Lens diseases

From Cat
Section of feline eye showing shape, position and size. (Courtesy of Barnett & Crispin, 2002)

Disorders of the lens constitutes a relatively small component of general eye diseases.

The lens is a biconvex, transparent and refractive structure suspended by zonular fibres, situated behind the iris (which it supports) and posterior chamber, and arbitrarily dividing the anterior and posterior segments of the eye[1].

The feline lens consists of a capsule, lens epithelium lying beneath the capsule of the anterior face and at the equator, and lens fibres which form throughout life; the lens fibres are partially responsible for the normal ageing change of senile nuclear sclerosis. Sclerosis of the lens occurs in the older cat, as in all animals, but is not as obvious as in the dog. The lens is subdivided into a nucleus (embryonic, foetal and adult), cortex and capsule and these can be further subdivided clinically into anterior and posterior portions.

The lens is relatively large compared to the dog and accommodation is poor.

Disorders of the lens can be classified into congenital anomalies, cataract (simply defined as an opacity of the lens and/or its capsule)and luxation/subluxation (abnormal position due to partial or complete rupture of the zonular fibres).

References

  1. Barnett, KC & Crispin, SM (2002) Feline Ophthalmology: An atlas & text. Saunders, USA