Visual System Examination

Dr Mahmood Fauzi Ansari MBBS MS FCLI

Asst. Professor OphthalmologyAl 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

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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.

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)

• In patients over 40 years old, the reduced near visual acuity is one of the symptoms of presbyopia

Near Vision Charts

Types

-Reduced Snellen Acuity card Test distance at 14 inch (or 40cm)

-Jaeger Acuity Card

-Bailey-Lovie Reading Card

-Point system

-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

• Refractive error, cataract, glaucoma, corneal opacity, retinal pathology, optic atrophy

Common causes of dimness of vision

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 Concave or minus lens

Convex cylinder 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)

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Pupillary Constriction(Miosis)

Right Left

Nolte 17-38

Afferent limb = Optic Nerve (SSA)

Efferent limb = Oculomotor Nerve (GVE)PostganglionicPreganglionic

Direct Reflex

Consensual Reflex

AKA Pupillary Light Reflex

AFFERENTRetina 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 ciliaris muscle

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Reflex abolished if afferent or efferent is damaged.

Right Left

B

C

Right Left

Right Left

Nolte 17-38

Afferent defect

Efferent defect

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Pupillary Dilation(Mydriasis)

Decreased light to pupilSevere painStrong emotional stimulus

Reticular Formation

Reticulospinal fibers

Preganglionic Sympathetic Neurons in Thoracic Cord (T1-T2)

(pre-ganglionic sympathetic)

Dilation of pupil

Superior Cervical Ganglion

(post-ganglionic sympathetic)

Cortex, Thalamus & Hippocampus

? Hypothalamus (CNS control center for ANS)

?

Horner’s Syndrome• Pupillary Constriction• Ptosis• Flushed & Dry Skin

• Loss of Sympathetics• Lesion can be in CNS or PNS• Deficits ipsilateral to lesion

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Accommodation (or “Near”) Reflex1. Shift in gaze from far to near. (contraction of pupil)

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

Argyll Robertson pupil: Pupillary constriction occurs as part of the accommodation reflex, but not in response to light.

2. Three components:Ocular convergencePupillary constrictionLens thickening

Marcus-Gunn pupil—There is ill-sustained contraction of the pupil in swinging flashlight test, e.g. as in retrobulbar neuritis.

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 eyes2. 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

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Visual Fields

Definition: The entire area that can be “seen” by the patient without movement of the head and with the eyes fixed on a single spot.

Mapping of Visual Fields:• Confrontational method• Perimetry (Manual or

Automated)

Temporal Field of Left Eye

Nasal Field of Left Eye

F

Normal Monocular Visual Field of Right Eye

Normal Monocular Visual Field of Left Eye

F

Monocular Visual Fields

Blind Spot • 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.

Vertical Meridian

Horizontal Meridian

Upp

er F

ield

of

Left

Eye

Low

er F

ield

of

Left

Eye

UTQ

LTQ

UNQ

LNQ

The optic chiasma

The Normal Field of Vision

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 two-

dimensional extent of field.• Static perimetry—Non-moving stimuli presented to obtain a vertical boundary /

height of the visual field.UsesCharting 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 indiameter from periphery to centre.• At least 8 or preferably 16 meridians must be tested.

Automated perimeters utilize computers to programme visual field sequences, e.g. Baylor visual fieldprogrammer attached to standard Goldmann perimeter.

Automated perimeters, e.g. Friedmann analyser, Ouplot, Auto field perimeters Field master and Humphery field analyser

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 ophthalmoscopyObserver 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 principlei. 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 theobserver 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) build-up