convergence insufficiency

Convergence insufficiency is an inability to obtain or maintain enough convergence for comfortable binocular vision at near.¹ The defining findings are an exophoria at near, orthophoria or a low exophoria at distance, a receded near point of convergence, reduced positive fusional vergence and a low AC/A ratio.² Among nonstrabismic binocular vision problems, convergence insufficiency is the most common, with a reported prevalence of about 3% to 5%.²

Convergence insufficiency acts like a permanently decompensated exophoria at an unusually close working distance, which can decompensate briefly at the normal working distance when the patient is tired.¹ Symptoms often improve dramatically after therapy, along with the near point of convergence and fusional convergence amplitudes, and that response places the condition on an innervational basis.³ An older theory blamed a congenital weakness of the medial rectus muscles, and that theory has not held up.³

Patients report eyestrain and a sense of tension around the globes, and after brief reading the letters blur and run together.³ Crossed diplopia occasionally occurs during near work, ocular headaches are frequent, and patients characteristically close or cover one eye to read.³ A receded near point of convergence is the most consistent finding, and about 94% of optometrists surveyed used the near point in making the diagnosis.²