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Lens and Cataract > Anatomy, Biochemistry, Physiology, Embryology and Development > Flashcards

Anatomy, Biochemistry, Physiology, Embryology and Development Flashcards

1
Q

index of refraction of lens

A

1.4 centrally, 1.36 peripherally

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2
Q

average nonaccommodative power of lens

A

15-20 D

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3
Q

size of lens at birth? adult?

A

birth: 6.4mm equatorially and 3.5mm A-P
adult: 9mm equatorially and 5mm A-P

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4
Q

refractive changes in lens due to age?

A

decreasing refractive index, increased relative thickness of cortes, increasingly curved shape, and overall increased refractive power

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5
Q

what substance predominantly makes up lens capsule

A

type IV collagen

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6
Q

thinnest portion of lens capsule

A

posterior pole

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7
Q

largest lens crystalline? most abundant? smallest?

A

largest: alpha
most abundat: beta
smallest: gamma

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8
Q

increase or decrease in water insoluble lens proteins with age?

A

increase

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9
Q

rate limiting step in glucose metabolism in lens?

A

posphorlyation of glucose by hexokinase into glucose-6-phosphate (G6P)

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10
Q

% glucose metabolism by glycolysis? by TCA cycle? %ATP produced aerobically?

A

78%. 3% (low oxygen tension in lens), but due to high efficiency still produces 25% of ATP

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11
Q

percentage of G6P metabolized in lens by HMP shunt pathway? more or less than other tissues?

A

5%, which is proportionally higher than other tissues

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12
Q

metabolic pathway responsible for diabetic cataract?

A

sorbitol

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13
Q

affect of hyperbaric oxygen on lens?

A

nuclear cataract formation

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14
Q

relative proportions of sodium, potassium, water, chloride, and amino acids in lens

A

potassium and amino acids high

sodium, chloride, and water low (due to Na+/K+ pump)

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15
Q

embryologic origin of lens

A

surface ectoderm

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16
Q

name the first three steps of lens development in order

A

lens placode, lens pit, lens vesicle

17
Q

orientation of Y sutures in lens?

A

upright Y anteriorly, inverted Y posteriorly

18
Q

where do zonules originate?

A

secreted by ciliary epithelium

19
Q

Laterality, relative commonality, and associated syndromes with anterior and posterior lenticonus

A

Anterior: bilateral, less common, Alport syndrome
Posterior: unilateral, more common, Lowe syndrome

20
Q

most common location of Mittendorf dot

A

inferonasal

21
Q

when does the lens vesicle normally separate from the surface ectoderm

A

33 weeks gestation

22
Q

Microspherophakia:

  1. refractive state
    • stubby fingers, small stature, reduce joint mobility (and inheritance)
  3. feared complication
  4. medications contraindicated in (3)
  5. medical and procedural treatment of (3)
A
  1. highly myopic
  2. Weill-Marchesani, AR
  3. pupillary block glaucoma
  4. miotics (increase pupillary block)
  5. cycloplegics (decrease A-P lens diameter) + LPI
23
Q

Aniridia:

  1. laterality
  2. % sporadic
  3. associated gene
  4. associated findings
  5. workup for sporadic?
A
  1. almost always bilateral
  2. 1/3 sporadic
  3. PAX6
  4. epitheliopathy from decreased limbal stem cells, angle closure glaucoma, optic nerve and foveal hypolasia
  5. abdominal u/s to eval for Wilms tumor (WAGR = Wilms tumor, aniridia, GU anomalies, mental retardation)
24
Q

basic causes of congenital cataracts and relative frequency

A

1/3 isolated inherited trait, 1/3 associated with systemic syndromes, 1/3 unknown

25
Q

most common type of congenital cataract?

A

lamellar

26
Q

anatomy of lamellar cataract

A

clear center, opaque spherical shell, clear surrounding of shell

27
Q

small bluish cortical lens opacities in newborn? management?

A

Cerulean cataract; observe as are usually not visually significant

28
Q

Marfan:

  1. inheritance and gene product
  2. location of lens subluxation
  3. management of lens subluxation
A
  1. AD, fibrillin
  2. usually superotemporal
  3. refractive correction first, as surgery os complicated by zonular dehiscence, vitreous loss, and RD
29
Q

Homocystinuria:

  1. inheritance
  2. diagnositc lab findings
  3. location of lens subluxation
  4. treatment
A
  1. AR
  2. high homocystine, high methionine
  3. inferonasal
  4. cysteine and B6 supplements; methionine restriction
30
Q

inheritance of ectopia lentis et pupillae? location of lens subluxation?

A

AR; 180 degrees away from pupillary displacement

Lens and Cataract (3 decks)

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