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Refraction
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Refraction In order for an eye to see clearly, the light rays must come to a perfect focus when they reach the fovea. The bending of the light rays is called refraction. Each eye has its own characteristic refractive error. An instrument (retinoscope) is used to determine this error. The examination is called refracting the eye. From the refraction, the examiner learns the strength of lens necessary to provide the clearest vision for each eye.
RELATED TERMS--------------------------------------
Fovea
A central portion of the retina and macula that contains only cones. The fovea is the only part of the eye that is capable of 20/20 or better vision.
Refraction
In order for an eye to see clearly, the light rays must come to a perfect focus when they reach the fovea. The bending of the light rays is called refraction. Each eye has its own characteristic refractive error. An instrument (retinoscope) is used to determine this error. The examination is called refracting the eye. From the refraction, the examiner learns the strength of lens necessary to provide the clearest vision for each eye.
Eye
The organ of sight. The eye has a number of components. These components include but are not limited to the cornea, iris, pupil, lens, retina, macula, optic nerve, choroid and vitreous.
Lens
The lens of the eye is like an adjustable lens of a camera and focuses light rays on to the retina for sharp images. A condition called presbyopia occurs when the lens is no longer able to adjust for objects at different distances.
Vision
The sense of sight.
SIMILAR TERMS--------------------------------------
PREVIOUS AND NEXT TERMS--------------------------------------
Reflex sympathetic dystrophy
See 'algodystrophy'.
Reiter's syndrome
Triad of arthritis, conjunctivitis and urethritis. A form of reactive arthritis. Other features of seronegative spondylarthropathy may be present.
Relapsing polychondritis
A rare autoimmune disorder in which there is inflammation of hyaline cartilage in joints, nose, pinna and airways. Scleritis may occur.
Rice bodies
Aggregates of cells, fibrin and debris found in synovial fluid from chronically inflamed joints.
Ritchie index
A scoring system for recording joint tenderness.
Refraction
Retinal detachment
A retinal detachment occurs when the retina, that part of the eye that contains the photoreceptors, detaches from the underlying layers of cells, called the choroid. A retinal detachment my be the result of injury to the eye such as blunt trauma (remember Sugar Ray, the boxer) or it may result from other things like high myopia or age-related macular degeneration. In certain diseases, retinal breaks and tears occur and these may lead to a retinal detachment. Early warning signs include bright dots or lights or some of your side vision may appear dark. A retinal detachment may be treatable if detected early, so see your Ophthalmologist.
Retinoblastoma
The most common cancer in the eye occurring in early childhood. A parent or doctor may first suspect a problem by detecting whiteness in the normally dark pupil. Occasionally it leads to a wandering eye (strabismus). It does not spread from one eye to the other but about 25% have a tumor in each eye. Immediate medical treatment is necessary. Sometimes the eye(s) must be removed to prevent spreading of the tumor into the brain.
Retrobulbar neuritis
An inflammation of the optic nerve. It causes a loss in vision. It is sometimes indicative of a neurological disease.
Rod cone dystrophy
A number of retina diseases in which the rod photoreceptors first start to degenerate followed by the cone photoreceptors. Other parts of the retina and RPE are also adversely affected. Symptoms include loss of side vision and night blindness followed by the loss of central vision. RP is the most common form of rod-cone degeneration. Some forms occur at birth while other forms may start much later in life. Generally very poor prognosis.
Rods
The rods are the visual cells of the retina that are important for night vision and peripheral vision. The rods are the first affected in rod-cone degenerations such as RP.
RELATED TERMS--------------------------------------
Fovea
A central portion of the retina and macula that contains only cones. The fovea is the only part of the eye that is capable of 20/20 or better vision.
Refraction
In order for an eye to see clearly, the light rays must come to a perfect focus when they reach the fovea. The bending of the light rays is called refraction. Each eye has its own characteristic refractive error. An instrument (retinoscope) is used to determine this error. The examination is called refracting the eye. From the refraction, the examiner learns the strength of lens necessary to provide the clearest vision for each eye.
Eye
The organ of sight. The eye has a number of components. These components include but are not limited to the cornea, iris, pupil, lens, retina, macula, optic nerve, choroid and vitreous.
Lens
The lens of the eye is like an adjustable lens of a camera and focuses light rays on to the retina for sharp images. A condition called presbyopia occurs when the lens is no longer able to adjust for objects at different distances.
Vision
The sense of sight.
SIMILAR TERMS--------------------------------------
PREVIOUS AND NEXT TERMS--------------------------------------
Reflex sympathetic dystrophy
See 'algodystrophy'.
Reiter's syndrome
Triad of arthritis, conjunctivitis and urethritis. A form of reactive arthritis. Other features of seronegative spondylarthropathy may be present.
Relapsing polychondritis
A rare autoimmune disorder in which there is inflammation of hyaline cartilage in joints, nose, pinna and airways. Scleritis may occur.
Rice bodies
Aggregates of cells, fibrin and debris found in synovial fluid from chronically inflamed joints.
Ritchie index
A scoring system for recording joint tenderness.
Refraction
Retinal detachment
A retinal detachment occurs when the retina, that part of the eye that contains the photoreceptors, detaches from the underlying layers of cells, called the choroid. A retinal detachment my be the result of injury to the eye such as blunt trauma (remember Sugar Ray, the boxer) or it may result from other things like high myopia or age-related macular degeneration. In certain diseases, retinal breaks and tears occur and these may lead to a retinal detachment. Early warning signs include bright dots or lights or some of your side vision may appear dark. A retinal detachment may be treatable if detected early, so see your Ophthalmologist.
Retinoblastoma
The most common cancer in the eye occurring in early childhood. A parent or doctor may first suspect a problem by detecting whiteness in the normally dark pupil. Occasionally it leads to a wandering eye (strabismus). It does not spread from one eye to the other but about 25% have a tumor in each eye. Immediate medical treatment is necessary. Sometimes the eye(s) must be removed to prevent spreading of the tumor into the brain.
Retrobulbar neuritis
An inflammation of the optic nerve. It causes a loss in vision. It is sometimes indicative of a neurological disease.
Rod cone dystrophy
A number of retina diseases in which the rod photoreceptors first start to degenerate followed by the cone photoreceptors. Other parts of the retina and RPE are also adversely affected. Symptoms include loss of side vision and night blindness followed by the loss of central vision. RP is the most common form of rod-cone degeneration. Some forms occur at birth while other forms may start much later in life. Generally very poor prognosis.
Rods
The rods are the visual cells of the retina that are important for night vision and peripheral vision. The rods are the first affected in rod-cone degenerations such as RP.
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This dictionary contains 19186 terms.
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