Cataract

Any congenital or acquired opacity in the lens capsule or substance, irrespective of the effect on vision, is a cataract. Cataract is the commonest cause of treatable blindness in the world.


Lens: The lens is biconvex and transparent. It is held in place behind the iris by the suspensory ligament whose zonular fibers are composed of protein fibrillin which attach its equator to the ciliary body. Disease may affect structure, shape and position.

Normal lens: 4-5mm thick and approx. 10 mm in diameter.
Outer: cortex.
Inner: Nucleus


Classification:
I. According to Age
- Congenital
- Infantile
- Juvenile
- Pre-senile
- Senile

II. According to Morphology
- Capsular
- Sub-capsular
- Cortical
- Nuclear

III. According to Etiology
- Age related: example senile cataract
- Traumatic cataract
- Metabolic cataract: due to diabetes mellitus, hypoparathyroidism
- Toxic cataract: due to use of steroids, and other medications
- Complicated cataract: secondary to some other eye disease such as chronic anterior uveitis, acute angle closure glaucoma, pathological myopia

IV. According to Maturity
- Immature cataract
- Mature cataract
- Hypermature cataract: Proteins are liquefied and the permeability of the capsule is increased. This results in leakage of proteins and deposition of calcium.

Example: MORGAGNIAN CATARACT (Cortex liquefies and the nucleus sinks down)

Intumescent cataract: Lens is swollen due to water retention. Maybe immature, mature or hypermature.


Symptoms:
1. Blurred vision (most important symptom)
2. Glare
3. Monocular diplopia
4. Haloes around light
5. Improvement in near vision


Signs:
Depend on the state of maturity of the cataract
1. Decreased visual acuity
2. Change in the colour of the pupil
3. Iris shadow
4. Abnormal red reflex


Management:
(There is no medical treatment for cataract!)
1. Surgery (Goal of cataract surgery: to leave the patient emmetropic)
2. Glasses


Indications for Cataract Surgery:
1. Visual improvement
2. Medical indication eg. The patient develops glaucoma or diabetic retinopathy,r etinal detachment
3. Cosmetic indication


Pre-operative Assessment:
1. Complete ocular exam
2. Macular function test
3. Optic nerve function test
4. Biometry
5. Investigations:
- CP & ESR (complete blood picture and erythrocyte sedimentation rate)
- FBS (fasting blood sugar)
- UDR (urine detailed report)
- Hep B and C virology


Anaesthesia:
1. Facial Block
2. Retrobulbar block


Surgical Techniques:
1. ECCE (Extra Capsular Cataract Extraction)
2. ICCE (Intra Capsular Cataract Extraction)- not used anymore
3. Phacoemulsification – the newest method


Disadvantages of ICCE (Intra Capsular Cataract Extraction):
1. Large incision
2. Posterior capsule is removed and so the vitreous gel may come out
3. Posterior capsule is removed and therefore, there is no support for the IOL (intraocular lens)


Advantages of Phacoemulsiication:
1. Small tunnel incision
2. Quick recovery
3. Early visual rehabilitation
4. Useful for the removal of soft cataract (nucleus is soft)


Complications of Cataract Surgery:
1. Operative complications
- Rupture of posterior capsule
- Vitreous loss
2. Post-op complications
- Iris prolapse
- Corneal edema
- Uveitis
- Endopthalmitis
- Post-op Astigmatism
- Cystoid macular edema
- Retinal detachment
- Posterior capsule opacification

Congenital Cataract
- Opthalmological emergency!!!!
- Bilateral congenital cataract results in a significant effect on visual acuity and results in nystagmus and amblyopia.
Nystagmus: involuntary rapid movement (horizontal, vertical, rotatory or mixed i.e. of two types) of the eyeball.
Amblyopia: dimness of vision without detectable organic lesion of eye.