|Classification and external resources|
Aphakia is the absence of the lens of the eye, due to surgical removal, a perforating wound or ulcer, or congenital anomaly. It causes a loss of accommodation, far sightedness (hyperopia), and a deep anterior chamber. Complications include detachment of the vitreous or retina, and glaucoma.
Aphakic people are reported to be able to see ultraviolet wavelengths (400–300 nm) that are normally excluded by the lens. They perceive this light as whitish blue or whitish violet. This is probably because all three of the eye's color receptors, the blue more than the others, are stimulated when such a person sees ultraviolet wavelengths. Some animals have a fourth color receptor for ultraviolet wavelengths (see tetrachromacy) and see the near ultraviolet as an extra primary color.
Babies are rarely born with aphakia. Occurrence most often results from surgery to remove congenital cataracts (clouding of the eyes' lens, which can block light from entering the eye and focusing clearly). Congenital cataracts usually develop as a result of infection of the fetus or genetic reasons. It is often difficult to identify the exact cause of these cataracts, especially if only one eye is affected.
People with aphakia have relatively small pupils and their pupils dilate to a lesser degree.
Symptoms and treatment
Without the focusing power of the lens, the eye becomes very farsighted. This can be corrected by wearing glasses, contact lenses, or by implant of an artificial lens. Artificial lenses are described as "pseudophakic." Also, since the lens is responsible for adjusting the focus of vision to different lengths, patients with aphakia have a total loss of accommodation.
- Komarnitsky. "Case study of ultraviolet vision after IOL removal for Cataract Surgery".
- David Hambling (May 30, 2002). "Let the light shine in: You don't have to come from another planet to see ultraviolet light". EducationGuardian.co.uk.
- Mary V Gibbens, R Goel, S E Smith (1989). "Effect of cataract extraction on the pupil response to mydriatics" (PDF). British Journal of Ophthalmology 73: 563–565.
- Columbia University's Digital Reference of Ophthalmology
- Aphakia, Cincinnati Children's Hospital Medical Center Ophthalmology Division
- The human is a blocked tetrachromat A review of the spectral sensitivity of the human visual system. (Suggests that the human lens is responsible for blocking the ultraviolet frequencies, that we already have a UV sensor in the retina ready and waiting, and if the UV wasn't blocked, we'd all be tetrachromats.)