Central Retina Functional Damage in Usher Syndrome Type 2: 22 Years of Focal Macular ERG Analysis in a Patient Population From Central and Southern Italy

Lucia Galli-Resta,Silvia Iovine,Benedetto Falsini,Francesca Campagna,Giorgio Placidi,Paolo Maltese,Edoardo Abed,Matteo Bertelli,Marco Piccardi,Angelo Minnella,Lucia Ziccardi

doi:10.1167/iovs.17-23703

Abstract

Recent studies show that patients with Usher syndrome type 2 (USH2) have abnormal cone structure and density in the central retina. This occurs in the presence of normal acuity, opening the quest for additional sensitive functional measures of central cone function in USH. We tested here whether focal macular cone electroretinogram (fERG) could be such a tool. This retrospective study of central cone function loss was based on data from 47 patients with USH2 from the Ophthalmology Department of the Policlinico Gemelli/Catholic University in Rome. The analysis focused on the decrease of the fERG, obtained in response to a 41-Hz sinusoidal modulation of a uniform field presented to the central 18°, generated by red light-emitting diodes (LEDs) and superimposed on an equiluminant steady adapting background. fERG decrease was compared with the decrease of best-corrected visual acuity and Goldmann kinetic perimetry V4E field. fERG follow-up data document a severe and precocious loss of central cone function in USH2 patients, preceding losses in other measures of cone function. fERG is already reduced to 40% of control at the beginning of the second decade of life, and by 25 years of age, all USH2 patients have fERGs less than 30% of control values. fERG represents a sensitive tool to evaluate central cone function in USH2, anticipating the decline of other central cone function measures, such as visual acuity and Goldmann perimetry.

Highlights

The analysis focused on the decrease of the focal macular cone electroretinogram (fERG), obtained in response to a 41-Hz sinusoidal modulation of a uniform field presented to the central 188, generated by red light-emitting diodes (LEDs) and superimposed on an equiluminant steady adapting background. fERG decrease was compared with the decrease of best-corrected visual acuity and Goldmann kinetic perimetry V4E field
RESULTS. fERG follow-up data document a severe and precocious loss of central cone function in Usher syndrome type 2 (USH2) patients, preceding losses in other measures of cone function. fERG is already reduced to 40% of control at the beginning of the second decade of life, and by 25 years of age, all USH2 patients have fERGs less than 30% of control values
Usher syndrome (USH) is an autosomal recessive group of diseases characterized by the association of retinitis pigmentosa (RP)-like retinal degeneration with bilateral sensory-neural hearing loss.[1]

Summary

Methods

This retrospective study of central cone function loss was based on data from 47 patients with USH2 from the Ophthalmology Department of the Policlinico Gemelli/Catholic University in Rome. Patients were clinically followed at the Institute of Ophthalmology, Visual Electrophysiology Service at Fondazione Policlinico Gemelli/Universita Cattolica del S. A detailed medical and family history was obtained from the patient and/or their parents. This included information regarding age of diagnosis of hearing loss, nature of hearing loss, age of perceived night blindness, age of RP diagnosis as well as information regarding motor development (age at which the patient first sat and walked, as well as whether and when the patient learned to use a bicycle, a discriminating criterion for vestibular integrity)

Results

Discussion

Conclusion