Photoreceptors, RPE and choriocapillaris loss in Stargardt disease as measured by OCT angiography and en face OCT.

Abstract

Purpose : To study imaging of the outer retina, RPE and choriocapillaris using OCT angiography and en face OCT in nine molecularly confirmed cases of Stargardt disease.

Methods : This is a cross sectional observational case series of nine cases of Stargardt disease with confirmed ABCA4 mutations. Clinical exam and multimodal imaging was performed including en face OCT, OCT angiography, fundus autofluorescence, infrared imaging, visual fields, and microperimetry. Participants were divided into 2 groups based on the age of onset of symptoms: Group 1 (less than 20 years old), group 2 (20 years old or more). To quantify loss, two experienced masked graders measured the defect area of the IS/OS and RPE layers in 6x6 mm en face OCT scans. Additionally, choriocapillaris perfusion density was quantified by OCT angiography employing the split-spectrum amplitude decorrelation algorithm.

Results : The mean age at presentation was: Group 1 (n=4) 19 years (range 14-25 years), group 2 (n=5) 49 years (range 35-62 years). In both groups, the mean best corrected visual acuity (BCVA) of the better eye was 20/60. In both groups, there was a trend toward better BCVA with later age of onset. The area of defects in the IS/OS, RPE, and choriocapillaris perfusion were greater with younger onset disease in group 1 but did not appear to correlate with age in group 2. In each group, the IS/OS layer defect area was consistently larger than the RPE layer defect area. Larger choriocapillaris perfusion defects corresponded to larger defects in both the IS/OS and RPE layers.

Conclusions : Younger age of onset of Stargardt disease is a potential risk factor for disease severity. Furthermore, loss of choriocapillaris perfusion correlated closely with IS/OS layer and RPE layer defects. IS/OS loss preceded RPE loss in areas of decreased choriocapillaris perfusion despite anatomical proximity. This is, most likely, due to primary photoreceptor involvement in this disease, where the ABCA4 gene is expressed. The RPE and choriocapillaris loss may be secondary to photoreceptor loss.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.