Functional Tests

Color Vision

Ability of the eye to discriminate between colors excited by lights of different wavelengths.

L-Cones

60% of all cones, most sensitive to longer wavelengths, perceived by brain as Red.

M-Cones

30% of all cones, most sensitive to medium wavelengths, perceived by the brain as Green.

S-Cones

10% of all cones, most sensitive to short wavelengths, perceived by the brain as Blue.

Red

60% of all cones, most sensitive to longer wavelengths, perceived by brain as?

Green

30% of all cones, most sensitive to medium wavelengths, perceived by the brain as?

Blue

10% of all cones, most sensitive to short wavelengths, perceived by the brain as?

Long-Wavelength/Red Cones

L-Cones?

Medium-Wavelength/Green Cones

M-Cones?

Short-Wavelength/Blue Cones

S-Cones?

Monochromacy

Total color blindness (very rare).

Dichromacy

One of three color pigment is absent.

Protanopia

Red photoreceptors absent.

Deuteranopia

Green photoreceptors absent.

Tritanopia

Blue photoreceptors absent.

Protanopia and Deuteranopia

Red-Green confusion.

Tritanopia

Blue-Yellow Confusion

Trichromacy

Color deficiency rather than loss.

Protanomaly

Red color deficiency

Deuteranomaly

Green color deficiency

Tritanomaly

Blue color deficiency (rare, not hereditary)

Monocular

Checking for acquired CVD, detection of asymmetric eye conditions.

Binocular

Checking for hereditary CVD, occupational qualifications.

1st Plate

This plate in Ishihara is for demonstration and malingerers.

Transformation Plate (2-9)

This plate in Ishihara is for a number seen by a colour normal appear different to color deficient subject.

Vanishing Plate (10-17)

This plate in Ishihara is for a a number is seen by a color normal but cannot be seen by a color deficient subject.

Hidden-Digit Plates

This plate in Ishihara is for a normal person does not see a figure while a CVD will see the figure.

Diagnostic Plates

This plate in Ishihara is for a normal seen by normal subjects, CVD one number more easily than another.

• Protans only see the number on the right side.

• Deutans only see the number on the left side.

Diagnostic Plates in Ishihara Plates can be seen by normal subjects? (2)

• Number of plates read correctly:

  • 14 Plates – Seeing 12 and up plates indicated normal.

  • 24 Plates – Seeing 13 and up plates on the first 15 plates indicates normal.

  • 38 Plates – Seeing 17 and up plates on the first 21 plates indicates normal.

Recording of Ishihara Plates? (3)

Stereopsis

It refers to the brain's ability to merge slightly different images from each eye into a three-dimensional image.

Stereopsis

This process relies on the binocular disparity.

Stereopsis

The slight difference in images seen by each eye is due to their horizontal separation.

Stereopsis

The brain processes these disparities to perceive depth allowing us to navigate our environment with spatial awareness.

Light seen by both eyes.

Clinical example of Simultaneous Perception?

Fusion tests with fusion locks.

Clinical example of Fusion?

Seen in stereo tests or daily depth perception.

Clinical example of Stereopsis?

Simultaneous Perception

Both eyes see images at the same time (not necessarily fused).

Fusion

The two retinal images are integrated (sensory fusion).

Stereopsis

Highest level – Perception of depth and 3D vision

1. Simultaneous Perception

2. Fusion

3. Stereopsis

Grades of Binocular Vision (Claude Worth Classification)? (3)

Stereoscopic Vision (Stereopsis)

The ability to perceive depth and 3D space by combining slightly different images from each eye.

• Each eye views an object from a slightly different angle (due to interpupillary distance).

• The brain merges these dissimilar retinal images → depth perception.

Mechanisms of Stereoscopic Vision (Stereopsis)? (2)

Panum’s Area (Panama’s Fusion Space)

The region around the horopter where two slightly different retinal images can still fuse into one.

• Coarse (Gross) Stereopsis

• Fine Stereopsis

Types of Stereopsis

Coarse (Gross) Stereopsis

Use large retinal disparities; helps with motion and orientation in space.

Fine Stereopsis

Detects small differences; used for precise tasks.

• Spatial orientation

• Walking

• Driving

Function of Coarse (Gross) Stereopsis? (3)

• Reading

• Threading a needle

Function of Fine Stereopsis? (2)

Stereoscopic Acuity

The smallest binocular disparity detectable as depth — measured in arcseconds.

15–30 arcsec

Excellent Stereoscopic Acuity?

40–60 arcsec

Average Stereoscopic Acuity?

Up to 125–200 m distance

Limit of Stereopsis in Stereoscopic Acuity?

Eccentricity (off-center viewing)

Stereopsis decreases with?

• Hand-eye coordination

• Safe movement and navigation

• Sports performance

• Tasks needing depth judgment (e.g., surgery, driving)

• Lack of stereopsis can cause poor depth judgment and risk of injury.

Stereopsis is essential for?

Lang’s Two-Pencil Test

The test depends on the patient’s ability to use binocular cues to align two real 3D objects.

Synoptophore

Uses separate images projected to each eye via optical tubes to assess simultaneous perception, fusion, and stereopsis.

Julesz Random-Dot Stereogram

It tests true stereopsis by removing monocular clues.

Julesz Random-Dot Stereogram

When viewed binocularly, a hidden 3D shape “pops out” from random dots.

TNO Stereotest

Tests fine and coarse stereopsis using red-green random-dot plates viewed through corresponding filters.

TNO Stereotest

Patient wears red–green glasses.

Lang Stereotest (I & II)

Special textured 3D card with embedded images that each eye views differently. It uses a random-dot technique without filters.

200–1200 arcsec

Range for Lang Stereotest (I & II)?

Titmus Fly Stereotest

Polarized images create binocular disparity — 3D perception when viewed through polarized glasses.

40–3600 arcsec

Range for Titmus Fly Stereotest?

Randot Stereotest

Improved version of Titmus — eliminates monocular cues by using random-dot backgrounds.

20–400 arcsec

Range for Random Stereotest?

Frisby Stereotest

Uses transparent plastic plates of varying thickness — each plate has patterns with a real physical depth difference.

15–600 arcsec

Range for Frisby Stereotest?

Visual Field

Test of limit for entire area of space that you can see at one time while your eyes are fixated straight ahead at one single target.

Central Vision

Inner part of sight that allows to see fine details directly.

Peripheral Vision

Side vision, covering above, below, and sides when looking straight ahead.

Blind Spots

Natural gaps where the optic nerve meets the retina or abnormal dark spots (scotomas) caused by diseases.

180-220 Degrees

Total Field in Visual Field?

150 to 170 Degrees

Monocular Field in Visual Field?

100 Degrees

In Monocular visual field it is the degrees of temporally from central fixation?

60 Degrees

In Monocular visual field it is the degrees of nasally from central fixation?

Middle 120 degrees of overlapping

In Monocular visual field it is the degrees in overlapping?

30-40 Degrees

In Monocular visual field it is the degrees of exclusive visual field?

50-60 Degrees

Superiorly degrees in the Visual Field?

75 Degrees

Inferiorly degrees in the Visual Field?

Contrast Sensitivity

Ability to distinguish an object from its background when shading, light, or contrast is low.

Contrast Sensitivity

Enables us to see well in different conditions, such as foggy or rainy days, and allows you to identify road signs when driving during the night.

CSV-1000

Testing instrument with four sets of sine-wave grating (alternating light and dark lines) with varying spatial frequency.

Long Contrast ETDRS

Visual acuity chart with low contrast.

Hiding Heidi

Evaluates an infant or non-verbal child’s ability to detect low-contrast images and facial features.