Polarimetric nerve fiber analysis in patients with visible optic nerve head drusen

Objective: To evaluate the effect of visible optic nerve head drusen (ONHD) on retinal nerve fiber layer (RNFL) thickness retardation by using scanning laser polarimetry. Methods: Twenty-three eyes of 13 patients with visible ONHD and 26 eyes of 13 age- and sex-matched control subjects were involved in the study. Ophthalmologic examination, scanning laser polarimetry with nerve fiber analyser (NFA) type II GDX, automated Humphrey visual field testing, and red-free fundus photography were performed. Eyes with ONHD were classified from grade 0 to III according to the amount of visible drusen. Thus, grade 0 discs had no clinically visible ONHD and grade III discs represented the presence of dense drusen. Results: Measurements with NFA of RNFL thickness retardation showed significant decrease in eyes with visible ONHD compared with control eyes (P < 0.05). Although no significant difference was found between grade I and grade II discs regarding NFA measurements, grade III discs had significantly lower values, indicating the greater amount of RNFL loss with higher grade ONHD. Documentation of increased percentage of visual field defects with higher grade drusen was also in accordance with this finding. Conclusions: NFA can quantitatively detect the decrease in retardation of RNFL thickness in eyes with visible ONHD and can be used as an indicator of nerve fiber layer loss in these cases.