Subjective Assessment of The Observer

Various factors related to the observer may affect the perception of color, they include the following:

1. Color vision: Dental practitioners may have a defect in color vision.^7,24 Several studies have reported that approximately 8% of males and 0.5% of females may be suffering from congenital color deficiencies.^50,51 Hence, dental practitioners should have their color vision evaluated (early on) to ensure accurate shade selection. If a color vision defect is present, the practitioner should seek the assistance of a dental auxiliary and/or digital shade-matching devices for selecting tooth shades. Practitioners may also suffer from binocular disparity (imbalance in the color perception between the right and left eye.)⁷ To limit the error associated with binocular differences, it is advised to position the shade tabs below or above the tooth of interest as opposed to beside it.^7,24

2. Aging: Aging may cause worsening of shade-matching ability due to alterations in vision.^7,24 Also, the cornea and lens of the eye turn yellow with age, thereby causing objects to appear more yellowish and brownish compared to their original color.^7,24

3. Gender: Multiple studies report that women can perceive color more accurately than men.^7,24

4. Substance abuse and medications: The misuse or inadvertent use of drugs, alcohol, and caffeine may impair color perception.^24,28 Medications used for treating erectile dysfunction (such as Viagra) may add a blue tint to the vision.²⁴ The use of oral contraceptives is associated with difficulty in differentiating various colors, including red, green, yellow, and blue.²⁴ Also, prolonged use of oral contraceptives may lead to a decrease in yellow and blue color perception.^24,28

5. Eye and Color fatigue: If the eyes are fatigued, they may not be able to identify colors accurately. Hence, it is recommended to schedule these procedures early in the day and perform them at the beginning of the appointment.^7,24 Color fatigue is associated with constant exposure of the eye to a single color, thereby decreasing its responsiveness to that color.^28,44 To circumvent this phenomenon, it is suggested that the operatory walls be painted neutral gray and the practitioner periodically glance at them during shade selection.^28,44