|Year : 1983 | Volume
| Issue : 6 | Page : 755-758
Argon laser therapy in open angle glaucoma
B Sridhar Rao
Sankara Nethralaya, Medical Research Foundation 18, College Road, Madras, India
B Sridhar Rao
Sankara Nethralaya, Medical Research Foundation 18. College Road, Madras
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Rao B S. Argon laser therapy in open angle glaucoma. Indian J Ophthalmol 1983;31:755-8
Laser treatment of the trabecular meshwork inan attempt to improve the aqueous outflow was first reported by Krasnov in 1973. Using high power and short bursts of ruby laser energy he was able to make punctures in the trabecular meshwork and reach schelemm's canal in selected parts of the angle. However, the effect did not last for more than few months and repetition of the procedure was necessary. Wise and Witter conceived a totally new concept of applying small non-penetrating laser burns to the trabecular meshwork. This is based on the theory that collapse of the trabecular meshwork might be, the major factor in the mechanism of production of open angle glaucoma. Application of nonpenetrating burns reverses this collapse thereby produces a fall in intraocular pressure. The present study reports a series of cases of uncontrolled upon angle glaucoma treated with argon laser at Sankara Nethralaya.
| Material and methods|| |
The present study is a report of the first seven cases of open angle glaucoma treated between February 1982 to May 1982. All the cases were considered presurgical as they were uncontrolled i.e. progressive field loss and disc changes with maximal tolerated medical therapy. This included miotics, epinephrine and carbonic anhydrase inhibitors in tolerated doses. Timolol maleate 0.5% was used in addition to the above drugs in two cases. This group included one patient intolerant to miotics and three to carbonic anhydrase inhibitors.
Following baseline evaluations were performed in all the cases.
1. Complete ophthalmic evaluation including history, refraction and Gonioscopy with careful documentation of angle structures, pigment and iris contour.
2. Visual field examination with a calibrated Goldmann perimeter.
3. Goldmann applanation tonometry.
4. Dilated fundus examination.
The patients medication schedules were stabilized and when clinically feasible were unchanged during the follow-up period. This was done to assess the effect of the laser treatment alone on intraocular poressure without introducing the variable of medication and modification. All the patients were informed about the nature of treatment, and the need for subsequent filtration surgery should laser therapy fail to control the glaucoma.
All the patients were treated as out-patients with topical anaesthesia using 4%, Xylocaine. Continuous wave argon laser Coherent Radiation model 900(R was used. A three-mirror gonioscopic contact lens was used. In all patients the gonioscopic mirror gave the best visualization of the a,igle. Approxiniatelv11)1) burns were applied to the pigmented travecular meshwork band above the scleral spur. The burns were evently spaced over the 300 degrees of the angle [Figure - 1]. In all cases, a 50 micron spot size 0.1 second exposure time and a power setrting of 800 to 1100 milli watts were used. The power level chosen was adequate to produce depigmented spot at the point of impact with occasional bubble or scattering of pigment. Eyes with minimal pigmentation received more power than eyes with dense pigmentation. Following treatment the patients were asked to continue their regular glaucoma medication; a topical steroid drop three times a day for 3 days was added to the above treatment schedule. The patients were seen postoperatively on the 3rd day and later at 2 weeks -and 2 months intervals. Visual acuity, applanation tonometry and gonioscopy were performed in the follow-up period.
| Observations|| |
The age group of the cases treated varied from 11 years to 75 years. There were 4 cases of primary open angle glaucoma. Out of these 2 cases were juvenile in onset [Table - 1]. 3 were cases of open angle glaucoma in aphakia. All cases had advanced glaucomatous cupping with visual field loss. 4 cases had already lost the fellow eye due to glaucoma. In 2 cases. glaucoma was controlled with medical therapy and one case had undergone successful filtration surgery in the fellow eye [Table - 2].
There was a significant fall in the intraocular pressure of 6mm of Hg or more in4 cases. Out of these 2 cases primary open glaucoma, one was a case of juvenile open angle glaucoma and was a case of open angle glaucoma in aphakia. All these four patients had fairlydense pigmentation in the travecular meshwork.
Out of the three cases which did not show a significant drop in intraocular pressure. Two were cases of open angle glaucoma in aphakia and one was a case of juvenile type of open angle glaucoma. Out of these three cases with poor response to laser therapy one was subjected to successful trabeculectomy, one refused surgery and in the third case of open angle glaucoma, the drop in pressure was considered sufficient, to avoid a filtration surgery.
Accidental coagulation of the iris base occurred in 4 cases, which did not appear to affect the final results, Haemorrhage was not noted during the treatment in any of the cases. Post treatment complications were very minimal. Only one case had transient iritis which responded to topical steriods. Scatterred svnechiae were observed in 2 cases [Table - 3], they were small, extended upto the trabecular meshwork at the level of the burn and were localized in extent.
Out of 4 cases of open angle glaucoma, who had a good response to laser therapy, two were cases of primary open angle glaucoma, one juvenile type of open angle glaucoma, and one had open angle glaucoma in aphakia. Even though the number of patients in this study is very small, certain trends are obvious. In the phakic group, primary open angle glaucoma had a fairly good response, juvenile type of glaucoma had moderate response and aphakic group poor response to laser therapy [Table - 4]. Wise and Witter' in their study found that aphakic eyes showed less response compared to the phakic eyes. All the four cases with significant fall in intraocular pressure had a fairly dense pigment in the trabecular meshwork. Out of 3 cases with poor laser response 2 had minimal pigment in the trabecular meshwork. The effect of laser appears to be related to the amount of pigment in the trabecular meshwork. Patients with pseudoexfoliation and glaucoma who have dense pigment in trabecular meshwork require to be compared with patients with minimal pigment to confirm this relationship.
The mechanism of effect of laser therapy appears to be an increase in the trabecular out flow.,
Small scattered synechiae were observed in two cases in this study. Schwarts et a1  had an incidence of 29% in their series. These synechiae are related to the end point of coagulation and are common with heavier burns. These did non affect the final outcome.
| Summary and conclusion|| |
Argon laser therapy in 7 cases of open angle glaucoma uncontrolled with maximal tolerated medical therapy discussed in detail. In 4 cases the intraocular pressure could be brought down to a level which was considered safe and a filtration surgery could be avoided. In no case was the glaucoma wersened by laser therapy. However, longer follow-up with larger no cases will help us define the place of argon laser therapy in open angle glaucoma in the proper perspective. Laser trabeculoplasty is a resonably effective moderately safe form of therapy in patients with open angle glaucoma.
| References|| |
Krasnov, M.M. 1973, Amer J. Ophthalmol, 75:674-678.
Wise, J.B., Witter, S.L. 1979, Arch. Ophthalmol, 97: AR RAO 319-322.
Schwartz„A.L., Whitten, M.E., Bleiman, B. Martin D., 1981, Ophthalmolgy 88:203-212.
Wilensky, J.T., Jampol, L.M. 1981, Ophthalmol 88:213-217.
[Figure - 1]
[Table - 1], [Table - 2], [Table - 3], [Table - 4]