Spatial summation in the paracentral visual field in carriers of Leber's hereditary optic neuropathy

Purpose: To identify if genetically pinpointed asymptomatic LHON individuals show visual field dysfunction in the absence of typical central scotoma. Method: Contrast perimetry (CP):The detectability of 2-D gabor patches as a function of their size was measured using 4AFC in each quadrant of the visual field. Each patch was centered on 4′ from fixation on a diagonal. Five diameters (from 1′ to 7′) and two different spatial frequencies were presented randomly as the stimuli. Eight homoplasmic subjects (mutation 11778), 2 affected, 5 non-affected and 1 recovered and 5 normals served as subjects. Two subjects had repeated tests. Results: Normals and unaffected family members were indistinguishable at any patch size visual field quadrant or spatial frequency. Repeatability of individual data points was within 3 db (0.15 log). Both affected individuals showed that losses were independent of spatial frequency. The recovered patient showed significant losses in spite of normal acuity. Conclusion: CP is a reliable method. In this small sample it had not identified a genetically determined vulnerability of the VF. CP longitudinal studies are needed to evaluate if CP could serve in the follow-up of individual patients.