Stereoscopic Vision in Macular Telangiectasia Type 2

Abstract

Purpose: To investigate stereoscopic vision in patients with macular telangiectasia (MacTel) type 2 and correlate paracentral sensitivity loss to reduced stereoscopic function. Methods: In a prospective single-center study, 50 patients with MacTel type 2 and 25 age-matched controls were investigated. Stereoscopic function was evaluated with Lang I, Titmus, and TNO tests. Sensitivity of the central 16° was tested using fundus-controlled perimetry (microperimetry). Functional loss was quantified as depth, size, and localization of scotomata. Results: Both the Titmus and the TNO test revealed significantly reduced stereoscopic vision in patients compared to controls (p < 0.0001 for both). This applied even to patients with only relative or monocular paracentral scotoma. A strong correlation was observed for reduced stereoscopic vision with horizontal scotoma size and with the distance of scotomata from the foveal center. Conclusions: The results indicate that stereoscopic vision is impaired early in patients with MacTel type 2. A paracentral sensitivity loss, even if mild and limited to one eye, may considerably interfere with stereoscopic function despite normal visual acuity. Projection of paracentral scotomata within the patient’s central visual field plays an important role in stereoscopic vision and should be considered when interpreting stereoscopic test results.

Binocular Inhibition of Reading in Macular Telangiectasia Type 2

“…22 Scotomas of the left eye are projected on the right side of the fixated letter/word and hence in reading direction, thus interrupting the perceptual span required for reading (Figs. 4,6). Interestingly, in our sample, left eyes had generally lower reading speed than right eyes, which would be in keeping with this idea ( Supplementary Fig.…”

“…Our previous finding of an early impaired stereoscopic vision in MacTel would be in keeping with this concept. 6 Impairment of binocular fusion might also partly explain the phenomenon of ''dancing'' or ''lost'' letters, which is frequently reported by patients with MacTel (unpublished observation). Figure 6 attempts to simulate impaired monocular reading and impaired binocular fusion when reading.…”

“…1 Disease-related changes seem to first arise in the temporal parafovea, eventually leading to focal loss of photoreceptors and hence paracentral scotomas. [1][2][3] Paracentral scotomas were shown to be associated with reading difficulties and impaired stereoscopic vision [4][5][6] and can be visualized with fundus-controlled perimetry (microperimetry). Microperimetry enables a precise determination of retinal position, size, and depth of scotomas.…”

Functional Relevance of Hyper-Reflectivity in Macular Telangiectasia Type 2

“…18 Typical symptoms that have been shown to be associated with paracentral scotomas in MacTel are reading difficulties 4 and an impairment of stereoscopic function. 25 Central visual acuity, however, may be relatively preserved due to the paracentral nature of structural changes. 4,6 In line with these findings, we observed no correlation between hyper-reflective changes and BCVA.…”