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Biomedical subjects

R K Parrish

Publications and source records attributed to R K Parrish.

At least 19 recordsLinked to original sources
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↗
PubMed1990

Contact B-scan echography in the assessment of optic nerve cupping.

We determined the reliability of high-resolution contact B-scan echography for estimating the optic cup size in 56 eyes of 28 patients with glaucoma or ocular hypertension. Two trained observers independently evaluated horizontal and vertical cup/disk ratios in stereophotographs, and two skilled echographers independently estimated optic cup size in photoechograms in a masked fashion. The reliability of echographic interpretation varied (kappa 0.29 to 0.71), but it always exceeded that expected by chance alone, even for cups of 0.3 disk diameter or less. Subtly saucer-shaped cups (three of 50 eyes) and deep cups with intact neuroretinal rims (two of 50 eyes) were misinterpreted echographically. High-resolution contact B-scan echography may provide a useful and reliable estimate of the optic cup size in eyes with opaque media.

Fundus Oculi↗
PubMed1990

A prospective study of angiographic cystoid macular edema one year after Nd: YAG posterior capsulotomy.

We prospectively studied 120 eyes with intact opacified posterior capsules in 120 consecutive patients to determine the incidence of new late-onset angiographic cystoid macular edema (CME) after neodynium: yttrium aluminum garnet (Nd:YAG) laser posterior capsulotomy. Fifty-seven of 120 patients (48%) had both precapsulotomy and one-year post-capsulotomy angiograms done. Of these 57 patients, three eyes had angiographic CME before capsulotomy and two of these three cases had persistent CME one year after capsulotomy. In the other 54 patients, three new late-onset cases occurred (5.6%). Because the incidence of postcapsulotomy new CME was low, the statistical significance of possible risk factors, such as rupture of the anterior hyaloid face or pseudophakic status cannot be determined. However, aphakic patients with vitreous prolapse after capsulotomy tended to have a higher incidence to CME than pseudophakic patients. We recommend fluorescein angiography to identify occult CME in cases of unexplained visual-acuity decrease after capsulotomy.

Aged↗
PubMed1987

Noncontact trephination of the cornea using a pulsed hydrogen fluoride laser.

We used a pulsed hydrogen fluoride infrared laser and a specially designed axicon lens to perform circular corneal trephinations in ten eye bank eyes. This noncontact system focused each laser pulse into an annulus on the cornea. Corneal perforation was achieved in seven to nine seconds at a repetition rate of 10 Hz, using a laser output energy of 100 mJ per pulse. A trephination, 90% of corneal thickness, 6.5 mm in diameter, was produced with 70 pulses.

Cornea↗
PubMed1987

Zonular dialysis during extracapsular cataract extraction in pseudoexfoliation syndrome.

Five patients with pseudoexfoliation syndrome (PES) and glaucoma developed extensive zonular dialyses during extracapsular cataract extractions. Weakness of the lens zonules or their attachments to the ciliary processes, which has been described in association with PES, may explain this complication. We believe that patients with PES are at particular risk for developing large zonular dialyses during extracapsular surgery. Preoperative phakodonesis, anterior chamber depth asymmetry, and excessive lens movement during the anterior capsulotomy should alert the surgeon to this problem.

Aged↗
PubMed1987

Glaucoma filtering surgery with 5-fluorouracil.

A life-table analysis of surgical outcomes was performed on the first eye of 155 patients who were enrolled in a pilot study of glaucoma filtering surgery with postoperative subconjunctival 5-fluorouracil (5-FU) injections. The success rates at 1-, 2-, and 3-year intervals were 68, 63, and 63%, respectively, for 88 patients with non-neovascular glaucoma in aphakia; 82, 75, and 75% for 39 patients with non-neovascular glaucoma after unsuccessful filtering surgery; and 68% at each yearly interval for 28 patients with neovascular glaucoma. Complications which resulted from filtering surgery and the 5-FU injections included corneal epithelial defects (55.5%), conjunctival wound leaks (36.8%), suprachoroidal hemorrhage (5.8%), rhegmatogenous retinal detachment (2.6%), endophthalmitis and phthisis (1.9% each), and corneal scarring, late bleb leak, malignant glaucoma, and traction retinal detachment (1.3% each). A Cox Model regression analysis failed to demonstrate a correlation between surgical success and age, race, type of filtering procedure, or total dose of 5-FU received. Postoperative subconjunctival 5-FU may increase the operative success rate for selected patients with a high risk for failure after glaucoma filtering surgery.

Actuarial Analysis↗
PubMed1987

Mutagenic potential of a 193-nm excimer laser on fibroblasts in tissue culture.

In response to concerns regarding possible DNA damage by far ultraviolet radiation during excimer laser corneal surgery, the mutagenic potential of an argon fluoride excimer laser (193 nm) on BALB/3T3 mouse fibroblasts grown in tissue culture was investigated. The cumulative incidence of anaplastic transformation after subablative radiant exposures from 3.5 mJ/cm2/pulse to 13.4 mJ/cm2/pulse was 3.6% of all cell cultures. The incidence of anaplastic transformation in nonirradiated controls was 4.2%. Transformation after exposure to x-ray radiation (60.9 rad) was 98.8%. The difference between the incidence of transformation of nonirradiated controls or excimer-treated cultures compared with x-ray radiation-treated cells was significant P less than 0.0001 (chi square test). In this standard cell line, 193-nm laser energy does not appear to have substantial mutagenic potential.

Anaplasia↗
PubMed1987

The effect of beta irradiation on monkey Tenon's capsule fibroblasts in tissue culture.

Fibroblast proliferation with subsequent bleb scarring is a major cause of filtering surgery failure. To investigate possible antiproliferative effects of beta radiation, owl monkey Tenon's capsule fibroblasts in tissue culture were irradiated to doses of 30, 100, 300, 1,000, and 3,000 rads with a linear accelerator and to doses of 95,285, and 950 rads with a Strontium-90 applicator. The irradiated cell proliferation expressed as the percentage of the non-irradiated control growth on the third and seventh days, respectively, after beta irradiation was: 97% and 96% after 30 rads; 72% and 90% after 100 rads; 48% and 44% after 300 rads; 39% and 14% after 1,000 rads; and 39% and 14% after 3,000 rads. Similar effects on cell proliferation were observed with the Strontium-90 applicator. The inhibitory effect of beta irradiation on fibroblast proliferation in tissue culture suggests that beta irradiation after filtering surgery may reduce postoperative bleb scarring.

Animals↗
PubMed1987

Trifluorothymidine and 5-fluorouracil: antiproliferative activity in tissue culture.

The antiproliferative activity of trifluorothymidine (F3TDR) and 5-fluorouracil (5-FU), two cell-cycle-phase-specific antimetabolites, was compared in a tissue culture model of human scleral fibroblasts and rabbit corneal epithelial cells. The mean concentrations required to inhibit human scleral fibroblast proliferation to 50% of the control rate (ID50) after 5 days of exposure were 8.50 micrograms/mL for F3TDR and 0.43 microgram/mL for 5-FU. The corresponding ID50 levels for rabbit corneal epithelial cells were 0.24 microgram/mL and 0.42 microgram/mL. The ID50 of F3TDR was significantly higher than that of 5-FU in human scleral fibroblasts (p less than 0.001) but not in rabbit corneal epithelial cells. F3TDR appears to have no clinical advantage over 5-FU in minimizing corneal epithelial toxicity when given to prevent fibroblast proliferation after glaucoma filtering surgery.

Animals↗
PubMed1987

An intraoperative intraocular pressure monitor.

An autoclavable instrument based on piezoelectric principles for intraoperative monitoring of the intraocular pressure is presented. Accurate and rapid recordings of intraocular pressure during various surgical techniques are discussed.

Humans↗
PubMed1987

Subconjunctival 5-fluorouracil mechanisms of ocular penetration.

Aqueous, corneal, and tear film 14C 5-fluorouracil (5-FU) levels were measured in rabbit eyes to better understand the mechanisms of intraocular penetration after subconjunctival injection. Significantly higher aqueous and tear 5-FU levels were achieved one hour after administration when the subconjunctival injection was given transconjunctivally rather than percutaneously through the upper lid [aqueous = 65.7 +/- 9.1 micrograms/ml vs 21.3 +/- 5.1 micrograms/ml (mean +/- SE; p = 0.02, 2-tailed t-test); and tears = 5408.8 +/- 357.3 micrograms/ml vs 228.0 +/- 46.4 micrograms/ml (mean +/- SE; p = 0.004, 2-tailed t-test)]. The aqueous 5-FU levels four hours after transconjunctival injection were significantly greater in anesthetized rabbits without blink reflexes than in those with intact reflexes [32.0 +/- 3.2 micrograms/ml vs 13.4 +/- 0.5 micrograms/ml (mean +/- SE; p = 0.026, 2-tailed t-test)]. The corneal 5-FU levels four hours after transconjunctival injection were greatest nearest the injection site. Direct corneal penetration appears to account for the majority of the aqueous 5-FU concentration after subconjunctival injection; however, there may also be diffusion through the limbus.

Animals↗
PubMed1986

Preliminary report on corneal incisions created by a hydrogen fluoride laser.

We created corneal incisions in eye bank eyes with a pulsed hydrogen fluoride infrared laser. This laser was selected because its emission spectrum (2.7 to 3.0 micron) closely corresponds to the absorption peak of water in the infrared region. Short pulses (200 nsec) of hydrogen fluoride laser light focused with a cylindrical lens resulting in radiant exposures of 1.3 J/cm2 at the corneal surface created linear cuts in the cornea with minimal thermal damage adjacent to the incision, suggesting that the pulsed hydrogen fluoride laser may be useful for corneal surgery.

Cornea↗