2 The condition, current treatments and procedure
2.1 Glaucoma is usually a chronic condition associated with raised intraocular pressure. The most common type of glaucoma in the UK is primary (or chronic) open-angle glaucoma. It leads to progressive damage to the optic nerve. Early stages are usually asymptomatic. But, as the condition progresses, it causes visual impairment and, if untreated, blindness.
2.2 NICE's guideline on glaucoma describes its diagnosis and management. Treatment is usually eye drops containing drugs that either reduce aqueous humor production or increase its drainage. Surgical procedures such as trabeculectomy, drainage tubes, deep sclerectomy, viscocanalostomy, laser trabeculoplasty and cyclodiode laser treatment may also be used.
2.3 Repetitive short-pulse transscleral cyclophotocoagulation (commonly known as micropulse transscleral cytophotocoagulation) uses a laser to target the same tissue as conventional cyclodiode laser treatment but it is delivered in pulses lasting microseconds. This allows the tissue to cool between pulses, with the aim of reducing collateral damage.
2.4 The procedure is normally done under local or general anaesthesia and usually takes 10 to 20 minutes. A probe is applied to the surface of the eye with firm pressure and moved in a continuous sliding motion over the upper or lower limbus of the eye, or both. To prevent ciliary neurovascular injury, the 3 and 9 o'clock positions are avoided. The device is set to deliver repetitive short-pulse (micropulse) laser energy with specified 'on' and 'off' times. Lower laser settings are used for patients with higher pigments to avoid overtreatment and inflammation. The laser treatment usually lasts between 100 seconds and 360 seconds per session. After the procedure, patients may need to wear an eye patch over the treated eye for about 24 hours and may be prescribed topical corticosteroids and antibiotics.