O B J E C T I V E S

S T R A B I S M U S R E V I E W

M E A S U R I N G S T R A B I S M U S

T R E A T I N G D I P L O P I A

V E R G E N C E & P R I S M S

BINOCULAR SINGLE VISION

Sensory fusion = two eyes, one image

Images from each eye cortically blended into one

Advantages: Single image Stereo vision Large visual field

Prerequisites Located on corresponding retinal areas Sufficiently similar in size, brightness

and sharpness.

MOTOR FUSION

Ability to align the eyes for the maintenance of sensory fusion. Convergence Divergence

Vergence

OBSTACLES TO SENSORY FUSION

Similar images stimulating non-corresponding retinal points

Strabismus = misalignment of the visual axes

Dissimilar images stimulating corresponding retinal points Anisometropia – asymmetric refractive error Aniseikonia – different sized images Visual deprivation: unilateral cataract or other organic disease of the anterior

visual pathway

STRABISMUS

ESOTROPIA

Infantile ET Refractive/accommodative ET

EXOTROPIA

Alternating constant XT Intermittent XT

IMPLICATIONS

Suppression – brain ignores “wrong” image to avoid double vision (diplopia)

Leads to: Maldevelopment of areas of the brain responsible for binocular vision. Must clear obstacle to fusion early in childhood in order to allow development of

binocular interaction.

Maldevelopment of area of the brain responsible for recognition of visual input from the suppressed eye.

Amblyopia

Visual maturity ~ 10 years old

IMPLICATIONS

Stereoblindness: binocular vision is necessary for true stereoacutiy

People who lack fusion/binocular vision use visual cues other than stereo vision to recognize depth.

CONSEQUENCES IN ADULTHOOD

Diplopia – 1 object, 2 separated images Due to acquired strabismus – adult brain cannot easily suppress one image

Confusion – 2 objects, 2 superimposed images Due to acquired strabismus or aniseikonia

Loss of depth perception

Treatment: EOM surgery, prisms, occlusion.

DETECTION OF STRABISMUS – CORNEAL LIGHT REFLEXES

Temporal reflex, right eye= esotropia

WHAT TYPE OF STRABISMUS?

Pseudoesotropia

- Wide epicanthal folds

DETECTION OF STRABISMUS- BRUCKNER TEST

Direct Ophthalmoscope

PHOTOSCREENERSiScreen

MTI

DETECTION OF STRABISMUS- COVER TEST

ALTERNATE COVER TEST

WHAT IS A PRISM, ANYWAY?

LENS REFRACTION VS.

“FAR-SIGHTED” “NEAR-SIGHTED”

VS. PRISM REFRACTION

PRISM REFRACTION

∆

PRISM COVER TESTING

How would you hold a prism over an EXOTROPIC eye?

Base In

PRISM COVER TESTING

NEUROLOGIC IMPLICATIONS

DIPLOPIA

“GROUND IN” PRISM

FRESNEL PRESS-ON PRISM

TREATMENT OF BINOCULAR DIPLOPIA

Left Medial Rectus Disinsertion 10∆ Exotropia

CONVERGENCE INSUFFICIENCY

• Difficulty maintaining a converged eye position for near fixation.

• Small angle latent or intermittent exodeviation at near only.

• Normal binocular vision

Symptoms: eyestrain, double vision, tearing, fatigue

Strongly associated with reading and similar near activities.

CONVERGENCE INSUFFICIENCY

CONVERGENCE INSUFFICIENCY

Prism recession exercises for CI

THANK YOU!