Retinal Thickening and Photoreceptor Loss in HIV Eyes without Retinitis

Abstract

Purpose: To determine the presence of structural changes in HIV retinae (i.e., photoreceptor density and retinal thickness in the macula) compared with age-matched HIV-negative controls.

Methods: Cohort of patients with known HIV under CART (combination Antiretroviral Therapy) treatment were examined with a flood-illuminated retinal AO camera to assess the cone photoreceptor mosaic and spectral-domain optical coherence tomography (SD-OCT) to assess retinal layers and retinal thickness.

Results: Twenty-four eyes of 12 patients (n = 6 HIV-positive and 6 HIV-negative) were imaged with the adaptive optics camera. In each of the regions of interest studied (nasal, temporal, superior, inferior), the HIV group had significantly less mean cone photoreceptor density compared with age-matched controls (difference range, 4,308-6,872 cones/mm2). A different subset of forty eyes of 20 patients (n = 10 HIV-positive and 10 HIV-negative) was included in the retinal thickness measurements and retinal layer segmentation with the SD-OCT. We observed significant thickening in HIV positive eyes in the total retinal thickness at the foveal center, and in each of the three horizontal B-scans (through the macular center, superior, and inferior to the fovea). We also noted that the inner retina (combined thickness from ILM through RNFL to GCL layer) was also significantly thickened in all the different locations scanned compared with HIV-negative controls.

Conclusion: Our present study shows that the cone photoreceptor density is significantly reduced in HIV retinae compared with age-matched controls. HIV retinae also have increased macular retinal thickness that may be caused by inner retinal edema secondary to retinovascular disease in HIV. The interaction of photoreceptors with the aging RPE, as well as possible low-grade ocular inflammation causing diffuse inner retinal edema, may be the key to the progressive vision changes in HIV-positive patients without overt retinitis.

Fig 1. Color fundus photo with boxed areas showing the different locations of the fovea and perifoveal areas that were scanned using the adaptive optics camera with the patient fixating between 0 degrees and 2 degrees of retinal eccentricity from the foveal center along the horizontal and vertical meridians.

Fig 2. Postprocessing of Adaptive Optics Images.

A. HIV-positive, and B. Age-matched control, with scan centered on the fovea (fixation at 0 deg). Selected region of interest (ROI) (small yellow box). ROI magnified with corresponding color map of the cone density. Photoreceptor density counts shown.

Fig 3. Analysis of three B-scans within the raster scan set.

The first was centered on the fovea (F), the second was 10 scans superior to the fovea (S), and the third was 10 scans inferior to the fovea (I). For each scan, thickness was measured at the center and over a length of 1,000 microns equally split over the center (red lines).

Fig 4. SD-OCT scans of A. HIV-positive, and B. HIV-negative control, showing total retinal thickness measurements.

Top red line corresponds to the internal limiting membrane (ILM) and bottom red line corresponds to the Bruch’s membrane (BM).