Abstract
Purpose::
Goldmann visual fields (VF) are used routinely in monitoring the visual loss in retinitis pigmentosa (RP). The visual outcome can vary widely even between different members of the same family. However, the qualitative nature and inherent variability in the Goldmann VF can cause difficulties for the clinician. We explore the use of serial wide field multifocal electroretinography (mfERG) in monitoring and developing prognostic information of patients with RP.
Methods::
A retrospective analysis of 33 patients with different phenotypic variants of retinitis pigmentosa was undertaken. Follow up ranged from 32 months to 27 years. Assessments included best-corrected snellen visual acuity, slit lamp biomicroscopy and fundus examination, serial Goldmann VFs, Ganzfield electroretinography (ERG) and multifocal electroretinography using a custom built wide field mfERG.
Results::
Age range: 18-80 years (median: 55). Visual acuity at last follow-up ranged from no perception of light to 6/5. Various distinctive patterns and varying severities of visual field constriction were noted on the Goldmann VF. Variability in the Goldmann VF was demonstrated with inconsistent changes in the shape and severity of VF constriction, and clinically unexplainable transient improvements being noted in at least 1 follow-up visit in all 33 patients. The mfERG was able to provide an objective measure of the rate of progression of the loss of retinal function. In 2 patients the mfERGs allowed the earlier diagnosis of RP as the mfERGs demonstrated progressive losses in retinal function despite the ERG and Goldmann VF being normal in the initial years.
Conclusions::
Establishing an exact genetic diagnosis is not always possible. However, the use of serial mfERG can be used to diagnose RP at an earlier stage as the changes precede changes in the Goldmann VF. The mfERG is a more objective test than the Goldmann VF for monitoring the rate of progression RP and serial mfERGs provide more reliable prognostic information for patients. The relationships between the mfERG amplitudes and implicit times, and the Goldmann VFs are however complex and further study is recommended.
Keywords: electroretinography: clinical • perimetry • retinal degenerations: hereditary