Improving the Function Of XEN (iFOX) Study

The greatest risk factor for glaucoma is intraocular pressure (IOP). Management of glaucoma aims to reduce IOP and glaucoma surgery involves increasing the outflow of aqueous humour from the eye to achieve this. XEN gelatin stent surgery delivers a consistent non-inflammatory and flexible stent to form a drainage connection between the anterior chamber of the eye and the subconjunctival space. The fluid from the eye drains out through the stent to form a blister (bleb) in the surrounding tissue which is vital for long term success. This project will allow the long term collection and analysis of data to help improve patient outcomes. Multiple surgical variables may influence post-operative outcomes and success rates of the surgery. These include the entry position, dimensions of the stent within different parts of the eye and the final position of the stent. Other non-surgical factors which are likely to play a role in terms of surgical success include age, sex, racial sub-type and disease (glaucoma) sub-type. The three major endpoints in terms of judging surgical success rates are IOP reduction, number of pressure lowering medications (eye drops) used and drainage area (bleb) shape and appearance. This will be a prospective observational study over a 12 month period after XEN surgery. Patients who have already undergone surgery will be asked to participate as well as patients about to undergo surgery. The first phase will involve collecting all of our currently performed XEN gelatin stent patient data, following informed consent and collating that. Data will be collected from patient records and a local clinical database at the Lions Eye Institute from 19/08/19 - 19/08/2021. We will collect IOP measurements, medication usage, bleb appearance (using a standard grading scale), 5-fluorouracil needling usage and complications on these patients in addition to relevant medical information from the patients’ medical records such as previous procedures. We will also have full demographic record including age, sex, race as well as their diagnostic classification. Patients will be followed for at least twelve months and all of their data concerning variables important for this trial will be entered into a specially modified database. These data will include the baseline demographic disease causation data. They will include the anatomical site of insertion through the angle, length of tube position in the three anatomical sites (anterior chamber, scleral, subconjunctival) as well as position around the limbal circumference in clock hours. Intraocular pressure and medication use data will be collected at baseline pre-operatively, one month, two months, three months, six, then at 12 monthly intervals for analysis. Visual acuity at final visit will be recorded and compared to baseline. The number of 5-fluorouracil injections/needling procedures performed post-operatively within the first twelve months will be recorded. The 12 month visit will be the most important data collection visit. We will also perform anterior segment optical coherence tomography (OCT) imaging using infrared light of the gel microfistula within the scleral and subconjunctival space so that descriptive measures of the intrascleral portion may be documented as well as exact positioning of the termination of the gel stent within the subconjunctival space be identified (anterior tenon’s, mid-tenon’s, deep tenon’s/episcleral). We will also take slit lamp photographs of the bleb and XEN gelatin stent beneath the conjunctiva. We will use these images to validate our clinical grading scheme recorded directly from the clinic. The Indiana Bleb Grading Scheme specifically details degrees of vascularity, including avascular and cystic changes within the bleb along with bleb leaks, bleb size and height.