Observation or Laser Peripheral Iridotomy? – Implications of the ZAP Trial

Pearls Manager: Hari Jayaram

The ZAP study was a single-centre randomised clinical trial performed in China to compare Laser Peripheral Iridotomy (LPI) to no treatment in asymptomatic Primary Angle Closure Suspects. The primary outcome measure was Incident Primary Angle Closure Disease (composite endpoint of high IOP, PAS or acute angle-closure)

After 7 years, 19/889 (2.1%) LPI eyes vs 36/889 (4.1%) untreated eyes developed angle-closure disease. The rate of developing any angle closure endpoint was less than 1% per year in PACS. Eyes that underwent LPI had a 47% reduction in the risk of developing angle-closure disease (HR 0.53, 95% CI 0.30–0.92, p=0.024).

• Prophylactic LPI is of modest benefit in PACS • The risk of PACS developing primary angle closure over a 6 years period is low • Number needed to treat: 44 to prevent one case of new primary angle closure disease over 6 years • The ZAP data do not support the widespread practice of LPI iridotomy in PACS, although further evidence is required to support this practice in non-Chinese Populations

EGS Guidelines, 5th Edition, Page 42