Seeing Success in Gene Therapy Trial! Choroideremia

Gene Therapy Success!
A trial for choroideramia gene therapy has been reported. 14 patients at Oxford Eye Hospital received injections of a virus containing the missing gene, into the eye.

Significant improvements to vision were found across the group of patients. 12 maintained or even gained vision, which remained for up to five years. Of the untreated eyes, only 35% sustained vision.

"I was going into the operating theatre and having my eye injected with a virus that was used to insert the correct DNA into my cells so that the missing protein was produced. After the operation, I had my month one test. When I was doing the usual eye chart test, I had a lightbulb moment. I realised that I was about to go on reading past a point I had not reached in a decade.

I read the equivalent of four lines on the eye chart more than I could before. I was sitting there reading and I had tears just streaming down my face with this massive grin" - Joe Pepper, a Surrey teacher on receiving gene therapy.

This research will hopefully pave the way to future breakthroughs, for other eye diseases including macular degeneration.

Choroideremia is a condition that causes progressive loss of vision. Mainly affecting males, the first symptom is usually night blindness. Patients often feel their vision is not as good in low lighting, often starting from early childhood.

The visual problems are a result of loss of the cells that pick up light and also the choroid blood complex surrounding,this is also known as atrophy. As the condition progresses, visual field loss can follow, narrowing to leave tunnel vision. Fine detail or acuity can also be lost over time.Generally vision can decrease over time, but the severity each person experiences can vary.

Cause
Choroideramia is caused by mutated genes, specifically the CHM gene. CHM gives instructions and attaches to other molecules called Rab proteins inside cells. A mutation causes a cascade of events which mean the Rab proteins can not reach or attach to the correct area (organelles inside the cells), cells then die off prematurely.

Inheritance
An X-linked recessive pattern. The X-chromosome, one of the two sex chromosomes, are found as pairs in females XX and XY in males. So males only require one copy of the mutated gene to cause the condition, while females need two mutated copies. Women with just one copy are called carriers, they generally will not have symptoms of choroideremia but may show small areas of cell loss during a thorough eye examination. Though these changes may affect vision, but later on in life.

Statistics
It's estimated that choroideremia affects 1 in 50,000 to 100,000 people. It has been noted that they condition may go underdiagnosed because it shares similarities with many of eye disorders.
Of all causes of blindness, choroideremia accounts for 4%.

Read more at www.matheson-optometrists.com/choroideremia.html

Increase of contact lens related sight threatening eye infection

UCL, University College London alongside Moorfields Eye Hospital led  a study of infection in contact lens wearers. Since 2011, the researchers found three times as many incidences of Acanthamoeba keratitis in South-East England. A rare but preventable cause of blindness.

When contact lens users are aware of the risks involved in poor lens hygiene, they often adopt the correct habits and infection is unlikely. The increased cases illustrates the need for awareness.

Findings published in the British Journal of Ophthalmology, saw reusable contact lens wearers were at the highest risk. This group are more likely to have used ineffective lens solution, have water contaminate their lenses and admitted to poor lens hygiene.

What is Acanthamoeba keratitis (AK)?

• An eye disease affecting the cornea, the front surface of the eye. 
• It becomes inflamed and painful due to the infection. 
• The Acanthamoeba bug forms cysts during infection. 
• It is not only contact lens wearers that can be infected, but wearers pose a higher risk due to contamination of lens cases. 

What are the statistics?

• It can affect 2.5 in every 100,000 contact lens wearers.
• 25% of people with AK need corneal transplants to treat the disease or restore vision. 
• A quarter of affected patients become severe cases, loosing up to 75% of their vision or going blind all together. 
• Since 2000 - 2003 where incidences were 8-10 in a year, it's now noted that we treat between 36-65 cases annually.

What increases the risk?

• Researchers found that people were three times more likely to contract AK, if they had poor contact lens hygiene. 
• Those who did not consistently wash and dry their hands as part of their lens routine. 
• Also, in people who wore their contact lenses swimming or in hot tubs, while showering or face washing.

Where is Acanthamoeba found?

• The Acanthamoeba bacteria is actually found in the UK more commonly than in other countries. 
• Water contamination is the main concern for the UK, as Acanthamoeba is found in higher levels in domestic water supplies, as opposed to mains water. 
• As well as hot and cold water, it can also be found in soil.

How can I prevent an AK infection?

• Always follow your Optometrists advice on good lens hygiene and best practice.
• Wash and completely dry your hands before handling your lenses. 
• Avoid wearing your lenses swimming, when washing your face or showering/bathing. 
• Consider switching to a daily disposable lens, you can ask your optometrist to check your suitability and which lens type would be best for you. As the lens is replaced each day, there is no feeding ground for bacteria to grow over time and each lens is clean and fresh.

References:

Acanthamoeba keratitis
British Journal of Ophthalmology

Healthy Habits, Healthy Eyes - Moorfields

UCL