Guide to Cataracts: Types, Causes, and Treatments

Any opacity in the lens that hinders the optical homogeneity of the lens is known as a cataract.

Classification of Cataracts

A cataract can be congenital or acquired.

Congenital 

• Infantile → <1 year 
• Developmental → >1 year 

Acquired Cataract

This can be classified in 3 ways:

• Anatomically 
• Maturity 
• Etiologically

1. Anatomically

We classify based on where the cataract starts from in the anatomy of an eye. 

• Anterior Subcapsular (ASC)
• Anterior Cortical
• Nuclear Cataract
• Posterior Cortical Cataract
• Posterior Subcapsular Cataract (PSC)/Cupuliform Cataract
• Anterior Polar Cataract
• Posterior Polar Cataract

2. Maturity

We can classify according to maturity as:

• Immature: Some part of the lens is clear; some part is opaque.
• Mature: All parts of the lens are opacified.
• Hyper-mature: Degenerative changes occur. Hypermature cataracts can cause 2 types of degenerative changes:
• Morgagnian Cataract: Liquefaction of the cortex causing nucleus to float, Wrinkling of capsule.

Sclerotic Cataract: Wrinkling of capsule, shrunken lens.

• Iris shadow is formed when there is an immature cataract, i.e., partially cataract, partly clear, causing the shadow of the opacified portion to fall on the lens.

3. Etiological

They are classified based on etiology as

• Senile (Most common cataract)
• Metabolic
• Complicated/Secondary
• Toxic
• Traumatic
• Radiational
• Associated with systemic disease (pre-Senile) <50 years of age

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Senile cataract

They are further divided as cortical, nuclear, and sub-capsular.

Cortical Cataract

• It occurs primarily due to hydration.
• Water collects between the fibers, forming clefts and vacuoles. This gives rise to different stages of hydration.
  • Stage I - Stage of lamellar separation
  • Stage II - Incipient stage (Cuneiform cataract)
  • Stage III: -Intumescent (Maximum hydration)
  • Stage IV - Mature Cataract
  • Stage V—Hyper-mature Cataract 

• Morgaian
• Sclerotic

Nuclear cataract

• The etiology is nuclear sclerosis.
• Sclerosis can be caused by an increase in insoluble protein and a decrease in soluble protein, denaturation of the protein (dehydration), and deposition of pigments such as melanin and urochrome.
• Although official grading of nuclear cataracts is not based on colors, we can classify the maturity of the cataract based on its color:
  • G1 - Yellow - Xanthopsia (Yellow Vision)
  • G2 - Amber
  • G3 - Brown - Brunescence
  • G4 - Black - Nigra
• Dehydration crisis: due to recurrent diarrhea, it can also cause cataracts because of the denaturation of proteins.

Subcapsular

• Anterior Subcapsular (ASC) due to fibrous dysplasia of anterior epithelial cells.
• Psular (PSC): The pupil dilates at night, giving rise to scattering of light that causes glare, especially while driving. Dysplasia of E cells, Wedl cells, or bladder cells. During the day, there is meiosis that leads to a decrease in visual acuity and difficulty in near vision.

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Associated with systemic disease (Pre-Senile) 

Any cataract that is developed within the age of 50 years.

They are divided into different categories as:

• Diabetes Mellitus (DM), aka metabolic cataract
• Myotonic Dystrophy (MD),
• Atopic Dermatitis
• Neurofibromatosis-Type 2

The most common ocular feature of NF-κB is that it causes PSC. Atopic dermatitis is associated with shield cataract, which is a kind of ASC.

• The image below depicts a Christmas tree cataract, which is associated with myotonic dystrophy. It involves the cortical part and can be a PSC too.

• It has polychromatic needle-like opacities.

Ocular Features of Myotonic Dystrophy: The P’5s

• Ptosis
• Presenile Cataract (Christmas-tree cataract)
• Intraocular Pressure (IOP): Low
• Pigmentary Retinopathy: salt and pepper pigments
• Pupil: Miotic, reacting slowly to light.

Metabolic Cataract 

Diabetes Mellitus (DM)

• It occurs due to sorbitol accumulation. Sorbitol is hyperosmotic, and any hydration will lead to cataracts.
• The enzyme responsible for the pathway is NADPH-dependent aldose reductase.
• It can be a snowflake or snowstorm cataract.
• Snowflake/Snowstorm is more common in Type-1 DM.
• Fluctuating refractive errors occur in hyperglycemic patients because of myopic shifts. This is due to swelling that in turn increases the curvature.
• In cases of hyperglycemia, we see a shift; vice versa, in cases of hypoglycemia, we observe a hypermetropic shift (towards lesser curvature).
• Frequent changes of Presbyopic glasses are caused by:
  • Early cataracts (Intumescent cataracts)
  • Late glaucoma (late stage of primary open-angle glaucoma) (POAG) can crescent with fluctuating refractive errors.

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Galactosemia

• It can occur due to 2 enzyme deficiencies, and they are:
  • Galactokinase - This deficiency causes Lamellar cataract.
  • Galactose-Phosphate-Uridyl Transferase (GPUT): This deficiency causes oil-droplet cataracts, as shown below:
    • It is also known as reversible cataract.

Chalcosis

• It means copper alloy in the eye.
• It is caused by:
  • Wilson's disease
  • Any copper-containing foreign body.

• The image below depicts a sunflower cataract.
• Kayser-Fleischer Ring (KF-Ring) is copper disposition in Descemet's membrane in the cornea. It is reversible (fading).

• It starts superiorly and inferiorly to make a circle.
• 95-100% of patients with neurological complications will present with KF-ring, whereas only 65-67% of patients with hepatic involvement will present with KF-ring.
• Fleischer's Ring is an iron deposition on the epithelium layer and appears in patients with keratoconus (conical deposition at cornea).

Complicated Cataract/Secondary Cataract

• The pathognomonic feature of complicated cataract is polychromatic lustre with a bread-crumb appearance.
• The most common type of complicated cataract is posterior secondary cataract (PSC).

Etiologies

The most common cause of complicated cataracts is chronic anterior veitis. High Myopia (mostly PSC)

Hereditary Fundus dystrophy—it can lead to:

• Retinitis Pigmentosa (RP)
• Leber's Amaurosis
• Gyrate atrophy
• Stickler Syndrome

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Toxic Cataract

• It can be caused by:
  • Steroids: They disturb the osmotic balance in the lens.
  • Phenothiazines
  • Long-Acting Miotics such as Echothiophate, Phospholine Iodide, and DFP.
  • Amiodarone
  • Busulfan
  • Gold
  • Chloroquine
• An easy mnemonic to remember the drugs and respective cataracts is shown above.
  • B-S-C causes PSC, and the rest of the drugs on the list cause ASC.
  • The most common complication of topical steroids in the eye is glaucoma (OAG) due to deposition of mucopolysaccharides in TM.
  • The most common complication of systemic steroids is cataract (PSC).

Traumatic Cataract

• Perforating/Penetrating: It can lead to cataracts if it hits the lens.
• Blunt Trauma: It is also called concussion injury.
• Features of blunt trauma:
  • Rosette-shaped cataract: It is a cortical cataract that starts from the posterior cortex.

Types of Congenital Cataracts

1. Blue Dot Cataract

• This is the most common type of congenital cataract. 
• Bluish dots are seen on the lens as cataract opacities. 
• It is also a feature of Down syndrome. 
• Both the nucleus and the cortex of the lens are affected. 

2. Lamellar/Zonular Cataract 

• Due to some environmental insult, one lamella can develop cataracts, but the adjacent 

areas are clear. 

• Over this cataract, there can be small spoke-like opacities called the RIDERS.
• Etiology: This condition can develop due to vitamin D deficiency or rubella infection. 
• This only involves the foetal nucleus. 
• This is the most common infantile cataract. 
• This is the most common congenital cataract causing a marked diminution of vision. 

3. Anterior Polar Cataract 

• It starts from anterior pole.
• This is generally associated with the persistent pupillary membrane. 

4. Posterior Polar Cataract 

• This can be associated with remnants of hilar tissues known as Mittendorf dots. 
• An onion ring appearance is seen. 

5. Coronary Cataract 

• Peripheral cortical opacities are seen in this condition. 

6. Sutural Cataract 

• The opacities are only seen along the sutures. 
• From the front, it looks like Y, and from the back, it looks like an inverted Y. 
• Wilson disease causes sunflower cataract. 
• Galactosemia causes oil droplet cataracts. 

7. Total Congenital Cataract 

• The whole lens is opaque when the child is born. 

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Clinical Features of Cataracts

The child presents with congenital cataracts.

• Leukocoria: It is also known as the white eye reflex.

Investigation

First, a detailed eye examination is to be done.

• A scan is done for the anterior chamber to check for IOL power and axial length.
• B scan is done for the posterior chamber.
  Then the investigation is divided into two types:

1. Ocular: A scan and B scan are done.
2. Systemic: It is not done in unilateral cataracts or bilateral cataracts with positive family history. It is done to find other causes of cataracts. This can be of two types:
   • Serum analysis: In this, glucose level, galactokinase level, calcium, phosphorus levels, and TORCHS titre levels are checked.
   • Urine analysis:
     • Reducing substances in the urine indicate galactosemia.
     • Amino acids in the urine indicate Lewis's syndrome.
     • If sediments are detected in the urine, then it is Fabry's disease.
     • The detection of copper in the urine indicates Wilson's disease.
     • Blood in the urine indicates Alport's syndrome (familial hemorrhagic nephritis).

Pre-operative Assessment

Systemic Condition:

• Sugar Level: DM (Diabetes Mellitus).
• Hypertension: Make the blood pressure normal for the surgery.
• Respiratory System: The patient should not have a cough or upper respiratory infections because if the patient coughs after or during the surgery, it will be harmful.
• History of Myocardial Infarction or Stroke: Surgeons have to wait for 4-6 months.
• If the patient has epilepsy or Parkinson's disease.

Treatment of the Cataract

There is no medical treatment or prevention of cataracts. The only option is surgery. These surgeries are explained in detail below:

• ICCE: Intracapsular cataract extraction; the capsule is removed along with the lens.
• ECCE: Extracapsular cataract extraction; the capsule is not removed.
• SICS: Small-Incision Cataract Surgery; it can be manual or with the help of phacoemulsification.
• FLCS: Femto Laser Cataract Extraction.

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Complications of Cataract Surgery

1. Operative complications
   • Vitreous loss
   • Posterior loss of lens fragments
   • Suprachoroidal (expulsive) hemorrhage
2. Early postoperative complications
   • Iris prolapse
   • Striate keratopathy
   • Acute bacterial endophthalmitis
3. Late postoperative complications
   • Capsular opacification
   • Implant displacement
   • Corneal decompensation
   • Retinal detachment
   • Chronic bacterial endophthalmitis

Also read: Complications Of Cataract Surgery 

Endophthalmitis

It is the purulent inflammation of intraocular fluids, usually due to infection.

Etiology

The most common etiological factor that causes the acute onset of endophthalmitis is Staphylococcus epidermidis.

Clinical Features

All these signs and symptoms rapidly progress:

• Worsening of vision
• Redness
• Pain
• Photophobia
• Blepharospasm
• Discharge

Note: Two eyes are never operated simultaneously, as postoperatively there can be infection and diminishing of vision in both eyes. A minimum of a 2-week interval should be there before the surgery of the other eye.

On Examination:

• There is progressive diminution of vision.
• Lid swelling
• Chemosis
• Corneal edema
• Hypopyon: It is the presence of pus cells in the anterior chamber.
• All the signs of anterior uveitis may be present.
• Vitritis: Hallmark
  • There are a lot of inflammatory cells and exudates in the vitreous, due to which the media is hazy.
• Fundal glow is absent in severe and late cases.
• Retinal peri-phlebitis

Treatment:

According to EVS (Endophthalmitis Vitrectomy Study):

• Check the Vision: As per the vision, treatment can be of two types:
  • If there is no hand movement, then the treatment is pars plana vitrectomy.
    • For pars plana vitrectomy, entry from the vitreous is through pars plana, i.e., the eye is entered 3.5 mm from the limbus to avoid damage to zonules and lenses.
  • If there is hand movement or better vision, then the patient is treated conservatively.

Treatment of choice for endophthalmitis: Intravitreal antibiotic injections. The antibiotics given are ceftazidime and vancomycin. Small doses of dexamethasone are given to control inflammation.

Systemic antibiotics that are given due to their higher ocular penetration are quinolones. Management of associated uveitis is done by giving cycloplegics and topical steroids under cover.

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