Glossary

Bifoveal fixation: In normal eyes, the condition in which the fovea of one eye “corresponds” to the fovea of the other eye, and the image of the target object is fixated so that the image of the target falls on both foveas. This provides the basis for fusion of the images and stereopsis.

Binocular: Refers to the organized simultaneous perception of information from the right eye and the left eye.

CA/C ratio: The amount of ref lex convergence-accommodation stimulated during convergence. Expressed as a ratio of convergence-accommodation/ convergence.

Cheiroscopic tracing: A drawing made in a stereoscope that can give information about binocular alignment, suppression, visual stability, aniseikonia, and visual-spatial projection.

Comitant: Also known as concomitant. In strabismus, when the angle of deviation is the same in all positions of gaze. Noncomitant, also known as nonconcomitant, in strabismus, or phoria, when the angle of deviation varies as the eyes are moved to different positions of gaze.

Compensatory lens: See Lens. Constructional apraxia: See Apraxia. Convergence: See Vergence.

Cover test: A test that provides an objective determination of the presence, type (phoria or tropia, eso, exo, hyper, or hypo), and amount of an ocular deviation.

Covert attention: See Attention.

Cranial nerves: Twelve pairs of nerves that emanate directly from the nervous tissue of the brain. This is in contrast to spinal nerves that emerge from segments of the spinal cord. Six of the twelve pairs are involved with the eyes and vision.

Cyclotorsion: Rotation of the eye around its visual axis. It occurs normally. However, it may also be pathological after an eye injury, surgery, or ABI and, if large in magnitude, it will interfere with or prevent binocular alignment of the eyes and fusion of visual images.

Divided attention: See Attention.

Decision tree: A decision support tool for calculating conditional probabilities to help to identify a strategy most likely to reach an outcome or goal.

Decompensated phoria: See Phoria.

Diplopia: Double vision. The condition in which a single object is perceived as two objects instead of one.

Divergence: See Vergence.

Duane’s Retraction Syndrome: A congenital eye condition characterized by a limitation of abduction (outward movement) of the affected eye, retraction of the eyeball on adduction (inward movement), with an associated narrowing of the palpebral fissure (closing of the eye).

Duction: The movement of only one eye.

Eso: A prefix indicating that the eyes are deviated inward, or pointing closer than the object of regard.

Esophoria: See Phoria.

Exo: A prefix indicating that the eyes are deviated outward, or pointing farther than the object of regard.

Exophoria: See Phoria.

Egocentric localization: The localization of objects in space in reference to one’s own body.

Fixation: The maintenance of visual gaze on a single location.

Fixation disparity: A small misalignment or instability in eye alignment under binocular viewing conditions.

Gaze palsy: A limitation of the movement of one eye or of both eyes to move in the same direction at the same time.

Graded occlusion: See Occlusion. Guidance lens: See Lens. Hemiparesis: See Paralysis.

Homonymous hemianopia: Loss of vision in the same visual f ield of each eye resulting in a loss of vision in the right or left visual field.

Homolateral: Pertaining to one side of the body.

Hyper: A prefix indicating that one of the eyes is deviated upward, or pointing higher than the object of regard. Also, greater or more, as in hypermetric saccades.

Hypo: A prefix indicating that one of the eyes is deviated downward, or pointing lower than the object of regard. Also, insufficient or less, as in hypometric saccades.

Hypermetric saccade: See Saccade. Hypometric saccade: See Saccade.

Hyperopia (farsightedness): Light rays coming from a distant object strike the retina before coming to sharp focus. Causes the individual to use additional accommodative effort to keep objects clear.

Ideational apraxia: See Apraxia.

Lens: Optical device that causes light to bend or become focused in a different point in space. Minus lenses (concave) are used for myopia and make objects appear smaller and closer in space. Plus lenses (convex) are used for hyperopia and make objects appear larger and further in space. Astigmatic lenses have different powers in one meridian than another causing light to be focused at different places in space. A compensatory lens is one that allows the person to function better with their existing visual anatomy and physiology. A guidance lens is one prescribed with the desire of shifting the posture of either eyes or the body to some different status in the future

Minus lens: See Lens.

Monocular: Having only one eye, or when each eye is used separately, for example, when one eye is covered, as during a vision therapy procedure.

Myopia (nearsightedness): Light rays coming from a distant object are brought to focus in front of the retina interfering with the formation of a clear image of objects viewed in the distance.

Nearpoint retinoscopy: See Retinoscopy.

Neglect: (Also called visual neglect, hemispatial agnosia, visual-spatial inattention, or hemi-imperception)—a passive unconscious decreased awareness of one side of the body, visual field, or other stimuli.

Neuro-ophthalmologist: A physician concerned with the neurological aspects of diseases affecting the visual system.

Neuro-optometrist: A doctor of optometry who delivers care related to visual function, or visual habilitation and rehabilitation for the neurologically challenged patient.

Noncomitant: See Comitant.

Nystagmus: Rapid involuntary movements of the eyes in a rhythmic pattern. Occlusion: The partial or total covering of one eye. Various forms include a patch

placed directly over the eye, an opaque contact lens, or translucent or opaque spectacle lenses. Total occlusion means that no image or light reaches any part of the eye. Sectoral occlusion is the covering of only part, so that only one area of the visual field is obscured. Spot occlusion is the placing of a spot, usually centrally, so that only the central part of the visual field is occluded, allowing for normal peripheral awareness. Graded occlusion is a translucent occlusion where form is degraded but light and movement can still be detected.

Ocular motor: Pertaining to eye movements, such as pursuits or saccades, or the muscle system controlling the eyes.

Oculocentric localization: The localization of objects in space with reference to the eye.

Oculomotor: Having to do with ocular motor movements, or pertaining to CN III.

Oculomotor apraxia: See Apraxia.

Optokinetic nystagmus (OKN): Subcortically mediated function based on the principle that the eyes tend to follow or track the motion of one element at a time in a steadily moving display, and make a rapid refixations to continue the pursuit.

Optic ataxia: See Ataxia.

Optic flow: Movement of image information across the retina caused when objects move in the world, or we move through the environment, used in determining one’s visual direction or heading.

Overconvergence: See Vergence. Overt attention: See Attention.

Parallax: The apparent movement in the position of an object viewed along two different lines of sight. Used to judge distances.

Paralysis (hemiplegia): Total paralysis of the arm, leg, and trunk on the same side of the body. Hemiparesis is weakness on one side of the body.

Phoria (heterophoria): The neuromuscular “resting position” of the eyes. An esophoria is a spatial mismatch where the neuromuscular posturing of the eyes is closer than the actual object of regard. An exophoria is a spatial mismatch where the neuromuscular posturing of the eyes is farther than the actual object of regard. When a heterophoria cannot be compensated by fusional vergence, strabismus ensues.

Phoropter: A refractive instrument containing lenses and prisms used to determine the amount of nearsightedness, farsightedness, and astigmatism; phoric posture and vergence; and accommodative measurements.

Photoreceptors: Sensory structures (rods and cones) that receive light stimuli. Physiological diplopia: A normally occurring event under binocular conditions,

where objects in front of and behind the object of regard are perceived as being double.

Plus lens: See Lens.

Prism: A wedge of refractive material that shifts light 1 cm per prism diopter at a distance of 1 m. The greater the power of the prism or the distance, the greater the shift in apparent movement of the object viewed through the prism. Prisms are said to be yoked when the bases in front of both eyes point in the same direction and the prism amounts are the same.

Presbyopia: A loss of elasticity of the lens of the eye, normally occurring in middle age. It causes def iciencies in accommodation resulting in an inability to focus clearly for near vision.

Pursuit: Ocular movement that holds the image of a target on the fovea, when either self, the target, or both are moving, to keep the dynamic image from blurring.

Refraction (refractive measurements): Test used to determine which lenses will provide the sharpest, clearest, and most comfortable sight, for example, with a phoropter and retinoscopy.

Retinoscopy: A technique using an instrument called a retinoscope to obtain an objective measurement of the refractive condition of the eyes, that is, determination of nearsightedness, farsightedness, and/or astigmatism. Nearpoint retinoscopy is an objective method to evaluate the focusing accuracy of the eyes relative to a target within arms length, and gives a direct measure of the accuracy and stability of focusing.

Saccade: A relatively rapid jump movement of the eyes from one place in space to another to bring images of objects of interest onto the fovea. A hypermetric saccade is one where the saccadic movement is longer or overestimates the amount of jump needed to go from one point to another. A hypometric saccade is one where the saccade is shorter, or an underestimation.

Sectoral occlusion: See Occlusion.

Spatial map: A neurological or mental representation, which may be a tactile, proprioceptive, or visual map of the body, or an auditory or visual map of the body or space. The maps may be two or three dimensional, have one or multiple frames of reference and be static or dynamic.

Spot occlusion: See Occlusion.

Stereopsis: The binocular appreciation of depth due to the retinal disparity of objects viewed from a slightly different perspective in each eye.

Strabismus: Also called “tropia” refers to the visual condition in which the visual axes of the eyes are not directed toward the same object at the same time and binocular (bifoveal) fixation is not present.

Subitize: The ability to, in a glance, make rapid, accurate, and confident judgements of number for small numbers of items. This ability appears to be innate in human, infants. The limit for adults is approximately seven objects.

Suppression: The condition where all or part of the visual field is not perceived by one eye due to inhibition of the image, rather than visual field loss. The main purpose of suppression is to secure binocular single vision where it would not be attainable otherwise.

Supranuclear: Situated or occurring superior or cortical to a nucleus in the brain. Transilluminator: A light source used to evaluate external eye health and pupillary

reflexes.

Tropia: Strabismus, a suffix indicating a misalignment of the eyes. Usually combined with prefixes such as eso, exo, hyper, hypo, or cyclo.

Underconvergence: See Vergence.

Vectogram: A vision training instrument using polarized targets that is designed to develop binocularity, expand fusional ranges, increase flexibility between the accommodative and binocular systems and match sensory systems.

Verbal apraxia: See Apraxia.

Vergence: Eye movements involving both eyes in which each eye moves in opposite directions. Vergence movements help to attain and maintain fusion at various distances. Convergence is the turning inward of the lines of sight to attain or maintain single vision while viewing objects or print at nearpoint. Divergence is the relaxation of convergence, allowing the two lines of sight to become more parallel as an object moves away. Overconvergence pertains to the posturing of the eyes closer than the actual object. Underconvergence pertains to the posturing of the eyes further away than the actual object of regard.

Version: The movement of both eyes in a coordinated and conjunctive manner. Sometimes used synonymously with pursuit and visual tracking.

Vertical imbalance: A phoric or tropic vertical misalignment of the eyes. Vestibulo-ocular reflex (VOR): A reflex eye movement in the direction oppo-

site to head movement to stabilize an image on the retina during a head movement.

Visual confusion: The condition in strabismus where each of the two foveas receives an image of a different object and the brain perceives the two objects as superimposed and in the same spatial location.

Visual midline: The perceived visual-spatial perception of straight ahead.

Visual neglect: See Neglect. Visual inattention: See Neglect.

Wolff wand: A testing instrument that is used as a target during the testing of pursuits, saccades, and convergence.

X, Y, and Z axes: Refers to meridians or axes in reference to the eyes or body. The X axis refers to a movement along the horizontal, the Y axis along the vertical, and the Z axis perpendicular to or closer or further away from the eyes or body.

Yoked prism: See Prism.

Zone of proximal development (ZPD): The difference between what a learner can do without help and what he or she can do with help. The distance between the actual developmental level as determined by independent problem solving and the level of potential development as determined by problem solving under guidance.

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MV1 P-B P-I

FIGURE 4.1 Hierarchy of visual areas. This hierarchy shows 32 visual areas. These areas are connected by linkages, most of which have been demonstrated to be reciprocal pathways. (From Felleman, D. J. and Van Essen, D. C., Cerebral cortex, 1991, 1, 1. Reprinted with permission.)

FIGURE 5.7 Pencil layout test for visual-spatial neglect.

FIGURE 6.6 Patient performing the combined weight bearing and visual egocentric localization tests.

Long wavelengths

are bent less

Prism

Short wavelengths are bent more

(B)

FIGURE 7.2 (A) This figure shows white light being broken down into the spectrum by a prism. (B) This is a demonstration of how high-contrast, square-wave, black on white text looks after passing through a prism. There is an apparent doubling with a ghost yellow image to the right and a “blurring” effect, which is produced by a blue color fringe to the left of the core of the letter and with a red fringe to the right of the black letter.

FIGURE 7.23 This shows the setup for doing the double Maddox test for cyclo rotations. Shown is the Bausch and Lomb phoropter, which allows for both Maddox rods to be rotated through 360 degrees. Here the red Maddox rod, which is before the patient’s right eye is set to “0” and is the vertical reference line. The white Maddox rod, which is before the patient’s left eye is close to 10 degrees of excyclorotation.

FIGURE 7.24 A: This gives a patient’s view of the double Maddox rod test. A The right eye sees the vertical red line, which can easily be seen to be perpendicular to the horizontal segments of the lens. B: The left eye sees the white line. Here the white Maddox rod is shown rotated, with the top to the left. The white Maddox rod is rotated until the patient subjectively reports the two lines to be parallel to each other.

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WESSON FIXATION DISPARITY CARD

FIGURE 7.29 This is the Wesson fixation disparity card. The only portion with Polaroid filters is the very center portion. The small lower arrow is seen through one channel and the colored lines above are seen through the other channel. Everything else on the card is seen by both eyes and is to act as a form of fusion lock, fusion hold or stimulus to fusion, depending on the model used by the clinician.

FIGURE 7.33 This is the center portion of the Mallett fixation disparity card as produced by Bernell. It is meant to be used in the back holder part of the Macular integrity tester. It can also be used on a Vectogram stand.

FIGURE 8.2 Wellness Protect Eyewear. (Courtesy of Eschenbach Optik of America, www. eschenbach.com)

FIGURE 8.3 FL-41 lens. (Courtesy of Brain Power Incorporated, www.callbpi.com)

The correct answer is...

FIGURE 11.3 Visual memory module from Computerized Perceptual Therapy. (Home Therapy, Inc.)

FIGURE 11.4 Visual thinking module from Computerized Perceptual Therapy. (Home Therapy, Inc.)