Evaluation of the visual pathway with ERG, mfERG and mfVEP in inherited eye disorders

University dissertation from Department of Ophthalmology, Lund University

Abstract: This thesis will describe the clinical phenotypes, with emphasis on electrophysiology, in patients with different hereditary eye diseases and to further evaluate and modify the mfVEP technique for clinical use. Bothnia Dystrophy is a tapetoretinal disorder with a mutation in the RLBP1 gene. Early in the disease the fundus may have a normal appearance. The full-field ERG demonstrates an absence of the rod response but normal amplitudes for the cones. However, after prolonged dark adaptation the rods recover completely. MfERG can be used for objective documentation of the disturbed macular function. Patients with retinitis pigmentosa may not always follow the typical natural course of the disorder with progressive loss of the central visual fields, which may in some patients remain unaffected for several decades. MfERG and mfVEP may be of clinical use in evaluating remaining visual function in these patients. Patients with dominant optic atrophy and a known mutation in the OPA-1 gene have a very variable clinical phenotype. MfVEP and ocular blood flow measurements are two new methods for improved identification and characterization of this disorder. A patient with a known mutation for Leber`s hereditary optic neuropathy (LHON) was followed during the acute stage of the disease with mfVEP, demonstrating a correlation to the progression of the disease. The mfVEP may be of clinical value as an objective method for monitoring the course of this disease. MfVEP demonstrates the cortical response corresponding to the central visual field. An improvement for the clinical value of the method was the use of an IR-camera for both stimulation and for controlling the fixation. By introducing a two channel system it was possible to describe the uncrossed/crossed visual pathways and analyze inter-ocular differences.