The Effect of Glaucoma Surgery on Aqueous Dynamics in Patients With Glaucoma or Ocular Hypertension

There are currently many surgical options for patients with glaucoma and ocular hypertension (OHT), including trans-trabecular meshwork surgery with or without an implant, trans-scleral surgery with or without implant, ciliary body treatment, suprachoroidal surgery with or without implant, external non-incisional treatment. However, little is known about how these different surgical techniques used to treat glaucoma affect the flow of fluid through and out of the eye (aqueous dynamics).

One hundred and fifty patients with open angle glaucoma or OHT who are deemed to require glaucoma surgery clinically will be included in a prospective interventional study to investigate the effect of a number of surgical interventions (as listed above) for glaucoma on aqueous dynamics and also to investigate the influence of baseline aqueous dynamics on the eventual outcome of the different surgical techniques. The contralateral non-operated eye will be used as control where possible.

Participants will undergo pre-operative baseline measurement of aqueous dynamics parameters (intraocular pressure (IOP), aqueous flow rate, tonographic outflow facility) 2-8 weeks after stopping to use their eye drops for glaucoma. This stopping of glaucoma drops, or treatment 'washout', is considered an intervention as it deviates from the participants' usual care. Intraocular pressure will be measured using an ocular response analyser (ORA), the outflow facility will be measured by electronic Schiøtz tonography, and the aqueous flow rate will be measured by fluorophotometry. The uveoscleral outflow will be calculated using the Goldmann equation.

Measurement of aqueous dynamics parameters will be repeated 3 months and 12 months after surgery at post-operative follow-up appointments. The follow-up measurements of aqueous dynamics parameters will also be made after 2-8 weeks treatment washout where participants have to continue to use medication for their glaucoma after the surgery. Paired student t-tests will be used to compare aqueous dynamics parameters before and after surgery.

A number of additional eye test procedures will also be performed to collect data for the study at the pre-operative baseline appointment and at routine post-operative follow-up assessments 3 months and 12 months post-surgery. Other data will be collected from eye tests that are routinely performed at the pre-operative appointment and at post-operative follow-up appointments: 1 day, 1 week, 1 month, 3 months, 6 months, and 12 months after surgery.