Test 17  (Refractive surgery)
1. The refractive state of the eye may be altered by:
a. paralysing the ciliary muscle

b. changing the depth of the anterior chamber

c. removing the vitreous

d. increasing the thickness of the lens

e. changing the axial length of the eye


2. Monovision:
a. refers to the use of one eye for distant vision and the other for near

b. is mainly reserved for presbyopic patients

c. requires one eye to be made hypermetropic and the other myopic

d. reduces visual acuity

e. reduces stereopsis

3. The following are contraindication to refractive surgery:

a. age less than 21

b. keratoconus

c. discontinuation of gas permeable lenses wear for 
    less than ten weeks

d. tilted disc

e. irregular astigmatism


4. Photorefractive keratectomy:
a. uses excimer laser made up of ultraviolet radiation

b. uses thermal energy for reshaping the corneal contour 

c. corrects myopia by flattening the central cornea

d. causes more stromal scar in high myope than low

e. is less predictable for high myope than low myope

5. LASIK is superior to photorefractive keratectomy in that it :

a. is a less painful procedure

b. gives a faster visual rehabilitation

c. can treat a higher myopia

d. has less complication

e. has less myopic regression


a. is contraindicated in patients with thin cornea

b. involves the use of microtome

c. involves the creation of a complete circular flap

d. can be repeated by lifting the flap created if further refinement is necessary

e. causes less scarring than photorefractive keratectomy


7. The side-effect of LASIK include:
a. reduced corneal sensation

b. inaccurate biometry if the patient requires cataract 
   surgery in later life

c. tear film abnormality

d. erroneously high intraocular pressure with applanation 

e. glare

8. Radial keratotomy:

a. is an irreversible procedure

b. weakens the cornea

c. is used to reduce the refractive power of the cornea

d. is used to increase the refractive power of the cornea

e. flattens the central cornea


9. Radial keratotomy:
a. involves incisions with depth which are at least 80% 
    of the corneal thickness

b. has a greater effect the deeper the incision

c. has a greater effect the longer the cut

d. has a greater effect the smaller the central zone

e. is more predictable than LASIK in treating myopia


10. Temporal corneal incision during phacoemulsification has 
      the following advantages:
a. easier access to the eye

b. reduced incidence of endophthalmitis

c. less surgically induced astigmatism

d. increased surgical view

e. decreased incidence of epithelial downgrowth


11. The following are true about astigmatic keratotomy:
a. the incision is placed perpendicular to the steepest 

b. causes coupling

c. the nearer the incision to the centre the greater 
    the reduction of astigmatism

d. if astigmatic keratotomy were performed for a phakic 
    patient, the site of incision should be based on the 
    corneal topography

e. astigmatic keratotomy can be carried out either as a 
    transverse or arcuate incision

12. The advantages of arcuate incision over transverse incision in 
      astigmatic keratotomy include:

a. more uniform relaxation of the cornea

b. cutting a more uniform thickness of the cornea

c. the entire length is at the same distance from the 
    calculated central zone

d. actual incision length is about 10% longer than 
    a linear incision spanning the same number of degrees

e. reduced risk of post-operative keratitis


13. When a tight suture is placed radially in the cornea, the following 
       may occur:
a. the cornea adjacent to it is flattened

b. the curvature of the cornea along that meridian is 

c. the curvature of the cornea at 900 to that meridian is 

d. the effect on corneal curvature is increased if the suture 
    is deep

e. the effect on corneal curvature is increased if the suture 
    is nearer the centre of the cornea

14. The following are true about intrastromal corneal ring:

a. it can be used to treat myopia

b. it can be used to treat hypermetropia

c. it is made up of PMMA

d. it is a reversible procedure

e. it involves the use of keratome


15. The following involves the use of donor cornea:
a. epikeratophakia

b. keratomileusis

c. keratophakia

d. lamellar keratoplasty

e. penetrating keratoplasty


16. In a patient who has had vitreoretinal surgery:
a. buckling causes a hypermetropic shift

b. buckling induces astigmatism

c. cataract formation is a common complication with 
    macular hole surgery

d. injection of air into the vitreal cavity of a phakic patient 
    causes a myopic shift

e. injection of air into the vitreal cavity of an aphakic 
    patient causes a a hypermetropic shift 

17. The effect of silicone oil in an eye include:
a. reducing the hypermetropic power of an aphakic eye

b. causes a myopic shift in a phakic eye

c. increases the speed of ultrasound passing through it

d. band keratopathy

e. glaucoma

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