Visual System Examination
Dr Mahmood Fauzi Ansari MBBS MS FCLI
Asst. Professor Ophthalmology
Al Mareefa college of medicine
2013-14
Eyes are the window to the brain!
Before Visusal exam----WIPE
•
•
•
•
Wash hand
Introduce self
Patient name DOB
Explain examination and get consent
Learning objectives
• Visual Acuity:
CN II & beyond in the visual pathway
• Visual Fields:
Central & Peripheral Vision (retina to cortex)
• Ocular Motility:
(CN III, IV, VI)
• Reflexes
• Pupillary Light Reflex (CN II & III)
• Accommodation (Near) Reflex
• Fundus Examination (Retina including Optic disc): (Increased
intracranial pressure; status of blood vessels reflecting hypertension, diabetes, etc.)
• Visual Pathway: Since it is precisely organized & extends from the rostral to
caudal aspect of the hemispheres, lesions along the pathway produce specific
deficits that can aid in localizing the lesion.
4
The Spectrum of Light
400-700um
The normal schematic eye
Optic axis—The line passing through the centre of curvature of cornea and the two
surfaces of the lens, meets the retina at fovea centralis.
Nodal point—The optical centre lies in the posterior part of the lens.
Anterior focal distance—It is about 15 mm in front of the cornea.
Posterior focal distance—It is about 24 mm behind the cornea.
The average power of a normal emmetropic eye is + 58 to + 60D.
Most emmetropic eyes are approximately 24 mm in length.
What is Visual acuity?
• The resolving power of the eye used to assess and
quantify the eye’s ability to resolve varying letter sizes.
• Visual acuity is a measurement of central vision only.
• Assessment of total visual system from cornea to
occipital cortex.
• Visual acuity can be tested for both distance and near
vision.
• Distance visual acuity is the most common test.
• Distance visual acuity (DVA)
– 20ft or 6M is equivalent to optical infinity
• Near visual acuity (NVA)
– 40cm or 14 inches
Examples of visual acuity charts.
(A) Snellen chart.
(B) Landolt C chart.
(C) Illiterate E chart.
Snellens chart
Visual acuity by Hand held card
Visual Acuity Grading (10th Revision of the WHO International Statistical
Classification of Diseases).
1 Good vision = 6/6 to 6/18.
2 Low vision = 6/24 to 3/60 (CF3m).
3 Blind = 3/60 (CF3m) to PL (perception of light).
4 Blind to light - NPL (no perception of light).
Legal blindness is defined as visual acuity (vision) of 20/200 (6/60) or less in the
better eye with best correction possible.
In many areas, people with average acuity who nonetheless have a visual field of
less than 10 degrees (the normal being 180 degrees) are also classified as being
legally blind.
Near Visual Acuity
• Testing the VA at close
range (usually 40cm)
• The purpose is to detect
people with near vision
difficulties (e.g.,
uncorrected high
hyperopia,
accommodative
dysfunction)
Near Vision Charts
Types
-Reduced Snellen Acuity card Test
distance at 14 inch (or 40cm)
-Jaeger Acuity Card
-Bailey-Lovie Reading Card
• In patients over 40 years
old, the reduced near
visual acuity is one of the -Point system
symptoms of presbyopia
-M notation
NEAR POINT
• Near point is nearest possible distance at
which the near object can be clearly seen.
• It dramatically changes with age.
• It is about 8 cm at age 10 and
100 cm at age 70 yrs
50 cm at the age of 50 yrs
Common causes of dimness of vision
• Refractive error, cataract, glaucoma, corneal
opacity, retinal pathology, optic atrophy
Refractive error
• Refractive error is an optical abnormality of
eye in which image is formed either infront or
behind the retina.
• Refraction is the procedure by which any
refractive error is corrected with lenses.
• Corrective lens is needed for proper focusing.
Types of refractive errors
• EMMETROPIA -Normal optical condition of the eye.
• AMETROPIA- ERRORS OF REFRACTION
•
•
•
•
Myopia (short-sightedness or near-sightedness)
Hyperopia (Long-sightedness or Far-sightedness)
Astigmatism
Presbyopia Insufficiency of accommodation due to
advancing age ( 40 years).
• Aphakia Absence of lens. It is a classical example of
acquired high hypermetropia.
IMAGE FORMATION
ON THE RETINA
BEHIND THE RETINA
INFRONT OR BEFORE RETINA
lenses
Convex lens or plus lens
Convex cylinder
Concave or minus lens
Concave cylinder
Image formation with/with out lens
Hypermetropic eye
Correction with convex lens
Color Sense
• The normal colour
vision is called
“trichromatic”
(red,green, blue)
• COLOUR BLINDNESS
[ACHROMATOPSIA]
• an inability to recognise
colour.
• Congenital—an
inherited condition
• Acquired—diseases of
the macula and optic
nerve,
-Red color blindness (protanopia)
-Green color blindness (deyteranopia)
-Blue color blindness (tritanopia)
Ishihara Color Blindness Test Plate
Pupil
-should appear symmetric,
-constrict to light (light reflex)
Pupillary Constriction
(Miosis)
Right
Direct
Reflex
Afferent limb =
Optic Nerve (SSA)
AKA Pupillary Light Reflex
Left
Consensual
Reflex
Efferent limb = Oculomotor Nerve (GVE)
Postganglionic
Preganglionic
Nolte 17-38
AFFERENT
Retina  Optic nerve Optic
chiasma  Optic tract 
Pretectal Nucleus 
Parasympathetic Occulomotor
nucleus 
EFFERENT
 Oculomotor Nerve Nerve
to inferior oblique  Ciliary
ganglion  Short ciliary nerve
 Sphincter pupillae and
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ciliaris muscle
Reflex abolished if afferent or efferent is damaged.
Right
Right
Left
Left
B
Afferent
defect
C
Right
Left
Efferent
defect
Nolte
2917-38
Pupillary Dilation
(Mydriasis)
Decreased light to pupil
Severe pain
Strong emotional stimulus
?
Cortex,
Thalamus &
Hippocampus
Hypothalamus
(CNS control center
for ANS)
?
Reticular
Formation
Reticulospinal
fibers
Dilation
of pupil
(post-ganglionic
sympathetic)
Superior
Cervical
Ganglion
(pre-ganglionic
sympathetic)
Preganglionic
Sympathetic Neurons
in Thoracic Cord (T1T2)
Horner’s Syndrome
• Pupillary Constriction
• Ptosis
• Flushed & Dry Skin
• Loss of Sympathetics
• Lesion can be in CNS or PNS
• Deficits ipsilateral to lesion
30
Accommodation (or “Near”) Reflex
1. Shift in gaze from far to near. (contraction of pupil)
2. Three components:
Ocular convergence
Pupillary constriction
Lens thickening
AFFERENT-----Retina  Optic nerve Optic chiasma  Optic tract  Lateral Geniculate
Nucleus  Optic Radiation  Primary Visual Cortex 
EFFERENT-----Parasympathetic Oculomotor Nuclei  Oculomotor Nerve  Ciliary
ganglion  Short ciliary nerve  Sphincter pupillae and ciliaris muscle
Marcus-Gunn pupil—There is ill-sustained contraction of the pupil in
swinging flashlight test, e.g. as in retrobulbar neuritis.
Argyll Robertson pupil: Pupillary constriction occurs as part of the
accommodation reflex, but not in response to light.
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The H test
PHYSIOLOGY OF VISION
• In order to achieve clear vision, light reflected from objects within the visual field is
focused on to the retina of both eyes. The processes involved in producing a clear
image are:
Refraction of the light rays
• When light rays pass from a medium of one density to a medium of a different
density they are refracted or bent.
Accommodation of the eyes to light
• 1. Pupil (constriction for near object and bright light
•
dilatation for distant object and dim light)
• 2. Movement of the eyeballs-convergence
• 3. Lens (flattened----far object / globular----near object)
FUNCTIONS OF THE RETINA
• The retina is the photosensitive part of eye. The light sensitive cells are the rods
and cones.
• The rods are more sensitive than the cones. They are stimulated by low intensity or
dim light, e.g. by the dim light in the interior of a darkened room (scotopic vision).
• The cones are sensitive to bright light and colour. The different wavelengths of light
stimulate photosensitive pigments in the cones, resulting in the perception of
different colours. In a bright light the light rays are focused on the macula lutea
(photopic vision).
• Point of fixation—It is the area of maximum visual acuity in the normal visual field.
It corresponds to the foveola of the retina.
• Dark adaptation is the ability of the eye to adapt itself to decreasing illumination.
Visual purple (rhodopsin) is a photosensitive pigment present only in the rods. The
rate at which dark adaptation takes place is dependent upon the rate of
reconstitution of rhodopsin.
The visual nerve pathway
LESIONS OF THE
VISUAL PATHWAY
1. Hemianopia loss of half the field of vision of both eyes
2. Amblyopia partial loss of sight, fixation reflexes not developed.
3. Amaurosis complete loss of sight in one or both eyes
Inspection
• Patient posture
• Around bed walking aids, glasses
• Eye inspections(Pupil size and symmetry
Strabismus, Proptosis, Ptosis, Sclera, Around
eye stye, swelling, discharge etc)
EXAMINATION OF THE POSTERIOR
SEGMENT OF THE EYE
Visual Fields
Monocular Visual Fields
Definition: The entire area that
• Confrontational method
• Perimetry (Manual or
Automated)
Blind Spot
Lower Field of
Left Eye
Mapping of Visual Fields:
Upper Field of
Left Eye
can be “seen” by the patient
without movement of the head and
with the eyes fixed on a single
spot.
Temporal Field of
Left Eye
Nasal Field of
Left Eye
Vertical Horizontal
Meridian Meridian
UTQ
UNQ
F
LTQ
F
LNQ
Normal Monocular Visual
Field of Left Eye
Normal Monocular Visual
Field of Right Eye
•
15° to the temporal side of the visual field of each eye
•
On the horizontal meridian
•
Corresponds to the location of the optic nerve head 15° to the nasal side of the retina of each
eye.
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The Normal Field of Vision
The optic chiasma
Perimetry
• The term ‘perimetry’ is used to describe various techniques employed to
evaluate both central and peripheral visual fields using targets of various
sizes and colours.
• Two techniques
• Kinetic perimetry—A target is moved across the field to map out of the twodimensional extent of field.
• Static perimetry—Non-moving stimuli presented to obtain a vertical
boundary / height of the visual field.
Uses
Charting of the visual fields is very useful
in the diagnosis of many disease
conditions
• Glaucoma
• Retinal diseases e.g. retinitis
pigmentosa
• Follow up of laser treatment for
diabetic retinopathy
• Neurological disorders, e.g. brain
tumours, head injury, multiple sclerosis,
cerebral thrombosis,
aneurysms.
The Perimeter—(Lister’s, Goldmann’s)
It consists of a half sphere within which a spot of light can be moved
(kinetic technique).
Method—The patient is seated with his chin supported by the chin rest.
• One eye is covered by a pad.
• The other eye fixes an object placed at the centre of the arc.
• The field is recorded first with a white object 5 mm in
diameter from periphery to centre.
• At least 8 or preferably 16 meridians must be tested.
Automated perimeters, e.g. Friedmann analyser, Ouplot, Auto field
perimeters Field master and Humphery field analyser
Automated perimeters utilize computers to programme visual field
sequences, e.g. Baylor visual field
programmer attached to standard Goldmann perimeter.
Central Field (Campimetry)
• Bjerrum’s screen—It consists of a black felt or
flannel screen, 2 m in diameter on which
• central 30° of the visual field can be studied
(kinetic technique).
• 1.Electroretinogram (ERG)
• The changes induced by the stimulation of light in the resting
potential of the eye are measured by electroretinography.
• It is extinguished or absent in complete failure of function of rods
and cones, e.g. pigmentary retinal dystrophy, complete occlusion of
retinal artery, complete retinal detachment, advanced siderosis, etc.
• 2. Electro-oculogram (EOG)
• The changes in the resting current when the eyes are moved laterally
are picked up by the electrodes placed at the inner and outer canthi.
It is absent in retinal dystrophies and degenerations.
EXAMINATION OF THE FUNDUS OCULI
• Pupil is dilated with a suitable
mydriatic, e.g. phenylephrine,
tropicamide, homide or
cyclopentolate and the examination
of the fundus oculi is done in a dark
room.
• Atropine is preferred in children as
it results in paralysis of ciliary
muscle.
RED REFLEX
•
red reflex
white reflex
• Red reflex is reduced in cataract, corneal
opacity, retinoblastoma
Direct ophthalmoscopy
•
•
•
•
•
•
Helmholtz
invented
the
direct
ophthalmoscope.
Method—The surgeon looks through a
self-luminous ophthalmoscope and
directs the light upon the pupil. A
uniform red reflex or glow is seen.
Examination of the fundus is done best
at a close distance with accommodation
relaxed.
Optical principle
i. The convergent light beam is
reflected from the ophthalmoscopic
mirror
ii. The incident rays reach the retina
causing it to be illuminated.
iii. The emergent rays from the fundus
then reach the observers retina through
the hole in the mirror. The image is
virtual, erect and magnified (15 times in
emmetrope eye).
Indirect ophthalmoscopy
Observer Method—It is done in a dark
room with a convex condensing lens (+
30 D, + 20 D, +14 D) and a concave
mirror. The lens is held in between the
thumb and forefinger of the left hand. The
curved surface of the lens is towards the
examiner. The periphery of the retina can
be seen by scleral depression with the
patient in lying down position.
Optical principle
i. The convergent beam is cast by a
perforated concave mirror.
ii. The patient’s eye is made myopic by
placing a +13D, +20D or +30D convex
lens between the
observer and the patient.
iii. A real, inverted enlarged (5 times with
+13D and 3 times with + 20D lens) image
of the fundus is formed.
Optic Disc
• It is circular or oval in shape measuring 1.5 mm in diameter. It is
situated at the posterior pole of the fundus. It is pink in colour.
There is a funnel-shaped depression ‘the physiological cup’ seen in
the centre. The central retinal vessels emerge from the middle.
The normal cup : disc ratio is 0.3 or 1:2
• Size—Optic disc is large in myopia and small in hypermetropia and
aphakia.
• ii. Shape—The normal optic disc is round or oval in shape.
• iii. Margin—The margin is sharp and clearly defined
• normally and in primary optic atrophy. It is blurred in cases of
secondary optic atrophy, optic neuritis, papillitis and
papilloedema.
• iv. Colour—It is normally pink in colour. It is pale or white in cases
of optic atrophy. It is waxy yellow in retinitis pigmentosa
• v. Cupping—Pathological cupping is seen in glaucoma.
Papilloedema is seen in cases of raised intracranial tension (brain
tumour) and malignant hypertension.
Glaucoma
• As glaucoma advances,
the cup enlarges until it
occupies most of the disc
area.
Papilledema
• Indicates increased
intracranial pressure,
e.g. due to
hydrocephalus, brain
tumor, idiopathic
intracranial
hypertension or acute
intracranial hemorrhage
Proliferative retinopathy and
cotton-wool spots
Cotton-wool spots are
caused by ischemic
damage to nerve fibers
Compensatory
proliferation of vessels
Diabetes and
hypertension are the
main causes
Hypertensive retinopathy
• Arteriosclerosis with
moderate vascular wall
changes (“copper wiring”)
to more severe vascular
wall hyperplasia and
thickening (“silver wiring”)
• Arteriovenous crossing
abnormalities
(arteriovenous nicking)
• These vessel changes are
better appreciated using the
green light (makes the red
retina appear in grey tones)
Age-related Macular Degenetation
• Wet form: abnormal blood
vessel growth w/ hemorrhage
and protein leakage
Dry
form: Drusen
(cellular debris) buildup