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Biomedical subjects

A L Coleman

Publications and source records attributed to A L Coleman.

34 records · Page 2Linked to original sources
PubMed1996

Determination of the real size of fundus objects from fundus photographs.

PURPOSE: The purpose of this research was to study the accuracy of measurements that rely on Littmann curves to determine the real size of fundus images. METHODS: Retinal tacks of known dimensions were placed near the optic disc in one eye of each of two cynomolgus monkeys. Images of the retinal tack and optic nerve head of these two eyes were then obtained with a Zeiss Fundus camera. The dimensions of the retinal tacks and optic discs were measured directly on the film from the Zeiss fundus camera. These measurements were then corrected with Littmann's mathematical approximations. RESULTS: In the cynomolgus eye with 19.9 mm axial length, Littmann's mathematical approximations of the real sizes of the retinal tack and optic disc from measurements on the Zeiss film had median percent bias [(calculated size-real size)/real size] of -0.2% (range, -3.2% to 3.9%). In the other eye with 17.9 mm axial length, the median percent bias was 14.7% (range, 5.1% to 29.7%). CONCLUSION: The estimation of the real size of fundus images with Littmann's mathematical approximations from images on Zeiss film have < 4% bias if the eye's dimensions fall in the range over which Littmann's curves were produced.

Animals↗
PubMed1995

Initial clinical experience with the Ahmed Glaucoma Valve implant.

PURPOSE: We studied the Ahmed Glaucoma Valve implant, an aqueous shunting device that has a unidirectional valve mechanism designed to prevent postoperative hypotony in eyes with intractable glaucoma. METHODS: In this multicenter, prospective clinical trial, we studied 60 eyes (60 patients) with increased intraocular pressure or glaucoma that had not responded to medical treatment, laser photocoagulation, or previous glaucoma surgery, in which the Ahmed Glaucoma Valve implant was placed to decrease intraocular pressure. RESULTS: Success was defined as intraocular pressure less than 22 mm Hg and greater than 4 mm Hg for two months or longer, intraocular pressure that was lowered by at least 20% from preoperative values (in eyes with preoperative intraocular pressures less than 22 mm Hg), and no additional glaucoma surgery or visually devastating complications. Cumulative probability of success at 12 months was 78%. Eight (13%) of 60 eyes had intraocular pressure less than 5 mm Hg the first postoperative day. Two other eyes had shallow anterior chambers, which required anterior chamber reformation. The major complications associated with the use of the valve were serous choroidal detachments in 13 eyes (22%), blockage of the tube in six eyes (10%), malposition of the tube in four eyes (7%), a suprachoroidal hemorrhage in one eye (2%), and corneal graft rejections in three (19%) of 16 eyes with corneal grafts. CONCLUSIONS: Although the 12-month success with the Ahmed Glaucoma Valve implant is similar to that reported for other drainage devices, the complications associated with overfiltration in the immediate postoperative period appear to be less frequent than with other valved drainage devices. Randomized, prospective studies to compare the Ahmed Glaucoma Valve implant with other drainage devices are needed to make clinical comparisons of the different devices.

Adult↗
PubMed1993

The efficacy of brimonidine in decreasing elevations in intraocular pressure after laser trabeculoplasty.

PURPOSE: The authors explored the empirical dosing requirement for administration of an alpha 2-adrenoceptor agonist, brimonidine, and determined its efficacy in decreasing elevations in intraocular pressure (IOP) after 360 degrees argon laser trabeculoplasty (ALT). METHODS: This vehicle-controlled, double-masked, multicenter trial evaluated three dosing regimens of brimonidine. Two hundred thirty-two patients for whom 360 degrees ALT was indicated were randomized into one of four treatment groups: 0.5% brimonidine both before and after ALT; brimonidine before but vehicle after ALT; vehicle before but brimonidine after ALT; or vehicle at both times. RESULTS: During the first 3 hours after 360 degrees ALT, the overall incidence of IOP elevations of 5 mmHg or greater was 38% (23 of 60 eyes) in the group receiving vehicle only, and it ranged from 3% to 9% (2 of 62 to 5 of 53 eyes) in the groups receiving any brimonidine treatment. There was little difference in efficacy between the three dosing regimens of brimonidine. Brimonidine was well tolerated by the patients. CONCLUSION: Based on this large, controlled, multicenter study, 0.5% brimonidine was an effective agent for reducing elevations in IOP after 360 degrees ALT. Only one dose, administered either before or after 360 degrees ALT, was required.

Adrenergic alpha-Agonists↗
PubMed1992

Once-daily versus twice-daily levobunolol (0.5%) therapy. A crossover study.

The authors executed a two-period, randomized, double-masked, crossover study comparing once-daily to twice-daily levobunolol hydrochloride (0.5%) in 20 patients with elevated intraocular pressure (IOP). Modified diurnal curves were performed at four times for each study arm: baseline, day 1, day 14, and day 28. The mean diurnal corrected decrease in IOP from baseline ranged from 16% +/- 11% to 22% +/- 9% when the subjects were treated twice daily, and from 14% +/- 10% to 18% +/- 8% when the same subjects were treated once daily. At day 1, patients had a significantly greater IOP lowering after twice-daily therapy than after once-daily therapy (P less than 0.05). At 14 and 28 days, there was no clinically significant difference between the two treatment regimens. The results of our crossover study suggest that once-daily treatment with levobunolol (0.5%) is as effective as twice-daily treatment.

Adult↗
PubMed1991

Larger optic nerve heads have more nerve fibers in normal monkey eyes.

The cup-to-disc ratio and the neural rim area are used to detect glaucoma damage to the optic nerve. Both parameters are dependent on the size of the optic disc and on the number of optic nerve fibers. We compared the size of the disc in fundus photographs with the number of nerve fibers in 25 normal monkey eyes. The number of fibers increased linearly with an increasing disc area. One must know the size of the optic disc to evaluate properly the cup-to-disc ratio or neural rim area.

Animals↗
PubMed1991

Displacement of the optic nerve head by acute changes in intraocular pressure in monkey eyes.

The authors used the Humphrey Retinal Analyzer to study the effect of acute changes in intraocular pressure (IOP) on the topography of the optic nerve head in normotensive and hypertensive eyes of cynomolgus monkeys. Chronically elevated IOP was produced monocularly in monkeys by argon laser angle treatment. In 8 hypertensive eyes, the mean IOP of 51 mmHg was lowered acutely to 15 mmHg with a needle placed in the anterior chamber. In 12 normotensive eyes, the mean IOP of 16 mmHg was similarly increased to 45 mmHg. Simultaneous stereophotographs were taken both before and within 15 minutes after the IOP change. The surface of normotensive optic nerve heads moved posteriorly a mean of 17.8 microns after IOP elevation (P less than 0.02). The surface of hypertensive optic nerve heads moved anteriorly 47.4 microns after IOP lowering (P = 0.1); this change was significantly less in nerve heads with larger and deeper cups (P less than 0.02). Significant changes were not detected in disc diameter or vein diameter with acute changes in IOP. Measurable shifts in the position of the optic nerve head surface when IOP is altered may provide a future prognostic test for glaucomatous optic neuropathy.

Animals↗
PubMed1991

Transscleral cyclophotocoagulation of human autopsy and monkey eyes.

We studied the effect of uveal pigmentation on contact Nd:YAG transscleral cyclophotocoagulation in 36 human autopsy and eight cynomolgus monkey eyes. Ten autopsy eyes from black individuals required less energy to create a lesion than 23 eyes from whites. The mean lesion diameter at the posterior pars plicata was similar in all these eyes; however, the mean energy required was 4.4 J in the black and 6.4 J in the white eyes. Transscleral cyclophotocoagulation lowered intraocular pressure (IOP) in four monkey eyes with elevated IOP, but did not in four other eyes without elevated IOP. Treatment over conjunctival pigmentation burned the conjunctiva, even at the lowest energy tested (3.5 J). Contrary to other investigators' findings, transmission electron microscopy showed at least short-term loss of scleral architecture in both the human autopsy and monkey eyes.

Animals↗
PubMed1990

Topical timolol decreases plasma high-density lipoprotein cholesterol level.

beta-Adrenergic antagonists taken orally adversely alter plasma lipid profiles. This study was designed to determine whether 0.5% topical timolol maleate has a similar effect. Forty volunteers who were not using medications known to alter plasma lipid levels were recruited for an unmasked study in which each subject served as his or her own control. Twelve subjects did not complete the study because of ocular and systemic side effects or extraneous factors. Twenty-eight subjects used topical timolol for an average of 76 days, with two 12-hour fasting plasma specimens obtained at the beginning and end of the period. Mean total cholesterol and low-density lipoprotein cholesterol levels did not change significantly with treatment. Triglyceride values increased 12%; high-density lipoprotein cholesterol levels decreased 9%; and the total cholesterol-high-density lipoprotein cholesterol ratio increased 8%. Higher baseline high-density lipoprotein cholesterol levels were associated with larger reductions in high-density lipoprotein cholesterol levels. Changes in high-density lipoprotein cholesterol levels of this magnitude have been estimated to increase the risk of coronary artery disease by 21%.

Administration, Topical↗
PubMed1990

Cardiovascular and intraocular pressure effects and plasma concentrations of apraclonidine.

We performed a double-masked, crossover study comparing the cardiovascular and intraocular pressure effects of 0.5% and 0.25% topical apraclonidine hydrochloride and 0.5% timolol maleate in 20 healthy female volunteers. The contralateral effects of unilateral apraclonidine and the plasma concentrations of apraclonidine were also assessed. All measurements were done 2, 5, and 8 hours after drop instillation. A 15-minute treadmill test was performed after the 2-hour measurements. All three active medications lowered intraocular pressure comparably. There was no significant contralateral intraocular pressure effect seen with apraclonidine. The apraclonidine plasma concentrations were variable and unrelated to the amount of intraocular pressure lowering and cardiovascular parameters measured. Apraclonidine did not affect blood pressure or heart rate any differently than placebo. Timolol, however, blunted exercise-induced tachycardia. There were no significant differences in pupillary diameters or interpalpebral fissure widths among treatment groups.

Administration, Topical↗
PubMed1990

Apraclonidine hydrochloride: an evaluation of plasma concentrations, and a comparison of its intraocular pressure lowering and cardiovascular effects to timolol maleate.

We performed a prospective, placebo-controlled, cross-over study in 20 young healthy female volunteers. We evaluated both the cardiovascular and IOP effects of both timolol maleate and apraclonidine hydrochloride. In addition, we evaluated the plasma levels of various apraclonidine concentrations. We utilized 0.5% timolol and both the 0.25% and 0.50% concentrations of apraclonidine. Both timolol and apraclonidine lowered IOP comparably. Timolol lowered the resting pulse rate and blunted exercise-induced tachycardia. Apraclonidine did not affect blood pressure or heart rate any differently than placebo. We detected plasma levels of apraclonidine in many individuals for up to 8 hours. These serum levels were variable and did not appear to relate to the quantity of IOP lowering.

Adrenergic alpha-Agonists↗
PubMedDate not supplied

Use of insurance claims databases to evaluate the outcomes of ophthalmic surgery.

This article reviews methodological issues in research using Medicare claims data and reviews how those issues affect the interpretation of study results. Although studies using Medicare claims data can improve our knowledge of surgical outcomes, the ability to infer that one type of surgery or one surgeon is better than another is limited by such factors as bias due to inaccurate record keeping, confounding of treatment effects by other covariates, effect modification due to factors associated with treatment, and selective loss of follow-up of patients. Five studies on the outcomes of cataract surgery and capsulotomy are reviewed, providing illustrations of methodological strengths and weaknesses of this type of research.

Aged↗