Purpose: To investigate the impact of high myopia on choriocapillaris perfusion and choroidal thickness (CT) in diabetic patients without diabetic retinopathy.
Methods: Healthy subjects and patients with diabetes mellitus were recruited from communities in Guangzhou. They were divided into four groups according to the presence of diabetes and high myopia: healthy control (n = 77), diabetes (n = 77), high myopia (n = 77), and diabetes with high myopia (n = 77). Swept-source optical coherence tomography angiography (SS-OCTA) measured choriocapillaris perfusion and CT. Choriocapillaris perfusion was quantified using the choriocapillaris perfusion index (CPI).
Results: A total of 308 subjects (308 eyes) were included in the study. The average CPI was 91.11 ± 0.84, 90.16 ± 1.46, 89.80 ± 1.42, and 89.36 ± 1.19% in the control, diabetes, high myopia, and diabetes with high myopia groups, respectively (P < 0.001); the average CT was 227.55 ± 43.13, 205.70 ± 59.66, 158.38 ± 45.24, and 144.22 ± 45.12 µm, respectively (P < 0.001). After adjusting for age and sex, the average CPI decreased 0.95 ± 0.20% (P < 0.001) in the diabetes group, 1.33 ± 0.20% (P < 0.001) in the high myopia group, and 1.76 ± 0.20% (P < 0.001) in the diabetes with high myopia group relative to the control group; the average CT decreased 23.53 ± 8.12 (P = 0.004), 70.73 ± 9.41 (P < 0.001), and 85.90 ± 8.12 µm (P < 0.001), respectively. Further adjustment for other risk factors yielded a similar result.
Conclusion: Diabetes and high myopia significantly affect CPI and CT, and the presence of both conditions is more damaging to CPI and CT than diabetes or high myopia alone.