Defects in field of vision
1. Concentric Diminution: all around the periphery the field of vision is contracted.
2. Central scotoma: central dark areas in the field.
3. Hemianopia: loss of sight in one half of a visual field.
4. Homonymous Hemianopia: Same half of field of vision of both eyes affected.
eg:- Right homonymous hem ianopia. Here right half of fields of both eyes lost i.e, temporal half of right
field of vision and nasal half of left field of vision. Seen in lesion of left optic tract.
5. Heteronymous hemianopia: Bitemporal or Binasal
Bitemporal Hemianopia: Temporal half of both field of vision affected i.e. right half of right field of vision and left half of left field of vision. Lesion at central part of optic chiasma
6. Quadrantanopia: When only one quadrant of the field of vision is affected.
Superior quadrantic hemianopia - [Lower fibres of optic radiation - Temporal]
Inferior quadrantic hem ianopia - [Upper fibres of optic radiation - Parietal]
In superior quadrantic hem ianopia upper half of field of vision is involved and in inferior quadrantic hem ianopia lower
half is involved.
c. Colour vision: This is the ability to identify colours of objects. This is tested using special colour cards. The best one used is Ishihara’s chart: It has different coloured dots forming a background, in which numeral or figure is inscribed using some different colour, which can be easily identified if colour vision is normal. A series of such charts are therefore made of different colours.
Precautions: Before showing the charts, the subject is asked to read the numerals or figures in the charts to be shown. The subject should read it in a maximum of 30 seconds time.
Ill. Oculomotor, IV. Trochlear and VI. Abducent nerves:
These three cranial nerves are tested together as they innervate the extra ocular muscles which move the eye balls.
Oculomotor: Medial, Superior and inferior recti and inferioroblique muscles, Sphincter pupillae, Ciliary
muscle, and levator palpebrae superioris.
Trochlear: Superior oblique
Abducent: Lateral rectus
They are tested as follows:
1. Movements of the eye ball:
The examiner’s index finger is held about 2 feet in front of the subject’s eyes. Ask him to follow the movement of finger in all directions with his eyes without moving the head. Elevation and depression movements in full adduction and abduction are much more informative than simply testing elevation and depression in mid position of gaze.
2. Look for the presence of strabismus (squint), diplopia, nystagmus and ptosis.
Strabismus (squint): is a condition in which the visual axis do not meet at the point of fixation. Ask whether there is any diplopia (double vision).
Nystagmus is involuntary, conjugate, often rhythmical oscillations of the eyes, which may be horizontal, vertical or rotatory.
Ptosis is drooping of the upper eyelid usually due to paralysis of levator palpebrae superioris. Ptosis can also result from cervical sympathetic paralysis.
3. Examination of the pupils
Size: Compare the size of the two pupils. first in bright light and then in dim light. Note whether the pupils are large or small and whether any irregularity is present. Slight inequality of the pupils may be present in perfectly healthy subjects.
Shape: Note whether the pupil is circular in outline, as it should be or whether its contour is irregular. 4. Pupillary reflexes: (Refer Superficial reflexes page No: 133)
V. Trigeminal Nerve: It is a mixed nerve having both sensory and motor components.
Testing the sensory functions: [Sensory distribution through Ophthalmic, Maxillary & Mandibular] Test all the general sensations over face.