Convergence excess is the binocular vision problem where the eyes turn in too much (go cross-eyed) when looking at near, and then get 'locked-in' and can't straighten out for comfortable distance vision. As a result, the eyes are not sure where they are pointing in space, and therefore cannot give the focusing system the right information to allow the eyes to focus. This can often result in symptoms of blurred distance vision.
Near visual stress is common but can be easily missed in a standard eye examination if visual efficiency (not just clarity) is not assessed, often resulting in misdiagnosis and incorrectly prescribed distance glasses.
Intermittent distance blur and near visual stress, if not treated, frequently precedes true myopia (short-sightedness), in which the visual system adapts permanently to near visual stress by becoming short-sighted, causing constant distance blur. True myopia is a life-long, progressive condition, in which constant correction (glasses, contact lenses) is required to see clearly. Myopia is also associated with a higher prevalence of eye diseases such as retinal detachment and glaucoma.
Prevention of myopia is the key treatment goal when addressing near visual stress, along with active management of symptoms to prevent it from affecting a child's academic and sporting performance.