Cataract

LENS

• Diameter: 9-10 mm

• Thickness: 3.5mm at birth, 5mm (in elderly)

• Ant. Surface < convex than Post. Surface

• Refractive Index: 1.39

• Refractive Power: 15-16D

Structure

• The Lens Capsule

• The Lens Epithelium

• The Lens Cells or Fibers

Lens Capsule

• Thin + Transparent + Hyaline + Collagenous membrane

• Highly elastic but does not contain any elastic tissue.

• Thicker anteriorly than posteriorly

• Rich in type IV collagen

Thickness of Lens CapsuleAnterior Pole

Posterior Pole

21µm21µm

14µm

17µm 17µm

23µm 23µm

4µm

Embryonic Nucleus

Foetal Nucleus: The lens at birth

Infantile Nucleus: Lens at puberty

Adult Nucleus: Lens in early adult life

Cortex: Peripheral part comprises youngest lens fibers, increases in size with age

• Fiber cells contain large no. of negatively charged crysytallins, so a large no of positively charged cations enter the lens cells

• Resulting ion gradient provides energy for other membrane transport processes like sodium-calcium, sodium-bicarbonate and amino acid transport

• Na-K ATPase uses energy from 1 molecule of ATP to pump 3 molecules of Na+ outward and 2 molecules of K+ inward

• Major site of cation transport is anterior epithelium

Transport of Ions

Formation of Lens vesicle

• Optic Vesicle Optic Vesicle grows laterally.grows laterally.

• Surface ectoderm Surface ectoderm over optic vesicle over optic vesicle thickened to form thickened to form Lens Placode.Lens Placode.

• Lens Placode Lens Placode sinks below sinks below surface and surface and converted into converted into lens vesiclelens vesicle

Lens

• Formed from Lens vesicle• Cells of Post. Wall elongate to form Lens fibres• Ant. Wall equitorial cells form rest of the fibres• Lens capsule produced by cells of lens by 5th week

• Embryonic Nucleus: formed between 1st and 3rd month of fetal life, consists of transparent primary lens fibres.

• Fetal Nucleus: 3rd to 8th month,

consists of secondary lens fibres.

• Infantile Nucleus: formed during last week of fetal life to puberty

• Adult Nucleus: Formed after pubertyCortex consists of recently formed lens

fibres

Definition of cataract• Opacity of the lens, which occurs when fluid gathers between

the lens fibers.When eyes work properly:• Light passes through the cornea and the pupil to the lens.• The lens focuses light & producing clear, sharp images on

the retina.• As a cataract develops, the lens becomes clouded, which

scatters the light and prevents a sharply defined image from reaching retina. As a result, vision becomes blurred.

Epidemiology

1. Cataracts remain the leading cause of blindness.

2. Age-related cataract is responsible for 48% of world blindness, which represents about 18 million people

3. Cataracts are also an important cause of low vision in both developed and developing countries.

Causes of cataract

• Old age (commonest)• Ocular & systemic diseases

– DM– Uveitis– Previous ocular surgery

• Systemic medication– Steroids– Phenothiazines

• Trauma & intraocular foreign bodies

• Ionizing radiation– X-ray– UV

• Congenital– Dominant– Sporadic– Part of a syndrome– Abnormal galactose

metabolism– Hypoglycemia

• Inherited abnormality– Myotonic dystrophy– Marfan’s syndrom– Rubella– High myopia

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Cataract

Divided to :• Acquired cataract

Age - related cataract

Presenile cataract

Traumatic cataract

Drug induced cataract

Secondary cataract• Congenital Cataract

Systemic association

Non-systemic association

Age -related cataract It is the Most commonly occurred.

Classified according to:Morphological Classification

• Nuclear• Cortical• Subcapsular• Christmas tree – uncommon

Maturity classification

• Immature Cataract • Mature Cataract • Hypermature Cataract

Nuclear cataract• Most common type• Age-related• Occur in the center of the lens.• In its early stages, as the lens changes the way

it focuses light, patient may become more nearsighted or even experience a temporary improvement in reading vision. Some people actually stop needing their glasses.

• Unfortunately, this so-called 2nd sight disappears as the lens gradually turns more densely yellow & further clouds vision.

• As the cataract progresses, the lens may even turn brown. Advanced discoloration can lead to difficulty distinguishing between shades of blue & purple.

Cortical cataract • Occur on the outer edge of the lens (cortex).

• Begins as whitish, wedge-shaped opacities or streaks.

• It’s slowly progresses, the streaks extend to the center and interfere with light passing through the center of the lens.

• Problems with glare are common with this type of cataract.

Subcapsular cataract

• Occur just under the capsule of the lens.

• Starts as a small, opaque area

• It usually forms near the back of the lens, right in the path of light on its way to the retina.

• It’s interferes with reading vision

• Reduces vision in bright light

• Causes glare or halos around lights at night.

Posterior Subcapsular Cataracts

• Begins at the back of the lens (posterior pole) & spreads to the periphery or edges of the lens.

• It can be developed when:

– Part of the eye are chronically inflamed.

– Heavy use of some medications (steroids).

• Affects vision more than other types of cataracts because the light converges at the back of the lens.

• Anything constrict the pupils (bright light) makes it very difficult for people with this type of cataract to see.

• Dilating drops useful in this type by keeping the pupils large and thus allow more light into the eye.

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Immature Cataract Lens is partially opaqueTwo morphological forms are seen:1.Cuneiform Cataract:

– Wedge shaped opacities in the peripheral cortex and progress towards the nucleus.

– Vision is worse in low ambient illumination when the pupil is dilated.

2.Cupuliform Cataract:– A disc or saucer shaped opacities beneath the posterior

capsule.– Vision is worse in bright ambient illumination when the

pupil is constricted. Lens appears grayish white in color.Iris shadow can be seen on the opacity with oblique illumination.

Mature Cataract

• Lens is completely opaque.

• Vision reduced to just perception of light

• Iris shadow is not seen

• Lens appears pearly white

Right eye mature cataract, with obvious white opacity at the centre of pupil

Hypermature Cataract

• Shrunken and wrinkled anterior capsule due to leakage of water out of the lense.

• This may take any of two forms:

1.Liquefactive/Morgagnian Type

2.Sclerotic Cataract

Liquefactive/Morgagnian Type

• Cortex undergoes auto-lytic liquefaction and turns uniformly milky white.

• The nucleus loses support and settles to the bottom.

Sclerotic Cataract

• The fluid from the cortex gets absorbed and the lens becomes shrunken.

• There may be deposition of calcific material on the lens capsule.

• Iridodonesis: Anterior chamber deepens and iris becomes tremulous.

• The zonules become weak, increasing the risk of subluxation / dislocation of lens.

• 1)Diabetic cataract• a)Snow flakes cataract(true diabetic cataract):• -It occurs typically in young type 1 diabetics(insulin dependent)• -It starts as “fluid vacuoles” then a cloud of opacities resembling

“snow-flakes” appear all over the lens and finally becomes totally milky white.

• b)Pre-Senile cataract:• -It stimulates senile cataract but it develops at an earlier age• 2)Hypo-paratyrodism• 3)Severe anemia• 4)Toxic(Naphthalene,didnitrophenol,ergot,thalium, and systemic

cortisone)• 5)Radiation(infra red in glass blowr cataract,x ray ,electric cataract

and ultrasonic radiation)• 6)Other systemic diseases:atopic dermatitis,myotonia

dystrophica,sclerodermia,mongolism, and cretinism.)

• -Positive history of ocular or systemic diseases.• -The age may be suggestive (young age).• -The opacity starts in the posterior subcapsular

area,shows polychromatic luster )characteristic rainbow display of colors) seen on slit lamp examination .

• -The opacity may progress to total opacity with chalky white appearance (excessive calcium deposition).

• -The eye shows sign of the original disease e.gKPs of iridocyclitis,High intraocular pressure or bad projection of light in retinal detachment.

•  

Complicated cataract - diabetesJuvenile

• White punctate or snowflake posterior or anterior opacities

• May mature within few days

Adult

• Cortical and subcapsular opacities

• May progress more quickly than in non-diabetics

Complicated cataract - myotonic dystrophy

• Myotonic facies• Frontal balding • 90% of patients after age 20 years

• Stellate posterior subcapsular opacity

• No visual problem until age 40 years

Complicated cataract - atopic dermatitis

• Cataract develops in 10% of cases between 15-30 years

• Bilateral in 70%

• Frequently becomes mature

• Anterior subcapsular plaque (shield cataract)• Wrinkles in anterior capsule

Causes of traumatic cataract

Penetration

Concussion

‘Vossius’ ring from imprinting of iris pigment Flower-shaped

• Ionizing radiation

• Electric shock

• Lightning

Other causes

DrugsChlorpromazine

• Long-acting mioticsOther drugs

• Amiodarone• Busulphan

- initially posterior subcapsularSystemic or topical steroids

- central, anterior capsular granules

Secondary (complicated) cataract

• Chronic anterior uveitis• High myopia

Posterior subcapsular

• Hereditary fundus dystrophies • Central, anterior subcapsular opacities

Glaukomflecken

• Follows acute angle-closure glaucoma

• LOCS III

Symptoms

• A cataract usually develops slowly, so:

– Causes no pain.– Cloudiness may affect only a

small part of the lens– People may be unaware of any

vision loss.• Over time, however, as the

cataract grows larger, it:– Clouds more the lens– Distorts the light passing

through the lens.– Impairs vision

• Reduced visual acuity (near and distant object)

• Glare in sunshine or with street/car lights.

• Distortion of lines.

• Monocular diplopia.

• Altered colours ( white objects appear yellowish)

• Not associated with pain, discharge or redness of the eye

Signs• Reduced acuity.• An abnormally dim red reflex is seen when the eye is

viewed with an ophthalmoscope.• Reduced contrast sensitivity can be measured by the

ophthalmologist.• Only sever dense cataracts causing severely impaired

vision cause a white pupil.• After pupils have been dilated, slit lamp examination

shows the type of cataract.

Treatment

• Glasses: Cataract alters the refractive power of the natural lens so glasses may allow good vision to be maintained.

• Surgical removal: when visual acuity can't be improved with glasses.

• Surgical techniques

– Phacoemulsification method.

– Extracapsular method.

– Intracapsular method

Pre-op assesments

• General health evaluation including blood pressure check• Assessment of patients’ ability to co-operate with the

procedure and lie reasonably flat during surgery• Instruction on eye drop instillation• The eyes should have a normal pressure, or any pre-existing

glaucoma should be adequately controlled on medications.• An operating microscope is needed, in order to reach the lens,

a small corneal incision is made close to the limbus for the phaco-probe.

• It is important to appreciate anterior chamber depth and to keep all instruments away from the corneal endothelium in the plane of the iris.

Extra-capsular Cataract Extraction (ECCE)

• The nucleus and the cortex is removed out of the capsule leaving behind:

• Intact posterior capsule

• Peripheral part of the anterior capsule

• Zonules.

• This method:

• Provides support of placement of IOL

• Prevents vitreous from bulging forwards

• Acts as a barrier between anterior and posterior segment.

• All this results in decreasing the incidence of complications.

Intra-capsular Cataract Extraction

• The lens is removed as one single piece i.e., the nucleus and the cortex are removed within the capsule of the lens after breaking the zonules.

• There is no support left for posterior chamber IOL, therefore, only anterior chamber IOL (ACL) can be implanted which has risk of adverse corneal complications.

• There is no barrier left between anterior and posterior segment, which increases the incidence of other complications.

• The only advantage is that after-cataract does not develop as the entire capsule is removed.

Phacoemulsification:1. Corneal incision 2.75-3.2 mm2. Viscoelastic to anterior chamber.3. Capsulorhexis4. Hydrodissection.5. Phacoemulsification of the nucleus.6. Aspiration of the cortex.7. More viscoelastic.8. Folded intraocular lens (IOL) is inserted under a cushion of

viscoelastic fluid which protect the corneal endothelium, the lens unfold spontaneously within the capsular bag.

9. Vescicoelastic removed and replaced with balanced salt solution.

10. Self sealing wound.

11. Sub conjunctival injection of steroid and antibiotics

12. Eyepad and protection eye shield.

Phacoemulsification in cataract surgery involves insertion of a tiny, hollowed tip that uses high frequency (ultrasonic) vibrations to "break up" the eye's cloudy lens (cataract). The same tip is used to suction out the lens

.

Postoperative care after cataract surgery

• Steroid drops (inflammation)• Antibiotic drops (infection)• Avoid

• Very strenuous exertion (rise the pressure in the eyeball)• Ocular trauma.

Complications of cataract surgery• Infective endophthalmitis

– Rare but can cause permanent severe reduction of vision.– Most cases within two weeks of surgery.– Typically patients present with a short history of a reduction in their

vision and a red painful eye.– This is an ophthalmic emergency.– Low grade infection with pathogen such as Propionibacterium species can

lead patients to present several weeks after initial surgery with a refractory uveitis

• Suprachoroidal haemorrhage.– Severe intraoperative bleeding can lead to serious and permanent

reduction in vision.

• Uveitis– Postoperative inflammation is more common in certain types of eyes for

example in patients with diabetes or previous ocular inflammatory disease.

• Ocular perforation.

• Postoperative refractive error– Most operations aim to leave the patient emmetropic or slightly myopic, but

in rare cases biometric errors can occur or an intraocular lens of incorrect power is used.

• Posterior capsular rupture and vitreous loss– If the very delicate capsular bag is damaged during surgery or the fine

ligaments (zonule) suspending the lens are weak (for example, in pseudoexfoliation syndrome), then the vitreous gel may prolapse into the anterior chamber. This complication may mean that an intraocular lens cannot be inserted at the time of surgery. Patients are also at increased risk of postoperative retinal detachment.

• Retinal detachment.– This serious postoperative complication is, fortunately rare, but is

more common in myopic patients after intraoperative complications.

• Cystoid macular oedema– Accumulation of fluid at the macula postoperatively can reduce the

vision in the first few weeks after successful cataract surgery. In most cases this resolves with treatment of the post-operative inflammation.

• Glaucoma– Persistently elevated intraocular pressure may need treatment

postoperatively.

• Posterior capsular opacification– Scarring of the posterior part of the capsular bag, behind the

intraocular lens, occurs in up to 20% of patients. Laser capsulotomy may be needed.