NHMRC Glaucoma Guidelines - ANZGIG

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NHMRC GUIDELINES FOR THE SCREENING, PROGNOSIS, DIAGNOSIS, MANAGEMENT AND PREVENTION OF GLAUCOMA Chapter 10 – Laser therapy and surgery Summary of common laser interventions Laser iridotomy Laser iridotomy is used to treat angle closure. This technique creates a hole in the iris in order to break the pupil block, which is the most common cause of angle closure. It is most frequently undertaken by Nd:YAG laser iridotomy, however when this form is not available, an argon laser may be utilised (European Glaucoma Society [EGS] 2003). Laser iridoplasty Laser iridoplasty is used in angle closure following iridotomy when the angle remains appositionally closed or occludable. Contraction burns are applied to the peripheral iris to pull it away from the trabecular meshwork. Laser trabculoplasty Laser trabeculoplasty is used in open angle glaucoma. Applications to the trabecular meshwork alter the drainage tissue, generally increasing aqueous outflow. Combination laser surgery Iridotomy is often combined with iridoplasty, where laser is applied to shrink the peripheral iris away from the trabecular meshwork to improve the aqueous flow. Cyclodestructive procedures Transcleral cyclophotocoagulation is a form of laser therapy which treats glaucoma by damaging the ciliary body. The laser is aimed through the sclera at the ciliary body, which secretes aqueous humor. This form of laser treatment lowers IOP by decreasing aqueous humor production. Currently, cyclodestructive procedures are commonly performed using a transscleral laser delivery system, however they can also be performed endoscopically (Pastor et al 2001, cited in American Academy of Ophthalmology [AAO] 2005b). Laser options for specific glaucoma classification and stages Open angle glaucoma Literature reviews of controlled trials of argon laser trabeculoplasty report an average reduction in IOP of 30% in most eyes with primary open angle glaucoma (POAG) (Royal College of Ophthalmologists [RCO] (2004). However in clinical practice the effectiveness of laser therapy is influenced by patient risk factors including age (tends to be less successful in young patients), and type of glaucoma (tends to be more successful in pseudoexfoliation and pigment dispersion glaucoma). There appears to be a progressive diminution of the effect of laser therapy over time in some patients, and glaucoma control can be lost quickly. Therefore patients who have had laser treatment should be monitored frequently. National Health and Medical Research Council 141
NHMRC GUIDELINES FOR THE SCREENING, PROGNOSIS, DIAGNOSIS, MANAGEMENT AND PREVENTION OF GLAUCOMA Chapter 10 – Laser therapy and surgery The literature indicates that one year after laser therapy, for open angle glaucoma (OAG) the condition is successfully controlled in approximately 80% of patients (American Optometric Association [AOA] 2002). After the first year, this rate declines by about 5−15% per year. In general, glaucoma is successfully controlled in approximately 50% of patients five years after laser therapy and 10–30% of patients 10 years after laser therapy (AOA 2002). When laser trabeculoplasty is given as primary treatment, approximately 50% of patients do not require medication for one to two years after treatment (Tuulonen, Airaksinen, Erola et al 2003). The IOP-lowering effect of laser trabeculoplasty diminishes by approximately eight percent per year and follow-up of up to seven years suggests that only 20% of patients manage without medication (Tuulonen et al 2003). Repeated laser therapy has a lower success rate and a higher risk of poor outcomes than one administration of laser therapy only (AOA 2002). Selective laser trabeculoplasty appears to be equivalent to argon laser trabeculoplasty in lowering IOP. Patients who previously failed to improve with argon laser trabeculoplasty may have a greater reduction in IOP when treated with selective laser trabeculoplasty (AOA 2002). Usually, medications should continue following laser therapy, and in only 25% of cases can it be reduced from pre-laser levels. The risk of failure to control the progression of glaucoma with laser therapy is higher in younger patients, when pre-treatment IOP is very high, and when glaucoma is more severe (AOA 2002). Evidence Statements • Evidence strongly supports argon laser trabeculoplasty for older patients with glaucoma who are at risk of visual loss within their lifetime, particularly when the following factors apply: −−there is difficulty with administering eye drops −−patients are unresponsive to medication alone, or −−patients are poor candidates for incisional surgery. • Expert/consensus opinion suggests that patients undergoing laser therapy require continual comprehensive glaucoma monitoring due to the diminishing treatment benefit over time. Communication with patients Irrespective of the way in which glaucoma is managed, health care providers should continue to educate patients about the need for monitoring. They should ensure that patients understand that even if successful, laser therapy does not equate to a cure. point of note Expert opinion indicates that the high success rates of argon laser trabeculoplasty obtained in clinical trials may not be easily achieved in clinical practice. point of note After a patient undergoes laser therapy, the health care provider responsible for long-term monitoring should be clearly identified, particularly when medication is no longer required. 142 National Health and Medical Research Council
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NHMRC Glaucoma Guidelines - ANZGIG

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