Investigative ophthalmology最新文献

This investigation demonstrates that dextran passes into rabbit corneas stored in M-K medium prior to corneal transplantation. An equilibrium between dextran in the cornea and in the M-K medium is reached at about 24 hours. Post-keratoplasty dextran efflux is rapid with about 70 to 75 per cent being lost within one to three hours and 99 per cent being lost in 12 hours.

Hyperosmotic agents (2 M urea or 2 M DL-lactamide), perfused into the internal carotid artery of Rhesus monkeys, produced a marked decrease in intraocular pressure and an increase in aqueous humor protein. Fenestrae of the ciliary capillaries were broken immediately following the perfusion and the nonpigmented epithelium was separated from the pigmented epithelium. The pigmented epithelium especially of the pars plana then became degenerative. As intraocular pressure began to rise slowly, three to seven days after perfusion, the nonpigmented epithelium recovered to an almost normal structure, but the pigmented epithelium did not regenerate. The surviving cells in the pars plicata formed the original apico-apical junctions. The number of vacuoles in the endothelium of Schlemm's canal decreased while the intraocular pressure was low and increased gradually with the recovery of the intraocular pressure.

The major beta-crystallin fractions from the human lens and the lenses of other selected primates have been isolated and partially characterized. Primate beta-crystallins, like those of most other mammals, consist of two heterogenous protein fractions (betaH and beta L) of quite different molecular size. Most of the polypeptide chains comprising the betaH and beta L heteropolymers are common to both fractions. Evidence is presented suggesting that primate betaH-crystallin may be smaller than betaH from other vertebrate species. Additionally, human betaH is found to contain a major component on sodium dodecyl sulfate (SDS) electrophoresis which is much larger (about 60,000 daltons) than other beta-crystallin polypeptides. Immunochemical evidence inidcates that some components of primate beta-crystallin have evolved rapidly, although at least one antigenic component is very conservative and gives a reaction of identity with all other vertebrate beta-crystallins studied.

The transmittance of the ocular media has been measured in vivo in rabbit eyes using an argon laser light source and microthermocouple sensor. The intensity profiles at the cornea and retina were measured with the thermocouple and the ratio of the power associated with the intensity profiles indicated the fraction of light power reaching the retina. Measurements from 10 rabbits indicated a transmittance coefficient of 0.85 for wavelengths between 488 and 514.5 nm.

This report compares the reproducibility of analog and digital photogrammetry for topographical analysis of the optic cup. Ten simultaneous stereophotographs of each of three optic discs were taken with the Zeiss fundus camera plus a twin-prism stereoseparator. Digital processing produced photogrammetric contours of the optic cup and estimates of its geometry. Optic cup contours from the same stereopairs were also drawn with an analog stereoplotter and were analyzed by manual planimetry. The reproducibility of digital photogrammetry and analysis for estimation of cup depth, cup width, cup cross sectional area, and cup volume was concluded to be generally superior to the reproducibility of analog photogrammetry and manual analysis.

Two patients with unilateral abducens palsy used their paretic-but visually superior-eye for fixation. In these patients, adaptive changes of saccadic amplitude and of the relation between phasic and tonic components of saccades were found. These changes led to a reduction of foveation time.

The mydriatic effect of topically applied 3H-atropine (2%) was compared in the pigmented rabbits (black fur and dark brown irides) and nonpigmented (albino) atropinesterase-negative rabbits. The duration, t1/2, of the mydriatic effect in the nonpigmented and pigmented rabbit was 43.5 and greater than 96 hours, respectively. At hour 96, the tissue 3H-atropine in the pigmented iris was greater than that in the nonpigmented iris by the factor of eight. The longer duration of mydriatic effect in the pigmented iris is explained by the slow release of the bound drug from the pigment onto the muscarinic receptors.

Retractor bulbi muscles of mouse and rat were examined by light and electron microscopy. Two morphological fiber types were observed, analogous to Type I and Type II cells of skeletal musculature and comparable to fibers observed in the global region of the rectus extraocular muscles of these species.

A transient iridocyclitis is produced in rabbits by the intravenous injection of bacterial endotoxin. A major feature of this response is an altered vascular permeability which can be measured by the ocular accumulation of circulating 125I-labeled albumin. The present study was made to determine the effects of inhibitors of prostaglandin synthesis of the ocular response to an E. coli 055:B5 endotoxin. Aspirin pretreatment prevented the ocular response following the intravenous injection of 10 mug per kilogram of endotoxin, but had no effect following 100 mug per kilogram. Indomethacin pretreatment prevented an alteration in ocular vascular permeability 1 1/2 hours after the injection of 100 mug per kilogram of endotoxin and significantly reduced the alteration 4 hours after endotoxin. Thus inhibitors of prostaglandin synthesis can prevent the ocular response to circulating endotoxin depending on their relative potency and the amount of injected endotoxin. These results suggest that prostaglandins are important in the ocular response to circulating endotoxin in the rabbit.

Axonal transport in primate optic nerve axons was studied by autoradiography, scintillation counting, and electron microscopy under conditions of short-term intraocular pressure elevation. With elevation of intraocular pressure to 30 mm. Hg below mean arterial blood pressure, blockage of transport was detected within 2 hours by autoradiography and within 1 hour by electron microscopy. The earliest buildup of radioactively labeled protein and ultrastructurally visible cellular organelles was within the scleral lamina cribrosa. The degree of blockage, judged by amount of label buildup, increased with time. Some transported material traversed the lamina cribrosa despite pressure elevation at the level tested. Reversal of transport blockade occurred rapidly after normalization of intraocular pressure.