Comparison of central corneal thickness measurements between optical and ultrasound pachometers.

The central corneal thickness measured by 2 methods was compared in 31 normal subjects. At each of the two examinations, central corneal thickness was evaluated by an ultrasonic and an optical method. Reliability was assessed by an analysis of variance (ANOVA) between repeated measurements for the electronic digital and the Humphrey ultrasonic pachometers. The former revealed a systematic right-left difference, the left cornea being significantly thicker. This phenomenon has been observed in many studies and has been attributed to a measurement not done perpendicularly to the cornea. Angle lambda measured on eight subjects was nasal in all cases. A very high correlation coefficient was obtained between the two methods of central pachometry and the results obtained for the right eye by these two methods were not significantly different. Also, a small but significant negative correlation was observed between the central corneal curvature and the corneal thickness as evaluated by either pachometer.

Localization and characterization of specific receptors for atrial natriuretic factor in the ciliary processes of the eye.

By light and electron microscope radioautography in vivo, competitive binding sites for 125I-Arg 101-Tyr 126 atrial natriuretic factor were localized mostly on the "pigmented" epithelium of the rat ciliary process. Further investigation using isolated ciliary processes from rabbits demonstrated the presence of specific receptors for 125I-atrial natriuretic factor. In addition, synthetic atrial natriuretic factor inhibited basal and stimulated adenylate cyclase activity. These results demonstrate for the first time the presence of specific receptors for atrial natriuretic factor in the ciliary processes which are negatively coupled to adenylate cyclase. The possible role of this peptide in the control of intraocular pressure is suggested.

The retinal capillaries of the rat in deoxycorticosterone hypertension. An ultrastructural study with the diffusion tracer lanthanum.

Unilaterally nephrectomized rats treated with deoxycorticosterone and 1% sodium chloride in their drinking water developed severe systemic hypertension with marked cardiac and renal lesions. No pathologic changes could be detected in the retinal vasculature by light microscopy, but electron microscopy revealed inconstant alterations in the pericytes of retinal capillaries: these cells showed hyaloplasmic edema, margination of chromatin, dilatation of rough endoplasmic reticulum, and swelling of mitochondria. Injection of lanthanum into control rats confirmed that this 40-A tracer cannot pass the interendothelial tight junctions. In hypertensive animals, however, it penetrated these junctions and could be visualized in capillary basement membranes and between cells of the retina. The results indicate that an increase in permeability is probably the first pathologic change to occur in the retinal capillaries of hypertensive rats.