A prospective contralateral-eye study has found that trabecular micro-bypass surgery with the iStent inject significantly improves signs and symptoms of ocular surface disease (OSD) compared with continued topical glaucoma therapy, alongside a marked reduction in medication burden.
The Norwegian single-centre study followed 28 patients with bilateral mild-to-moderate open-angle glaucoma, implanting an iStent inject in one eye while the fellow eye continued intraocular pressure (IOP)-lowering drops. Ocular surface outcomes were assessed over six months using objective clinical measures and validated symptom questionnaires.
At six months, eyes treated with iStent inject showed a 79% reduction in glaucoma medication use, falling from a mean of 1.9 medications preoperatively to 0.4. In contrast, medication use remained largely unchanged in control eyes continuing topical therapy.
This reduction in medication burden was associated with significant improvements in ocular surface health. Study eyes demonstrated meaningful reductions in bulbar conjunctival redness and corneal staining, measured using keratograph imaging and the Oxford ocular surface staining (OSS) scale. Improvements in both parameters were significantly greater in iStent-treated eyes than in fellow eyes maintained on drops.
Patient-reported symptoms also improved despite unilateral intervention. Mean Ocular Surface Disease Index (OSDI) scores fell from 18.4 at baseline – consistent with mild OSD – to 9.3 at six months, while SPEED II scores nearly halved. The magnitude of OSDI improvement exceeded the established minimal clinically important difference, suggesting the changes were not only statistically significant but clinically meaningful.
Importantly, many other ocular surface parameters – including tear osmolarity, tear meniscus height, tear film thickness, Schirmer testing, meibomian gland dropout and meibum expressibility – remained stable in both groups, indicating that the observed benefits were not offset by new surface compromise following surgery.
While non-invasive tear break-up time (NIKBUT-first) worsened transiently in the iStent group, average NIKBUT values were unchanged at six months. The authors suggest this may reflect temporary postoperative effects rather than deterioration in tear film stability, particularly given improvements in other ocular surface markers.
A subgroup analysis excluding eyes that underwent cataract surgery showed similar trends, supporting the conclusion that improvements were attributable to reduced topical medication exposure rather than phacoemulsification.
IOP reduction at six months was comparable between groups, despite the substantial difference in medication use. No intraoperative or postoperative complications related to stent implantation were reported, and visual outcomes were maintained.
The authors conclude that interventional glaucoma treatment with trabecular micro-bypass stents can deliver ocular surface benefits alongside IOP control by reducing long-term exposure to topical medications. Given the high prevalence of OSD in glaucoma patients and its impact on adherence and quality of life, the findings support considering ocular surface health when selecting treatment pathways in mild to moderate disease.
The study, published in Clinical Ophthalmology, adds to a growing body of evidence positioning minimally invasive glaucoma surgery as a means not only to lower IOP, but also to mitigate treatment-related ocular surface toxicity.
