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Biomedical subjects

G O Waring

Publications and source records attributed to G O Waring.

At least 19 recordsLinked to original sources
PubMed1992

Subepithelial fibrosis after myopic epikeratoplasty. Report of a case.

A 29-year-old man with a -22.00-diopter myopia in the right eye underwent a planar, nonfreeze myopic epikeratoplasty and postoperatively developed a central subepithelial opacity. The opacity recurred after two superficial keratectomies; finally, another epikeratoplasty was performed. Light microscopic examination of the original button showed that the epithelium was thickened, collagenous subepithelial fibrocellular tissue was present, and Bowman's layer was focally disrupted. The stroma was edematous and peripherally scarred with scattered keratocytes. Examination by transmission electron microscopy revealed keratocytes lying anterior and posterior to Bowman's layer. The subepithelial fibrocellular tissue corresponded to an area of a break in Bowman's layer and probably originated from the donor stroma. The break in Bowman's layer may have been caused by the microkeratome cuts, but its origin is not certain.

Adult↗
PubMed1992

Corneal wound healing in monkeys after repeated excimer laser photorefractive keratectomy.

Five rhesus monkey eyes underwent repeated argon fluoride (193 nm) excimer laser myopic photorefractive keratectomy 3 months following an initial ablation that had produced mild subepithelial haze. At 3 months all eyes had development of a dense subepithelial opacity and a thickened epithelium (12 cells, 80 microns) with vacuolization of basal cells, fragmented basement membrane, and a layer of subepithelial fibrosis containing activated fibroblasts. By 6 months the opacity was clearing; epithelium was thinner (50 microns); subepithelial fibrosis was more lamellar. By 15 months only mild haze persisted clinically; epithelium was 30 microns thick, with persistent basal vacuolization and focal basement membrane disruption; subepithelial fibrous tissue was more organized. Early repeated excimer laser ablation of the monkey cornea apparently induces vigorous stromal wound healing. Use of shallower ablations, corticosteroids, or a longer delay between ablations may be necessary for repeated laser surgery to be practical clinically.

Animals↗
PubMed1992

Penetrating keratoplasty in patients with rheumatoid arthritis.

The authors reviewed in a retrospective manner 47 penetrating keratoplasties performed on 23 eyes of 21 patients with rheumatoid arthritis. The indications for the first penetrating keratoplasty were corneal melt in 19 eyes (83%), infectious keratitis in 2 eyes (9%), and corneal scarring after ulceration in 2 eyes (9%). Twelve of the 23 eyes required 24 repeat penetrating keratoplasties. Seventeen of the 23 eyes (74%) had clear grafts at the last follow-up visit, a median of 13.7 months after the last penetrating keratoplasty. The final best corrected visual acuity was greater than or equal to 20/60 in 4 eyes (17%), 20/70 to 20/100 in 1 eye (4%), 20/200 to 20/400 in 7 eyes (30%), counting fingers in 4 eyes (17%), hand motions in 2 eyes (9%), and light perception in 4 eyes (17%). One eye (4%) was enucleated. Anatomic success (absence of phthisis bulbi, enucleation, or conjunctival flap) was achieved in 20 eyes (87%). The survival probability for the 21 patients was only 48% 5 years after the first penetrating keratoplasty. The authors conclude that penetrating keratoplasty is often anatomically successful in patients with rheumatoid arthritis; however, the prognosis is poor for both vision and survival of the patient.

Adult↗
PubMed1992

Mycobacterium gordonae keratitis.

A 20-year-old man was evaluated for an indolent corneal ulcer. Tissue and cultures from a penetrating keratoplasty indicated that the causative agent was Mycobacterium gordonae. This is the third patient reported with M. gordonae keratitis, although there have been numerous reports of nontuberculous mycobacterial keratitis. Nontuberculous mycobacterial keratitis is typically associated with previous trauma. The patient reported here had no known predisposing factor.

Adult↗
PubMed1992

Cytokeratin expression in corneal endothelium in the iridocorneal endothelial syndrome.

The immunocytologic characteristics of two formalin-fixed, paraffin-embedded corneas from patients with the iridocorneal endothelial (ICE) syndrome and unaffected control corneas were studied. Binding of polyclonal antisera to Factor VIII, S-100 protein, involucrin, neuron specific enolase (NSE), and the lectins peanut agglutinin and Ulex europaeus agglutinin-1 was performed using the standard peroxidase-anti-peroxidase method. We detected reactive patterns of monoclonal antibodies to cytokeratins (34BE12 is a 56-58 kD mouse IgG reactive to stratified epithelia; Pkk1 is a 44-54 kD mouse IgG reactive to simple epithelia; and KL1 is a 55-57 kD mouse IgG reactive to epidermis and simple epithelia) using the standard avidin-biotin complex method. Staining properties were similar for the polyclonal antisera, lectins, NSE, and chromogranin in corneas with ICE syndrome and in the controls. However, the cytokeratins 34BE12, Pkk1, and KL1 were detected in the endothelium of the corneas with the ICE syndrome but not in the controls. These findings suggest that various cytokeratins are expressed in the corneal endothelium in the ICE syndrome that are not expressed in unaffected corneal endothelium.

Antibodies, Monoclonal↗
PubMed1991

Stability of refraction during four years after radial keratotomy in the prospective evaluation of radial keratotomy study.

The Prospective Evaluation of Radial Keratotomy Study is a nine-center clinical trial of a standardized technique of radial keratotomy in 435 patients who had simple myopia with a preoperative refraction between -2.00 and -8.00 diopters. We studied the stability of the refractive error during four years after surgery for each of 341 eyes first operated on that had a single surgical procedure. Between baseline and two weeks after surgery, all eyes became less myopic; between two weeks and three months, 161 eyes (59%) lost 1.00 D or more of the initial effect; and between three and six months, 266 eyes (95%) had a stable refraction with less than 1.00 D change. The change from six months to four years was less than 1.00 D for 246 eyes (72%). There was 1.00 D or more decrease in surgical effect (increased minus power) for 13 eyes (4%), and 1.00 D or more increase in surgical effect (decreased minus power) for 82 eyes (24%). Eyes with larger amounts of preoperative myopia and smaller diameter of the clear zone were more likely to have an increasing effect of the surgery. The duration of this continued increasing effect of the surgery is unknown.

Adult↗
PubMed1991

The relationship of visual acuity, refractive error, and pupil size after radial keratotomy.

To better define the relationship between residual refractive error, uncorrected visual acuity, and pupil diameter, we compared 42 eyes that had an eight-incision radial keratotomy according to the Prospective Evaluation of Radial Keratotomy Study protocol with 42 matched control eyes. The parameters measured were best corrected visual acuity, uncorrected visual acuity, and the change in cycloplegic refraction with enlarging pupil diameter. The best corrected visual acuity was 20/16 in both the radial keratotomy and control groups, but the variability (SD) was higher in the radial keratotomy group. The average uncorrected visual acuity was 0.35 (35%) better in the radial keratotomy group, but the variability was 1.77 times higher. Change in refraction with dilation occurred in 9% of the controls and 36% of the radial keratotomy patients, indicating a significant difference (P = .002). The change in refraction with dilation in the eyes with radial keratotomy was almost equally split between a hyperopic change (17%) and a myopic change (18%), which was much different than in the control eyes, only 2% of which changed in a hyperopic direction and 7% in a myopic direction. The radial keratotomy patients with a myopic change had the best uncorrected visual acuity, indicating that positive spherical aberration yielded the best aspherical surface for uncorrected visual acuity.

Adult↗
PubMed1991

Computer-assisted videokeratography of corneal topography after radial keratotomy.

We used computer-assisted videokeratography to compare the topographies of 32 corneas from 23 subjects after radial keratotomy with those of 47 normal corneas from 47 subjects controlled for age and preoperative keratometric and refractive power. Three ophthalmologists independently classified color-coded videokeratographs based on the color-coded pattern of dioptric power distribution and the cross-sectional shape. Corneas that had radial keratotomy exhibited a polygonal pattern not seen in normal eyes; this occurred in 59% of corneas. All normal corneas demonstrated a cross-sectional shape configuration that was steeper centrally than peripherally; 79% of corneas after radial keratotomy had a shape that was flatter centrally than peripherally. After radial keratotomy, the dioptric power increased from the center to the periphery (radius of approximately 4.6 mm) by 2.8 +/- 2.2 diopters (mean +/- SD), with a sharp inflection zone ("paracentral knee") 2.7 mm from the center; normal corneas showed a smooth decrease in power from the center to the periphery of 1.9 +/- 0.5 diopters.

Adult↗
PubMed1991

Trapezoidal keratotomy for the correction of naturally occurring astigmatism.

We performed trapezoidal keratotomy, consisting of combined nonintersecting semiradial and transverse incisions, in 64 eyes of 45 consecutive patients with naturally occurring astigmatism. The central clear zone diameter and number and length of transverse incisions were determined by the refractive error. Mean preoperative refractive astigmatism was 3.18 +/- 1.16 diopters (D) (range, 2.25 to 7.00 D). At the 1-year follow-up examination, the mean surgically corrected astigmatism determined by vector analysis was 3.70 +/- 1.50 D (range, 0.75 to 8.5 D), and the mean residual refractive astigmatism was 0.85 +/- 0.72 D (range, 0 to 4.0 D), with 64% of eyes having 1.00 D or less. The smaller the clear zone diameter, the greater the astigmatic correction. Longer transverse incisions produced more steepening of the secondary meridian. The operative complications included microperforation (5%), misalignment of surgical meridian (6%), encroachment on clear zone (5%), and inadvertent crossed incisions (11%). Trapezoidal keratotomy reduced naturally occurring astigmatism, but with only fair predictability and with some irregular astigmatism due to irregular wound healing.

Adolescent↗
PubMed1991

Solid state ultraviolet laser (213 nm) ablation of the cornea and synthetic collagen lenticules.

We used a Q-switched Nd:YAG laser with non-linear optical crystals to produce the 5th (213 nm) and the 4th (266 nm) harmonic frequencies. Using these two wavelengths, we ablated fresh porcine corneas and type I collagen synthetic epikeratoplasty lenticules. For the 213-nm ablation, radiant exposure was 1.3 J/cm2. The ablation rate was 0.23 micron per pulse for the epikeratoplasty lenticules. We examined all tissues with light microscopy, transmission electron microscopy, and scanning electron microscopy. Histology for the 213-nm ablation showed a clean ablation crater with minimal collagen lamellae disruption and a damage zone less than 1 micron. In comparison, the 266 nm radiation showed more charring at the edges with a damage zone approximately 25 microns deep with disruption of the stromal lamella. Our results show that this solid state UV laser is a potential alternative to the excimer laser for cornea surgery.

Aluminum Silicates↗
PubMed1991

Results of the Prospective Evaluation of Radial Keratotomy (PERK) Study five years after surgery. The Perk Study Group.

In the Prospective Evaluation of Radial Keratotomy (PERK) Study, 793 eyes of 435 patients with 2 to 8 diopters (D) of myopia received a standardized surgery consisting of 8 incisions with a diamond-bladed knife set at 100% of the thinnest paracentral ultrasonic corneal thickness measurement and a diameter of the clear zone of 3.0 to 4.5 mm; 97 eyes (12%) received an additional 8 incisions. There were 757 eyes (95%) followed for 3 to 6.3 years. After surgery, uncorrected visual acuity was 20/40 or better in 88% of eyes. The refractive error was within 1 D of emmetropia for 64% of eyes; 19% were myopic and 17% were hyperopic by more than 1 D. Between 6 months and 5 years after surgery, 22% of the eyes had a refractive change of 1 D or more in the hyperopic direction. For 25 eyes (3%) there was a loss of 2 or more lines of best spectacle-corrected visual acuity.

Adult↗
PubMed1991

Lack of association between keratoconus, mitral valve prolapse, and joint hypermobility.

The authors enrolled 95 patients with keratoconus and 96 matched controls in a cross-sectional study to determine if mitral valve prolapse and hypermobile joints occur with greater frequency in individuals with keratoconus than in individuals without keratoconus. The hypothesis that keratoconus may not be a distinct eye disease, but a nonspecific sign representing a more generalized systemic disorder, possibly a mild collagen tissue abnormality, was considered. M-mode and two dimensional echocardiography and cardiac auscultation detected no statistically significant difference in the prevalence of mitral valve prolapse in patients with keratoconus compared with controls. Formal, systematic examination of five joints also failed to detect a statistically significant difference in the prevalence of hypermobile joints in keratoconus patients and controls. However, as an ancillary finding, a significantly higher proportion of patients with keratoconus was found to have a history of hay fever than was the case with controls.

Adult↗
PubMed1991

Corneal topography as a predictor of refractive change in the prospective evaluation of radial keratotomy (PERK) study.

The first operated eyes of 435 patients undergoing radial keratotomy in the Prospective Evaluation of Radial Keratotomy (PERK) study were evaluated by photokeratography to document the preoperative and postoperative corneal shape. We determined by regression analysis and analysis of variance that the corneal shape preoperatively improved the prediction of the corneal shape 6 months postoperatively in the 3-mm-clear-zone population. The reduction of myopia in all 435 eyes ranged from 1.25 to 9.75 diopters. We studied the effect of the preoperative corneal shape on this variability in the outcome of the surgery using rings 2 and 7 on photokeratography and corneal diameter. In the 3-mm-clear-zone group, eyes with flat prolate corneas had a greater reduction in myopia (4.65 D); those with steeper, more spherical corneas had less reduction in myopia (3.48 D). In addition, eyes with a 3-mm clear zone and flat central corneas alone (8.0 mm = 42.19 D) flattened approximately 0.75 D more than those with steep central corneas (7.0 mm = 48.21 D). In the 3.5-mm and 4.0-mm clear zone groups, the change in corneal curvature was not related to the preoperative curvature. A stepwise regression analysis of the 151 eyes in the 3.0-mm-clear-zone population demonstrated the following predictive equation for radial keratotomy; change in cycloplegic refraction = -14.55 + [-2.097 x average ring-2 radius] + [3.605 x average ring-7 radius] + [0.69 x horizontal corneal diameter] + [0.079 x age] + [-0.379 x spherical equivalent cycloplegic refraction]. There was a 1.17-D observed difference in the effect of radial keratotomy between those eyes with a steep/steep corneal topography (7.2% of the 3.0-mm-clear-zone population) and the flat/flat topography (29% of the 3.0-mm-clear-zone PERK population). A knowledge of corneal topography provides an additional tool for understanding the operative variability of radial keratotomy.

Cornea↗