Final Exam Peavc Flashcards
Is defined as a condition in which the refractive status of one eye different from that the other
ANISOMETROPIA
The condition in which the refractive status is equal in the two eyes
ISOMETROPIA
A form of anisometropia in which one eye is myopic and the other is hyperopic
ANTIMETROPIA
Anisometropia is has 3 generally classified
BY TYPE
By DEGREE
BY ETIOLOGY
By type
Different amount of the same error of refraction
ANISOMETROPIA
By type
Different types of errors such as hyperopia vs myopia or spherical vs astigmatic.
ANTIMETROPIA
By degree
Difference in error totaling no more than 2.00D
LOW
ANISOMETROPIA IS DERIVED FROM THE GREEK AND MADE UP OF FOUR PARTS
AN-NOT
ISO-EQUAL
METR-MEASURE
OPIA-VISION
THE CONDITION IN WHICH THE TWO EYES UNEQUAL REFRACTIVE POWER.ONE EYE MAY BE MARKEDLY STRONGER THAN THE OTHER
ANISOMETROPIA OR ASYMMETROPIA
By etiology
This occurs because of differential growth of the eyeball of both eyes. It is hereditary in origin.
CONGENITAL ANISOMETROPIA
Created by trauma, pathology,or the results of systematic changes.
-uniocular aphakia, wrong IOL power, trauma, keratoplasty
Acquired anisometropia
It is a condition in which the refractive power of the two eyes is unequal
Absolute anisometropia
It is a type of REFRACTIVE anomaly in which although the total refraction of the two eyes is equal the components elements in each show relatively large differences. In other words the total refraction of the two eyes can be equal but the axial lenght may be different
Relative anisometropia
Type of absolute anisometropia
-simple
-compound
-mixed
-simple astigmatic anisometropia
-compound astigmatic anisometropia
One eye is normal and the other is either hypermetropic or myopic
Simple anisometropia
Both eyes are ametropic either hyperopic or myopic ;but one eye has a higher refractive error
Compound
Both eyes are ametropic, one eye is hyperopic and the other is myopic.
Mixed ANTIMETROPIA
When one eye is normal and the other has either myopic or hyperopic astigmatism
Simple astigmatic anisometropia
When both eyes are astigmatic but of unequal degree
Compound astigmatic anisometropia
CLINICAL FEATURES:
Small degree of anisometropia.
If there is a difference of more than 5D between the two eyes the patient loses binocularity
Binocular vision
If the ANISOMETROPIA IS HIGH AND THE EYES HAVE A GOOD VISUAL ACUITY,THE PATIENTS GETS INTO THE HABIT OF USING THE HYPERMETROPIC EYE FOR DISTANCE AND THE MYOPIC EYE FOR NEAR VISION
ALTERNATING VISION
If the defect is one eye is high and if its visual acuity is not good, the eye can be excluded altogether from vision and the eye becomes amblyopic
Amblyopia
A concomitant convergent squint occurs in children with the eye having the defect becoming convergent
Strabismus
Is a serious concern in newborns and young children because it can lead to amblyopia (impaired vision in one eye) with a major degree of anisometropia the brain cannot reconcile the difference in images coming from two eyes it develops a preference for the image coming from one eye suppresses the image from the other eye and in time the brain loses the ability to see the image from the suppressed eyes
ANISOMETROPIA
This is commonly referred to as lazy eye,this is when a child has reduced vision in one of their eyes because during childhood they have not used that eye adequately.
Amblyopia
This is when a person is not able to align both of their eyes under normal conditions simultaneously and is referred as being cross eyed.
Strabismus
This is when a person has double vision
DIPLOPIA
Symptoms of anisometropia
Amblyopia
Strabismus
Diplopia
Eye strain
Headaches
Sensitivity to light
Complexity in reading
Nausea
Fainting
Sheer tiredness
Their depth perception is impaired
Causes:
There are many different reasons why a person can have anisometropia
-an uneven growth in both eyes
-during cataract surgery there is miscalculation of Lens power
-inborn defects in the eye
Is a clinical test mainly used for assessing a patient’s degree of binocular vision and binocular single vision.
Worth’s fours dot test or w4LT
-Is also used in detection of suppression of either the right or left eye.
-suppression occurs during binocular vision when the brain does not process the information received from either of the eyes. This is a common adaptation to strabismus, amblyopia and aniseikonia
WORTH FOUR LIGHT TEST
When light is transmitted though the transparent portion of the eye and reflects off the retina,creating a reddish orange reflection in the eyes.
Red reflex
Because iSCREEN VISION TECHNOLOGY
Photoscreening
Photoscreening used to detect
ANISOMETROPIA
The corrective spectacles can be tolerated up to maximum difference of 4D. Higher than that,diplopia may occur.
Spectacles
Advised for higher degrees of anisometropia
Contact lens
For uniocular aphakia
IOL IMPLANTATION
For unilateral high myopia, astigmatism and HYPERMETROPIA
Refractive corneal surgery
Treatment for anisometropia
-spectacles
-contact lenses
-Refractive laser or lasik laser
-phakic IOL
-clear lens extraction with the implantation of iol
It is a binocular condition so the image in one eye is perceived as different in size compared to the image in the other eye
Aniseikonia
Unequal greek
Aniseikonia
Commented upon the probability of unequal image sizes (1864)
Donders
Discussed the possibility (1903)
C.Hess
Designed iseikonic lenses for aniseikonia
Von rohr
Condition in which the size and shape of the ocular images are equal
ISEIKONIA
Condition in which ocular images are unequal in size and shape
Aniseikonia
Lenses which correct aniseikonia and include also the correction of REFRACTIVE error
Iseikonic lenses
-eyes are gazing in a certain direction
-images are different in size
Static aniseikonia
-(OPTICALLY INDUCED) ANISOPHORIA
-EYES HAVE TO ROTATE A DIFFERENT AMOUNT TO GAZE AT THE SAME POINT IN SPACE
DYNAMIC ANISEIKONIA
-The size of one ocular image is symmetrically larger that the other.
(Symmetrical) overall
The size of one ocular image is symmetrically larger that the other in one meridian only.
i. Axis 90
ii. Axis 180
iii. AXis oblique
(symmetrical) meridional
Combination of overall and meridional is manisfested.
(symmetrical) Compound
Variation in size differ from different positions of visual field
ASYMMETRICAL
Image distortion increases progressively in both directions
PINCUSHION
Image distortion decreases progressively in both directions
Barrel
Image difference increases progressively in one direction
Prismatic
Image size remains the same but there occurs an oblique distortion of shape
OBLIQUE
Utilized the classification
David 1959
Asymmetric convergence and stereoscopic disparities exists when viewing the object located to one side
Normal
Asymmetric
-Pincushion or barrel
-ever increasing magnification towards the apex of a prsim
Symmetric
-overall
-meridional
-compound
Based on binocular space perception
Space eikonometric method
Based on directly comparing perceived image sizes between the tow eyes
Direct comparison method
The direct comparison uses as a target a cross with a small white disc at the center of a black square at its intersection
SPACE EIKONOMETER
The patient wears _________ so that each set of arrows i is seen by _______.
If the px has _________, one set of arrows will not appear aligned with the _____
Polarizing lenses
One eye,
Aniseikonia
Other
Aniseikonia:RE IMAGE
SMALLER HORIZONTAL. MERIDIONAL
Correction: R % % 90
ANiseikonia:RE image
Smaller overall
Correction: RE % O.A
One or more meridians can be measured by means of an adjustable magnifying device before one eye
Aneiseikonia
One or more meridians can be measured by means of an adjustable magnifying device before one eye
Aneiseikonia
3 commercially available direct comparison
New aniseikonia test (awaya test)
Basic aniseikonia test (,version 1)
Aniseikonia inspector (version 3)
The awaya test for aniseikonia provides a manual method to detect and calibrate the aniseikonia condition
New aniseikonia test
An easy to use windows software program to test the aniseikonia of a patient
Basic aniseikonia test ( version 1)
An easy to use windows software program to test the aniseikonia of a patient
Basic aniseikonia test ( version 1)
-A windows software program for the clinical management of aniseikonia.
-an advance aniseikonia test
-a design tool to calculate correcting prescription (aniseikonia and anisophoria correction)
Aniseikonia inspector (version 3)
Symptoms of aniseikonia
-headache
-asthenopia
-photophobia
-reading difficulty
-nausea
-nervousness
-motility
-vertigo and dizziness
-general fatigue
Symptoms of aniseikonia
-headache
-asthenopia
-photophobia
-reading difficulty
-nausea
-nervousness
-motility
-vertigo and dizziness
-general fatigue
-Unilateral or less commonly;
-Bilateral reduction of best corrected visual acuity that can not be attributed dorectly to the effect of any structural abnormality of the eye or the posterior visual pathway. Defect of central vision
AMBLYOPIA
Primarily a defect of central vision
AMBLYOPIA
Classifications of AMBLYOPIA
-strabismic amblyopia
-anisometropic amblyopia
-amblyopia due to bilateral high refractive error (isometropia)
-stimulus deprivation amblyopia
-most common form of amblyopia
-to result from competitive or inhibitory interaction between neurons carrying the nonfusible from two eyes.
-which leads to domination of cortical vision center by fixating eye and chronically reduced responsiveness to nonfixating eye input.
Strabismic amblyopia
-second in frequency
-it develops when unequal refractive error in the two eye causes the image on the on retina to chronically defocused.
-this condition is thought to result:
Anisometropia amblyopia
-second in frequency
-it develops when unequal refractive error in the two eye causes the image on the on retina to chronically defocused.
-this condition is thought to result:
Anisometropia amblyopia
Mild hyperopic or astigmatic anisometropia
1-2D mild amblyopia
1-2D-> mild amblyopia
Mild hyperopic or astigmatic amblyopia
Less than 3D usually doesn’t cause amblyopia
mild myopia anisometropia
Less than 3D usually doesn’t cause amblyopia
mild myopia anisometropia
6D -> severe amblyopia visual loss
Unilateral high myopia
Result from large approximately equal uncorrected refractive error in both eyes of young child
isometropic amblyopia
Result from large approximately equal uncorrected refractive error in both eyes of young child
isometropic amblyopia
Risk-> bilateral amblyopia
Hyperopia exceeding 5D and myopia 10 D
Risk-> bilateral amblyopia
Hyperopia exceeding 5D and myopia 10 D
Uncorrected bilateral astigmatism in early childhood may result in loss of resolving ability limited to chronically blurred meridians.
Meridional Amblyopia
