One of the most significant instruments used in checking the accurate color perception of a human being is colour vision tests. Providing knowledge about what colour vision is, which kind of tests exist, and how the result should be interpreted can give insight into possible color vision deficiency for a person. Detailed information has been provided in the following article regarding color vision tests, procedure for the test, and result interpretation.

 

General Overview of Colour Vision

Colour vision is simply the capacity to distinguish wavelengths of light since the amounts of light which are taken in by the photoreceptors in the retina determine colours. The human eye has two types of photoreceptors: rods and cones. The former is used for vision in low light, while the latter functions in bright light and is sensitive to color. There are three types of cone cells, sensitive to different wavelengths of light.


  • S-cones: are sensitive to short wavelengths, or blue light.
  • M-cones: sensitive to medium wavelengths, or green light.
  • L-cones: sensitive to long wavelengths, or red light.

Color vision deficiency or rather referred to as color blindness; one has missing or defective forms of cone cell type. The absence, in some ways makes a challenge when a number of individuals tend to miss other colours other than being seen- frequently, one or two. Those usually involving red and green being the two types are frequent amongst others

 

There exist varieties of tests:

There are various tests to check the color vision of a person. Among them, some of the most commonly used ones are mentioned below:

 

1. Ishihara Test

The most widely accepted harmful colour vision test, particularly for the red-green form of colour blindness, are the Ishihara test. It was developed by Dr. Shinobu Ishihara in early part of the twentieth century. It is available in the form of a set of plates on which dots form colored shapes, thus making a pattern.


  • Procedure: Given a set of several plates. The observer then counts the number or gives the shape of a specific pattern constructed using colored dots, all of which are selected to be recognizable with normal color vision, but not at all very recognizable for any one of the specific color vision defects.
  • Results: Failure to clearly identify the quantity or pattern of a given colour combination on various plates is often a symptom of color vision deficiency.

2. Farnsworth-Munsell 100 Hue Test

Farnsworth-Munsell 100 Hue Test is more sensitive and determines a person's color discrimination capability for the colors present in the spectrum.


  • Test: There are 85 colored caps in the test, to be arranged in an ordered sequence so that it forms a gradient of color changes from one color to another.
  • Results: The amount of shift from the correct sequence establishes the severity and type of color blindness.

3. Anomaloscope

An Anomaloscope is an instrument which can be applied in diagnosing color vision deficiency, especially red-green color blindness.


  • Procedure: A patient views the Anomaloscope with both red and green illumination. Patient is asked to match both colors similar that he or she sees color matching
  • Results: the match setting might be applied so to further reduce type of color deficiency and severity of it

4. Computerized Color Vision Test

Due to the advancement in technology, one can now conduct color vision tests efficiently from behind any computer or smartphone. This type of test mainly uses the same standards that apply in an ordinary test but merely through a computer or mobile device instead.


  • Procedure: The patient is shown several pictures or patterns then asked to differentiate which are colours or shapes.
  • Results: Online tests give a preliminary estimate but are not as reliable as that of a professional in the clinic.

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Protocol of Colour Vision Test

The protocol followed for carrying out a colour vision test is generally the following:


  • Preparation: Illumination-controlled, distraction-free seating of a subject is necessary. The illumination must be proper so that they could distinguish easily between the colors.
  • Test Room: Special lights may be used in testing under conditions that stimulate the subject to see color discriminations properly, such as in Ishihara testing.
  • Test Administration: The practitioner administers the chosen color vision test to the individual. He or she leads the individual through each plate or section in tests where arrangement is necessary. In tests where arrangement is needed, the individual is provided with the materials.
  • Recording Results: The practitioner records the response of the client, including the problems the client may have in the test. It becomes useful during interpretation.
  • Post Test Counseling: Upon taking the test, the professional reviews the findings of the test result with the patient and describes those findings and its possible meaning in life.

Results Interpretation

The performance of this test could be interpreted through understanding the individual's performance, as well as the possible shortcomings. Here's how to interpret common test results:

 

1. Results of Ishihara Test

  •  Normal Vision: The person sees all or most of the numbers or shapes on the plates.
  • Color Vision Deficiency: He or she misses some numbers or shapes, possibly a sign of deficiency. Many plates that he or she missed will give away the type of color vision deficiency, such as red-green.

2. Results from Farnsworth-Munsell 100 Hue Test

  • Normal Color Vision: The person puts the caps in alignment very closely, a good performance in colour discrimination.
  • Colour Vision Deficiency: The greater the difference in the match, the greater the colour vision deficiency. The pattern of error can be further sub-classified.

3. Result of Anomaloscope Test

  • Normal Vision: The colour is matched perfectly with very minimal adjustment of settings.
  • Colour Vision Deficiency: The differences in the amount of adjustment needed specify the type and degree of deficiency.

4. Online Colour Vision Test Result

Preliminary Appraisal: Results from screening of internet tests are only presumptive of some deficiency and shall be clinically diagnosed for their validation.


Reasons for Conducting Color Vision Test

Color vision test is conducted for the following reasons:


  • Requirements in Occupation: For example, pilots, electricians, graphic designers require special color vision. Testing helps the appropriate person being chosen for this occupation.
  • Safety: Color vision defects decrease safety in instances such as the perception of colors of traffic light signals or warning messages. Awareness of the conditions can help in the provision of suitable precautionary measures.
  • Educational and Social Consequences: Knowledge of color vision defect can help deal with educational issues as well as social relationships in case of its diagnosis in a person.
  • Personal Awareness: Testing helps people know what type of color perception they may have, thus improving their choice of environment or activities.

The very important measurements that are used to check whether the person is viewing colors appropriately or not is the color vision test. Among some of the techniques used, it includes Ishihara test, Farnsworth-Munsell 100 Hue Test, and Anomaloscope. Once one learns about the process and its interpretation, then a person is aware of the kind of color perception he or she is experiencing and how to react concerning health and safety issues.

 

Conclusion

Knowing how important it is to test color vision, a person would take measures to ensure such deficiencies would not even come hence equipping one into real-life settings. Be it at the workplace, by having safety requirements, or even self-attentiveness of a person, with the bombardment that everyone has to face in this world, this is one essential thing to know about color vision.


Please book an appointment with the Best Eye Specialist in Lahore, Karachi, Islamabad, and all major cities of Pakistan through InstaCare, or call our helpline at 03171777509 to find a verified doctor for your disease.