Abstract
Purpose::
To investigate visual function including reading performance and contrast sensitivity, and also ocular higher order aberration in subjects with cortical cataract without opacity in the central pupil area.
Methods::
Among the 150 subjects aged >55 yrs of a population based study (Monzen Eye Study, 2005), 20 normal subjects (NS), (mean age 65.0 ± 5.7 yrs) and 24 with cortical cataract and no opacification in a 3mm diameter area about the centre of the pupil (CS) (mean 66.0 ± 6.9 yrs) were selected. Each subject underwent an MNREAD-J test (Minnesota Laboratory & TWCU Oda-lab for Low Vision Research) for reading acuity, critical print size, and maximum reading speed; and ophthalmic evaluations employing particular tools including contrast sensitivity (CAT-2000 NEITZ), backward light scattering intensity (BLSI) of the crystalline lens (EAS-1000,NIDEK), and ocular higher order aberration (KR-9000PW, Topcon, Tokyo, Japan) Higher order aberration was divided into the 5 types Trefoil, Coma, Tetra-foil, 2nd-Astigmatisum and Spherical according to a Zernike Vector Map (installed in a KR-9000PW).
Results::
No significant differences were observed between NS and CS in contrast sensitivity or BSLI around the lens axis. Reading acuity and maximum reading speed of CS (mean: 0.167logMAR; 282cpm) were significantly worse than those of NS (mean 0.053logMAR; 323cpm), P<0.05. The maximum reading speed of CS decreased with increase of opacification in the pupil area (r = 0.457, P<0.05). In the fourth higher order aberrations, ocular aberration, with exception of spherical aberration, was significantly higher in CS than in NS (P<0.05). There was a positive correlation between Tetra-foil aberration and the area of cortical opacification in a 6mm diameter area around the center of the pupil (r = 0.442, P<0.05).
Conclusions::
In cortical cataract cases without opacification in the central pupil area, no obvious deterioration of contrast sensitivity was seen. However, the reading performance of these cases was weak. Forward light scattering of the cortical opacification and increasing of the higher order aberration may play important roles in this deterioration of quality of vision.
Keywords: cataract • aging: visual performance • optical properties