Advances in glaucoma treatment and management: surgery.

Ever since the first glaucoma surgery in 1856, the goal has been to decrease intraocular pressure (IOP), the only modifiable risk and prognostic factor for glaucoma. Over the years, reduction of IOP has been achieved by surgical manipulation of the aqueous inflow or outflow pathways. The glaucoma surgeries that have been developed to affect the inflow pathway have involved the destruction of the ciliary body, the tissue that makes the aqueous, whereas those that affect the aqueous outflow pathway involve either internal or external filtration. With internal filtration, the outflow pathways are manipulated so that they function better; with external filtration, the eye’s natural outflow pathways are bypassed. After the introduction of prostaglandin analogue medications in 1996, the frequency of all types of glaucoma surgery decreased, including the most common type, argon laser trabeculoplasty. In early 2000, a new type of laser surgery, selective trabeculoplasty, was developed and was reported to be less destructive than argon laser trabeculoplasty. 1 Since then, the frequency of laser trabeculoplasty procedures has gradually increased to pre‐prostaglandin-analogue levels (personal communication, H. Dunbar Hoskins, Jr, MD, Center for Quality Eye Care, June 6, 2011). The most frequently used intraocular surgery for glaucoma has been the trabeculectomy, which involves the creation of a partial-thickness scleral flap over a sclerectomy into the anterior chamber. Although this type of external filtration has been regarded as safer than the prior full-thickness sclerectomy, which does not have a partial-thickness flap limiting the flow of aqueous out of the eye, several new surgeries have been developed with the goal of improving on or replacing the trabeculectomy. Thus, in many new-device trials, the standard with which the new device or surgery is compared is a trabeculectomy. Since many of these studies have limitations, of which clinicians should be aware, the goal of this article is to review some of the most recent advances in incisional glaucoma surgery. In a literature review of trabeculectomies, Rotchford and King 2 identified 100 studies published between 2000 and 2005. Only 31 were randomized clinical trials; 53 were retrospective series. The best evidence for supporting clinical decisions is from randomized clinical trials, which involve the random assignment of patients to one procedure or another, an approach that prevents unknown biases from changing or affecting the results. Without randomization, it is difficult to know whether one procedure is better than another. In the 100 studies, there were 92 distinct IOP-related definitions of success, making it very difficult to compare the results of the studies, in which success rates ranged between 36% and 98% after 3 years of follow-up. Such a wide range of expectations for success makes it very difficult for a surgeon to obtain consent from a patient. The drive to create a better or different surgical procedure to lower IOP arises not only from the limited success rates of trabeculectomies but also from the short- and long-term risks of endophthalmitis (ocular infection) and ocular hypotony (too low IOP) after trabeculectomy. Unfortunately, 99 of the 100 studies did not report information on either visual function or optic nerve progression parameters. Although lowering of IOP is often used as a surrogate treatment goal for glaucoma management, the ultimate goal is to preserve visual function. Without information on visual function before and after surgery or across surgical groups, assessment of the success of the surgery is limited to IOP and thus does not capture the whole story.