Monocular rock endpoint?

• A. 10 cpm with +1.00/-2.00 lens
• B. 30 cpm with a plano lens
• C. 25 cpm with +5.00/-5.00 lens
• D. 20 cpm with a +2.50/-6.00 lens equally with each eye

Answer: (D)

Monocular rock endpoint testing aims to push the eye just enough to reveal its accommodative limit under a controlled, balanced optical load, without introducing binocular interactions or uneven blur between eyes. The best setup is one that provides equal stimulus to each eye and a moderate, sustainable testing pace so the eye can clearly reach an endpoint without fatigue or confusing blur.

Choosing the same lens power for both eyes creates a symmetric challenge, so any measured endpoint reflects the monocular system’s capacity rather than differences between eyes. The rate of 20 cycles per minute is a middle ground—fast enough to test dynamic accommodation but slow enough to keep the target stable and the endpoint observable. The lens combination described yields a mild overall refractive demand (a small net effect across meridians) so accommodation is engaged without overwhelming it or producing extreme, unhelpful blur from large astigmatic differences.

Other options either remove the accommodation cue (plano lens), impose uneven or extreme astigmatic demands across meridians, or apply a faster rate that can introduce fatigue or imprecise endpoints. Therefore, applying an equal lens load to each eye at a moderate rocking rate best isolates the monocular endpoint.