Glossary (still in progress)
Accommodation: The process of focusing our eyes to make targets clear at different distsances. Accommodation works with vergence; it is a neuromuscular process. This visual skill regulates the focus of the eyes at different distances. To accommodate for clear vision at various distances the lens in our eye actually changes shape. The somewhat gelatinous material of the lens is “stretched” or “squashed” due to muscle actions within the eye, this change in shape changes the power of the lens. A camera lens that can zoom in and out simulates this idea.
Accommodation Excess: A diagnosis made by the doctor when a focusing system is overactive, uses more power than necessary and stay stimulated even when stimulus is absent. A person with this condition exerts too much power when working on near tasks.
Accommodation Insufficiency: A diagnosis made by the doctor when the focusing system is underactive, or does not supply enough power to provide a clear image at a particular distance and will have trouble switching focus easily between distances, particularly far to near and vice versa.
Accommodation Posture:The measured distance ahead of or behind the object of regard where the focusing system "rests." If this posture is either closer than the object or farther than the object, such as a book, the visual system must work harder to keep the object clear.
Amblyopia: Low or reduced visual acuity not correctable by refractive means, (glasses or contacts) and exists despite any apparent structural or pathologic abnormalities of the eye. Amblyopes often are strabismic (exotropic or esotropic). A common lay term for amblyopia is “lazy eye,” and should be a diagnosis of exclusion of other causes of reduces clarity of sight.
Ammetropia: Having a refractive error.
Astigmatism: Astigmatism nearly always refers to the shape of the front of the eye, the cornea (occasionally astigmatism exists in the lens of the eye). A spherical cornea has no astigmatism, a cornea shaped more like the bowl of a spoon distorts images, the light rays are being bent and focused at more than one spot creating a less than clear image, the image appears to have a haze surrounding it, or a “ghost image.”
Binocular: If a person uses both eyes together they see binocularly. Binocular vision allows us to see depth and dimension, people lacking good binocular vision are unable see the images in the “magic pictures.” Double vision can be a consequence of poor binocularity, sometimes the person will, unconciously, simply shut down one eye to avoid seeing double.
Esotropia: An esotropic eye turns inward toward the nose. This eye turn may be evident all the time or only when a person is fatigued and may be subtle enough that only a trained eye professional will detect the turn. The eye turn may be related to a high refractive error, a muscle or nerve weakness or occasionally a muscle trapped against a bone.
Exotropia: An eye that turns outward toward the temple. This eye turn may be evident all the time or only when a person is fatigued and may be subtle enough that only a trained eye professional will detect the turn. The eye turn may be related to a high refractive error, a muscle or nerve weakness or occasionally a muscle trapped against a bone.
Eyesight: The ability to see light, a sense that most of us are born with. SEE: VISION
Fovea: The fovea located on the retina of the eye is the point from which we see most sharply and where the receptors are located that allow us to see colors. In a normal visual system the fovea of the left and right eye are directed at the same point in space at the same time giving us a better image than either eye alone.
Hyperopia: Farsightedness, a farsighted person often has good vision at near and far distances, however the persons eyes are naturally focused in the distance and so a lot of extra effort is needed to bring near objects into focus, for example the work a student does at their desk. This translates to eye fatigue, headaches and often, poor ability to stay on task.
Myopia: Nearsightedness, a myopic person has good vision at near but cannot see well far away.
Refractive Error: This term is typically used to describe eye problems that can be remedied with glasses or contact lenses. Lens powers are found during the eye exam that will, when combined with the eyes own power, converge parallel rays of light onto the retina to create the best image possible. Myopia, hyperopia, and astigmatism are common problems of refractive error.
Strabismus: The patient cannot fixate/foveate an object binocularly under normal conditions. That is, the person cannot keep both eyes directed at the same point in space, the person is exotropic or esotropic.
Vergence: Vergence works in combination with accommodation, it is the skill that regulates where in the plane of regard we are aiming our eyes so that we see single and not double images. Convergence implies both eyes are turning medially, toward the nose, in the case of divergence both eyes are moving outward toward the temples.
Vision: Vision is a learned, dynamic (or changing) process of organizing, interpreting and understanding what is seen. It is a process that integrates sensory and motor information generated by the brain and body to derive meaning and direct movement. SEE: EYESIGHT