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Konstantinos Balaskas, Ferenc B Sallo, Irene leung, Traci E Clemons, Emily Y Chew, Alan C Bird, Tunde Peto, MacTel Study Group; Progression of Inner Segment/Outer Segment junction breaks in Macular Telangectasia type 2 and association with change in visual acuity over a period of 5 years. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4573.
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Macular Telangiectasia (MacTel) type 2 is now considered a disorder of neuroglial origin with photoreceptor loss being integral to the disease process. Breaks in the Inner Segment/Outer Segment (IS/OS) junction line on Optical Coherence Tomography (OCT) are representative of photoreceptor drop-out in the context of the disease. This project examined the correlation between appearance of an IS/OS break in eyes with MacTel type 2 and change in Best Corrected Visual Acuity (BCVA) over time.
499 participants (970 eyes) enrolled in the MacTel Natural History Study between November 2005 and December 2011 who had at least 1 year of follow-up were included in the present project. Patients underwent annual appraisals with OCT imaging. We recorded on each visit BCVA and the presence of an IS/OS break on OCT and whether this involved the center or not. Mixed effects and repeated measures logistic regression models were used to compute means (continuous) and probabilities (categorical) of progression over time.
Of the eyes with OCT data (N=933), a total of 219 (23%) did not have an IS/OS break present at baseline, 353 (38%) had a non-central break and 361 (39%) had a break that affected the center. By 5 years the probability of progression of an eye from no IS/OS break to a non-central break was 72% while the probability of the break progressing from non-central to central was 51%. The risk of an eye having a 15 or more letter drop (RR: 1.70; 95% CI: 1.08 - 2.68;p=0.02) or a 10 or more letter drop (RR: 1.40; 95% CI: 1.04 - 1.90;p=0.03) in visual acuity from baseline was higher in eyes with an IS/OS break affecting the center compared to eyes without an IS/OS break present at baseline.
Our analysis revealed a high percentage of progression to the appearance of an IS/OS break and to its extension towards the center over a 5-year period suggesting that this alteration is an essential part of the process of structural damage to the photoreceptors in the course of MacTel type 2. There was a steep, linear progression to the development of an IS/OS break. This study demonstrates an association between BCVA loss and progression of IS/OS breaks to the centre of the macula with the relative risk of a meaningful loss in distance BCVA (> 15 letters) being significant in the presence of a central IS/OS break.
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