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Biomedical subjects

J W Cowden

Publications and source records attributed to J W Cowden.

At least 19 recordsLinked to original sources
PubMed1998

Corneal topography in Ehlers-Danlos syndrome.

PURPOSE: To assess the use of corneal topography in conjunction with slitlamp biomicroscopy and retinoscopy to diagnose keratoconus in a large group of patients with Ehlers-Danlos syndrome (EDS). SETTING: Kresge Eye Institute, Wayne State University, Detroit, Michigan, USA. METHODS: Thirty-six patients (72 eyes) with genetically typed EDS had slitlamp biomicroscopy, retinoscopy, and videokeratography with the EyeSys instrument. The presence or absence of slitlamp keratoconus findings was correlated to a presumptive diagnosis based on corneal topography using derived topographic indexes associated with keratoconus. These topographic indexes included central corneal power, (CCP), difference in CCP, inferosuperior asymmetry (I-S) value, and asphericity (Q). Axial and profile difference maps were generated and analyzed for findings suggestive of keratoconus. RESULTS: In 72 eyes, no keratoconus was found using slitlamp biomicroscopy. No eye had an I-S value greater than 1.60 diopters (D), 2 eyes had a CCP greater than 46.50 D, and 2 eyes had a Q value less than -1.00. Eight of 36 pairs of eyes had an intereye CCP greater than 0.92 D. In both eyes of the patient with Q values less than -1.00 the profile difference maps were mildly abnormal. CONCLUSIONS: Slitlamp biomicroscopy of the cornea was unremarkable in all patients. Only 1 patient had Q values and profile difference maps that were mildly suggestive of keratoconus. Even after adding topography to the examination, it appears that keratoconus in a known population of patients with EDS remains rare.

Cornea↗
PubMed1998

The intraocular penetration of dexamethasone after photorefractive keratectomy.

BACKGROUND AND OBJECTIVE: To determine the effect of photorefractive keratectomy (PRK) on intraocular steroid penetration. MATERIALS AND METHODS: To assess steroid penetration after PRK, four rabbits underwent unilateral myopic 9.90-D PRK procedures. The other eye was left undisturbed as a control. One week later both eyes received hourly doses of radiolabeled topical dexamethasone. RESULTS: No significant difference in corneal tissue [(mean +/- 1 SD) PRK 4.8 +/- 1.1 micrograms/g, control 5.2 +/- 1.2 micrograms/g] or aqueous humor concentration [(mean +/- 1 SD) PRK 0.8 +/- 0.12 microgram/ml, control 0.9 +/- 0.05 microgram/ml] of dexamethasone was seen. CONCLUSIONS: Dexamethasone penetration in eyes 1 week following PRK is similar to that of the unablated cornea.

Animals↗
PubMed1993

Corneal endothelial cell counts after Molteno implantation.

Implantation of a Molteno drainage shunt has been shown to be effective in advanced glaucoma. Foreign substances within the anterior chamber have been known to cause progressive endothelial cell loss. We undertook a study to evaluate the endothelial effects of an indwelling Molteno drainage shunt. Nineteen patients who underwent uneventful implantation of a Molteno drainage shunt for advanced aphakic or pseudophakic glaucoma were followed up. Serial endothelial cell counts were obtained in a masked fashion. During follow-up periods ranging from 5.4 to 25.7 months, endothelial cell loss averaged two cells per square millimeter per postoperative month with a 95% confidence interval of positive seven cells to negative ten cells per square millimeter per postoperative month. No clinically significant progressive trend in endothelial cell loss was seen in patients undergoing uncomplicated Molteno drainage procedures. Larger sample sizes with longer follow-up will be necessary to establish whether a Molteno drainage shunt causes clinically remarkable endothelial cell loss.

Cell Count↗
PubMed1993

Corneal stromal penetration of topical ciprofloxacin in humans.

PURPOSE: Use of fluoroquinolone agents as single drug treatment for severe bacterial keratitis requires that adequate stromal drug concentrations are achievable that exceed the MIC90 for common corneal pathogens. The purpose of this study, therefore, is to document the human stromal penetration of the fluoroquinolone, ciprofloxacin, in human tissue obtained from patients undergoing penetrating keratoplasty. METHODS: Twelve patients, all with intact corneal epithelia, received 0.3% ciprofloxacin (Ciloxan) eyedrops every 15 minutes for the first hour and then every hour for 10 hours before their scheduled keratoplasty. Corneal tissue samples obtained from the excised buttons at the time of surgery were frozen and subsequently analyzed for drug concentration using high-pressure liquid chromatography. RESULTS: A mean corneal tissue concentration of 5.28 +/- 3.4 micrograms/g tissue (mean +/- standard deviation) of ciprofloxacin was determined. Tissue levels ranged from 1.43 micrograms/g of tissue to 10.58 micrograms/g of tissue. CONCLUSION: Ciprofloxacin penetration was variable in patients with an intact epithelium and, in some cases, did not exceed the MIC90 for some gram-positive organisms. The presence of an epithelial defect is expected to potentiate the penetration of ciprofloxacin to most likely exceed the MIC90 for most corneal pathogens.

Chromatography, High Pressure Liquid↗
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↗
PubMed1990

Penetrating keratoplasty in infants and children.

Fifty children, 2 months to 14 years of age underwent 66 penetrating keratoplasties. Included were 18 eyes with congenital corneal opacification, 16 with corneal decompensation (either from congenital glaucoma, trauma, or multiple surgeries), 10 with corneal hydrops secondary to keratoconus, and 10 with failed grafts. There were 32 clear grafts with a 1- to 10-year follow-up, 30 failed grafts, and 4 lost eyes. Acquired corneal scars, corneal decompensation, older children, and phakic eyes had the best prognosis. Corneal perforations, active inflammation or infection, and infants with multiple ocular anomalies had the poorest prognosis. Children undergoing combined procedures did less well than those undergoing a single- or two-staged procedure.

Adolescent↗
PubMed1989

A periosteal-temporalis fascia pedicle flap for repairing impending ocular perforations and extruding keratoprostheses.

We repaired four eyes in four patients with impending perforation using a vascular periosteal-temporalis fascia pedicle flap continuous to the periorbita of the orbital wall. Two eyes with extruding keratoprostheses, one eye with severe ocular surface dysfunction and a perforated, infected keratoplasty, and one eye with scleral ectasia were successfully reconstructed. Excellent visual acuity (20/25) was attained in one eye and functional visual acuity (20/100) was maintained in another. Structural integrity was maintained in all eyes. A vascularized flap was an excellent source of tissue for reconstructing eyes with impending perforation and scleral melting.

Adolescent↗
PubMed1987

Repeated radial keratotomy in the prospective evaluation of radial keratotomy study.

In the Prospective Evaluation of Radial Keratotomy study, 59 patients received a repeated radial keratotomy in which the eight additional incisions were centered between the eight initial incisions. Other aspects of the surgical technique remained the same. The average length of follow-up after the reoperation was 26 months, and ranged from 11 to 42 months. After the reoperation, 45 patients (77%) had a decrease in myopia of 0.50 diopters or more, 12 patients (20%) changed by less than 0.50 diopters, and two patients (3%) had an increase in myopia. Thirty patients (51%) remained undercorrected by more than 1.00 diopter, 27 patients (46%) were between +0.12 and -1.00 diopter, and two patients (3%) were overcorrected by more than 1.00 diopter. There was no relationship between the change in refractive error after the reoperation and any patient characteristics or surgical factors. After the reoperation, the uncorrected visual acuity increased by two to nine Snellen lines for 45 patients (76%), changed one line or less for 13 patients (22%), and decreased three lines for one patient (2%).

Evaluation Studies as Topic↗
PubMed1982

Radial keratotomy. A retrospective study of cases observed at the Kresge Eye Institute for six months.

The conclusions alter the review of 25 eyes six months following radial keratotomy are as follows: (1) The improvement in uncorrected visual acuity is dependent on multiple variables that substantially alter the results achieved. The degree to which each of these variables influences the outcome has yet to be determined; however, radial keratotomy does reduce myopia. (2) The time required for stabilization of the corneal curvature was about three months, although gradual reduction in the correction achieved occurred in a few cases between three and six months. (3) Postoperative glare at night and/or fluctuating vision was an important complaint in over one third of the patients. (4) Proper patient selection and informed consent are essential. The possibility of getting rid of glasses is not likely except for the patient with less than 3 to 4 diopters of myopia. Most patients who underwent the procedure were pleased with the improvement in unaided visual acuity, although it may have been less than they expected.

Adolescent↗
PubMed1982

Radial keratotomy in monkeys. A one-year follow-up report.

Twelve adult rhesus monkey eyes underwent a radial keratotomy, consisting of 16, deep evenly spaced radial corneal incisions extending from the edge of a 3 mm central optical zone to the limbus. Peripheral deepening incisions were used. Keratometry and retinoscopy done before and after surgery monthly for one year revealed an average of 1.79 diopters decrease in the corneal curvature and an average increase of 2.49 diopters in the refractive error, which remained stable after one to two months. No significant complications were observed despite four perforations.

Animals↗
PubMed1981

A clinical investigation of the surgical correction of myopia by the method of Fyodorov.

The surgical correction of myopia using the method of Fyodorov known as radial keratotomy consists of 16 partial thickness, radial incisions in the cornea, which result in central flattening and peripheral bulging, reducing the degree of myopia. The purpose of this investigation was to determine: (1) the amount of myopia correctable; (2) the time required for stabilization of corneal curvature changes; (3) the degree to which the variables affect the results; (4) the surgical and postoperative complications; and (5) patient motivation and satisfaction. Preliminary results revealed a significant reduction of the myopia. The keratometry readings and refractive correction required appeared to stabilize by the third month. Fluctuating vision and increased glare were the most frequent complications encountered. The preliminary results of 20 cases followed for six months postradial keratotomy are reported.

Adolescent↗
PubMed1979

Slit-lamp attachment for examination of donor corneas in McCarey-Kaufman medium.

An attachment permits slit-lamp examination of excised donor cornea in McCarey-Kaufman medium. The bottle that contains the excised cornea is placed in a holder and examined with the slit lamp by means of a mirror placed at a 45 degree angle. This mirror reflects the slit beam up through the bottom of the bottle. This allows accurate examination of the donor cornea in a stable manner that was not previously possible.

Corneal Transplantation↗