John V. Thomas

Argon Laser Trabeculoplasty in the Presurgical Glaucoma Patient

The trabecular meshwork in 334 eyes of 260 patients with medically uncontrolled primary and secondary open-angle glaucoma was treated with the argon laser. The average intraocular pressure reduction obtained was 7.1 mm Hg. Tonographic data showed significant increase in the facility of outflow. Glaucoma surgical intervention was avoided in 87.5% of phakic eyes and in 62.1% of aphakic eyes. Laser trabeculoplasty was found to be effective in primary open-angle glaucoma, pseudoexfoliation glaucoma, pigmentary glaucoma, angle recession glaucoma, glaucoma secondary to uveitis, and in eyes with failed glaucoma surgical procedures. The length of follow-up in this series ranged from one week to 21 months, with an average of five months. The major complication noted was a rise in intraocular pressure following treatment. In one eye, a small central island of vision was lost due to this intraocular pressure elevation. Treating one-half of the angle in each of two treatment sessions separated by a few weeks reduces the degree of this pressure elevation. The glaucoma status of 3% eyes was made worse after treatment with trabeculoplasty.

Extracapsular Cataract Extraction and Posterior Chamber Intraocular Lens Implantation in Glaucomatous Eyes

Two hundred ninety-six eyes of 250 patients undergoing extracapsular cataract extraction (ECCE) with or without the implantation of a posterior chamber intraocular lens (PC-IOL) were studied. Pre-existing glaucoma of varying severity was present in 139 eyes and no known ocular pathology other than cataract in 157 eyes. During the first eight weeks following surgery, intraocular pressure elevations greater than or equal to 15 mmHg above baseline were seen in 23% of glaucomatous eyes controlled before surgery with glaucoma medications, in 39% of glaucomatous eyes controlled before surgery with argon laser trabeculoplasty, and in only 3% of nonglaucomatous eyes. The implantation of a PC-IOL did not influence the incidence of postoperative intraocular pressure (IOP) elevations. Among glaucomatous eyes with severe preoperative visual field loss (split fixation or central island less than or equal to 10 degrees), 9.7% had worsening of visual field after surgery. Open angle glaucoma of unclear etiology developed in 1.4% of normal eyes following uncomplicated ECCE with PC-IOL implantation. Surgical techniques the authors have found useful in glaucomatous eyes undergoing ECCE with PC-IOL implantation are discussed.

Optic Disc Cupping in Arteritic Anterior Ischemic Optic Neuropathy Resembles Glaucomatous Cupping

Five cases of anterior ischemic optic neuropathy secondary to biopsy-proven giant cell arteritis are presented. In each case, cupping of the optic disc, which closely resembled glaucomatous cupping, was observed in the affected eye. The presence of glaucoma was ruled out on the basis of normal intraocular pressures and normal tonographic measurements of facility of outflow. These cases indicate that arteritic ischemic optic neuropathy can result in optic disc cupping, which closely resembles glaucomatous cupping. The similarities in the appearance of cupping of these discs with that seen in eyes with glaucoma suggest that the pathogenesis of cupping in glaucoma and in arteritic ischemic optic neuropathy may share some common mechanisms.

Effect of Pilocarpine in Treatment of Intraocular Pressure Elevation Following Neodymium:YAG Laser Posterior Capsulotomy

A prospective study was conducted in 30 eyes of 30 patients to determine if pilocarpine would prevent increased intraocular pressure following Q-switched neodymium (Nd):YAG laser posterior capsulotomy. Fifteen eyes were given pilocarpine 4%, immediately following laser therapy and every hour until bedtime. Fifteen eyes served as untreated controls. Our results show that without prophylactic therapy, 10 of 15 eyes (67%) had a post-laser intraocular pressure (IOP) elevation of greater than 10 mmHg, while only one of 15 (6.6%) of the pilocarpine-treated eyes had a rise of that magnitude. The facility of outflow was reduced by 42% in the untreated eyes in contrast to an increase of 3% in those eyes treated with pilocarpine. Thus, pilocarpine 4% is effective in reducing the incidence and magnitude of elevated IOP following Nd:YAG posterior capsulotomy.

Pupillary and iridovitreal block in pseudophakic eyes.

Twenty-six cases of pupillary and iridovitreal block in pseudophakic eyes are reported. Although ten patients presented with acute angle closure glaucoma, the majority were asymptomatic and had normal intraocular pressures. While cure was finally achieved in all cases, recurrence of block occurred in six eyes as late as two months after initial successful treatment. A variety of therapeutic modalities including argon laser iridectomy, argon laser gonioplasty (iridoplasty), surgical iridectomy, surgical vitrectomy, Q-switched Nd:YAG laser iridectomy and Nd:YAG laser photodisruption of the anterior vitreous face were needed. Despite successful relief of pupillary and iridovitreal block in these eyes with no evidence of glaucoma prior to cataract and lens implant surgery, four eyes developed eight or more clock hours of peripheral anterior synechiae, and nine eyes continue to require chronic medical therapy for glaucoma.

Laser Trabeculoplasty Re-Treatment

Because of inadequate control of intraocular pressure, 26 eyes of 24 patients with primary and secondary open-angle glaucoma who had previously undergone argon laser trabeculoplasty were re-treated. Re-treatment was successful in ten eyes (38%); their average decrease in intraocular pressure was 10.2 mm Hg. After laser re-treatment, three eyes (12%) had marked increases in intraocular pressure, ranging from 10 to 37 mm Hg above baseline, necessitating urgent surgical intervention.

Shock-wave Effect on Anterior Segment Structures Following Experimental Neodymium:YAG Laser Iridectomy

The short-pulse laser may prove superior to the argon laser in producing noninvasive iridectomies. Little is known of the effects of the laser shock-wave on anterior segment structures adjacent to the iris. To investigate this question, iridectomies were produced in two owl monkeys using a neodymium (Nd):YAG laser and tissues were evaluated by light microscopy and scanning and transmission electron microscopy. For purposes of comparison, one eye received an iridectomy produced by an argon laser. Results indicate that while clean iris colobomas can be produced with a well-focused Nd:YAG laser, its shock-wave affects tissues in both the trabecular meshwork and corneal endothelium if the iridectomy is located within 0.8 mm of the limbus. No damage to the trabecular meshwork or corneal endothelium was evident after the argon laser iridectomy.

Effect of cataract surgery on intraocular pressure reduction obtained with laser trabeculoplasty

Thirty-nine eyes of 34 patients with open-angle glaucoma who had been treated successfully with argon laser trabeculoplasty underwent either extracapsular cataract extraction with posterior chamber intraocular lens implantation or intracapsular cataract extraction without lens implantation. Cataract surgery did not have a significant effect on the magnitude of intraocular pressure reduction obtained with laser trabeculoplasty. This study supports the view that eyes with coexisting cataract and glaucoma may benefit from laser trabeculoplasty before cataract surgery.

Acute Glaucoma Following Nd:YAG Laser Membranotomy

A 65-year-old aphake with a functioning filtration bleb underwent neodymium:YAG laser membranotomy. Shortly thereafter, he acutely developed pain, nausea, and visual blur with an intraocular pressure of 42 mm Hg. The mechanism of the acute glaucoma is believed to be occlusion of the fistula by herniated vitreous.

Relationship of Patient Age and Tolerance to Carbonic Anhydrase Inhibitors

A retrospective review of the records of 222 patients indicated a significantly higher incidence of long-term tolerance to carbonic anhydrase inhibitors among patients 40 years of age or less than in older patients. This finding indicated that since argon laser trabeculoplasty and conventional glaucoma surgery have low rates of success in young individuals, it seems prudent to consider carbonic anhydrase inhibitors as part of long-term maximum medical therapy particularly in younger individuals unless specific contraindications exist.