Position of the ISTENT Inject® Trabecular Micro-Bypass System Visualized with the NIDEK GS-1 Gonioscope—A Postoperative Analysis

Abstract

Glaucoma is one of the leading causes of irreversible blindness globally and is characterized by the gradual loss of retinal ganglion cells. The primary risk factor for the development and progression of glaucoma is increased intraocular pressure (IOP). Numerous surgical interventions exist to lower IOP should conservative therapy fail. One trend in recent years has been minimally invasive glaucoma surgery (MIGS) as an alternative to traditional methods. The ISTENT inject® is an ab interno trabecular micro-bypass implant designed to be implanted through the trabecular meshwork into the Schlemm’s canal to lower IOP. The aim of the study was the postoperative visualization and description of the positioning of the ISTENT inject® using automated circumferential goniophotography. Patients with symptomatic cataracts and mild to moderate primary open-angle glaucoma (POAG), pseudoexfoliation glaucoma (PEX), and pigment-dispersion glaucoma were included who underwent combined cataract surgery with the ISTENT inject® and received postoperative automated gonioscopy with the NIDEK Gonioscope GS-1 to visualize the location of the implant. Twenty-four implants of 14 eyes in 11 patients could be visualized. Out of the implants, 14.3% were in the trabecular meshwork, 46.4% were at the border between the trabecular meshwork and scleral spur, 25% were below the trabecular meshwork, and 14.3% of the implants were not detectable in the gonioscopy. In the overall cohort, a statistically significant IOP reduction was found over the 12-month postoperative observation period. Even in three eyes, in each of which both stents were located below the trabecular meshwork, an IOP reduction over 12 months was observed compared to the baseline IOP. In this study, vertical two-dimensional positioning of the ISTENT inject® was performed for the first time using NIDKE GS-1 automated 360° goniophotography. The method is suitable for postoperative visualization, control, and documentation of positioning after ISTENT inject® implantation. Further studies are needed to analyze the correlation between positioning of the ISTENT inject® in the chamber angle and postoperative IOP reduction.

iStent insertion orientation and impact on trabecular meshwork motion resolved by optical coherence tomography imaging

“…Apart from the OCT result, the iStent position was also evaluated by gonioscopy, following a recently published grading system. 9 Grade 1 refers to the most anterior position that inserted in the anterior TM, grade 2 represents the posterior TM insertion, grade 3 represents the scleral spur insertion, and grade 4 represents the most posterior position that inserted in the region below the scleral spur. The grading results are provided in Table 2.…”

“…However, it is crucial to note that gonioscopy is a contact imaging technique, and its limitations include the inability to detect the iStent below the tissue surface, resulting in a non-detectable rate of ∼15%. 9,10 In contrast, optical coherence tomography (OCT) is a non-invasive imaging modality capable of obtaining depth-resolved reflectivity profiles beneath the tissue surface. 11 OCT structural imaging has been utilized to gather morphological and positional information of the iStent, 12 as well as to assess SC dilation.…”