Cataract

Cataract

Cataract is clouding or opacity of crystalline lense of eye.

Varying in degree from slight to complete opacity and obstructing passage of light.

Classification of Cataract

1. Etiological classification

2. Morphological classification

1. Etiological classification

Includes;

1. Congenital cataract

Malnutrition

Infectious disease during 1st trimester of pregnancy (mumps, measles, rubella)

Radiation and drug

2. Acquired cataract 

1. Senile cataract 

Age related cataract

Denaturation of lens protein and opecification of cortical lens fibers.

2. Traumatic cataract

Due to penetrating or non penetrating injury, blunt injury to eye, laceration (tearing soft tissue), foreign bodies in eye.

3. Complicated cataract (Secondary cataract)

Opacity of lens and other intraocular disease.

4. Metabolic cataract

Due to endocrine disorders and biochemical abnormalities.

5. Radiation cataract

Exposure of radiation causing damage of lens epithelium.

6. Electric cataract

After passage of powerful electric current through body.

7. Dermatogenic cataract

Associated with skin disease (atopic dermatitis).

8. Toxic cataract

Tetracycline, thiazides, tranquilizer, corticosteroids, oral contraceptives.

2. Morphological classification

1. Capsular cataract

May anterior capsule or posterior capsule.

2. Sub capsular cataract

Superficial part of cortex (just below capsule). Include anterior sub capsule or posterior sub capsule.

3. Cortical cataract

Lens fibers of cortex mainly affected.

Hydration due to accumulation of water droplet in between fiber and protein first denaturation then coagulated forming opacity.

4. Supranuclear cataract

Involve only deeper part of cortex (just outside nucleus).

5. Nuclear cataract

Nucleus of crystalline lens become cloudy and obstruct light rays.

6. Polar cataract 

Involve capsule and superior part of cortex in polar region only, may be anterior polar cataract and posterior polar cataract.

Cataract Progress (Clinical Stages Development)

1. Immature cataract

Lens of eye not completely opaque.

2. Mature cataract

Lens completely opaque and vision is significantly reduced.

3. Intumescent cataract

Lens absorbs water and increase in size.

4. Hypermature cataract

Lens protein break down into short chain polypeptides, that leaks through lens capsule.

Clinical Manifestations

1. Milky white in pupil

2. Rainbow around beam

3. Loss of vision due to lens opacity

4. Increased glare in bright light

5. Decreased color perception

6. Decreased visual acuity

7. Poor vision at night

8. Light sensitivity/ photophobia 

9. Blurred and distract image

10. Light scattering

11. Peripheral vision loss

12. Contrast sensitivity

Diagnostic Evaluation

1. Ophthalmoscopy

2. Slit lamp biomicroscopy

3. Refraction and Retinoscope

4. Snellen visual acuity test

5. Glare testing

6. Penlight examination of pupil and lens

Surgical Management

1. Capsulotomy

Incision made into capsule of cloudy lens.

2. Extra capsular cataract extraction

Portion of anterior capsule of lens removed, leaving the posterior capsule to support intra-ocular lens (IOL).

3. Intra capsular cataract extraction

Remove entire lens and capsule.

4. Phacoemulsification

Titanium needle vibrating at ultrasonic frequencies used to disrupt the lens nucleus.

Fine instrument chopping nucleus into smaller pieces.

Anterior capsule and lens particles removed from eye by irrigation and aspiration.

Posterior capsule is left to support IOL (intra ocular lens).

5. Intraocular lens implantation

After removal of cataract, intraocular lens (IOL) impant into eye.

6. Cryosurgery 

Freeze lens with cryogenic substance such as liquid nitrogen.

Cataract extracted through use of cryoextractor.

Cryoprobe whose refrigerated tip adheres to and freeze tissue of lens, permitting it's removal.

Preoperative

1. Administer mydriatics and cycloplegic drug to dilate and paralyzed pupil of operative eye .

2. Instill nonsteroidal anti-inflammatory eye drops to reduce inflammation and to help maintain pupil dilation.