Metamorphopsia in patients with macular telangiectasia type 2.

Purpose: To assess metamorphopsia in patients with macular telangiectasia (MacTel) type 2.
Methods: In a prospective observational cohort study, 40 eyes of 20 patients with MacTel type 2 were investigated by funduscopy, fluorescein angiography, optical coherence tomography and microperimetry. Metamorphopsia was assessed using Amsler grids following a standard protocol and standardized questionnaire.
Results: Metamorphopsia was present in 30 (83%) out of 36 nonproliferative eyes and in all four eyes with neovascular membranes. In the 30 nonproliferative eyes with distortions, metamorphopsia was always present in the nasal quadrant of the central visual field. Distortions were most pronounced in the nasal and lower quadrant in 70 and 30%, respectively. Three nonproliferative eyes with a very early and three eyes with a late disease stage did not perceive metamorphopsia. The degree of distortions was often but not necessarily correlated with the degree of leakage. Metamorphopsia was present in five out of eight eyes with normal sensitivity in microperimetry testing. Detection of scotoma by Amsler grid testing was poor.
Conclusion: Metamorphopsia is a frequent clinical symptom in MacTel type 2 even in the absence of neovascularization. Since macular thickness was within normal limits in such eyes, extensive swelling or distortion of the neurosensory retina would not account for metamorphopsia in contrast to other macular diseases such as age-related macular degeneration or idiopathic epiretinal membranes.