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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Graefe's archive for clinical and experimental ophthalmology 233 (1995), S. 226-230 
    ISSN: 1435-702X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract • Background: Lesions resembling those of human retinopathy of prematurity can be provoked in newborn Wistar rats by exposure to an FiO2 of 80% for the first 5 days of life followed by 5 days recovery under room-air conditions. • Methods: We evaluated the effects of moderate hyperbarism (+60.75 kPa, i.e. 455 mmHg or 0.6 atm) and topical administration of 0.25% timolol maleate on oxygen-induced retinopathy (OIR) in this experimental model. • Results: OIR (including neovascularization in most cases) was observed in 100% of the retinas of normobaric oxygen-reared ratlings that did not receive timolol. OIR was less frequent in oxygen-reared ratlings treated with hyperbarism (60%) or timolol (65%). Hyperbaric oxygen supplementation combined with timolol treatment during both the hyperoxic and room-air phases reduced the incidence of OIR to 30%. There was no sign of vasoproliferation in any of the retinas from the latter three groups. • Conclusions: The highly significant protective effects of hyperbarism and timolol observed in this study are not fully understood. We speculate that vasoconstriction induced by the hyperbarism reduces the amount of oxygen that reaches the retina from the choroid during O2 supplementation, while an increased ocular perfusion pressure caused by timolol-induced reduction of the intraocular pressure might decrease the stimulus to vasoproliferation that normally occurs with room-air recovery.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Graefe's archive for clinical and experimental ophthalmology 234 (1996), S. S38 
    ISSN: 1435-702X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract • Background: Technical advances in neonatal intensive care have significantly increased the number of very low birth-weight babies that survive the perinatal period. Some of these infants develop severe retinopathy of prematurity that may lead to retinal detachment. • Methods: Between November 1988 and January 1994, 28 eyes from 15 preterm babies underwent scleral buckling for stage 4 retinopathy of prematurity at a mean age of 4.2 months. Cryotherapy was performed preoperatively on 12 eyes and intraoperatively in the remaining 16 eyes. The mean follow-up period was 35 months. • Results: Scleral buckling produced retinal reattachment in 13 eyes (46.4%). Severe myopia (−5 D to −15 D) was found in all 13 of these eyes; 12 also presented convergent strabismus. Mean visual acuity, measured in 6 eyes from children over the age of 3 years was 20/40. In 7/28 eyes of the younger children of this group we found a fix and follow the light capability. No light perception was detected in 11/28 eyes; in the remaining 4/28 eyes there was only light perception. Scleral buckling failed to prevent the progression to stage 5 in 15 eyes (53.6%). Additional surgery was excluded for 9 of these eyes based on ultrasonography findings; the other 6 eyes underwent vitrectomy, which led to macular reattachment in 4 cases. • Conclusions: Clinical experience shows that scleral buckling is not always capable of preventing progression of the disease to stage 5. Furthermore, even when the anatomic results of this procedure are good, the functional outcome is often complicated by severe visual impairment.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International ophthalmology 17 (1993), S. 55-56 
    ISSN: 1573-2630
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-2622
    Keywords: Oxygen-induced retinopathy ; retinopathy of prematurity ; oxygen ; retinal vasculature ; scoring system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The authors describe a scoring system they have developed for evaluating damage produced in the retinal vascular network of the newborn rat by exposure to oxygen. India ink-injected retinal flat mounts are used. The scoring system provides for division of the retina into three concentric zones with the optic disk as a center point. Each retinal quadrant is then examined for the presence of the following lesions of progressive severity: vaso-obliteration of the capillary network, loss of the periarteriolar capillary-free zone, newly formed capillary tufts. When more than one type of lesion is present in a quadrant, only the most severe lesion is considered. The numerical score corresponding to that lesion is then multiplied by the factor corresponding to the concentric zone in which the lesion lies to give the quadrant score. The total retinal score is represented by the sum of the four quadrant scores. This type of system, if adopted by other investigators, can facilitate precise and systematic description of the results of different experimental protocols.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-2622
    Keywords: Intraocular pressure ; oxygen-induced retinopathy ; rat ; retinopathy of prematurity ; timolol maleate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of timolol maleate on intraocular pressure (IOP) and the severity of retinopathy induced by exposure to 80% oxygen were studied in newborn Wistar rats. One drop of timolol maleate (0.25%) instilled in each eye twice a day for the first ten days of life substantially reduced intraocular pressure without significantly modifying arterial pressure. Forty percent of the ratlings treated in this way failed to develop oxygen-induced retinopathy (OIR) after exposure to 80% oxygen for the first five days of life; in the other 60% OIR was less severe than that seen in an identically oxygenated group that did not receive timolol. The authors hypothesize that the pharmacologically induced reduction in IOP may have attenuated the effects of the high concentrations of oxygen on the immature retinal vessels by improving the ocular perfusion pressure. The possibility that timolol maleate also exerts a direct action on the caliber of these vessels cannot be excluded.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-2622
    Keywords: axonal transport ; light ; oxygen ; oxygen-induced retinopathy ; retina ; retinopathy of prematurity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this study was to establish whether exposure to intense lighting favors the development or aggravates experimental oxygen-induced retinopathy in the new-born rat. Five groups of Wistar rats were studied. The control group was maintained for the first 14 days of life under conditions of cyclical (12L∶12D) lighting at 12 Lx in room air. Two other groups were subjected, for the same amount of time, to semi-darkness (2 Lx; 12L∶12D), one with room air and the other with supplemental 80% oxygen. The final two groups were exposed to the same room air and hyperoxic treatments under intense lighting conditions (600 Lx; 12L∶12D). After the treatment period, four rats were randomly chosen from each group, sacrificed and their retinas examined under electron microscope. Marked structural changes were seen only in the photoreceptor outer segments of those rats exposed to intense light. In eighty-five of the remaining rats retinal vascular morphology was examined in retinal flat mounts after intracardiac injection of India ink. Retinopathy was observed in rats treated with hyperoxia but no significant differences could be attributed to the light conditions under which the retinopathic rats had been maintained. In the rest of the rats, axonal transport along the optical pathways was evaluated after intravitreal injection of (3H) taurine. In the two groups exposed to hyperoxia, axonal transport was altered, but less markedly in those exposed to intense lighting than in those exposed to semi-darnkess. Intense illumination under conditions of normoxia favors axonal transport. Exposure to intense lighting does not seem to aggravate oxygen induced retinopathy in the rat though it does produce structural lesions of the photoreceptors.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Documenta ophthalmologica 87 (1994), S. 315-329 
    ISSN: 1573-2622
    Keywords: Experimental retinal detachment ; Glial fibrillary acidic protein ; Müller cells ; Oxygen ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We conducted an extensive histological study of the retinas of newborn rats that had been exposed to hyperoxic conditions. Our aim was to verify whether it is possible, using oxygen alone, to induce retinal detachment, a lesion that is characteristic of the more advanced stages of retinopathy of prematurity (ROP). Eight litters (total number of animals: 64) of newborn, albino Wistar rats were used. Four litters (32 rats) were exposed to 80% oxygen for the first ten days of life. Some of these rats were then removed to room-air environments where they were kept for two, three or four more weeks. The other four litters (32 rats) were maintained for the entire period in room-air. On the 11th, 25th, 32nd and 39th days of life rats from both the exposed and control groups were sacrificed and 5 micron sections of their in toto eyeballs were submitted to histological evaluation and immunohistochemical studies. Folding of the internal retinal layers was observed in some of the animals exposed to hyperoxia, as well as those kept in room air. These folds did not alter the overall thickness of the retina itself and were probably congenital. Retinal folds and microdetachments were seen in many of the retinas from the exposed group of rats. Extensive detachment was observed in one of the rats sacrificed after two weeks of room-air recovery, in two of those recovered for three weeks and in two exposed to four weeks of room air. The sections containing these areas of retinal detachment showed marked increases in glial fibrillary acidic protein (GFAP) in immunocytochemical studies, suggesting that Müller cells might play a role in the pathogenesis of retinal detachment.
    Type of Medium: Electronic Resource
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