The Relationship of Retinal Vessel Caliber to Diabetic Macular Ischemia

Abstract

 

Purpose

 

Diabetic macular ischemia (DMI) is an important cause of visual loss. However the relationship of DMI to retinal vessel diameter has not been examined. We examined if retinal vessel caliber is related to the presence and severity of DMI to determine if retinal vessel diameter may be a marker of DMI.

 

Methods

 

Clinic based cross-sectional study of patients with type 2 diabetes presenting to a tertiary hospital over 6 months. Presence and severity of DMI was assessed using Early Treatment Diabetic Retinopathy Study (ETDRS) protocols from fundus fluorescein images and classified as none/mild, moderate or severe according to foveal avascular zone (FAZ) size, capillary loss or dilatation, and perifoveal vascular abnormalities.. Custom software was used to quantify the greatest linear dimension and area of the FAZ. Retinal vessel caliber was measured using a validated semi-automated software on fundus fluorescein images.

 

Results

 

Of 53 patients examined, 18 (34%), 18 (34%) and 17 (32%) had none/mild, moderate and severe DMI respectively. Persons with moderate or severe DMI had narrower mean retinal arteriolar caliber than persons with no DMI (140.6 µm 95% Confidence Interval (CI) 134.7, 146.4 vs 150.7 µm, 95% CI 142.5, 158, p=0.04, Table) The association remained after multivariate adjustment for age, gender, previous panretinal photocoagulation and neovascularisation at the disc and elsewhere (adjusted mean retinal arteriolar caliber of 140.7 µm 95% CI 135.5, 146.0 vs 150.4 µm, 95% CI 142.9, 157.8, p=0.04) Increasing severity of DMI was also associated with narrower arterioles, with multivariate adjusted mean arteriolar calibers of 150.6, 142.1 and 139.1 µm in participants with none/mild, moderate and severe DMI respectively. Increased FAZ (greatest dimension and area of ischemia) were also associated with narrower arteriolar caliber; each standard deviation decrease in arteriolar caliber was associated with 0.21 mm (95% CI 0.05, 0.38) increase in diameter and 0.19 mm2 (95% CI 0.04, 0.33) increase in area.(p=0.01 for both, Figure 1) Retinal venular caliber and arteriole to venule ratio (AVR) were not associated with DMI.

 

Conclusions

 

Retinal arteriolar narrowing is associated with macular ischemia in eyes with diabetic retinopathy, suggesting it may be a marker for DMI.

 

 

Table. Retinal vessel calibers by severity of diabetic macular ischemia.

 

 

Keywords: 499 diabetic retinopathy • 436 blood supply