ABO Contact Lenses 2

Question 1

A patient wearing soft contact lenses complains of reduced vision late in the day. Slit-lamp examination reveals corneal neovascularization at the superior limbus. What is the most likely cause?

Accepted Answer

Chronic hypoxia from low-Dk lens

Answer

Chronic hypoxia from wearing low-oxygen-transmissible (low-Dk) lenses causes limbal vessel ingrowth to compensate for oxygen deprivation.

Question 2

Which base curve selection guideline applies when fitting rigid gas-permeable (RGP) contact lenses?

Accepted Answer

Align the lens base curve with the flattest K

Answer

The standard RGP fitting philosophy is to align the lens base curve with the flattest keratometry reading to achieve an 'on K' or alignment fit.

Question 3

A toric soft lens rotates 15° nasally on a patient's left eye. Using the LARS rule, how should the lens axis be adjusted?

Accepted Answer

Add 15° to the prescribed axis

Answer

LARS (Left Add, Right Subtract) means if the lens rotates left (nasally on left eye), add that amount of degrees to the prescribed axis.

Question 4

What is the primary advantage of silicone hydrogel contact lenses over conventional hydrogel lenses?

Accepted Answer

Significantly higher oxygen transmissibility (Dk/t)

Answer

Silicone hydrogel lenses have dramatically higher Dk/t values due to silicone's high oxygen permeability, reducing hypoxia-related complications.

Question 5

A patient presents with acute red eye after sleeping in extended-wear contact lenses. Slit-lamp shows a stromal infiltrate with an overlying epithelial defect and mucopurulent discharge. What condition is most suspected?

Accepted Answer

Microbial keratitis

Answer

An epithelial defect with stromal infiltrate and mucopurulent discharge is the hallmark presentation of microbial keratitis, a vision-threatening emergency.

ABO - American Board of Optometry Practice Test

ABO - American Board of Optometry Practice Test

ABO Contact Lenses 2