In the trial frame, on which surface should the cylinder axis markings be visible to the clinician?

In the trial frame, on which surface should the cylinder axis markings be visible to the clinician?

• A. Back
• B. Front
• C. Top
• D. Side

Answer: (B)

The cylinder axis markings should be visible on the surface that the clinician reads directly when aligning lenses in the trial frame. That surface is the front of the lens, which faces outward toward the examiner. Having the axis mark on the front lets the clinician see and orient the cylinder correctly while the patient looks through the lens. If the mark were on the opposite (back) surface, it would be harder for the clinician to read it during fitting, increasing the chance of misalignment. Reading the axis from the front ensures accurate orientation of the astigmatic correction.

The cylinder axis markings should be visible on the surface that the clinician reads directly when aligning lenses in the trial frame. That surface is the front of the lens, which faces outward toward the examiner. Having the axis mark on the front lets the clinician see and orient the cylinder correctly while the patient looks through the lens. If the mark were on the opposite (back) surface, it would be harder for the clinician to read it during fitting, increasing the chance of misalignment. Reading the axis from the front ensures accurate orientation of the astigmatic correction.