Kanski Chapter 9 Lens
Terms in this set (33)
Define subcapsular cataract.
Age-related cataract formation either just under the anterior capsule or just in front of the posterior capsule.
Appearance of anterior subcapsular cataract.
Age-related fibrous metaplasia of anterior lens epithelium, typically of little visual impact.
Define posterior subcapsular cataract.
Age related cataract that appears vacuolated granular or plaque-like. Because this cataract is closer to the nodal point of the eye, there is a profound effect on vision, more commonly with near vision and under conditions of miosis (think oncoming headlights).
Define nuclear cataract.
Exaggeration of the normal ageing changes involving the lens nucleus. View with oblique illumination.
Define second sight phenomenon.
Elderly patients may no longer need to wear reading glasses when they begin to develop nuclear cataracts secondary to the increase in refractive index of the lens (causes a myopic shift to correct hyperopia).
Define cortical cataract.
Clefts and vacuoles form in the lens cortex and when opacified, appears as cortical wedge-shaped spokes, most common inferonasally. Patients complain of glare.
Define christmas tree cataract.
Uncommon finding of polychromatic needle-like deposits in the deep cortex and nucleus.
Define maturity levels of cataract.
Immature (partially opaque), mature (completely opaque), hypermature (wrinkling of the cortex), morgagnian (liquefied cortex and sunken lens).
Describe cataracts in diabetes mellitus.
High levels of glucose in the aqueous is converted to sorbitol which causes an osmotic overhydration of the lens and subsequent myopic shift. Cortical fluid vacuoles develop and opacify. Diabetics may develop the classic snowflake cortical cataract or rapidly progressive nuclear cataracts.
Cataracts in myotonic dystrophy.
90% of patients with this disease develop fine cortical opacities early on that develop into visually disabling stellate posterior subcapsular opacities.
Cataracts in atopic dermatitis.
These patients develops a shield like anterior subcapsular plaque. May also develop PSC.
What is the most common cause of secondary cataract?
Chronic anterior uveitis is the most common cause of this lens pathology.
Describe cataracts in the setting of chronic anterior uveitis.
Chronic inflammation (in addition to chronic steroid use) in the anterior chamber leads to breakdown of blood-aqueous and blood vitreous barrier which presents with a polychromatic lustre in the posterior poll of the lens.
Small, grey-white anterior subcapsular or capsular opacities within the pupillary area which represent focal infarcts of the lens epithelium. Findings is almost pathognomonic for past acute-angle closure glaucoma.
What refractive error is associated with secondary cataract?
High myopia is associate with PSC and early-onset NS which ironically increases refractive index, making patient even more myopic. Simply myopia not associated with cataract formation.
What other dystrophy is associated with cataract formation?
Hereditary fundus dystrophy (Leber's, RP, Stickler, gyrate atrophy) associated with PSC.
What is the most common cause of unilateral cataract in a young otherwise healthy individual?
Trauma is the most common cause of unilateral cataract in a young otherwise healthy individual.
Describe the components of phacodynamics.
1. Irrigation flow rate, determined by height of irrigation bottle.
2. Aspiration flow rate, rate of fluid removal, attracts lens mat.
3. Vacuum generated during occlusion, allows for holding.
4. Surge when occlusion is broken. May collapse AC.
How does aspiration flow rate effect phaco.
Higher AFR increases attraction of lens material to phaco tip.
Most common cause of congenital cataracts?
AD mutation is the most common cause for bilateral congenital cataracts.
Define congenital nuclear cataract.
Opacities confined to the fetal nucleus of the lens that may appear as fine dust-like opacities.
Describe congenital lamellar cataracts.
Opacities that affect the anterior or posterior lamella and may may be associated with radial extensions called riders.
Define coronary congenital cataracts.
Supranuclear cataracts that form like a crown around the the nucleus.
Define blue dot cataract.
Innocuous opacities that may be associated with other congenital lens opacities.
Define sutural congenital cataract.
Lens opacities that follow the anterior or posterior Y-shaped sutures.
Define anterior polar cataract.
Conical lens opacity that projects in the anterior chamber, occasionally associated with persistent pupillary membrane, aniridia, Peter's anomaly, and anterior lenticonus.
Define posterior polar cataract.
Cataract occasionally associated with persistent hyaloid remnant (Mittendorf dot), posterior lenitconus, and persistent hyperplastic primary vitreous.
Define central oil droplet.
Opacities characteristic of galactosemia.
Define membranous cataract.
Rare and may be associated with Hallermann-Streiff-François syndrome. It occurs when the lenticular material partially or completely reabsorbs leaving behind residual chalky-white lens matter sandwiched between the anterior and posterior capsules.
What systemic metabolic conditions are associated with congenital cataracts?
Galactosemia (oil droplet cataract), lowe syndrome, fabry disease, mannosidosis.
What intrauterine infections may cause congenital cataracts?
Rubella, toxo, CMV, and Varicella.
What chromosomal abnormalities are associated with congenital cataract?
Down's syndrome, cri du chat syndrome, and Edwards syndrome.
What skeletal abnormalities are associated with congenital cataracts?
Hallerman-Streiff-Francois syndrome and Nance Horan syndrome.
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