The principle advantage of cataract glasses is their convenience - they are easy to handle and quick to put on.
However, this is often outweighed by the many disadvantages:
- image magnification - cataract glasses magnify objects by about 30% which may take months to become accustomed to. They are unsuited for unilateral cataract extraction since the magnification makes it impossible for the brain to fuse the image of the aphakic eye with that of the other - diplopia ensues.
- image distortions - the thickness of the glasses causes straight lines to appear bowed outwards. The patient must learn to look through the centre of glasses where vision is most effective and to turn their head when looking to the side.
- image jumping - there is an annular area of blindness from which images jump in and out. The patient is liable to collision and is one of the reasons why the wearing of contact glasses results in disqualification from driving heavy goods or public service vehicles.
- the lenses are heavy, tend to slip, and may need constant adjustment by an optician.
Since accommodation is lost, bi- or tri- focals are usually prescribed.