Why primary angle-closure glaucoma is declining in Scotland
The prevalence of acute primary angle-closure glaucoma (APACG) is declining in Scotland as cataract surgery becomes more common, researchers said.
“We propose that increasing rates of cataract surgery performed at an earlier age group in Scotland have played a significant role in reducing the rate of APACG by reducing the incidence of obstruction and the level of lens and papillary block mechanisms,” wrote Stewart N. Gillan from Ninewells Hospital and Medical School in Dundee, United Kingdom, and colleagues.
They published their finding in Ophthalmic Epidemiology.
The researchers defined APACG as iridotrabecular contact resulting in peripheral anterior synechiae and/or raised IOP, causing glaucomatous optic neuropathy.
They enumerated four possible mechanisms for the condition: pupil block, obstruction at the level of the iris and/or ciliary body (plateau iris), obstruction at the level of the lens, and obstruction posterior to the lens (aqueous misdirection syndrome).
Six risk factors they reported include: older age, female sex, hypermetropia, lenticular changes, use of pharmaceutical products, and East Asian ethnicity.
Despite predictions that the prevalence of APACG, a leading cause of blindness, is set to rise worldwide, some authors have reported a decline in certain countries.
To situate Scotland in this context, Gillan and his colleagues analyzed national data from the Information Services Division (ISD) Scotland, which includes all activity carried out across the 14 Scottish health boards, including National Health Service (NHS) patients treated in private hospitals. (None of the private Scottish hospitals have emergency ophthalmic facilities.)
They counted the number of NHS patients diagnosed principally as having APACG, the number who underwent YAG laser peripheral iridotomy, and the number who had cataract surgery as an inpatient or day case, from 1 April 1998 to 31 March 2012.
They found that the number of patients coded for APACG dropped 46.4%, from 46.7 per million to 25 per million, a statistically significant change (P < 0.005).
Meanwhile, the rate of cataract surgery went up 73.4%, from 354.2 per 100,000 to 615.2 per 100,000, which was also significant (P < 0.005).
In addition, the rate of peripheral iridotomy spiralled 116.3%, from 38.0 per million to 82.2 per million. Even more striking, this increase took place in the most recent period; peripheral iridotomy actually decreased by 48.2% from1998 to 2008, before rocketing back up by 317.% between 2008 and 2012.