5 Year Outcomes In Patients Undergoing Phacoemulsification With Single Istent Implantation (First Generation Istent®, Glaukos Corporation, California) In Comparison To Phaco Alone In A Tertiary Referral Centre With A Diverse Multi-Ethnic Population

Phacoemulsification (phaco) plus procedures that include the newer minimally invasive glaucoma surgery (MIGS) type surgical devices such as the iStent are well established . This retrospective study reports observed outcomes in a large ethnically diverse cohort managed in a tertiary unit, looking at patients who had glaucoma and cataracts and had either a combined phaco with iStent or phaco surgery alone.

Our study aims to establish a longer term safety and efficacy profile of the first generation iStent and importantly also reports on visual field changes over the 5 year post-operative period and changes in required glaucoma medications to clarify if there is a difference between the 2 groups.

MIGS devices are being used increasingly in combination with cataract surgery in patients with glaucoma. We wanted to evaluate the benefits of performing combined cataract surgery with iStent by comparing with a cohort of glaucoma patients who underwent cataract surgery alone.

The surgery for the cataract provides a window of opportunity for iStent insertion which could mean a reduction in glaucoma drop load and improve glaucoma control in patients. 

This study was an observational retrospective longitudinal cohort study carried out at a single centre,  which serves an ethnically  diverse population in London. 47 patients each undergoing phacoemulsifcation followed immediately by a single iStent insertion (model GTS100, Glaukos corporation, California) versus 44 patients who underwent phacoemulsification alone (controls)  were compared over a five year follow up period in patients with open angle glaucoma or ocular hypertension. 

The groups were well matched with no significant difference in mean age, starting visual field mean deviation or diagnoses. We reviewed changes in IOP, visual acuity, number of glaucoma medications,  visual fields, need for further surgery.

The IOPs reduced from 18.19 mmHg pre-operatively to 14.22 mmHg in the control group (p<0.05) and 22 mmHg to 15.15 mmHg in the istent group (p<0.005). The mean number of medications reduced from 2.36 to 1.39 (p<0.05) at 5 years in the iStent group and increased from 0.79 to 1.65 (p<0.05) at 5 years in the phaco alone group. The visual field mean deviation increased from -8.2dB to -11.35 dB in the phaco alone group (p<0.05) and showed no significant change from -8.16dB to -5.91dB in the istent group (p=0.1).  

26% of the phaco-iStent group were independent of drops in contrast to 2.3% in the control group (p<0.05). Over 5 years MD significantly worsened in 34% of the control group, compared to 1 patient in the iStent group (p<0.05%).  

In our cohort of multi ethnic glaucoma patients who started with the same visual field mean deviations our study shows - the control group mean deviation significantly progressed over 5 years in 34% of patients , the overall mean deviation was unchanged in the istent group, with 3 (6%) patients showing progression (P<0.05).  This analysis demonstrates that functionally, the iStent patients had much better functional outcomes, with less visual field progression in this group which was statistically significant.

With regards to glaucoma medications our results demonstrate that the istent cohort were better controlled on fewer medications and that indeed a quarter of patients were not on any medication  at 5 years compared to controls.