Lens And Cataract Flashcards
(26 cards)
What is the lens of eye
Is a transparent biconcave structure just immediately behind the iris
What are the characteristics of lens
Focus the light on retina especially ( macula , fovea)
Derived from ectoderm
Avascular
Highly elastic but it hardness with age
What are the layers of lens ?
Lens capsule
Lens epithelium
Lens differantiated fibers
Lens mature fibers
Lens capsule composed of ?
Collgen type 4 and proteoglycans ( imp in protection and attachment of zonules )
What is the type of lens epithelium ?
Single layer of cuboid cells present only in anterior surface of capsule ( the cells divide to provide new cells that differntiate as lens fibers )
What are the differntiating lens fibers ?
Fibers still have their nuclei elongated and inside their cytoplasm proteins called crystallines
What are the mature lens fibers ?
They lost their nuclei and became densly pached to produced hard structure
What is cataract ?
Opacification of lens of the eye ( become cloudy and opaque )
Cataract is the most common cause of ……… in the world
Treatable blindness
How patients with cataract see the image ?
The image appears blurry , colors are distored and Glare present
Glare( the colors appear shiny and not same as real one )
What are the types of cataract ?
Nuclear cataract
Cortical cataract
Posterior subcapsular cataract
What is nuclear cataract ?
Most common type
Nucleus becomes hard scelortic due to 1) condensation of nucleus
2) deposition of brown pigment
Nuclear cataract present with
Nearsightedness means that the patient has problems with distance vision while reading is less affected
What is the cortical cataract?
Opacification of lens
Result from changes in water content of periphery of lens causes fissuring
The cortical cataract associated with
Glare
Scattering at night
What is the most common cause of cataract ?
Age ( senile cataract )
Age related cause of cataract result from acculations of
Smoking
Alcohol
UV light exposure
Blood suger level ( uncontrolled diabetes )
What are the ocular causes of cataract?
Trauma
Ocular tumors
Uveitis
Steriod
Myopia ( nearsightedness)
What is fabry disease?
X linked lysosomal storage disease
What is Lowe syndrome?
X linked recessive disease characterized by
Congenital cataract
Myotonia areflexia
Mental retraction
Aminoaciduria
Phosphaturia
Proteinurea
Glucoma ( 50% )
What are the systematic disesae associated with cataract?
DM
Metabolic diseases( hypocalcemia , fabry disease, galactosemia)
Medications( steroid , chlorpromazine)
Infections
Myotonic dystrophy
Atopic dermatatis
Congenital
Infections
External radiation
Down syndrome
Lowe’s syndrome
What are the symptoms of cataract?
Glare
Loss of vision
Amblyopia
What are the signs of cataract?
Decreased visual acuity
Lens opacity with SLE
Black spot against red reflex of fundus
Leukocoria
The main stay treatment of cataract?
Surgical removal of lens
