New technology predicts conversion to POAG
Clinicians can predict which patients with ocular hypertension (OHT) are most likely to develop primary open-angle glaucoma (POAG) using short-wave automated perimetry (SWAP), scanning laser polimetry (SLP) and confocal laser ophthalmoscopy (CSLO), as well as the patient’s age, according to researchers.
"Our study suggests that the combination of patient age with structural and functional variables provided by various instruments could help the clinician in better managing a general population of OHT patients, even if a predictive model alone cannot replace clinical judgment," writes Maria L Salvetat and colleagues.
Dr Salvetat and her colleagues from Azienda Ospedaliero-Universitaria Santa Maria della Misericordia in Udine, Italy, published their findings in Eye.
Although lowering intraocular pressure (IOP) often benefits patients with POAG, it’s not feasible to lower the IOP in everyone with ocular hypertension because of its prevalence, and because of the risk of adverse effects. As such, it would be useful to know which patients with ocular hypertension are at greatest risk of developing POAG.
Previous large studies have identified older age, higher IOP, larger vertical or horizontal cup-to-disk ratio, greater standard automated perimetry (SAP), pattern standard deviation (PSD) and thinner central corneal thickness (CCT) as significant predictors.
Race, positive family history and low diastolic perfusion pressure have also been documented as risk factors.
But new instrumental tests have shown the ability to detect fundamental or morphological glaucomatous damage. Besides SWAP, SLP and CSLO, these include frequency-doubling technology (FDT) and Heidelberg retina tomography (HRT).
A test with ibopamine has also showed promise. A D1-dopamine and alpha-adrenergic agonist, ibopamine induces an increased aqueous humour production and a noncycloplegic mydriasis when instilled in the conjunctival sac.
In previous studies, ibopamine eye drops caused an IOP increase in patients with reduced functioning of the outflow structures, including patients with POAG, normal tension glaucoma, positive family history, and hydrodynamic disorders caused by corticosteroids. Healthy patients, on the other hand, tend to show no influence on IOP with ibopamine.
To see which of these methods was most helpful in predicting the conversion to POAG, the researchers randomly selected one eye in each of 133 patients with ocular hypertension.
All the patients had IOPs at least 24 mm Hg in one eye and greater than 21 mm Hg in the other eye. They all had normal optic disc and retinal nerve fibre layer (RNFL) appearance in both eyes, 2 normal standard automated perimetry visual field (SAP VF) test results in both eyes, best corrected visual acuity at least 0.7, open anterior chamber angles, absence of other ocular pathology, reliable SAP, SWAP and FDT test results, and good CSLO and SLP image quality.