Suman Thakur, B.Optom, F.Optom

Paediatric Optometrist, Dr. Shroff’s Charity Eye Hospital, New Delhi, India


Contrast sensitivity (CS) is the ability of the eye to detect small changes in illumination at the targets that do not have clearly defined limits. (1, 2)  CS refers to the ability of the visual system to discriminate edges in a screen and effectively defines the boundaries of the objects. (3)

Contrast sensitivity measures real world:

Visual acuity (VA) uses only black and white letters, but the real world consists of shades of gray therefore measuring CS is just as important as (VA) and now is universally accepted as a part of routine practice (4) as it reflects the quality of vision and in many cases decline earlier, while VA remains normal. (2)

CS defines the threshold between the visible and non-visible, which has both elementary and clinical significance in the science of vision, whereas, the VA is measured at the fixed target (Optotype), and it may be the basic assessment of vision which does not fully meet the daily requirements of the human visual function, which encounters a variety of stimuli of varying intensity.

Figure 1: Image of a staircase with normal vision and vision with reduced contrast sensitivity.
[Image courtesy:]

For the real-world vision, CS is much more sensitive to measure besides having 20/20 vision (Figure 1). CS testing however has been found to be significantly predictive of visual performance in the natural world. (5)

There are various eye or health conditions that may diminish your CS and make you feel that you are not seeing well in the real world. Some factors that contribute in loss of spatial contrast sensitivity seen in ocular conditions are as follows:

  1. Diabetes (diabetic retinopathy)
  2. Cataract
  3. Glaucoma
  4. Traumatic optic neuropathy
  5. Amblyopia
  6. Optic Nerve Disorders

These conditions cause significant loss in vision and simultaneously the level of contrast sensitivity also decreases, hence, the quality of life is affected.

Importance of CS in daily life:

CS is important in daily life because it helps you to identify objects that may not be outlined clearly and pick up on subtle details. However, contrast is important for many things. Here are some real-life situations where contrast plays a big role (Figure 2).

People with decreased CS also have greater difficulty with high-risk driving (more on rainy and foggy days) than patients with good vision, even after adjusting for age, gender, and cognitive impairment. (6) In the kitchen, people will have difficulty in identifying sugar and salt in a white plate or bowl.

Figure 2: Images of a road seen through different contrast levels.
[Image courtesy:]

Doctors must have good contrast on differentiating the flowing blood and arteries and picking up the correct instrument from the silver tray at appropriate time. Pilots must face difficulties in identifying small, semi-isolated, air to ground targets. It is even found that contrast sensitivity and visual field had the greatest effect on orientation-mobility, but that visual acuity had a negligible effect, hence, the loss of spatial awareness and poor mobility or orientation can increase the risk of accidents such as falls. (7)



The real world is not only limited to the black and white target. We must not be satisfied with reading the smallest target. We must be aware of our functional vision by measuring the CS and know the real level of our vision. You might not know what the real world looks like and you might be missing the pleasure of viewing the beautiful world.

In conclusion, not everything we see is black and white.  There are various colors of life and the contrast plays an important role in it and the pictures above can clearly show how important is contrast in daily life not only for a quality life but also for a safe and secure life.



  1. Adams, R. J., & Courage, M. L. (2002). Using a single test to measure human contrast sensitivity from early childhood to maturity. Vision research, 42(9), 1205–1210.
  2. Arden G. B. (1978). The importance of measuring contrast sensitivity in cases of visual disturbance. The British journal of ophthalmology, 62(4), 198–209.
  3. Campbell, F. W., & Robson, J. G. (1968). Application of Fourier analysis to the visibility of gratings. The Journal of physiology, 197(3), 551–566.
  4. Moseley, M. J., & Hill, A. R. (1994). Contrast sensitivity testing in clinical practice. The British journal of ophthalmology, 78(10), 795–797.
  5. Owsley, C., & Sloane, M. E. (1987). Contrast sensitivity, acuity, and the perception of ‘real-world’ targets. The British journal of ophthalmology, 71(10), 791–796.
  6. 6.McGwin, G., Jr, Chapman, V., & Owsley, C. (2000). Visual risk factors for driving difficulty among older drivers. Accident; analysis and prevention, 32(6), 735–744.
  7. Marron, J. A., & Bailey, I. L. (1982). Visual factors and orientation-mobility performance. American journal of optometry and physiological optiCS, 59(5), 413–426.