Crystalline Lens

Question 1

Equator

Answer 1

Tip of Lens

Question 2

Equator is _________

Answer 2

Stationary

Question 3

Movement occurs mainly in…

Answer 3

Centre of lens

Question 4

Lens has Zonule fibres that attach…..

Answer 4

to the Equator and the Ciliary body i.e. Ciliary processes and the Ciliary muscle.

Question 5

Between 20-60yrs of Age, there is an average increase in lens thickness of….

Answer 5

1mm in Cortex

Question 6

There is also a gradual decrease in Anterior Radius of the lens with Age –

Answer 6

On average - 5mm between 20-60yrs.

Question 7

What other changes are there?

Answer 7

Compensatory changes in refractive index gradient of the lens.

The elasticity of the lens capsule also diminished with Age.

Question 8

Reduction in Crystalline lens Power with age is one of the mechanisms to counteract the effects of Axial Length growth.

Answer 8

This is a reduction of about 25D in the first 12 yrs. of life.

Question 9

Brunescence

Answer 9

As we age, the lens selectively absorbs more blue light (410nm) because of accumulation of yellow pigment in the lens.

This decrease in transmission of blue light is part of the Cataractogenic process (formation of cataracts) and causes a relative “blue-blindness.”

Colours are perceived differently because the lens tends to yellow with age.

Question 10

What effect does Cataract have on a patient?

Answer 10

Seeing in dim light becomes more difficult because the lens tends to become less transparent. A denser lens means that less light passes through to the retina at the back of the eye. Also, the retina which contains the photoreceptors become less sensitive. So for reading brighter light is needed.

Question 11

Fact about how older patients require more light.

Answer 11

On average 60yrs old need 3x more light to read than 20yrs old.