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Biomedical subjects

R F Steinert

Publications and source records attributed to R F Steinert.

At least 55 records · Page 3Linked to original sources
PubMed1991

A comparative study of masking fluids for excimer laser phototherapeutic keratectomy.

Several fluids of different viscosity were used to mask deeper tissues while exposing protruding irregularities during therapeutic keratectomy of an irregular anterior corneal surface with the 193-nm argon fluoride excimer laser. A model of an irregular anterior corneal surface was developed in deepithelialized calf eyes using grade 8-0 sandpaper. Therapeutic keratectomy was then performed on 28 eyes at a fluence of 180 mJ/cm2, a repetition rate of 10 Hz, and 500 pulses per eye. Solutions of 0.3% hydroxypropylmethylcellulose 2910 and a 0.1% dextran 70 solution, 1% carboxymethylcellulose sodium solution, or 0.9% saline solution were applied to the corneal surface of 21 eyes. Seven control eyes underwent ablation without the addition of fluid. Scanning electron microscopy demonstrated that corneas treated with dextran 70 had the least surface irregularity, and those treated with carboxymethylcellulose or saline solution had intermediate surface irregularity. Corneas that were ablated without additional fluid had the greatest surface irregularity. The application of a moderately viscous solution during therapeutic excimer laser keratectomy enhances the smoothing effect of surface ablation.

Animals↗
PubMed1991

A spectrum of bilateral squamous conjunctival tumors associated with human papillomavirus type 16.

Three patients with bilateral tumors presenting as multiple keratinizing and verrucous lesions of the bulbar and tarsal conjunctiva were determined by DNA amplification and hybridization studies to harbor human papillomavirus type 16 (HPV-16). Results of biopsy in two patients showed infiltrating squamous cell carcinoma in one eye and dysplasia or carcinoma in situ in the fellow eye. In the third patient, focal, inflamed, hypertrophic, papillary lesions with pseudoglandular invaginations of the surface epithelium were found in the tarsal conjunctivae of both eyes. These are the first documented cases of bilateral conjunctival tumors associated with human papillomavirus.

Adult↗
PubMed1991

Current therapy for bacterial keratitis and bacterial conjunctivitis.

Therapy of bacterial keratitis and conjunctivitis requires that antibiotics be administered to eliminate viable bacteria. Only a limited number of ophthalmic antibiotics are commercially available. Although generally adequate for the treatment of bacterial conjunctivitis, the commercial preparations are believed to contain too low a concentration of antibiotic for the treatment of bacterial keratitis. Using products designed for parenteral administration, the ophthalmologist or the pharmacist formulates so-called fortified preparations containing much higher antibiotic concentrations. Because of their limited spectrum of action, two fortified preparations generally are administered concurrently. Topical application is the most effective route of antibiotic administration for treatment of bacterial keratitis. Antibiotics may also be injected periocularly, a method with risk, or intravenously, a method of uncertain efficacy.

Administration, Topical↗
PubMed1991

Astigmatism after small incision cataract surgery. A prospective, randomized, multicenter comparison of 4- and 6.5-mm incisions.

Four surgeons evaluated induced astigmatism and postoperative wound stability in a randomized prospective study of 130 patients undergoing cataract extraction. After phacoemulsification through a scleral pocket, patients received either a 6.5-mm diameter silicone optic posterior chamber intraocular lens (PC IOL) folded for insertion through a 4-mm small incision or a 6.0-mm diameter polymethylmethacrylate (PMMA) optic PC IOL placed through an approximately 6.5-mm conventional incision. Vector analysis calculations of prism diopters (D) of mean postoperative-induced keratometric astigmatism for the small incision versus conventional incision groups were, at day 1, 1.54 D versus 3.07 D (P less than 0.0001); at weeks 1 to 2, 1.00 D versus 2.43 D (P less than 0.0001); at 1 month, 0.98 D versus 1.44 D (P = 0.004); and at 3 months, 0.82 D versus 1.03 D (P = 0.089). Subgroup analysis of the suturing technique for the 6.5-mm incision showed that the technique of wound closure, as well as the wound size, influenced the induced astigmatism. For all four surgeons using three methods of suturing the 6.5-mm wound, however, the variability in the amount of induced cylinder was least with the 4.0-mm wound closed with a horizontal mattress suture. Complications in the two groups were comparable.

Aged↗
PubMed1990

Immunofluorescence study of corneal wound healing after excimer laser anterior keratectomy in the monkey eye.

We performed anterior keratectomies on six monkey eyes, four by excimer laser large-area ablation at 193 nm and two by mechanical keratectomy. Immunofluorescence was used to study the wound healing response histopathologically. The distribution of fibrinogen, fibronectin, laminin, collagen types III, IV, and VI, and keratan sulfate was determined at postoperative intervals of 24 hours, 6 days, and 1 month. At 24 hours, fibrinogen and fibronectin coated the ablated surface, but corneal epithelial cells had not yet migrated over the wound. By 6 days and persisting at 1 month, an epithelial ingrowth of seven to 10 layers, mild stromal hypercellularity, and new collagen formation were present in the repair region. At 1 month, fibrinogen, fibronectin, laminin, and type III collagen were strongly detected in the repair region. Type VI collagen was present in both normal and healed corneal stroma at all intervals, and type IV collagen was present in Descemet's membrane only. Sulfated keratan sulfate was absent from the newly synthesized collagen stroma at all intervals. Slit-lamp photographs demonstrated corneal haze in the ablation zone in all cases at 24 hours, persisting for 1 month. The fluorescence patterns produced by excimer laser ablation and mechanical keratectomy were qualitatively identical.

Animals↗
PubMed1990

Penetrating keratoplasty for pseudophakic bullous keratopathy associated with closed-loop anterior chamber intraocular lenses.

Closed-loop anterior chamber intraocular lenses (AC IOLs) are associated with a high incidence of pseudophakic bullous keratopathy (PBK). The prognosis for recovery of vision with penetrating keratoplasty and the exchange of one type of AC IOL for another remains controversial. A total of 40 consecutive patients with closed-loop AC IOLs and varying degrees of PBK underwent penetrating keratoplasty, explanation of the closed-loop AC IOL, and implantation of a flexible tripod AC IOL--all done with a uniform technique. The average follow-up study was 24 months. Average preoperative visual acuity was 20/170 (range, 20/25-hand motions) and average postoperative visual acuity was 20/44 (range, 20/20-no light perception). A total of 23 eyes (57.5%) achieved a visual acuity of 20/40 or better. Eleven eyes (27.5%) had a visual acuity of 20/200 or worse. Persistent cystoid macular edema was the most frequent cause of poor vision postoperatively (4 eyes), followed by age-related macular degeneration (3 eyes) and graft rejection (2 eyes). This is the first series documenting a good visual outcome for at least 2 years after penetrating keratoplasty and exchange of a closed-loop AC IOL for a single type of flexible tripod AC IOL.

Aged↗
PubMed1989

Neodymium:YAG laser anterior vitreolysis for Irvine-Gass cystoid macular edema.

Twenty-nine consecutive patients with vitreous incarceration in the wound after cataract surgery and cystoid macular edema (Irvine-Gass syndrome) were treated with Nd:YAG laser anterior vitreolysis. Fifty-five percent (55%) achieved two or more lines of stable visual improvement; 17% improved but with fluctuating levels of vision and persistent edema; 28% failed to improve, half of them because of coexisting ocular pathology. Visual improvement was achieved an average of 3.5 months after treatment. Persistent macular edema was associated with several types of anterior chamber intraocular lenses.

Anterior Eye Segment↗
PubMed1989

Epikeratoplasty for adult and pediatric aphakia, myopia, and keratoconus: the Massachusetts Eye and Ear Infirmary experience.

Between February, 1985 and February, 1987, 49 eyes of 47 patients underwent epikeratoplasty for one of the following indications: adult aphakia (21 eyes; 20 patients), pediatric aphakia (10 eyes; 10 patients), myopia (7 eyes; 6 patients), and keratoconus (11 eyes; 11 patients). Follow-up at least 12 months (average = 18 months) is available for all 49 eyes. Of 49 eyes, 44 (90%) were anatomically successful with an intact, clear lenticule at least 12 months post-operatively, with no significant difference between the four groups (adult aphakia = 90%, pediatric aphakia = 90%, myopia = 86%, and keratoconus = 91%). The functional success rate, however, was 91% for keratoconus, 81% for adult aphakia, 80% for pediatric aphakia, and only 43% for myopia. We conclude that epikeratoplasty can be an effective tool in the treatment of carefully selected patients with adult or pediatric aphakia and keratoconus, but has only limited applicability in the management of myopia.

Adult↗
PubMed1988

Adequacy of the ELISA test for screening corneal transplant donors.

Using a simple mathematical model, we calculated the risk for a patient undergoing penetrating keratoplasty to receive a cornea from a human immunodeficiency virus-infected donor despite negative results on serologic testing of donor serum. This error in serologic testing occurred when false-negative results were obtained from the enzyme-linked immunosorbent assay used to screen donor corneas for human immunodeficiency virus exposure. The average risk of transplanting an infected cornea was low, 0.03%, but increased by a factor of ten when donor tissue from donors at high risk for AIDS was used. Current screening procedures are probably adequate to prevent transmission of human immunodeficiency virus, but increased vigilance for high-risk donor populations may be appropriate.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Long-term comparison of epikeratoplasty and penetrating keratoplasty for keratoconus.

The results of epikeratoplasty for keratoconus in ten patients with long-term follow-up (mean, 25 months; range, 19 to 31 months) vs ten patients with contemporaneous penetrating keratoplasty for keratoconus (mean, 33 months; range, three to 81 months) indicate a similar level of postoperative spectacle visual acuity (20/32 vs 20/27, respectively) and similar refractive and keratometric results. The healing period until achieving best corrected visual acuity averaged 12 months for epikeratoplasty vs three months for penetrating keratoplasty. Compared with penetrating keratoplasty, epikeratoplasty offers the advantages of maintaining an intact globe surgically and postoperatively in a young, active population, while avoiding potential immune rejection. The major disadvantages are a prolonged healing period and undefined limits in the extent of the cone that would define suitable candidates preoperatively.

Contact Lenses↗
PubMed1988

Epithelial abnormalities and sterile ulceration of epikeratoplasty grafts.

Six epikeratoplasty (EKP) specimens were obtained 1 to 10 months after refractive keratoplasty for aphakia (2 cases), keratoconus (1 case), and myopia (3 cases). The EKP grafts were removed because of postoperative complications such as delayed reepithelialization, lenticule edema, stromal ulceration, graft opacification, and inability to improve vision in a clear graft. The extent of epithelial abnormalities was associated directly with the severity of structural changes in the underlying basal lamina, Bowman's layer, and stroma as evidenced by electron microscopic examination. Epithelial defects were associated with varying degrees of sterile stromal ulceration of the underlying lenticule. In one case, an extensive full-thickness ulceration of the EKP button occurred in the area of persistent epithelial defects and was associated with a major ulceration of the underlying recipient's corneal stroma. Removing the failing button halted the ulcerative process with prompt reepithelialization. In the absence of inflammation and infection, the persistent epithelial abnormalities and defects leading to proteolytic degradation of the EKP buttons constitute an important mechanism of graft failure with major visual consequences and possibly irreversible ocular damage.

Adult↗
PubMed1988

Postoperative management of epikeratoplasty.

Epikeratoplasty is the surface implantation of devitalized human corneal tissue onto a recipient cornea for optical rehabilitation. Its postoperative management can be divided into three stages: (1) epithelialization, (2) suture management, and (3) restoration of visual function. Careful attention to each of the healing phases and the multiple potential complications that commonly arise is required for a satisfactory level of visual performance to be achieved in a high proportion of cases.

Anti-Bacterial Agents↗
PubMed1987

Quantitative and ultrastructural studies of excimer laser ablation of the cornea at 193 and 248 nanometers.

Excimer laser radiation at 193 nm and 248 nm was used to create linear etch perforations of enucleated calf corneas. The etch depth per pulse was determined for various exposures, and specimens were examined by light and transmission electron microscopy. Compared to 248 nm, excimer laser ablation at 193 nm was found to have a lower threshold for onset of ablation, less increase in etch depth per pulse at increasing fluences, and less structural alteration in adjacent cornea. For 193 nm, structural alterations were minimal, confined to an area less than 0.3 micron wide, and did not increase with increasing fluence. These studies suggest that clinical strategies for excimer laser refractive surgery will employ the 193-nm wavelength, with fluence chosen depending on surgical strategy. Ablation exposures above 600 mJ/cm2 at 193 nm may give the most repeatable etch depth.

Animals↗