Search results
Results from the WOW.Com Content Network
The primary causes include post-cataract surgery, certain medications, and, less commonly, neurological or ophthalmological conditions. Post-cataract surgery is a common cause, as replacing the natural lens with a synthetic one increases exposure to blue light, leading to temporary blue-tinted vision. This effect usually resolves as the eye adapts.
A retinal tear may also allow fluid to leak behind the retina, causing it to detach. This will often leak blood into the vitreous, which is seen by the patient as a sudden appearance of numerous small black dots or ribbons moving across the field of vision. Sometimes a gray curtain may appear to partially block vision in one eye.
Posterior capsular opacification, also known as after-cataract, is a condition in which months or years after successful cataract surgery, vision deteriorates or problems with glare and light scattering recur, usually due to thickening of the back or posterior capsule surrounding the implanted lens, so-called 'posterior lens capsule opacification'.
Manual small incision cataract surgery (MSICS) is an evolution of extracapsular cataract extraction (ECCE); the lens is removed from the eye through a self-sealing scleral tunnel wound. A well-constructed scleral tunnel is held closed by internal pressure, is watertight, and does not require suturing.
Visual outcome after cataract surgery was close to conformity with WHO guidelines in Buenos Aires, where more than 80% of post-surgery eyes had visual acuity of 6/18 (20/60) or better, but ranged between 60% and 79% in most of the other regions, and was less than 60% in Guatemala and Peru.
Cataract surgery in small animals such as dogs and cats is a routine ophthalmic procedure with a success rate of around 90%, and is usually better for eyes with relatively recent cataract development. The presence of other ocular problems may reduce the success rate. Procedures are similar to those for humans.
A scotoma may include and enlarge the normal blind spot. Even a small scotoma that happens to affect central or macular vision will produce a severe visual disability, whereas a large scotoma in the more peripheral part of a visual field may go unnoticed by the bearer because of the normal reduced optical resolution in the peripheral visual field.
Most vision researchers believe that phosphenes result from the normal activity of the visual system after stimulation of one of its parts from some stimulus other than light. For example, Grüsser et al. showed that pressure on the eye results in activation of retinal ganglion cells in a similar way to activation by light. [ 23 ]