VISUAL FIELD DEFECTSOCULAR REFLEXES

Clinical correlation

• Loss of vision in one half of the visual field (Rt or Lt) is termed as hemianopia.

• Homonymous hemianopia: Loss of vision in the same halves of the visual field.

• Heteronymous Hemianopia: Loss of vision in the different halves of the visual field.

3

Pupillary Light Reflex• When the amount of

light entering the eyes increases, the pupils constrict.

• Functions to help the eye adapt extremely rapidly to changing light conditions.

• Direct light reflex: same pupil constricts

• indirect (consensual) light reflex: pupil of the opposite eye constricts

Two type of light reflex

• Direct light reflex• Constriction of pupil of the eye in which the light is

directed is called direct light reflex

• Consensual light reflex (In direct)• Constriction of pupil of the other eye is called

consensual light reflex

Pathways of direct and indirect light reflexes (v.imp.)

BY Muhammad Ramzan Ul Rehman Nishtar Ken

14

Pupillary light reflexDirect

Consensual

Extrinsic Eye Muscles

Inferior rectus Inferior oblique

Medialrectus

Superiorrectus

Superioroblique

Lateralrectus(cut)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

• Superior rectus• Rotates eye up and medially

• Inferior rectus• Rotates eye down and medially

• Medial rectus• Rotates eye medially

16

Extrinsic Eye Muscles

Inferior rectus Inferior oblique

Medialrectus

Superiorrectus

Superioroblique

Lateralrectus(cut)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

• Lateral rectus• Rotates eye laterally

• Superior oblique• Rotates eye down and laterally

• Inferior oblique• Rotates eye up and laterally

17

Medial and lateral recti move eyes side to side

Superior and inferiorrecti move eyes upand down

Superior and inferiorobliques rotate the eyes

Extra ocular musclesNerve Supply

Figure 51-7; Guyton & Hall 18

Accommodation• It is the ability of the

eye to keep the image focused on the retina (as the distance between the eyes & the object varies)

19

AccommodationAccommodation

NEAR RESPONSE or accomodation for near vision

• The three components of near response are: 1. accommodation, 2. convergence of the eyeballs & 3. Pupillary constriction

Pathway of Convergence Reflex

ACCCOMODATION REFLEX• When the eyes are

focussed from a distant to near object, three reactions take place

• 1. Constriction of pupils• 2. thickening of lens due to

contraction of ciliary muscles

• 3. Convergence of both eye balls

These three reactions together constitute Accommodation or near reflex

Accommodation reflex

Visual Acuity• Acuteness or clearness of vision

• It is the degree to which the details and contours of objects are perceived

• It is defined in terms of the minimum separable (shortest) distance by which two lines can be separated and still be perceived as two lines

• Thus the minimum separable in a normal individual corresponds to a visual angle of about 1 minute

• Clinically Snellen’s charts are used to determine visual acuity

METHOD FOR STATING VISUAL ACUITY

• Chart for testing eyes consists of letters of different sizes placed 20 feet ( 6 meters) away from the person being tested.

• Person is said to have normal vision if he can see the letters from the distance of 20 feet or 6 meters. so he have vision of 20/20 or 6/6

26

CONFRONTATION METHOD TO TEST THE FIELD OF VISION

27

perimetry

Lister’s perimeter• Perimetry maps and

quantifies the visual field, especially at the extreme periphery of the visual field.

28

GOLDMAN’S PERIMETRY

29

Physiologic blind spot: In all perimetry charts, a blind spot caused by lack of rods and cones in the retina over the optic disc is found about 15 degrees lateral to the central point of vision, as shown in the figure.

• ScotomaA blind spot in any other portion of the visual field

30