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Biomedical subjects

J J Rowsey

Publications and source records attributed to J J Rowsey.

At least 19 recordsLinked to original sources
PubMed1998

The immunology of corneal graft rejection.

Corneal transplantation is the most successful of organ transplants due to the fact that the eye is an immunologically privileged site, and the cornea is an immunologically privileged tissue. The factors responsible for this include presence of the blood-aqueous barrier, the avascularity of the cornea, the absence of classic antigen-presenting cells (APCs) in the central cornea, inhibitory factors in the aqueous humor, the phenomenon known as anterior chamber-associated immune deviation (ACAID), and the intraocular expression of Fas ligand. Loss of ocular immune privilege can occur with breaching of the blood-ocular barrier, corneal neovascularization, migration of classic APCs to the center of the cornea, loss of inhibitory factors in aqueous humor, abrogation of ACAID, and loss of Fas ligand expression within the anterior chamber. The purpose of this review is to analyze these events and how they relate to corneal graft rejection. A discussion on future research and therapeutic modalities is provided.

Animals↗
PubMed1997

Cystic epithelial downgrowth following clear-corneal cataract extraction.

Epithelial downgrowth is a serious complication of intraocular surgery. It is characterized by the diffuse or cystic proliferation of surface epithelium inside the eye. Advances in microsurgical technique that result in smaller surgical wounds and permit greater precision in wound closure should reduce the incidence of this complication. We report a case of epithelial downgrowth presenting 3 years after an uncomplicated clear-corneal cataract extraction with insertion of a posterior chamber silicone lens. The epithelial down-growth was amenable to surgical correction because the well-defined cyst could be excised en bloc.

Aged↗
PubMed1997

The Tampa Trephine technique with cat corneal endothelium.

The Tampa Trephine (Martin Marietta Speciality Components, Largo, FL, U.S.A.) penetrating keratoplasty technique uses a 7.0-mm corneal donor button with six rectangular 1 x 2-mm tabs of Bowman's layer, 75 microns in thickness, which are inserted into the recipient stroma beneath Bowman's layer. We evaluated the safety of the Tampa Trephine tissue-trephination method on the cat corneal endothelium combining vital staining and scanning electron microscopy, comparing it with the standard Weck trephination technique. The Tampa Trephine tissue trephination produces a donor button with a 6.7-mm diameter central area of normal endothelium. Localized peripheral areas of cellular loss, endothelial and Descemet's tears, endothelial detachment, and folding along the border of the trephination were observed with the Tampa Trephine method, all located in an area of < or = 150 microns, adjacent to the edge of the button. Standard trephination induced a localized peripheral area of endothelial damage < 50 microns in extension from the donor edge. A theoretic maximal 8.4% peripheral endothelial cell loss is induced with the Tampa Trephine trephination method, compared with a 2.8% loss with the standard procedure. The peripheral location of the alterations after the Tampa Trephine does not hinder the viability of the corneal endothelium, as it has been clinically observed.

Animals↗
PubMed1996

Use of a mirror needle holder with transsclerally sutured posterior chamber intraocular lenses.

A mirror needle holder has been designed to facilitate the passage of a needle through the ciliary sulcus during transscleral fixation of posterior chamber (PC) intraocular lens (IOLs). Two human postmortem eyes were used to demonstrate the efficacy of this mirror used as the needle holder. This method was compared with the current method of passing sutures without view of the ciliary sulcus. The mirror needle holder demonstrated precise passage of the needle into the ciliary sulcus by direct visualization of the ciliary processes and sulcus. This method may avoid the complications associated with transsclerally sutured PC IOLs during penetrating keratoplasty and secondary IOL placement.

Ciliary Body↗
PubMed1993

Combined treatment of Acanthamoeba keratitis with propamidine, neomycin, and polyhexamethylene biguanide.

We developed an intensive treatment regimen of topical neomycin, propamidine, and polyhexamethylene biguanide that was tapered to a maintenance level over a 14- to 28-day period as toxicity developed. Since July 1991, we used this treatment on six eyes of five patients in whom Acanthamoeba keratitis was diagnosed clinically. All patients had positive cultures for microorganisms from their corneas or contact lens cases or had pathognomonic findings of pseudodendritic subepithelial infiltrates and radial keratone-uritis. After therapy, all patients improved within two to four weeks, with regression or resolution of neuritis and infiltrates, healing of epithelial defects, and lessening of pain. By three to four months, visual acuity had returned to 20/20 in all eyes. We believe the addition of polyhexamethylene biguanide to our treatment regimen in Acanthamoeba keratitis dramatically aided and hastened the clinical improvement in five consecutive patients and may, with early diagnosis, increase the number of medical cures.

Acanthamoeba Keratitis↗
PubMed1993

Photography of shock waves during excimer laser ablation of the cornea. Effect of helium gas on propagation velocity.

Shadow photography of shock waves excited by means of a xenon chloride excimer laser was performed to determine the shock wave propagation velocity in air, nitrogen and helium. Energy densities between 500 and 2,000 mJ/cm2 were used to ablate a rotating rubber cylindrical target and porcine corneas. In ablating the rubber cylinder, a shock wave velocity of 3.3 km/s was generated in air and nitrogen at 40 ns; this decreased to 1.4 km/s at 320 ns. When helium was blown on the target, the velocity increased by a factor of approximately two, to 5.9 km/s at 40 ns and 2.7 km/s at 320 ns. We suggest that blowing helium on the surface of the cornea during excimer laser ablation may speed the dissipation of high-energy acoustic waves and gaseous particles, and thus reduce the exposure and transfer of heat energy to the surrounding tissue.

Animals↗
PubMed1993

Peters' anomaly: a review of 26 penetrating keratoplasties in infants.

We reviewed the specimen records log of the McGee Eye Institute Histopathology Service from January 1979 to December 1990 for penetrating keratoplasty specimens submitted with a clinical diagnosis of Peters' anomaly. The records of the 19 cases thereby identified were reviewed for clinical outcome and visual rehabilitation, and the histopathology of all specimens was reviewed and correlated with the clinical diagnosis. Two specimens from the same patient were eliminated as histopathologically inconsistent with Peters' anomaly; one patient's data were not used because the patient was an adult when first grafted. Six eyes were grafted two or more times, for a total of 26 grafts on 16 eyes in 10 patients. Mean age at the time of first transplant was 18 weeks (range, 3 weeks to 40 months). Mean follow up was 30 months (range, 7 months to 6 1/2 years). Five eyes had preoperative glaucoma which persisted postoperatively. Ten eyes developed glaucoma postoperatively. Of the 15 eyes with glaucoma, 14 were uncontrolled medically and 12 underwent cyclodestructive or Molteno filtering procedures, or both, to control pressure. Graft rejection developed in 9 of the 10 eyes that required a cyclodestructive procedure, with partial or complete graft failure occurring shortly after the procedure. Glaucoma did not develop in one eye; in one other eye, it was medically controlled. These 2 eyes maintained clear grafts. Of the 6 eyes that were regrafted, only 1 obtained ambulatory vision. Of the 26 eyes receiving grafts, the grafts failed completely in 17 and partially in 5; 4 have remained clear. Five patients maintain ambulatory vision.

Child, Preschool↗
PubMed1992

Treatment of alkali-injured rabbit corneas with a synthetic inhibitor of matrix metalloproteinases.

Healing of corneal alkali injuries remains a severe clinical challenge. The authors evaluated the effect of a new synthetic inhibitor of matrix metalloproteinases (GM6001 or N-[2(R)-2-(hydroxamido carbonylmethyl)-4-methylpentanoyl]-L-tryptophane methylamide) on preventing ulceration of rabbit corneas after alkali injury. Topical treatment of corneas with severe alkali injuries with 400 micrograms/ml or 40 micrograms/ml GM6001 alone prevented ulceration for 28 days, although 8 of 10 corneas treated with vehicle perforated. Corneas treated with 4 micrograms/ml GM6001 had midstromal depth ulcers. Corneas treated with 400 micrograms/ml of GM6001 contained very few inflammatory cells and had significantly reduced vessel ingrowth compared with vehicle-treated corneas. Epithelial regeneration after moderate alkali injuries also was investigated. Persistent epithelial defects developed 4 days after moderate alkali injury in rabbit corneas treated with vehicle and progressively increased to an average of 20% of the original 6 mm diameter wound by 27 days after moderate alkali injury. By contrast, epithelial regeneration was complete and persisted for 21 days for corneas treated with a formulation containing GM6001 (400 micrograms/ml), epidermal growth factor (10 micrograms/ml), fibronectin (500 micrograms/ml), and aprotinin (400 micrograms/ml). Sporadic punctate staining developed in 20% of the corneas treated with the combination of agents between days 21-28 after moderate alkali injury. These results demonstrate that topical application of GM6001 prevented corneal ulceration after severe alkali injury and that a combination containing GM6001, epidermal growth factor, fibronectin, and aprotinin promoted stable regeneration of corneal epithelium after moderate alkali injury.

Alkalies↗
PubMed1991

Ocular infections associated with Comamonas acidovorans.

Comamonas acidovorans (Pseudomonas acidovorans) is a ubiquitous gram-negative rod. Although generally considered nonpathogenic, we found C. acidovorans to be associated with six cases of ocular infections. The organism was the only isolate in three cases, whereas an association of other organisms was present in three cases. The multiple resistance patterns of these strains to antibiotic susceptibility testing emphasizes the need for culturing ocular infections. We recommend the identification and susceptibility testing of all ocular gram-negative rod isolates.

Adolescent↗
PubMed1991

Clinical use of the 193-nm excimer laser in the treatment of corneal scars.

Phototherapeutic keratectomy using a 193-nm excimer laser was performed at four centers on 33 sighted patients with corneal opacity and/or irregular astigmatism. Pathologic conditions included anterior stromal and superficial scarring from postinfectious and posttraumatic causes, including inactive herpes simplex virus, anterior corneal dystrophies, recurrent erosions, granular dystrophy, and band keratopathy. Most patients received peribulbar anesthesia and underwent removal of the epithelium prior to laser ablation. A majority of patients had a reduction in the amount of corneal scarring and approximately half had improved visual acuity. No intraocular reaction or changes in endothelial counts were seen, and some patients avoided the need for penetrating keratoplasty. Reepithelialization usually occurred within 4 or 5 days and we noted no significant scarring secondary to use of the laser. It was difficult to eliminate preexisting irregular astigmatism despite the use of surface modulators, such as methylcellulose. A hyperopic shift secondary to corneal flattening was encountered in approximately 50% of the patients. A combination of myopic ablation, followed immediately by a secondary hyperopic steepening, may minimize this refractive change. The 193-nm excimer laser is an effective new tool in the treatment of selected patients with superficial corneal opacity from a variety of conditions.

Adult↗
PubMed1991

Infectious endophthalmitis following sutureless cataract surgery.

Within the last 6 months, three cases of infectious endophthalmitis following sutureless cataract surgery have been referred to us. Two of these cases followed uncomplicated sutureless phacoemulsification with intraocular lens implantation. One case was complicated by a postoperative hyphema with additional surgery for clot removal 2 days following the initial procedure.

Aged↗
PubMed1991

Effect of oxygen free radicals on corneal collagen.

Corneal collagen was labeled in vivo by injection of 14C-proline into the anterior chamber of rabbit eyes. The isolated corneal collagen was incubated in iron-free phosphate buffered saline (pH 7.4) containing 1 mM ascorbate and 0.1 mM CuSO4 for either 1 hour or 3 hours at 37 degrees. Addition of 2 volumes of 8M urea-1 mM dithiothreitol and heating for 1 min at 100 degrees solubilized virutually all of the collagen in the control incubations but left a significant amount of insoluble collagen in specimens exposed to the hydroxyl radical generating system. This residue amounted to 19% and 38% of the initial radioactivity in samples incubated for 1 h and 3 h, respectively. The chromatographic profiles (gel filtration on CL-4B) of the soluble fraction showed an increase in both aggregation and degradation products of collagen in the 1 h incubation mixture, whereas after 3 h there was an increase only in degradation products. These observations suggest that additional crosslinking of the soluble collagen aggregates observed at 1 h may be responsible for their subsequent disappearance at 3 h, with concomitant increase of the insoluble fraction. Collagen degradation by .OH may play a role in corneal ulceration, whereas hydroxyl radical-mediated crosslinking is consistent with age-dependent increases in insoluble collagen.

Animals↗
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↗