The lens is situated between the Iris and the vitreous body. It has a shape of a magnifying glass and it’s bulging from both the sides. It is made by several layers: the external membrane (capsula), the crust (cortex) and the core (nucleus).
The lens function
- Refraction – The lens has a refractive power of about 22 diopters, and together with the cornea, whose refractive power is about +43 diopters, makes the total refractive power of about 65 diopters.
- Accommodation – During the process of accommodation or adjustment to contractions of the muscle, the lens changes the curvature of the anterior and the posterior segment, and thus it becomes stronger by over 10 diopters, when young. Over the years the accommodation is getting lost so that about the age of 45 it decreases to less than 3 diopters and then, for reading we would need reading glasses.
- Protection – The lens absorbs the UV rays and thus it prevents them to penetrate further and damage the retina, especially its most sensitive part – the macula.