A comparison of total and parietal tenonectomy with trabeculectomy

Glaucoma is an eye disease characterized by elevated pressure (above 21 millimeters of mercury, mmHg) within the eye caused by obstruction of the outflow of aqueous humor from the anterior chamber (portion of the eye between the cornea and the lens). This condition causes gradual loss of peripheral vision, and possibly later loss of central vision. Glaucoma that remains uncontrolled despite apparently adequate medical treatment may be treated surgically, by trabeculectomy, a procedure allowing drainage of the aqueous humor beneath the conjunctiva by connecting the anterior chamber of the eye with the subconjunctival space. There is disagreement over the benefit of removing part or all of Tenon's capsule, the membrane that envelops the eyeball from the back to the area of the iris. A study was carried out of 49 eyes before trabeculectomy; 23 underwent partial tenonectomy (excision of Tenon's capsule), and 26 underwent total tenonectomy. A final intraocular pressure below 18 mmHg was achieved in 19 of 23 patients (83 percent) in the partial tenonectomy group, and in 18 of 26 patients (69 percent) in the total tenonectomy group. A pressure below 21 mmHg was obtained by 87 percent of the partial group, and 81 percent of the total group. There was no significant statistical difference between the two groups. It is concluded that equivalent results may be expected using either procedure. A total tenonectomy requires more careful dissection and may be associated with inadvertent creation of a hole. Therefore, a partial tenonectomy, in most cases, has intraoperative advantages over total tenonectomy. (Consumer Summary produced by Reliance Medical Information, Inc.)