Biomedical subjects

M M Wright

Publications and source records attributed to M M Wright.

11 recordsLinked to original sources

PubMed1991

The physiologic characteristics of relative pupillary block.

In biometric photographs of 13 patients, we quantified the iris contour in eyes with central anterior chamber depths ranging from 1.9 to 3.4 mm (epithelium to lens surface). This actual profile was compared to that predicted by a theoretical analysis of the forces acting on the iris. The average discrepancy between the calculated actual and the theoretically predicted iris position was only -0.01 to +0.03 mm. The close agreement validates the model under normal conditions and in the presence of relative (nonsynechial) pupillary block. The theoretical iris shape may not occur under conditions that violate the underlying physical assumptions of the mathematical model, such as when iridectomy eliminates the pressure difference between the anterior and posterior chamber or when synechiae introduce additional forces on the iris other than the ones included in the analysis.

Anterior Chamber↗

PubMed1991

Measurement of intraocular pressure with a flat anterior chamber.

When a flat chamber develops in an eye after filtration surgery, management depends on whether the cause is excessive filtration or aqueous misdirection (ciliary block or malignant glaucoma). This diagnosis is often based on the intraocular pressure: low pressure in excessive filtration, high pressure in aqueous misdirection. To determine the accuracy of tonometry when the lens is in contact with the cornea, flat anterior chambers were created in 5 eyes obtained from an eye bank. The pressure in the vitreous cavity was raised and lowered with an infusion line and monitored with a pressure transducer. The intraocular pressure was estimated with a Goldmann applanation tonometer, a Pneumatonometer, and a Tono-pen. The readings poorly represented the actual pressure in the vitreous cavity. The error was 0 to 51 mmHg (mean, 12.8 mmHg) with the Goldmann tonometer, 0 to 33 mmHg (mean, 9.0 mmHg) with the Pneumatonometer, and 1 to 28 mmHg (mean, 13.5 mmHg) with the Tono-pen. Therefore, in the face of a flat anterior chamber, pressure measurements made on the cornea cannot be relied on to distinguish excessive filtration from aqueous misdirection.

Anterior Chamber↗

PubMed1991

5-Fluorouracil after trabeculectomy and the iridocorneal endothelial syndrome.

Nine patients (nine eyes) with iridocorneal endothelial (ICE) syndrome underwent trabeculectomy and received postoperative subconjunctival injections of 5-fluorouracil (5-FU) to enhance bleb formation (total 5-FU dose, 30-105 mg; mean, 53.8 mg). Eight eyes had undergone prior unsuccessful trabeculectomy. Four eyes had intraocular pressure (IOP) less than or equal to 21 mmHg on zero to two glaucoma medications after 6 to 54 months of follow-up (mean, 25.3 months). Five eyes required repeat surgery within 2 to 13 months and were considered failures. All five eyes that failed received a Molteno drainage implant. Progressive endothelial proliferation may explain late onset bleb failure and the relative ineffectiveness of 5-FU in this condition.

Adult↗

PubMed1991

Nd:YAG cyclophotocoagulation: outcome of treatment for uncontrolled glaucoma.

We reviewed the records of 35 patients (35 eyes) treated with Nd:YAG cyclophotocoagulation for uncontrolled glaucoma and followed for 6 to 36 months or until treatment was declared a failure (loss of light perception, or intraocular pressure (IOP) greater than 21 mm Hg). The mean pretreatment intraocular pressure was 37.9 mm Hg (range, 20 to 61 mm Hg). The total energy in the initial treatment session ranged from 50.4 to 372.4 J (191.7 +/- 66.3 J). After the treatment, the mean IOP was 21.2 mm Hg (range, 0 to 53 mm Hg). The Kaplan Meier survival analysis demonstrated that failures occurred throughout the follow-up period and that the majority of patients required further intervention or lost all vision if followed long enough. Visual outcome was not correlated with energy used. Eleven eyes (31%) lost two or more lines of acuity or lost all light perception. These findings suggest that Nd:YAG cyclophotocoagulation may control IOP but cannot always save vision.

Adolescent↗

PubMed1990

Time course of thymoxamine reversal of phenylephrine-induced mydriasis.

We conducted a randomized, double-masked, paired comparison of 0.1% thymoxamine vs placebo for the reversal of phenylephrine-induced mydriasis. Mydriasis was induced with 2.5% phenylephrine in each eye of 74 subjects (148 eyes). Each subject then received 0.1% thymoxamine in one eye and placebo in the other eye. Pupillary measurements were obtained at regular intervals during the ensuing 8 hours. At all intervals, a greater percentage of thymoxamine-treated eyes returned to baseline pupillary diameters compared with placebo-treated eyes (P less than or equal to .01). For subjects in whom both pupils returned to baseline, thymoxamine-treated eyes returned to baseline in a mean of 2.2 hours, vs 5.2 hours for placebo (P less than .0001). Among thymoxamine-treated eyes, those with light irides responded more rapidly than those with dark irides, returning to baseline in 1.6 vs 2.8 hours, respectively (P = .0046). After constriction to baseline pupillary diameter had been achieved, no patients experienced a rebound dilation.

Adolescent↗

PubMed1989

Efficacy of the primary dye test.

A primary dye test was performed on the right lacrimal system of 25 normal subjects by three physicians of differing levels of experience in performing the test. The frequency of positive primary dye tests for each of the three examiners was higher than previously reported. The most experienced examiner had the highest percentage (100%) of positive primary dye tests, and the least experienced examiner had the lowest percentage (80%) of positive tests. However, variation between the most experienced examiner and the other two was due, at least in part, to a difference in fluorescein instillation. Therefore, the effect of experience could not be ascertained. The most experienced examiner used four moistened fluorescein strips medially and each used a 10-minute interval after dye instillation before looking for evidence of dye passage through the nasolacrimal duct. Twenty-one (84%) of the subjects had a positive primary dye test on initial blowing of the nose. This indicates that even inexperienced examiners can expect to detect a high percentage of functioning lacrimal drainage system with the method of the experienced examiner.

Adult↗

PubMed1986