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Cornea/Refractive/Lens > Lens > Flashcards

Lens Flashcards

1
Q

Sulcus lens instead of PCIOL

A

More anterior lens, shift focal point –> more myopic final refraction.

Normal Axial length (22-24) –> -1.00 diopters.

Longer eyes: less myopic shift for sulcus IOL

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2
Q

Membranous cataract

A

Membranous cataracts: lens proteins resorbed and anterior/posterior capsule fuse

Associated with 
Lowe syndrome
Hallerman-Strieff syndrome
microphthalmos
congenital rubella infection
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3
Q

Ectopia lentis

A 
sulfite oxidase deficiency (serious systemic abnml)
and others...
WATCH HIM SEE
Weil Marchesani
Aniridia
Trauma
Congenital glaucoma
Homocystinuria

Hereditary ectopia lentis
Iris coloboma
Marfans

Sulfite oxidase def
Ectropion uveae
Ehler Danlos)

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4
Q

Pump-leak theory

A

sodium flows IN through the BACK of the lens with the concentration gradient

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5
Q

Lens coloboma

A

often associated with cortical lens opacification

Wedge-shaped defect OR indentation of lens periphery that occurs as an isolated anomaly OR is 2/2 LACK OF CILIARY BODY or zonular development
typically located inferiorly and may be assoc/w/colobomas of the uvea

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6
Q

leading cause of preventable blindness

A

cataracts

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7
Q

Normal aging human crystalline lens with age becomes… (more/less) refracting power. (Flatter/curved) shape

A

Increasingly curved shape, somewhat offset by DECREASE in index of refraction 2/2 INCREASED presence of insoluble protein particles

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8
Q

Upon contraction of ciliary muscle… what happens?

A

Ciliary muscle contracts, diameter of muscle ring is reduced,
RELAXED tension on zonular fibers, lens becomes more SPHERICAL.

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9
Q

Clear corneal incisions assoc/w/

A
  • more susceptible to wound burn
  • more difficult to construct
  • less likely to be watertight
  • HIGHER incidence of endophthalmitis
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10
Q

Occlusion of phaco tip increases or decreases risk of incision burns?

A

occlusion of phaco tip reduces/interrupts fluid excavation through the phaco handpiece. This leads to an increased buildup of heat within the handpiece and transfer of thermal energy to the incision.

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11
Q

High aspiration flow rate and vacuum levels increases or decreases risk of incision burns?

A

decreases risk of incision burns

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12
Q

posterior infusion syndrome

A

Rare
Most likely to occur during hydrodissection, when fluid is forcefully injected into the capsular bag.

The fluid infused into the AC may be misdirected into the vitreous cavity, –> INCREASE in the vitreous volume, with subsequent forward displacement of the lens and shallowing of the anterior chamber. The fluid may accumulate in the retrolenticular space or dissect posteriorly along the vitreoretinal interface.

A shallow AC may indicate loss of integrity of the capsular bag, damaged zonular fibers, or misplacement of the irrigating tip.
Rx:
IV mannitol OR
19 g needle through the pars plana into the retrolenticular space and gently aspirate to try to remove the fluid and deepen the AC OR
PPV

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13
Q

Children -cataract

A

s/p blunt or penetrating trauma in a child, fibrin can be deposited on the anterior lens capsule that mimics the appearance of cataract

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14
Q

cataract assoc/w/acute trauma

A

best to do phacoemulsification through a small limbal incision - allows removal of any cataract assoc/w/acute trauma

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15
Q

Floppy iris from alpha1A antagonists for BPH mechanism

A

2/2 competitive binding to the post-synaptic nerve endings of the iris dilator

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16
Q

Major intrinsic protein

A

protein correlated with elongation of the lens fiber cell.

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17
Q

Lens cortex vs nucleus age

A

nucleus: birth -20 yo
Cortex: 20 yo+

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18
Q

Pathophysiology of diabetic cataracts

A

Sorbital pathway

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19
Q

YAG lens is what type of lens? What does it do to the depth of field?

A 
YAG lens: high plus lens
increases magnification (therefore reduces gross focus errors and pitting of the lens)
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20
Q

TASS

A

Toxic Anterior Segment Syndrome: sterile inflammatory rxn 2/2 contaminants injected into eye or incorrect pH
acutely post-op: 12-24 hrs (CONFINED to AC)

acute endophthalmitis (2-7 days)

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21
Q

Risks for cataract development

A

smoking African-American woman

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22
Q

wrong configuration of 3 piece IOL does what to refractive error?

A

Correct inverted S: IOL slightly posterior to haptics normally (so when in sulcus optic is AWAY from iris)

S configuration: patient will be slightly myopic

Single piece lenses generally not vaulted and when placed backwards do not generally affect the pt’s final refraction

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23
Q

Metabolically active cells of the crystalline lens found…

A

germinative zone = PRE-equatorial zone of the lens (single layer of cuboidal epithelial cells)

lens equator = begin differentiating into lens fibers

bow region (POST-equatorial zone) = complete differentiation into fibers

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24
Q

Homocystinuria

A

tall, 50% MR
inferonasal dislocated lens
thromboembolic events w/general anethesia

Diet restrict to Rx: LOW methionine, HIGH cysteine
+/- vitamin B6

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25
Q

chronic hyperbaric O2

A

early NS cataracts (myopic shift)

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26
Q

systemic assoc/w/PSC

A

steroid gtts
RP
NF2
brachytherapy

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27
Q

rubella cataract

A

pearly nuclear white opacifications & retention of cell nuclei within the lens fibers

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28
Q

Chlorpromazine and thioridazine cause what types of cataracts?

A

they are both phenothiazines. From Aqueous, absorb onto posterior K and ANTERIOR lens capsule = anterior capsule pigmentation

Chlorpromazine = rarely causes damage to retina
Thiordazine = severe retinopathy with high doses.  Initially = RPE stippling in posterior pole --> RPE loss
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29
Q

Argon laser to epi downgrowth does what to membrane?

A

500 um spot size
Turns MEMBRANE white
normal iris turns brown with laser

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30
Q

PCO rate of formation for different IOLs

A

acrylic (lowest PCO) < silicone < PMMA

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31
Q

Soemmering ring

A

aka raing cataract

residual lens epithelial cells may proliferate in the closed space b/t anterior and posterior capsules

32
Q

Elschnig pearls

A

lens epithelial cells proliferate in large spherical aggregates

33
Q

PCO

A

cells migrate across the posterior capsule and cause contraction of a secreted collagen matrix –> capsular wrinkling

34
Q

Rx dysphotopsias

A

Rx:

  • pupillary constrict
  • Pt to wear spectacles with thicker frames
  • reverse optic capture
  • piggyback lens
  • nasal anterior capsule removal with YAG
35
Q

Prevent dysphotopsias

A
  • make sure IOL well centered
  • optic haptic jxn @ 3:00 and 9:00
  • ensure capsulorrhexis rim overlaps the lens edge
  • using lower index lens w/rounded edge design
36
Q

Most metabolically active cells in the lens?

A

anterior lens epithelial cells

posterior lens epithelial cells lose all their organelles and become the embryonic nucleus

37
Q

Where is the lens ATPase located and what does it pump?

A

located on the ANTERIOR epithelial cells

Pumps K+ INTO lens
Pumps Na+ out of the lens

Mnemonic: Think of lens as getting yellower as you get older (bananas = yellow = high in K+)

38
Q

primary breakdown pathway of glucose for the lens

A

78% of glucose in the lens = anaerobic glcyosis
5% - HMP shunt

sorbital pathway minimally activated. Only activated when excess of glucose (sorbital gets trapped and creates an osmotic gradient for water to enter the lens)

39
Q

Vergence of convex or concave mirror

A

Concave mirror = always positive vergence

Convex mirror = always negative vergence

40
Q

What can affect the A-scan measurement for AL

A 
Eye filled with oil or gas
Posterior staphylomas (peripapillary region) = adj but not centered on the macula.  Gives false impression that AL is LONGER than the true axial length --> falsely weak lens = hyperopic surprise.
41
Q

Above what hertz is considered ultrasonic?

A

20,000 (20K)
Phacoemulsification handpieces generally oscillate between 27,000 and 60,000 Hertz

Dx ophthalmic U/S performed in the range of 8-15 MHz (8-15 million cycles per second)

42
Q

cataracts s/p contusion injuries

A

Stellate cataracts located posteriorly with star-like configuration

43
Q

Issues with multifocal IOLs

A
  • decreased contrast sensitivity
  • Myopic LASIK/PRK increase the amount of positive spherical aberration
  • increase in positive spherical aberration also results in decreased contrast sensitivity

-IOL power calculations are least accurate for post-myopic LASIK/PRK and post-RK eyes

Therefore, hyperopic LASIK/PRK pt would be happiest person.

44
Q

snowflake cataracts

A

bilateral cortical cataracts = Subcapsular multiple gray-white opacities

Occurs in uncontrolled diabetes (sorbitol) & Down Syndrome

45
Q

ectopia lentis et pupillae

A

AR
classic: slit like configuration that is displaced in the OPPOSITE direction as the subluxed lens

usually:
Iris displacement inferotemporally OU
Lens dislocation superonasally OU

46
Q

LRIs vs. AKS

A

Both parallel to the limbus & both done in the steep meridian to reduce astigmatism

but LRIs are performed VERY CLOSE to the limbus
vs
AKs performed at least 1 mm toward the apex of the cornea

47
Q

Arcuate incision vs Radial incision flattening

A

Arcuate incisions: flattening in the meridian of the incision and STEEPING in the meridian 90 degrees away (coupling). Pt maintains spherical equivalent.

Radial incisions cause flattening in BOTH the meridian of the incision and 90 degrees away

48
Q

Coupling ratio

A

Amount of flattening induced by an incision
divided by the amount of steepening induced 90 degrees away

Transverse incisions = straight incisions parallel to the limbus
Have coupling ratio > 1 which means they induce a hyperopic ratio

49
Q

Peristaltic vacuum phacoemulsifaction

A

generate vacuum by having “rollers” circulating around fixed tubing. As rollers compress and move along the tubing, vacuum is created

50
Q

Vacuum ris

A

2/2 roller speed b/c vacuum created by the speed of the rollers turning over in the tubing (peristaltic system) as long as tip occluded
rise time is dependent on the aspiration flow rate

51
Q

Major molecule promoting reducing environment in lens

A

glutathione
As reduced form of glutathione gets depleted, more disulfide bonds form which leads to increased protein aggregation/cross-linked

52
Q

Anterior subcapsular cataract

A

Fibrous plaque between anterior lens capsule & anterior epithelial cells
Vision usually good

Caused by?
Amiodarone, phenothiazines

53
Q

Poterior subcapsular cataract

A

Posterior migration of enlarged, swollen lens epithelial cells
Vision usually bad (with glare)

Caused by?
Steroids
Inflammation
Trauma
Diabetes, RP, NF-2
Radiation
Remnant of tunica vasculosa lentis
54
Q

Oil droplet cataract

A

Occurs in Galactosemia (Inheritance: AR)
Symptoms: malnutrition, hepatomegaly, jaundice, mental retardation
Fatal if not recognized

Treatment: eliminate milk from diet (cataract may be reversed)

55
Q

Oil droplet cataract

A

Occurs in Galactosemia (Inheritance: AR)
Symptoms: malnutrition, hepatomegaly, jaundice, mental retardation
Fatal if not recognized
Treatment: eliminate milk from diet (cataract may be reversed)

56
Q

Sunflower cataract

A

Located in anterior lens capsule and subcapsular cortex
Occurs in Wilsons disease
Inheritance: AR

Abnormal copper metabolism (high copper, low ceruloplasmin)

57
Q

Christmas tree cataract (polychromatic)

A

Occurs in Myotonic Dystrophy and Hypoparathyroidism
(Inheritance: AD)

Symptoms: Delayed relaxation of muscles, ptosis, frontal balding, wasting of temporalis and masseter muscles (“hatchet face”), CPEO

58
Q

Alport Syndrome

A

Inheritance? XR or AR (10%)

Ocular findings?
Anterior lenticonus
Cataract
Fleck retinopathy

Systemic findings?
Renal failure (hematuria), deafness
59
Q

Lowe oculocerebralrenal Syndrome

A

Inheritance? XR

Ocular Findings?
Congenital glaucoma
Congenital cataracts
Posterior lenticonus

Systemic findings?
Renal tubular acidosis, mental retardation

60
Q

What are the types of phaco machine pumps?

A

Peristaltic - rapid rise with rollers, linear control of vacuum, best
Venturi – nearly instant vacuum, dangerous
Diaphragm - slow buildup in vacuum

61
Q

When does IOP spike usually occur after phaco?

A

4 hours

62
Q

Which viscoelastic agent raises IOP more?

A

Dispersive (Na hyaluronate) > Cohesive (Chondroitin sulfate)

63
Q

When can IOL be placed in children?

A

Only after 2 years old

64
Q

What is the disadvantage of silicone IOL in retinal surgery?

A

Droplet deposits causing poor view

65
Q

Silicone oil causes what kind of shift?

A

Hyperopic if phakic/pseudophakic

Myopic if aphakic

66
Q

How much toric IOL rotation can increase astigmatism?

A

30 degrees

67
Q

Where to put sulcus IOL suture?

A

0.75mm behind limbus
sulcus = 0.83mm V, 0.46mm H
avoid 3:00 and 9:00 (long ciliary nerves)

68
Q

Chalcosis

A

May be caused by brass or bronze

Ocular signs?
Kayser-Fleischer ring (Cu in Descemet’s, can be used to monitor therapy)
Green discoloration of iris
Sunflower cataract

69
Q

Siderosis Bulbi

A

Fe deposits in epithelial tissues; damage to photoreceptors + RPE

ERG?
Decreased B-wave

Ocular signs?
Iris heterochromia, cataract, rust color to cornea, glaucoma, anisocoria

70
Q

Marfan syndrome

A

Inheritance / Gene?
AD (fibrillin; Ch 15)

Ocular findings?
Lens dislocation (superotemporal)
Myopia, retinal detachment

Systemic findings?
Tall, long limbs, hyperflexible joints

Life threatening problem?
Dilation of aorta (risk of dissection)

71
Q

Homocystinuria

A

Inheritance / Gene?
AR (Cystathionine β-synthase)

Elevated levels?
Homocystine and methionine

Ocular findings?
Lens dislocation (inferonasal)

Systemic findings?
Tall, osteoporosis, chest deformities
Seziures, mental retardation
Abnormalities develop after birth

Life threatening problem?
Thromboembolism esp. under GA

Treatment?
Low methionine, high cysteine diet

72
Q

Cystinosis

A

Cystine crystals in anterior K stroma

3 Forms?
1) Infantile (AR, dwarfism, rickets, renal failure / Fanconi, death before puberty)
2) Adolescent (AR, similar but less severe),
3) Adult (?inheritance, asymptomatic)
Retinopathy only in infantile

Treatment?
Oral & topical cysteamine to stop crystals

73
Q

Sulfite Oxidase Deficiency

A

Hemiplegia, athetosis
Death at age 5 with brain damage
Increased urine levels?
sulfite

74
Q

Hyperlysinemia

A

Lysine a-ketoglutarate reductase deficiency

Mental retardation w/ dislocated lenses

75
Q

Weil-Marchesani

A

Short, stubby fingers
Small lens diameter, large AP diameter
High myopia

76
Q

Microspherophakia

A

Miosis; poor dilation w/ mydriatic

Rx: cycloplege –> taughtens zonules.

Cornea/Refractive/Lens (7 decks)

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