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 .