Would you expect more of a lag of accommodation on MEM in Convergence Insufficiency or Convergence Excess?

• A. Convergence Insufficiency
• B. Convergence Excess
• C. Both equally
• D. Neither

Answer: (B)

MEM measures how the eye’s accommodation at near compares to the optic demand. A lag means the eye isn’t accommodating enough for the target; a lead means it’s over-accommodating.

In convergence excess, the AC/A ratio is high, so small amounts of accommodation provoke more convergence than usual. Because fusion can be maintained through this vergence drive, the accommodative system doesn’t need to respond as strongly to a near target, so the actual accommodation response can lag behind the demand. That gives a larger lag on MEM.

In convergence insufficiency, the AC/A ratio is lower, so the vergence system isn’t overdriving convergence for a given accommodation; the accommodative response tends to be closer to the demand (or even slightly leading). This makes the MEM lag less pronounced than in convergence excess.

So, more lag on MEM is expected with convergence excess.