The Human Lens
The Human Lens
The human lens changes throughout your life. The changes in the lens as you age can be divided into 5 stages:
Stage 1: The Youthful Lens
The youthful lens provides clear and focused vision, vivid color, high contrast without glare, and the ability refocus from distance to near. With the youthful lens, your eye behaves like a high quality autofocus camera.
Stage 2: Loss of Accommodation (Presbyopia)
The lens is clear, but the ability to focus at distance and then refocus at near is slowly lost. This is presbyopia. Presbyopia is a progressive event that usually becomes apparent in your 30's or 40's. You may start to notice this when reading details on a map or prescription bottle. If you experience eye strain or headaches when reading, this may be due to presbyopia.
Stage 3: The 'Clear' Cataract
The lens is still clear, however the lens material no longer bends light consistently. The image that is generated is a little blurry even though the lens material is clear. This type of blur cannot be corrected with glasses or contacts. Contrast goes down, and glare becomes noticeable. You may find yourself changing glasses more often, even several times in a year, as the lens changes. You may become more nearsighted.
Stage 4: The Moderate Cataract
When opacities are actually visible to your Ophthalmologist, you are at Stage 4. There are many different types of Stage 4 cataract. The lens may be yellow (nuclear cataract). There may be white spokes radiating from the sides (cortical cataract). Spots can collect on the posterior surface of the lens (posterior subcapsular cataract). All cataracts cause blur, glare, and loss of contrast. Color shifts to a brown-yellow tint, although you may not realize that this has happened until cataract surgery brings natural color and brilliance back. Most cataracts are at this stage when surgery is performed.
Stage 5: The Advanced Cataract
The stage 5 cataract can become white. Vision is profoundly reduced. Cataracts rarely progress to this stage in the United States.