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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
chronic hyperbaric O2
early NS cataracts (myopic shift)
26
systemic assoc/w/PSC
steroid gtts RP NF2 brachytherapy
27
rubella cataract
pearly nuclear white opacifications & retention of cell nuclei within the lens fibers
28
Chlorpromazine and thioridazine cause what types of cataracts?
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 ```
29
Argon laser to epi downgrowth does what to membrane?
500 um spot size Turns MEMBRANE white normal iris turns brown with laser
30
PCO rate of formation for different IOLs
acrylic (lowest PCO) < silicone < PMMA
31
Soemmering ring
aka raing cataract | residual lens epithelial cells may proliferate in the closed space b/t anterior and posterior capsules
32
Elschnig pearls
lens epithelial cells proliferate in large spherical aggregates
33
PCO
cells migrate across the posterior capsule and cause contraction of a secreted collagen matrix --> capsular wrinkling
34
Rx dysphotopsias
Rx: - pupillary constrict - Pt to wear spectacles with thicker frames - reverse optic capture - piggyback lens - nasal anterior capsule removal with YAG
35
Prevent dysphotopsias
- 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
Most metabolically active cells in the lens?
anterior lens epithelial cells posterior lens epithelial cells lose all their organelles and become the embryonic nucleus
37
Where is the lens ATPase located and what does it pump?
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
primary breakdown pathway of glucose for the lens
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
Vergence of convex or concave mirror
Concave mirror = always positive vergence | Convex mirror = always negative vergence
40
What can affect the A-scan measurement for AL
``` 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
Above what hertz is considered ultrasonic?
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
cataracts s/p contusion injuries
Stellate cataracts located posteriorly with star-like configuration
43
Issues with multifocal IOLs
- 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
snowflake cataracts
bilateral cortical cataracts = Subcapsular multiple gray-white opacities Occurs in uncontrolled diabetes (sorbitol) & Down Syndrome
45
ectopia lentis et pupillae
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
LRIs vs. AKS
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
Arcuate incision vs Radial incision flattening
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
Coupling ratio
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
Peristaltic vacuum phacoemulsifaction
generate vacuum by having "rollers" circulating around fixed tubing. As rollers compress and move along the tubing, vacuum is created
50
Vacuum ris
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
Major molecule promoting reducing environment in lens
glutathione As reduced form of glutathione gets depleted, more disulfide bonds form which leads to increased protein aggregation/cross-linked
52
Anterior subcapsular cataract
Fibrous plaque between anterior lens capsule & anterior epithelial cells Vision usually good Caused by? Amiodarone, phenothiazines
53
Poterior subcapsular cataract
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
Oil droplet cataract
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
Oil droplet cataract
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
Sunflower cataract
Located in anterior lens capsule and subcapsular cortex Occurs in Wilsons disease Inheritance: AR Abnormal copper metabolism (high copper, low ceruloplasmin)
57
Christmas tree cataract (polychromatic)
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
Alport Syndrome
Inheritance? XR or AR (10%) Ocular findings? Anterior lenticonus Cataract Fleck retinopathy ``` Systemic findings? Renal failure (hematuria), deafness ```
59
Lowe oculocerebralrenal Syndrome
Inheritance? XR Ocular Findings? Congenital glaucoma Congenital cataracts Posterior lenticonus Systemic findings? Renal tubular acidosis, mental retardation
60
What are the types of phaco machine pumps?
Peristaltic - rapid rise with rollers, linear control of vacuum, best Venturi – nearly instant vacuum, dangerous Diaphragm - slow buildup in vacuum
61
When does IOP spike usually occur after phaco?
4 hours
62
Which viscoelastic agent raises IOP more?
Dispersive (Na hyaluronate) > Cohesive (Chondroitin sulfate)
63
When can IOL be placed in children?
Only after 2 years old
64
What is the disadvantage of silicone IOL in retinal surgery?
Droplet deposits causing poor view
65
Silicone oil causes what kind of shift?
Hyperopic if phakic/pseudophakic | Myopic if aphakic
66
How much toric IOL rotation can increase astigmatism?
30 degrees
67
Where to put sulcus IOL suture?
0.75mm behind limbus sulcus = 0.83mm V, 0.46mm H avoid 3:00 and 9:00 (long ciliary nerves)
68
Chalcosis
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
Siderosis Bulbi
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
Marfan syndrome
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
Homocystinuria
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
Cystinosis
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
Sulfite Oxidase Deficiency
Hemiplegia, athetosis Death at age 5 with brain damage Increased urine levels? sulfite
74
Hyperlysinemia
Lysine a-ketoglutarate reductase deficiency | Mental retardation w/ dislocated lenses
75
Weil-Marchesani
Short, stubby fingers Small lens diameter, large AP diameter High myopia
76
Microspherophakia
Miosis; poor dilation w/ mydriatic Rx: cycloplege --> taughtens zonules.

Cornea/Refractive/Lens (7 decks)

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