Lens and cataract

 

1. The following are true about cataract:

a. it is the most common cause of blindness in the world

b. nuclear sclerosis reduces the distant vision more than
    near

c. posterior subcapsular cataract is more likely to cause
    problem with distant vision than near

d. more females than males have cataract surgery

e. outdoor workers are more likely to develop cataract
    than indoor workers
 

answer1.    a.T    b.T    c.F    d.T    e.FNuclear sclerosis causes myopia and therefore reduces the distant vision more than near.Posterior subcapsular cataract becomes more visually significant when the pupil constricts as during accommodation or near vision.Females live longer than males and therefore have higher rate cataract surgeryAlthough UV light has been implicated in cataractogenesis, there is no firm studies to demonstrate that outdoor workers are more prone to cataract development than indoor workers.

2. True association include:

a. Wilson's disease - sun-flower cataract

b. myotonic dystrophy - Christmas tree cataract

c. amiodarone - anterior capsular cataract

d. Alport's syndrome - posterior lenticonus

e. Down's syndrome - cerulean (blue-dot) cataract
 

answer2.    a.T    b.T    c.T    d.F    e.TAlport's syndrome is associated with anterior lenticonus.Cerulean or blue-dot cataract contains multiple bluish white opacities within the cortex.

3. The following are true about microspherophakia:

a. it is associated with myopia

b. it can cause pupillary block glaucoma which should be
    treated with mydriatic

c. it is associated with short stature and stiff joints

d. anterior dislocation is a known complication

e. it can be an autosomal recessive disorder.
 

answer3.    a.T    b.T    c.T    d.T    e.TThe lens is round and has small diameter giving it a high converging power and therefore myopiaPupillary block may be exaggerated with miotic whereas mydriatic can relieve the block by tightening the zonules and therefore pull the lensbackwardIt is associated with Weill-Marchesani's syndrome which is an autosomal recessive disorder and has the features of short stature and stiff joints

4. The following metabolic disorders are associated with
     cataract:

a. hyperlysinemia

b. hypercalcemia

c. hypocalcemia

d. hypoglycaemia

e. uraemia

answer4.  a.F    b.F    c.T    d.T    e.FHyperlysinemia is associated with lens subluxation but not cataractHypocalcemia but not hypercalcemia is associated with cataractHypoglycaemia in utero is associated with cataract
 

5. Drug-induced cataract include:

a. phenothiazine

b. echothiopate

c. aspirin

d. lovastatin

e. systemic beta-blockers

answer5.    a.T    b.T    c.F    d.T    e.F

6. True statements about the ocular effects of congenital rubella
    include:
 

a. eye defect typically occurs with infection during the
    first trimester of pregnancy

b. lamellar cataract is the most common type of cataract
    seen in congenital rubella

c. viral particles usually remain in the lens particle long
    after birth

d. myopia is common

e. congenital rubella causes progressive chorioretinitis.

answer6.    a.T    b.F    c.T    d.F    e.FThe cataract seen in congenital rubella shows white nuclear opacities or total cataract.The affected eye is small with miotic pupil and shallow anterior chamberThere may be salt and pepper retinopathy which is non-progressive.

7. The following are true about blunt trauma on the lens:

a. Vossius ring is caused by the imprint of the pupillary
    pigment on the lens

b. Vossius ring causes decreased vision in the majority
     of patients

c. Vossius ring is a permanent sign

d. contusion cataract is usually rosette-shaped

e. contusion cataract typically involves the anterior cortex

answer7.    a.T    b.F    c.F    d.T    e.FVossius ring is usually visually insignificant and tend to disappear with time.Contusion cataract is usually stellate or rosette-shaped involving the axial posterior lens capsule

8. In congenital cataract:

a. patients with severe bilateral cataract should have the
    cataracts removed before three months of age

b. intraocular lens should be used

c. the posterior capsule is usually left intact

d. post-operative visual acuity is usually better in patients
    with unilateral cataract than bilateral cataract

e. visual prognosis is poor in patients who develop
    nystagmus

answer8.    a.T    b.F    c.F    d.F    e.TPatients with visual significant bilateral cataract should undergo extraction before fixation develop which is usually at 3 months of age. Nystagmus which develops after this age usually indicates poor visual prognosisThe use of intraocular lens is controversialThe posterior capsule is removed together with limited anterior vitrectomy as posterior capsule opacification is common if leftPost-operative visual acuity is usually poor in patients with unilateral cataract compared with those with bilateral cataract

9. With regard to the materials used in intraocular lens:

a. PMMA is the most common material used in making
    foldable lens

b. PMMA transmits a broader spectrum of light than
    natural lens

c. silicone is associated with increased capsular fibrosis

d. silicone lens tends to be thinner than PMMA for the
    same dioptre power

e. hydrogel lens has a lower tensile strength than PMMA

answer9.    a.F    b.T    c.T    d.F    e.TPMMA is rigid and has a high tensile strength. It is not suitable forfoldable lens.PMMA transmit a broad spectrum of light than human lens. Therefore, chromophore is incorporated to block ultra-violet light.Silicone lens is associated with increased capsular fibrosis. It also has a lower refractive index than PMMA and therefore a thicker lens is needed for the same dioptreBoth silicone and hydrogel have lower tensile strength than PMMA and are used to make foldable lenses.

10. Regarding eye drops used in cataract surgery:

a. flurbiprofen is used to dilate pupil

b. flurbiprofen prevents post-operative inflammation

c. phenylephrine stimulates the alpha receptors

d. phenylephrine should be avoided in patients on
    monoamine oxidase inhibitors

e. cyclopentolate acts on the constrictor muscle of the iris

answer10.    a.F    b.F    c.T    d.T    e.TFlurbiprofen is used to prevent miosis but does not dilate the pupilPhenylepherine can cause hypertensive crisis in patients taking monoamine oxidase inhibitorsCyclopentolate acts on the constrictor  muscle of the iris leading to dilatation.

11. Homocystinuria:

a. is an autosomal recessive condition

b. causes inferonasal subluxation of the lens

c. is associated with raised serum methionine

d. is associated with mental retardation

e. causes osteoporosis

answer11.    a.T    b.T    c.T    d.T    e.TWeakened zonules are thought to be caused by cystein deficiency.

12. The histological features of the following are true:

a. Elschnig pearls - proliferation of lens epithelium
    onto the posterior capsule

b. posterior subcapsular cataract - bladder cells

c. cortical cataract - morgagnian globules

d. glaucoflecken - Wedl cells

e. Soemmerring ring - sequestration of proliferating  lens
    fibres in the equatorial region of the capsule

answer12.    a.T    b.T    c.T    d.F    e.TWedl or bladder cells are caused by posterior migration of lens epithelial cells which swell along the posterior capsule giving rise to posterior subcapsular cataract.

13. In a 6 month old baby with bilateral cataract, urine test is
       useful in:

a. homocystinuria

b. galactosemia

c. Lowe's syndrome

d. abetalipoproteinemia

e. cystinosis

answer13.    a.F    b.T    c.T    d.F    e.FUrine test reveals protein and reducing agent in Lowe's syndrome and galactosemia respectively. Both conditions are associated with bilateral cataract

14. In galactosemia:

a. the condition is autosomal dominant

b. the most common form is caused by
    galatose-a-phosphate uridyl transferase deficiency

c. mental retardation is a feature in untreated cases

d. the cataracts usually assume oil droplet appearance

e. early cataracts are reversible with dietary restriction

answer14.    a.F    b.T    c.T    d.T    e.TAutosomal recessive.

15. Factors that can increase intravitreal pressure during
      phacoemulsification include:

a. excessive peribulbar anaesthesia

b. patient taking deep breadth

c. pressure from the speculum

d. choroidal haemorrhage

e. a high bottle height

answer15.    a.T    b.F    c.T    d.T    e.FIntravitreal pressure is increased when the patient is breadth holding.

16. With regard to viscoelastics:

a. they are cleared in an unmetabolised state by filtration
    through the trabecular meshwork

b. sodium hyaluronate has a higher pseudoplastic
    behaviour than chondroitin sulphate

c. they are toxic to the endothelium if not removed at the
    end of the surgery

d. methylcellulose is cheaper than sodium hyaluronate

e. Viscoat is made up sodium hyaluronate and chondroitin
    sulphate

answer16.    a.T    b.T    c.F    d.T    e.TPseudoplastic behaviour refers to the ability of solution to reduce its viscosity with applied stress. Solutions with low pseudoplastic behaviour require significant force on the syringe plunger to express the solution from the tip of the cannula.

17. Pseudoexfoliation syndrome:

a. is commonly seen in glass blowers

b. is most commonly in the fifth decade of life

c. causes mid-periphery transillumination

d. causes iridonosis

e. is associated with poor pupillary dilatation

answer17.    a.F    b.F    c.F    d.T    e.TTrue exfoliation is seen in glass blowersPseudoexfoliation is usually seen in the seventh decade and there is peripupillary atrophy with transillumination

18. The advantages of capsulorrhexis over capsulotomy
       include:

a. easier delivery of the nucleus during extracapsular
    cataract operation

b. holds the nucleus in the capsular bag during
    phacoemulsification

c. better centration of the intraocular lens

d. less likelihood of capsular contraction

e. less likelihood of  anterior capsular tear extending into
    the posterior capsule
 

answer18.    a.F    b.T    c.T    d.F    e.T

19. Cataract extraction in an eye that had previous par plana
      vitrectomy is associated with an increased risk of :

a. zonular dehiscence

b. suprachoroidal haemorrhage

c. posterior capsule rupture

d. globe collapse

e. cystoid macular oedema

answer19.    a.T    b.F    c.T    d.F    e.TZonular dehiscence and posterior capsule rupture are the main complications of cataract extraction in an eye that had undergone par plana vitrectomy. Posterior capsule rupture is due toincreased mobility of the posterior capsule.

20. True statements about the aspiration systems used in
       phacoemulsification include:

a. diaphragm pump produces the slowest build up of
    vacuum

b. peristaltic pump allows linear control of vacuum

c. Venturi pump is associated with the highest risk of
     inadvertent engagement of unwanted tissue

d. Venturi pump gives the most rapid rise in vacuum

e. high aspiration is needed during the early stage of
    phacoemulsification

answer20.    a.T    b.T    c.T    d.T    e.FLow aspiration and high power is needed during the early stage of phacoemulsification.
 

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