Assessment of Corneal Endothelium (CE) in Patients Undergoing Temporary Myopia Therapy (Ortho-K) with CRT Contact Lenses (CL)

Abstract

Purpose : Orthokeratology is a temporary corneal refractive therapy involving the overnight CL wear. During sleep, eyelid occlusion and CL act as barriers to O₂ flow for corneal metabolism and may induce adverse effects such as Corneal Oxygen Deficiency, causing CE morphological alterations. Specular microscopy (SM) was used to evaluate CE. Purpose: Evaluate Paragon CRT® 100 wearers' CE.

Methods : Clinical Trial at Clínica Schaefer Research Center, Brazil, License 1.766.502 CONEP. Age: 18-27 years. Myopic patients: -0.75 to -6,00D, astigmatism 0 to -1.75D. Patients with diseases that restrict the fitting of CL were excluded. Ortho-K lenses: Paragon CRT® and Paragon CRT® 100, Paflufocon B and D. Nidek Specular Microscope (Gamagori, Japan) to calculate the Endothelial Cell Density (ECD), Cellular Area (CA), Coefficient of Variation (CV), and Percentage of Hexagonal Cells (%H). Reliability Index was calculated by the Cells Analyzer_{USA Patent} (Technicall, Brazil) with sample accuracy: 95% Reliability Degree and 0.05 Relative Error (RE). Sampling included cells from three different endothelial central areas, keeping the same RE<5%. To estimate the time effect on the variables, the multiple linear regression model was adjusted, considering the number of days between CL fitting and the different evaluation times as an explanatory variable. In each case, angular coefficients were calculated for the homogeneity of the studied variables regarding the effect of time on these variables. For null homogeneity hypothesis, the stability hypothesis of the variable over time was calculated. Values of p<0.05 showed statistical significance. Software: IBM SPSS Statistics v.20.0. Armonk, NY.

Results : Follow-up time: 333 to 1,111 days, mean of 333±111 days. ECD and CA homogeneity behavior was not observed after CL fitting in relation to time. Patients 13 and 14 presented a higher decrease in ECD and increase in CA, when compared with other patients (Table 1). CV and HEX homogeneity was observed after CL fitting in relation to time (Table 2).

Conclusions : 34 eyes of 17 patients were compared, and two eyes of two patients presented ECD decrease and CA increase. No difference was observed in CV and HEX.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Table 1 - Estimated Angular Coefficients for the Endothelial Cell Density and Cellular Area

 

Table 2 - Different Types of Conical Section and the Corresponding Values of Various Asphericity Coefficients