11 - lens and cataract

7/23/2019 11 - Lens and Cataract

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11 - Lens and Cataract

1. Which of the following is not a function of the crystalline lens?

a. maintaining clarity

b. providing accommodationc. metabolizing toxins

d. refracting light

2. What is a normal change in the normal human crystalline lens as it ages?

a. It develops an increasingly curved shape, resulting in more refractive power.

b. It develops an increasingly flatter shape, resulting in less refractive power.c. It undergoes an increase in the index of refraction as a result of the decreasing

presence of insoluble protein particles.

d. It undergoes a decrease in the index of refraction as a result of the decreasingpresence of insoluble protein particles.

3. What occurs during terminal differentiation?

a. Lens epithelial cells elongate into lens fibers.

b. The mass of cellular proteins is decreased.c. Glycolysis assumes a lesser role in metabolism.

d. Cell organelles increase their metabolic activity.

4. What is the first presenting sign of Marfan syndrome in the eye?

a. pupillary block glaucoma

b. monocular diplopiac. the need for aphakic correction

d. inferonasal subluxation

5. Why are glutathione and vitamins A and C present in the anterior

chamber?

a. to adjust the pH and act as a bufferb. to protect the corneal endothelium

c. to scavenge free radicalsd. to induce DNA damage


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6. What occurs when the ciliary muscle contracts?

a. The diameter of the muscle ring is reduced, thereby increasing tension on thezonular fibers, allowing the lens to become more spherical.

b. The diameter of the muscle ring is increased, thereby increasing tension on the

zonular fibers, allowing the lens to become more spherical.c. The diameter of the muscle ring is reduced, thereby relaxing tension on the

zonular fibers, allowing the lens to become more spherical.d. The diameter of the muscle ring is increased, thereby relaxing tension on the

zonular fibers, allowing the lens to become more spherical.

7. The Y-sutures seen in the adult lens are the result of which of the following?

a. the junction of the adult nucleus with the surrounding cortexb. scarring from the tunica vasculosa lentis

c. the elaboration of the adult nucleus around the fetal nucleus

d. fusion of the embryonic cells within the fetal nucleus

8. Which of the following systemic diseases is not associated with ectopia

lentis?

a. homocystinuria

b. Ehlers-Danlos syndromec. Marfan syndrome

d. myotonic dystrophy

9. What is a typical characteristic of a lens coloboma?

a. usually associated with previous lens traumab. typically located superiorly

c. typically associated with normal zonular attachmentsd. often associated with cortical lens opacification

10. Which of the following is seen in Peters anomaly?

a. treatment with rigid gas-permeable contact lenses

b. defects in the corneal endothelium and Descemet membranec. identification ofPAX6 mutation in all cases

d. bilaterality in 10% of cases


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11. "Oil droplet;' crystalline, and "snowflake" cataracts are characteristic of

which diseases, respectively?

a. diabetes, myotonic dystrophy, galactosemia

b. myotonic dystrophy, galactosemia, diabetes

c. galactosemia, diabetes, myotonic dystrophyd. galactosemia, myotonic dystrophy, diabetes

12. A patient presents with a mature lens and secondary glaucoma without

evidence of pupillary block. What is the most likely diagnosis?

a. phacomorphic glaucoma

b. phacolytic glaucoma

c. phacoantigenic uveitisd. lens particle glaucoma

13. Which change is most characteristic of exfoliation syndrome?a. exfoliative material confined to the lens capsuleb. strong zonular fibers

c. increased pigmentation of the trabecular meshwork

d. hypotony

14. A 65-year-old patient presents with a gradual reduction in vision 1 year

after Vitrectomy to repair a retinal detachment. What is the most likely

explanation?

a. Redetachment of the retina

b. posterior subcapsular cataract from intensive steroid therapyc. nuclear cataract after vitrectomy to repair the retinal detachment

d. phacoantigenic uveitis from leakage of lens protein

15. Which of the following is true regarding the epidemiology of cataracts?

a. They are more prevalent in persons younger than 65 years.b. They are more prevalent in men.

c. They occur only as a consequence of age.d. They are the leading cause of reversible blindness.

16. In the developing world, which of the following could apply to a patient

who develops a visually significant cataract?

a. An additional person may be removed from the workforce for care of the patient.

b. The patient must receive prompt attention to have the cataract removed.c. The patient is at lower risk for falls.

d. The patient is older than 65 years.


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17. What did the Beaver Dam Eye Study determine regarding visually

significant cataracts?

a. They occur earlier in men than in women.

b. They interfere with vision only after patients are older than 75 years.

c. They are more likely to be cortical than nuclear.d. The incidence of visually significant cataract increases slowly from age 54 to 75.

18. If the best -corrected visual acuity for a patient with cataract is 20/100, a

surgeon would be most likely to recommend surgery if

a. pinhole acuity is also 20/100

b. potential acuity meter (PAM) acuity is 20/25

c. laser interferometry reveals that the patient has no ability to recognize theorientation of the diffraction pattern

d. a Maddox rod test shows multiple interruptions in the red light streak

19. If a patient has a dense white cataract and the posterior pole is not visible,

which of the following would be most helpful for the clinician in deciding

whether to perform surgery?

a. Specular microscopy

b. B-scan ultrasonographyc. laser interferometry

d. Maddox rod test

20. If a patient is found to have a best-corrected visual acuity of20/40 in each

eye but reports that vision is adequate for his needs, which factor would cause

the ophthalmologist to consider cataract surgery?

a. The level of lens opacity equals the level of vision loss.b. The patient has no medical problems that would contraindicate surgery.

c. The ophthalmologist is unable to see the patient's retina well enough to evaluate

it.d. The patient would be able to perform his activities of daily living more easily

with better vision.

21 . In a highly myopic patient, which of the following best describes anappropriate step in decreasing operative risks?

a. raising the height of the irrigating bottle

b. maintaining a loose incision to allow for increased leakage

c. carefully examining the peripheral retina preoperativelyd. warning the patient of blurred vision from postoperative anisometropia


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22. Which of the following is a source of potential complications during

cataract surgery in a uveitis patient?

a. shallow anterior chamber

b. zonular laxity

c. endogenous endophthalmitisd. phacolytic glaucoma

23. Which one of the following steps would reduce the operative risks of

surgery for a mature, white cataract?

a. placing a small initial incision in the anterior capsule and injecting sufficient

viscoelastic into the lens to expel liquid cortex prior to completing the

capsulorrhexisb. steepening the dome of the anterior capsule by removing the viscoelastic after

the initial capsule puncture

c. staining the capsule with trypan blue or indocyanine green dyed. creating numerous radial relaxing incisions in the anterior capsule with longVannas scissors

24. A patient with visually significant cataract is found to dilate poorly on

preoperative examination.

Which of the following is the most likely cause of this poor dilation?

a. pigment dispersion syndromeb. atopic dermatitis

c. exfoliation syndrome

d. hypertension

25. Which of the following would be the best initial treatment of a

postoperative shallow anterior chamber caused by ciliary block glaucoma?

a. miotics and peripheral iridotomy

b. cycloplegia and aqueous suppressantsc. emergent vitrectomy

d. cyclophotocoagulation

26. In operating on a patient with exfoliation syndrome, a surgeon chooses tomake a large anterior continuous curvilinear capsulorrhexis (CCC).

What postoperative complication will most likely be avoided?

a. opacification of the posterior lens capsule

b. postoperative phimosis of the anterior capsulec. postoperative spike in intraocular pressure

d. glare and halos


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27. In cataract surgery in which the posterior lens capsule ruptures and

vitreous presents in the anterior chamber, when is anterior Vitrectomy

complete?

a. when vitreous is removed from the wound

b. when a posterior chamber intraocular lens (IOL) can be placedc. when the surgeon can see the retina

d. when vitreous is removed anterior to the posterior lens capsule


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Answers

1. c.Lens cells have no mechanism for metabolizing toxins. The lens remains clear

because the lens fibers contain no nuclei or organelles that would scatter light. The

lens refracts light because the relative density of the lens is greater than that of thefluids (aqueous and vitreous) surrounding it. The lens, until the onset of

presbyopia, remains flexible to provide accommodation in response to the tensionplaced on the capsule from the ciliary muscle and zonular fibers.

2. a. With age, the human lens develops an increasingly curved shape, which

results in more refractive power. This change may be accompanied by- and

sometimes offset by-a decrease in the index of refraction of the lens, probablyresulting from an increase in water insoluble proteins.

3. a.Terminal differentiation involves elongation of the lens epithelial cells intolens fibers.This change is associated with a tremendous increase in the mass of cellular

proteins in each cell. The cells lose organelles, including nuclei, mitochondria, and

ribosomes.

The loss of cell organelles is optically advantageous; however, the cells thenbecome more dependent on glycolysis for energy production and less active

metabolically.

4. b.Monocular diplopia occurs when the lens is partially dislocated, and light can

pass both through and around the edge of the lens. Pupillary block glaucoma fromanterior dislocation of the lens is a rare event. Aphakic correction is required when

the lens is totally subluxed into the vitreous. When the lens subluxates, it usuallydoes so superotemporally.

5. c.Glutathione and vitamins A and C are powerful free radical scavengers. Theyhave no effect on the pH or the corneal endothelium. They actually protect DNA

from being damaged by free radicals.

6. c.The ciliary muscle is a ring, but upon contraction it does not have the effectthat one would intuitively expect of a sphincter. When it contracts, the diameter of

the muscle ring is reduced, thereby relaxing tension on the zonular fibers, allowing

the lens to become more spherical.


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7. d. The Y-sutures represent the edges of the secondary lens fibers of the fetal

nucleus. The anterior Y is erect and the posterior one is inverted. They can be seenin the center of the adult nucleus in a clear lens. The junction of the adult nucleus

and surrounding cortex is invisible until the nucleus develops sclerosis. The tunica

vasculosa lentis surrounds the lens as it grows. The Y-sutures are within the fetalnucleus, not around it.

8. d. Myotonic dystrophy is not associated with ectopia lentis.

9. d. A lens coloboma is a wedge-shaped defect or indentation of the lens periphery

that occurs as an isolated anomaly or is secondary to the lack of ciliary body or

zonular development.Cortical lens opacification or thickening of the lens capsule may appear adjacent

to the defect.

Lens colobomas are typically located inferiorly and may be associated withcolobomas of the uvea.

10. b. Peters anomaly is bilateral in 80% of cases. PAX6 mutations occur in

patients with Peters anomaly, but many cases are associated with mutations in

other alleles. Treatment usually involves sector iridectomy and/or penetratingkeratoplasty as well as management of coexisting glaucoma. Rigid gas-permeable

contact lenses would be ineffective since they do not address the effects of thecentral corneal opacity.

11. d.Galactosemia produces an "oil droplet" cataract that appears within the firstfew weeks of life. Untreated, galactosemia is rapidly fatal. Crystalline cataracts in

myotonic dystrophy develop a Christmas tree-appearing cortical cataract as well asposterior subcapsular changes that will lead to complete opacification. The acute

cataract of uncontrolled diabetes has a snowflake appearance in the anterior and

posterior subcapsular region.

12. b.Phacolytic glaucoma occurs when denatured lens protein leaks through anintact but permeable capsule. In phacomorphic glaucoma, the mature lens causes

pupillary block and secondary angle closure. In phacoantigenic uveitis, leaking oflens protein produces a granulomatous inflammatory reaction. Lens particle

glaucoma is associated with penetrating lens injury or surgery.


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13. c. Increased pigmentation of the trabeculum and reduced outflow occur

frequently in exfoliation syndrome. Exfoliative material has been found in manybodily organs as well as on the iris and corneal endothelium. Intraocular pressure

may rise as a result of the obstruction of the trabecular meshwork by the exfoliative

material.

14. c.Nuclear cataract is common in patients older than 50 years if vitrectomy hasbeen used to repair a retinal detachment. Redetachment of the retina is an acute

phenomenon and unlikely 1 year after repair. Steroid therapy after retinal

detachment is usually brief and unlikely to cause nuclear cataract. Phacoantigenic

uveitis produces an inflammatory reaction and is extremely rare.

15. d. Census data confirm that cataracts are the leading cause of reversible

blindness. Cataracts increase in prevalence with increasing age and are a leading

cause of blindness worldwide. They can occur as a congenital condition or as aresult of trauma, metabolic diseases, or medications. Major epidemiologic studiesconfirm an increased prevalence in women.

16. a. When 1 individual is incapacitated by blindness, the care that is required to

provide for that person may remove the caregiver from the workforce as well. Theratio of surgeries to population in the developing world is as low as 50 per million.

Reduced vision is a primary factor in decreasing mobility and increasing the risk offalls. Cataracts form earlier in life in populations in which nutrition is not optimal.

17. d.Cataracts begin to interfere with vision in persons aged 43-54 years, and,from that age range, the incidence increases 13-fold in those aged 75 years or older.

The overall incidence of cataract is greater in women than in men. Nuclearcataracts are more frequent than cortical cataracts at all ages.

18. b. The potential acuity meter (PAM) projects the equivalent of a Snellen visualacuity chart into the eye, specifically through clear spaces in the lens, by means of

a beam of light to allow an estimate of macular function. The pinhole testapproximates the PAM; a reduced acuity would signal other ocular conditions that

cataract surgery might not improve.Laser interferometry usually is beneficial in denser cataracts: the patient's failure to

discern the orientation of the diffraction pattern would indicate reduced visual

potential.

The patient's inability to see a continuous red line on a Maddox rod test wouldsuggest areas of decreased retinal sensitivity in the macula.


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19. b. B-scan ultrasonography is indicated to evaluate for occult tumors, retinal

detachment, and posterior staphyloma or other posterior pathology that could affectthe visual outcome.

Laser interferometry and Maddox rod testing are not reliable with such a dense

cataract. Specular microscopy would be indicated only if signs of cornealendothelial dysfunction were present.

20. c. The only consideration that would prompt the surgeon to consider operating

would be the inability to evaluate the patient's retina. This would be the case even if

the cataract explained the vision loss and the patient appeared well enough to

undergo surgery. If the patient reports that his vision is adequate for his needs,

surgery should be postponed.

21. c. Careful examination of the retinal periphery may reveal the presence of

lattice degeneration, retinal holes, and other abnormalities that warrantconsideration of preoperative treatment and/or diligent postoperative evaluation.Lowering the height of the irrigating bottle produces less stress on the zonular

fibers and reduces the risk of posterior capsule tears. All incisions should be

carefully closed to reduce the risk of infection. Myopic patients do need to be

cautioned about anisometropia, and intolerable imbalances may promptconsideration of second-eye surgery.

22. b.Chronic ciliary body inflammation at the zonular fibers may lead to zonular

laxity similar to that seen in exfoliation syndrome. The technical aspects of cataract

surgery can be more difficult in patients with uveitis. There may be limited accessto the lens because of posterior synechiae, a pupillary membrane, pupillary

sphincter fibrosis, and a floppy iris. Lysing synechiae, excising pupillarymembranes, and using pupil expanders and viscoelastic can counteract and

overcome the effects of an abnormal iris. Rupture of the capsulorrhexis with

extension to the zonular fibers can further complicate the procedure, and capsulardyes may be necessary to maintain a continuous capsular tear during the rhexis.

23. c.When cataract surgery is performed on a patient with a white lens, there is

little or no red reflection. This makes it difficult to perform a circularcapsulorrhexis. Utilizing a capsular dye improves visualization of the capsule,

facilitating the creation of an anterior capsulorrhexis. The other methods described

increase the operative risks. Steepening the dome of the anterior capsule increases

the propensity for radial anterior capsule tearing and therefore should be avoided.Maximally filling the anterior chamber with viscoelastic during the capsulorrhexis

can reduce leakage of white lens material into the anterior chamber, improving the


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view of the anterior capsule. Creation of numerous radial relaxing incisions is a

method used when the initial capsulorrhexis is unsuccessful; it would not be theprimary step in creation of a capsulorrhexis. A small puncture in the anterior

capsule with injection of viscoelastic to expel liquid cortex prior to the completion

of the capsulorrhexis can be used initially but is not considered necessary with theadvent of capsular dyes.

24. c.Exfoliation syndrome is a common disorder associated with the deposition of

a fibrillo granular material on the anterior surface of the lens and elsewhere in the

anterior segment. With respect to cataract surgery, patients with this condition may

have zonular laxity, capsular fragility, and poor pupillary dilation.

25. b.Causes of a shallow chamber postoperatively include wound leak, pupillary

block, suprachoroidal effusion or hemorrhage, and ciliary block glaucoma with

aqueous misdirection into the vitreous cavity. If the cause is known to be ciliaryblock glaucoma, initia treatment with cycloplegia and aqueous suppressants mayrelieve the condition. Surgical disruption of the vitreous face by YAG laser or a

Vitrectomy may be necessary at a later time to permanently restore normal aqueous

circulation and anterior chamber depth if the initial treatment fails.

26. b.A large capsulorrhexis will reduce the risk of phimosis and increased tension

on the weakened zonular fibers of the patient, also reducing the risk of lateposterior dislocation of the intraocular lens. Opacification of the posterior lens

capsule is dependent not on the size of the capsulorrhexis but rather on the anterior

capsule overlapping the edge of the intraocular lens. Postoperative pressure spikesare not dependent on capsulorrhexis size, although they are more common in

patients with exfoliation. Glare and halos are also not caused by a large anteriorcapsulorrhexis.

27. d.Loss of vitreous is not a problem for the eye; vitreous traction is. The goal ofvitreous removal is to reduce the possibility of traction. The clinician may prevent

traction by removing enough vitreous to keep it away from the incision. Therefore,a Vitrectomy is not complete until all vitreous is removed anterior to the posterior

capsule. This ensures a lower risk of traction, and it is also the best way to decreasethe risk of postoperative cystoid macular edema (CME).

11 - lens and cataract

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