NEUROPHYSIOLOGY OF EYEVISUAL ACUITY, ACCOMMODATION, PUPILLARY
REFLEXES, VISUAL PATHWAYS, INTRAOCULAR PRESSURE.
VISUAL ACUITY, It is the most important criterion of testing the
functional integrity of the eye Distance vision is assessed from 6
meters.
Near vision- 14 inches from the eye.
VISUAL ACUITY,V A of infants and children
Age 6-8weeks 5 months 18-24 months 2-3 years >3 years
Snellens acuity (20/600) 6/1800 (20/60) (20/40) (20/30) (20/20)
6/18 6/12 6/9 6/6
VISUAL ACUITY, V A of infants and children -Occlude one eye and
observe the behaviour -Cover test for fixation -Electroretinogram
(ERG) -Visual evoked response (VER) -Opticokinetic nystagmus
(OKN)
VISUAL ACUITY,V A of infants and children Very young and
infants
VISUAL ACUITYV A of infants and children Very young and
infants
VISUAL ACUITY,
VISUAL ACUITY,V A of infants and children (6 months old and
above)
VISUAL ACUITY,
V A of infants and children
VISUAL ACUITY,(2-3 years)
VISUAL ACUITY,
V A of infants and children (Preschool children)
VISUAL ACUITY,
VISUAL ACUITY,
Adult with snellens visual acuity chart
VISUAL ACUITY,
VISUAL ACUITY,
VISUAL ACUITY,
Near visual acuity
The pupil NEAR REACTION HAS A TRIAD OF ACTIONS. -Convergence of
eyes-Accommodation of the lenses -Miosis of the pupil
The pupil AccommodationFunction of:-inner radial muscle -outer
longitudinal muscle of cillary body *contraction of the round
muscle shortens the diameter of circle *Lens by virtue of its own
elasticity tends to assume a more spherical shape for near
objects
Accommodation The refractive power of the lens 20 diopters can
be increased up to 54 diopters in young Stress on the suspensory
ligaments change the shape of the lens contraction of circular
muscle- spherical lens relaxation of circular muscle -flat lens for
distance vision Controlled by parasympathetic supplyit increases
its refractive power capable of focusing on near objects.
Pupillary reflexes Iris increase the amount of light that enters
the eye during dull illumination decrease the amount of light that
enters the eye in bright illumination By changing the size of the
pupil
Pupillary reflexes
Pathway of the pupillary light reflex
Light & near input to EW nucleus
Presbyopia When a person is old lens grows larger and thicker
loosing its elasticity lens remains totally non-accommodating to
see near use hypermetropic correction (+ diopteric lens)
Oculo sympathetic pathway
7th nerve& lacrimal gland innervations
NEUROPHYSIOLOGY
NEUROPHYSIOLOGY
Intraocular pressure Aqueous secretion * Active secretion 80% of
aqueous production by nonpigmented ciliary epithelium via active
metabolic process *Passive secretion 20% of production
ultrafiltration,diffusion depend on BP,plasma oncotic pressure&
IOP
Intraocular pressure Factors determine the level of IOP Rate of
aqueous secretion Resistance encountered in the outflow channels
Level of episcleral venous pressure Normal IOP 10mmHg to 21mmHg
Diurnal variation high IOP in the morning lower in the
afternoon
Intraocular pressure Methods of examination tonometry
*indentation- Schiotz tonometer *applanation-Goldman -The Perkins
-The air puff -The Pulsair -The Tono pen
Noncontact pulsair Schiotz tonometer
perkins
tonopen
