Trabeculectomy: a re-evaluation after three years and a comparison with Scheie's procedure

Seventy-one patients with glaucoma needing surgical correction had either a peripheral iridectomy with a thermal sclerostomy or a trabeculectomy utilizing a modification of Watson's technique in which the scleral flap was closed tightly with sutures. Results of surgery were analyzed at intervals up to and including three years following the surgical procedure. The success of the operations was judged both in terms of the effect on intraocular pressure as well as on the visual ability of the eye. Since the surgeon's aim is to lower intraocular pressure to a particular level, not simply to an arbitrary level that facilitates statistical analysis, the control of the disease was graded in terms of how completely the operative procedure fulfilled the goal set by the surgeon at the time the decision to operate was made. While this method of grading success introduces a subjective element, a more valid assessment of the true value of the surgery may be obtained. The results suggest that the Scheie procedure lowers pressure to a lower level and for a longer duration than does the trabeculectomy (mean intraocular pressure three years postoperatively was 12.3 mm Hg in cases of primary glaucoma treated with a Scheie procedure and 16 mm Hg in those with trabeculectomy with a sutured scleral flap). In this study the long-term visual result was apparently no different with the Scheie procedure and trabeculectomy. Trabeculectomy causes fewer flat anterior changes than the Scheie procedure. The degree of pressure lowering in trabeculectomy is directly related to the amount of postoperative filtration. The relative indications for trabeculectomy include: (1) malignant glaucoma in the other eye; (2) chronic angle closure glaucoma where an iridectomy is considered insufficient; (3) "high pressure glaucoma" where pressure below 20 mm Hg is not essential; (4) low inflow glaucoma in which persistent flat anterior chambers may be expected following routine filtration surgery; and (5) cases where endophthalmitis is a real concern, as in the very young, those remote from medical care and those with poor personal hygiene. Trabeculectomy gives such poor results in secondary glaucoma that the procedure is probably relatively contraindicated. Trabeculectomy is a valuable operation, but not the final solution to glaucoma surgery. It should be chosen with full recognition of its specific advantages and disadvantages.