Strabismus - Fundamentals of Clinical Ophthalmology.pdf

A SIMPLE REFLEX MODEL OF NORMAL BINOCULAR VISION
●
●
●
on the centre of the macula. The parietooccipito-temporal
junction is considered an
important structure in the cortical control of
smooth pursuit. Associated pathways to the
brainstem and cerebellum are as yet unclear.
The control in this system is ipsilateral and
the pathways are deep in the parietal lobe so
that pure occipital lesions do not affect
smooth pursuit.
Optokinetic movements serve to hold images
of the visual environment steady on the centre
of the macula during sustained head rotation.
We previously referred to disturbance of
optokinetic nystagmus (OKN) in failure to
develop binocular vision. Pure OKN consists
of a slow phase following the stripes on an
OKN drum interspersed with saccades to
refixate oncoming stripes.
Vestibular movement, namely in the vestibuloocular
reflex, holds images of the visual world
during sustained head rotation. Vestibular eye
movements are based on the labyrinthinepontine
pathways and take information from
the ampullae of the semi-circular canals to
generate these ocular movements.
Vergence via the occipito-mesencephalic pathway
is a disconjugate eye movement enabling
bifoveal fixation during convergence.
References
1. Corbetta M, Miezin FM, Dobmeyer S, Shulman GL,
Petersen SE. Selective and divided attention during
visual discriminations of shape, color, and speed:
functional anatomy by positron emission tomography.
J Neurosci 1991;11:2383–402.
2. Dobson V, Teller DY. Visual acuity in human infants:
a review and comparison of behavioral and
electrophysiological studies. Vision Res 1978;18:
1469–83.
3. Norcia AM, Tyler CW, Allen D. Electrophysiological
assessment of contrast sensitivity in human infants. Am
J Optom Physiol Optics 1986;63:12–15.
4. Hubel DH, Wiesel TN. Binocular interaction in striate
cortex of kittens reared with artificial squint.
J Neurophysiol 1965;28:1041–59.
5. Shimojo S. Pre-stereoptic binocular vision in infants.
Vision Res 1986;26:501.
6. Gwiazda JB, Held R. Binocular function in human
infants: correlation of stereoptic and fusion rivalry
discrimination. J Pediatr Ophthalmol Strabismus 1989;
26:128.
7. Norcia AM, Sutter EE, Tyler CW. Electrophysiological
evidence of the existence of coarse and fine disparity
mechanisms in humans. Vision Res 1985;25:1603–11.
8. Held R, Birch E, Gwiazda J. Stereoacuity of human
infants. Proc Natl Acad Sci USA 1980;77:5572–4.
9. Naegele JH. The postnatal development of monocular
optokinetic nystagmus in infants. Vision Res 1982;
22:341.
10. Mays LP, Gamlin PD, Tello CA. Neural control of
vergence eye movements: neurons encoding vergence
velocity. J Neurophysiol 1986;56:1007–21.
11. Mays L. Neural control of vergence eye movements:
convergence and divergence neurons in the midbrain.
J Neurophysiol 1984;51:1091–107.
12. Judge SC. Neurons in the monkey midbrain with
activity related to vergence. J Neurophysiol 1986;55:
915–29.
13. Birch E, Shimojo S, Held R. Preferential looking
assessment of fusion and stereopsis in infants aged 1–6
months. Invest Ophthalmol Vis Sci 1991;32:820.
14. Brookman KE. Ocular accommodation in human
infants. Am J Optom Physiol Optics 1983;60:91–9.
15. Aslin RN. Development of binocular fixation in human
infants. Am J Optom Physiol Optics 1977;23:133–50.
16. Archer SM, Sondhi N, Helveston EM. Strabismus in
infancy. Ophthalmology 1989;96:133–7.
17. Leigh RJ, Zee DS. The properties and neural substrate
of eye movements. In: Leigh RJ, Zee DS, eds. The
Neurology of Eye Movements. Philadelphia: FA Davis,
1991.
13