Aqueous Release to Treat IOP Spikes Post-cataract Surgery

Efficacy and Safety of Aqueous Humour Release (Burping) Performed at the Slit-lamp to Treat Acute Intraocular Pressure (IOP) Spikes Post-cataract Surgery

Intraocular pressure (IOP) rise after cataract surgery is an important and common problem. Over 300,000 cataract operations are done per year in the United Kingdom alone. IOP rise can adversely affect vision and can be particularly detrimental in glaucoma patients with pre-existing visual field defects. The aim of this study is to evaluate the efficacy and safety of aqueous humor release (also known as burping of the wound), a procedure that has been used for decades to quickly reduce acute IOP spikes following cataract surgery. Currently there is no published evidence on a standard technique to perform wound burping. Similarly there is uncertainty around the amount and duration of the IOP decrease, and the type and frequency of complications eventually associated. This will be the first research project formally evaluating this procedure. This study will also help allay issues over fluid release in high IOPs and consequences of such dramatic IOP drop which concerns ophthalmologists who do not routinely use this technique.

At present there is no de facto standard to manage acute intraocular pressure (IOP) rise following cataract surgery. Several drugs, both topical and systemic, have been tested for their ability to blunt the acute IOP spike, nevertheless none has proven to be superior and consistently effective. Oral acetazolamide has demonstrated to help controlling IOP spikes following cataract surgery in glaucomatous eyes. However there are still constraints in its widespread use, as it may be contraindicated in patients with poor renal function, sickle cell disease and sulpha drug allergy. As a result, many units including Moorfields Eye Hospital have used a technique called known as 'burping of the corneal wound' to release fluid from inside the anterior chamber of the eye. This makes logical sense as it reduces the pressure immediately and may remove some of the causes for raised IOP such as retained viscoelastic and inflammatory molecules from inside the eye. This technique has also been used to reduce IOP in patients already receiving pharmaceutical treatment. The technique has been used for decades, however, there is no published evidence of a proposed technique, range of IOP decrease or frequency of complications. Thus, most surgeons in most units are cautious of 'burping the wound' as it may induce infection or other complications compromising the surgical outcome due to the sudden reduced IOP reduction. Nevertheless a similar approach, needle penetrating the eye to release aqueous and reduce IOP, is becoming more popular as the first approach to treat an acute angle closure crisis, where the presenting IOP is often very high, i.e. a much more difficult and dangerous situation than post cataract surgery.

Following uneventful cataract surgery, wound "burping" will be performed in all eligible patients who gave their informed consent. The procedure will be offered whenever the intraocular pressure (IOP) is either higher than 30 mmHg or deemed inappropriate in view of the ocular condition (e.g. glaucoma). After 'burping' the wound, patients will have their IOP measured using Goldmann application tonometry (GAT) immediately and at 2 hours. The 'burping' procedure will be repeated until satisfactory pressure is achieved and care will be taken to avoid shallowing of the anterior chamber while fluid is released. We will assess for the presence of leaks from the wound with a Seidel test with fluorescein 5% once the IOP is satisfactory. To prevent any infection after each procedure, we will prescribe post-op drops including chloramphenicol 0.5% four times a day for 2 weeks or minimum of 3 days and these will continue as per routine. All other complications will be recorded at follow-up.

Anaesthetic drop (tetracaine 1%) followed by povidone iodine 5% drop is instilled. After 5 minutes, a sterile 30 gauge needle tip is pressed on the posterior lip of the one of the existing cuts (paracentesis or main wound) from cataract surgery to release the fluid and consequently the pressure. This will be performed under careful monitoring to avoid any undesirable shallowing of the anterior chamber of the eye.

Efficacy of 'burping' the wound to reduce IOP (mmHg) post-cataract surgery when measured using Goldmann application tonometry (GAT)

Observing the frequency of complications, including but not limited to, severe pain, worsening of vision, or infection

Inclusion Criteria: Patient whose post-operative IOP was regarded to be too high for visual safety, or higher than 30mmHg, on the same day or within 1 week of the surgery Exclusion Criteria: Patients with IOP less than 30 mmHg or IOP deemed by clinician not too high to treat Patients unable to cooperate Patients who have undergone complicated cataract surgery

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