New News Biology #37

The Eye (Part 2)

Accommodation = Reflex changing the refractive power of the lens

Close Object; the lens become short & fat, and refracts (bends) the light more strongly

There is a muscle around the lens called the ciliary muscle, which is responsible for controlling the lens’ shape. Connected to the ciliary muscles is the suspensory ligaments, which are what actually hold onto the lens. Normally, the ciliary muscles are contracted and the suspensory ligaments are stretched, in turn stretching the lens into a flat shape.

When the lens has to refract the light more, the ciliary muscle becomes relaxed, which makes the suspensory ligaments loosen, freeing the lens to return to its normal fat form.

Far Object; the lens doesn’t have to refract the light as much

In this case, the ciliary muscles contract, pulling the suspensory ligaments tighter, and making the lens flat.

Sight Problems; short-sighted and long-sighted both cause the same result, certain things become blurry.

Long-sighted; it basically means the lens can’t change its shape enough to refract the light onto that specific spot on the retina. The result is that close objects seem blurry. We can fix this by wearing convex lens, which provide extra refracting power, serving as a second lens.

Short-sighted; its the opposite of long-sighted. The far away objects become blurry, a result of the lens refracting too much light. A concave lens fixes this by counter-acting the extra refracting, balancing out the ‘refracting too much’ part.