Glare is an issue that is often discussed before cataract surgery as it relates to the choice of IOL. When IOLs were first introduced, only the degree and the safety of implantation were considered, so the visual effect was not well understood. As research progressed, it was understood that the reason for glare after cataract surgery was the spherical aberration effect of IOLs, which means that the same parallel light rays, when passing through a spherical lens, could not completely focus the light on the retina, and the part of the light that could not be focused on the net mo was the cause of glare.
Therefore, aspheric crystals were created. Under normal circumstances spherical crystals have a visual effect comparable to aspheric crystals due to their small pupils when there is sufficient light, but in relatively low light conditions, spherical crystals will have reduced visual acuity, especially when seeing light sources that produce glare. In contrast, the visual effect of aspheric lens is not affected by the pupil size, and it can achieve better vision in both bright and dark places, especially for patients with abnormal pupils, such as glaucoma patients with forced dilated pupils and patients with traumatic pupil damage.