In middle age, the lens of the eye becomes less flexible and less able to thicken and thus less able to focus on nearby objects, a condition called presbyopia Causes 
. Reading glasses or bifocal lenses can help compensate for this problem. For more information on the effects of age on the eye, see Changes in the Body With Aging: Eyes Eyes The body changes with aging because changes occur in individual cells and in whole organs. These changes result in changes in function and in appearance. (See also Overview of Aging.) As cells... read more .
In old age, changes to the eye may include the following:
Yellowing or browning of the lens caused by many years of exposure to ultraviolet light, wind, and dust
Thinning of the conjunctiva
A bluish hue caused by increased transparency of the sclera
The number of mucous cells in the conjunctiva may decrease with age. Tear production may also decrease with age, so that fewer tears are available to keep the surface of the eye moist. Both of these changes explain why older people are more likely to have dry eyes Keratoconjunctivitis Sicca Keratoconjunctivitis sicca is dryness of the conjunctiva (the membrane that lines the eyelids and covers the white of the eye) and cornea (the clear layer in front of the iris and pupil). Too... read more 
. However, even though the eyes tend to be dry normally, tearing can be significant when the eyes are irritated, such as when an onion is cut or an object contacts the eye.
Arcus senilis (a deposit of calcium and cholesterol salts) appears as a gray-white ring at the edge of the cornea. It is common among people older than 60. Arcus senilis does not affect vision.
Some diseases of the retina are more likely to occur in old age, including macular degeneration Age-Related Macular Degeneration (AMD or ARMD) Age-related macular degeneration (AMD) causes progressive damage to the macula, the central and most vital area of the retina, resulting in gradual loss of central vision. Central vision becomes... read more 
, diabetic retinopathy Diabetic Retinopathy Diabetic retinopathy is damage to the retina (the transparent, light-sensitive structure at the back of the eye) as a result of diabetes. Blood vessels in the retina can leak blood and fluid... read more 
(if people have diabetes), and detachment of the retina Detachment of the Retina Detachment of the retina is separation of the retina (the transparent, light-sensitive structure at the back of the eye) from the underlying layer to which it is attached. People notice a sudden... read more . Other eye diseases, such as cataracts Cataract A cataract is a clouding (opacity) of the lens of the eye that causes a progressive, painless loss of vision. Vision may be blurred, contrast may be lost, and halos may be visible around lights... read more 
, also become common.
The muscles that squeeze the eyelids shut decrease in strength with age. This decrease in strength, combined with gravity and age-related looseness of the eyelids, sometimes causes the lower eyelid to turn outward from the eyeball. This condition is called ectropion Entropion and Ectropion Entropion is a condition in which the eyelid is turned inward (inverted), causing the eyelashes to rub against the eyeball. Ectropion is a condition in which the eyelid is turned outward (everted)... read more 
. Sometimes, because of age-related looseness affecting a different part of the eyelid, the lower eyelid turns inward, causing the eyelashes to rub against the eyeball. This condition is called entropion Entropion and Ectropion Entropion is a condition in which the eyelid is turned inward (inverted), causing the eyelashes to rub against the eyeball. Ectropion is a condition in which the eyelid is turned outward (everted)... read more . When the upper eyelid is affected, the lid can droop, a condition called ptosis.
In some older people, the fat around the orbit shrinks, causing the eyeball to sink backward into the orbit. This condition is called enophthalmos. Because of lax tissues in the eyelids, the orbital fat can also bulge forward into the eyelids, making them appear constantly puffy.
The muscles that work to regulate the size of the pupils weaken with age. The pupils become smaller, react more sluggishly to light, and dilate more slowly in the dark. Therefore, people older than 60 may find that objects appear dimmer, that they are dazzled initially when going outdoors (or when facing oncoming cars during night driving), and that they have difficulty going from a brightly lit environment to a darker one. These changes may be particularly bothersome when combined with the effects of a cataract.
Other changes in eye function also occur as people age. The sharpness of vision (acuity) is reduced despite use of the best glasses, especially in people who have a cataract Cataract , macular degeneration Age-Related Macular Degeneration (AMD or ARMD) Age-related macular degeneration (AMD) causes progressive damage to the macula, the central and most vital area of the retina, resulting in gradual loss of central vision. Central vision becomes... read more , or advanced glaucoma Glaucoma Glaucomas are a group of eye disorders characterized by progressive optic nerve damage (often, but not always, associated with increased eye pressure) that can lead to irreversible loss of vision... read more (see table Some Disorders That Affect Mainly Older People Some Disorders That Affect Mainly Older People 
). The amount of light that reaches the back of the retina is reduced, increasing the need for brighter illumination and for greater contrast between objects and the background. Older people may also see increased numbers of floating black spots (floaters Eye Flashes and Floaters Eye flashes are a person's perception of bright flashes of light, flickering lights, or streaks of light that do not correspond to external sources. Eye floaters are specks or strings that appear... read more ). Floaters usually do not significantly interfere with vision.
