L1. Accommodation Basics

What tests and procedures are affected by accommodation?

• VA

• pupils

• EOM’s

• Cover test

• Stereoacuity testing

• Retinoscopy

• Autorefraction

• Subjective refraction

• NRA/PRA

• AA

• MEM/Nott

• Accommodative facility

• Slit lamp/tonometry alignment

What is the definition of accommodation?

The eye’s ability to bring objects located at different distances into focus by changing the shape of the lens

What does accommodation do?

It adds more plus power to the eye/focuses nearer objects

How is true accommodative demand (TAD) found?

TAD = standard accommodative demand + refractive error - Corrective lens power

What are the two main clinical ways to think about accommodative demand?

• Type of refractive error relative to its correction

• Lens power relative to the patient’s refractive error

These determine how much accommodation the patient must exert at different working distances.

How does correction status affect accommodative demand in myopic patients?

• Fully corrected myope: Normal accommodative demand.

• Over‑corrected (“over‑minused”) myope: Increased accommodative demand.

• Under‑corrected myope: Decreased accommodative demand → behaves like having a built‑in add (similar to reading glasses).

How does correction status affect accommodative demand in hyperopic patients?

• Fully corrected hyperope: Normal accommodative demand.

• Over‑corrected (“over‑plused”) hyperope: Decreased accommodative demand → functions like a built‑in add.

• Under‑corrected hyperope: Increased accommodative demand (must use more accommodation to compensate).

What is the goal of refraction?

Least minus power for maximum VA = determine lens power that brings distance target into focus when all accommodation is relaxed.

How does anisometropia/aniseikonia affect the spectacle prescription?

A full refractive correction may not be tolerated in spectacles if it causes significant image size disparity between the eyes (aniseikonia). Therefore, the final spectacle Rx may be modified from the refraction to improve binocular vision and reduce symptoms.