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Tjebo FC Heeren, Diána Kitka, Daniela Florea, Alan C Bird, Emily Chew, Traci E Clemons, Daniel Pauleikhoff, Frank G Holz, Tunde Peto; Progression of Ellipsoid Zone Loss correlates with Change of Scotoma Size in Macular Telangiectasia Type 2.. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1280.
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© ARVO (1962-2015); The Authors (2016-present)
Macular telangiectasia type 2 (MacTel) is a potential bilateral neurodegenerative disease with ellipsoid zone (EZ) loss detected on spectral domain optical coherence tomography (SD-OCT) as a common feature. While best corrected visual acuity (BCVA) often remains stable until late disease stages, visual function loss is typically characterized by the development of a paracentral (nasal) scotoma that enlarges over time as measured by microperimetry. It has been shown that EZ loss correlates with aggregate sensitivity loss, a measure for scotoma depth. Seeking further evidence that EZ loss correlates with functional loss is important, as EZ loss is a potential outcome parameter for interventional clinical trials. Therefore we compared EZ loss with change in scotoma size over time.
Participants of the MacTel Natural History Observation Study (NHOS) underwent annual exams including BCVA, microperimetry (MP1, Nidek), and high density SD-OCT volume scans (Spectralis, Heidelberg Engineering). Scotoma size was derived from counting the number of stimuli above a threshold of 12dB as well as the number of stimuli with absolute scotoma (‘thresholding’). EZ loss was measured using en face SD-OCT scans (Heidelberg Eye Explorer, Heidelberg Engineering) and compared with change of scotoma size and loss of BCVA. Analysis was performed with mixed effects models, accounting for correlation between eyes.
Thirtyone participants (56 eyes) from one center were followed for 4.5±1.2 years (range 2.3-7.6 years). EZ loss was 18600±3917.3 pixel at baseline (≈0.59mm2) and increased 2627.8±427.9 pixel (≈0.08mm2) per year. BCVA decreased 2.2 ± 0.9 letters per year. EZ loss correlated significantly with progression of relative and absolute scotomas (r = 0.62; p-value < 0.0001 and : r = 0.72; p-value < 0.0001, respectively). Microperimetry showed a less discernible progression than EZ loss and a higher rate of ‘regression’, indicating higher variability of the measurement. No correlation was found between EZ loss and loss of BCVA.
Progression of EZ loss correlates well with progression of scotoma size corroborating EZ loss as clinical surrogate outcome parameter for visual function. Moreover, EZ loss, as an objective parameter compared with functional parameters such as microperimetry or BCVA, may be more suitable as primary end point in future interventional clinical trials.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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