Abstract
Purpose :
To examine relationships between DR features and severity in the retinal periphery and central macula.
Methods :
Retrospective opportunistic cross sectional analysis of fundus images acquired during routine clinical assessments of patients with DR in two tertiary care retina centers. Color (Zeiss), wide field FA (Heidelberg Spectralis) and OCTA (Zeiss angioplex or RTVue) were captured on the same visit in both eyes of all patients. Features of DR were graded and a severity score was computed. Areas of capillary non perfusion (CNP) were outlined on FA and a previously designed algorithm was used to calculate an OCT A ischemia index (OII). There was also feature based grading on FA for CNP areas, foveal avascular zone (FAZ) widening and neovascularization. Similar grading was done on OCTA for CNP areas, FAZ size and microvascular abnormalities (MVA). OII was calculated for 3x3mm and 6x6mm superficial plexus (SP),deep plexus(DP) and whole retina scans. OII has a theoretical range of 0-1, with 1 representing complete ischemia. Areas of CNP on the FA were estimated and stratified into two groups (CNP < ≤50% and >50%). We cross-tabulated with chi squared testing and used spearman rank correlation coefficients for specific lesion characteristics at central and peripheral locations. Mann Whitney U test was performed for relationship between ischemia index at the periphery and OII at the center.
Results :
22 eyes of 11 patients were included in the analysis. Significant spearman’s rank order correlations were noted between widening of FAZ on FA and SP and DP on OCT A ( 0.54,p=0.008; 0.50,p= 0.01). Central CNP on FA showed significant relationships with MVA in SP( 0.49,p=0.01), CNP and widening of FAZ in the DP of OCT A (0.49,p=0.01). Neovascularisation elsewhere and disc on FA correlated significantly with CNP in SP of OCTA (p=0.001,0.002). Significant positive relationships were seen with peripheral CNP on FA and widening of FAZ on the SP (0.54,p=0.008), as well as MVA in SP and DP of OCTA (0.63,p=0.001;0.54,p=0.009). The OII in the DP on the 6x6mm OCTA scan was seen to be significantly higher in the group with ≤50% ischemia on FA (p=0.03).
Conclusions :
The presence of CNP and MVA on the OCT A is an indicator of widespread retinal vascular damage and potentially represents a non invasive method of evaluating retinal ischemia.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.