Are There Problems with Non-penetrating Glaucoma Surgery?

In 1989, Koslov et al. described ‘deep sclerectomy’ (DS): an ‘en-bloc’ resection of the external wall of Schlemm’s canal, along with corneal stroma adjacent to the anterior trabeculum and, more anteriorly, exposure of Descemet’s membrane over 4–5 mm. These structures were removed with a slice of sclera beneath a superficial scleral flap: hence the term deep sclerectomy. In 1998, Vaudaux et al. demonstrated increased aqueous humor outflow, while protecting the eye from hypotony-related complications. At that time, Watson et al.’s trabeculectomy complications included 28 % with iridocorneal touch, a further 1 % with lenticulo-corneal touch, and early intraocular pressures (IOPs) of ≤5 mmHg in 25 % of eyes; Popovic’s series had IOPs ≤5 mmHg in one in three patients at one week post-operatively; Migdal and Hitchings reported that 29 % of patients had IOPs ≤8 mmHg for over two weeks post-operatively; Stewart et al.’s results showed 76 % with IOP <5 mmHg and 47 % with iridocorneal touch, both at two days post-operatively. Despite these rates of complications occurring early in the post-operative period, trabeculectomy became established as the technique of choice for glaucoma. It was considerably safer than its predecessors, namely anterior and posterior lip sclerectomy, iridencleisis, and posterior lip sclerectomy with or without cautery. Today, post-trabeculectomy complication rates are far less high than these owing to improvements in surgical technique. At the time, however, they were the benchmark, driving the search for an alternative. Koslov’s deep sclerectomy was appealing.