Accommodative insufficiency (AI) involves the inability of the eye to focus properly on an object.
[1] AI is generally considered separate from presbyopia, but mechanically both conditions represent a difficulty engaging the near vision system (accommodation) to see near objects clearly.
Presbyopia is physiological insufficiency of accommodation due to age related changes in lens (decreased elasticity and increased hardness) and ciliary muscle power.
[4] Premature sclerosis of lens or ciliary muscle weaknesses due to systemic or local cases may cause accommodative insufficiency.
[1] Near vision will be blurred, and asthenopic symptoms like head ache and eye strain may occur while reading.