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Biomedical subjects

G O Waring

Publications and source records attributed to G O Waring.

At least 163 records · Page 9Linked to original sources
PubMed1984

Characterization of the Descemet's membrane/posterior collagenous layer isolated from Fuchs' endothelial dystrophy corneas.

The combined Descemet's membrane (DM) and posterior collagenous layer (PCL) of Fuchs' endothelial dystrophy corneas were isolated and characterized by biochemical and immunofluorescence methods. The amino acid composition of the Fuchs' DM-PCL was similar to age-matched normal Descemet's membranes (DM). As determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and 125I two-dimensional peptide mapping, normal DM and Fuchs' DM-PCL contained the same collagen types [type IV and endothelial cell (EC) collagen], but a slight discrepancy was seen in the electrophoretic mobility of some collagen chains. Immunofluorescence staining localized fibrinogen/fibrin to Fuchs' DM-PCL but not to normal DM. These data suggest that the appearance of 110 nm banded material in sheets and fusiform bundles characteristic of Fuchs' PCL is not due to the presence of a new (abnormal) collagen type but may represent altered assembly of collagen molecules, and that the fibrinolytic system may play a role in the degenerative process of Fuchs' endothelial dystrophy.

Amino Acids↗
PubMed1984

Penetrating keratoplasty in children.

Retrospectively studied were 91 patients, 14 years of age or less, who had 152 penetrating keratoplasties in 107 eyes, with an average follow-up of 30.1 months. Survival analysis showed the probability of obtaining a clear graft at one year to be 60 +/- 8% in 45 eyes with congenital opacities, 70 +/- 8% in 31 eyes with opacities from trauma and 73 +/- 8% in 31 eyes with acquired nontraumatic opacities. Most failures occurred during the first postoperative year and were characterized by the gradual loss of graft clarity from undetermined cause. Twenty-nine percent (10) of the 34 eyes with congenital corneal opacities in which vision could be measured had a most recent visual acuity better than 6/120 (20/400). Irreversible amblyopia, glaucoma, other structural abnormalities of the anterior segment and mental retardation complicated visual rehabilitation in the congenital group. In the post-traumatic group, vision was better than 6/120 (20/400) in 45% (13) of 29 eyes, being limited by vitreoretinal pathology, fibrous ingrowth, and optic nerve damage from glaucoma. Visual acuity in the acquired, nontraumatic group was better than 6/120 (20/400) in 67% (20) of 30 eyes. The percentage of patients achieving 6/12 (20/40) or better in the congenital, post-traumatic, and nontraumatic groups were 3% (1/34), 17% (5/29), and 47% (14/30), respectively. In the congenital group, only patients with posterior polymorphous dystrophy obtained a visual acuity of 6/30 (20/100) or better. Preoperative vascularization of the cornea, persistent epithelial defects, and performance of lensectomy-vitrectomy were factors most highly correlated with poor graft survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Results of penetrating keratoplasty for pseudophakic corneal edema with retention of intraocular lens.

We reviewed the records of 26 consecutive patients undergoing penetrating keratoplasty for pseudophakic corneal edema in which the original intraocular lens was retained. The average interval between lens implantation and penetrating keratoplasty was 31.5 months. Follow-up after keratoplasty ranged from 11 to 59 months, with an average of 24.5 months. Six patients had anterior chamber lenses; sixteen, iris or iridocapsular lenses; and four, posterior chamber lenses. A vitrectomy was performed in 14 (54%) patients. Of the 21 patients with clear grafts (80%), 8 (38%) had vision of 20/40 or better while 7 (33%) had acuities of 20/200 or worse. Visual acuity of 20/40 or better was attained by 3 of 4 (75%) patients with posterior chamber lenses but only 3 of 16 (19%) patients with iris-supported lenses. Cystoid macular edema was the principal cause of decreased acuity in 12 of the 13 patients with clear grafts and acuity less than 20/40. Angiographic confirmation was obtained in 7 of 12 patients. Overall, the results are similar to those reported for pseudophakic keratoplasty with intraocular lens removal. No adverse effect of retaining a securely fixated intraocular lens was demonstrated.

Cataract Extraction↗
PubMed1984

Corneal ulcer due to Achromobacter xylosoxidans.

We report a case of corneal ulcer caused by the opportunistic organism Achromobacter xylosoxidans which developed during chronic topical steroid treatment of an eye with neovascular glaucoma. A. xylosoxidans has probably been underreported as a cause of ocular infection because of confusion between this organism and other Gram-negative organisms, particularly pseudomonas. A. xylosoxidans is resistant to aminoglycosides and some cephalosporins but not carbenicillin. This difference in antibiotic sensitivity patterns between A. xylosoxidans and pseudomonas makes an accurate differentiation between the 2 organisms important. This case was successfully treated after substituting topical carbenicillin for topical gentamicin and amikacin.

Administration, Topical↗
PubMed1983

Clinical specular microscopy of posterior polymorphous endothelial dystrophy.

By means of clinical specular microscopy in 27 patients with posterior polymorphous corneal endothelial dystrophy diagnosed by slit lamp examination and 26 relatives with normal findings by slit-lamp and specular microscopic examinations, we identified two clinical and specular microscopic patterns of posterior polymorphous dystrophy. (1) The localized vesicular or band pattern consisted of clear corneas with localized lesions resembling craters that were lined by abnormal cells and surrounded by enlarged, pleomorphic cells. (2) The geographic pattern was associated with Descemet's membrane haze and deep stromal haze, occasional peripheral iridocorneal adhesions, and glaucoma. By specular microscopy, this type had large, well circumscribed areas of abnormal pleomorphic cells with indistinct borders and increased reflective highlights. These areas were surrounded by normal-sized and smaller polygonal cells. The former cells appear to represent epithelial cells and the latter endothelial cells.

Adult↗
PubMed1983

Oval lipid corneal opacities in beagles: VI. Quantitation of excess stromal cholesterol and phospholipid.

We identified and quantitated the following lipids in corneas of normolipemic beagles that had oval corneal opacities: total lipids, cholesterol esters, free cholesterol, total phospholipids, phosphatidyl choline, phosphatidyl ethanolamine, sphingomyelin and total triacylglycerols. All except the total triacylglycerols were significantly higher in the 20 affected corneas than in ten normal age and sex-matched controls (P less than 0.005 for each). Few long-chain unsaturated fatty acids were detected. This lipid analysis and the previously reported natural history, ultrastructure, and histochemistry indicate that these opacities result from a primary disorder of corneal lipid metabolism that closely resembles central crystalline corneal dystrophy in man.

Animals↗
PubMed1983

Comparison of two methods of marking the visual axis on the cornea during radial keratotomy.

We compared two methods of marking the visual axis on the cornea during radial keratotomy surgery in 34 eyes of patients participating in the National Eye Institute Prospective Evaluation of Radial Keratotomy. The locations of the corneal light reflections produced by an optical centering device and by the operating microscope filament were identical in 18 eyes, overlapped partially or touched in ten eyes, and were separate in the remaining six eyes. The two corneal marks in this last group were close enough to make little practical difference. The two methods can be used interchangeably in clinical practice.

Cornea↗
PubMed1983

Rationale for and design of the National Eye Institute Prospective Evaluation of Radial Keratotomy (PERK) Study.

A five-year, multicenter, collaborative clinical trial of radial keratotomy for myopia is being carried out at nine clinical centers. The study, funded by the National Eye Institute, is recruiting approximately 500 patients aged 21 years or older with -2.00 to -8.00 diopters of physiologic myopia who also meet other clearly defined eligibility criteria. Surgeons use a diamond-bladed micrometer knife to make eight radial incisions in the anterior cornea. The diameter of the central clear zone is determined by the amount of myopia and the depth of the incisions by intraoperative ultrasonic pachymetry. Investigators other than the surgeon gather all pre- and post-operative data. Examinations include measurement of visual acuity with standardized charts, verification of refractions by a second observer, measurement of corneal curvature by keratometry and photokeratoscopy, quantitation of glare with a glare tester, and measurement of the size of individual endothelial cells from specular photomicrographs with a computerized digitizer. A formal psychometric questionnaire is used to evaluate the patients' subjective response. Physician monitors insure adherence to the protocol during site visits and members of the Data and Safety Monitoring Board oversee the progress of the study. Biostatisticians at the Coordinating Center insure complete data collection, process the data, and assist in the interpretation of results.

Academies and Institutes↗
PubMed1983

Results of penetrating keratoplasty in 123 eyes with pseudophakic or aphakic corneal edema.

The clinical records of 123 eyes that received a penetrating keratoplasty for aphakic or pseudophakic corneal edema with a mean follow-up time of 18 months were studied retrospectively. Thirty-five eyes from which an intraocular lens (IOL--85% iris fixated) was removed at the time of keratoplasty were compared with 88 eyes that never had an IOL. The mean interval between initial cataract surgery and penetrating keratoplasty was 28 months for the pseudophakic group from which the IOL was removed and 67 months for the aphakic group without IOL. In both groups, 97% had an anterior vitrectomy. Corneal grafts remained clear in 91% of the previously pseudophakic eyes and in 81% of the aphakic eyes (P less than or equal to 0.05). The final corrected visual acuity was worse in the pseudophakic eyes with IOL removed (16% saw 6/6 to 6/12 while 22% saw worse than 6/60) than in the aphakic eyes (34% saw 6/6 to 6/12 while 7% saw worse than 6/60). Postoperative maculopathy occurred in 43% of eyes from which IOLs were removed and in 22% of aphakic eyes.

Aged↗
PubMed1983

Sample size for estimating the quantiles of endothelial cell-area distribution.

The estimation of corneal endothelium mean cell area (and, hence, mean cell density) is an important problem in clinical ophthalmology. Mitotic division of these cells is not known to occur, and cell deaths are followed by the enlargement of adjacent cells. As a consequence, cell-area distributions change drastically as functions of age and disease. Changes in cell-area distributions, in particular multimodality and skewness due to aging, are observed, and give rise to some difficult sampling problems. In this paper, sample quantiles are investigated as an alternative to the use of the sample mean. Asymptotic approximations are provided for the sample sizes required to estimate population quantiles with a desired precision. Asymptotic sample sizes are then compared with those obtained from tolerance limits. Empirical sample quantiles that can be used as benchmarks to compare corneas of normal individuals against corneas with unknown cell-area distributions are also presented. Aspects that merit further investigation are noted.

Adolescent↗
PubMed1982

Posterior collagenous layer of the cornea. Ultrastructural classification of abnormal collagenous tissue posterior to Descemet's membrane in 30 cases.

We studied the transmission electron microscopy of the abnormal collagenous tissue posterior to Descemet's membrane in 30 human corneas that represented 19 different diseases. We named this abnormal tissue the "posterior collagenous layer" of the cornea and classified it into three morphologic types: (1) banded posterior collagenous layer, characterized by 110-nm wide-spacing material, (2) fibrillar posterior collagenous layer, characterized by loose meshwork of collagenous fibrils 20 to 30 nm in diameter, and (3) fibrocellular posterior collagenous layer, characterized by fibroblasts in connective tissue. The published ultrastructural studies of 88 corneas that represented 13 different clinical disorders fit this classification well. The posterior collagenous layers often formed multiple lamellae, but no pattern was invariably associated with a specific clinical disorder. We think these multiple layers represent successive periods of deposition of collagen by a stressed corneal endothelium and provide a lifelong record of senescent and pathologic events.

Adolescent↗
PubMed1982

Oval lipid corneal opacities in beagles.

Naturally occurring, oval opacities at the junction of the middle and inferior thirds of the cornea were found in an experimental beagle dog colony and were examined by light and electron microscopy. Abnormalities were limited to the anterior stroma and consisted of extracellular rhomboid crystalline spaces. Spherical or elliptical vacuolar spaces, sometimes containing electron-dense amorphous debris, distorted stromal lamellae. Stromal keratocytes in affected areas revealed a range of changes from hyperplasia of organelles to degeneration and necrosis.

Animals↗
PubMed1982

Isolation and characterization of fibronectin from bovine aqueous humor.

Aqueous humor collected from freshly enucleated bovine eyes was passed over a gelatin affinity column, and bound material was eluted with 4M urea. When fractionated by sodium dodecyl sulfate electrophoresis, the eluted material co-migrated with human plasma fibronectin and protein standards of approximately 220,000 daltons. Amino acid analyses demonstrated a composition similar to that of human plasma fibronectin and fibronectin synthesized by cultured cells. The concentration of fibronectin in aqueous humor is approximately 100 times less than in human plasma.

Amino Acids↗
PubMed1982

Oval lipid corneal opacities in beagles: ultrastructure of normal beagle cornea.

The ultrastructure of normal Beagle cornea was similar to the human cornea, except the Beagle lacked an anterior limiting lamina (Bowman's layer) and banding in the anterior portion of the posterior limiting lamina (Descemet's membrane). The epithelium was an average of 19 cells thick with 3 basic types: squamous, polygonal, and basal. The subepithelial stroma with a mean thickness of 9 microns was hypocellular, and the bundles of collagen were randomly oriented. The majority of the stroma consisted of closely packed, parallel collagen lamellae interspersed with keratocytes and occasional nerve fibers. The posterior limiting lamina was homogeneous and thick with increasing age. The endothelial cells formed a monolayer and had apical tight junctions.

Animals↗
PubMed1982

Use of Healon in anterior segment trauma.

Healon can assist in the repair of penetrating segment injuries by maintaining a deep anterior chamber that allows easier suturing of the wound and easier repositioning of the iris, by protecting the corneal endothelium during surgery, and by separating peripheral iridocorneal adhesions. We describe this technique in repair of an eye with a limbus-to-limbus corneal laceration.

Anterior Chamber↗
PubMed1982

The corneal endothelium. Normal and pathologic structure and function.

A summary of normal and abnormal endothelial structure and function is presented. Endothelium originates from neural crest and it elaborates a banded basement membrane in utero. It is involved in mesenchymal dysgenesis of the anterior segment, like the central defect of Peters' anomaly. Cytoplasmic organelles include mitochondria that provide energy for the metabolic pump, rough endoplasmic reticulum that participate in secretion of extracellular matrix, and a terminal web that may participate in cell migration. The endothelium's main function is to control corneal hydration and nutrition with a leaky barrier formed by the apical gap and macula occludens junctions that keep some water out of the stroma but allow nutrients to pass, and with an ATPase-dependent metabolic pump that is located in the lateral plasma membranes. Endothelial wound healing involves flattening and enlargement of cells to maintain an intact monolayer as well as production of abnormal collagenous material posterior to Descemet's membrane. HLA antigens located in the plasma membrane may participate in corneal endothelial graft rejection. Clinical assessment of the endothelium involves three modalities: specular microscopy to study endothelial morphology, fluorophotometry to measure barrier function, and pachymetry to measure corneal thickness.

Adolescent↗