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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

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visual system examination

Visual System Examination

Dr Mahmood Fauzi Ansari MBBS MS FCLI

Asst. Professor Ophthalmology

Al Mareefa college of medicine

2013-14

before visusal exam wipe
Before Visusal exam----WIPE
  • Wash hand
  • Introduce self
  • Patient name DOB
  • Explain examination and get consent
learning objectives
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 normal schematic eye
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
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
Examples of visual acuity charts. (A) Snellen chart. (B) Landolt C chart. (C) Illiterate E chart.
slide12

Visual Acuity Grading (10th Revision of the WHO International Statistical Classification of Diseases).

1Good vision = 6/6 to 6/18.

2 Low vision = 6/24 to 3/60 (CF3m).

3Blind = 3/60 (CF3m) to PL (perception of light).

4Blind 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
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-LovieReading Card

-Point system

-M notation

near point
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
Common causes of dimness of vision
  • Refractive error, cataract, glaucoma, corneal opacity, retinal pathology, optic atrophy
refractive error
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
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
  • PresbyopiaInsufficiency of accommodation due to advancing age ( 40 years).
  • AphakiaAbsence of lens. It is a classical example of acquired high hypermetropia.
image formation
IMAGE FORMATION

ON THE RETINA

BEHIND THE RETINA

INFRONT OR BEFORE RETINA

lenses
lenses

Convex lens or plus lens

Concave or minus lens

Convex cylinder Concave cylinder

image formation with with out lens
Image formation with/with out lens

Hypermetropic eye Correction with convex lens

color sense
Color Sense
  • The normal colour vision is called “trichromatic” (red,green, blue)
  • COLOUR BLINDNESS [ACHROMATOPSIA]
  • an inability to recognisecolour.
  • Congenital—an inherited condition
  • Acquired—diseases of the macula and optic nerve,

-Red color blindness (protanopia)

-Green color blindness (deyteranopia)

-Bluecolor blindness (tritanopia)

pupillary constriction miosis

Afferent limb = Optic Nerve (SSA)

Consensual Reflex

Direct Reflex

  • Efferent limb = Oculomotor Nerve (GVE)
    • Postganglionic
    • Preganglionic
Pupillary Constriction(Miosis)

AKA Pupillary Light Reflex

Right

Left

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 ciliaris muscle

Nolte 17-38

reflex abolished if afferent or efferent is damaged

Right

Left

B

C

Reflex abolished if afferent or efferent is damaged.

Right

Left

Afferent defect

Right

Left

Efferent defect

Nolte 17-38

pupillary dilation mydriasis

Cortex, Thalamus & Hippocampus

Hypothalamus (CNS control center for ANS)

?

?

Reticular Formation

Reticulospinal fibers

Preganglionic Sympathetic Neurons in Thoracic Cord (T1-T2)

Superior Cervical Ganglion

(post-ganglionic sympathetic)

(pre-ganglionic sympathetic)

Pupillary Dilation(Mydriasis)

Decreased light to pupil

Severe pain

Strong emotional stimulus

Dilation of pupil

Horner’s Syndrome

  • Pupillary Constriction
  • Ptosis
  • Flushed & Dry Skin
  • Loss of Sympathetics
  • Lesion can be in CNS or PNS
  • Deficits ipsilateral to lesion
accommodation or near reflex

Ocular convergencePupillary constrictionLens thickening

Accommodation (or “Near”) Reflex

Shift in gaze from far to near. (contraction of pupil)

2. Three components:

AFFERENT------

Retina  Optic nerve Optic chiasmaOptic tract  Lateral Geniculate Nucleus  Optic Radiation Primary Visual Cortex 

EFFERENT-----

-ParasympatheticOculomotorNuclei OculomotorNerve 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.

physiology of vision
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
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.
lesions of the visual pathway

1. Hemianopialoss of half the field of vision of both eyes

2. Amblyopiapartial loss of sight, fixation reflexes not developed.

3. Amaurosis complete loss of sight in one or both eyes

LESIONS OF THE VISUAL PATHWAY
inspection
Inspection
  • Patient posture
  • Around bed walking aids, glasses
  • Eye inspections(Pupil size and symmetry

Strabismus, Proptosis, Ptosis, Sclera, Around eye stye, swelling, discharge etc)

visual fields

Monocular Visual Fields

Temporal Field of Left Eye

Lower Field of Left Eye

Upper Field of Left Eye

Nasal Field of Left Eye

Horizontal Meridian

Vertical Meridian

UTQ

UNQ

F

F

LTQ

LNQ

Normal Monocular Visual Field of Left Eye

Normal Monocular Visual Field of Right Eye

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)
  • 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.
perimetry
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.

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
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. Friedmannanalyser, 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
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).
slide49

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. pigmentaryretinal 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
EXAMINATION OF THE FUNDUS OCULI
  • Pupil is dilated with a suitable mydriatic, e.g. phenylephrine, tropicamide, homide or cyclopentolateand the examination of the fundusoculi is done in a dark room.
  • Atropine is preferred in children as it results in paralysis of ciliary muscle.
red reflex
RED REFLEX
  • red reflex white reflex
  • Red reflex is reduced in cataract, corneal opacity, retinoblastoma
slide53

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.

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).

optic disc
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, papillitisand 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 (braintumour) and malignanthypertension.
glaucoma
Glaucoma
  • As glaucoma advances, the cup enlarges until it occupies most of the disc area.
papilledema
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
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
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
Age-related Macular Degenetation
  • Wet form: abnormal blood vessel growth w/ hemorrhage and protein leakage
  • Dry form: Drusen

(cellular debris) build-up

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