Macular Telangiectasia Type 2: Visual Acuity, Disease End Stage, and the MacTel Area: MacTel Project Report Number 8

Abstract

Purpose: To report the visual acuity measures from the macular telangiectasia type 2 (MacTel) registry and to investigate and describe phenotypic findings in eyes with substantial vision loss resulting from MacTel.

Design: Cross-sectional multicenter study.

Participants: Participants in the MacTel Natural History Observation Registration Study.

Methods: Best-corrected visual acuity (BCVA) data, retinal imaging data, and clinical data were accessed from the MacTel Study databases in May 2019.

Main outcome measures: Frequency distribution of BCVA and its relationship to age; morphologic changes in eyes with very late disease stages, defined by a BCVA of 20/200 or worse; average retinal thickness of macular subfields on OCT; and dimensions of the area affected by MacTel (i.e., the MacTel area).

Results: Best-corrected visual acuity was 20/50 or worse in 37.3% and 20/200 or worse in 3.8% of 4449 eyes of 2248 patients; 18.4% and 0.7% of all patients showed bilateral BCVA of 20/50 or worse and 20/200 or worse, respectively. Asymmetry between right and left eyes was present (median BCVA, 71 letters vs. 74 letters), a finding supported by more advanced morphologic changes in right eyes. Participant age correlated with BCVA, but the effect size was small. If a neovascularization or macular hole were present, bilateral occurrence was frequent (33% or 17%, respectively), and BCVA was better than 20/200 (79% or 78%, respectively) or 20/50 or better (26% or 13%, respectively). Eyes with advanced disease (BCVA, ≤20/200) showed the following characteristics: (1) atrophy of the foveal photoreceptor layer with or without associated subretinal fibrosis; (2) an affected area, termed MacTel area, limited to a horizontal diameter not exceeding the distance between the temporal optic disc margin and foveal center, and the vertical diameter not exceeding approximately 0.8 times this distance (exceptions were eyes with large active or inactive neovascular membranes); (3) reduced retinal thickness measures within the MacTel area; and (4) less frequent retinal greying and more frequent hyperpigmentations compared with eyes that have better BCVA.

Conclusions: Severe vision loss is rare in MacTel and is related to photoreceptor atrophy in most people. Results indicate disease asymmetry with slightly worse vision and more advanced disease manifestation in right eyes. MacTel-related neurodegeneration does not spread beyond the limits of the MacTel area.

Figure 3.

Frequency distribution of best-corrected visual acuity values for all eyes, and for right and left eyes separately. The vertical dashed lines show Snellen visual acuity cutoffs at 20/50 (68 letters) as the threshold for the ability to drive, as well as 20/200 (38 letters) and 20/400 (23 letters) as the limits for legal blindness in the United States and many European countries, respectively. Box plots show median (thick line), interquartile range (IQR; box), and data extremes (end of whiskers) at 1.5 times the IQR away from the lower or upper quartile (or upper maximum). ETDRS = Early Treatment Diabetic Retinopathy Study.

Figure 5.

Graphs showing effect of age on best-corrected visual acuity (BCVA) in macular telangiectasia type 2 (MacTel). A, B, Frequency and relative frequency (in percent) of severe vision loss (≤20/200) and BCVA between better than 20/100 to 20/50. The eye with lower visual acuity was selected for this analysis (n = 2247 eyes, because age was not available for 1 patient of the BCVA analysis group). The graph in (A) shows the distribution of BCVA ranges as a function of age. (B) The fraction of patients with severe vision loss (≤20/200, black dots) does not seem to he higher in older patients. C, Median BCVA (dots) as a function of age. The gap represents the interquartile distance, and the whiskers extend to the data extremes. The dashed line shows the regression line (with error) from a simple linear regression model.

Figure 6.

Images showing exemplary cases for structural correlates to low visual function (best-corrected visual acuity [BCVA], ≤20/200): color fundus photographs (CFPs; first column), fundus autofluorescence images (second column), fluorescein angiography images (third column), and spectral-domain (SD) OCT images (fourth column). Dashed lines in the CFPs show the position of the SD OCT scans. The OCT images show regular retinal layers outside the macular telangiectasia area in all cases.

Figure 7.

Bar graphs showing best-corrected visual acuity (BCVA) distribution of eyes with (A) neovascular changes and (B) full-thickness macular holes. Most eyes demonstrated best-corrected visual acuity of better than 20/200 (38 Early Treatment Diabetic Retinopathy Study letters).

Figure 8.

Images showing examples for eyes with fibrosed neovascularization or full-thickness macular hole (FTMH) with good and poor best-corrected visual acuity (BCVA), respectively. A, Small subretinal fibrosis temporal to the foveal center with well-preserved BCVA (20125 Snellen). B, Large subretinal fibrosis with poor BCVA. The diagnosis of macular telangiectasia was made based on historic images. C, Small, slightly paracentral FTMH with well-preserved BCVA (20/25 Snellen). D, Large FTMH with complete outer retinal atrophy, especially in the temporal parafovea, with poor BCVA (20/320, Snellen).

Figure 9.

Bar graphs showing frequency of funduscopic findings characteristic for macular telangiectasia type 2, grouped according to different ranges of best-corrected visual acuity (BCVA): (A) greying, (B) pigment, (C) crystals, and (D) blunted vessels. Missing information was because of unavailable or ungradable fundus images.

Figure 10.

Diagrams showing the extension of macular telangiectasia-relared fluorescein-angiographic changes in eyes with severe vision loss (best-corrected visual acuity, ≤20/200) (A) without and (B) with neovascular change. Right and Left eyes were considered equally. Gray level represents the cumulative frequency of angiographically visible changes at a given location, plotted for each eye based on horizontal and vertical measures. Darker gray level indicates higher frequency. d = distance between temporal optic disc margin and foveal center.