Ganglion Cell Layer Analysis in Nonarteritic Anterior Ischemic Optic Neuropathy in Diabetic Patients: From the Acute to Resolving Phases
Purpose: The aim of the present study was to assess tomographic changes in CGC in diabetic patients with non-arteritic anterior ischemic optic neuropathy (NOIA-NA) over a 6-month period and to investigate possible correlations with visual acuity and DM. Materials and methods: This is a prospective observational study, conducted at a diabetes referral centre between January 2017 and January 2020. All patients received a complete ophthalmological examination including measurement of best corrected visual acuity (BCVA), a standard automated visual field, and optical coherence tomography of the papilla (the peripapillary retinal nerve fibre layer RNFLp) and macula (the ganglion cell layer). Patients were monitored at 3 and 6 months. At each follow-up visit, visual acuity measurement, OCT, and CV were performed. CGC measurements in the affected eyes were compared with those of a control group. Correlations between the thinning of the CGC and functional parameters such as MAVC and mean deviation (MD) in the acute and chronic phases were analyzed. Results: We included 80 eyes of 80 diabetic patients with NOIA-NA corresponding to our inclusion criteria. The average age was 60.78 ± 6.88 years with extremes ranging from 40 to 75 years, sex ratio F/H=1.28. The mean CGC thickness was 76.93 ± 2.96 μm and 80.03 ± 1.03 μm in affected and control eyes, respectively (P=0.001). Compared to the normative OCT baseline, 62.5% of affected eyes showed thinning of the CGC thickness. In contrast, 100% of the eyes showed RNFLp thickening. The rate of CGC thinning increased over time, such that by the third month, 100% of the eyes with NOIA-NA in our study were classified as abnormal. The CGC was significantly thinner between the initial visit and 3 months (76.93 ± 2.96 µm vs. 67.12 ± -3.33 µm P<0.001) and significantly thinner between the third month follow-up and 6 months (67.12 ± -3.33 µm vs. 66.56+/-3.4 µm P<0.03). The mean percentage of CGC loss after the acute episode was 12.75% (9.81 µm) at 3 months and 13.47% (10.37 µm) at 6 months. CGC at the initial visit was found to be significantly associated with VA (r=-0.682; p<0.001) and DM (r=0.946; p<0.001). Similarly, mean CGC thickness at 3 months and 6 months follow-up was significantly associated with VA (r=-0.633, p<0.001 at 3 months and r=-0.654, p<0.001 at 6 months) and DM (r=0.877, p<0.001 at 3 months and r=0.811; p<0.001 at 6 months). Conclusion: This study indicates that early lesions of the CGC occur in diabetic patients with NOIA-NA in the acute phase, that these lesions can be accurately measured with OCT, and that the significant correlation between CGC changes and visual field deficits and VA represents an important structure-function relationship and underscores the importance of OCT in the evaluation of the functional and structural course of eyes with NOIA-NA.