Effects of Continuous Positive Airway Pressure Treatment for Obstructive Sleep Apnea-Hypopnea Syndrome on Corneal Morphological Characteristics.

PURPOSE To evaluate the effects of continuous positive airway pressure (CPAP) therapy on corneal endothelial morphometry and pachymetry in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS). METHODS This prospective, observational study included patients with OSAHS who were evaluated right before and after the commencement of CPAP treatment. Each patient underwent a detailed ophthalmologic examination and assessment of their corneal endothelium with a noncontact specular microscope (Tomey EM-3000; Tomey Corp). Endothelial cell density, coefficient of variation of cell area (CV), hexagonal cell appearance ratio (%Hex), and central corneal thickness were measured. The post-CPAP results were compared with the results of a control group. The differences in the corneal parameters between pre- and post-CPAP therapy of the OSAHS group were correlated with the pretreatment polysomnography results. RESULTS Twenty-seven distinct eyes of 27 patients recently diagnosed with OSAHS and 30 eyes of 30 healthy individuals were used for the statistical analysis. The mean age of patients with OSAHS was 54.2 ± 11.8 years, and after 9.6 months (range 3-18 mo) of good adherence to CPAP treatment, their CV values, indicating polymegathism, decreased from 41.7 ± 8.7 to 38.3 ± 5.8 (P = 0.04), whereas %Hex, indicating pleomorphism, increased from 45.8% ± 8.2% to 48.4% ± 6.6% (P = 0.008). Their post-CPAP corneal parameters did not differ significantly from those of the control group (P > 0.05). A significant positive correlation was observed between the decrease in CV and the duration of the treatment (Rs = 0.566, P = 0.002), as well as the pre-CPAP nonrapid eye movement (NREM) sleep percentage (Rs = 0.459, P = 0.02). A negative correlation was noted between the decrease in CV and the percentage of rapid eye movement (REM) sleep (Rs = -0.459, P = 0.02). CONCLUSIONS Better oxygenation during sleep, resulting from increased CPAP adherence, had a significant influence on corneal endothelium, providing an improvement in corneal polymegathism and pleomorphism, with a potential return of CV and %Hex to their normal values. Greater improvement in polymegathism was observed in patients with greater proportion of NREM sleep.