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First Author: R.Kucumen TURKEY
Co Author(s): C. Utine S. Ziylan F. Ciftci
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To evaluate short term specular microscopic findings after collagen cross linking (CXL) for progressive keratoconus and to describe a common morphological finding of specular microscopy images.
Yeditepe University, Department of Ophthalmology, Istanbul, Turkey
The surgery was performed under topical anaesthesia (4% lidocaine eye drop). The corneal epithelium was completely removed in a central circle of 9 mm diameter by means of a thin blunt metal spatula. Following de-epithelialization, the photosensitizer solution containing riboflavin-5-phosphate 0.1% (G. Streuli & Co. AG) with dextran T500 20% (Roth AG) was applied for 30 minutes. Corneal pachymetry guidance was performed in all patients prior to the operation by a Galilei dual Scheimpflug analyzer to define the area with minimal thickness. Intraoperatively, ultrasonic pachymetry readings (PacScan 300AP, Sonomed Inc., NY) were used to ensure that minimum thickness exceeds 400 ?m. The wavelength was 365 nm at a power of 3 mW/cm2 or 5.4 joule/cm2; distance was approximately 5 cm from corneal apex. During UVA irradiation for 30 minutes, isoosmolar riboflavin 0.1% solution was administered every 3 minutes. Postoperative treatment included topical antibiotic drops (Ofloxacin, 4x1), non-steroid anti-inflammatory drops (Diclofenac, 4x1) and artificial tear drops (Tears Naturale Free®, 8x1). Endothelial cell analysis with specular microscopy (Konan Medical, Inc., Hyogo, Japan) was performed preoperatively and postoperatively when epithelial healing has been completed. The cell density, pleomorphism, polymegathism and central corneal thickness values were recorded.
A total of 8 eyes of 8 patients with progressive keratoconus were included into the study. The mean central corneal thickness was 488.29 ±46.71 ṁ (range: 423 541 ṁ) preoperatively, 492.88 ±49.57 ṁ postoperatively (p=0.87). The postoperative specular microscopy images were obtained at 2.16 ±1.94 weeks (Range: 1-6). The mean cell densities were 2571.67 ±255.72 cells/mm2 preoperatively and 2627.63 ±207.03 cells/mm2 postoperatively (p=0.74). The mean polymegathism value displayed an insignificant increase from preoperatively to postoperatively (27.67 ±2.66 and 40.88 ±19.13, respectively. p = 0.25). The mean pleomorphism value decreased significantly from 49 ±5.80 preoperatively to 39.88 ±6.24 (p=0.01). We noted an increase in reflectivity of the endothelial cytoplasm and an ondulating pattern of endothelial plane simulating an edema of the posterior stroma. The posterior stroma and normally invisible Descemets membrane were hyperreflective partially obscuring some of the details of endothelial cell cytoplasm and borders. In 1 eye, of which an 18 months specular microscopy image could be obtained, the endothelial cell mosaic was found to be completely normal, indicating possibly a full reversal of the above mentioned morphological changes.
In this small case series, we did not note a significant change in endothelial cell counts, although some changes in morphological parameters were seen. More importantly, we noted an increase in endothelial cytoplasmic reflectivity, loss of clarity of the cell borders and an ondulating pattern with posterior stromal edema. This effect seemed to be transient. These findings may reflect endothelial cytoplasmic activity induced by CXL which does not affect cell function and can be recovered during the postoperative months. Alternatively, the hyperreflectivity of the stroma may be shadowing on the specular imaging of the endothelium.