Aspects of vision – Contrast


How the EYES functionHow YOU function

Raising a red flag

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Optical problems that affect the eye’s ability to deliver a clear image of the outside world to the retina include:

  • lack of correction or under-correction of refractive errors (often correctable with glasses or contact lenses)
  • a cataract, a clouding of the lens in the eye (usually correctable with surgery).
  • retinal disorders such as macular degeneration and glaucoma (requiring medical treatment)

Reduced contrast sensitivity is associated with diseases of the organs of vision, both optical problems such as cataracts and refractive error and diseases of the outer retina such as Macular Degeneration and of the inner retina such as glaucoma and optic neuropathy.

Like visual acuity, contrast sensitivity loss is non-specific; test results do not in themselves lead to a diagnosis. But measuring and documenting contrast sensitivity can play an important role in the early detection of certain visual system conditions, especially those that leave high contrast visual acuity unaffected such as optic neuropathies, glaucoma, and diabetes. Well before visual acuity is affected, retinal disorders may cause deficits in contrast sensitivity that will show up in testing, indicating a need for a more comprehensive professional examination.

Contrast sensitivity in the real world

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Becoming aware of one’s reduced contrast sensitivity through testing is the critical first step to learning to adapt to and make adjustments for low contrast sensitivity. (See Testing below) When you have identified low contrast sensitivity as a cause of vision difficulties, you can adapt strategies to optimize your vision.

 

 

 

Strategies for those with low contrast sensitivity may include focusing awareness on those situations that are most challenging such as:

    • driving at night, low contrast hazards such as curbs and steps, dimly lit rooms….
    • improving illumination. While magnification is helpful for visual acuity loss, better lighting creates a higher contrast lighting and brings out objects that are not visible in low light. You might be unable to see white rice on a white plate on a white tablecloth until the lighting is increased. Better lighting is key to improving one’s ability to read.
    • enhancing the contrast of your environment. If your stairs are hard to see, you can mark them with tape of a contrasting color. Writing with a wide-tip dark black pen can make writing easier.
      See ____ for suggestions…. LINK here to modules on this >>>
    • adopting glasses with specially designed color tints (often yellow or amber) that often improve contrast.