 µm, 0.28 ± 1.72 µm, and 0.01 ± 0.77 µm with first method of measurement, respectively, and the mean difference in TCT and ET were -0.26 ± 5.75 µm, and 0.37 ± 1.38 µm with second method of measurement respectively before and after eye rubbing. These differences were statistically insignificant (all p > 0.05) using both measuring methods. CONCLUSION: Thirty seconds of circular pattern rubbing over closed eye lids using index finger produce no significant changes on total corneal, epithelial and Bowman's membrane thickness.

A perfluoropolyether corneal inlay for the correction of refractive error.

This study assessed the long-term biological response of a perfluoropolyether-based polymer developed as a corneal inlay to correct refractive error. The polymer formulation met chemical and physical specifications and was non-cytotoxic when tested using standard in vitro techniques. It was cast into small microporous membranes that were implanted as inlays into corneas of rabbits (n = 5) and unsighted humans (n = 5 + 1 surgical control) which were monitored for up to 23 and 48 months respectively. Overall, the inlays were well tolerated during study period with the corneas remaining clear and holding a normal tear film and with no increased vascularisation or redness recorded. Inlays in three human corneas continued past 48 months without sequelae. Inlays in two human corneas were removed early due to small, focal erosions developing 5 and 24 months post-implantation. Polymer inlays maintained their integrity and corneal position for the study duration although the optical clarity of the inlays reduced slowly with time. Inlays induced corneal curvature changes in human subjects that showed stability with time and the refractive effect was reversed when the inlay was removed. Outcomes showed the potential of a perfluoropolyether inlay as a biologically acceptable corneal implant with which to provide stable correction of refractive error.