CPOA Contact Lens Basics 5 — Questions and Answers
Question 1: Which type of contact lens is specifically designed to vault over the entire cornea and rest on the sclera?
- Corneal RGP lens
- Soft toric lens
- Scleral lens (Correct answer)
- Hybrid lens
Correct answer: Scleral lens
Scleral lenses have large diameters (16–24 mm) that vault completely over the cornea and land on the scleral tissue, making them ideal for irregular corneas.
Question 2: Contact lens-induced acute red eye (CLARE) is most often associated with which lens wear pattern?
- Daily disposable lenses worn as directed
- Frequent replacement lenses worn monthly
- Overnight or extended wear of contact lenses (Correct answer)
- RGP lenses worn for 8 hours daily
Correct answer: Overnight or extended wear of contact lenses
CLARE typically occurs upon waking after sleeping in contact lenses due to hypoxia and bacterial toxin accumulation under the lens.
Question 3: What is the purpose of using fluorescein dye during an RGP contact lens fitting?
- To disinfect the lens before insertion
- To assess the fitting relationship between the lens and cornea (Correct answer)
- To measure the water content of the lens
- To check the oxygen permeability of the lens material
Correct answer: To assess the fitting relationship between the lens and cornea
Fluorescein pools in the tear layer under the RGP lens and glows under cobalt blue light, revealing the fit pattern (bearing, clearance, alignment).
Question 4: Which statement is correct regarding silicone hydrogel contact lens materials compared to conventional hydrogel materials?
- They have lower oxygen permeability
- They have higher oxygen permeability (Correct answer)
- They have a higher water content
- They are not approved for daily wear
Correct answer: They have higher oxygen permeability
Silicone hydrogel materials transmit significantly more oxygen to the cornea than conventional hydrogel materials, reducing hypoxia-related complications.
Question 5: A patient's contact lens prescription specifies 'BC 8.6 / D 14.2 / -3.00 SPH.' What does 'SPH' indicate?
- The lens is a spherical design with no cylinder correction (Correct answer)
- The lens has a spherical base curve
- The add power is spherical
- The lens diameter is spherical
Correct answer: The lens is a spherical design with no cylinder correction
SPH (sphere) indicates this is a spherical lens without astigmatism correction, meaning no cylinder or axis is present.
Question 6: When educating a patient about the risks of sleeping in contact lenses, which complication should be emphasized as the most serious?
- Lens drying out and becoming difficult to remove
- Increased risk of microbial keratitis and corneal ulcers (Correct answer)
- Mild redness upon waking
- Temporary blurry vision after removal
Correct answer: Increased risk of microbial keratitis and corneal ulcers
Sleeping in contact lenses dramatically increases the risk of microbial keratitis, a serious infection that can lead to permanent vision loss.
Question 7: Which solution is safe to use for topping off a contact lens case that still has old solution remaining in it?
- Fresh multipurpose solution added to the existing solution
- Saline solution added to the existing solution
- The case should be emptied, rinsed with fresh solution, and refilled (Correct answer)
- Distilled water added to top off the existing solution
Correct answer: The case should be emptied, rinsed with fresh solution, and refilled
Topping off old solution dilutes its disinfecting efficacy; the case must be emptied, rinsed with fresh solution, and completely refilled.
CPOA Contact Lens Basics 5
Which type of contact lens is specifically designed to vault over the entire cornea and rest on the sclera?