Optometric Terms 4

Question 1

recovery

Answer 1

the point at which fusion is regained once broken

Question 2

re-fixation reflex

Answer 2

if you are looking to side of an object instead of directly at it (eg. if you have made an inaccurate saccade, or if a fixated target suddenly moves) it is signaled that the image of the object of regard is blurry, and not viewed straight ahead

re-fixation reflex at the fovea is stimulated as this “error” of eye position is registered, and the eye makes a corrective movement to put the image back on the fovea

reflex allows foveal re-fixation from target to target and maintenance of foveal fixation on a moving target

Question 3

reticular formation

Answer 3

essential for governing some of the basic functions of higher organisms, and is one of the oldest portions of the brain; part of the brain involved in actions such as:

1) wake/sleep cycle
2) filtering incoming stimuli to discriminate irrelevant background stimuli

3) important regulator in the ANS for respiration rate, heart rate, GI activity, and pain
4) has been shown to play a major role in alertness, fatigue, and motivation to perform various activities

have speculated that the reticular formation controls approximately 25 specific behaviors including sleeping, walking, eating, urination, defecation, and sexual activity

Question 4

reticular activating system (4)

Answer 4

1) name given to part of the brain (reticular formation and its connections) believed to be the center of arousal and motivation in mammals

2) activity of this system is a prerequisite for consciousness to occur, it is generally assumed that this system’s role is indirect and it does not, by itself, generate consciousness
(instead its unique anatomical and physiological characteristics ensure that the thalamocortical system fire in such a way that is compatible with conscious experience)

3) also involved with circadian rhythm

4) thought to be the area affected by psychotropic drugs
general anesthetics work through their effect on the reticular formation

Question 5

retinal rivalry

Answer 5

occurs when 2 very different (conflicting) images are simultaneously and separately presented to the two eyes

under normal conditions the brain will alternately suppress one image, then the other

Question 6

retinoscope

Answer 6

handheld instrument that gives the optometrist info regarding the refractive status of an eye

observation of the retinscopic reflex also provides valuable info regarding attention, visual posture, and embededness of the visual posture

Question 7

rod

Answer 7

a light-sensitive retinal receptor found in great abundance in peripheral retina

responsible for dim illumination (scotopic) seeing and motion detection

rods transform light info into chemical energy so that it can be used by the visual system

Question 8

saccades

Answer 8

relatively quick eye movement (compared to the relative slow speed of pursuit movements) during which the eye “jumps” from one target to another

thought to be mediated by the parietal lobe and the eye fields in the frontal lobe

Question 9

primary stimulus for a saccadic eye movement is

Answer 9

the location of the target

Question 10

saccades are often called a “ “ movement because

Answer 10

“catching” bc it helps the patient “catch” and bring a new target to the fovea

faster than all the other eye movements and always starts and ends with a fixation

Question 11

saccades require the patient to have the initial ability of

Answer 11

maintaining fixation

Question 12

sclera

Answer 12

tough, fibrous white outer runic (coat) of the eye, a continuation forward of the dura mater

Question 13

what plays a key role in accurate and efficient saccades

Answer 13

thereafter the concept of peripheral awareness and the ability to “calculate” the size of the jump needed to arrive at the desired target

Question 14

scotoma

Answer 14

area within the visual field in which vision is absent or reduced; may be the result of disease, neurological insult, or prolonged suppression

Question 15

sherrington’s law of reciprocal innervation

Answer 15

law that explains agonist-antagonist relationships, and monocular eye movements (auctions)

states that when a muscle contracts, its direct antagonist relaxes to an equal extent allowing smooth movement

Question 16

sight

Answer 16

relates to visual acuity, sharpness of vision, or how well a person is able to resolve letters on the snellen chart, often expressed as a snellen fraction

gives no info as to how much effort is needed to see clearly, to use both eyes together, or how much meaning is obtained from the visual input

Question 17

SILO

Answer 17

small in, large out

perceived changes induced by the intro of lenses or prisms, target separation, and after-images

Question 18

single vision

Answer 18

classified as:

1. normal: when it is bifocal and there is no manifest deviation
2. anomalous: when images of the fixated object are projected from the fovea of one eye and an extrafoveal area of the other eye (i.e. when visual direction of the retinal elements is different)
   a small manifest strabismus is therefore always present in anomalous single vision

Question 19

sphere

Answer 19

a lens with equal power in all meridians

Question 20

stereopsis

Answer 20

binocular appreciation of depth due to retinal disparity (see also 3rd degree fusion)

eyes are separated in the horizontal plane of the head and thus each eye has a slightly horizontally disparate view of the world

sensory fusion of these horizontally disparate unequal retinal images results in a three dimensional percept

Question 21

stereoscope

Answer 21

instrument designed to separate the binocular field into 2 parts, one part for each eye

when fusion is attained, a unified image is seen

it is used to explore both binocular and monocular abilities when both eyes are open

brewster (uses sphere-prisms)
wheatstone (uses mirrors)

Question 22

strabismus

Answer 22

or “squint” or “tropia” refers to the visual condition in which binocular (bi-foveal) fixation is not present

when strabismus is present (manifest) the visual axes of the eyes are not directed toward the same object at the same time

line of sight of one eye does not intersect the target being observed

Question 23

Streff syndrome

Answer 23

also called “juvenile bilateral functional amblyopia” or the “non-malingering syndrome”

bilateral condition in which there is reduced visual acuity at both distance and near in the presence of minimal refractive error and no evidence of lesion or pathology

visual acuity at near is more reduced than at distance

measured VAs may be variable, and may be better with single letters than with full chart or full line presentation

subjective complaints are usually related to near-point tasks such as reading

frequently patients will have reduced stereopsis, large accommodative lag on dynamic retinoscopy, and a reduced visual field (tubular or spiral field) that may be variable

may be difficulties with eye-hand coordination, fixation difficulties, and color vision disturbances

patient’s general behavior may seem out of step or off in timing

prior to the onset of the condition, most children have been above-average achievers- may be associated with a visual or emotional stress occurring in the child’s life

more prominent during puberty (ages 7-13), girls more frequently than boys

treatment includes low pluss lenses and/or vision therapy

Question 24

subjective angle

Answer 24

in strabismus, the point at which the patient reports a first degree fusion response or higher

in normal correspondence, the subjective angle of strabismus is equal to or within a few degrees of the objective angle

Question 25

superior colliculus (SC)

Answer 25

one of the primary processing centers for visual info received from the retina of the eye

a % of magnocellular fibers that leave the back of the eye do not go to the LGN, but instead to the SC in the mid-brain

In the SC, visual info integrates with:

• vestibular info from the semicircular canals
• proprioceptive info from muscles, tendons, and ligaments
• tactile, auditory, and other systems

It is involved in orientation, balance, and postural mechanisms, and keeps the world level.

Part of the process that tells us whether we are moving, the object of regard is moving, or both are moving. Using this info, along with info from other areas of the brain, we construct a personal 3D representation of space, with ourselves placed at the center