Rod monochromacy (day blindness or night vision) is a very rare disorder that affects 1 in 33,000 people in the United States. Achromatopsia is present from birth. The first signs may include the presence of nystagmus and light sensitivity accompanied with squinting in bright light. It is commonly misdiagnosed at birth with Congenital Nystagmus due to symptoms.
Achromatopsia is characterized by:
· Complete inability to differentiate colors
· Severe light sensitivity (photophobia)
· Long-sightedness
· Involuntary eye movements
· Central
There are two types of Achromatopsia, Complete Monochromacy and Blue Cone Monochromacy. Achromats must rely on their “rod vision”. Rods are located in the periphery of the retina, therefore color vision and detail vision is affected.
Complete monochromats have the most severe vision. They may have complete loss or retain a small amount of specific colors. Their visual acuity ranges from 20/120 to 20/200. Nystamus is usually present and may lessen with age. Age of onset is within the first six months of birth. It is typically found in only some siblings and must be an autosomal recessive gene from each parent. It is found in both males and females.
Blue cone is the rarest of achomatopsia. Their vision varies from severe to moderate. They will have imcomplete color vision loss and some may see in the blue – yellow axis. Their visual acuity ranges from 20/60 to 20/200. Nystagmus is usually present however may still have monochromacy without nystagmus which may reduce dramatically with age. Age of onset is within the first six months of birth. It possibly found in the maternal grandfather or maternal cousins and siblings. It is nearly exclusive to males. It can happen in females, however it is extremely
Vision loss is stable, however does vary with exposure to bright lights.
A view through the eyes of a Monochromat.
Important ways of enhancing vision for those affected is by filtering the light. Filters include the use of dark glasses, colored filters or red central contact lenses. Filters help decrease amount of light that is entering the eye. This allows the achromat better vision without glare. Students with Complete Monochromasy function best with the use of Red or Amber filters, whereas, student with Blue Cone Monochromacy function best with Magenta, Amber or Gray filters.
Students with achromatopsia will struggle with tasks that require the distinction of color or activities where the same shape has been utilized yet differing in color. They will also have difficulty with light and glare such as walking in and out of a building or areas with varied lighting such as the gym, library or cafeteria. Outdoor activities such as playing on the playground or participating in Physical Education in activities that are outside such as Track and Field, Flag Football etc, will certainly prove to be difficult. Ability for such mentioned activities will vary based upon weather conditions of cloudiness. The student should consider the use of recommended filters (prescribed sunglasses), tints and the use of hats or visors to control light.
The inclusion of large print may be a necessity as well as the use of magnifying devices to help reduce fatigue and eye strain.
Recent information has found a possible link with color blindness to dyslexia, however studies are continuing to affirm this possibility.
Congenital achromatopsia should not be confused with cerebral achromatopsia. Cerebral achromatopsia if a form o color blindness that can result from trauma, illness or some other cause. It is a stable condition which generally does not affect acuity. It is diagnosed by an neurologist rather than an ophthalmologist.
References:
The Achromatopsia Network (n.d.) What Is Achromatopsia? Retrieved June 25, 2011 from http://www.achromat.org/what_is_achromatopsia.html
Flick, D. (2007, July 20) Monochromacy – Complete Color Blindess Retrieved on June 25, 2011 from Colblindor http://www.colblindor.com/2007/07/20/monochromacy-complete-color-blindness/
Rod Monochromatism versus Blue Cone Monochromatism.(n.d.)Retrieved June 25, 2011 from Achromatopsia.info. A Journey through the Light! http://www.achromatopsia.info/rod-vs-blue-cone/
Howard, M (2008, June 13) Achromotopsia Retrieved June 25, 2011 from Serrendip at Brynmawr University http://serendip.brynmawr.edu/exchange/node/2038
Windsor, L.K.,O.D, F.A.A.O and Windsor, R.L., O.D., F.A.A.O., (n.d.) Understanding Achromatopsia, Retrieved June 25, 2011 from Low Vision Centers of Indiana, Published in Vision Enhancement Journal http://www.eyeassociates.com/understanding_achromatopsia.htm
Developed by: Mari Garza
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