James Price

Oscillatory potentials. History, techniques and potential use in the evaluation of disturbances of retinal circulation

The oscillatory potentials seem to reflect severe disturbances in the retinal (and perhaps choroidal) circulation. In some cases of diabetic retinopathy with severe microangiopathy, the oscillatory potentials may be selectively reduced or extinguished while the amplitude of the a- and b-waves of the ERG remains normal. A correlation appears to exist between severely reduced oscillatory potentials and a circulatory deficiency in the retina. This selective reduction of the oscillatory potentials during advancing retinopathy is considered to be indirect evidence that they are generated independently from the mechanism producing the primary components (the a- and b-waves). The usefulness of the oscillatory potentials in the prognosis of retinal disease, particularly in diabetic retinopathy, is reviewed. The historical background, the techniques and instrumentation necessary to produce and record them, the experimental data available on the site of their origin, the clinical significance to date and the experimental efforts in our laboratory are summarized.

Familial Retinal Arteriolar Tortuosity with Retinal Hemorrhage

The syndrome of familial retinal arteriolar tortuosity with retinal hemorrhages is a rare inherited disorder. 1,2 We have examined an American family in which three generations have had this condition.

Effect of adaptation and wavelength on the power spectrum of human oscillatory potentials

Oscillatory potentials were recorded from four adult subjects under dark- and light-adapted conditions with photopically balanced red and blue flashes. The responses between 80 and 200 Hz were analyzed by means of a Fast Fourier transform program. The results show a robust change in the power - but not in the frequency composition - with the different stimulus conditions. We suggest that an analysis of the total power within this frequency band may provide a quantitative way of evaluating the duplex nature of the oscillatory potentials.

Asteroid hyalosis and axial length measurement using automated biometry

ABSTRACT Accurate axial length measurements are needed before intraocular lens implantation in patients with asteroid hvalosis requiring cataract extraction. We suspected that falsely short axial length measurements may be obtained using automated A‐scan biometry when we found an automated measurement of 15.90 mm in a patient with severe unilateral asteroid hvalosis. A manual biometry measurement of 21.90 mm was obtained for comparison; this was within 0.2 mm of the manual reading in the opposite uninvolved eve. A case‐control study was performed on 20 unilateral asteroid hyalosis subjects using the uninvolved eye as the control, comparing automated biometn and manual A‐scan biometry to assess the effect of asteroid hyalosis on automated biometry measurements. Five subjects (25%) with asteroid hvalosis had falsely short axial length measurements of more than 1.00 min using automated biometry. This would result in more than 2.50 diopters of error in the implanted lens power. This case‐control study demonstrates that falsely short axial length measurements may be obtained using automated biometry in patients with asteroid hvalosis, leading to significant error in intraocular lens power calculations.

Changes in lysosomal enzyme activities of eye tissues in endotoxin-induced inflammation

Lysosomal enzyme activities in rabbit ocular tissues were examined at various times after the intravitreal injection of endotoxin. Lysosomal enzyme activities in the aqueous, vitreous, and pigment epithelium-choroid were elevated 3 h after injection. It is deduced from the fluorescein-labeled dextran and SDS-polyacrylamide gel electrophoresis analysis of the aqueous, vitreous, and pigment epithelium-choroid from endotoxin injected rabbits that the elevation of lysosomal enzyme activities are probably due to a breakdown in blood-ocular barriers.

Selective abnormality of the cone B-wave in a patient with retinal degeneration

A 44-year-old woman with midperipheral pigmentary changes that resemble retinitis pigmentosa (RP) is described; unlike typical patients with RP, her photopic b-wave was markedly attenuated as compared with her photopic a-wave. Otherwise, her electroretinogram (ERG) was typical of patients with early stages of photoreceptor degeneration. Scotopic and photopic a-wave amplitudes were reduced about 50%; her scotopic b/a appeared normal.

Cranial Nerve Damage in Patients after α (Heavy)-Particle Radiation to the Pituitary

Abstract The records of 161 patients were reviewed to determine if radiation damage had occurred following cranial irradiation. All of these patients had received α-particle radiation to their pituitary glands during the period when this form of therapy was given for diabetic retinopathy. Extraocular muscle palsy developed in 11 of these patients, iridoplegia in six, and fifth nerve damage in six. All of the palsies developed within a short period following their irradiation, and a definite dose relationship was present. The dose rate was approximately 100 rads/min for all cases. Fractionation varied but it is known for all cases. The estimated doses to the third, fourth, fifth, and sixth cranial nerves was calculated at a saggital plane 13 to 15 mm from the pituitary by using computer-drawn dosimetry charts for the respective aperture size. The energetic α particles were produced by the 184-in synchrocyclotron at Berkeley, Calif. A dose relationship for radiation palsies was apparent.