Postoperative Assessment Following Istent Inject® W (Glaukos™) Implant With Nidek Gs-1 Automated Gonioscopy

iStent inject® W (Glaukos™) is designed to be inserted through the trabecular meshwork (TM). The injector contains 2 stents, that are advised to be placed at least 2 clock hours apart from each other, in order to achieve maximal efficacy¹. Gonioscopy is used to assess stents’ position postoperatively. However, manual gonioscopy is subjective and offers a brief image of the iridocorneal angle (ICA). Automated gonioscopy has been proposed to be a more objective alternative for ICA examination². The purpose of this study is to evaluate the postoperative outcomes of iStent by using an automated gonioscope.  

A retrospective observational study involving imaging of patient eyes in a one of the largest tertiary eye units along the south coast in the United Kingdom.

Observational study. Patients diagnosed with open                angle glaucoma underwent phacoemulsification combined with iStent inject® W. The ICAs were imaged with NIDEK GS-1 automated gonioscope (NIDEK™, Japan), 1 months postoperatively. Two independent observers graded stents’ position as follow: 

• ·      “correct position”: placed within TM
• ·      “incorrect position”: placed anterior or posterior to the TM
• ·      When two stents were placed in the same eye, the distance between them was also graded: 
• ·      “correct distance”: stents were equal to or more than 2 clock hours apart
• ·      “incorrect distance”: stents were less than 2 clock hours apart

Thirty-two iStents from 16 eyes were imaged. Three images were excluded due to poor quality. Overall IOP reduction of 14.3 % (p=0.049) was observed one month postoperatively. Two eyes (10.5%) had only one stent implanted. Twenty-three (71.8%) stents were graded in “correct position” by both observers. Seven eyes were graded as having “correct distance” between stents by both observers. Of them, 6 were also deemed to have “correct position” for all stents. The IOP reduction observed in eyes with both stents in “correct position” and “correct distance” was 21.3% (p=0.181); while that one observed in eyes with either only 1 stent, or “incorrect position” or “incorrect distance” was 10.2% (p<0.05)

We observed an IOP reduction whether or not iStents were placed on target location (“correct position” and “correct distance”) . Stents on target location were more effective than those not on target location. NIDEK GS-1 automated gonioscope provided an overall good image quality and agreement between observers