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LENS AND CATARACT

Dr. Ramirez

ANATOMY

- Biconvex- Avascularthats why could be removed in surgery- Colorless- Transparent- 4mm thick- 9mm in diameter- Suspended behind the iris

o Zonules- Aqueous anteriorly- Vitreous posteriorly

COMPOSITION

- 65% water- 35% protein (highest protein content of any tissue of the body)- Trace minerals

o Potassium is more concentrated in the lens than in most tissueso Ascorbic acid, glutathione

- No pain fibers, blood vessels or nervesLAYERS OF THE LENS

FUNCTION

- Focus light rays upon the retinao Distant object

Ciliary muscle relaxes Zonular fibers tautens Reduction of A-P diameter of lens Refractive power of lens is minimized

o Near object Ciliary muscle contracts Zonular tension released Capsule molds lens to a more spherical body Greater refractive power

ACCOMMODATION

- Interplay of:o Ciliary bodyo Zonuleso Lens

- As the lens ages, its accommodative power is greatly reducedPHYSIOLOGY

- Disorders of the lenso Opacificationo Distortiono Dislocationo Geometric anomalies

CATARACT

- Signs and Symptoms1. Painless progressive blurring of vision2. Blurring of vision described as cloudiness3. Monocular diplopia4. Glare they can see clearly but less light

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- Lens opacity- Usually associated with aging- Mostly bilateral- But rate of progression in each eye is seldom equal- Lens edema

o Varies directly wit the stage of cataract development- Protein alteration- Necrosis- Disruption of normal continuity of the lens fibers

CATARACT FORMATION

- Reduction in oxygen uptake- Initial increase in water content- Dehydration- Na and Ca content increased- Ka, Ascorbic Acid, Protein content decreased- UV Light

o Significant factorSTAGES OF CATARACT DEVELOPMENT

- Immature (incipient)o Slightly opaqueo Scattered opacities are separated by clear zones

- Intumescent (swollen)o Water content is maximal and capsule is stretched; more

spherical shape

- Paradoxically, distant vision is blurred but near vision may improveslightly

o Second Sighto Artificial myopia greater convexity of the lens in the incipient

stage

- Matureo Completely opaqueo Somewhat edematous

- Hypermatureo Water has escaped from the lenso Relatively dehydrated, very opaque lenso Wrinkled capsule

AGE-RELATED CATARACT

- Most common type of cataract- Blurred vision and visual distortion- No medical treatment- Cataract surgery is indicated when visual impairment interferes with the

patients normal activities

- If glaucoma secondary to lens swelling (intumescent) occurs, surgery isindicated

COMPLICATIONS

- Glaucoma swollen lens may come in contact with iris (angle closure)- Lens-induced uveitis

CHILDHOOD CATARACT

- Congenitalo Present at birth or appear shortly thereaftero Uni or bilateralo Dense central congenital cataracts require surgery

Amblyopia if not treated within 1st 2 months of life (evenif cataract removed)

- Acquiredo Juvenile Cataracto Aimed at preventing amblyopia

- Surgical treatment- Optical correction

o Spectacleso Contact lenso IOL

TRAUMATIC CATARACT

- Foreign body injuryo BB shot frequent causeo Rocks, iron, overexposure to heat (glassblowers cataract) o X-rays, radioactive materialso Lens becomes white soon after entry of the foreign body

CATARACT SECONDARY TO INTRAOCULAR DISEASE (COMPLICATED CATARACT)

- Chronic recurrent uveitis- Glaucoma- Retinal detachment- Prognosis not good

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CATARACT ASSOCIATED WITH SYSTEMIC DISEASE

- Diabetes mellitus most common- Hypoparathyroidism- Myotonic dystrophy- Atopic dermatitis- Galactosemia- Downs syndrome- Marfans Disease

DISLOCATED LENS (ECTOPIA LENTIS)

- Hereditary Lens Dislocationo Coloboma of the lenso Homocystinuriao Marfans syndrome dislocated lenso Marchesanis syndrome

- Traumatic Lens Dislocationo Following contusion injuryo Iridodonesis (quivering of iris)

TYPES OF CATARACT SURGERY- Intracapsular Cataract Extraction (ICCE) whole lens (anterior, posterior

capsule with nucleus) done in traumatic injury where zonules are detached,

implant cannot be placed

- Extracapsular Cataract Extraction (ECCE)with Intraocular Lens Implant(IOL)posterior capsule left intact; wide incision, puncture anterior capsule o

remove nucleus, place implant then suture

- Phacoemulsification (Phaco) with IOLsmall incision withphacoemulsification machine, suction the lens, less traumatic 2.7 mm

- Femtosecond Cataract Surgerynewer machine, with lens implant after- Intraocular Lens

Multifocal lens

no need for reading glasses

AFTER-CATARACT (SECONDARY MEMBRANE)

- Opacification of posterior capsuleo Traumatic cataracto Cataract surgery

- Persistent subcapsular lens epithelium may attempt regeneration of lensElschnigs pearls

- Neodymium YAG laser