[Comparative experimental study of morphological and histochemical changes of chorioretinal complex after subthreshold laser exposure].

The influence of several subthreshold laser procedures on chorioretinal complex (CRC) tissues was experimentally studied in rabbits using histological and histochemical methods. Subthreshold micropulse laser radiation and transpupillar thermotherapy were found to have the most attenuated and advantageous effect on CRC structure. The feature of subthreshold laser exposure is partly reversible selective changes in CRC, that have temporary stimulating effect on cellular metabolism and local regenerative processes providing an opportunity for still viable tissues to function adequately.

Intrinsic tissue fluorescence in an organotypic perfusion culture of the porcine ocular fundus exposed to blue light and free radicals.

BACKGROUND: A wide variety of pathological pathways may result in age-related macular degeneration. Because of its complexity, there is no comprehensive model of the disease yet. One key feature is the accumulation of the autofluorescent pigment lipofuscin in the retinal pigment epithelium (RPE). Thus, we developed an organotypic perfusion culture model of the porcine ocular fundus, generating lipofuscin under exposure to blue light and hydrogen peroxide. METHODS: Porcine fundi (choroid, Bruch's membrane, RPE, and retina) were explanted in toto, transferred into a perfusion culture chamber, perfused with cell culture medium and kept at 37 degrees C. Free radical stress was induced by supplementation of H(2)O(2), and/or the specimens were exposed to blue light, or kept untreated as controls. After a culture period of 7 days, the specimens were subject to microscopic inspection, histology, fluorescence microscopy, and measurement of fluorescence spectra as well as fluorescence decay times. RESULTS: Histology showed atrophic ganglion cells and rod outer segments. All other tissue structures were morphologically intact. Compared to the controls, RPE and retina exposed to light showed increased fluorescence, which was shifted towards shorter wavelengths. The fluorescence spectra and decays resembled that of lipofuscin granules isolated from human donor eyes. HPLC analysis revealed the abundance of the lipofuscin component N-retinylidene-N-retinylethanolamine (A2E), its precursor products, as well as two new, green-emitting fluorophores. CONCLUSIONS: Porcine ocular fundi were successfully preserved in an organotypic perfusion culture for 7 days, and exhibited remarkable autofluorescence after light and free radical exposure, making the model suitable for investigations of lipofuscinogenesis.

[Dependence of the efficiency of low-intensity laser therapy in involution chorioretinal dystrophy on a used wavelength]. / Zavisimost' effektivnosti nizkointensivnoi lazernoi terapii involiutsionnoi tsentral'noi khorioretinal'noi distrofii ot primeniaemoi dliny volny.

Seventy-five patients (75 eyes) with central involution chorioretinal dystrophy (non-exudative type at the progression stage) were followed up. All of them received low-intensity laser therapy. Irradiation of 890 nm, 644 nm and 500 nm was used in groups 1, 2 and 3, respectively. The study purpose was to compare the efficiency of wavelengths. Visual acuity and retinal sensitivity were determined. The results were evaluated immediately after treatment and in 3 months. The maximal improvement in visual acuity and retinal sensitivity was in those who received 890 nm laser therapy; 500 nm irradiation--a less pronounced effect and 640 nm--the lowest one. We attribute such distribution of efficiency to a proliferation type of each irradiation range in the macular zone.

Noninvasive technique for monitoring chorioretinal temperature during transpupillary thermotherapy, with a thermosensitive liposome.

PURPOSE: To develop a technique for noninvasive and real-time monitoring of chorioretinal temperature in transpupillary thermotherapy (TTT). METHOD: A modified slit lamp, which was equipped with two laser wavelengths (490 nm for illumination and fluorescein excitation and 810 nm for hyperthermia), was developed for TTT and temperature monitoring. Five types of liposomes were prepared, and their phase-transition temperatures were 40 degrees C, 46 degrees C, 47 degrees C, 48 degrees C, and 52 degrees C, respectively. Carboxyfluorescein was encapsulated in each liposome. After intravenous injection of each liposome, TTT with the modified slit lamp was performed on normal rat choroid or tissue with choroidal neovascularization (CNV). During TTT, chorioretinal temperature was monitored by observing release of fluorescein from circulating liposomes. RESULTS: Fluorescence from liposomes was initially observed around the heated lesion immediately after TTT began and disappeared rapidly when irradiation stopped. Choroidal and retinal temperatures were monitored separately. TTT for normal retina required higher power than that for normal choroid to observe fluorescence from a 40 degrees C, 46 degrees C, and 47 degrees C liposome. Retinal whitening was observed after TTT at a high-power setting. TTT for CNV required higher laser power than that for the normal choroid and retina. CONCLUSIONS: The results demonstrate the potential use of a noninvasive monitoring technique of chorioretinal temperature during TTT. The method should be useful to establish the TTT setting and achieve the optimal temperature increase in CNV.

Transscleral thermotherapy: short- and long-term effects of transscleral conductive heating in rabbit eyes.

OBJECTIVE: To determine the highest safe treatment temperature, at 30- and 60-second exposure durations, for transscleral thermotherapy (TSTT) of choroidal melanoma. METHODS AND DESIGN: Transscleral conductive heating was performed in 15 rabbits at 50 degrees C to 70 degrees C for 30 or 60 seconds. The thermal lesions in the ocular fundus were monitored for 4 months with ophthalmoscopic, photographic, and fluorescein angiographic examination. Histologic examination included polarized light microscopy. RESULTS: The effect of TSTT was similar for both exposure durations. Vascular occlusion in the retina and choroid developed at temperatures of 55 degrees C and higher. After heating at 60 degrees C, scleral collagen fibers developed a minimal undulation; at 65 degrees C, they became clearly undulated. The undulation resolved in the 3 to 4 months after heating. Heating at 70 degrees C caused persistent severe damage to the sclera. Retinal tears developed after heating at 65 degrees C and 70 degrees C. CONCLUSIONS: A temperature of 65 degrees C was found to be the highest temperature that did not cause permanent damage to the sclera at both exposure durations. A temperature of 60 degrees C may be the optimal temperature for TSTT of choroidal melanoma because retinal tears may develop at 65 degrees C. CLINICAL RELEVANCE: In TSTT, the temperature levels reached are cytotoxic for choroidal melanoma as well as intrascleral tumor cells. Occlusion of choroidal vessels induced by TSTT may contribute to tumor necrosis because these vessels serve as feeder vessels for the tumor.

Heat shock protein hyperexpression on chorioretinal layers after transpupillary thermotherapy.

PURPOSE: To assess a biological effect induced by temperature elevation during transpupillary thermotherapy (TTT). METHODS: Six pigmented rabbits were anesthetized, and TTT was performed on the right eye using an 810-nm diode laser installed on a slit lamp (spot size, 1.3 mm; duration, 60 seconds; power, 92-150 mW). A series of laser pulses were aimed at the posterior pole of the retina. The left eyes were used as the control. Twenty-four hours after laser irradiation, a histologic study was performed on the chorioretinal layers. Tissue samples were fixed in formalin and embedded in paraffin. A monoclonal antibody was used to detect heat shock protein (Hsp)70 immunoreactivity, followed by a biotinylated goat anti-mouse antibody, revealed by the avidin-biotin complex and the 3-amino-9-ethyl-carbazole (AEC) chromogen. Retinal structures were further identified by hematoxylin erythrosin saffron (HES) coloration. RESULTS: The photocoagulation threshold was found to be at the 150-mW laser power. Under this threshold, Hsp70 immunostaining was the strongest at the 127-mW power, with staining of some choroidal cells, including capillary endothelial cells. No Hsp70 immunoreactivity was observed on the retina. At the 107-mW power, Hsp70 reactivity was observed only in occasional choroidal cells. At the 98-mW power, only mild, diffuse Hsp70 immunoreactivity was observed in the choroid. At the 92-mW power, as in nonirradiated eyes, no Hsp70 immunoreactivity was detected. CONCLUSIONS: Subthreshold transpupillary 810-nm laser irradiation induces choroidal Hsp hyperexpression. This confirms that choroidal Hsp hyperexpression can be induced during TTT, as has been recently hypothesized by several investigators.

Effect of different phototherapy lights on retinal and choroidal blood flow.

The response of retinal (RBF) and choroidal (ChBF) blood flow to illumination with light with different spectra was investigated in spontaneously breathing newborn piglets. After 1 h in complete darkness, the animals were exposed to blue, white or green light in such a manner that equal energy was delivered to the eye. RBF and ChBF showed different flow responses. After 60 min exposure to blue light, RBF increased from 0.22 +/- 0.01 ml/min/g at baseline to 0.32 +/- 0.03 ml/min/g (+/- SEM) (p less than 0.03). Apart from this increase, RBF did not change significantly during any of the experimental settings. ChBF, on the other hand, was significantly affected by illumination. Thus, at 120 min of light exposure all three types of light decreased ChBF significantly from baseline (darkness) levels. Blue light decreased ChBF (mean +/- SEM) from 13.78 +/- 0.84 to 7.61 +/- 0.67 ml/min/g (p less than 0.01), white light from 17.43 +/- 1.86 to 9.86 +/- 1.07 ml/min/g (p less than 0.01), and green light from 14.13 +/- 1.64 to 8.31 +/- 1.30 ml/min/g (p less than 0.02). The results indicate that light is an important modulator of ChBF and to a certain extent also RBF. Further, the results suggest that ChBF and RBF are regulated differently.