Effect of axial length on intraocular VEGF levels in eyes with Diabetic Retinopathy

Abstract

Purpose : There has been uncertainty in the possible mechanism behind the myopia-diabetic retinopathy (DR) protective nature relationship. We investigated the effect of axial length (AL) on intraocular vascular endothelial growth factor (VEGF) levels in diabetic patients.

Methods : In our prospective study, we enrolled 48 eyes of as many patients. Further, they were divided into three groups of 16 patients each. Group A comprised of normal subjects without diabetes, group B comprised of diabetic patients without retinopathy and group C comprised of diabetic patients with non proliferative retinopathy. Each group was further subdivided into two subgroups (A1-A2, B1-B2, C1-C2) based on the axial length of the eye i.e, AL<=23.30 mm and AL>23.30 mm. Aqueous was obtained at the time of cataract surgery for most of the patients and in few patients of group C, at the time of anti VEGF injection for clinically significant macular edema. The levels of VEGF were evaluated by commercially available kit using bead-based flow cytometric analysis. The level of VEGF was compared with AL in all the three groups. The study was approved by the institutional ethical board.

Results : The mean VEGF values of three groups in patients with AL<=23.30 mm (A1,B1,C1) were 112.5938 (±30.432) pg/ml, 89.3975 (±16.367) pg/ml, and 125.2550 (± 44.759) pg/ml respectively and on comparing these three subgroups there was no statistically significant relation (P=0.107). The mean VEGF values of three groups in patients with AL>23.30 mm (A2,B2,C2) were 53.9262 (± 17.312) pg/ml, 58.5025 (±17.160) pg/ml, 75.9588 (±32.608) pg/ml respectively. Though there is increase in mean VEGF values in group with diabetes and diabetes with NPDR as compared to non-diabetics but on analysing there was no statistically significant difference between their means (P=0.166).
There is significant difference between mean VEGF values when patients with AL<= 23.30 are compared with those having AL>23.30 mm in all the three groups with t test P values of 0.001 (non- diabetics), P=0.002 (diabetics without NPDR) and P=0.025 (diabetics with NPDR) respectively.

Conclusions : The decrease in aqueous VEGF levels in eyes with long axial length appears to have a protective role against DR in diabetic patients. More studies targeting more subjects and other cytokines as well may be useful to prove this protective behavior.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.