Abstract
Purpose :
Proliferative diabetic retinopathy (PDR) is a cause of visual loss. The characteristics of PDR are not well defined. The early treatment diabetic retinopathy study (ETDRS) reported fluorescein angiography (FA) leakage occurred in both retinal neovascularisation elsewhere (NVE) and intraretinal microvascular abnormality (IRMA). Other definitions of IRMA include absence of fluorescein leakage. The purpose of this study was to evaluate optical coherence tomography angiography (OCTA) to distinguish NVE from IRMA.
Methods :
A cross sectional study of 32 eyes of 26 patients. NVE and IRMA vascular lesions were scanned by Spectralis OCTA. Origin and morphology were evaluated to classify the lesions as NVE or IRMA. A chi squared test was used to compare treated and treatment naïve eyes.
Results :
Mean age was 45 years, 19/26 (73%) patients were male, 7/26(27%) were female. 23 eyes were treatment naïve and 9 eyes received past treatment. 22 eyes were classified as NVE based on breach of the internal limiting membrane (ILM). 16/22 (73%) NVE arose from the ganglion cell layer, and originated from a major arcade vein at the margin of capillary non-perfusion. 4/22 (18%) NVE arose from the inner nuclear layer (INL) and originated from the capillary plexus peripherally away from larger vessels. 2/22(9%) NVE originated from sea fan IRMA at the INL in areas of capillary non-perfusion. 8/32 (25%) eyes were classified as IRMA on OCTA, with no breach of the ILM, ILM outpouching, or vitreous dots. 4 out of 8 eyes defined as IRMA on OCTA showed FA leakage, so were treated as NVE with laser therapy. 2 out of 8 eyes with IRMA had received treatment with intravitreal aflibercept. A chi-squared test showed no difference in the subtype of NVE identified between treated and treatment naïve eyes (p=0.8)
Conclusions :
OCTA enables a more detailed evaluation of the morphology and origin of NVE and IRMA in diabetic retinopathy. Lesions defined as IRMA on OCTA may demonstrate fluorescein leakage and NVE may originate from IRMA. NVE and IRMA may represent a continuum representing severity of diabetic retinopathy, rather than separate clinical entities. Further studies will be required to determine how the morphology of vascular lesions in diabetic retinopathy affects treatment response and prognosis.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.