Aphakia
Encyclopedia
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
, 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 that are normally excluded by the lens. This may have had an effect on the colors perceived by artist Claude Monet
, who had cataract
surgery in 1923.
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.
Causes:
1. Congenital- It is rare. It can be grouped as Primary (failure of development of lens in foetal life) and Secondary (Lens forms but gets absorbed in-utero due to some factors).
2. Surgical- following cataract surgery.
3. Trauma- common in children.
4. Posterior dislocation of lens in vitreous.
, contact lenses or by implant of an artificial lens
(pseudophakia).
Optical principle- correct the error by convex lens of appropriate power, so that the image is formed on retina.
Lens (anatomy)
The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a...
of the eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
, due to surgical removal, a perforating
Perforation
A perforation is a small hole in a thin material or web. There is usually more than one perforation in an organized fashion, where all of the holes are called a perforation...
wound or ulcer
Corneal ulcer
A corneal ulcer, or ulcerative keratitis, is an inflammatory condition of the cornea involving loss of its outer layer. It is very common in dogs and is sometimes seen in cats...
, or congenital anomaly. It causes a loss of accommodation
Accommodation (eye)
Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image on an object as its distance changes....
, hyperopia
Hyperopia
Hyperopia, also known as farsightedness, longsightedness or hypermetropia, is a defect of vision caused by an imperfection in the eye , causing difficulty focusing on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance...
, and a deep anterior chamber. Complications include detachment of the vitreous
Vitreous membrane
The vitreous membrane is a layer of collagen separating the vitreous humour from the rest of the eye. At least two parts have been identified anatomically. The posterior hyaloid membrane separates the rear of the vitreous from the retinaThe anterior hyaloid membrane separates the front of the...
or retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...
, and glaucoma
Glaucoma
Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...
.
Aphakic people are reported to be able to see ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
wavelengths that are normally excluded by the lens. This may have had an effect on the colors perceived by artist Claude Monet
Claude Monet
Claude Monet was a founder of French impressionist painting, and the most consistent and prolific practitioner of the movement's philosophy of expressing one's perceptions before nature, especially as applied to plein-air landscape painting. . Retrieved 6 January 2007...
, who had cataract
Cataract
A cataract is a clouding that develops in the crystalline lens of the eye or in its envelope, varying in degree from slight to complete opacity and obstructing the passage of light...
surgery in 1923.
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.
Optics of the Aphakic Eye
The eye becomes highly hypermetropic and total power of eye is reduced. This results in a total loss of accommodation.Causes:
1. Congenital- It is rare. It can be grouped as Primary (failure of development of lens in foetal life) and Secondary (Lens forms but gets absorbed in-utero due to some factors).
2. Surgical- following cataract surgery.
3. Trauma- common in children.
4. Posterior dislocation of lens in vitreous.
Treatment
Aphakia could be corrected by wearing glassesGlasses
Glasses, also known as eyeglasses , spectacles or simply specs , are frames bearing lenses worn in front of the eyes. They are normally used for vision correction or eye protection. Safety glasses are a kind of eye protection against flying debris or against visible and near visible light or...
, contact lenses or by implant of an artificial lens
Intraocular lens
An intraocular lens is an implanted lens in the eye, usually replacing the existing crystalline lens because it has been clouded over by a cataract, or as a form of refractive surgery to change the eye's optical power. It usually consists of a small plastic lens with plastic side struts, called...
(pseudophakia).
Optical principle- correct the error by convex lens of appropriate power, so that the image is formed on retina.