Normal age-related vision changes
http://www.mayoclinic.com/health/vision-problems/HA00061&slide=1
As you age, so do your eyes. Common changes in your vision as you age include:
- Reduced sensitivity to light. You might notice that you need brighter lighting near your favorite reading chair or at your workstation.
- Decreased visual acuity. Colors appear dim, and glare forms when light shines directly at you. This might cause you to avoid night driving.
- Difficulty reading small print. The lens in your eye becomes less elastic and loses its ability to focus — a condition called pre*****yopia. You might need reading glasses or a magnifying glass to read small print.
Besides these changes to your eyes, aging makes you more prone to developing eye diseases that could impair your vision.
1. Cataracts (白内障)
Your eye's lens — a clear, M&M-sized oval — sits behind the iris and pupil. If the lens becomes cloudy or if the lens develops opaque areas that block light from passing through (opacities), you have a condition called a cataract. Cataracts are usually associated with blurred vision.
About half of Americans age 80 and older have cataracts or have had cataract surgery. In early cataracts, you may not notice blurred vision because the opacities are small and the cloudiness is minimal. But as the opacities and the cloudiness become denser, the cataracts can interfere with your vision.
Vision with cataracts:
If you have cataracts, you may notice your vision becoming clouded, blurred or dim. You might find it harder to see at night. Some other signs and symptoms include:
- Sensitivity to light and glare
- Halos around lights
- Fading or yellowing of colors
- Double vision or multiple vision in one eye
Surgery is a common solution for cataracts. Most cataracts can only be detected with special instruments, so make an appointment with your eye doctor if you notice your vision clouding.
2. Glaucoma (青光眼)
Glaucoma is a group of diseases that are usually associated with an elevated fluid pressure inside your eyeball. This pressure can damage your optic nerve — the millions of nerve fibers that carry visual information from your eye to your brain. As your optic nerve deteriorates, blind spots develop in your visual field. This can lead to blindness in both eyes.
If detected early, glaucoma is treatable with medication or surgery.
Vision with glaucoma:
You might not notice glaucoma until it reaches an advanced stage. But some signs and symptoms you might notice before then include:
- Sensitivity to light and glare
- Trouble differentiating between varying shades of light and dark
- Trouble with night vision and halos around lights
- Loss of side vision
- Eye pain or discomfort, with certain types of glaucoma
Seek immediate medical attention if you have severe eye pain, a headache, and nausea and vomiting associated with changes in your vision.
3. Macular degeneration (视网膜黄斑变性退化疾病)
Age-related macular degeneration (AMD) occurs when tissue in your macula — the part of your retina that's responsible for the center of your visual field — deteriorates. A blind spot forms in the center of your vision as a result.
AMD is one of the most frequent causes of vision loss in people age 60 and older. Though it usually can't be reversed, if AMD is caught early, you might be able to reduce the extent of your vision loss.
Vision with macular degeneration:
AMD leads to a blind spot in the center of your visual field. Other signs and symptoms include:
- The need for increasingly bright light when reading or doing close work
- Printed words that appear distorted or increasingly blurred
- Colors that seem washed out and dull
- A gradual haziness of your overall vision
- Difficulty seeing when moving from a bright room to a dimly lit room
If AMD develops in one eye and not the other, it may not be as noticeable, as your good eye compensates for the weak one. It's when AMD develops in both eyes that your vision is dramatically affected.
4. Floaters (飞蚊症)
As you age, your vitreous can become more liquid than jelly-like, causing floaters, which appear as spots and specks floating across your field of vision (see arrows). They're actually small clumps of gel, fibers and cells floating in the vitreous.
Most floaters are harmless, but if you suddenly develop a large number, especially if accompanied by flashes of light, it might signal a retinal tear or retinal detachment. Floaters are also a symptom of eye melanoma, a cancer of the eye. In such cases, seek medical attention immediately.
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来源: xiaoxiaowen 于 09-04-05 17:08:13
