Longitudinal Structure/Function Correlation Between Microperimetry and OCT Imaging in Type 2 Macular Telangiectasia (MacTel)

Abstract

Purpose : To evaluate the correlation of the change in EZ loss area as measured by SD-OCT en face images with the visual function changes demonstrated by development of absolute scotoma as measured by MAIA microperimetry from baseline to 2 years in eyes of participants enrolled in a phase 2 trial of ciliary neurotrophic factors (CNTF) for MacTel (NTMT2, Neurotech).

Methods : We analyzed macular SD-OCT volumes and microperimetry sensitivity maps obtained as part of NTMT2. The OCT layer segmentation and generation of en face images of the EZ in SD-OCT volumes were performed using a semiautomatic method. Standard (mesopic) retinal sensitivity in the macula was determined using a MAIA-1 microperimeter and a custom grid pattern. Mixed effects models were used to assess the association between change in structure (EZ loss area) and function (number of test points below a threshold value [≤ 4dB]) from baseline to 2 years.

Results : The NTMT2 study found that the CNTF implant reduced the progressive loss of photoreceptors (as measured by the EZ loss area) compared to untreated eyes. For this analysis, a total of 87 eyes (59 participants) from the NTMT2 study were included. The median age was 62 years (range: 44-79 years) and 59% were female. The mean (±SE) EZ loss area was 6489 (±479) pixels at baseline and 8193 (±581) pixels at year 2. The mean number of test points ≤ 4dB was 1.9 (±0.4) points at baseline and 3.3 (±0.4) points at 2 years. There was modest correlation (r=0.61; p-value<0.001) between the change in EZ loss area versus the change in the number of test points ≤ 4dB. The results from a mixed effects model showed that at 2 years, the change in EZ loss area for eyes that developed at least one absolute scotoma was 2215 (±330) pixels as compared with 1003 (±369) pixels for eyes that did not develop an absolute scotoma. It is estimated that for eyes with at least one absolute scotoma an increase in the EZ loss area of 0.055 mm² at 2 years would be expected. The area under the curve (AUC) for the change in the number of test points ≤ 4dB was 0.70 (95% CI: 0.59–0.81; p-value<0.001).

Conclusions : This analysis provides additional support for a strong structure to function relationship between the EZ loss area and retinal sensitivity in MacTel thus lending support for the use of EZ loss area as an outcome of disease severity as well as progression for trials in patients with MacTel.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.