Zinc uptake by primate retinal pigment epithelium and choroid.

We studied zinc uptake by nonhuman primate retinal pigment epithelium (RPE) and choroid, using 65Zn as a probe. With intravenously administered 65ZnCl2, virtually all detectable tracer was lost from the plasma after 20 hours but the pigment epithelium-choroid showed prominent uptake and retention. Plasma concentrations of oral 65ZnO remained high 20 hours after feeding. Uptake and retention of orally administered 65Zn as 65ZnO from the bloodstream by the RPE/choroid was avid in both young and old animals. Excretion in urine and feces was minimal. All pigmented ocular tissues took up and retained 65Zn. A survey of total zinc content of human and nonhuman primate ocular tissues showed that the pigmented tissues had consistently higher concentrations of zinc. Our results demonstrate for the first time direct uptake and retention of zinc from the blood by primate RPE and other ocular tissues.

Blood flow in the normal human retina.

The laser Doppler technique was used to measure the blood flow rate in 41 major vessels in ten eyes of healthy volunteer subjects. The specific relationship between blood flow rate, F, and vessel diameter, D, was determined for both retinal arteries and retinal veins. On average, F increased with increasing D at a power of 4.1, consistent with the presence of Poiseuille flow. In six eyes of six subjects, measurements on individual vessels were combined to yield the total retinal blood flow rate. The mean and standard deviation of the total retinal blood flow was 80 +/- 12 microliter/min. The blood flow rate per unit mass of retinal tissue was calculated and found to be in good agreement with that reported for macaque monkeys. Blood flow to the temporal side of the retina was approximately three times larger than to the nasal side. There was no significant difference between blood flow to the superior and the inferior retina.

Treatment of congenital unilateral upper eyelid retraction with a marginal myotomy procedure.

Two children with congenital unilateral upper eyelid retraction were treated successfully with surgery at 2 years of age. Excellent results were obtained using a modification of Grove's marginal myotomy procedure for lengthening the levator palpebrae superiorus muscle. To our knowledge, early surgical treatment for this rare idiopathic disorder has not been reported previously.

Evaluation of micrometric and microdensitometric methods for measuring the width of retinal vessel images on fundus photographs.

The width of retinal vessel images on fundus photographs was determined by projection micrometry and microdensitometry. These methods were evaluated on 12 retinal vessels using the negatives of 570-nm monochromatic fundus photographs. For projection micrometry, the intraobserver reproducibility of vessel width measurements was 1.6%-2.9%, depending upon the experience of the observer. Significant interobserver differences in the measured widths were demonstrated. For microdensitometry, three distinct measurement criteria were used. Significant differences in width as measured by the three criteria were found, but there were no interoperator differences for each criterion. The intraoperator reproducibility of vessel width measurements by microdensitometry was 2.1%-2.5%. Significant differences were found in the vessel widths determined by the micrometry and densitometry methods, and results obtained by micrometry are discussed in terms of edge-detection phenomena.