What is APHAKIA

APHAKIA

Aphakia literally means absence of crystalline lens from the eye. However, from the optical point of view, it may be considered a condition in which the lens is absent from the pupillary area. Aphakia produces a high degree of hypermetropia.

Causes
1. Congenital absence of lens. It is a rare condition.
2. Surgical aphakia occurring after removal of lens is the commonest presentation.
3. Aphakia due to absorption of lens matter is noticed rarely after trauma in children.
4. Traumatic extrusion of lens from the
eye also constitutes a rare cause of aphakia.
5. Posterior dislocation of lens in vitreous causes optical aphakia.

Optics of aphakic eye Following optical changes occur after removal of crystalline lens:
1. Eye becomes highly hypermetropic.
2. Total power of eye is reduced to about +44 D from +60 D.
3. The anterior focal point becomes 23.2 mm in front of the cornea.
4. The posterior focal point is about 31 mm behind the cornea i.e., about 7 mm behind the eyeball. (The antero-posterior length of eyeball is about 24 mm)
5. There occurs total loss of accommodation.

Clinical features
Symptoms.
1. Defective vision. Main symptom in aphakia is marked defective vision for both far and near due to high hypermetropia and absence of accommodation.
2. Erythropsia and cynopsia i.e., seeing red and blue images. This occurs due to excessive entry of ultraviolet and infrared rays in the absence of crystalline lens.

Signs of aphakia include:
1. Limbal scar may be seen in surgical aphakia.
2. Anterior chamber is deeper than normal.
3. Iridodonesis i.e., tremulousness of iris can be demonstrated.
4. Pupil is jet black in colour.
5. Purkinje's image test shows only two images (normally four images are seen-).
6. Fundus examination shows hypermetropic small disc.
7. Retinoscopy reveals high hypermetropia.