Trabeculectomy is one of the most effective surgeries for the management of glaucoma.1 Although Medicare claims data reported a 43% decrease in the number of trabeculectomies in the US.2 it is still the most common glaucoma procedure in the world. However, cataract progression is one of the common consequence of the procedure.3 In Advanced Glaucoma Intervention study (AGIS), approximately half of the study patients developed cataract in the first five years of follow-up. Serious postoperative complications are not uncommon after this procedure and are associated with increased risk of cataract formation.3
Another common scenario for the glaucoma specialists is patients with coexisting cataract and glaucoma. The options are: to perform cataract extraction followed by trabeculectomy, perform trabeculectomy first followed by cataract extraction, or perform a combined procedure. To decide on the best course of action, it is important to have good quality data. Few studies have assessed the risk associated with phacoemulsification following trabeculectomy over a long-term follow-up period.4,5
Arimura and colleagues have published the five-year IOP outcomes of trabeculectomy followed by phacoemulsification in Japanese patients which compared to the outcomes of trabeculectomy alone.6 A total of 1,098 eyes of patients with glaucoma in Collaborative Bleb-Related Infection Incidence and Treatment Study (CBIITS) who underwent trabeculectomy with 0.04% mitomycin C at 34 clinical centers were evaluated. Patients were enrolled for two years and followed up every six months for up to five years. Surgical failure was defined on the basis of mean IOP as follows; < 20% reduction in preoperative IOP or postoperative IOP of ≤ 21 mmHg (criterion A), ≤ 18 mmHg (criterion B), or ≤ 15 mmHg (criterion C), respectively. Additionally, surgical failure was defined the case required reoperation for glaucoma or developed loss of light perception or low IOP (≤ 5 mmHg).
In this cohort, 40 eyes that were treated with trabeculectomy followed by phacoemulsification and 208 eyes who had undergone trabeculectomy alone were analyzed. Meaningful differences were found in the five-year cumulative probabilities of success A, and success B (≤ 18 mmHg) between the trabeculectomy followed by phacoemulsification (40%, and 35%) and trabeculectomy alone (59.1%, and 52%.9) groups (P = 0.01 for both).
Optimal time for phacoemulsification to reduce the risk of trabeculectomy failure has been controversial
Optimal time for phacoemulsification to reduce the risk of trabeculectomy failure has been controversial. Bleb remodeling lasts for at least six months after surgery; thus, premature timing of phacoemulsification before the completion of bleb remodeling might accelerate bleb fibrosis and does not recommended.7 Most of the patients in the present study (36 eyes) underwent phacoemulsification after one year of trabeculectomy. Nonetheless, the authors demonstrated that shorter time gap between trabeculectomy and phacoemulsification was significantly associated with surgical failure (HR = 1.02) even with longer gap. Five eyes were subjected to phacoemulsification within one year after trabeculectomy, and surgical failure on the basis of all criteria was observed in four of the five eyes. This results are in line with to an earlier study which showed that the hazard ratios are 3.0, 1.7, and 1.3 for six months, one year, and two years after trabeculectomy, respectively.
However, their reported hazard ratios of the time interval between trabeculectomy and phacoemulsification were small and this analysis assumed a linear association between the timing and the outcome. As supported by their data and the previous studies, IOP outcomes were affected more profoundly when the cataract surgery was performed within one year of the trabeculectomy. One should know that the study was not randomized and the patients' characteristics and surgical techniques for trabeculectomy used by the study centers or surgeons were not identical and may subject to biases. For example, one-third of the trabeculectomies has been done using fornix-based approach. Additionally, the trabeculectomy-alone patients were eight years younger, which may affect the surgical success of the filtration surgery.
Cataract surgery within one year after trabeculectomy dramatically affect the success rate and should be avoided unless it is necessary
The current report agrees with other studies that phacoemulsification following trabeculectomy adversely affects surgical outcomes and a shorter time gap between trabeculectomy and phacoemulsification reduces the probability of success. Cataract surgery within one year after trabeculectomy dramatically affect the success rate and should be avoided unless it is necessary.