8. Crude Touch
Name of test: cotton wool test.
Receptors: Free nerve endings & hair end organs.
Afferents: A delta and C fibers.
Pathway (tract): ventral spinothalamic tract (anterolateral system).
Perception: thalamus (protopathic).
Localization: not sharply localized.
Lost in: Tabes dorsalis, peripheral nerve lesion, brain stem lesion.
Better felt in: hairy skin than non hairy skin (dorsum than palm of
hands).
Adaptation: rapidly adapting (phasic)= decrease or stop discharge
upon maintained stimulation.
9.
10.
11.
12. Fast cutaneous pain
Name of test: pin prick test.
Receptors: polymodal Free nerve endings (Nociceptors).
Afferents: A delta.
Pathway (tract): Neo-lateral spinothalamic tract (anterolateral
system).
Perception: sensory cortex (epicritic).
Localization: sharply localized.
Lost in: peripheral nerve lesion, syringomyelia.
Adaptation: slowly or non adapting (tonic).
13. Slow pain
Receptors: polymodal Free nerve endings (Nociceptors).
Afferents: C.
Pathway (tract): Paleo-lateral spinothalamic tract (anterolateral
system).
Perception: thalamus (protopathic).
Localization: not sharply localized.
Lost in: peripheral nerve lesion, syringomyelia.
Adaptation: slowly or non adapting (tonic).
Occurs in: Skin, deep structures and in viscera.
14. pain
Receptors: polymodal Free nerve endings (Nociceptors).
Afferents: A delta & C.
Pathway (tract): lateral spinothalamic tract (anterolateral system).
Perception: thalamus & cortex.
Its Loss is termed: Analgesia.
Its exaggeration is termed: Hyperalgesia.
Adaptation: slowly or non adapting (tonic).
Lesion in sensory cortex: loss of fast pain only.
Lesion in thalamus: loss of fast & slow pain, then return of slow
pain only.
Lesion in peripheral nerve & syringomylia: loss of fast &
slow pain.
18. Tactile discrimination
Threshold distance: minimal distance between 2 points to be felt
as 2 separate points.
Threshold distance : 2-3 mm at lips & finger tips, 3-5 mm at
dorsum of hands, 50-60 mm at the back.
Areas with less threshold distance have: Large number of
receptors, large number of afferents, less convergence of afferents,
large cortical areas of representation.
Areas with more threshold distance have: less number of
receptors, less number of afferents, more convergence of afferents, less
cortical areas of representation.
24. Vibration sensation
Name of test: tunning fork test.
Receptors: Missner’s corpuscles (respond to frequency up to 80
cycles/sec) & paccinian corpuscles (up to 500 cycles/sec).
Afferents: A beta.
Pathway (tract): Dorsal column tract = gracile & cuneate tract
(medial lemniscus).
Perception: sensory cortex (epicritic).
Localization: sharply localized.
Lost in: peripheral nerve lesion, tabes dorsalis, brain stem & cortical
lesions.
Adaptation: rapidly adapting receptors (phasic).
25. Vibration sensation
Mixed sensations: vibration & stereognosis.
Vibration= touch & pressure.
Uses of tunning fork:
- vibration test
- hearing tests (Rinne & Weber tests).
Sites of vibration sensation: all body areas.
Tunning fork is placed over bones: for magnification of
stimulus.
26.
27.
28.
29. proprioception
(kinesthetic sensations)
Name of test: test for sense of position & test for sense of movement.
Receptors: Muscle spindle, golgi tendon organ, Ruffini end organ, in
capsules and ligaments of joints ( and Paccinian corpuscles for sense of
movements only).
Afferents: A beta.
Pathway (tract): Dorsal column tract = gracile & cuneate tract (medial
lemniscus).
Perception: sensory cortex (epicritic).
Localization: sharply localized.
Lost in: peripheral nerve lesion, tabes dorsalis, brain stem & cortical
lesions.
Adaptation: slowly adapting receptors (tonic).
30. proprioception
(kinesthetic sensations)
Static proprioception: sense of position.
Dynamic proprioception: sense of movement.
Loss of these sensation in lower limbs: sensory ataxia.
Ataxia: incoordination of voluntary movements in absence of
paralysis.
Types of ataxia:
- sensory (loss of proprioveption).
- motor (cerebellar syndrome).
31.
32.
33.
34. Stereognosis
Name of test: test for stereognosis.
Receptors: all receptors.
Perception: sensory cortex (epicritic).
Localization: sharply localized.
Lost in: peripheral nerve lesion, tabes dorsalis, brain stem & cortical
lesions.
Center: sensory association cortex (area 5,7).
This sensation requires:
- Intact sensory association cortex (area 5,7).
- Intact all sensations.
- Previous cortical experience.
35.
36.
37. Examination for ataxia
Name of test: Romberg’s test.
Result: +ve in sensory ataxia (falling down upon closure of ayes).
Sensory ataxia Motor ataxia
Tabes dorsalis Cerebellar lesion
+ve Romberg’s test no Romber’s test
Incoordination when eyes close Incoordination even with open
eyes
No tremors Kinetic tremors
Normal speech Staccato speech
Stamping gait Drunken gait
No nystagmus Nystagmus
38.
39. Gloves & stockings sensory
loss
Site of lesion: All peripheral nerves in upper & lower limbs.
(peripheral neuritis = polyneuropathy)
Affected sensations: loss of all sensations in peripheral parts of the
body.
40.
41. Jacket sensory loss
Site of lesion: around central canal of cervico-thoracic segments of
spinal cord.
Affected sensations: loss of pain & thermal sensations bilaterally in
upper limbs & upper parts of chest & back.
Name of the disease: Syringomyelia.
Pattern of sensory loss: Dissociated sensory loss, because all dorsal
column sensations + crude touch are not lost.
42.
43.
44. Hemisection of spinal cord
(Brown-sequard syndrome)
Below level of lesion on the same side:
- Sensory effects: loss of dorsal column sensations only
- Motor effects: upper motor neuron lesion, with spastic paralysis,
hyperreflexia, clonus & +ve Babiniski sign.
Below level of lesion on the opposite side:
- Sensory effects: loss of spinothalamic sensations only
- Motor effects: none
At level of lesion on the same side:
- Sensory effects: loss of all sensations (complete sensory loss).
- Motor effects: lower motor neuron lesion, with flaccid paralysis,
hyporeflexia & atrophy.
45.
46. Hemianaesthesia
Site of lesion: brain stem of opposite side.
Affected sensations: loss of all sensation in half the body.
Lesion in thalamus:
- Loss of all sensation on opposite side.
- Return of crude sensations after some time.
Lesion in Sensory cortex:
- Loss of fine sensations only on opposite side.
- No loss of crude sensations.
Lesion in Sensory association cortex:
- Loss of stereognosis (Astereognosis).
- Amorphosynthesis (forgets & ignores half of his body).
47.
48. Dermatomes
C2: skin over angle of mandible.
T2: skin over angle of sternum.
T4: skin over nipples.
T7: skin over xyphoid process.
T10: skin over umbilicus.
T12: skin over symphysis pubis.
C5: skin over deltoid muscle.
C6: skin over lateral forearm, arm & hand anteriorly and posteriorly.
C7: skin over middle forearm, arm & hand anteriorly and posteriorly.
C8: skin over medial forearm, arm & hand anteriorly and posteriorly.
49. Spinothalamic sensations:
- Pain.
- Temperature.
- Crude touch.
Any of these sensations can be used to examine integrity of
anterolateral system (spinal lemniscus).
Dorsal column sensations:
- Fine touch.
- Vibration.
- Proprioception.
- Deep pressure.
Any of these sensations can be used to examine integrity of Gracile &
Cuneate pathway (medial lemniscus)
50. Uses of cotton:
- Crude touch examination.
- Corneal reflex.
Examples of slow pain:
- Ischaemic pain.
- Pain due to spasm.
- Pain due to overdistention.
1ry hyperalgesia 2ry hyperalgesia
At site of injury Healyhy skin around injury
Receptors are facilitated Facilitation in spinal cord
Pain threshold is lowered Pain threshold is normal
Increased chemicals at site of
injury
Convergence-facilitation theory
51. Fast pain Slow pain
Acute, sharp, immediate Chronic, burning, aching
Felt after 0.1 sec Felt after 1-2 sec
Lasts for 1 sec Lasts for a long period
Occurs in skin only
Carried by A delta
Due to stimulation of mechano &
thermo sensitive pain receptors
Neospinothalamic tract
Perceived at cortex
In skin, deep tissues & viscera
Carried by C
Due to stimulation of all pain
receptors mainly the
chemosensitive
Paleospinothalamic tract
Perceived at thalamus & reticular
formation
52. Protopathic (thalamic) sensations:
- Slow pain.
- Extremes of temperature.
- Crude touch.
Epicritic (cortical) sensations:
- Fine touch.
- Fast pain.
- Vibration.
- Proprioception.
- Deep pressure.
- Fine degrees of temperature.
- Stereognosis.
77. Knee (patellar) jerk
examination
Stimulus: Tapping tendon of quadriceps (sudden stretch).
Receptors: Muscle spindle, central part of nuclear bag intrafusal
fibers.
Afferents: A alpha (primary = annulospiral afferent).
Center: AHCs of spinal segments L2, 3, 4. monosynaptic.
Efferent: Alpha motor neuron (LMN).
Effector: Contractile extrafusal skeletal muscle fibers.
78.
79.
80. Ankle jerk examination
Stimulus: sudden stretch of tendon achilis.
Receptors: Muscle spindle, central part of nuclear bag intrafusal
fibers.
Afferents: A alpha (primary = annulospiral afferent).
Center: AHCs of spinal segments S1, 2. monosynaptic.
Efferent: Alpha motor neuron (LMN).
Effector: Contractile extrafusal skeletal muscle fibers.
81.
82.
83. Tricepsexamination
Stimulus: sudden stretch of triceps tendon.
Receptors: Muscle spindle, central part of nuclear bag intrafusal
fibers.
Afferents: A alpha (primary = annulospiral afferent).
Center: AHCs of spinal segments C6,7. monosynaptic.
Efferent: Alpha motor neuron (LMN).
Effector: Contractile extrafusal skeletal muscle fibers.
84.
85.
86. Biceps jerk examination
Stimulus: sudden stretch of biceps tendon.
Receptors: Muscle spindle, central part of nuclear bag intrafusal
fibers.
Afferents: A alpha (primary = annulospiral afferent).
Center: AHCs of spinal segments C5, 6. monosynaptic.
Efferent: Alpha motor neuron (LMN).
Effector: Contractile extrafusal skeletal muscle fibers.
87.
88.
89. Planter reflex examination
Stimulus: deep scratch to sole from below upwards.
Receptors: Superficial receptors
Afferents: afferents enter the spinal cord through posterior horn.
Center: AHCs of spinal segments S1, 2.
Efferent: Alpha motor neuron (LMN).
Effector: Planter flexion of all toes.
90. Planter reflex
Normal:
- Normal person.
+ve Babiniski sign:
= Dorsiflexion of big toe & fanning of lateral 4 toes.
- UMNLArea 4 lesion.
Lost planter reflex:
- LMNL in S1-2.
Pseudo +ve Babiniski sign:
- Deep sleep & deep coma.
- Hypoglycemia & general anaesthesia.
- Infants below 1 year (pyramidal tract not mylinated).
Partial +ve Babiniski sign:
- Area 4 lesion (dorsiflexion of big toe), Area 6 lesion (fanning of lateral
toes).
91. Superficial reflexes
Stimulus: scratch to skin.
Receptors: Superficial receptors
Afferents: afferents enter the spinal cord through posterior horn.
Center: AHCs of spinal segments ………..
Efferent: Alpha motor neuron (LMN).
Effector: Contraction of muscle.
Lost in: UMNL & LMNL affecting their pathways.
Abdominal reflexes: T7- T12.
Cremasteric reflex: L1-2.
92. Corneal reflex
Stimulus: Touching cornea from its side by a piece of cotton.
Receptors: irritant receptors
Afferent: opthalmic branch of 5th cranial nerve.
Center: superior colliculus of midbrain
Efferent: 7th cranial nerve.
Response: Bilateral blinking.
Importance: test the integrity of 2 cranial nerves at the same time.
95. Importance of deep reflex
examination
- Give idea about state of spinal cord & higher centers.
- Give idea about muscle tone.
- Localization of site of lesion in CNS.
97. Muscle tone
Definition: continuous, rhythmic, alternating contraction of skeletal
muscle during rest.
- It is muscle to muscle reflex.
Stimulus: Maintained muscle stretch during rest.
Receptor: central part of nuclear chain intrafusal fibers.
Afferent: primary (Ia) & 2ry (II).
Center: AHCs of spinal cord.
Efferent: alpha motor neuron (LMN)
Effector: extrafusal contractile fibers.
Response: maintained contraction.
98. Muscle tone
Functions:
- Maintains upright posture.
- Maintains postural background for voluntary movements.
- Maintains venous & lymphatic return.
- Maintains body temperature constant.
- Maintains viscera in position.
Clonus: Rhythmic oscillations occurs when a hypertonic muscle is
subjected to sudden maintained stretch.
- It is due to cycles of stretch-inverse stretch reflexes.
- It occurs in: patellla, ankle.
99. Facilitated Inhibited
- Area 4.
- Neocerebellum.
- Area 6.
- Paleocerebellum.
- Vestibular nucleus. - Red nucleus.
- Facilitatory reticular formation. - Inhibitory reticular formation.
- Caudate nucleus. - Putamen & globus pallidus.
Tendon jerks & Muscle tone
Hypertonia without hyperreflexia: parkinsonism.
100. UMNL LMNL
- Lesion from motor cortex
till the spinal cord.
- Lesion from spinal cord
till the muscle.
- Generalized, contralat.
Paralysis.
- Localized, ipsilat.
Paralysis.
- Hyperreflexia & clonus. - Hypo or Areflexia.
- Loss of superficial
reflexes below lesion level.
- Loss of superficial
reflexes at lesion level.
- +Ve Babiniski - Only when S1-2 affected.
- Spasticity of antigravity
muscles + clasp knife.
- Flaccidity of affected
muscles.
- Minimal disuse atrophy. - Marked atrophy.
113. Coordination tests
Tests:
- Finger to finger test.
- Finger to nose test.
- Finger to doctor’s finger test.
- Arm pulling test.
- Wrist slapping test.
- Heel to knee test.
- Tests for rapid alternating movements.
- Tests for gait, speech, nystagmus & tremors.
These tests should be done with open eyes & then with
closed eyes.
124. Examination of III, IV & VI
Tests:
- Test eye movements by extraocular muscles.
- All extraocular muscles are innervated by occulomotor except:
- Lateral rectus by abducent nerve.
- Superior oblique by trochlear nerve.
- Occulomotor lesion produces:
- Paralytic divergent squint.
- Dropping of upper eye lid.
- Dilated fixed pupil.
- Loss of accomodation to near object.
125. Effects of atropine eye drops
- Loss of parasympathetic actions of occulomotor:
- Loss of accomodation.
- Dilated pupil.
- Intact somatic actions of occulomotor:
- No paralysis of extraocular muscles supplied by oculomotor nerve.
126.
127.
128.
129.
130.
131.
132.
133.
134.
135.
136.
137. Examination of V nerve
- Sensory Tests:
- Sensations of face.
- Corneal reflex.
- Motor Tests:
- Temporalis & masseter muscles.
- Pterygoid muscles.
- Jaw jerk.
- Trigeminal lesion produces:
- Loss of corneal reflex.
- Loss of sensations from corresponding half of face.
- Weakness of muscles of mastication.
- Exaggerated jaw jerk (in bilateral UMNL).
138.
139.
140.
141.
142.
143.
144.
145.
146.
147.
148.
149. Examination of VII nerve
- Sensory Tests:
- Sensations of taste in anterior 2/3 of tongue.
- Motor Tests:
- Frontalis & orbicularis oculi muscles.
- Orbicularis oris & buccinator muscles.
Upper part of facial nucleus:
- Has bilateral pyramidal tracts innervation. So, upper part of face is
not affected in UMNL.
lower part of facial nucleus:
- Has contralateral pyramidal tracts innervation. So, lower part of face
is affected in UMNL.
In LMNL of facial: upper & lower parts of face are affected.
150. UMNL LMNL
- No effect (sparing) of upper
part of face.
- Paralysis of upper & lower
parts of face.
- Effects are opposite to side of
lesion.
- Effects are to the same side of
lesion.
151.
152.
153.
154. Examination of IX & X nerves
- Examination of uvula:
- Normally, it is central in position and moves up & down while being
central.
- If uvula is deviated:
- Uvula deviates to the healthy side, then the other side has unilateral
lesion.
155.
156.
157.
158.
159. Examination of XI nerve
- Examination of:
- Sternomastoid muscle.s
- Trapezius muscles
160.
161.
162.
163.
164.
165.
166. Examination of XII nerve
Examination of TONGUE.
- In bilateral lesion of XII nerve:
- Patient can not protrude his tongue out of mouth.
- In unilateral lesion of XII nerve:
- Tongue is deviated to paralyzed side.
- Look at the paralysed side:
- Atrophy & fasciculations = LMNL.
- Small spastic tongue = UMNL.
171. Pupillary light reflex
Stimulus: exposure of one eye to light.
Receptors: rods & cones.
Afferents: optic nerve of stimulated eye → crossing of nasal fibers
in optic chiasma to opposite side & continuation of temporal fibers
without crossing → optic tract → fibers leave optic tract from posterior
part.
Center: pretectal area which stimulates EWN of both sides.
Efferent: occulomotor nerve bilaterally.
Effector: constrictor pupillae muscles bilaterally.
Response: bilateral miosis.
172. Pupillary light reflex
Importance:
- Protection of retina from excess light.
- Regulation of amount of light entering eyes.
- Diagnosis & localization of lesions in visual pathway.
Types of pupillary light reflex:
- Direct LR: constriction of pupil of the stimulated eye.
- Indirect LR (consensual): constriction of pupil of the unstimulated
eye.
Causes of indirect light reflex:
- Crossing of nasal fibers of the stimulated eye in optic chiasma.
- The stimulated pretectal area stimulates EWN bilaterally.
173. Pupillary light reflex
Lesions:
- Amauratic pupil: pupil of blind eye (optic nerve lesion) that gives no
response to direct light but constricts normally indirectly when the
normal eye is exposed to light.
- Hemianopic pupil: pupil of hemianopic eye (lesion in optic chiasma
centrally or peripherally, lesion in anterior part of optic tract) that
gives no response to light when it comes from its blind half of field,
but gives normal responses (bilaterally) when light comes from its
normal half of field.
- Normal light reflex: in normal persons, lesions in posterior part of
optic tract, in LGB, in optic radiations, in visual cortex.
- Argyll-Robertson pupil (light-near dissociation): no response in light
reflex, but normal response in near response. Occurs in tabes
dorsalis due to bilateral damage of pretectal areas of midbrain.
177. Near response
Stimulus: blurred image of a near object.
Receptors: rods & cones.
Afferents: optic nerve → crossing of nasal fibers in optic chiasma to
opposite side & continuation of temporal fibers without crossing → optic tract
→ LGB → optic radiations → visual cortex (17) → visual association cortex
(18, 19) → frontal eye field area (8).
Center: superior colliculus which stimulates EWN.
Efferent: occulomotor nerve bilaterally.
Effector: constrictor pupillae muscles, ciliary muscles & medial recti
muscles.
Response: - bilateral miosis.
- bilateral medial convergence.
- bilateral accomodation.
178. Near response
Importance: to see near objects clearly.
Miosis (by constrictor pupillae muscles):
- Prevents falling of light on peripheral parts of lens → prevents
spherical & chromatic aberration.
Medial convergence (by medial recti):
- Allows falling of the image of the near object on corresponding parts
of retinae of both eyes → prevents diplopia (double vision).
Accomodation (by ciliary muscles):
- To increase diopteric power of the lens → strong refraction and
focusing of diverging light of near object on the retina.
179. Near response
Accomodation occurs by:
- Contraction of ciliary muscles →
- Relaxation of suspensory ligaments →
- Decrease pull on lens capsule →
- Increase convexity of anterior surface of lens.
Prove:
- Prkinje-Sanson image.
Power of the resting lens: 20 diopters.
Power of maximally accomodating lens: 34 diopters.
power of accomodation = Difference between maximal power
& resting power.
180. Near response
Far point (punctum remotum):
- Farest point from eyes at which an object is seen clear without
accomodation.
- = 6 meters & more.
Near point (punctum proximum):
- Nearest point from eyes at which an object is seen clear with
maximal accomodation.
- = 20 cm in young adults and more than that with aging.
Presbyopia: decrease power of accomodation by aging due to
decrease lens elasticity.
- Far point: no change.
- Near point: receeds away from eyes (becomes more).
- Correction: convex lens for near vision.
181. Near response
myopia hypermetropia
Focusing of parallel light infront of
retina without accomodation.
Focusing of parallel light behind
retina without accomodation.
- Axial: long eye.
- Refractive: strong cornea
(keratoconus) or lens (spasm of
ciliary muscle).
- Axial: short eye.
- Refractive: weak cornea
(cornea plana) or lens (paralysis
of ciliary muscle).
- Far point: less than normal.
- Near point: less than normal.
- Far point: uses accomodation
to see it.
- Near point: more than normal.
Correction: concave lens. Correction: convex lens.
Astigmatism: irregularity in corneal or lens surfaces → unequal
refraction of light.
190. Visual field examination
Definition:
- The maximal part of the external environment seen by the fixed
eyes.
Normal boundaries:
- Temporal: 90 Nasal: 60
- Upper: 60 Lower: 70
Projection:
- Nasal field: projects on temporal half of retina.
- Temporal field: projects on nasal half of retina.
Tests:
- Confrontation test.
- Perimeter.
191. Visual field examination
Uses of perimeter:
- Examination of visual field.
- Diagnosis of scotoma (localized area of blindness within the normal
visual field).
- Diagnosis of optic atrophy (generalized contractions in visual field).
- Diagnosis & localization of lesions in visual pathway.
192. Visual field examination
Lesions that produce hemianopia:
- Lesion in optic chiasma.
- Lesion in optic tract.
- Lesion in optic LGB.
- Lesion in optic radiations.
- Lesion in visual cortex.
Lesions that produce homonymous hemianopia:
- Lesion in optic tract.
- Lesion in optic LGB.
- Lesion in optic radiations.
- Lesion in visual cortex.
193. Visual field examination
How to differentiate between Lesion in optic tract &
lesion in optic radiation (both produce homonymous
hemianopia?
By light reflex.
- Lesion in anterior part of optic tract → hemianopic pupil.
- Lesion in optic radiations → normal light reflex.
Why the lesion in visual cortex produces no effect on
macular vision (macular sparing)?
Because the macula has:
- Bilateral representation.
- Large cortical areas of representation.
- Area of representation has double blood supply.
194. Visual field examination
Area 17 Area 18,19
Perception of image without
understanding.
Understand the meaning of visual
impulses.
Perception of colors. Relate visual sensation to other
sensations.
Localization of object in space. If the image of the object is not
clear → impulses to area 8 to
produce accomodation reflex.
Fusion of images from both eyes
to give one mental impression
Lesion: crossed homonymous
hemianopia with macular sparing.
Lesion: agnosia (can not
understand the meaning of visual
information).
195.
196.
197.
198.
199.
200.
201.
202.
203.
204. Fundus examination
Instrument: ophthalmoscope; the instrument used in fundus
examination.
It consists of:
- Source of light.
- Mirror.
- Set of lenses.
Uses of ophthamoscope:
- Fundus examination.
- Diagnosis of errors of refraction.
- Diagnosis of intracranial tumors & high intracranial tension.
- Diagnosis of systemic disease (DM, Hypertension).
205. Fundus examination
Fundus: part of retina seen by ophthalmoscope .
Comment on:
- Macular region. - Retinal vessels.
- Optic disc. - Retina proper.
1) Macular region:
- Oval area, red-yellow in color and has a whitish center.
- Located at the center of retina (3 mm temporal to optic disc).
- Area of sharpest vision.
- Its receptors are mainly cones.
- Bilaterally represented in the visual cortex.
206. Fundus examination
2) Optic disc:
- Site of exit of optic nerve & entry of retinal vessels.
- Round, well defined borders, 1.5 mm in diameter, 3 mm to the
nasal side from the center of retina, pale pink in color, has
physiological cup (depression) in its center.
- No photoreceptors in this area (physiological blind spot).
- Diagnosis of intracranial tumors & high intracranial tension.
Abnormalities:
- Obliteration of its cup OR oedema of optic disc = brain tumor &
high intracranial tension.
- Very pale & small contracted disc = optic atrophy & glucoma.
207. Fundus examination
3) Retinal vessels:
- Retinal artery & vein in the center of optic disc.
- Both give many upper & lower branches.
- Arteries are narrow & brighter in color than veins.
Abnormalities:
- Dilated & tortious vessels = hypertensive retinopathy.
4) Retina proper:
- It is transparent, but appears pink (color of choroidal vessels).
Abnormalities:
- Capillary microaneurysms with hemorrhages & exudates = diabetic
retinopathy.
208.
209.
210. Visual acuity examination
Definition:
- The ability of eyes to detect details & boundaries of objects.
- It is the function of cones.
The emmetropic eye:
- Can differentiate between 2 points at a distance of 6 meters.
- Light rays coming from these 2 points make an angle of 1 minutes
(1/60 degree) in the nodal point AND
- Stimulate 2 cones in the retina separated by at least one
unstimulated cone → 2 separate images in the visual cortex.
211. Visual acuity examination
Maximal acuity occurs in fovea centralis because:
- Receptors are only cones (high acuity).
- 1:1 connection (no convergence).
- Highly developed pigmented epithelium (absorption of extralight).
- Light falls on receptors directly.
Tests:
- Landolt’s chart.
- Snellen’s chart.
212. Visual acuity examination
What is meant by 6/24:
- It means that: while the patient is sitting at 6 meters distance from
the char, the last raw he sees clearly is the raw of circle that can be
seen clearly by a normal person at a distance of 24 meters.
What the next steps in visual acuity examination:
- If he can not see clearly any raw at 6 meters distance, move him
closer to the chart to become at 5 meters distance, then 4 meters, 3
meters, 2 meters and finally 1 meter.
- If he can not see clearly at 1 meter distance, stand at 50 cm distance
from the patient and ask him to count your fingers.
- If he can not, go closer and detect if he can perceive your hand
movement in front of his eyes or not.
- If he can not, detect if he can perceive gross light or not.
213.
214.
215. Color vision examination
Definition:
- The ability of eyes to discriminate colors.
Tests:
- Ishihara test charts.
- Colored wool test.
Color vision:
- Function of cones.
- 3 different cones are present in retina (red, green & blue cones),
corresponding the 3 primary colors.
- Any other color can be perceived by simultaneous & differential
stimulation of the 3 cone systems.
216. Color blindness
Definition:
- The inability of eyes to discriminate colors.
Cause:
- Genetic: x linked recessive, 8% in males & 0.4% in females.
- Acquired: 2ry to eye diseases, in one or both eyes.
Types:
1) Trichromatic (anomaly): one cone system is weak, can see deep
colors but pale colors can not be discriminated.
2) Dichromatic (anopia): one cone system is absent, deep & pale colors
are perceived as different colors.
3) Monochromatic (anopia): 2 cone systems are absent.
(Red= prot) (geen= deutr) (blue=trit)
217.
218.
219.
220.
221.
222.
223. Hearing examination
Deafness:
- Partial or complete hearing loss.
Types & causes:
1) Conductive deafness:
- Obstruction of external ear by wax or foreign bodies.
- Rupture of tympanic membrane.
- Otitis media.
- Otosclerosis.
1) Nerve (sensori-neural) deafness:
- Injury of cochlear nerve.
- Degeneration of hair cells by drug toxicity.
- Tumor affecting inner ear.
224. Hearing examination
Tests:
- Rinne & Weber tests (qualitative)
- Audiometry (quantitative & qualitative).
1) Rinne test:
Compares air conduction to bone conduction in one ear.
- Rinne +ve = Normal: air conduction is better than bone conduction.
- Rinne –ve = Conductive deafness: bone conduction is better than air
conduction
- Reduced Rinne +ve (pseudo +ve) = nerve deafness: air conduction is
better than bone conduction, but both are not heard well.
225. Hearing examination
2) Weber test:
Compares bone conduction in both ears at the same time.
- Normal: sound is heard with equal intensity in both ears.
- Conductive deafness: sound is heard louder in the diseased ear (due
to absence of the sound that comes through air that normally masks
the sound comes through bones.
- Nerve deafness: sound is heard louder in the normal ear.
Other tests:
- Watch test: sound is heard at a shorter distance in the diseased
ear.
- Scwabach test: compares bone conduction of the patient with
that of the doctor.
- Audiometer.
