Lens and cataract

成大醫院
李美侖
Anatomy of the eye Anatomy of lens y Capsule: ‐‐ basement membrane of lens epithelium
y Zonular fibers
y Lens epithelium
‐‐ a single layer
‐‐ miotic at germinative zone y Nuclerus and cortex
Anatomy of lens y
y
y
y
9~10 mm in diameter
4~5 mm in anteroposteriorly length
255 mg in weight
Aging lens
‐‐ the index of refration decreases
‐‐ increaingly curved shape
‐‐ insolule protein particles increases
‐‐ decrease in lens protein concentration
‐‐ either hyperopic or myopic shift
Embyology of lens y
y
y
y
25 days—optic vesicles
27 days—lens plate
29 days—lens pit
33 days—lens vesicle
(0.2mm in diameter) Lens plate
Lens pit
Optic vesicle
retina
lens
Lens vesicle Embyology of lens y Primary lens fiber
Æembryonic nucleus
Æ40 days
y Secondary lens fibers
Æfetal nucleus
Æ2‐8 months
Æ 90mg
Lens epithelium
Primary lens fibers
(embryonic nucleus)
Fetal nucleus
Secondary lens fibers
Terminal differentiation of lens y
y
y
y
Germinative zoneÆequatorÆlens fibers
Lose oragnelles
Dependent on glycolysis for energy production
No blood supply or innervation after fetal development
Germinative zone
Funtions of lens
y To maintain its own clarity
y To refract light
y To provide accommodation
43‐47D
15‐20D
Pathology of lens
y
y
y
y
y
y
Aging changes
Drug‐induced lens changes
Metabolic cataract
Developmental defects
Lens‐induced glaucoma
Trauma
Anging changes
y Nuclear cataracts
Ægreater impairment of distance vision than of near vision
y Cortical cataracts
y Posterior subcapsular cataracts (PSCs)
Æ greater impairment of near vision than of distance vision
Drug‐induced lens changes
y Corticosteroids
Æ PSCs
Æ dose and duration
y Phenothiazines
Æ pigmented deposits in the anterior lens epithelium
y Miotics
y Amiodarone
Æstellate anterior axial pigment depsition
y Statins Metabolic cataract
y Diabetes Mellitus
‐‐ snowflake cataract
y Galactosemia
y Wilson disease
‐‐ sunflower cataract
Developmental defect
y Ectopia lentis
‐‐ subluxated, dilocated
‐‐ congenital: aniridia
‐‐ developmental: Marfan syndrome, homocystinuria, Weill‐Marchesani syndrome ‐‐ acquired: trauma Lens‐induced glaucoma
y Phacolytic glaucoma
‐‐ mature or hypermature cataract
‐‐ Tx: surgical removal
y Lens‐particle glaucoma
‐‐ residual lens material after surgical event or penetrating lens injury
‐‐ Tx: medication + surgical removal
y Phacomorphic glaucoma
‐‐ intumescent cataract causing pupillary block glaucoma
‐‐ Tx: laser iridotomy and cataract removal
Trauma y
y
y
y
Vossius ring
Traumatic cataract
Dislocation and subluxation
Perforating and penetrating injury
Surgery for cataract
y
y
y
y
Intracapsular cataract extraction(ICCE)
Extratracapsular cataract extraction(ECCE)
Phacoemulsification Intraocular lens implanation (IOL)
‐‐ anterior chamber IOL
‐‐ posterior chamber IOL
Complication of catarct surgery
y
y
y
y
y
y
y
y
Retinal detachment
Capsular rupture
Wound leak
Retained lens material
Posterior capsule opacifiacation
IOL decentration and dislocation
Postoperative endophthalmitis
Pseudophakic bullous keratopathy