Abstract
Purpose :
Panretinal photocoagulation (PRP) is used for proliferative diabetic retinopathy (PDR), but there is a delicate balance between insufficient treatment and laser-induced side effects like visual field constriction and night blindness as caused by excessive treatment. Hence, non-invasive markers of disease activity are needed to monitor treatment outcome. We aimed to determine changes in retinal vessel geometry (tortuosity, length-diameter-ratio (LDR), branching-coefficient (BC), branching angle (BA), deviation from optimal branching coefficient (DOBC) and fractal dimension (FD)) in a prospective, interventional clinical study of patients with PDR before and three months after PRP.
Methods :
Fifty-one eyes from 44 patients with PDR were included. We used wide-field fluorescein angiography (Optomap, Optos PLC., Dunfermline, Scotland, UK) to diagnose PDR at baseline and to assess activity at month 3. At baseline and follow-up, a certified grader measured retinal vessel geometry between 0.5 and 2.0 disc diameters from the optic disc by a semi-automated software (SIVA, Singapore I Vessel Assessment, National University of Singapore, Singapore) according to a standardized protocol.
Results :
At baseline, mean age and duration of diabetes was 53.1 and 21.1 years, respectively, and 68.6% were male. Mean HbA1c and blood pressure were 68.1 mmol/mol and 159/85 mmHg.
Prior to PRP, mean retinal arteriolar and venular parameters were 1.119 and 1.107 (tortuosity), 16.69 and 11.77 (LDR), 1.52 and 1.32 (BC), 80.87 and 81.12 (BA), and -0.52 and -0.29 (DOBC). FD was 1.476.
At follow-up, 15 eyes had progression of PDR as opposed to 36 eyes that did not. Retinal vessel geometry did not differ between the groups at baseline, but patients with progression had higher arterial BA at follow-up (82.08 vs. 77.62, p=0.02). Likewise, between baseline and follow-up patients without progression of PDR changed in venous LDR (11.47 vs. 13.99, p=0.04), BC (1.33 vs. 1.42, p<0.01), and DOBC (-0.28 vs. -0.41, p<0.01). Both groups increased in FD (progression: 1.486 vs. 1.502, p=0.03, non-progression: 1.472 vs. 1.487, p=0.02).
Conclusions :
Successful PRP leads to alterations in particular in the retinal venular vascular structure. If confirmed with longer time of observation, this may serve as a potential biomarker to determine the individualized threshold of optimal treatment.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.