Aspheric Lenses :
1. Conventional or non aspheric lenses impart images which are not as sharp as they could be, which means the patient will have vision of an order person rather than that of a healthy younger person.
2. Aspheric lenses or aberration free lenses are surface modified to improve image quality, brightness & overall contrast. Because of its wavefront design they provide excellent night vision & low light vision e.g walking in a fog or dining by candlelight. It also enables faster reaction time when driving at night.
3. Aspheric lenses which are negatively aberrated also improve depth perception.
In a healthy human eye, cornea is round is shape like a basketball. In eyes with atigmatism (Cylindrical numbers) the cornea is asymmetrical & shaped more like an egg. When light passes through a cornea with astigmatism the images does not focus sharply on the retina causing blurred vision. Toric lenses are designed to correct the astigmatism lenses after surgery.