Color Perception Test

General

Synonym/Acronym:
color blindness test, Ishihara color perception test, Ishihara pseudoisochromatic plate test.

Rationale
To assist in the diagnosis of color blindness.

Patient Preparation
There are no food, fluid, activity, or medication restrictions unless by medical direction.

Normal Findings

• Normal visual color discrimination; no difficulty in identification of color combinations.

Critical Findings and Potential Interventions
N/A

Overview

(Study type: Sensory (ocular); related body system: Nervous system.)

Defects in color perception can be hereditary or acquired. Color blindness occurs in 8% of males and 0.4% of females. It may be partial or complete. The partial form is the hereditary form, and in the majority of patients, the color deficiency is in the red-green area of the spectrum.

Knowledge of genetics assists in identifying those who may benefit from additional education, risk assessment, and counseling. Genetics is the study and identification of genes, genetic sequence variations, and inheritance. For example, genetics provides some insight into the likelihood of inheriting a condition such as color blindness. Some conditions are the result of sequence variations involving a single gene, whereas other conditions may involve multiple genes and/or multiple chromosomes. Color blindness is an example of a recessive sex-linked genetic disorder passed from biological mother to male children at birth. Further information regarding inheritance of genes can be found in the study titled “Genetic Testing.”

Acquired color blindness may occur as a result of diseases of the retina or optic nerve. Color perception tests are performed to determine the acuity of color discrimination. The most common test uses pseudoisochromatic plates with numbers or letters buried in a maze of dots. Misreading the numbers or letters indicates a color perception deficiency and may indicate color blindness, a genetic dysfunction, or retinal pathology.

Color perception is important in some occupations, and testing for color perception may be a requirement for employment, especially for health-care workers whose responsibilities include assessment and monitoring of symptoms or changes in patients’ conditions. Some common examples of color-based assessments in a health-care environment include interpreting the results of color pads on blood or urine test strips, identifying changes in body color (e.g., pallor, cyanosis, jaundice), determining the presence of blood or bile in body fluids and feces, and evaluating pH test strips to verify correct placement of a nasopharyngeal tube.

Indications

• Detect deficiencies in color perception.
• Evaluate because of family history of color visual defects.
• Investigate suspected retinal pathology affecting the cones.

Interfering Factors

• Inability of the patient to cooperate or remain still during the procedure because of age, significant pain, or mental status.
• Inability of the patient to read.
• Poor visual acuity or poor lighting.
• Failure of the patient to wear corrective lenses (glasses or contact lenses).
• Damaged or discolored test plates.

Potential Medical Diagnosis: Clinical Significance of Results

Abnormal Findings In:

• Identification of some but not all colors

Nursing Implications, Nursing Process, Clinical Judgement