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Biomedical subjects

S Kwitko

Publications and source records attributed to S Kwitko.

At least 19 recordsLinked to original sources
PubMed2001

Laser in situ keratomileusis after penetrating keratoplasty.

PURPOSE: To assess the outcomes of laser in situ keratomileusis (LASIK) after penetrating keratoplasty (PKP). SETTING: Hospital de Clínicas de Porto Alegre, Department of Ophthalmology, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil. METHODS: Fourteen eyes of 13 patients who had LASIK after PKP were retrospectively reviewed. The interval between LASIK and PKP was at least 1 year, and the follow-up after LASIK was also at least 1 year. All patients had a stable refractive error for a minimum of 6 months after all sutures were removed, regular and symmetric topographic astigmatism, and a minimal ultrasonic central corneal pachymetry of 500 microm. The Chiron Automatic Corneal Shaper and the Meditec Aesculap MEL 60 excimer laser were used. RESULTS: At 12 months, mean myopia decreased from -5.33 diopters (D) +/- 4.22 (SD) to 0.19 +/- 1.71 D, mean hyperopia decreased from +5.04 +/- 3.32 D to + 0.42 +/- 0.46 D, and mean astigmatism decreased from 5.37 +/- 2.12 D to 2.82 +/- 2.42 D (47.5% of mean percentage reduction). Retreatment was necessary in 42.9% of eyes because of cylindrical undercorrection. Uncorrected visual acuity improved in 11 eyes (78.6%). Best spectacle-corrected visual acuity improved in 6 eyes (42.8%) and was maintained in 4 eyes (28.6%); 5 eyes (35.7%) lost 1 Snellen line. Intraoperative complications included 1 buttonhole flap. Postoperative complications included interface epithelial ingrowth at the periphery (2 eyes) and pseudophakic retinal detachment 2 years after LASIK (1 eye). CONCLUSION: Laser in situ keratomileusis after PKP safely and predictably corrected the spherical component of the refraction. However, the predictability of LASIK in correcting post-PKP astigmatism was poor.

Adult↗
PubMed2000

Potential acuity meter accuracy in cataract patients.

PURPOSE: To determine potential acuity meter (PAM) accuracy in patients with cataract as the only ocular disease. SETTING: Hospital de Clínicas de Porto Alegre, Brazil. METHODS: This prospective study comprised 74 eyes with cataract. Patients with other ocular pathology diagnosed before or after surgery, as well as those with complicated surgeries, were excluded. All patients had PAM evaluation before surgery; these results were compared to the final postoperative visual acuity. Patients were divided into 4 cataract groups based on the Lens Opacity Classification System II: Group 1, early cataracts (nuclear opalescence [NO] 1 and/or posterior subcapsular cataracts [P] 1 and/or cortical opacity [C] < 2); Group 2, definite cataracts (NO2 and/or C2, with or without P1); Group 3, posterior cataracts (P2 or P3); Group 4, mature cataracts (N3 and/or C > or = 3, with or without P1). The PAM result was considered accurate if it was within 2 lines of the postoperative best spectacle-corrected visual acuity (BSCVA) 3 months after surgery. RESULTS: All patients had a BSCVA of 20/20. Accuracy of the PAM was 58.3% in Group 1, 50.0% in Group 2, 27.8% in Group 3, and 6.7% in Group 4 (P =.000 017). Patient age did not influence the results. CONCLUSIONS: The PAM may be used as a complementary tool in evaluating early and nondense cataracts; however, patients should not be excluded as candidates for cataract surgery based solely on PAM results.

Cataract↗
PubMed1997

Anterior segment prosthesis development: retinal function following anterior segment removal.

Replacement of the entire anterior segment of the eye is a very ambitious and complex endeavor and it is not known whether the retina remains functional when the anterior structures have been removed. We used routine histo-pathologic evaluation and electroretinographic measurements to determine the structural and functional status of rabbit retinas following surgical removal of the internal anterior structures (iris, ciliary body, and lens) and replacement of the vitreous with silicone oil. In some cases, we were able to record both a scotopic and a photopic electroretinographic response as long as 15 weeks after complete removal of the internal anterior segment structures. Although many hurdles remain and more efficacious surgical techniques and biomaterials need to be developed, our results suggest that, in the rabbit, the retina may continue to function in the absence of critical anterior segment structures.

Animals↗
PubMed1995

Allograft conjunctival transplantation for bilateral ocular surface disorders.

PURPOSE: The purpose of this study is to evaluate the efficacy of allogenic conjunctival transplantation in bilateral surface disorders and to correlate with human leukocyte antigen (HLA) typing and cross-matching. METHODS: A prospective study of allogenic conjunctival transplantation was undertaken in 12 eyes of 10 patients with bilateral surface disorders. Five eyes had Stevens-Johnson syndrome, three had Lyell syndrome, three had bilateral alkali burns, and one had a bilateral thermal burn. Human leukocyte antigen typing and cross-matching were retrospectively performed in eight patients and their respective donors. Stabilization of corneal epithelia, visual acuity, and rejection episodes were examined after the procedure. RESULTS: Eleven (91.6%) of 12 eyes had improved visual acuity, corneal transparency and surface lubrication, stabilization of corneal epithelia, and decreased corneal neovascularization and photophobia after an average follow-up of 17.2 months. Three patients (25%) had rejection episodes, with no disturbance in corneal surface in two. Two of these three patients had 100% incompatible HLA donor-recipient pairs; HLA of the third patient was not available. Patients with favorable evolution were either HLA identical or haplo-identical (50% identity) with their donors. Donor eyes did not present any epithelial problems during the follow-up period. CONCLUSIONS: Human leukocyte antigen-matched allogenic conjunctival transplantation proved to be an adequate method of treating severe bilateral surface disorders, with minimal complications.

Adolescent↗
PubMed1995

Bacterial contamination in soft contact lens wearers.

We prospectively analyzed bacterial contamination in 15 soft contact lens wearing subjects. Contact lenses, cases, tips of saline solution bottles, and conjunctiva were cultured. Cultures were positive for 13 subjects (86.6%). Contamination was present in 13 contact lens cases (86.6%), 12 contact lenses (80.0%), nine saline solution bottles (60.0%), and in the conjunctiva of three patients (20.0%). Gram-negative bacteria (Pseudomonas aeruginosa and Proteus mirabilis) were the most frequently isolated organisms. Staphylococcus aureus was the only gram-positive organism isolated. We discuss the possible sources of contamination, and emphasize the importance of contact lens care instruction.

Adolescent↗
PubMed1994

Intraocular lens implantation in Terrien's marginal corneal degeneration.

A patient with Terrien's corneal marginal degeneration and a previous trabeculectomy had planned extracapsular cataract extraction with intraocular lens implantation. A corneal incision was made with a diamond blade on the degeneration furrow superiorly and was closed with a 10-0 nylon double-running suture with keratoscopic control.

Cataract Extraction↗
PubMed1992

Diurnal variation of corneal topography after radial keratotomy.

A computerized videokeratography system was used to evaluate diurnal changes in corneal curvature of both untreated and surgically treated eyes of 11 patients who had undergone unilateral radial keratotomy. The mean postoperative interval was 34.5 months. Both corneas operated on and those not operated on steepened on average from morning to evening. For untreated eyes, this diurnal steepening was statistically significant at a distance of 0.5 mm from the corneal apex (mean +/- SE, 0.36 +/- 0.07 diopter) and in the inferotemporal quadrant (0.28 +/- 0.08 D); in eyes that had undergone radial keratotomy, steepening was significant at from 1.0 to 3.0 mm from the corneal apex (0.39 +/- 0.07 D) and temporal, inferotemporal, inferior, inferonasal, nasal, and superonasal to the corneal apex (0.42 +/- 0.08 D). The greatest steepening in the eyes treated with radial keratotomy compared with the untreated eyes occurred at 1.5 to 2.5 mm peripheral to the corneal apex in the inferonasal and nasal octants. Diurnal changes in intraocular pressure, corneal thickness, number of incisions, clear-zone size, postoperative period, and patient sex were not predictive of the magnitude of morning-to-evening change. Furthermore, diurnal changes in corneal curvature of untreated eyes were not predictive of diurnal changes in the fellow eyes after radial keratotomy.

Adult↗
PubMed1992

Corneal topographic changes following strabismus surgery in Grave's disease.

A computerized topographic analysis system was used to evaluate corneal changes after strabismus surgery in eight eyes of five patients with Graves' disease. All patients underwent inferior rectus muscle recession; three eyes also had medial rectus recession. Corneal topographic analysis revealed that, postoperatively, corneas steepened inferiorly and inferotemporally at 1.5 mm from corneal apex (p less than 0.05). The opposite effect was observed in the superior quadrant (average flattening of 1.20 +/- 0.32 D at 1.5 mm from corneal apex, and 1.08 +/- 0.39 D at 3.0 mm from corneal apex; p less than 0.05). Superotemporally, the cornea flattened by an average of 0.65 +/- 0.26 D at 3.0 mm from corneal apex, and superonasally 0.72 +/- 0.19 D at 3.0 mm from corneal apex (p less than 0.05). Central, nasal, and temporal cornea did not show statistically significant changes. Spherical equivalent did not change significantly after surgery. The amount of restriction and upgaze measured preoperatively was correlated weakly with inferior corneal steepening (r2 = 0.44; p = 0.046). These results are indicative that corneal topography may be influenced by strabismus surgery for Graves' disease through alteration of extraocular muscle tension or intraocular pressure.

Adult↗
PubMed1992

Anti-inflammatory therapy and outcome in a guinea pig model of Pseudomonas keratitis.

Corneal scarring as a consequence of bacterial keratitis is an important cause of visual loss and a major indication for penetrating keratoplasty. Anti-inflammatory agents might be useful in this condition for limiting corneal damage, but benefit from adjunctive anti-inflammatory therapy has never been demonstrated. In this limited pilot study, we compared the effect on clinical outcome of treating Pseudomonas keratitis in guinea pigs with prednisolone (a corticosteroid), flurbiprofen (a cyclo-oxygenase inhibitor), nordihydroguaiaretic acid (a lipoxygenase inhibitor), and a leukotriene antagonist, SKF104353 [R-(R*, S*)]-beta-[(2-carboxyethyl) thio-alpha-hydroxy-2-(8-phenyloctyl) benzenepropanoic acid, zinc salt]. None of the anti-inflammatory agents prevented sterilization of ulcers with antibiotic (ofloxacin) therapy. Therapy with the leukotriene antagonist appeared to reduce infiltrate size more quickly and produce a more rapid reduction in lesion size, but the differences were not statistically significant. Sample size calculations suggest that very large numbers of animals would be required to prove efficacy. The role of anti-inflammatory agents in reducing the stromal destruction caused by bacterial keratitis remains controversial.

Analysis of Variance↗
PubMed1992

Recurrence of microbial keratitis concomitant with antiinflammatory treatment in an animal model.

Recurrence of Pseudomonas keratitis during treatment with corticosteroids has been reported previously in humans. Rabbits with keratitis due to Pseudomonas aeruginosa or Streptococcus pneumoniae were treated with antibiotics and either vehicle, methylprednisolone acetate, flurbiprofen, or nordihydroguaiaretic acid (NDGA). Cultures performed after 7 days were negative, and antibiotics were discontinued. Two weeks later, Pseudomonas keratitis recurred in 6 of 7 (85.7%) steroid-treated rabbits, 1 of 8 (12.5%) flurbiprofen-treated rabbits, 1 of 8 (12.5%) NDGA-treated rabbits, and none of 8 vehicle-treated rabbits. None of the 31 rabbits infected with Streptococcus pneumoniae experienced recurrence. These data confirm the clinical observation that Pseudomonas keratitis may recur if antibiotic therapy is discontinued and corticosteroids are administered; the risk of recurrence appears to be much less with nonsteroidal antiinflammatory agents.

Animals↗
PubMed1992

Pharmacologic alteration of corneal topography after radial keratotomy.

Contraction of corneal wounds as the incisions heal may account for changes in corneal topography after radial keratotomy; such contractility of avascular corneal wounds has been demonstrated in vitro. Using a cat model of radial keratotomy, we demonstrated in vivo contractility of radial keratotomy incisions. In eight eyes of adult female cats, four-incision radial keratotomies were performed, producing central corneal flattening. After 3 and 8 days, serotonin (1 mg/mL) was applied. On day 3, application of topical serotonin resulted in corneal steepening (P < .0001); serotonin produced no topographic changes when applied on day 8 and had no effect on normal unoperated corneas. Vehicle produced no change in corneal curvature before or at any time after radial keratotomy. Fluorescence microscopy revealed cells with myofibroblastic differentiation at the incisions. These data suggest that cells with contractile abilities play a role in determining corneal topography after radial keratotomy.

Animals↗
PubMed1992

Computer-assisted study of diurnal variation in corneal topography after penetrating keratoplasty.

Diurnal changes in corneal topography have been documented to be greater in eyes following radial keratotomy that in normal eyes. To determine whether substantial changes of this nature result from corneal incisions in general or are a specific complication of radial keratotomy, we examined 12 corneas (10 patients) after penetrating keratoplasty for diurnal changes, using a computerized corneal topographic analysis system. Diurnal changes in keratometry readings, central corneal thickness, intraocular pressure, and refraction also were analyzed. From morning to evening, central corneal curvature flattened by an average of 0.74 +/- 0.18 diopters in eight eyes (67%), and steepened by an average of 2.00 +/- 0.53 D in four eyes (33%). Diurnal changes in central corneal thickness were correlated with diurnal changes in central corneal curvature (r = 0.63, P less than .05). These data suggest that changes in corneal thickness over the course of the day may partially account for the changes in corneal curvature demonstrated to occur following penetrating keratoplasty.

Adult↗
PubMed1991

Prospective corneal topographic analysis in surgery for postkeratoplasty astigmatism.

Computer-assisted photokeratoscopy was used to evaluate the topographic characteristics of corneas preoperatively and postoperatively in seven patients who underwent surgery for correction of postkeratoplasty astigmatism. The steep hemimeridians were typically separated by an angle other than 180 degrees (mean, 162.5 degrees) and the flat hemimeridians were often not orthogonal to the steep hemimeridians. Asymmetry of power (1.5 or more diopters) between these two major hemimeridians was also observed in three patients. Relaxing incisions were placed in the two steep hemimeridians and compression sutures were placed in the flat hemimeridians. The mean percent of reduction of astigmatism (vector-corrected) was 81.1%. The amount of keratometric astigmatism, and the degree of asymmetry of the hemimeridians were not correlated with the percent of reduction of astigmatism after placement of the relaxing and compression sutures. Computer-assisted topographic analysis may prove useful in planning transverse keratotomies centered on the steep hemimeridians and in placement of compression sutures in flat hemimeridians.

Adult↗
PubMed1991

Characterization of infectious crystalline keratitis caused by a human isolate of Streptococcus mitis.

Streptococcus mitis isolated from a human with infectious crystalline keratitis was injected intrastromally into corneas of adult New Zealand white rabbits that were treated with tetracycline hydrochloride, methylprednisolone acetate, or a combination of tetracycline and methylprednisolone. Animals were followed up for up to 44 days; untreated corneas and those treated with tetracycline developed no disease or "fluffy" stromal infiltrates with overlying epithelial defects representing an abscess. Corneas treated with the combination of tetracycline and corticosteroid usually developed crystalline stromal opacities that on histopathologic examination were shown to be intrastromal aggregates of cocci. Transmission electron microscopy of crystalline lesions within 10 days of infection revealed typical cocci intermixed with a fibrillar material having periodicity characteristic of fibrinogen or fibrin, and immunoperoxidase staining for fibrinogen was positive. By 1 month, electron microscopy revealed aggregates of degenerated bacteria that were surrounded by cellular processes of activated keratocytes. Our studies demonstrate a model for crystalline keratitis in which organisms are seen to reside within the stroma for up to 44 days without an inflammatory response. Periocular corticosteroids appear to be necessary to create this model. It is possible that the organisms are isolated from the host response by fibrin or by keratocytes.

Abscess↗
PubMed1991

Modified Schocket implant for refractory glaucoma. Experience of 55 cases.

Fifty-five eyes of 51 patients with different forms of refractory glaucoma (15 aphakic, 12 neovascular, 9 postpenetrating keratoplasty, 8 congenital, 5 secondary to uveitis, 4 associated with aniridia, 1 pseudophakic, and 1 traumatic) underwent antiglaucomatous surgery using a modified 90 degrees Schocket implant. In 25 eyes (45.4%), this was the first surgical procedure. Follow-up ranged from 3 to 27 months (mean, 10.3 +/- 5.4 months). The mean preoperative intraocular pressure (IOP) was 39.5 +/- 8.6 mmHg (range, 22 to 66 mmHg). The mean postoperative IOP was 17.8 +/- 7.6 mmHg (range, 4 to 50 mmHg). Intraocular pressure remained less than 21 mmHg in 50 eyes (90.9%) during the follow-up period. In 13 of these eyes (26.0%), IOP remained under control without any medication. Complications were observed in 13 eyes (23.6%) and were successfully treated in 11 of them. Complications included iris-tube block (5.4%), vitreous-tube block (3.6%), early postoperative flat anterior chamber (1.8%), choroidal effusion (3.6%), tube exteriorization from anterior chamber (3.6%), tube displacement from silicone band (1.8%), retinal detachment (1.8%), tube-cornea touch (1.8%), vitreous hemorrhage (1.8%), infectious endophthalmitis (1.8%), and phthisis bulbi (1.8%). Modified 90 degrees Schocket implants are an effective technique in the management of refractory glaucoma.

Adolescent↗
PubMed1991

Light and electron microscopic analysis of intraocular 2% hydroxypropylmethylcellulose.

Twenty samples of 2% hydroxypropylmethylcellulose for intraocular surgery, obtained from two Brazilian laboratories, were studied to determine the presence and type of impurities in the solutions. These were compared with ten samples of balanced salt solution (control group). Using light and scanning electron microscopy, five types of particles were identified: cellulose fibers, vegetable flakes, crystals, glass fragments, and other impurities. At least one of these contaminants was present in each sample of 2% hydroxypropylmethylcellulose. The vegetable matter was also seen in a sample of the raw material from which the clinical material had been prepared. Control solutions (i.e., balanced salt solution) were free of vegetable matter and of crystals, but glass fragments and other impurities were present. The average number of foreign particles in the solutions of hydroxypropylmethylcellulose (91.2 and 96.7 particles per milliliter for each of the two groups) was statistically greater than in the balanced salt solutions (13.7 particles per milliliter).

Drug Contamination↗