Achromatopsia: Gene Therapy Cures Eye Disease?


GAINESVILLE, Fla. (Ivanhoe Newswire) — Imagine only being able to see the things in front of you in soft focus, and just in black and white. For people with the genetic eye condition achromatopsia those are just some of the side effects.  But, researchers are testing a new treatment designed to cure the condition by fixing the gene responsible.

Each time Tara Cataldo prepares to leave her house, she has to make sure her face is completely shielded from the sun.

“I need to have very dark, very tinted sunglasses to feel comfortable outside and to see really well.” Cataldo told Ivanhoe.

Tara has achromatopsia, a genetic condition that makes her eyes incredibly sensitive to light.  She is also very nearsighted; even while wearing glasses or contacts, she can only see clearly at a very short distance.

“I cannot drive a car so I rely on public transportation and my bike to get around.” Cataldo explained.

Christine Kay, MD, a surgical ophthalmologist at Vitreoretinal Associates in Gainesville, FL said, “There are currently no approved and no effective treatments for achromatopsia.” (Read Full Interview)

Surgical ophthalmologist Christine Kay is working to change that. She is one of a handful of experts testing a gene therapy

“For achromatopsia the cells we have to target are cone cells responsible for decreased vision and color vision and those are cells at the very bottom layer of the retina.” Dr. Kay explained.

Using a tiny cannula, surgeons deliver a normal copy of one of two mutated genes; the CNGA3 or CNGB3 gene, directly into the eye … restoring vision.

Tara’s myopia is so severe that her risk of retinal detachment from any retinal surgery is high, which rules her out for the current trial. In the meantime, Tara says she’s learned to adapt to achromatopsia and live without limitations.

“And I hope all young achromats learn the same thing,” Cataldo said.

Doctor Kay says if the gene could eventually be delivered to the surface of the retina; additional patients, like Tara, could be treated. Agtc, the biotech company that developed the therapies and several U.S. universities have successfully tested this therapy in dogs and sheep.

Contributors to this news report include: Cyndy McGrath, Supervising Producer; Gabriella Battistiol, Assistant Producer; Roque Correa, Editor and Videographer.

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BACKGROUND: Achromatopsia is a hereditary and non-progressive visual disorder that is characterized by decreased vision, light sensitivity, and the absence of color in a patient’s vision. Sometimes called “day blindness” as patients can see better in dimmer light, complete achromatopsia will have reduced vision of 20/200 or less due to an abnormality of the retina. Patients may also have the presence of nystagmus or shaking of the eyes. It is caused by the portion of the eye responsible for “making the picture,” like the film in a camera. In a retina, there are three types of cells responsible for normal colored vision, referred to as cones. Green cones, red cones and blue cones, a balance of these cells is necessary for normal colored vision and a child born with non-functioning cones will have achromatopsia. It is an inherited condition; so far four genes are known to be associated with it. These are chromosome 14, chromosome 8q21-q22, chromosome 2q11, and chromosome 10q24.

TREATMENT: There is currently no cure for achromatopsia. Animal models of achromatopsia in dogs and mice have shown promising results in restoring some cone function in the retina. Children should be checked for refractive errors; prescribing glasses to correct far or near-sightedness and astigmatism can improve the vision somewhat but will not restore it to normal levels. Red colored lenses can help reduce a patient’s sensitivity to light which can enhance visual functioning. Plastic wrap-around glasses which have a top “shield” that covers the top of a prescription’s frame, as well as broad side shields to keep stray light from disabling the patient.


NEW TECHNOLOGY: A new clinical trial is underway testing gene therapy for achromatopsia. The genes are responsible for releasing proteins essential for the function of all the cells. Researchers remove the virus from the host DNA so it does not have the capacity to make the patient sick, and then insert the gene of interest into the DNA. Surgically done by a vitro retinal surgeon, the gene is then directly delivered to the retinal tissue. Researchers try to avoid directly touching the retina, to avoid detaching it and keep the surgery less evasive. The CNGA3 or CNGB3 gene would help restore the patient’s vision. This can only be done on certain patients; those with extremely severe achromatopsia are not able to participate in this trial because of the risk of retinal rupturing.

(Source: Dr. Christine Kay)


Erich A. Sandoval


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Doctor Q and A

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