Date post: | 16-Apr-2017 |
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Anisometropia
By kausar Ali
Student at OD
Pef university
ANISOMETROPIA
Total refraction of the two eyes is unequal .
Difference of 1 D in two eyes cause a 2 % difference in size of the two retinal images .
5% size difference / 2.5 D well tolerated .
2.5 – 4 D individual sensitivity
>4 D not tolerated
Alternate vision when one of two eyes is used at a time .
Occurs when one eye is emmetropic or moderately hypermetropic and the other myopic .
Patient uses former eye for distance vision and
And latter for near vision .
Anisometropia leads to development of squint .
Etiology :
Congenital and developmental
Acquired .
Uniocular Aphakic
Wrong power IOL
Trauma
Keratoplasty .
Clinical types :
Simple : one eye is normal other mopic /hypermatropic /astigmatism .
Compound : both eyes myopic/ hypermetropic / astigmatism /
Mixed : one eye myopic / other eye hypermetropic / astigmatism
STATE OF BINOCUAR VISION
If the refractive error difference is 4 diopters ( px fusional power) .
Uniocular vision : if the defect in one eye is higher it may be excluded from vision at early stage of life
The more emmetropic eye become amblyopic .
Alternate vision: hyperopic / myoic
Diagnosis :
Retinoscopy under cycloplegia
State of vision friend test ..
Worth four dot test .
Friend test : ( FIN green Red red )
The patient wears red green goggles and is seated at a distance of 6 meter from the chart .
Binocular single vision will read friend at once.
Uniocular vision will read either fin or red .
Alternate vision will read FIN at one time and Red other time .
Worth four Dot test:
The W4LT can be performed by examiner by two distances 33cm and 6cm .
The W4LT instrument is composed of a silver box which has 4 lights inside it . The 4 light are arranged in a diamond formation with a red light at a top two green light exact same manner and white light at the bottom .
The patient wear red and green goggles red for right eye and green for left eye.
Se all four light in absence of manifest squint normal binocular vision .
ARC sees four lights in presence of manifest squint .
See 2 red lights left eye suppression .
See 3 green light right eye suppression .
See 2 red and 3 green alternatively alternate suppression .
See 5 lights ( 2 red and 3 green ) diplopia .
Treatment :
Glasses .
Contact lenses
Keratoplasty .