COT Contact Lens Principles 4

Question 1

Which condition describes superficial punctate staining in a 3 o'clock and 9 o'clock distribution on the cornea during RGP lens wear?

Accepted Answer

Desiccation staining from incomplete blinking

Answer

Peripheral desiccation staining at 3 and 9 o'clock positions occurs when the area adjacent to the rigid lens is not adequately covered by the tear film during blinking.

Question 2

A scleral contact lens differs from a corneal RGP lens primarily because it:

Accepted Answer

Vaults entirely over the cornea and rests on the sclera

Answer

Scleral lenses have a large diameter (15–25 mm) that vaults over the entire cornea and lands on the scleral conjunctiva, creating a fluid reservoir.

Question 3

What is orthokeratology (ortho-k)?

Accepted Answer

Use of specially designed rigid lenses worn overnight to temporarily flatten the cornea

Answer

Orthokeratology uses reverse-geometry rigid lenses worn during sleep to temporarily reshape the corneal epithelium, providing clear unaided daytime vision.

Question 4

Which measurement tool is used to evaluate contact lens fit parameters such as base curve, diameter, and thickness?

Accepted Answer

Radiuscope (ophthalmometer)

Answer

A radiuscope (also called an optical spherometer) measures the back surface radius of curvature of rigid contact lenses.

Question 5

Microcystic corneal edema seen at the slit lamp is an early sign of which contact lens problem?

Accepted Answer

Chronic corneal hypoxia from insufficient oxygen transmissibility

Answer

Microcystic edema (epithelial microcysts) develops when chronic hypoxia disrupts normal epithelial cell metabolism and turnover.

COT - Certified Ophthalmic Technician Practice Test

COT - Certified Ophthalmic Technician Practice Test

COT Contact Lens Principles 4