Competition Questions - Contact Lens Part 2

Contact Lens -  Questions

Q36. Discomfort along the lower lid margin and reduced oxygen transmissibility are disadvantage of all of the following soft toric lens desigs, expect:
a. Prism ballast
b. Peri-ballast
c. Truncation
d. Double slab-off

Q37. A bacteriostatic agent in a contact lens solution will:
a. Eliminate all bacteria present
b. Prevent bacteria from producing exotoxins
c. Suppress the growth of bacteria in solution
d. Inhibit the movement of bacteria in the solution

Q38. How much oxygen is required by the cornea to maintain regular function?
a. 2 - 4%
b. 15 – 21%
c. 25 – 40%
d. 50 – 70%

Q39. What happens to the centre of gravity of an RGP lens if the total lens diameter is reduced from 9.60mm to 9.00mm?
a. It moves more anteriorly
b. It moves upwards
c. It moves more posteriorly
d. It moves downwards

Q40. A rigid gas permeable lens rides high on the eye. Which of the following parameter changes would be most effective in improving lens centration?
a. Flatter BOZR
b. Steep BOZR
c. Increased edge thickness
d. Decrease centre thickness

Q41. Which of the following is the correct combination of average corneal curvature and thickness?
  Corneal Curvature    Thickness
a. 7.76mm                0.05mm
b. 7.76mm                0.50mm
c. 7.86mm                0.05mm       
d. 7.86mm                0.50mm

Q42. A soft contact lens shows a semi-opaque, whitish superficial film on the lens surface, which is cracking and peeling in some places. The lenses are 14 months old, and the patient uses thermal disinfection daily. The patient complains of dryness and slight discomfort. What kind of deposit is on the lens?
a. Lipid deposits
b. Protein deposits
c. Jelly bumps
d. Calcific crystals

Q43. Which edge configuration of an RGP lens would enhance lens comfort?
a. Anterior apex with round edge
b. Posterior apex wit round edge
c. Central apex with square edge
d. Anterior apex with square edge

Q44. In against-the-rule astigmatism, the refractive power is greatest around:
a. The 45 degrees meridian
b. The 90 degrees meridian
c. The 135 degrees meridian
d. The 180 degrees meridian

Q45. Which of the following is a non-invasive technique for assessment of tear layer?
a. Tear prism height evaluation
b. Phenol red thread test
c. Rose Bengal staining
d. TBUT

Q46. Which of the following is often used in contact lens solutions to enhance lens wettability?
a. Chlorhexidine
b. Polyvinyl alcohol
c. EDTA
d. Sodium chloride

Q47. Theoretically, contact lenses may be contraindicated in case of:
a. Oblique astigmatism
b. Axial anisometropia
c. Irregular astigmatism
d. Refractive anisometropia

Q48. Which of the following new contact lens wearers is MOST likely to experience tiered eyes and headache, after long period of near work using spherical contact lenses?
a. A 19-years old with a prescription of -7.00Ds
b. A 27-years old with a prescription of -4.50 / -0.50 x 176
c. A 43-years old with a prescription of +8.50 / -0.25 x 89
d. A 39-years old with a prescription of -5.75 / -0.25 x 91

Q49. Which astigmatism type shows an increase with increasing age?
a. Against-the-rule
b. With-the-rule
c. Oblique
d. Irregular

Q50. A patient is wearing an RGP lens with BVP of -5.50D, which accurately compensate for his refractive error. The lens has a BOZR of 7.65mm. if we wanted to fit this patient with a contact lens that has a BOZR of 7.80mm, while maintaining the same total diameter, what BVP should we order for the new contact lens?
a. -4.00 D
b. -4.75 D
c. -6.25 D
d. -7.00 D

Q51. All of the following should be explained to a patient upon RGP lens delivery, EXCEPT
a. Instruction on lens care regimen
b. Specification of lens parameters
c. Normal adaptive symptoms
d. Schedules of aftercare visits

Q52. A soft contact lens wearing patient presents with red left eye. She complains of pain that worsens following lens removal. The patient is also very photophobic, and lacrimation is increased. Further examination shows reduced visual acuity, mucopurulent discharge and diffuse hyperaemia. What is the most likely cause?
a. Conjunctivitis
b. Microbial keratitis
c. Contact Lens Acute Red Eye (CLARE)
d. Giant papillary conjunctivitis (GPC)

Q53. In altering soft contact lens behaviour on the eye, which of the following statements is NOT true
a. Increasing the total lens diameter will decrease the sagittal height
b. Reducing the total diameter will loosen the lens fit
c. Reducing the BOZR will tighten the lens fit
d. Increasing the BOZR of the lens will decrease the sagittal height.

Q54. Contact lens induced peripheral ulcers (CLPUs) are often associated with ocular presence of:
a. Fungi
b. Gram-negative bacteria
c. Protozoans
d. Gram-positive bacteria

Q55. When a hyperope transfers from spectacle to contact lenses, he will use:
a. Less convergence and less accommodation
b. More convergence and less accommodation
c. More convergence and more accommodation
d. More accommodation and less convergence

Q56. Which of the following is the main oxygen supply of the corneal endothelium during closed eye conditions?
a. Atmosphere
b. Aqueous humor
c. Palpebral conjunctiva
d. Corneal epithelium

Q57. To obtain keratometry measurement on an advanced keratoconus patient, the following lens needs to be attached to a one-position keratometer to extend the range of its dioptric powers:
a. +1.25 D to extend the upper limit by 9.00 D
b. +1.00 D to extend the upper limit by 6.00 D
c. -1.25 D to extend the lower range by 9.00 D
d. -1.00 D to extend the lower range by 6.00 D

Q58. What is the estimated amount of cornea oedema present if 3 folds are observed in Descmet’s membrane?
a. 4%
b. 6%
c. 10%
d. 13%

Q59. What is the Back Vertex Power (BVP) of the contact lens needed to correct a spectacle refraction of +8.50 D at a vertex distance of 12mm?
a. +7.75 D
b. +8.25 D
c. +8.50 D
d. +9.50 D

Q60. A soft contact lens wearer presents with a fairy significant reduction in vision. Upon further examination, you notice wrinkling or corrugation of central area of the contact lens. Following lens removal, fluorescein pooling is observed in lines on the cornea. The most appropriate course of action would be:
a. Recommend the use of alcohol-based surfactant cleaners
b. Refit with thinner low water content lens
c. Refit with higher water content, slightly thicker lens
d. Disinfect the lenses with 3% hydrogen peroxide

Q61. What is the estimated amount of corneal oedema present if three striae are observed during slit-lamp biomicroscopy?
a. 3%
b. 7%
c. 10%
d. 13%

Q62. If a patient exhibit a significant amount of corneal toricity, which type of RGP lens design is best to maintain an acceptable lens-cornea relationship?
a. Revers geometry RGP lens
b. Back surface toric RGP lens
c. Spherical RGP lens
d. Front surface toric RGP lens

Q63. A patient’s right eye has keratometry readings of 7.95 mm along 180 degrees (42.50 D) and 7.76 mm along 90 degrees (43.50 D). Which BOZR would be most appropriate when fitting a spherical rigid gas permeable lens to this eye?
a. 7.60mm
b. 7.70mm
c. 7.80mm
d. 7.90mm

Q64. Which of the following is NOT a principle function of rigid lens wetting solutions?
a. Acts as a mechanical buffer between the lens and the finger during insertion
b. Encourages even distribution of tears over the lens
c. Disinfect the lens
d. Acts as a lubricant between surfaces of the lens and the surfaces of the cornea and lids

Q65. Central corneal clouding (CCC) is best observed by:
a. Sclerotic scatter
b. Optic section
c. Specular reflection
d. Tangential illumination

Q66. The permeability of a contact lens material is defined by the combination of its:
a. Oxygen transmissibility and lens thickness
b. Oxygen diffusivity and lens thickness
c. Oxygen transmissibility and oxygen solubility
d. Oxygen diffusivity and oxygen solubility

Q67. A patient wears a soft trial lens with BOZR 8.9mm and TD 14.00mm, and the lens is fitting well. We now decide to reduce the diameter of the contact lens to 13.50mm. if we wanted to retain the same lens-cornea relationship, which BOZR would be MOST appropriate for new contact lens?
a. 8.40mm
b. 8.60mm
c. 9.10mm
d. 9.30mm

Q68. Which of the following slit-lamp illumination techniques could you use to detect the depth of corneal lesions?
a. Direct illumination with an optic section
b. Diffuse illumination
c. Specular reflection with parallelepiped
d. Tangential illumination

Q69. A daily wear soft contact lens wearig patient complains theat their vision blurs and fluctuates with blinking after wearing the contact lens for a few hours. The MOST likely cause is:
a. Acute corneal oedema
b. Jelly bumps on the contact lens surface
c. Lipid deposits on the contact lens surface
d. A loose-fitting lens

Q70. An RGP lens wearer presents with 3 and 9 O’clock staining. Which of the following actions would be LEAST appropriate?
a. Fit RGP lenses with an aspheric back design
b. Prescribe artificial tears
c. Educate patient on the importance of proper blinking
d. Fit RGP lenses that have thicker lens edges