Breakdown and reestablishment of blood-aqueous barrier with laser trabeculoplasty

Effect of Laser Trabeculoplasty on Nocturnal Intraocular Pressure in Medically Treated Glaucoma Patients

PURPOSE

To evaluate the effects of laser trabeculoplasty on 24-hour intraocular pressure (IOP) in a group of medically treated open-angle glaucoma patients.

DESIGN

Prospective experimental study.

PARTICIPANTS

Eighteen open-angle glaucoma patients.

METHODS

Laser trabeculoplasty (180 degrees ) was performed on 28 eyes of 18 glaucoma patients. Twenty-four-hour IOP data were collected in a sleep laboratory before and 45 to 80 days after the procedure. Measurements of sitting and supine IOP were taken during the 16-hour diurnal/wake period, and measurements of supine IOP were taken during the 8-hour nocturnal/sleep period in 2-hour intervals.

MAIN OUTCOME MEASURES

Changes in the mean, peak, and range of IOP during the office-hour, diurnal, nocturnal, and 24-hour periods.

RESULTS

Compared with the baselines, changes in the mean, peak, and range of IOP were not significant during the office-hour period and during the diurnal period in either the sitting or the supine position. The mean, peak, and range of IOP were reduced significantly during the nocturnal period in the supine position. Mean and peak 24-hour IOP were reduced significantly in the habitual body positions (sitting during the diurnal period and supine during the nocturnal period). The reduction of mean 24-hour IOP in the supine position also was significant.

CONCLUSIONS

In this group of medically treated open-angle glaucoma patients, laser trabeculoplasty reduced IOP more consistently during the nocturnal period than during the diurnal period.

Influence of argon laser trabeculoplasty on transforming growth factor-beta 2 concentration and bleb scarring following trabeculectomy

BACKGROUND

The purpose of this study was to evaluate the influence of previous argon laser trabeculoplasty (ALT) on transforming growth factor-beta 2 (TGF-beta 2) concentration of the aqueous humor and its influence on bleb scarring after trabeculectomy.

METHODS

Fifty-one patients with primary open-angle glaucoma (POAG) and 29 patients with exfoliation (XFS) glaucoma were recruited for this prospective study before undergoing trabeculectomy. Sixty to 200 micro l of aqueous humor were analyzed for total and biologically active TGF-beta 2 concentrations (R and D Systems). TGF-beta 2 levels and a standardized bleb assessment were compared between the ALT- and non-ALT-treated groups.

RESULTS

POAG eyes without ALT showed significantly higher total TGF-beta 2 levels (2,317.7+/-1,041.1 pg/ml) than eyes with previous ALT (1,621.6+/-899.6 pg/ml; P=0.026). No significant difference was found for active TGF-beta 2 levels (ALT: 238.1+/-119.0 pg/ml; no ALT: 220.1+/-96.9 pg/ml; P=0.585). In XFS patients ALT did not alter total TGF-beta 2 levels (ALT: 1,524.9+/-624.9 pg/ml, no ALT: 1,220+/-499.1 pg/ml; P=0.20), but active TGF-beta 2 was significantly higher in the ALT-treated (237.0+/-99.7 pg/ml) than in the non-ALT-treated (140.0+/-95.3 pg/ml, P=0.028) group. Bleb grading revealed no statistical difference between the ALT- and non-ALT-treated groups in POAG (P=0.545, Fisher's exact test), whereas XFS patients with ALT were at increased risk for scarring compared to non-ALT-treated patients (P=0.053).

CONCLUSIONS

ALT appears to increase the risk of scarring in XFS patients because of increased levels of activated TGF-beta 2.

Ocular hypotensive effect of pilocarpine before and after argon laser trabeculoplasty

PURPOSE

The purpose of this study was to compare the hypotensive response of human glaucomatous eyes to 1% pilocarpine solution before and after argon laser trabeculoplasty.

METHODS

We designed a prospective, 'repeated measures' study comparing the ocular hypotensive effect of acutely administered 1% pilocarpine solution in 30 medically uncontrolled glaucomatous eyes, before and after argon laser trabeculoplasty.

RESULTS

The pilocarpine-induced IOP decrease was 3.6 +/- 0.59 mmHg before argon laser trabeculoplasty, and 1.8 +/- 0.53 mmHg after laser therapy. In both instances, the pilocarpine hypotensive effect was significantly correlated with pretreatment IOP (p = 0.02, r = 0.41 before argon laser trabeculoplasty, and p = 0.003, r = 0.52 after argon laser trabeculoplasty). We built a 'repeated measurements ANCOVA' model, and found no statistically significant difference between the pilocarpine IOP lowering effect before and after argon laser trabeculoplasty (p = 0.4).

CONCLUSION

Argon laser trabeculoplasty does not modify the IOP lowering effect of 1% pilocarpine solution.

Glaucoma associated with uveitis

Raised intraocular pressure is a common and frequently serious complication of anterior uveitis. The milieu of inflammatory cells, the mediators they release, and the corticosteroid therapy used to treat the uveitis can participate in the pathogenesis of uveitic glaucoma. These factors alter the normal anatomic structure of the anterior chamber and angle, influencing aqueous production and outflow. These changes act to disrupt the homeostatic mechanisms of intraocular pressure control. Structural changes in the angle can be acute, such as in secondary angle closure with pupillary block glaucoma, or chronic, such as combined steroid-induced and secondary open angle glaucoma. Management of uveitic glaucoma may be difficult because of the numerous mechanisms involved in its pathogenesis. Diagnostic and therapeutic decisions are guided by careful delineation of the pathophysiology of each individual case. The goal of treatment is to minimize permanent structural alteration of aqueous outflow and to prevent damage to the optic nerve head. This article reviews the pathogenesis of uveitic glaucoma, with specific attention to etiology. Medical and surgical therapies are also discussed, with emphasis on the more recent developments in each category.

Laser trabeculoplasty

Over a decade, laser trabeculoplasty has evolved from being a novel new treatment to one that is a commonly accepted intervention in the management of open-angle glaucoma. Despite its widespread use, however, there are still many unanswered questions about laser trabeculoplasty, including its mechanism of action and the ideal treatment parameters. In this review, we will discuss the history of the technique, the clinical experience, and some of the experimental studies that have been conducted to answer the questions regarding its mechanism of action.

Risk factors for the development of Tenon's capsule cysts after trabeculectomy

Tenon's capsule cysts (TCCs) are a complication of glaucoma filtering surgery. They are frequently associated with substantial elevations in intraocular pressure (IOP) beginning 2 to 8 weeks postoperatively. To determine the incidence and possible risk factors for the development of TCCs, case records of all patients who received trabeculectomy over a 4-year period at the Wills Eye Hospital were reviewed. The incidence of TCCs was 28% in those who underwent trabeculectomy. Characteristics of patients after trabeculectomy in whom TCCs developed were compared with patients after trabeculectomy in whom TCCs did not develop. Both univariate and multivariate techniques were used to assess the association of characteristics associated with the development of TCCs. Factors associated with increased risk (P less than 0.05) were: history of prior TCCs, argon laser trabeculoplasty, male gender, and the use of preoperative sympathomimetics. The use of a compression shell was associated with decreased risk (P less than 0.05).

The development of encapsulated filtering blebs

The development of an encapsulated filtering bleb (Tenon's cyst) complicated 56 of 409 consecutive filtering operations (13.7%) performed during a 40-month period after January 1983. Fifteen eyes (27.8% of encapsulated blebs) required surgical revision. The recognition of bleb encapsulation occurred 20.4 +/- 12.7 days (mean +/- standard deviation) postoperatively. Prolonged duration of beta-adrenergic antagonist therapy was associated with an increased frequency of bleb encapsulation (180.6 +/- 128.5 weeks without encapsulation, 229.0 +/- 129.3 weeks with encapsulation, P less than 0.009). Bleb encapsulation occurred in 42 of 272 eyes with previous argon laser trabeculoplasty, but in only 4 of 85 eyes without any previous anterior segment laser (P less than 0.01). Encapsulated filtering blebs developed in 4 of 12 (33.3%) eyes with congenital glaucoma and 4 of 9 (44.4%) eyes with juvenile glaucoma (P less than 0.0002). The intraocular pressures (IOPs) in the eyes with encapsulated filtering blebs were significantly elevated at 1, 2, and 3 postoperative weeks, and at final follow-up compared with eyes without bleb encapsulation.

The laser power needed for optimum results in argon laser trabeculoplasty

Ninety-five successive argon laser trabeculoplasties to as many patients were followed 6 to 18 (mean 8) months. Forty-eight eyes had capsular glaucoma and 35 simple glaucoma. The power used ranged from 100 mW to 1000 mW and the total energy from 1.0 J to 5.0 J. The success rates between groups were tested with a chi 2-test. With laser power of more than 500 mW and energy level more than 3.0 J, the success rates were maximal (77% and 75%).

The effect of ultraviolet, visible and infrared radiation on the rabbit blood-aqueous barrier

We studied the effects of visible (400-750 nm), infrared (750-1100 nm), and ultraviolet (300-400 nm) radiation on the breakdown of the blood-aqueous barrier (BAB) in albino rabbit eyes using fluorophotometry and fluorescein-bound albumin. There was no evidence of BAB breakdown following exposure to visible (158 J cm-2) or infrared (106 J cm-2) radiation. Fluorescence was detected in the anterior chamber 15 min following ultraviolet (UV) (300-400 nm; 37 J cm-2 and 73 J cm-2) and ultraviolet-A (UV-A) (320-400 nm; 45 J cm-2 and 90 J cm-2) irradiation. This fluorescence peaked at 2 hr after irradiation. Reestablishment of the BAB, indicated by no detectable fluorescence, occurred in all animals after 24 hr. There was a significant increase in fluorescence with increasing UV-irradiation dosage in all groups (P less than 0.05). Comparison of BAB breakdown following exposure to ultraviolet 320-400 nm and 300-400 nm in the same dosage (45 J cm-2) indicated that the inclusion of shorter wavelength UV exposure produced a significantly higher degree of BAB breakdown (P less than 0.001).

Topical indomethacin therapy before argon laser trabeculoplasty

Fifty treatment sessions for 43 eyes (35 patients) receiving argon laser trabeculoplasty to one-half the angle were randomly assigned in a double-masked fashion to pretreatment with either topical indomethacin 1% or placebo. In 25 treatments intraocular pressure increased 3 mm Hg or more within four hours. Topical indomethacin pretreatment had no effect on the incidence, magnitude, or time course of this acute increase. It also did not alter the long-term effectiveness of the laser treatment (-3.8 mm Hg in the indomethacin-treated group vs -4.3 mm Hg in the placebo-treated group). The overall incidence of new peripheral anterior synechiae found on gonioscopy at one month was 32% (16 of 50 treatments). Synechiae formation was much higher in blacks (ten of 11 eyes or 91%) than in whites (five of 38 eyes or 13%). Although there was an association between acute anterior chamber inflammation after laser treatment and ultimate synechia formation (P less than .05), indomethacin pretreatment did not alter its occurrence.

The effect of topical indomethacin on acute pressure elevation of laser trabeculoplasty in capsular glaucoma

In this controlled study 24 phakic patients with capsular glaucoma received a 5-drop loading dose of topical 1.0% indomethacin on the eye to be treated and the fellow eye prior to argon laser trabeculoplasty and post-operatively every 3 h to the end of the day. A control group consisted of 25 phakic eyes with capsular glaucoma which were lasered without indomethacin drops. There were no statistically significant differences between the groups in the post-operative mean intraocular pressures (IOP) and mean corrected changes in IOP immediately and one month after laser treatment. However, no eyes in the indomethacin treated group showed a true pressure rise greater than or equal to 10 mmHg whereas 4 eyes in the control group did (P = 0.1).