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Biomedical subjects

C L Schepens

Publications and source records attributed to C L Schepens.

At least 91 records · Page 5Linked to original sources
PubMed1983

Vitreous floaters.

The vitreous changes in 148 eyes with sudden onset of floaters were evaluated biomicroscopically and documented photographically using an El Bayadi-Kajiura aspherical preset lens mounted on a photo slit lamp. Posterior vitreous detachment (PVD) was found in 83% of the eyes. In those eyes, the primary causes of floaters were prepapillary glial tissue on the posterior hyaloid membrane and minimal vitreous hemorrhage. In eyes with no PVD, intravitreous fiber-like opacities corresponding to the patient's symptoms were present in the posterior vitreous cavity near the retina. These opacities were found on the plicated membranes of Cloquet's canal, or were associated with liquefaction of the gel. The symptoms of patients 50 years of age or older were related to the acute onset of PVD in 95% of the cases. The complaint of multiple small floaters was frequently associated with vitreous hemorrhage and retinal breaks.

Adult↗
PubMed1983

Ultrasonographic findings in eyes with giant retinal tears and opaque media.

A preoperative diagnosis of giant retinal tear was suspected as a result of ultrasonography in six eyes with opaque media, and the diagnosis was then confirmed during surgery. All eyes showed a discontinuity in the high amplitude linear retinal echo, representing the location of a retinal tear involving more than one retinal quadrant. In five eyes there was a double linear echo attached to the optic nerve. The linear echo that was discontinuous with the contour of the globe corresponded to the inverted posterior flap of the giant retinal tear. The linear echo that was continuous with the contour of the globe represented detached retina. The preoperative discovery of a giant retinal tear by ultrasonography in eyes with opaque media influences the subsequent management of the patient.

Adult↗
PubMed1983

Characterization of membranes removed during open-sky vitrectomy.

Membranes removed during open-sky vitrectomy have been characterized by electron microscopy, reaction with anti-human fibrinogen, susceptibility to enzymatic digestion, amino acid analysis, and electrophoresis in sodium dodecyl sulfate. There were significant differences between longstanding and newly formed membranes. Longstanding membranes contained substantial amounts of hydroxyproline, glycine, and hydroxylysine, were capable of digestion by collagenase but not by plasmin, yielded faint positive results with anti-human fibrinogen, and showed fibrils characteristic of collagen by electron microscopy. After digestion with pepsin, electrophoresis revealed bands that migrated the same distance as vitreous collagen chains. This type of membrane is evidently collagenous in nature. A second type of membrane, which developed in the course of vitrectomy, contained no hydroxyproline, only traces of hydroxylysine, and relatively small amounts of glycine, was digested by plasmin, yielded strong positive results with anti-human fibrinogen, and showed fibers that were not characteristic of collagen by electron microscopy. Electrophoresis demonstrated bands similar to authentic fibrin in these newly formed membranes. These data suggest that this second type of membrane is composed largely of fibrin. Prevention of the formation of this second type of membrane during vitrectomy may require the addition of agents that inhibit fibrin formation.

Amino Acids↗
PubMed1983

Pathologic processing of vitrectomy specimens. A comparison of pathologic findings with celloidin bag and cytocentrifugation preparation of 102 vitrectomy specimens.

Specimens obtained from 102 vitrectomies were processed by cytocentrifugation and celloidin bag techniques. The histopathology obtained with each procedure was compared with respect to cellular and tissue findings. Forty-five percent of cases had identical findings by the two techniques. Quantitative analysis of the discrepancies revealed better cellular recovery and identification by cytocentrifugation, and similar rates for the recovery and identification of tissue elements. Qualitative analysis showed better demonstration of tissue histopathology using celloidin bag thin sections. Thus, pathologic analysis was more complete when the two techniques were used together than when either was used alone.

Centrifugation↗
PubMed1982

Macular photocoagulation. Optimal wavelength selection.

Relative merits of different laser wavelengths for macular photocoagulation are analyzed in terms of light scattering and light absorption in hemoglobin, melanin, and macular xanthophyll. Disadvantages of inner retinal damage in the macula caused by the blue-green argon photocoagulators in standard clinical use are discussed, along with advantages of argon green and krypton yellow light. Results of treatment of subretinal neovascularization in disciform macular degeneration are presented. A repetitive treatment, close follow-up protocol was employed with the objectives of closing neovasculature and preserving central visual field. In 74 successive patients treated with monochromatic argon green radiation, neovasculature was closed in 93%, central visual field loss was reduced or stabilized in 76%, and visual acuity was improved or stabilized in 70%. Results were analyzed in terms of location and size of the neovascular membrane, and it was found that best results were obtained with neovascularization farther than 600 microns from the foveola and smaller than 2 mm2. In 17 patients with neovascular membranes more than 600 microns from the foveola, neovasculature was closed in 100%, central visual field loss was reduced or stabilized in 94%, and visual acuity was improved or stabilized in 88%. Similar results were obtained with monochromatic krypton yellow radiation.

Humans↗
PubMed1982

A model for the pathogenesis of retrolental fibroplasia based on the metabolic control of blood vessel development.

We postulate that the pathogenesis of retrolental fibroplasia (RLF) is related to the disruption of the normally coordinated ocular development and maturation in which there is an interplay between function, metabolism, and blood vessel development. The normal retina is avascular until the fourth month of gestation, at which time vascularization proceeds from the optic disk towards the peripheral retina. Until this time, the underlying choroidal circulation provides for full-thickness retinal oxygenation. We hypothesize that the centrifugal maturation of the retina, including the retinal photoreceptors (the major oxygen-consuming cell type of the adult retina), precedes this vascular outgrowth. The maturation of the photoreceptors and the concomitant increased oxygen consumption would make it impossible for the choroid to provide adequate full-thickness retinal oxygenation. The resulting progressive change in the inner retinal metabolism thus provides an orderly, controlled stimulus for the subsequent progression of retinal vascularization from the optic disk to the peripheral retina. Exposure of the premature neonate to abnormal oxygen levels would selectively retard inner retinal blood vessel development while the photoreceptors continue to mature and increase their oxygen consumption. Thus, when the infant is removed from abnormal oxygen, a neovascular proliferative stimulus will develop in direct relation to the mass of non-vascularized but metabolically active retina, initiating uncoordinated vessel growth in the inner retina.

Fetus↗
PubMed1981

Biomicroscopic evaluation and photography of liquefied vitreous in some vitreoretinal disorders.

The vitreous condition in retinitis pigmentosa, high myopia, peripheral uveitis, and Wagner's disease and in normal eyes was evaluated biomicroscopically and documented photographically using a present lens (El Bayadi-Kajiura) in 205 eyes. Compared with the control group, the incidence of partial or complete vitreous detachment was significantly higher in all four clinical entities and partial vitreous detachment was more frequently found in Wagner's disease, high myopia, and peripheral uveitis, but not in retinitis pigmentosa. A higher incidence of cottonball-like opacities and/or spindle-shaped condensations in the posterior vitreous near the retina was found in retinitis pigmentosa and high myopia than in peripheral uveitis or Wagner's disease. This finding suggests that the vitreous changes seen in retinitis pigmentosa and high myopia are secondary to chorioretinal degeneration.

Adolescent↗
PubMed1981

Clinical and research aspects of subtotal open-sky vitrectomy. XXXVII Edward Jackson Memorial Lecture.

Subtotal open-sky vitrectomy can be used to improve visual function in some eyes for which closed vitrectomy is useless. Open-sky vitrectomy allows easier access for surgical instruments, especially to anterior fundus structures. The technique also improves the visibility of intraocular structures. The surgical procedure, which uses special instruments and high-molecular-weight hyaluronic acid, is divided into four stages: preparation, operating inside the vitreous cavity, wound closure, and retinal reattachment. In 290 consecutive operations for which complete follow-up data are available, retinal reattachment was achieved in 61 eyes (21%). The greatest number of successes (16 of 30 cases [53%]) was achieved in severe tractional retinal detachments. Such results are encouraging because these eyes were considered inoperable by other techniques. Open-sky vitreous surgery is performed through a corneal incision, but a scleral incision over the pars plana may become the method of choice in selected cases. The development of a preretinal fibrin membrane, as a result of either a closed vitrectomy or an open-sky procedure, may be a major cause of postoperative failure. Hypotony during surgery is probably the main precipitating factor of intraocular fibrin membrane formation.

Adolescent↗
PubMed1981

Subtotal open-sky vitrectomy for severe retinal detachment occurring as a late complication of ocular trauma.

Subtotal open-sky vitrectomy was performed on 50 eyes with severe retinal detachment that developed as a late complication of ocular trauma. The retina was reattached in 32% of the eyes and vision was improved in 50% of the reattached cases. Two cases of giant retinal tear with massive preretinal retraction were successfully treated by suturing the retinal flap of the tear to the choroid. Subtotal open-sky vitrectomy may be helpful in cases in which closed vitrectomy has failed or would be likely to fail.

Adult↗
PubMed1981

Automated variable contrast acuity testing.

The results of clinical trials with a simple system for automating visual acuity measurements are presented. An inexpensive microcomputer: (1) presents acuity targets on a television screen, (2) uses patients' responses entered through a remote response box to control a staircase testing procedure, and (3) prepares a printed record of a patient's mean visual acuity and its standard deviation. The automated method: (1) offers a stable measure of visual performance, (2) provides an immediate analysis of the statistical significance of changes measured in visual acuity from one office visit to the next, and (3) gives results that are in general agreement with conventional chart testing methods when high contrast targets are used on the television screen. In addition, when medium and low contrast targets are used, the automated method provides a variable contrast acuity profile (VCAP), which describes visual performance at contrast levels that are vital to a patient's performance in daily life but not examined in conventional chart testing. VCAPs are measured clinically, and it is shown that the extent that a patient's acuity declines with decreasing contrast cannot be predicted from the patient's high contrast acuity. Automated variable contrast acuity testing is found to provide a simple, reproducible, clinically practicable method of documenting and quantitating the extent of a patient's visual difficulties at medium and low contrasts.

Adolescent↗
PubMed1981

A hydrophilic acrylate implant for scleral buckling: technique and clinical experience.

A new hydrophilic acrylate implant developed for scleral buckling was used in 51 patients: as an accessory meridional piece under a solid silicone buckle in 25 and as a main buckling element in 26 (intrasclerally in 15 and episclerally in 11). Clinical observations six to 18 months after implantation showed the implants to be well tolerated in all cases. There was no infection, rejection, extrusion of the implant, or erosion of the eye coats. In two patients who had reoperations, smooth fibrous tissue encapsulating the implant including the scleral bed was present. Our observations indicate that this new material has all the characteristics of an ideal implant for scleral buckling.

Acrylates↗
PubMed1981

New Cataract removal instrumentation and techniques: i. the NASA-McGannon cataract fragmentor.

The instrument consists of a high-speed air turbine driven cutter combined with a pressure-regulated infusion system and a peristaltic pump evacuation system. The tool has an exposure control to vary the axial position of the cutter relative to its housing. The entire unit is controlled and powered by compressed air. A foot pedal start and stops all suction and cutting functions. The intraocular pressure is controlled by a flow-compensating pressure regulator that balances out the inflow system pressure drop and thereby provides essentially constant intraocular pressure.

Cataract Extraction↗
PubMed1981

New Cataract removal instrumentation and techniques: ii. laboratory phacofragmentation with the NASA-McGannon cataract fragmentor.

The NASA-McGannon cataract fragmentor, a newly designed mechanical phacofragmentor powered by compressed air, was tested on 100 eyes of old rabbits and on 50 dark brown nuclei of human cataracts that were implanted in the anterior chambers of rabbit eyes after the lenses had been removed. It was possible to eliminate the eddy current in the anterior chamber, reduce the requirement for infusion, and reduce the time of fragmentation both for rabbit lenses and for implanted hard nuclei of human cataracts. Iatrogenic damage to the iris and posterior capsule of the lens was noted in the early cases but not in the later ones, as the operators became more skillful in manipulating the instrument.

Animals↗
PubMed1980

Biomicroscopic evaluation and photography of posterior vitreous detachment.

This is a preliminary effort to demonstrate conditions of the posterior vitreous more objectively by slit-lamp photography. For this purpose, a + 58.6-diopter, aspherical, preset lens (El Bayadi-Kajiura lens [Nikon]) and a photoslit (Zeiss Jena) were used. The most fundamental aspect in our technique of observation and photography of the posterior vitreous is that of catching the appropriate moment during the vitreous movement that follows horizontal and/or vertical displacement of the patient's eye. Posterior vitreous photographs by this method in normal eyes, retinitis pigmentosa, Wagner's disease, and preretinal macular fibrosis associated with macular edema in phakic eyes are presented, and biomicroscopic characteristics in each of these diseases are discussed. Our observations clearly demonstrate a new technique for detailed examination and photography of the posterior vitreous.

Adult↗
PubMed1980

Retinal detachment following congenital cataract surgery. I. Preoperative findings in 114 eyes.

One hundred fourteen eyes of patients with retinal detachment occurring after congenital cataract surgery were studied. Retinal detachment was typified by high incidences of men, myopia, preference for the second and fourth decades of life, and a fairly long interval after cataract surgery. Frequently found were the following: (1) undetected retinal breaks, (2) high incidences of small oval or round holes in the upper nasal quadrant near the ora serrata, (3) retinal detachment in more than one quadrant, and (4) extensive vitreous and preretinal traction. Preoperative examination was often hampered by a small, bound-down pupil, nystagmus, extreme photophobia, and an inability to move the eye in desired directions. The major factor in the pathogenesis of retinal detachment after congenital cataract surgery appears to be chronic vitreoretinal traction in the anterior vitreous caused by cataract removal.

Adolescent↗