Achromatopsia - An Overview

Introduction

Achromatopsia is an inherited disorder of the retina of the eye, and the ability to see color is limited. It is present at the time of birth and non-progressive, the symptoms do not get worsened as time passes. It is a different form of color vision deficiency and different from color blindness. In this syndrome, people can only see black, white, and some shades of grey, while in color blindness, people can perceive colors but are difficult in distinguishing between certain colors, like red and green.

What Is Achromatopsia?

Achromatopsia is a condition in which there is a complete or partial absence of color vision. People with this disorder can only see black, white, and shades of grey. In incomplete achromatopsia, people can appreciate a range of colors. This condition involves other vision problems like

• Increased Sensitivity to Light (Photophobia) - It is a condition in which bright light causes pain in the eyes. When bright light enters, blinking the eyes help reduce the amount of light entering the eye.

• Involuntary Eye Movements - The uncontrolled and rapid movement of the eye. The movement can be up and down or in circular motions. These uncoordinated eye movements can result in changes in vision, balance, and coordination.

• Reduced Sharpness of Vision - Blurred vision, formed image is not sharp and crisp. It is a common symptom associated with vision and eye problems.

• Nearsightedness or Far-Sightedness - Difficulty in seeing either near objects or far-away objects.

Achromatopsia is completely different from the color vision problem and color blindness. The prevalence of this condition is one in 30000 people worldwide. The people of the island of Pingelap have a high prevalence of this disease. Two types of achromatopsia are present; completed and incomplete. Complete achromatopsia is more common than incomplete type.

What Are the Causes of Achromatopsia?

This occurs due to mutations of several genes that code for the proper functioning of photoreceptor cells of the retina. Retina has two types of photoreceptor cells called rods and cones. Rods provide vision in low light and cones provide vision in bright light. These cells help in the transmission of visual signals to the brain and the image is seen. This process is called phototransduction. In patients with mutated genes, phototransduction is affected. In complete achromatopsia, the cone cells are non-functional and the rode cells only are functional. In the case of incomplete achromatopsia, there is limited color vision. In some people with complete achromatopsia, there are no identifiable gene mutations, and the exact cause is unknown.

What Are the Symptoms of Achromatopsia?

• Blind spots.

• Blurred vision.

• Color blindness.

• Extreme farsightedness.

• Discomfort in bright light.

• Nearsightedness.

• Poor vision.

• Involuntary eye movements.

When Does the Symptom Develop?

Being a genetic disorder this condition is presented by birth itself. Sensitivity to light comes in the first month of life. The symptoms will be noticed as the child grows a little older.

How Is Achromatopsia Diagnosed?

• An ophthalmologist diagnoses the condition. The retinal exam may be normal.

• Color Vision Testing - This test is also called the “Ishihara” color test, where the ability of eyes to differentiate different colors is tested. If the test is not passed the patient has some color vision problems, either partially or completely.

• Fundus Autofluorescences Test - A non-invasive imaging technique used to assess retinal pathologies.

• Ophthalmic Electrophysiology - A group of tests performed to evaluate how various parts of the eye respond to light. It helps in evaluating the vision system of the eye.

• Electroretinography (ERG) - Also known as an electroretinogram, measures the electrical response of the rods and cones of the eye. Normal eye response shows a wavy pattern response to each flash of light.

• Optical Coherence Tomography - A non-invasive imaging technique, used to generate pictures of the back of the eye, the retina. Also used to measure the thickness of the retina and the optic nerve.

• Visual Field Testing - This test measures, how far the eyes can see without moving and how is the vision in a different field of vision

How Is Achromatoipsia Treated?

Achromatopsia has no known cure, still, symptomatic treatment can be given to improve vision and to improve quality of life.

• Use of Special Glasses - Also called ‘EnChroma’ glasses, used by people with color vision problems. These glasses increase the saturation of colors that the eyes can see and help perceive the correct color.

• Low Vision Therapy - Achromatopsia and the associated symptoms can diminish vision. Making daily tasks difficult. Certain low vision aids help in making vision easier. The low vision aids include

• Spectacle-mounted magnifiers.

• Handheld or spectacle-mounted telescopes.

• Handheld and stand magnifiers.

• Electronic magnification devices.

• Assistive technology.

• Books on tape.

• Talking wristwatches.

What Is the Prognosis In People With Achromatopsia?

• In children the prognosis is good. Children can continue their education and day-to-day activities. They need support and assistance to overcome the challenges.

• Similarly, adults with this disorder can also lead a normal life. They adapt to the new lifestyle and day-to-day activities. The symptomatic treatment and use of low vision aids help to improve the quality of life.

What Are Tips to Manage Life With Achromatopsia?

• Avoid exposure to very bright light.

• Use of visual aids while using electronic gadgets.

• Avoid overexposure to bright sunlight. Use of hat or sunglasses while going out.

• Give more open space in the home to avoid bumping into things.

• Better organization of essential things. Giving large labels to things boxes in the kitchen can help save time.

Conclusion

Achromatopsia is a genetic disorder caused by a genetic mutation, resulting in partial or complete loss of color vision. The condition can be either complete or incomplete. Symptoms can vary from person to person. The quality of the image can be different. There is no complete cure for this condition. Proper therapy and the use of special glasses to improve vision help the affected persons to lead a good life without compromising the quality of life.