THE EVALUATION OF RETINAL NERVE FIBER LAYER THICKNESS BY OPTICAL COHERENCE TOMOGRAPHY IN PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY DISEASE

Abstract

Aim: We aimed to assess the changes in retinal nerve fiber layer (RNFL) and optic nerve head (ONH) in patients with chronic obstructive pulmonary disease (COPD).

Patients and Methods: Thirty patients having severe COPD and 29 age and sex-matched healthy subjects were enrolled in the study. After a detailed ophthalmic examination, the ONH and RNFL thickness measurements were taken by an optical coherence tomography (OCT) (Stratus OCT-3). Arterial blood gases (pO₂ and PCO₂) were measured and respiratory functional tests were performed for the staging of COPD patients. The OCT parameters were compared difference between the 2 groups using independent t test, while Pearson correlation analysis was performed to assess the correlations between respiratory functional tests, arterial blood gases and RNFL thickness parameters. A p value less than 0.05 was accepted as statistically significant.

Results: There were no significant differences in optic disc area, cup area and rim area between COPD and healthy subjects (p>0.05). Parameters of mean and superior quadrant RNFL thickness were found to be significantly thicker in COPD subjects (114.52±7.7 µm and 141.07 ±18.2 µm, respectively) compared to the control subjects (107.9±5.4 µm and 131.31±13.6 µm, respectively) (p<0.05). No correlation was found between pO₂ and RNFL thickness (r=-0.22, p=0.33). There was a moderate correlation between pCO₂ and superior quadrant RNFL (r= 0.53 and p=0.017), and a high negative correlation between FEV₁/FVC and superior quadrant RNFL (r=-0.76, p=0.003).

Conclusions: The increase in pCO2 and the decrease in FEV1 / FVC indicate increased hypoxia. Peripapillary RNFL loss associated with RGC death can be masked by hypoxia / ischemia-induced retinal and optic disc edema. Increased mean RNFL thickness in COPD patients was thought to be due to retinal edema associated with increased hypoxia.