Contact Lens Principles Flashcards
7 cards from real COT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Contact Lens Principles flashcards as text
Which term describes the phenomenon where a soft contact lens tightens on the eye after extended wear, reducing movement?
Answer: Lens binding (tight lens syndrome)
Lens binding occurs when mucus accumulates under the lens and adheres to the cornea, causing the lens to become immobile — particularly after extended or overnight wear.
A patient wearing daily soft lenses develops a red eye immediately after insertion each morning. The most likely cause is:
Answer: Toxicity or hypersensitivity to the lens packaging solution or preservative
Immediate-onset redness upon insertion of daily disposable lenses suggests a reaction to the packaging solution (e.g., phosphate buffer) rather than a chronic deposit issue.
Which keratometry reading relationship is used as a starting guide when selecting an initial RGP base curve?
Answer: Select a base curve 0.25–0.50 D steeper than the flattest K (align or slightly steep)
A common starting guideline is to fit the RGP base curve on K (aligned) or slightly steeper than the flattest keratometry reading to achieve an aligned fluorescein pattern.
What does a 'plus carrier' lenticular design in a rigid contact lens provide?
Answer: A thicker peripheral zone to improve lid interaction and superior positioning
A plus carrier lenticular edge is thicker at the periphery, encouraging the upper lid to ride over and center the lens in a lid-attachment fit.
Corneal neovascularization (pannus) associated with contact lens wear is primarily caused by:
Answer: Chronic hypoxia stimulating new blood vessel growth into the cornea
Prolonged corneal hypoxia triggers angiogenic factors (VEGF) that stimulate limbal blood vessel growth into the normally avascular cornea.
Which contact lens care step is considered the most critical in preventing Acanthamoeba keratitis?
Answer: Avoiding tap water contact with lenses and lens cases
Acanthamoeba organisms are present in tap water, so rinsing lenses or cases with tap water is a major risk factor for this devastating infection.
What is the primary purpose of using sodium fluorescein during a rigid contact lens fitting evaluation?
Answer: To visualize the tear layer distribution between the lens and cornea
Fluorescein fills the tear layer under a rigid lens and fluoresces under cobalt blue light, revealing areas of bearing (dark) and clearance (bright) for fit assessment.