The scientific definition of hardness is the ability to resist scratching, nothing more. If you ask most folks, theyâll say feathers are soft and glass is hard. In the world of gemology, however, glass is fairly soft. It can be scratched easily by a variety of what we gemologists consider hard substances.
convergence excess. Convergence excess is an over-convergence of the eyes at a near distance for extended periods of time, such as when reading, writing, drawing, or viewing a computer screen. Sometimes, the over-convergence can result in diplopia (double vision).nce a diagnosis of convergence insufficiency has been made, a simple visual therapy technique that may be helpful is pencil pushups. 1. Hold a pencil at arm s length, with the eraser about level with the tip of your nose.
What is convergence insufficiency? Convergence insufficiency is the inability to maintain binocular function (keeping the two eyes working together) while working at a near distance. Typically, one eye will turn outward (intermittent exotropia) when focusing on a word or object at near. In convergence insufficiency, eye misalignment occurs when focusing at near.