Study of Retinal Nerve Fibre Layer Thickness and Visual Contrast Sensitivity in HIV Positive Individuals.

INTRODUCTION: Measurement of Retinal Nerve Fibre Layer Thickness (RNFLT) by Optical Coherence Tomography (OCT) is a sensitive, non invasive and cheap method of detecting early retinal changes in a variety of diseases. In HIV infection, RNFLT is altered and this may have effect on other visual functions like Contrast Sensitivity (CS) and visual acuity. Such ocular pathology can affect the daily life and profession (especially driving) of HIV infected individuals. However, studies on this topic in HIV infected population are rare from India.

AIM: To study RNFLT, CS and their correlation in a sample of HIV positive Indian population.

MATERIALS AND METHODS: The present cross-sectional study was done in a tertiary care medical college hospital of Eastern India between May 2016 and September 2016. We did this study on HIV positive subjects with no clinically apparent ocular infection or other pathology. In this study, we have measured the RNFLT using the HRA-OCT Spectralis machine. The CS was tested using a smartphone version of the Pellie-Robson chart. CD4 count, visual acuity and colour vision were also tested. The data was analysed using SPSS version 20.0 for any correlation between these parameters. Pearson coefficient was used for continuous data and Spearman rank correlation was used for categorical data. A p-value <0.05 was considered significant.

RESULTS: We had 17 patients, that is 34 eyes. RNFLT loss was found in 21% of the eyes and borderline thinning was found in a further 26%. Predominantly, the temporal quadrant was involved. The mean of log CS was 1.33±0.38. Taking 1.5 as the cut-off value for normalcy, 47% of the eyes tested showed decreased CS. Log CS showed significant correlation with RNFLT of the temporal quadrant only (r=0.37; 95% C.I. 0.041 to 0.631; p=0.02). Temporal RNFLT also showed statistical correlation with the CD4 count. The low CS was also significantly correlated with low visual acuity (r=0.5).

CONCLUSION: In HIV infected persons, subtle ocular changes may occur and this may affect visual functions quite early. Hence, a comprehensive eye check-up should include parameters like CS and OCT.