R. Magni

Unilateral Retinitis pigmentosa: Clinical and Electrophysiological Report of Four Cases

Unilateral retinitis pigmentosa (URP) is a rare tapetoretinal dystrophy affecting only one eye. The François and Verriest criteria are necessary to make a correct diagnosis of URP: exclude all infective etiologies, check that the clinical signs of retinitis are present in the affected eye and ensure the total absence of any signs or symptoms of retinitis pigmentosa in the fellow eye. The standard electroretinogram and standard electro-oculogram are very useful for the correct diagnosis. Other pigmentary retinopathies simulating retinitis pigmentosa have to be excluded, such as previous retinal inflammatory diseases like syphilis, rubeola, other viral diseases and onchocerciasis. In this paper, 4 cases of URP are reported.

Single-sweep analysis using an autoregressive with exogenous input (ARX) model

Single-sweep visual evoked potential analysis would be useful in clinical electro-physiology practice because it would make possible the evaluation of transient phenomena, but recording single-sweep visual evoked potentials is difficult because of the low signal-noise ratio. To increase this ratio we used a filter based on an autoregressive with exogenous input model. We studied a group of 12 diabetic patients matched with a control group of 14 normal subjects. The model, in most cases, allowed us to extrapolate the P100 component from each single sweep of visual evoked potential. The visual evoked potential values obtained by means of averaging were not significantly different in the groups studied, but single-sweep analysis showed different distribution of the P100 component amplitude. The preliminary results of our study evidenced differences in the amplitude and latency distribution of normal and diabetic subjects, thus confirming the power of this new technique and its ability to obtain some information that is masked by the averaging method.

Effect of myopic excimer laser photorefractive keratectomy on the electrophysiologic function of the retina and optic nerve

Purpose: To assess by electrophysiologic testing the effect of photorefractive keratectomy (PRK) on the retina and optic nerve. Setting: Eye Clinic, S. Salvatore Hospital, L’Aquila University, Italy. Methods: Standard pattern electroretinograms (P‐ERGs) and standard pattern visual evoked potentials (P‐VEPs) were done in 25 eyes of 25 patients who had myopic PRK for an attempted correction between 5.00 and 15.00 diopters (D) (mean 8.00 D). Testing was done preoperatively and 3, 6, 12, and 18 months postoperatively. The contralateral eyes served as controls. During the follow‐up, 3 patients (12%) developed steroid‐induced elevated intraocular pressure (IOP) that resolved after corticosteroid therapy was discontinued. Results: No statistically significant differences were seen between treated and control eyes nor between treated eyes preoperatively and postoperatively. Conclusion: Myopic excimer laser PRK did not seem to affect the posterior segment. The transient steroid‐induced IOP rise did not seem to cause functional impairment.

Best's multiple vitelliform degeneration

Bests disease with multifocal lesions is rare. The authors describe four cases of multifocal vitelliform disease. The fluorescein angiographic features of macular and extramacular lesions are considered. Different stages of evolution may be present between central and extramacular lesions.

Homonymous bilateral hemianopsia : electrophysiological study of a case

Described is a case of bilateral homonymous hemianopsia with macular sparing, resulting from head trauma. The case presented lesions of the occipital visual areas which involved entirely the left hemisphere and only partially the right hemisphere. VEP were obtainable only from electrodes placed on the right hemisphere with both right eye and left eye stimulation. VEP mapping showed that each eye projects macular fibres towards functional areas of the right occipital hemisphere. Electrophysiological examination confirmed objectively and for the first time in man the theory of “double cortical macular representation”. Clinical implications of this finding are discussed.

Electroretinographic findings in congenital oculomotor apraxia (Cogan's syndrome)

We performed visual evoked potential testing and electroretinography in five patients with Cogans oculomotor apraxia. The visual evoked potentials were normal, confirming previously reported data. Electroretinograms were abnormal in two of the five patients examined. A previous study showed normal electroretinogram responses bilaterally in one patient. Our findings suggest the existence of two variants of the syndrome; the one with electroretinogram anomalies has a worse visual prognosis.