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Biomedical subjects

M Lynn

Publications and source records attributed to M Lynn.

At least 19 recordsLinked to original sources
PubMed1996

The effect of photorefractive keratectomy on the corneal endothelium.

PURPOSE: The authors prospectively investigated the effect of excimer laser photorefractive keratectomy (PRK) for myopia on the corneal endothelium. METHODS: Quantitative computer-assisted morphometric analysis of central and peripheral corneal endothelial cells was performed on 142 myopic eyes before and at 3 months, 1 year, and 2 years after PRK. The mean age of the subjects was 37 years (range, 21-66 years). Ninety-one (64%) of them had a history of contact lens wear. Mean attempted correction was -3.9 diopters (range, -1.6 to -6.0 diopters). RESULTS: The mean preoperative endothelial cell density was 2660 cells/mm2 centrally and 2776 cells/mm2 peripherally. There was no change in central endothelial cell density at any of the postoperative examinations. The peripheral cell density decreased 4.1% (P = 0.003) at 3 months and 6.2% (P = 0.0001) at 1 year. However, the peripheral cell density was not significantly different from the preoperative value at 2 years. The peripheral coefficient of variation of cell size was 7.8% lower 2 years postoperatively than it was preoperatively, and this improvement was attributable to cessation of contact lens wear after PRK. The decrease in peripheral endothelial cell density at 1 year correlated with the amount of attempted correction, but there was no correlation between attempted correction and the change in central or peripheral endothelial cell density 2 years postoperatively. CONCLUSION: For the correction of up to 6.0 D of myopia, PRK causes no detectable changes in central corneal endothelial cell density, but it does cause a transient, modest loss of peripheral corneal endothelial cells at 1 year. Variations in endothelial cell shape caused by contact lens wear resolve after PRK.

Adult↗
PubMed1996

Ciliary body endophotocoagulation during pars plana vitrectomy in eyes with vitreoretinal disorders and concomitant uncontrolled glaucoma.

PURPOSE: To investigate the efficacy of ciliary body endophotocoagulation during pars plana vitrectomy in eyes with medically uncontrolled glaucoma and concomitant vitreoretinal disorders. METHODS: The authors compared preoperative and postoperative intraocular pressure (IOP) and visual acuity in 21 eyes of 21 patients undergoing ciliary body endophotocoagulation with pars plana vitrectomy. RESULTS: Preoperative IOPs ranged from 22 to 59 mmHg (median, 46 mmHg). Visual acuity ranged from 20/200 to light perception (median, hand motions). Follow-up ranged from 3 to 18 months (median, 10 months). Postoperative IOPs ranged from 11 to 19 mmHg (median, 16 mmHg) at 6 weeks, 4 to 20 mmHg (median, 14 mmHg) at 3 months, 1 to 26 mmHg (median, 12 mmHg) at 6 months, and 0 to 48 mmHg (median, 12 mmHg) at 12 months. Postoperative visual acuity was statistically improved from preoperative visual acuity by 6 weeks. CONCLUSION: Ciliary body endophotocoagulation combined with pars plana vitrectomy can effectively treat concomitant glaucoma and vitreoretinal disorders.

Adult↗
PubMed1996

Donor factors associated with epithelial defects after penetrating keratoplasty.

The records of 39 patients undergoing 40 consecutive penetrating keratoplasties were reviewed to identify donor factors that might correlate with the presence of an epithelial defect on the first postoperative day. Of the 40 transplanted corneas, 13 (32.5%) had no epithelial defect, 18 (45%) had some epithelial defect, and nine (22.5%) had a total epithelial defect 1 day postoperatively. The status of the epithelium was correlated with several donor factors. The only factor that had a statistically significant association with the degree of epithelial defect was the time interval from preservation to surgery (p = .001). Based on a logistic regression model, the probability of having an epithelial defect 1 day after penetrating keratoplasty increased with respect to longer storage times. These results may aid the surgeon in the selection of donor tissue, particularly when performing penetrating keratoplasty on patients with ocular surface disorders.

Adolescent↗
PubMed1995

Case report: mannitol nephrotoxicity syndrome: role of hemodialysis and postulate of mechanisms.

High-dose intravenous mannitol infusion in various clinical settings may result in acute renal failure (ARF). This form of ARF is characteristically anuric and follows a distinctive clinical course. Most importantly, it occurs only after high doses of mannitol (> 200 g/day or cumulative dose of > 400 g in 48 hours), but not at lower doses. It appears that a low dose of mannitol acts as a renal vasodilator while high-dose mannitol is renal vasoconstrictor. Mannitol-induced ARF responds promptly to hemodialysis with rapid resolution of anuria and recovery of renal failure. This is a report of a case of anuric ARF after high-dose mannitol infusion for treatment of narrow-angle glaucoma that readily responded to acute hemodialysis. The literature is also reviewed for ARF associated with mannitol infusion in patients who received dialysis and those who did not receive dialysis; and the possible mechanism(s) of mannitol nephrotoxicity are discussed. Hemodialysis should be performed for rapid reversal of mannitol-induced ARF. Patients not treated with hemodialysis have increased morbidity and significant prolongation of their hospital course.

Acute Kidney Injury↗
PubMed1994

Corneal endothelial permeability of human tissue after storage in Optisol.

The purpose of this study was to compare Optisol to moist chamber storage for maintaining human corneal endothelial barrier function. Human corneas preserved in Optisol were stored for up to 35 days at 4 C. Endothelial carboxyfluorescein permeability (P(ac)) was measured and endothelial ultrastructure was evaluated by electron microscopy. Endothelial P(ac) (x 10(-4) cm/min) of Optisol-stored corneas was 1.7, 2.0, and 3.1 at five, seven, and 14 days, respectively. The P(ac) increased to 6.5 at 35 days of storage. Endothelial P(ac) in moist chamber stored-eyes was 2.6 at two days, and increased to 13.5 14 days of storage. Multiple regressional analysis showed that storage time and donor age affected P(ac); but time from death to enucleation, time from enucleation to storage, or endothelial cell number did not. Electron microscopy showed that endothelial junctions were maintained through two weeks by Optisol. Large areas of cellular destruction were seen after five days of moist chamber storage. These results show that Optisol can preserve endothelial barrier function through 14 days; barrier function is lost by three days of moist chamber storage.

Adult↗
PubMed1994

Conservative treatment of early-stage breast cancer. The Emory experience.

Between January 1983 and December 1991, 80 women with AJCC clinical stage I or II breast cancer were treated with conservative surgery and radiation therapy. Reexcision of the primary was performed in 40 breasts, and residual tumor was identified in 40% of these. Margins of resection were assessed in 80% and, of these, 46 patients had final margins of resection that were negative, 86% had axillary node dissection, 45 patients had histologically negative axillary nodes, and 24 had histologically positive axillary nodes. Of patients with histologically positive lymph nodes, 92% received systemic adjuvant treatment consisting of chemotherapy in 19/24 and tamoxifen in 14/24. Median follow-up was 34 months (range: 6-90 months). The adjusted 5-year actuarial Overall Survival for the group was 92%, and Disease-Free Survival was 80%. The 5-year Local Recurrence-Free Survival was 96%. The present study confirms the excellent results that can be obtained with conservative surgery plus radiation therapy.

Adult↗
PubMed1993

Acute behavioral and cardiac effects of cocaine and alcohol combinations in humans.

Subjects received acute doses of orally administered alcohol (0-1.0 g/kg) and intranasal cocaine (4-96 mg/70 kg) alone and in combination in two experiments. Results generally were consistent across both experiments. Cocaine administered alone improved Digit Symbol Substitution Test (DSST) performance, increased subject ratings of stimulant-like effects, heart rate and blood pressure, and decreased skin temperature. Alcohol administered alone disrupted DSST performance, increased ratings of drunkenness, heart rate and skin temperature, and decreased blood pressure. Combining cocaine and alcohol attenuated the disruptions in DSST performance observed with alcohol alone, and either did not change or attenuated the improvements in performance observed with cocaine alone. Combining the drugs also attenuated effects observed with the drugs alone on skin temperature and, to a lesser extent, blood pressure. By contrast, drug combinations increased heart rate above levels observed when cocaine or alcohol were administered alone. Effects of the drug combinations on subject ratings were variable.

Administration, Intranasal↗
PubMed1993

Preoperative irradiation and fluorouracil chemotherapy for locally advanced rectosigmoid carcinoma: phase I-II study.

From June 1988 to July 1991, 20 patients with locally advanced rectal or rectosigmoid cancer were treated prospectively with a strategy of combining preoperative irradiation and fluorouracil chemotherapy before surgical resection. The preoperative radiation dose was 5,000 cGy, and fluorouracil chemotherapy was administered on the first and last 3 days of irradiation in an intravenous bolus dose of 500 mg/m2. In a median follow-up of 25 months, the local regional failure rate was 10%. The 3-year actuarial overall survival and disease-free survival were 92% and 82%, respectively. Twenty percent of the surgical specimens showed no residual tumor, and only 10% showed positive lymph nodes. Significant leukopenia occurred in 10% of patients. Preoperative irradiation and fluorouracil chemotherapy increased surgical downstaging and improved local regional control. The overall toxicity was acceptable. The results of this particular multimodality approach was encouraging and warrant further investigation in phase III trials.

Adult↗
PubMed1992

Effects of cocaine and alcohol, alone and in combination, on human learning and performance.

The acute effects of cocaine hydrochloride (4 to 96 mg/70 kg) and alcohol (0 to 1.0 g/kg), administered alone and in combination, were assessed in two experiments with human volunteers responding under a multiple schedule of repeated acquisition and performance of response chains. Subjects were intermittent users of cocaine and regular drinkers who were not cocaine or alcohol dependent. Alcohol was mixed with orange juice and ingested in six drinks within 30 min; cocaine was administered intranasally 45 min after completion of drinking. In each component of the multiple schedule, subjects completed response sequences using three keys of a numeric keypad. In the acquisition component, a new sequence was learned each session. In the performance component, the response sequence always remained the same. Results were consistent in both experiments, despite variations in the order in which the drugs were tested alone and in combination. Alcohol administered alone increased overall percentage of errors and decreased rates of responding in the acquisition component, whereas responding in the performance component generally was unaffected. Cocaine administered alone decreased rates of responding but did not affect accuracy of responding in the acquisition component, and enhanced accuracy of responding without affecting rates of responding in the performance component. The combined doses of cocaine and alcohol attenuated the effects observed with alcohol and cocaine alone. These results suggest that, under the conditions investigated in this study, (a) alcohol produces greater behavioral disruption than cocaine or cocaine-alcohol combinations, (b) cocaine and alcohol each attenuate effects of the other, and (c) such attenuation is most pronounced for cocaine attenuating the disruptive effects of alcohol.

Adult↗
PubMed1990

Effects of intranasal cocaine on human learning, performance and physiology.

The behavioral and physiological effects of intranasally administered cocaine (placebo, 48, 96 mg/70 kg) were examined in eight recreational cocaine users under controlled laboratory conditions. The 48 and 96 mg doses of cocaine significantly improved subjects' performance on the Digit Symbol Substitution Test above levels observed either prior to drug administration or when placebo was administered. These effects were discernible for up to 120 min after cocaine administration. Cocaine had no statistically significant effects on learning and performance of ten-response sequences. The 48 and 96 mg doses increased heart rate and blood pressure for up to 180 min, and increased subject ratings of drug effects and decreased skin temperature for 60-90 min after drug administration. Cocaine produced no significant effects on the electrocardiogram. To our knowledge, this is the first experimental demonstration that acutely administered cocaine can improve behavioral performance in rested subjects. In addition, the duration of cardiac effects in this study was longer than previously reported with intranasal cocaine, perhaps due to the concurrent behavioral testing.

Administration, Intranasal↗
PubMed1989

Accuracy and reproducibility of KeraScanner analysis in PERK corneal topography. PERK Study Group.

The measurement of the corneal radius of curvature centrally and in the corneal periphery is exceedingly difficult because of variables in photography and data acquisition. We present a technique of Automated image scanning of corneal photographs which provides a more accurate and reproducible analysis of the paracentral corneal contour. We analyzed the sources of error of corneal topography measurement. CorneaScope photographs of calibration balls were generated by each Prospective Evaluation of Radial Keratotomy (PERK) Surgical Center. The 90% confidence intervals for individual ring-radial positions on the 8.00 and 10.00 mm balls were 7.91 to 8.09 mm and 9.89 to 10.11 mm respectively. Our isopter method of analysis for clinical comparison averages all eight radii of curvature for each CorneaScopef ring. This isopter technique reduces the corresponding 90% confidence intervals to 7.96 to 8.03 and 9.95 to 10.06 mm. The measurement variability of a 10 mm calibration ball decreased in the following order: calibration ball positioning, scanner personnel, photograph movement between scans, and nonrepositioned scanning. Photographs of calibration balls demonstrate +/- 4 microns of measurement resolution and patient corneal photographs may be evaluated to +/- 40 microns. This automated scanning system provides consistent data when digitizing keratographs.

Biometry↗
PubMed1988

Relationship of glare to uncorrected visual acuity and cycloplegic refraction 1 year after radial keratotomy in the prospective evaluation of radial keratotomy (PERK) study.

This study examines the relationship of subjective glare to refraction and visual acuity, respectively, 1 year after surgery in 435 patients who underwent radial keratotomy for nearsightedness in the Prospective Evaluation of Radial Keratotomy (PERK) study. Patients were asked if they experienced glare in bright light. Of the 425 responding, 200 patients responded "no" and 225 patients responded "yes." We found no statistically significant difference in the mean value of the cycloplegic refraction 1 year after surgery in these two patient groups. (Mean cycloplegic refraction: no = -.48, yes = -.52, p = .73). We also found no difference between these groups with respect to the percent of patients with uncorrected visual acuity of 20/40 or better 1 year after surgery (no = 79%, yes = 76%, p = .46).

Clinical Trials as Topic↗
PubMed1987

An endoscopic comparison of the effects of etodolac, indomethacin, ibuprofen, naproxen, and placebo on the gastrointestinal mucosa.

To assess the effects of various nonsteroidal antiinflammatory drugs on gastroduodenal mucosa, 72 normal men were administered either etodolac, indomethacin, ibuprofen, naproxen, or placebo for 7 days. Gastric and duodenal mucosa were scored before and after treatment by direct endoscopy and evaluation of photographs taken during endoscopy. Subjects treated with indomethacin, ibuprofen, and naproxen had significantly worse direct gastric scores, and those treated with indomethacin and naproxen also had significantly worse direct duodenal scores, when compared with pre-treatment and placebo scores. Subjects given either of 2 doses of etodolac had gastric and duodenal scores comparable to pretreatment and placebo scores. The direct gastric scores of the etodolac groups were significantly better than the scores of subjects receiving indomethacin, ibuprofen and naproxen. Similar results were obtained when endoscopy photographs were scored.

Acetates↗
PubMed1987

Laboratory test results as predictors of recurrent coronary artery stenosis following angioplasty.

A retrospective study has been conducted to examine the potential value of a battery of selected clinical laboratory tests as predictors of recurrent coronary artery stenosis following angioplasty. Data from 443 patients (including 325 men and 118 women) who had undergone coronary angioplasty were analyzed. Total men, total women, aspirin-treated men, and aspirin-treated women received separate statistical treatment. The only statistically significant difference in mean laboratory values between success (no recurrent stenosis) and recurrence groups was for serum cholesterol in aspirin-treated women, where the recurrence group showed a higher value than the success group. Multiple logistic regression showed a statistically significant association between elevated mean cholesterol and low mean hemoglobin concentration and recurrence in the female aspirin-treated group. Although only a small number of the laboratory test results fell outside normal laboratory reference ranges, we noted that for some tests, patients with extreme values predominantly developed recurrent stenosis while for certain other tests they were mainly successful. For example, seven of eight male diabetics with plasma glucose concentrations above 9.4 mmol/L (170 mg/dL) developed recurrence, while recurrent stenosis did not occur in any of six men with a bleeding time greater than twice normal. The results of these studies do not support the hypothesis that lipoprotein, coagulation, and platelet factors influence the development of recurrent stenosis in the majority of patients, although abnormalities in certain of these parameters may contribute to the process in specific cases.

Aged↗
PubMed1986

Reported satisfaction, fluctuation of vision, and glare among patients one year after surgery in the Prospective Evaluation of Radial Keratotomy (PERK) Study.

We studied satisfaction with the results of radial keratotomy one year after surgery on one eye as reported by 354 patients in the Prospective Evaluation of Radial Keratotomy (PERK) Study. We measured satisfaction using an index based on ten questions that were part of a longer psychometric questionnaire. Patients were generally satisfied with the results of radial keratotomy-48% were very satisfied, 42% were moderately satisfied, and 10% were dissatisfied. A lot of trouble with fluctuating vision was reported by 12% of patients before surgery and by 34% one year after surgery; 17% reported a lot of trouble with glare both before surgery and one year after surgery. The three major factors that influenced satisfaction were uncorrected visual acuity, residual refractive error, and subjective daily fluctuation in vision. A multiple regression equation that incorporated these three variables, glare, and patient sex was able to predict only 46% of the variance in patient satisfaction.

Adult↗
PubMed1986

Comparison of ultrasonic corneal thickness measurements before and during surgery in the prospective evaluation of Radial Keratotomy (PERK) Study.

Central corneal thickness, determined by an ultrasonic pachymeter, was studied in one eye each of 395 patients enrolled in the Prospective Evaluation of Radial Keratotomy (PERK) Study, to determine the changes in central corneal thickness between preoperative and intraoperative measurements. There was no statistical difference between the preoperative and the intraoperative measurement. However, 9.4% of the corneas were 0.03 to 0.08 mm thinner intraoperatively and 3.3% were 0.03 to 0.06 mm thicker intraoperatively, indicating that clinically meaningful changes in corneal thickness occurred between the preoperative and intraoperative measurements in some eyes. We conclude that the most reliable way to use ultrasonic pachymetry readings to set the length of the knife blade for radial keratotomy surgery is to measure the corneal thickness intraoperatively.

Cornea↗