Scanning laser polarimetry versus frequency-doubling perimetry and conventional threshold perimetry: Changes during a 12-month followup in preperimetric glaucoma. A pilot study

Purpose: To evaluate the possibility for detecting the progression in prepe rimetric primary open angle glaucoma (POAG) using scanning laser polarimetr y (SLP), frequency-doubling technology (FDT), and conventional automated pe rimetry (AP). Patients and methods: 22 eyes of 11 preperimetric POAG patients were evalua ted using SLP (Nerve Fiber Analyzer, GDx), AP (Humphrey 24-2 threshold test ) and FDT (30 degrees threshold test). All eyes had intraocular pressure (I OP) higher than 21 mmHg before treatment, but were consistently lower than 22 mm Hg with unchanged topical medication before and during the study. At the initial evaluation session optic nerve heads showed mild glaucomatous c hanges but the visual fields were normal (MD better than 2.0 dB, Glaucoma H emifield Test: within normal limits or borderline). AP and FDT measurements were repeated 6 months later, and all three tests were repeated 12 months after the first investigation. Results: IOP, AP and FDT measurements showed no statistically significant c hanges during the 12-month follow up period. In contrast to this, a tendenc y for a glaucomatous type decrease was seen with SLP in the retinal nerve f ibre layer (RNFL) thickness parameters (mean superior and inferior sector t hickness values, ellipse average thickness and maximal modulation). The mea n decrease of RNFL thickness in the superior and inferior sectors was 2.77 mum and 2.48 mum, respectively. Using the two-way nested ANOVA, which consi ders the relation between the right and left eyes of the subjects, the decr ease was statistically significant (p=0.021) for the inferior sector RNFL t hickness. Conclusion: The results suggest that scanning laser polarimetry is a useful technique to detect and measure glaucomatous progression in early glaucoma . Scanning laser polarimetry of the RNFL may help to detect and quantify ea rly progression even if worsening is not seen with perimetry and FDT tests.