Your patient has 10/100 vision at 10 feet. What is the cylinder power?

Your patient has 10/100 vision at 10 feet. What is the cylinder power?

• A. 0.50
• B. 1.00
• C. 2.00
• D. 3.00

Answer: (C)

Cylinder power measures astigmatism correction and is determined through a refraction, not from distance visual acuity alone. Knowing a patient’s acuity of 10/100 at 10 feet tells you how blurred detail is, but it doesn’t reveal the amount or orientation of cylindrical error in the eye. Different astigmatic corrections can produce similar acuity levels, so you can’t deduce the cylinder value from this acuity data. To obtain the correct cylinder power, you’d perform a refraction (retinoscopy or subjective refinement) and determine the cylindrical correction that best sharpens vision.

Cylinder power measures astigmatism correction and is determined through a refraction, not from distance visual acuity alone. Knowing a patient’s acuity of 10/100 at 10 feet tells you how blurred detail is, but it doesn’t reveal the amount or orientation of cylindrical error in the eye. Different astigmatic corrections can produce similar acuity levels, so you can’t deduce the cylinder value from this acuity data. To obtain the correct cylinder power, you’d perform a refraction (retinoscopy or subjective refinement) and determine the cylindrical correction that best sharpens vision.