Contrast
Sensitivity is the measure of quality or crispness of vision. In
general terms, contract sensitivity is our ability to detect subtle
differences between objects that are white and black. The ability of
human eye to detect contrast is best when there is very bright lighting
and it decreases as the light becomes dimmer. It is a fact that
refractive surgery causes a temporary mild decrease in contrast
sensitivity immediately after surgery.
Decrease in contract
sensitivity is triggered by the normal swelling and healing of the
cornea. It tends to resolve notably within the first few weeks post
surgery and recovers to near-normal within the first few months. A
number of factors contribute to this like the treatment using older
broad beam lasers, treating an area of the cornea that is too small as
compared to the size of the pupil under dim light and the presence of
significant higher order optical aberrations, which are very subtle
imperfections in the visual system. The traditional IOLs were spherical
i.e. front surface is curved. But the newly introduced Aspheric IOLs
are slightly flatter in the periphery and are designed to provide
better contrast sensitivity eg. The Acrysof SN60WF.
The
contrast sensitivity is better in younger generation as compared to the
older generation. This is mainly due to the loss of the ganglion cells
of retina which we lose as we age. As a result of this, the contrast
sensitivity also gets decreased. But comparing the blurred vision
endured by the cataract patients before the surgery, this improved
contrast sensitivity is a blessing. Younger generation patients are the
one to enjoy better contrast sensitivity as they are more likely to
have healthier ganglion cells.
Roshan Eye Care Hospital uses a spherical Acrysof IOLs whenever the patient can be motivated for the best.