Comparing Postoperative Visual Field Changes Following Cataract Extraction Combined With Glaucoma Drainage Device (Gdd) Placement, Istent Implantation, Or Trabeculectomy

Combined cataract extraction with glaucoma surgery has been shown to stabilize or even improve visual field loss following surgery. However, no study has fully examined differences in visual field outcomes between combined cataract extraction with either GDD, iStent placement, or trabeculectomy. This study aims to fill this gap in knowledge by comparing visual field changes between patients with moderate and severe open angle glaucoma (mean deviation (MD) -3 to -12db and worse than -12db, respectively) who have undergone combined cataract extraction with GDD, iStent placement, or trabeculectomy. 

This study was performed in the Department of Ophthalmology at Mayo Clinic, a tertiary medical center located in Rochester, Minnesota, USA. 

All patients with a history of open-angle glaucoma who underwent combined cataract extraction with either GDD placement, iStent implantation, or trabeculectomy were identified at a single institution through a customized data recruitment software, OPUS. Mean preoperative and postoperative visual field threshold values were identified in all eyes that underwent surgery. A slope describing change in mean visual field thresholds in moderate and severe glaucoma before and after surgery was identified to measure visual field loss. Kruskal-Wallis test compared slope between the three groups. Pairwise Mann-Whitney U test with Bonferroni correction compared slopes between each group with statistical significance defined as p<0.05. 

27 GDD, 155 iStent, and 144 trabeculectomy eyes with moderate and 24 GDD, 16 iStent and 129 trabeculectomy eyes with severe glaucoma were analyzed. Mean follow-up and age for both groups were: 4.34, 1.70, 4.86 and 66, 73, and 72 for GDD, iStent, and trabeculectomy, respectively. Mean MD in moderate and severe groups respectively was: GDD (-7.08, -20.77), iStent (-5.83, -16.45), and trabeculectomy (-7.17, -18.47). Visual field change differed significantly (p < 0.001). For moderate groups, trabeculectomy had faster decline (-1.91 dB/year) compared to GDD (-0.58 dB/year) and iStent (-0.62 dB/year). For severe, GDD had faster decline (-2.11 dB/year), trabeculectomy mild decline (-1.40 dB/year), and iStent was stabile (0.38 dB/year). 

There is a statistically significant difference in visual field outcomes between cohorts. In patients with moderate glaucoma, who had undergone combined cataract extraction, those receiving trabeculectomy exhibited greater postoperative visual field loss compared to those receiving combined iStent or GDD procedures whereas in patients with severe glaucoma, iStent and trabeculectomy patients had better visual field stability compared to GDD patients. These findings suggest iStent resulted in good visual field stability and trabeculectomy appeared to be superior to GDD in advanced glaucoma to preserve visual field.