Abstract
Purpose::
In patients with early signs of AMD small functional changes of foveal and parafoveal sensitivity are well known. To evaluate the impact of these changes on reading, we examined the eye movements during the reading of short sentences in a group of patients with early signs of AMD and an age-matched control group.
Methods::
Short paragraphs of text were presented by the visible laser beam of a scanning-laser ophthalmoscope (SLO) to 14 patients with early signs of AMD (visual acuity 0.6 or better, no other fundus changes than drusen and/or pigmentary changes) and 14 age-matched controls. Texts were presented with no (corresponding to 1M at 25cm) or slight (1,25-fold, 1,6-fold) magnification. Patients were tested with the text size corresponding to their individual magnification need. The movements of the fundus structures relative to the stimulus were extracted from the video sequences of the SLO-examination with the help of specialized image processing software. The reading speed was measured and the number of forward saccades and backward saccades per word was counted and evaluated. Data of the better eye of 14 patients with early signs of AMD and 14 age-matched controls was compared.
Results::
Mean rate (±standard deviation) of forward and backward saccades per word did not differ significantly for 1M text size between early AMD patients and controls.For 1,25 M text size we found a significant difference for the rate of backward saccades: 0,36 (±0,12) vs. 0,17 (±0,11) backward saccades per word (p=0,03).For 1,6 M text size we found a significant differences for the rate of saccades: 1,34 (±0,29) vs. 1,04 (±0,23) forward saccades per word (p=0,04); 0,43 (±0,25) vs. 0,17 (±0,11) backward saccades per word (p=0,04).We found no significant difference in the saccade rate of the control group reading the three different text sizes.
Conclusions::
We found differences in the rate of forward and backward saccades per word even in a group of patients with early signs of AMD.The quantification of reading eye movements could be a sensitive tool to assess subtle functional changes in early AMD.
Keywords: low vision • age-related macular degeneration • reading