Contact Lens Fitting and Care Flashcards

Which measurement is most critical when fitting a spherical soft contact lens for proper centration and comfort?

Answer: Horizontal visible iris diameter (HVID)

HVID is used to select the correct contact lens diameter to ensure proper centration and limbal clearance.

A patient presents with a base curve of 7.80 mm on their current contact lens and complains of lens tightness. What adjustment should be made?

Answer: Increase the base curve to 8.00 mm

A flatter (larger) base curve provides more movement and reduces the tight fit sensation.

What does a fluorescein pattern showing central pooling (dark ring around center) indicate in a rigid gas permeable (RGP) lens fit?

Answer: Steep fit

Central pooling of fluorescein beneath an RGP lens indicates the lens is fitting steeper than the cornea.

Which contact lens wearing schedule requires the most stringent patient education regarding infection risk?

Answer: Extended wear (overnight)

Extended wear lenses significantly increase the risk of microbial keratitis due to reduced oxygen transmission and disrupted tear film during sleep.

A patient with presbyopia wants contact lenses. Which design uses different optical zones on a single lens to provide both distance and near vision?

Answer: Simultaneous vision multifocal

Simultaneous vision multifocal contact lenses have concentric or aspheric zones that present both distance and near prescriptions to the eye at the same time.

What is the primary purpose of the lens edge lift in an RGP contact lens fit?

Answer: To allow tear exchange and lens movement

Edge lift in RGP lens design promotes tear exchange beneath the lens and allows adequate lens movement for corneal health.