Biomedical subjects

P Rapoza

Publications and source records attributed to P Rapoza.

6 recordsLinked to original sources

PubMed1995

The combined (Genesis) technique of radial keratotomy. A prospective, multicenter study. Refractive Keratoplasty Study Group.

PURPOSE: A prospective, multicenter, clinical study to evaluate a standardized surgical (Genesis) protocol which includes combined-technique radial incisions in patients seeking reduction of their physiologic myopia. The combined incisions were designed to incorporate the safety of the centrifugal incision technique with the efficacy of the centripetal incision technique. METHODS: A total of 375 eyes undergoing radial keratotomy procedures performed in six different clinical centers were analyzed. All procedures were performed in accordance with the Genesis nomograms. The Genesis protocol called for using preoperative screening pachymetry to guide central clear zone size selection, incising the thinnest corneal quadrant first, suturing corneal perforations, and discouraged more than one enhancement procedure, when indicated. Globe fixation technique served as a study variable. RESULTS: Mean follow-up was 6.2 months (range, 1.5-12 months). Mean residual cycloplegic refraction was -0.48 +/- 0.61 diopters (D) (range, -2.50 to +1.50 D); 92% of eyes were within 1 D of the planned goal of -0.50 D and 85% were within 1 D of emmetropia; 14% were myopic; and 1% was hyperopic by more than 1 D. Uncorrected visual acuity was 20/40 or better in 95% of eyes; the remaining 5% retaining myopic refractive errors. A single procedure was performed in 73% of eyes, and 99% received less than two enhancements. Of eyes with no enhancements, 97% had uncorrected visual acuity of 20/40 or better. One study eye (0.3%) had a two-line loss of spectacle visual acuity. There were no invasions of the central clear zone. Globe fixation was a significant predictor for enhancement incidence (P < 0.001) but not for perforation incidence (P = 0.06). Incision sequence was predictive for perforation incidence (P < 0.0002). CONCLUSION: The combined-technique of radial keratotomy, coupled with the Genesis surgical protocol, affords centrifugal incision safety with centripetal incision efficacy. The Genesis nomograms, with a built in refractive outcome goal of -0.50 D provide an acceptable degree of accuracy and predictability while guarding against hyperopic overcorrection.

Adult↗

PubMed1994

Effectiveness of histocompatibility matching in high-risk corneal transplantation: a summary of results from the Collaborative Corneal Transplantation Studies.

The Collaborative Corneal Transplantation Studies (CCTS) were designed to evaluate the effect of donor-recipient histocompatibility matching and crossmatching on the survival of corneal transplants in high-risk patients. Corneas were allocated to the 419 patients in the double-masked Antigen Matching Study on the basis of HLA-A,-B and HLA-DR antigen match. ABO blood group compatibility was determined but not used for recipient selection. The 37 patients in the Crossmatch Study were randomly assigned to receive a cornea from either a positively or negatively crossmatched donor. All patients received topical steroid therapy according to a standard protocol. Matching for HLA-A,-B and HLA-DR antigens had no effect on overall graft survival, the incidence of irreversible rejection, or the incidence of rejection episodes. The positive group in the Crossmatch Study had fewer graft failures, rejection failures, and rejection episodes than the negative group; however, these differences were not statistically significant. The estimated proportion of eyes with failure from rejection by 3 years was 30% for the ABO-incompatible group and 16% for the ABO-compatible group (relative risk, 1.98; 95% confidence interval, 1.15 to 3.13). These studies demonstrate that, for high-risk patients who are immunosuppressed by topical steroid therapy: 1) neither HLA-A.-B nor HLA-DR antigen matching substantially reduced the likelihood of corneal graft failure; 2) a positive donor-recipient crossmatch did not increase the risk of corneal graft failure; and 3) ABO blood group matching may be effective in reducing the risk of graft failure from rejection.

ABO Blood-Group System↗

PubMed1991

Epidemiology of ocular chlamydial infection in a trachoma-hyperendemic area.

The epidemiology of ocular chlamydial infection in a trachoma-hyperendemic area of Tanzania was investigated. Specimens for chlamydial isolation cultures and direct fluorescent antibody cytology were collected from 1085 children aged 1-7 years. Other data included examinations for signs of clinical trachoma and the collection of household data on risk factors. A total of 33% of children had a positive laboratory test for Chlamydia species. The most important factors for predicting chlamydial infection were the presence of a sibling with laboratory evidence of infection, increased number of flies around the house, a household that herded cattle, and practice of a local religion. Younger children and girls were at no increased risk for a positive laboratory test, although these subgroups have more clinical disease. The data are compatible with a model of less frequent episodes of reinfection as children become older.

Age Factors↗

PubMed1989

Water availability and trachoma.

As part of an epidemiological survey of risk factors for trachoma in 20 villages in the United Republic of Tanzania, we investigated the relationship of village water pumps, distance to water source, and quantity of household water to the risk of inflammatory trachoma. We also evaluated whether there was an association between the cleanliness of children's faces and these water variables. No association was found between the presence of a village water supply and the prevalence of trachoma. However, the risk of trachoma in the household increased with the distance to a water source--although there was no association with the estimated daily amount of water brought into the house. Likewise, children were more likely to have unclean faces if they lived more than 30 minutes from a water source, but whether they had clean faces was not associated with the daily quantity of water brought into the household. The effect of the distance to water supply on trachoma may well reflect the value placed on water within the family, and this determines the priority for its use for hygiene purposes. The results of the study suggest that changing the access to water per se may be insufficient to alter the prevalence of trachoma without also a concomitant effort to change the perception of how water should be utilized in the home.

Child↗

PubMed1988

The diagnosis and treatment of chlamydial conjunctivitis.

Chlamydial conjunctivitis will usually go unrecognized and therefore untreated unless it is specifically considered. The possibility of chlamydial infection must be borne in mind in neonatal conjunctivitis, in acute conjunctivitis in sexually active adults, and in chronic follicular conjunctivitis. Chlamydial conjunctivitis is often indistinguishable from other forms of conjunctivitis on clinical grounds, and accurate diagnosis is based on laboratory tests. It seems that direct fluorescent antibody (DFA) cytology offers an attractive alternative to the more complicated and time-consuming tissue culture isolation method. Once diagnosed, chlamydial infection should be treated with the appropriate systemic antibiotics, and proper posttreatment follow-up is necessary to assess the efficacy of treatment.

Chlamydia Infections↗

PubMed1986

Respiratory arrest following retrobulbar anesthesia.

Respiratory arrest is a serious complication of retrobulbar anesthesia. We have prospectively followed 3123 retrobulbar injections to determine the incidence of respiratory arrest and identify possible risk factors. Injections contained either 2% or 4% lidocaine with 0.75% bupivacaine (Marcaine) in a 50:50 mixture by volume (total 10 cc.) to which a 1 ml ampule of hyaluronidase (150 NF units) was added. Use of 4% lidocaine gave a significantly higher incidence of respiratory arrest than 2% lidocaine (0.79% vs. 0.09%; P = 0.003, Fisher's exact test). Serum levels of lidocaine and bupivacaine of patients who arrested were not elevated significantly compared to 20 control patients. All levels were well below accepted levels of toxicity. Thus, 4% lidocaine increases the risk of respiratory arrest. These results suggest the mechanism is not direct intravascular or central nervous system injection.

Adult↗