CRANIAL NERVES (1-6)
1) Trace the pathway fro smell.
Olfactory receptor cells olfactory nerves olfactory bulb
Olfactory tract
Medial olfactory stria lateral olfactory stria
Septal nuclei Pyriform cortex Thalamus
Entorhinal cortex
Uncus
Amygdala
Hypothalamus limbic system Neo cortex
Limbic system
2) What are the factors that affect the visual acuity?
Optical factors : image forming mechanisms of the eye like
pupil size and refractory errors.
Retinal factors : visual acuity is maximal at fovea centralis and
less than 1/30 th of the visual acuity at fovea
in the peripheral retina.
Stimulus factors : size,color of the object and its distance from
the eye.
Intensity of illumination
Brightness
Contrast of test object against background.
Duration of exposure
3) Name the refractory errors. How do you correct them?
REFRACTORY ERRORS CORRECTION
Hyperopia (far sightedness) Convex lens
Myopia (near sightedness) Biconcave lens
Astigmatism Cylindrical lens
Presbyopia Convex lens
4) What is the clinical significance of tests for color vision?
The significance is in the identification of color blindness.
Complete absence of color perception (“anopia”):
“Protanopia“ - absence of red color perception
“Deuteranopia“- absence of green color perception
“Tritanopia“ - absence of blue color perception
“Anomaly” refers to weakness in color perception.
“Protanomaly“ - weakness in red color perception
“Deuteranomaly“- weakness in green color perception
“Tritanomaly“ - weakness in blue color perception
5) What are the other methods for testing color vision?
Edridge – Green lantern test.
Holmgren’s wools test or Yarn (spun thread) matching test.
Anomaloscope
6) Define field of vision?
The part of the external world visible to one eye in all directions
when the person fixes his gaze on one point is called as the field of
vision for that eye.
7) What is blind spot?
The optic nerve leaves the eye at a point 3mm medial to and
slightly above the posterior pole of the globe; this region is the optic
disc. Since there are no visual receptors (rods & cones) over the optic
disc; this is known as the blind spot of the eye.
8) Mention the visual field defects produced by lesions at various levels in
the visual pathway.
LEVEL OF LESION VISUAL DEFECT
1. Optic nerve Complete blindness of the affected eye.
2. Optic chiasm Bitemporal hemianopia (if lesion
is at the site of decussation of
inner fibres)
Binasal hemianopia(if lesion is on
both sides of optic chiasm
confined to the uncrossed optic
fibres)
3. Optic tract of right side Left homonymous hemianopia
4. Optic tract of left side Right homonymous hemianopia.
5. Optic radiation (partial Homonymous quadrantanopia
damage to superior or (superior or inferior) with macular
inferior fibres) sparing
6. Occipital cortex Homonymous hemianopia with macular
involvement (if large areas of occipital
cortex involved)
9) What is ptosis?
Drooping (hanging) of upper eyelid is called as ptosis.
Levator palpebrae superioris that acts as the elevator of the
upper eyelid is supplied by the facial nerve. Hence in facial
nerve palsy, ptosis occurs.
10) Trace the pathway for light reflex.
Light stimulus
Optic nerve (IInd cranial nerve)
Optic tract
Superior colliculi of both sides or
the pretectal nucleus.
via colliculonuclear fibres
Edinger westphal nucleus
Oculomotor nerve (IIIrd cranial nerve)
Ciliary ganglion
via short ciliary nerve
sphincter pupillae
