ABSTRACT
BACKGROUND: At the present time, positive, wide-angle contact (and preset) lenses, having a large field of view, are widely used for inspecting and irradiating the fundus. They provide a real, inverted image of the fundus, but illuminate only the slit projected. The wide-field they provide (125 degrees ) is considered to be an advantage, but their image inversion and the lack of illumination of the whole field is disadvantageous. Contact lenses of the Goldmann type have a comparably restricted field of view (standard Goldmann: 46 degrees, CGR 3: 53 degrees). They illuminate the whole field inspected, but it is necessary to use internal mirrors when looking at the periphery. MATERIAL: The new contact lens has a lateral magnification of 0.44 and a field of view of 64 degrees. Owing to the prismatics of its biconcave structure, the field of view may be shifted by tilting the lens and/or by induced eye movements, beyond the ora serrata. CONCLUSIONS: The new contact lens CGR4 has an upright field of view of 64 degrees and tilting enables one to reach the equator with very little optical image degradation. The new lens has a negative power of - 139 dioptres. Safety during laser irradiation tasks is increased as compared to positive lenses because the irradiance at the crystalline part is significantly reduced. The lens is made of laser-resistant glass with a refractive index of 1,516 BK 7 (Schott).
Subject(s)
Contact Lenses , Laser Coagulation/instrumentation , Ophthalmoscopes , Retinal Vessels/pathology , Retinal Vessels/surgery , Computer-Aided Design , Equipment Design , Equipment Failure Analysis , Humans , Laser Coagulation/methods , Ophthalmologic Surgical Procedures/instrumentation , Ophthalmologic Surgical Procedures/methodsABSTRACT
PURPOSE: To determine whether blue light induces photoreversal of rhodopsin bleaching in vivo. METHODS: Eyes of anesthetized albino rats were exposed to either green (550 nm) or deep blue (403 nm) light, and the time course of rhodopsin bleaching was determined. Rhodopsin was isolated from whole retinas by detergent extraction and measured photometrically. To inhibit photoreversal of bleaching, rats were perfused with 70 mM hydroxylamine (NH(2)OH), a known inhibitor of photoreversal. To determine whether blue-absorbing, photoreversible photoproducts were formed, rhodopsin was bleached to near completion with green light and then exposed to blue light. Finally, experimental results were simulated on a computer by means of a simple, three-component model involving a long-lived photoreversible photoproduct. RESULTS: Photoreversal of bleaching in blue light occurs in vivo as evidenced by the following: In the absence of NH(2)OH, bleaching of rhodopsin by blue light was slow and complex. In the presence of NH(2)OH, however, blue light bleached rhodopsin very fast with a simple, pseudo-first-order kinetic. A long-lived bleaching intermediate produced by green light exposure was photoreversed to rhodopsin by exposure to blue light. The three-component computer model, invoking a blue-absorbing, photoreversible, long-lived intermediate accurately described the data. CONCLUSIONS: Because of the instantaneous, nonmetabolic regeneration of rhodopsin by the process of photoreversal of bleaching, blue light exposure permits the absorption of large numbers of photons by rhodopsin and by a photoreversible intermediate of bleaching in vivo. These data may have an important impact on resolving mechanisms of blue light-mediated damage to the retina.
Subject(s)
Light , Photoreceptor Cells, Vertebrate/physiology , Retinal Pigments/physiology , Rhodopsin/physiology , Rhodopsin/radiation effects , Animals , Computer Simulation , Hydroxylamine/pharmacology , Male , Photoreceptor Cells, Vertebrate/drug effects , Photoreceptor Cells, Vertebrate/radiation effects , Rats , Rats, Sprague-Dawley , RegenerationABSTRACT
BACKGROUND: Endoscopes play a more and more important role in visualizing and treating pathologies of the lacrimal drainage system. The present study analyzes the results obtained during endoscopy of the lacrimal ducts using a gradient-index (GRIN-) endoscope. PATIENTS AND METHODS: 44 patients, 18 to 87 years old (mean 59 years +/- 18.9), with chronic epiphora or symptoms of affection within the lacrimal ducts were examined using a rigid gradient-index (GRIN-) endoscope. Examination was performed ambulatory using drops for local anesthesia. RESULTS: All 44 patients showed pathologic conditions in the lacrimal drainage system. 2 patients had chronic changes. 25 patients had a relative stenosis (16 presaccal, 9 postcanalicular ones). 17 patients had a total stenosis (12 presaccal, 5 postcanalicular ones). 33 patients showed a single-sided pathology while 11 patients showed a bilateral one. The GRIN-endoscope could be used in all patients and gave excellent image quality of the pathologies. CONCLUSIONS: Endoscopy with a GRIN-endoscope can complement the ambulatory diagnostics and therapy of the lacrimal drainage system. In the patient group studied (n = 44), presaccal pathologies (n = 28) were twice more frequent than postcanalicular ones (n = 14). Further developments could enlarge the indications of the GRIN-endoscope.
Subject(s)
Endoscopes , Lacrimal Duct Obstruction/diagnosis , Nasolacrimal Duct/pathology , Adolescent , Adult , Aged , Aged, 80 and over , Equipment Design , Female , Humans , Lacrimal Duct Obstruction/pathology , Male , Middle AgedABSTRACT
BACKGROUND: Using small endoscopes it is now possible to evaluate the status of lacrimal ducts in vivo. GRIN-Lenses produce better pictures from the lacrimal ways than fiber-bundles. GRIN-endoscopes are rigid. The present study is concerned with the feasibility and indications of such GRIN-endoscopic examination. PATIENTS AND METHODS: Two different GRIN-endoscopes with a distal diameter of 0.89 mm were used. One with a phi 0.5 mm optic and an additional working channel and another one with a phi 0.35 mm optic and two additional working channels. One channel each was used for injection of air or 0.9% NaCl. Either a laser fiber or another instrument (max phi 0.16 mm) could be introduced into the second channel. 44 patients in age between 18 and 87 with symptoms of epiphora or signs of chronic lacrimal way affections were examined. RESULTS: The presaccal lacrimal ducts could be clearly visualized in all patients. In case of presaccal stenosis, the examination of the lacrimal sac was not always possible. The endoscope used, based of GRIN-lenses, gave an excellent image quality. Endoscopy under local anesthesia was well tolerated by all the patients with affection of the lacrimal drainage system. Because this ambulant examination does not stress the patient too much, it could be repeated a number of times. Endoscopy under general narcosis could enlarge the application spectrum. This method can complement the ambulant diagnostics and therapy of the lacrimal drainage system.
