4. When the refractive power in two eyes is not equal , so that the focus
formed are also different in two eyes, this condition is called
ANISOMETROPIA.
The optical condition of the eyes, where both the eyes have equal
refractive power is called as ISOMETROPIA.
Small amount of anisometropia is very commonly seen in population,
but it has no visual concern.
The difference of 1D in refractive power in two eyes will produce
unequal size and image on the Retina of 2% only.
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5. A difference up to 5% in retinal images of the two eyes is well tolerated.
A difference between 2.5 and 4.0 D can be tolerated depending upon the
individual sensitivity.
If the difference more than 4 D in both eyes is not tolerated and produce
symptoms.
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6. Anisometropia can be classified in two types-
1:- ETIOLOGICAL TYPES
2:- CLINICAL TYPES
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7. A:- CONGENITAL or DEVELOPMENTALANISOMETROPIA:-
It is hereditory in origin.
It’s occurs due to disproportional growth between two eye balls.
B:- ACQUIRED ANISOMETROPIA:-
It can be caused by:
Uniocular keratoplasty.
Trauma of the eye.
Uniocular traumatic injury.
Improper refractive surgery.
Asymmetric age change.
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9. In this case one eye affected with refractive
error (i.e. Myopic or Hypermetropic),
while the other eye is normal
(Emmetropic).
Depending on the type of refractive error
present in affected eye, it can be :
Simple hypermetropic.
Simple myopic.
Simple astigmatism.
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Normal eye
Myopic eye
Hypermetropic eye
10. In this case, both the eyes have same type
of refractive error i.e. Myopia, hypermetropia
or astigmatism, but there is significant
difference in their refractive power.
It may be :
Compound myopic
Compound hypermetropic
Compound astigmatism.
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Myopic eye
Myopic eye
11. In this case, one eye is myopic and the
other is Hypermetropia. This is also
Antimetropia.
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Myopic eye
Hyperopic eye
12. When one eye is normal and the other has
either simple myopic or hypermetropic
astigmatism
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Normal eye
Simple myopic
astigmatism
13. When both eyes are astigmatic but of unequal
degree.
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Simple myopic
astigmatic
Simple myopic
astigmatic
14. In this case, one eye has hypermetropic
astigmatism and the other has myopic
astigmatism.
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Simple myopic
astigmatic
Simple hyperopic
astigmatic
15. Three possibilities exist as follows:
1: Binocular single vision is present in small
degree of anisometropia (<3 D)
2: Uniocular vision, When refractive error in
one eye is high degree.
3: Alternate vision occurs when one eye is Emmetropic
or moderately hypermetropic and the other myopic,
then hypermetropic eye is used for distant vision and
myopic for near.
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16. Eye strain
Headache
Disturbance of binocular vision
Suppression of one eye
Difficulty in fixation
Diplopia occur if the difference exceeds 5%
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18. 1- F, I, N are written in GREEN and
R, E, D IN RED COLOR.
2- It is in corporated in Snellen’s vision box.
3- The patient is to sit a distance of 6 m after
wearing diplopia goggles with red glass in
front of right eye and green in front of the
left eye and asked to read the latters.
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F R I E N D
19. 1- Binocular single vision- patient will read
FRIEND at once.
2- Uniocular single vision- patient will read
either F I N or R E D.
3- Alternate vision- the patient will read F I N
at one time and R E D at other time.
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F R I E N D
Binocular single
vision
R E D or FIN
Uniocular vision
20. 1- For this test, the patient wear goggles with
red lens in front of the right eye and green
lens in left eye and views a with four lights:
one RED, two GREEN, one WHITE.
2- The patient is made to sit at a distance of 6 m.
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21. 1- Normal binocular single vision- if the patient sees all
the four lights in the absence of manifest squint.
2- In abnormal retinal correspondence, the patient see
four light even in the presence of manifest squint.
3- If the patient sees only two red lights, it indicates LEFT
SUPRESSION.
4- If the patient sees only three green light, indicate RIGHT
SUPRESSION
5- When patient sees the three green lights and two red
lights, alternately, it indicates presence of
ALTERNATE SUPRESSION
6- If the patient sees the five lights (two red and three green),
indicate DIPLOPIA.
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DIPLOPIA
22. 1- SPECTACLES: The corrective glasses can be prescribed
in anisometropia up to a difference of 4 D, because difference
of >4D will not be tolerated by patient and will produce diplopia.
2- CONTACT LENSES are advised for higher degrees of
anisometropia.
3- ANISOMETROPIC SPECTACLES are special type of
spectacles used to treat anisometropia.
4- OTHER MODALITIES OF TREATMENT
a) IOL implantation for Uniocular aphakia.
b) Refractive corneal surgery for unilateral myopia ,
astigmatism and Hypermetropia.
c) Phakic refractive lenses are good option for refractive error
of 4-10 D.
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