Lens Anatomy and Cataracts

• Cataracts are the leading cause of reversible blindness
• Cataracts are an age-related disorder
• Cataracts are a disease/disorder of the lens

Anatomy of the Lens

• The lens is a biconvex structure attached to the ciliary process by the zonular fibers, between the iris and vitreous humor
• The lens is non-vascular, colorless, and transparent
• Index of Refraction: 1.336
• The lens consists of stiff, elongated prismatic cells known as lens fibers, which are tightly packed together
• The lens is divided into the nucleus, cortex, and capsule
• It is enclosed within an elastic fibers capsule
• It helps to refract incoming light and focus it onto the retina
• Diameter: 9-10mm
• Thickness: 3.5mm at birth, 5mm in adults
• Weight: 135mg (0-9 years), 255mg (40-80 years)
• Refractive Index: 1.39
• Dioptric Power: +18D
• Accommodation Power: +14-16D (at birth) and 7-8D (at 25-40s)
• Accommodation power decreases with age

Anterior Lens Epithelium

• The anterior lens epithelium is a single layer of cells beneath the lens capsule
• It is formed of cuboidal cells that become columnar at the equator

Lens Fibers

• Lens fibers are elongated epithelial cells with a complicated structure
• Mature lens fibers are cells that have lost their nuclei
• Lens fibers are arranged compactly as the nucleus and cortex of the lens are formed throughout life

Cortex

• The cortex is the peripheral part which comprise the youngest lens fibers

Nucleus

• The nucleus is the central part consisting of the "oldest fibers"
• It consist of different zone, which laid down successively as the derlopmet proceeds
• Different zones include Embryonic, Fetal, Infantile and Adult

Lens Transparency

• Lens transparency is due to the arrangement of its fibers, internal structure, and biochemistry of lens cells and fibers
• A cataract lens is an opaque lens
• Cataracts are part of the aging process

Cataracts

• A cataract refers to the clouding of a lens or any opacity within the lens which causes decreases in vision
• Lens fibers become opaque when a cataract is present

Causes of Cataracts

• Congenital: Familial or due to intrauterine infection, maternal drug ingestion
• Age: Most cataracts are common in the elderly
• Metabolic: Diabetes, hypocalcemia, Wilson’s diseases, galactosemia
• Drug-Induced: Corticosteroids, Prednisolone, Miotics, Amiodarone, Phenothiazine
• Traumatic and Inflammatory: Post intraocular surgery, uveitis, external trauma

Diseases Associated with Cataracts

• Down's Syndrome
• Dystrophia myotonia
• Lowe's Syndrome
• Atopic dermatitis

Morphological Classifications of Cataracts

• Subcapsular Cataract: Can be anterior or posterior
• Nuclear Cataract: Involves the nucleus of the lens, often yellow to brown in color
• Cortical Cataract: Has a wedge-shaped/radial or spoke-like opacity
• Polar Cataract: Located in the central posterior part of the lens

Stages of Maturation

• Stage of Lamellar Separation
• Stage of Incipient: (a) cuneiform cataract (periphery) or (b) cupuliform (center opaque)
• Immature Cataract: Lens is partially opaque, pearly greyish
• Mature Cataract: Lens is completely opaque, pearly white
• Hypermature Cataract: (i) Morgagnian cataract or (ii) sclerotic (cortex and nucleus become brown)
• In Morgagnian cataracts liquefaction of the cortex allows the nucleus to sink inferiorly
• Sunken and wrinkled anterior capsule due to loss of H2O rate of lense

Immature Cataracts

• Opacification becomes more diffuse and irregular
• An iris shadow is still visible
• The lens is not completely opaque
• Wedge-shaped opacities at the periphery of the lens
• It progresses gradually
• A clear cortex exist between the iris and senile cataract opacity (greyish white in immature senile cataract)
• Light cast on the eye is visible through the dense cortex.

Mature Cataracts

• Complete opacification of lens, capsule, cortex, and nucleus
• The lens appears "pearly white"
• Progresses to Hypermature Cataract
• May be complicated with Phacolytic Glaucoma

Just Counting (JC) vs. More change (MC)

• JC - Visual acuity reduced to finger counting
• MC -Visual acuity reduced to hand movement or perception of light
• JC - Lens is partially opaque
• MC - Lens is totally opaque
• JC - iris shadow is present
• MC - No fundus details are visible, where fundus may be visible

Hypermature Cataracts

• Hypermature cataracts are characterized by "wrinkling of the capsule" due to the dense vortex and morgagnian
• Sinking of lens (nucleus at nfs) means loss of power to focusing
• Characterized with inflammation, eye pain, headache

Common signs (C), Findings (F), Complaint(C/O) and or History (H/O)

• Decreased visual acuity.
• Progressive and painless.
• Worse in bright light.
• Glare and monocular diplopia.
• Sometimes see white or cloudy image reflex in pupil

Ape Scan and Keratometer

• "Ape scan" is for refractive power determination.
• "Keratometer" measures the curvature of the cornea.

Treatments for Cataracts

• Glasses
• Better lighting/illumination
• Surgery:
  • Phacoemulsification:

Surgical Methods for Cataract Extraction

• ICCE (Intracapsular Cataract Extraction)
  • Involves extraction of the entire lens, including the "posterior capsule and zonules"
  • Requires "weak and degenerated zonules"
  • Choice of surgery if the lens is markedly subluxated/dislocated
• ECCE (Extracapsular Cataract Extraction)
  • 5mm-6mm incision made where the clear front covering of the eye (cornea) meets the white part of the eye
  • Removal of the lens capsule along with any remaining lens material
  • An "IOL" may then be placed inside the lens capsule and the incision is closed
  • It is usually done if the cataract is too large to be destroyed by the ultrasound

Complications of Cataract Surgery

• Infection in the eye
• Swelling and fluid in the center of the retina layer (Cystoid Macular Edema)
• Swelling of the clear covering of the eye (corneal edema)
• Hyphema (bleeding in front of the eye)
• Retinal Detachment

Comparing ECCE and ICCE

• ECCE incision is 5-6mm, ICCE incision is 10-12mm
• With ECCE the posterior lens is conserved, With ECCE entire remove of leas
• With ECCE no stitches are required and the eye heals itself, With ICCE stitches are required and the eye takes Longer to heal
• Both implantation methods can use IOL, but ICCE can result in an aphakic eye.
• ECCE post-operative care is minimal, ICCE post-operative care is more

Steps of phacoemulsification

• Titanium needle is inserted into the anterior chamber.
• A foldebable IOL is is now be serted
• Next Nucleus expression
• Nucleus is then aspirated away