Projection in Heterotropia Helen Griffiths Year 1 October 2016
The plan for today….. Projection in normal BSV – recap Types of strabismus Projection in strabismus Consequences of strabismus
Normal retinal correspondence Fovea Has the principal visual direction (PVD) Projects straight ahead Corresponds to the fovea of the other eye Nasal retina Projects temporally Nasal retina RE corresponds with temporal retina of LE Temporal retina Projects nasally
Normal binocular single vision
Normal binocular single vision
Heterotropia A condition in which one or other visual axis is not directed towards the fixation point
Types of Heterotropia Esotropia - One eye deviates nasally when both eyes are open Exotropia – One eye deviates temporally when both eyes are open
Types of Heterotropia Hypertropia - One eye is deviated upwards when both eyes are open Hypotropia – One eye is deviated downwards when both eyes are open
Projection in heterotropia Diplopia Results from stimulation of non-corresponding retinal points by a single object Confusion Results from stimulation of corresponding points in the two eyes by different objects
Esotropia
Esotropia
Esotropia Image from right eye on the right side
Esotropia Homonymous (uncrossed) diplopia Image from an esotropic eye is seen on the same side eg. Right esotropia image from right eye seen on the right hand side
Exotropia Heteronymous (crossed) diplopia Image from an exotropic eye is seen on the opposite side eg. Right exotropia image from right eye seen on the left hand side
Draw the following: Projection diagram: Right XT with normal retinal correspondence
Vertical heterotropia Hypertropia Object of fixation stimulates superior retina of the deviating eye which projects inferiorly Diplopic image from the deviating eye seen below the real target (seen by fixing eye) RE S F cerebral projection RE
Vertical heterotropia Hypotropia Object of fixation stimulates inferior retina of the deviating eye which projects superiorly Diplopic image from the deviating eye seen above the real target (seen by fixing eye) F I RE F I cerebral projection RE
Adaptations To avoid diplopia and confusion Suppression Abnormal correspondence
Suppression The mental inhibition of visual sensations Occurs more readily in children Foveal (central) suppression eliminates confusion Nasal / temporal (peripheral) suppression eliminates diplopia
Abnormal correspondence Sensory adaptation which allows strabismic patients to use both eyes without diplopia or confusion Achieve abnormal binocular single vision Further details in semester 2
Summary Diplopia results from stimulation of non-corresponding retinal points by the same object Confusion results from stimulation of corresponding points by different objects Homonymous pathological diplopia occurs in esotropia Heteronymous pathological diplopia occurs in exotropia
To do Read Von Noorden & Campos - chapter 13 p211 – 222 NB: 220 – 231 on line Library or http://www.cybersight.org/data/1/rec_docs/3285_5.85MB_Binocular_Vision_and_Ocular_Motility.pdf