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Biomedical subjects

W C Stewart

Publications and source records attributed to W C Stewart.

At least 91 records · Page 5Linked to original sources
PubMed1995

Anatomic features of the optic disc and risk of progression in ocular hypertension.

We evaluated characteristics of the optic disc in ocular hypertensive patients which might portend future glaucomatous damage. We included in this study 12 patients with an intraocular pressure > 21 mmHg who on follow-up showed signs of optic nerve head damage. Each of these patients were matched to an ocular hypertensive patient who remained stable for > 5 years. This study found that neither optic disc, neural rim or peripapillary halo areas, vein or artery diameter over non-atrophied or atrophied retinal areas, differed significantly between groups (p > 0.05, Wilcoxon signed rank test). However, peripapillary atrophy was greater in patients who showed signs of glaucomatous disc damage (1.757 +/- 0.36 mm2, p = 0.02, Wilcoxon signed rank test) compared to stable patients (1.064 +/- 0.79 mm2), although this finding was not significant after the Bonferroni correction. Patients with < 0.6 mm2 area of peripapillary atrophy (n = 6), however, did not suffer damage. This study suggests that a relationship between the extent of peripapillary atrophy and the chance of developing optic disc damage in patients with ocular hypertension deserves further study.

Atrophy↗
PubMed1995

Reproducibility of the Glaucoma-scope in cadaver eyes.

We evaluated the intra- and inter-observer variability of depth measurements of the optic disc in cadaver eyes using the Glaucoma-scope. Intra-observer variation of 10 separately captured images became significantly greater with increasing depth of the optic cup (p < 0.001). The standard deviation of depth measurements were 9.06 mu over the neural rim, 25.00 mu along the cup wall, and 40.94 mu at the bottom of the optic cup. However, intra-observer variation of a single captured image did not increase with greater optic cup depth. Intra-observer variation, but not inter-observer variation, generally was greater when measuring the superior than inferior optic disc (p < 0.05). This study suggests that when capturing separate optic disc images with the Glaucoma-scope, increased variation in depth measurements can be expected with greater optic cup depth and in the superior portion of the optic disc.

Cadaver↗
PubMed1994

Analysis of diode, argon, and Nd: YAG peripheral iridectomy in cadaver eyes.

We compared semiconductor diode, neodymium (Nd): YAG and argon laser iridectomies performed in 14 cadaver eyes using Miyake videographic, histologic and scanning electron analysis. We found that the diode laser created an iridectomy in < 10 applications in blue, hazel and brown irides using 1000-1200 mW over 0.5 seconds. In hazel and blue irides the argon laser created iridectomies at parameters similar to the diode, but required multiple low energy burns in brown irides. Scanning electron microscopy showed pigment epithelial loss with the diode and Nd:YAG laser, and heaped up epithelium at the iridectomy site with the argon laser. Nd:YAG laser had the greatest iridectomy size. This study suggests a possible clinical advantage of diode versus argon laser iridectomies in reduced applications in brown irides and in preventing postoperative pigment occlusion. However, diode laser demonstrated no definite advantage over Nd:YAG laser.

Cadaver↗
PubMed1994

Prognostic factors and postoperative course following single-plate Molteno implantation.

We evaluated potential preoperative and early postoperative prognostic indicators for chronic intraocular pressure control in 38 consecutive glaucoma patients undergoing single-plate Molteno implantation. Six months following surgery 22 patients had an intraocular pressure < or = 18 mm Hg and were considered successes. Twelve patients had an intraocular pressure > 18 mm Hg and were considered failures. Factors such as age, race, sex, type of glaucoma, phakic status, eye treated, intraocular pressure, bleb elevation, or number of glaucoma medicines were not significantly related to postoperative intraocular pressure control (p > 0.05). Postoperatively a significant difference in intraocular pressure was not observed between success and failure groups until three (13.8 +/- 5.4 versus 20.8 +/- 6.4 mm Hg, p = 0.010) and six (11.2 +/- 3.3 mm Hg versus 21.2 +/- 1.2 mm Hg, p < 0.001) months. Approximately 50% of patients who had an intraocular pressure > 20 mm Hg and 75% of those who measured < 20 mm Hg at any given examination in the early postoperative period were controlled six months postoperatively. Patients controlled at six months maintained control for as long as 43 months postoperatively. This study indicates that in the early postoperative period after a single-plate Molteno implant some patients have an ocular hypertensive phase but may ultimately be controlled, whereas most patients with an intraocular pressure within the normal range maintain control long-term.

Aged↗
PubMed1994

Fornix- vs. limbus-based flaps in combined phacoemulsification and trabeculectomy.

We studied prospectively the results of limbus-versus fornix-based flaps in patients undergoing combined trabeculectomy and phacoemulsification. We found no significant difference at six months postoperatively in the level of intraocular pressure between the limbus-(16.1 +/- 4.1 mm Hg) and fornix- (14.0 +/- 3.4 mm Hg, p = 0.161) based groups, or in the number of glaucoma medications (p = 0.0750). The highest intraocular pressure recorded within the first postoperative month was similar between groups (18.4 +/- 6.9 mm Hg for limbus and 18.5 +/- 5.5 mm Hg for fornix, p > 0.900). Postoperative bleb height, extent, and vascularity, as well as chamber depth were statistically similar between groups (p > 0.05). Postoperative complications were similar between groups. This study indicates that both fornix- and limbus-based flaps may be used safely and effectively when performing a trabeculectomy combined with phacoemulsification.

Aged↗
PubMed1994

Influence of serous suprachoroidal detachments on the results of trabeculectomy surgery.

We evaluated the influence of early serous choroidal detachments upon the results of trabeculotomy surgery. In 18 consecutive patients with serous choroidal detachments we found no significant difference in the intraocular pressure or number of glaucoma medicines from individually matched controls one year postoperatively. Final intraocular pressure was not correlated to the duration (p = 0.427), time of onset following surgery (p = 0.669), or size (p = 0.149) of the serous choroidal detachment. Prior to onset of the serous choroidal detachment the anterior chamber depth, bleb height, number of glaucoma medications, and intraocular pressure were statistically similar to the control group (p > 0.05). Following detachment, anterior chamber depth, and bleb height remained similar, but intraocular pressure fell from 9.4 +/- 6.5 to 4.6 +/- 4.1 mmHg (p = 0.025). Postoperative complications were similar between groups. This study indicates that serous choroidal detachments following trabeculectomy which are limited in size or duration are not associated with a worsening of long-term intraocular pressure control.

Aged↗
PubMed1994

Filtration surgery in rabbits treated with diclofenac or prednisolone acetate.

We performed filtration surgery in one eye of each of 28 rabbits. Either a nonsteroid (diclofenac) or a steroid (prednisolone acetate) was given as a postoperative antiinflammatory agent. On no examination day was there a significant difference in the intraocular pressure of the rabbits that had received diclofenac as contrasted with those that had received prednisolone acetate (P > .05, Student's t-test). Neither was there, based on log-rank life-table analysis, any significant difference between the two groups in terms of filtering bleb survival (P = .484). Finally, there were no significant differences on any examination day between the two groups in terms of bleb height or conjunctival injection (P > .05, Mann-Whitney U-test). We conclude that in this rabbit model for filtration surgery, the postoperative antiinflammatory effect of diclofenac was similar to that of prednisolone acetate. Because a nonsteroidal agent such as diclofenac that could provide an antiinflammatory effect sufficient to allow optimal bleb survival in humans, without the level of potential side effects of corticosteroids, might be clinically useful, further studies may be warranted.

Animals↗
PubMed1994

Comparison of diode and argon laser trabeculoplasty in cadaver eyes.

PURPOSE: To evaluate differences in the effects of diode and argon trabeculoplasty on cadaver eye trabecular meshwork. METHODS: The argon laser was used at a 50 mu spot size, 500 to 100 mW of power, and a 0.1 second time interval, and the diode laser was used at a 0.1 to 0.2 second time interval, 100 mu spot size, and 400 to 1200 mW of power. Analysis was performed using videography, microscopy, and scanning electron microscopy. RESULTS: This study found grossly that burns with the argon laser caused tissue blanching and pigment dispersion, whereas no reaction was observed with the diode laser. The diode laser made no observable histologic alterations, but the argon caused fragmentation and coagulation of trabecular beams. Scanning electron microscopy showed that the diode laser caused an area of trabecular beam coalescence measuring 50 to 100 mu in diameter with energies > or = 0.12 J. A surrounding zone of more superficial trabecular beam fragmentation measuring 200 to 400 mu in diameter also was observed. Similar energy levels from the argon laser caused hole formation 200 to 400 mu in diameter. Lower argon energy levels (0.05 J) caused inconsistent coalescence 50 to 100 mu in diameter similar to the diode laser. CONCLUSIONS: This study suggests that in the trabecular meshwork the diode laser causes a reaction at, but not at less than, energy levels shown previously to produce a clinical ocular hypotensive effect. Also, at similar energy per area, the tissue effects of the diode and argon laser are comparable.

Argon↗
PubMed1993

Conjunctival structure and cell counts and the results of filtering surgery.

We evaluated perioperative conjunctival biopsy specimens in 28 consecutive patients with primary open-angle glaucoma undergoing trabeculectomy who had not undergone previous intraocular surgery. We found six months postoperatively that the number of goblet cells was significantly greater (6.40 +/- 5.40 vs 1.68 +/- 1.60 per field of view; P = .004, Student's t-test) in patients with easier postoperative intraocular pressure control (intraocular pressure < or = 15 mm Hg with zero to two glaucoma medications) than in patients with more difficult intraocular pressure control (> 15 mm Hg with three or more glaucoma medications). No statistical differences between groups were observed in mast cells, neutrophils, eosinophils, macrophages, plasma cells, lymphocytes, or fibroblasts (P > .05). Also, no statistical difference between groups existed in conjunctival structure, including mucopolysaccharide and collagen composition, vascular density, or epithelial thickness (P > .05). This study suggests that the number of conjunctival goblet cells may be related to intraocular pressure control after trabeculectomy.

Adrenergic beta-Antagonists↗
PubMed1993

Factors associated with visual loss in patients with advanced glaucomatous changes in the optic nerve head.

We evaluated factors associated with decreased or stable visual function in 72 patients with primary open-angle glaucoma and complete cupping of the optic disk who were followed up five years or more. We found a significantly lower mean (15.4 +/- 2.7 mm Hg) and peak (24.5 +/- 6.9 mm Hg) intraocular pressure in those patients whose vision remained stable vs those whose vision decreased (21.3 +/- 3.2 and 39.2 +/- 11.0 mm Hg, respectively) (t-test, P < .001). Additionally, the variance of each patient's individual intraocular pressure readings measured during the follow-up period was lower in the group with stable vision (4.5 mm Hg) than in those in whom vision decreased (9.0 mm Hg) (F test, P < .001). Stepwise discriminant analysis disclosed that mean intraocular pressure, variance of an individual's intraocular pressure measurements over time, history of argon laser trabeculoplasty, and compliance with therapy discriminated 92.9% of patients (52 of 56) whose vision remained stable and 87.5% of patients (14 of 16) whose vision decreased. Reduction of intraocular pressure and compliance with therapy are important in patients with complete glaucomatous cupping of the optic disk.

Aged↗
PubMed1993

One-year results of semiconductor transscleral cyclophotocoagulation in patients with glaucoma.

We evaluated 30 consecutive patients with glaucoma treated with semi-conductor diode transscleral cyclophotocoagulation to determine the results and complications of this procedure. Twelve months after surgery the mean (+/- SD) preoperative intraocular pressure of 32.5 +/- 10.9 mm Hg (n = 30) had dropped to 20.8 +/- 15.6 mm Hg (n = 19) (P = .018, paired Student's t test), while the mean number of preoperative medications received decreased from 2.0 to 1.8 (P = .060, Wilcoxon's Signed Rank Test). One year after surgery three patients (10%) were unavailable for follow-up, eight (27%) had required other surgical procedures to control the intraocular pressure, 17 (56%) had controllable intraocular pressure of 21 mm Hg or below or received pain relief from the diode laser alone, and two (7%) patients with controlled intraocular pressure had suffered visual loss. Other complications included mild conjunctival hyperemia and uveitis in all patients and mild ocular pain in six patients. This study suggests the usefulness of diode transscleral cyclophotocoagulation in reducing the intraocular pressure for up to 1 year.

Adult↗
PubMed1993

Tight versus loose scleral flap closure in trabeculectomy surgery.

Thirty-two consecutive trabeculectomy patients were randomized to receive a tight scleral flap closure (15 eyes) with postoperative laser suture lysis, or a loose scleral flap closure (18 eyes) to determine differences in the surgical results. Three months postoperatively no statistical difference in intraocular pressure (loose closure 15.1 +/- 3.3 mm Hg, tight closure 15.0 +/- 3.6 mm Hg, p > 0.05) or number of glaucoma medicines (loose closure 1.6, tight closure 1.3, p > 0.05) existed between treatment groups. In the early postoperative period, no statistical difference between groups was observed in the anterior chamber depth, visual acuity or intraocular pressure (p > 0.05). Laser suture lysis was performed without complication in nine patients with a statistically significant reduction in intraocular pressure (p < 0.01). This study suggests, by the technique used, that no obvious benefit exists in using a tight versus a loose scleral flap closure when performing a trabeculectomy.

Aged↗
PubMed1993

The influence of age upon inflammatory cell counts and structure of conjunctiva in chronic open-angle glaucoma.

We evaluated the influence of age upon conjunctival structure and number of inflammatory cells by studying perioperative conjunctival biopsies from 54 consecutive primary open-angle glaucoma patients undergoing initial filtering surgery (trabeculectomy alone or combined cataract extraction and trabeculectomy). All patients had received chronic topical glaucoma therapy for > 1 year. We divided the patients into three age groups for analysis: 40-60 (n = 10), 61-74 (n = 28), and > 75 (n = 16) years. We found no statistical difference (p > 0.05, chi-square) in cell counts of neutrophils, eosinophils, mast cells, macrophages, fibroblasts, lymphocytes, plasma cells and goblet cells across the three age groups. In addition, no statistical differences were observed between age groups in vascular density, epithelial thickness as well as mucopolysaccharide and collagen composition (p > 0.05, chi square). This study suggests that conjunctival structure and inflammatory cell counts change little with advancing age in primary open-angle glaucoma patients.

Adult↗
PubMed1993

Postoperative prognostic indicators following trabeculectomy.

We evaluated prognostic indicators for long-term filtration from the ocular examination within the first three months following primary trabeculectomy without antimetabolite therapy. We found that in patients who were more easily controlled at one year postoperatively (intraocular pressure < or = 16 mmHg and using 0-2 medications), compared to those who were more difficult to control (> 16 mmHg or on three medications), the intraocular pressure became significantly different between groups at three months and the number of glaucoma medications at eight weeks postoperatively. More easily controlled patients had greater bleb elevation by one month and extent of bleb formation at two weeks postoperatively. The presence of microcysts, anterior chamber depth, and avascularity did not differ between the two groups. This study suggests that differences in the ocular examination exist within the first three months following trabeculectomy which reflect the postoperative intraocular pressure control at one year.

Aged↗
PubMed1993

Trabeculectomy with 5-fluorouracil vs single-plate Molteno implantation.

We compared the results achieved in 22 consecutive patients who underwent single-plate Molteno implantation, with those achieved in a matched group who had trabeculectomy with postoperative 5-fluorouracil. Six months following surgery, the average intraocular pressure (IOP) in the Molteno group was 15.4 +/- 8.0 mm Hg, and in the trabeculectomy group, 16.1 +/- 5.6 mm Hg (P = .920). A mean of 1.4 antiglaucoma medications were being used in each group (P = .776). Complications following Molteno implantation included six tube revisions and three flat anterior chambers; following trabeculectomy, eight serous choroidal detachments and nine positive Seidel tests. This study suggests that Molteno implantation and trabeculectomy with adjunctive 5-fluorouracil provide similar IOP control, but that the two procedures are associated with different types of complications.

Adult↗