|Year : 1983 | Volume
| Issue : 6 | Page : 751-753
Argon laser trabeculoplsty in the treatment of glaucoma
Verinder S Nirankari, James Karesh, Richard D Richards
Department of Ophthalmology, School of Medicine, University of Maryland Hospital, USA
Verinder S Nirankari
University of Maryland Hospital, 22 South Greene Street. Baltimore, Maryland-21201
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Nirankari VS, Karesh J, Richards RD. Argon laser trabeculoplsty in the treatment of glaucoma. Indian J Ophthalmol 1983;31:751-3
Treatment of open angle glaucoma by laser therapy of the trabecular meshwork has been the subject of great interest ever since the reports of Krasnov in 1973  and Worthen and Wickham in 1974 . Recently, studies by Wise , and others,, have rekindled interest in this procedure.
| Materials and methods|| |
Since May of 1981, a total of 130 eyes of 96 patients with primary and secondary open angle glaucoma were treated. This report is on the first 90 eyes of 64 patients who have had a minimum follow-up of six months. These are consecutive patients with none lost to followup. All the patients in this series had uncontrolled pilocarpine 4%, timolol. 0.5%, an epinephrine compound, and carbonic anhydrase inhibitors. All patients had progressive glaucomatous damage to their optic nerve, visual field loss, and were candidates for surgical intervention.
All the patients were treated as outpatients. The continous wave Coherent radiation model 900 argon laser was used. The eye to be treated was anesthetized with topical 0.5% proparacain hydrochloride and a coated 3 mm contact lens was used to treat the angle.
The laser was set with a spot size of 50 microns with the duration of exposure of 0.1 seconds. The light from the laser was mericulously focused on the porterior trabecular meshwork immediately anterior to the scleral spur. Enough power was delivered to create a tiny bubble in the trabecular meshwork if it was pigmented, and blanching if the trabecular meshwork was unpigmented. The power required to do this varied from patient to patient and even from quadrant to quadrant in the same eye. The power used was from 0.7 milliwatts to 1. 1 watts with a majority of eyes treated with power settings between 0.8 and 0.9 milliwatts. Between 80 to 100 evenly spaced burns were used through the entire 360° of the angle in one sitting. This procedure is similar to that described by Wise and Witter.,
Following treatment, patients were advised to continue all their antiglaucoma medications and fluorometholone 1% eye drops were used four times daily for one week. Patients were examined at one week, one, three and six months, and one year following treatment. An ocular examination including visual acuity, slit lamp biomicroscopy, Goldmann applanation tonometry, and fundoscopy was done each time. In addition, visual fields and tonography were done at three and six months following treatment.
| Observations|| |
There were 90 eyes of 64 patients. The age range was from 35 years to 82 years with a mean of 66 years. There were 66 eyes or 47 black patients and 24 eyes of 17 white patients. There were 39 eyes of 29 male and 57 eyes of 35 female patients. Follow-ups ranged from 6 months to 16 months with a mean of 10 months. Eleven eyes had undergone previous filtering procedures which were unsuccessful. Diagnosis in mot cases was primary open angle glaucoma. Other less frequent diagnoses were aphakic glaucoma, uveitis and glaucoma, pigmentary glaucoma, pseudoexfoliaion glaucoma, and etc. [Figure - 1].
The prelaser intraocular pressure ranged from 19 mm Hg to 45 mm HG with an average of 28.2 mm Hg. The postlaser intraocular pressure ranged from 12 mm Hg to 30 mm Hg with an average of 12.6 mm Hg. The mean pressure change was a decrease of 10.6 mm Hg. This is statistically significant (p .001) using a ' student's t-test. The decrease in the intraocular pressure persisted over a 16 month follow-up period as seen in [Figure - 2].
Tonography data was available in 29 eyes. The average facility of aqueous outflow (C) prior to treatment was 0.09. The average post treatment C value was 0.19. This is statistically significant (p .001) using a student's t-test.
The overall success rate, as measured by post-treatment IOP of equal to or less than 21 mm Hg was 85% (76 eyes). Partial success was achieved in five eyes with pressure reduced to between 22 and 24 mm Hg. No differences in the success rate were seen between blacks and whites or between males and females [Figure - 3].
All patients in this series developed a mild transient uveitis which cleared in all cases by one week. There were six eyes that developed transient elevations of intraocular pressure varying between 2 mm Hg and 9 mm Hg over the baseline. In all these cases, during the follow-up period, the elevation lasted a maximum of two weeks. All these eyes achieved satisfactory decline of IOP with a mean post-treatment IOP of 16.5 mm Hg (range of 13 mm Hg to 20 mm Hg).
Two eyes had small hemorrhages in the region of the Schlemm's canal during treatment. Both of these resolved with no sequelae. Samll scttered PAS were seen in 12 eyes following treatment. They were non-progressive and did not influence the success of the procedure.
There were nine eyes that were failures. Diagnoses in these eyes were primary open angle glaucoma (4), aphakic glaucoma (2), pseudoexfoliation glaucoma (2), and glaucoma-cyclitic crisis (1).
| Discussion|| |
Argon laser trabeculoplasty seems to be a highly successful procedure in the treatment of open angle glaucoma. Our experience is similar to that of previous investigators.,,,,, sub Using the technique, we were able to avoid surgery in 85% of our patients. Results indicate that the procedure appears to be as effective on black patients as on white patients. This is an important fact as the results of standard filtration procedures on the black population have been quite poor. Our results, like those in earlier studies, confirm that orgon laser trabeculoplasty more successfully controls glaucoma in phakic than in aphakic eyes. We agree with the findings of earlier studies that the pressure lowering effect of this procedure is long term ,, and, in out study, persisted over a 16 month follow-up period [Figure - 2].
Tonography data on 29 eyes showed an increased coefficient of outflow of +0.10 above the baseline. This was seen at 3 and 6 months following treatment. This increase in outflow is consistent with the theory of Wise , of trabecular tightening leading to improved aqueous outflow. Recent histopathologic evedence also tends to support this view.
The advantages of laser trabeculoplsty over filtering procedures are multiple. Laser trabeculoplasty is done on an outpatient basis using topical anesthesia, avoids the risks of intraocular surgery such as infection, cataractogenesis, etc., and is highly effective in black patients. It does not preclude or complicate filtration surgery should this surgery become necessary later on. Furthermore, cataract extraction in patients who have had successful laser trabeculoplasty has not worsened their glaucoma.
The only significant complication in our series was the transient elevation of intraocular pressure in six of our patients. This observation has been reported by others as well. This may be important in patients with higher baseline pressure, or in those who have very little visual field left. In such cases, treatment of 180° of the angle at one sitting with close monitoring of the intraocular pressure would be indicated.
Although argon laser trabeculoplsty does not replace conventional medical therapy, it seems to be an effective modality that is most useful in patients prior to consideration of filtration surgery. Further studies on its long term effectiveness and of the effect of retreatment will help to clarify the exact role of this procedure in the treatment of galucoma.
| References|| |
Krasnov, M.M.: 1973, Am J Ophthalmol 75:674-8.
Worthen DM, Wickham MG. 1974. Trans. Am. Acad. Ophthalmol & Otolaryngol 78: 371-3.
Wise, .JB, Witter SL. 1979 A pilot study. Arch Ophthalmol 97:319-22.
Wise. J.B 1981 Ophthalmol 88:197-202.
Schwartz, A.L., Whitten, M.E.. Bleiman. B, Martin. D., 1981, Ophthalmol 88:203-12.
Wilensky, J.T, Jampol. L.M: 1981, Ophthalmol. 88:213-17.
Thomal JV, Simmons RJ. Bcicher D 111:1982 Ophthalmol 89:187-97.
Schwartz, A.L, Anderson, D.R:1974 Arch. Ophthal mol. 92:134-8.
Rodrigues, M.M., Spaeth. G.L.. Donohoo, P: 1982, Ophthalmol. 89:198-210.
[Figure - 1], [Figure - 2], [Figure - 3]