Cataract : Cloudiness of Lens
Definition
A cataract is the clouding of the lens in the eye, leading to progressive vision impairment. It occurs due to changes in the lens proteins and fibers, reducing its transparency and affecting light transmission to the retina.
Causes & Types of Cataract
1. Age-Related Cataract (Senile Cataract) – Most Common
- Oxidative stress leads to protein denaturation and lens opacification.
- Most common age-related cataract.
- Yellowish/brownish discoloration of the central lens nucleus.
- Associated with myopic shift (second sight phenomenon).
Types of Senile Cataract
A. Nuclear Cataract (Nuclear Sclerosis)
- Location: Affects the central (nuclear) part of the lens.
- Appearance: Yellowish or brownish discoloration of the lens nucleus.
Symptoms:
- Gradual progressive decrease in vision.
- Myopic shift (patients may see better up close).
- Glare in bright light.
Complications: Hardening of the nucleus (brunescence) may lead to difficulty in surgical removal.
B. Cortical Cataract
- Location: Affects the peripheral cortical fibers of the lens.
- Appearance: Spoke-like (radial) or wedge-shaped opacities extending from the periphery toward the center.
Symptoms:
- Blurred vision, especially in dim light.
- Glare and difficulty seeing at night.
- Fluctuating vision due to changes in hydration of lens fibers.
C. Posterior Subcapsular Cataract (PSC)
- Location: Just beneath the posterior capsule of the lens.
- Appearance: Granular or plaque-like opacity at the back of the lens.
Symptoms:
- Affects near vision more than distance vision.
- Significant glare and halos around lights.
- Rapid progression compared to other types.
Common in:
- Diabetes mellitus.
- Prolonged steroid use.
- High myopia.
D. Mature Cataract
Definition: A cataract in which the entire lens becomes opaque.
Symptoms:
- Complete loss of red reflex.
- Severe visual impairment or blindness.
- Lens may appear pearly white or completely opaque.
Management: Surgery is the only treatment option.
E. Hypermature (Morgagnian) Cataract
Definition: An advanced stage where lens proteins liquefy, and the nucleus sinks to the bottom.
Symptoms:
- White, milky appearance of the lens.
- Increased risk of complications like phacolytic glaucoma (due to leakage of lens proteins).
Management: Urgent cataract surgery to prevent secondary complications.
2. Congenital Cataract
- Genetic causes (e.g., Down syndrome, galactosemia, rubella).
- Metabolic disorders affecting lens development.
Tyes of congenital cataract:
- Lamellar cataract – Due to metabolic disorders (e.g., hypocalcemia).
- Blue dot cataract – Benign, does not affect vision.
- Rubella cataract – Associated with maternal rubella infection.
3. Traumatic Cataract
- Blunt trauma (e.g., football injury, boxing).
- Penetrating trauma (e.g., glass injury, foreign bodies).
- Radiation exposure (e.g., UV rays, X-rays).
Tyes of Traumatic cataract:
- Rosette cataract – Seen after blunt trauma.
- Glassblower’s cataract – Due to infrared radiation exposure.
4. Secondary Cataract (Complication of Other Conditions)
- Diabetes mellitus – Sorbitol accumulation leads to osmotic damage.
- Uveitis – Chronic inflammation damages the lens.
- Steroid-induced cataract – Prolonged corticosteroid use.
5. Drug-Induced Cataract
- Corticosteroids (oral/inhaled).
- Phenothiazines (e.g., chlorpromazine).
- Amiodarone (used in cardiac arrhythmias).
Diagnosis of Cataract
1. History
- Gradual, painless loss of vision.
- Increased difficulty with night vision.
- Frequent change in glasses due to refractive changes.
2. Clinical Examination
- Visual Acuity Test: Decreased visual acuity assessed with Snellen’s chart.
- Slit Lamp Examination: Best diagnostic tool to assess cataract type and severity.
Investigations
- Biometry (IOL Power Calculation) - Used to calculate intraocular lens (IOL) power before surgery.
- B-Scan Ultrasound - To rule out retinal detachment.
- Blood Tests - Preoperative assessment (blood sugar, CBC).
Management of Cataract
1. Conservative Treatment (For Early Cataract)
- Spectacle correction for mild cases.
- Sunglasses with UV protection to slow progression.
2. Surgical Management (Definitive Treatment)
Indicated when Best Corrected Visual Acuity (BCVA) <6/18 or daily activities are affected.
Types of Cataract Surgery
- Phacoemulsification - Preferred method, uses ultrasound for lens fragmentation.
- Manual Small Incision Cataract Surgery (MSICS) - Used for dense cataracts.
- Extracapsular Cataract Extraction (ECCE) - Larger incision, used in mature cataracts.
Types of Intraocular Lenses (IOLs)
- Monofocal IOL - Fixed focus for distance vision.
- Multifocal IOL - Corrects both near and distance vision.
- Toric IOL - Corrects astigmatism.
Postoperative Care & Complications
Immediate Postoperative Care
- Topical antibiotics & steroids to prevent infection.
- Avoid eye rubbing, heavy lifting, and strenuous activities.
Complications of Cataract Surgery
Early complications:
- Endophthalmitis - Infection inside the eye.
- Corneal edema - Temporary swelling.
- Hyphema - Bleeding in the anterior chamber.
Late complications:
- Posterior Capsular Opacification (PCO) - Managed with YAG laser capsulotomy.
- Cystoid macular edema - Fluid accumulation in the macula.
- Retinal detachment - Rare but serious complication.
Key Points for Exams
- Most common type of cataract = Senile nuclear cataract.
- Most common cause of reversible blindness = Cataract.
- Best method for cataract surgery = Phacoemulsification.
- Complication of steroid use = Posterior subcapsular cataract.
- Management of posterior capsular opacification (PCO) = Nd:YAG laser capsulotomy.
