Age-related focal thinning of the ganglion cell–inner plexiform layer

Abstract

Purpose : Focal thinning is reported in patients with Alzheimer’s disease and the thinning zone is located in the inner inferior area (Shao et al. ARVO 2017). This study was aimed to determine the detailed thickness alterations and focal thinning pattern of the ganglion cell–inner plexiform layer (GCIPL) in healthy elderly subjects.

Methods : Nineteen eyes of 19 elderly healthy (≥ 60 years, 66.6 ± 6.0, range 60 – 83 yrs) and 34 eyes of 34 young healthy subjects (age ≤ 40 yrs, 31.8 ± 6.1, range 20 – 40 yrs) were recruited. Custom made UHR-OCT (axial resolution ~3 µm) was used to acquire three dimensional volumes of the macula (6 × 6 mm²). Automated segmentation software (Orion, Voxeleron LLC) was used to segment the GCIPL and created the thickness mapping data in a diameter of 6 mm centered on the fovea. To create the average thickness map, the center of fovea was aligned and the thickness in each pixel of the 512 × 128 pixels was averaged in the group, resulting in the average thickness maps. The difference of the thickness maps was calculated by subtracting the thickness of the young group from the elderly group in each pixel. Partition was done using the Early Treatment Diabetic Retinopathy Study (ETDRS) and Hemispheric partition methods.

Results : The topographic thickness alteration of GCIPL was found located in the nasal side in the elderly group. The most profound thinning was in the 1×1 mm² zone located 1.6 mm nasal from the fovea in the aging group (81.8 ± 7.6 µm, Mean ± Standard Deviation) compared to the young group (90.3 ± 4.5 µm, P = 0.0002). This thinning zone is defined as Miami Aging GCIPL Thinning Zone (A-Zone) with a mean thinning of 8.5 µm (Fig. 1), higher than any other sectors using EDTRS and hemispheric partitions between two groups. Statistical analysis of the annuli and sectors showed only the thickness in the inner annulus (1-3 mm in diameter) reached a significant level (post hoc test, P < 0.05) between groups. The thickness in the inner annulus was 80.6 ± 6.7 µm in the elderly group which was thinner than the young group (85.1 ± 5.6 µm, P < 0.05).

Conclusions : Focal thinning of GCIPL located in the nasal side was evident in elderly people and the characteristic thinning pattern may be developed as an image biomarker of age related retinal neurodegeneration.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.