August 22, 2026

PACES diaries

Learning PACES is never easy unless you have someone to pave the pathway for you

Color Vision 

Color Vision Examination Methods

Color vision can be assessed using simple techniques, especially when complex instruments are unavailable:

  • Use the back of an MDF knee hammer or a red hat pin.
  • Procedure:
    • Have the patient close one eye and present the color (e.g., red).
    • Ask them to identify the color, then repeat for the other eye.
  • You can also carry a red and green pen if interested in neurology.
  • Procedure:
    • Present the colors while the patient closes one eye and ask for identification.
  • During visual acuity tests, show colored objects while the other eye is closed for a comprehensive assessment. And check both the eyes

Table of Color Vision Defects

Type of Color Vision Defect

Description

Causes

Protanopia

Red color blindness; inability to perceive red light.

Genetic mutation affecting the L-cone photopigment; can also be influenced by aging and certain eye diseases.

Deuteranopia

Green color blindness; inability to perceive green light.

Genetic mutation affecting the M-cone photopigment; may also be exacerbated by retinal diseases or damage.

Tritanopia

Blue color blindness; inability to perceive blue light.

Genetic mutation affecting the S-cone photopigment; can also result from certain medications or retinal disorders.

Protanomaly

Reduced sensitivity to red light; mild red color blindness.

Genetic mutation affecting the L-cone photopigment; may worsen with age or eye conditions.

Deuteranomaly

Reduced sensitivity to green light; mild green color blindness.

Genetic mutation affecting the M-cone photopigment; can be influenced by retinal diseases or aging.

Tritanomaly

Reduced sensitivity to blue light; mild blue color blindness.

Genetic mutation affecting the S-cone photopigment; may also be linked to certain ocular conditions.

Achromatopsia

Complete color blindness; inability to perceive any colors.

Genetic mutations affecting cone photoreceptors; can also be caused by retinal dystrophies, brain damage, or certain syndromes (e.g., cone dystrophy).

 

 

 

 

 

Drugs Causing Color Vision Changes

  1. Antimalarials:
    • Examples: Chloroquine, Hydroxychloroquine
    • Effect: Retinal toxicity affecting blue-yellow perception.
  2. Antibiotics:
    • Examples: Gentamicin, Tobramycin
    • Effect: Potential retinal toxicity.
  3. Chemotherapy Agents:
    • Examples: Vincristine, Cisplatin
    • Effect: Can affect the optic nerve.
  4. Psychotropic Medications:
    • Example: Chlorpromazine
    • Effect: Retinal pigmentary changes.
  5. Beta Blockers:
    • Example: Timolol
    • Effect: Possible long-term color vision changes.
  6. Digitalis Preparations:
    • Example: Digoxin
    • Effect: Yellow-green vision disturbances.
  7. Recreational Drugs:
    • Examples: LSD, MDMA
    • Effect: Temporary color perception alterations.

 

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