Contact Lens Fundamentals Flashcards

Which condition is most directly associated with chronic corneal hypoxia from extended contact lens wear?

Answer: Corneal neovascularization (pannus)

Corneal neovascularization occurs when the oxygen-deprived cornea stimulates new blood vessel ingrowth from the limbus to compensate for hypoxia caused by inadequate oxygen transmission through extended contact lens wear.

What is the most appropriate initial management for a contact lens wearer who presents with a red, painful eye and a central corneal infiltrate?

Answer: Immediately discontinue lens wear and refer to a physician for evaluation of possible microbial keratitis

A central corneal infiltrate in a contact lens wearer is a potential sight-threatening emergency, and lens wear must be stopped immediately with urgent referral to rule out microbial keratitis.

What is the purpose of the sagittal depth (sag) in contact lens fitting?

Answer: It describes the vault of the lens over the cornea, determining how the lens sits relative to the corneal surface

Sagittal depth (sag) is the depth of the contact lens vault — the perpendicular distance from the chord diameter to the back surface — which determines how the lens fits relative to the corneal height.

A patient switches from glasses (spectacle Rx: -5.00 D) to contact lenses. Due to vertex distance, the expected contact lens power will be approximately:

Answer: Less minus than the spectacle prescription

As myopic spectacle lenses are moved closer to the eye (from ~12 mm vertex to 0 mm at the cornea), the effective power decreases, so the contact lens needs less minus power than the spectacle prescription.

Which parameter is most important when fitting a toric soft contact lens?

Answer: The axis orientation and stabilization mechanism to minimize lens rotation

For toric soft lenses, controlling lens rotation and maintaining correct axis alignment is critical, since even a small amount of rotation away from the prescribed axis significantly reduces astigmatic correction.

When teaching a patient to insert a soft contact lens, which instruction is most important for preventing infection?

Answer: Wash and dry hands thoroughly before handling lenses

Hand hygiene is the single most important step in preventing contact lens-related infections, as contaminated hands are the primary route of pathogen transfer to the ocular surface.

Which contact lens parameter should be steepened if a patient's RGP lens shows excessive movement and falls inferiorly with each blink?

Answer: Base curve should be steepened (smaller radius of curvature)

Steepening the base curve (using a smaller radius of curvature number) makes the lens fit more closely to the cornea, reducing excessive movement and preventing inferior decentration.