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Semiquantitative fluorescein photometric studies were performed on the retinas of lyophilized rat eyes. Before injecting the fluorescein, the right, dyeless eyes were enucleated under anesthesia with ketamine hydrochloride. The left eyes were removed between 20 seconds and two hours after intravenous injection of fluorescein. Histologic sections of each of the posterior segments were measured fluorophotometrically. The photometric values of most of the fluorescein-dyed retinal sections were higher than those of the contralateral (dyeless) control eyes. With increasing duration of observation the differences between the sections which contained fluorescein and those which did not diminished, although some temporary and limited increases occurred. The higher extinction values of the specimens containing fluorescein are in agreement with the quantitative results of Grimes et al. (1982), who found fluorescein in all retinal layers. Anesthesia-induced acidoses cannot be ruled out may be considered minimal. The information value of quantitative and semiquantative results is certainly superior to qualitative results is certainly superior to qualitative findings.

A presentation is given of a malignant melanoma of the choroid of a 15-year-old girl. The tumor was erroneously considered as to be a subretinal hemorrhage produced by a choroidal rupture after an accident. A beginning melanosis bulbi resulted in the enucleation and the histological examination of the eye, which confirmed malignant melanoma of the choroid.

Simultaneous photographic or angiographic studies of the anterior and posterior segments requires a considerable reduction in the respective parts of the negatives; this can be avoided by simultaneous study of the one segment ipsilaterally and the other contralaterally (this can also be performed vice versa). Differences and common properties of the eyes of rabbits and miniature pigs and the human eye are described. Apart from the monkey eye, the pig eye is most readily comparable with the human eye as regards vasotopographic and vasomorphologic conditions. In addition, the courses of angiographies in the eyes of experimental animals were observed; measurements of fluorescein inflow and circulation times in the anterior and posterior segments in miniature pigs are presented. These were subjected to significance tests: only the difference in the inflow and outflow of the dye in retinal vessels was found to be statistically highly significant. The difference in inflow between choroidal and retinal vessels was not significant, though this may have been due to an error of measurement. The techniques and measurements described represent the basis of observation in miniature pigs with experimentally induced hypertension.

After local application of gentamycine, dexamethasone and tropicamide to rat eyes, no effect was observed on the permeability of the vascular wall of the iris and ciliary body compared with fluorescein-Na. Nor were there any changes in vessel caliber. The constriction of the dye column observed in corneal neovascularizations was not seen in the (normal) iris vessels and the vessels of the ciliary body. With regard to the iris region, however, this might be due to mechanical causes and/or the possibility that vessels of different origins react differently.

For contributing to the question of an existence of a diffusion of the unbound part of the fluorescein between choroid and retina in fluorescein angiography, on pigmented rats, after intravenous injection of Fluorescein sodium and Rhodamine B respectively, comparing observations were effectuated. Rhodamine B in its unbound form showed a distinct diffusion between choroid and retina and coloured all retinal layers in the late phases whereas in the case of the Fluorescein sodium, only a poor diffusion was observable. The similar spectral bands of the primary and secondary fluorescences render difficult the observation of the behaviour of the fluorescein dye.

After local application of gentamicin, dexamethasone and tropicamide to rat eyes, no effect on the permeability or the caliber of retinal vessels was observed, nor any diffusion of fluorescein from the choriocapillaris to the outer retinal layers. The qualitative assessment of fluorescence microscopic preparations (and photographic reproductions of them) is relatively unreliable and has led to confusion in the literature. The results presented here, which to some extent contradict earlier findings published in 1971, are discussed. The authors expect to obtain more accurate results from the quantitative method which they are now using.

We conceived and manufactured a holder for rats. It is a useful little apparatus for some experiments on rats as well as for its fundus photography, angiographies included. The utility of our device is discussed and illustrated.

The effects of laser coagulation on rat fundi were studied angiographically and with the fluorescence microscope. The coagulations were performed using constantly 300 mW and 0.2 second exposure time and 50 microns spot diameter. We observed the animals for 3 months, after which we could still observe dye diffusion by fluorescence angiography. With the fluorescence microscope we could localize these diffusions as originating from neovascularisation starting from the choroid. These new vessels penetrated subsequently into the exterior retinal layers. At the beginning of our observation time, the retinal vessels showed some sinuosities, dilatations and solitary stenosis, but no disturbance of circulation was demonstrable.

The influence of clonidine and propranolol on the vessels of the anterior segment and of the fundus, as well as on mean arterial pressure and heart rate, was investigated in normal rabbits, minipigs, and minipigs with experimentally induced hypertension. The vessel reactions were monitored by photography or fluorescein angiography. Following injection of clonidine, constrictions of episcleral and conjunctival vessels occurred in all the animals, but the fundus vessels of the rabbits were not affected. Difficulties were encountered in assessing the condition of the iris vessels. In minipigs, after administering 6-20 micrograms/kg, an average delay of 2 seconds in the inflow into the retinal vessels was recorded, due possibly to a (transitory?) vessel constriction upstream. Mean arterial pressure increased initially in all animals, but to a different extent in the two species. There was less uniformity as regards heart rate. The vessel reactions of the two species to propranolol were different: in rabbits, a reaction was only observed after administering 2.46 mg/kg bodyweight in episcleral and conjunctival vessels, though not in fundus vessels. Minipigs were given doses of 0.16, 0.5, and 0.8 mg/kg; after 0.5 mg/kg a vessel constriction took place in the episclera and the conjunctiva, becoming manifest after 20 minutes and attaining a maximum after 60 minutes. However, there appeared to be no reaction in the fundus vessels. After an abrupt decrease in mean arterial pressure, both this and the heart rate showed an almost identically slow decrease until the 50th minute, followed by a slight increase up to the 60th minute. The comparison of the circulation parameters reveals some interesting parallels, though also some contrasts. The mechanisms of action and characteristics of these two substances are discussed.

Laser treated rat fundi were observed angiographically and with the fluorescence microscope for 3 months. Angiographically diffusions have been observable up to about one week post laser, fluorescence microscopically, however, for the whole observation time of 3 months. From the 2nd week, these diffusions were produced mainly by neovascularizations which angiographically were not visible. They started from the choroid and penetrated into the outer part of the retina.