Two perimetry strategies can identify early glaucomatous damage

SYDNEY, Australia — Two specialized perimetry tests can detect visual field loss before it appears on standard automated perimetry, a study here indicates.

John A. Landers, MB, BS, and colleagues investigated whether short wavelength automated perimetry (SWAP) and frequency doubling perimetry (FDP) could detect visual field abnormalities in patients that showed no abnormalities on achromatic automated perimetry (AAP). These tests target axons that are selectively damaged in glaucoma or have low redundancy.

Fifty patients with ocular hypertension and normal AAP readings who had characteristic glaucoma damage to the optic disc were evaluated using SWAP and FDP. Stereo fundus photographs were also taken, and these were analyzed by two glaucoma subspecialists not aware of the SWAP and FDP results. The specialists characterized the optic disc as normal or abnormal, and this was then compared to the SWAP and FDP findings.

SWAP showed a 33% sensitivity and a 92% specificity. The test had a positive predictive value of 57% and a negative predictive value of 81%.

FDP showed a 25% sensitivity and an 89% specificity. It had a positive predictive value of 49% and a negative predictive value of 79%.

The study suggests these tests can identify patients with early glaucomatous optic neuropathy not detected by AAP, the authors concluded.

The study is published in Clinical & Experimental Ophthalmology.