Competition Questions - Contact Lens Part 1

Contact lens - Questions

Q1. Which of the following modifications to rigid gas permeable (RGP) lenses can NOT be made in a typical contact lens practice
a. Thinning the edge
b. Reducing the total diameter (TD)
c. Flattening the peripheral curves
d. Steepening the Back Optic Zone Radius (BOZR)

Q2. The best view of corneal neovascularisation using a slit-lamp is obtained by….
a. Diffuse illumination
b. Retro illumination
c. Specular reflection
d. Conical beam

Q3. For an eye with subjective refraction -4.00 / -3.00 x 180, and keratometry readings 44.00 / 46.00@ 90, the lenticular astigmatism is
a. -1.00 DC x 90
b. -1.00 DC x 180
c. -2.00 DC x 90
d. -3.00 DC x 180

Q4. The most effective metabolic pathway by which the cornea receives its energy is…
a. Embden Meyerhof Pathway
b. Tricarboxylic acid cycle
c. Hexose monophosphate shunt
d. Pentose phosphate pathway

Q5. A long term soft contact lens wearer visits your office, and complains of reduced lens comfort and decreased wearing time, as well as fluctuation in vision. Upon examination you note corneal oedema, distorted keratometry mires, haze in the posterior stroma, and endothelial polymegathism. The most likely cause would be…
a. Endothelial bleb response
b. Microbial keratitis
c. Corneal exhaustion syndrome
d. Contact lens peripheral ulcer

Q6. Using the Cartesian system, describe the position of a temporally displaced lens of overall diameter 14.0mm, with its edge at the limbus, if the patient has a HVID 12.5mm and is wearing the lens in his left eye.
a. X = + 0.75; Y = 0.00
b. X = - 0.75; Y = 0.00
c. X = + 1.50; Y = 0.00
d. X = - 1.50; Y = 0.00

Q7.  The best way for a patient to remove RGP lens deposits is by ….
a. Polishing the lens surface
b. Using an alcohol based surfactant cleaner
c. Thermally disinfecting the lens
d. Using enzymatic cleaner

Q8. Which soft contact lens manufacturing technique will produce the most flexible lens?
a. Lathe cutting
b. Spin casting
c. Cast moulding
d. Moulding with a lathed back surface

Q9. A patient is wearing soft contact lens with BOZR 8.90mm and total diameter 14.0mm. If we wanted to refit this patient with a lens that has a total diameter of 14.5mm, but we do not want to change the lens-cornea fitting relationship, what BOZR should we choose for new lens?
a. 8.60mm
b. 8.90mm
c. 9.20mm
d. 9.50mm

Q10. How many cell layers does the normal corneal epithelium consist of?
a. One
b. Three
c. Five
d. Eight

Q11. A patient has keratometry readings of 7.90mm along 160 degree (42.75D) and 7.80mm along 70 degree (43.25D). What base curve Radius should be chosen when fitting a spherical soft contact lens to this eye?
a. 8.10mm
b. 8.40mm
c. 8.60mm
d. 9.30mm

Q12. A normal blink rate is approximately
a. 2 blinks per minute
b. 5 blinks per minute
c. 15 blinks per minute
d. 28 blinks per minute

Q13. Which of the following is the BEST approach to refitting PMMA wearer with RGP lenses?
a. Immediately refit with RGP lenses after removal of PMMA lenses
b. No lens wear until the K-readings becomes stable and then refit with RGP lenses
c. Reduce wearing time with the PMMA lenses, and then refit with RGP lenses
d. Gradual reduction of PMMA wear, with gradual increase in RGP wearing time.

Q14. According to ‘Holden & Mertz (1984), what should be transmissibility of an EW contact lens be to limit/prevent overnight corneal swelling?
a. Dk/t = 24 x 10-9
b. Dk/t = 24 x 10-11
c. Dk/t = 87 x 10-9
d. Dk/t = 87 x 10-11

Q 15. The management of corneal neovascularisation in soft contact lens wearer could include all of the following, except:
a. Refit with RGP lenses
b. Change in lens care regimen
c. Refit with thicker low water content lenses
d. Increase lens Dk/t

Q16. A patient has a spectacle prescription of -5.25 / -2.75 x 170. The keratometry measurement are 7.76mm @ 170 degree (43.50D) and 7.67mm @ 80 degree (44.00D). Which of the following contact lens types would be the most appropriate
a. Spherical rigid gas permeable lens
b. Back-surface toric rigid gas permeable lens
c. Spherical soft contact lens
d. Front-surface toric rigid gas permeable lens

Q17. Bio-microscopy with a conical beam is best used to view
a. Epithelial oedema
b. Crystalline Lens opacities
c. Cells and Flares in the anterior chamber
d. Corneal staining

Q18. Corneal innervation takes place via which cranial nerve
a. Optic nerve (N2)
b. Oculomotor nerve (N3)
c. Trigeminal nerve (N5)
d. Facial nerve (F7)

Q19. The use of small diameters in Toric RGP lenses is mainly for:
a. Strong lid forces
b. High plus powers
c. Steeper corneas
d. Normal lid margin

Q20. A patient is wearing an RGP lens with BOZR of 7.80mm and total diameter 9.20mm. The flurosceine pattern of the lens on the eye shows an alignment fit. If we wanted to create a similar fitting relationship with a lens that has a BOZR of 7.60mm, which of the following total lens diameters would be most appropriate:
a. 9.00mm
b. 9.20mm
c. 9.30mm
d. 9.40mm

Q21. The corneal endothelium mosaic can be best observed by
a. Specular reflection
b. Conical beam
c. Sclerotic scatter
d. Retro illumination

Q22. Approximately what percentage of the corneal thickness is made-up by the stroma
a. 10%
b. 40%
c. 65%
d. 90%

Q23. Which of the following changes in lens parameters will result in a more anteriorly placed centre of gravity?
a. Increasing the back optic zone diameter (BOZD)
b. Decreasing the lens thickness
c. Increasing the minus power
d. Increasing the back optic zone radius (BOZR)

Q24. A patient with ocular astigmatism at axis 160 degree has a trial lens placed on her left eye. The lens rotates 15 degree anticlockwise. What should the cylinder axis of the final toric soft contact lens be:
a. 15 degree
b. 145 degree
c. 165 degree
d. 175 degree

Q25. A soft contact lens wearing patient comes to your consulting room, complaining of a sudden decrease in lens tolerance in both eyes, stinging upon lens insertion, and foreign body sensation. During slit-lamp biomicroscopy, you see conjunctival hyperemia and diffuse corneal staining with fluorescein. What do you suspect?
a. Viral conjunctivitis
b. Solution toxicity reaction
c. Contact lens acute red eye (CLARE)
d. Contact lens induced peripheral ulcer (CLPU)

Q26. A patient is wearing an RGP lens, which has BOZR of 7.80mm and BOZD of 7.00mm. The lens fit is satisfactory. If we want to achieve the same sagittal relationship with a new lens that has a BOZR of 7.90mm, what should the BOZD of this new lens be?
a. 6.80mm
b. 7.20mm
c. 8.00mm
d. 8.40mm

Q27. Which slitlamp technique is BEST suited to an eye examination of epithelial microcysts?
a. Optic section
b. Diffuse illumination
c. Marginal retro-illumination
d. Sclerotic scatter

Q28. A well centred toric soft contact lens gives full corneal coverage, shows little movement and is slow to return to axis when mislocated. Without changing lens diameter, which of the following actions would be most appropriate?
a. Decrease lens thickness
b. Increase lens thickness
c. Increase the BOZR
d. Change the axis of the cylinder power

Q29. Which of the following is mercurial preservative?
a. Polyquad
b. Thimersol
c. Dymed
d. Chlorhexidine

Q30. The fluorescein pattern of RGP lens with BOZR 7.60mm shows significant central pooling. Without hanging the total diameter, which BOZR would be most appropriate?
a. 7.40mm
b. 7.55mm
c. 7.60mm
d. 7.75mm

Q31. The mucus layer of the tearfilm is mainly supplied by:
a. Meibomain glands
b. Conjunctival goblet cells
c. Gland of Krause
d. Glands of Wolfring

Q32. A soft contact lens wearing patient reports that his vision clears immediately after a blink, but quickly reverts to a lesser quality. This probably indicates that:
a. Total lens diameter is too small
b. The lens fit is too flat
c. The lens moves excessively
d. The lens fit is to steep.

Q33. A patient with spectacle prescription of -4.50 D and keratometry measurement of 44.00D along 175 degree s and 422.25 along 85 degrees would be best corrected with:
a. Spherical RGP lens
b. Back surface toric RGP lens
c. Spherical soft contact lens
d. Double slab-off soft toric lens

Q34. When fitting a soft contact lens, one normally determines the BOZR by:
a. Making it the same as the flattest keratometry reading
b. Making it 0.1mm flatter than the flattest keratometry reading
c. Making it the same as the steepest keratometry readings.
d. Making it 0.7mm flatter than the flattest keratometry reading

Q35. Which of the following signs (seen on Slit-lamp biomicroscopy) are MOST commonly found in patients with Contact Lens Acute red Eye (CLARE):
a. Corneal staining
b. Corneal thinning
c. Vertical striae
d. Corneal infiltrates

Read more:
Competition questions - Contact Lens Part-2