All Posts tagged Retinitis Pigmentosa

Gene Therapy for Choroideremia

Robert E. MacLaren from Oxford, England has published an article in The Lancet, January 2014, describing the results of six patients who received gene therapy for choroideremia.

The initial results of the retinal gene therapy showed improved rod and cone function. In all patients over six months, there was an increase in retinal sensitivity in the treated eyes that correlated with the vector dose of the gene therapy.

The study assessed the effects of an adeno-associated virus (AAV) vector encoding REP1 (AAV.REP1) in patients with choroideremia. Choroideremia is an x-linked recessive disease that causes blindness due to mutations in the CHM gene, which encodes the Rab escort protein 1 (REP1).

The findings warrant further assessment of gene therapy in choroideremia, age-related macular degeneration, retinitis pigmentosa, and Stargardt’s disease.

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Retinal Prostheses

Retinal Prostheses

Retinal prostheses have had a long history and now include more than 15 companies and research groups in six countries. Those currently in or near human testing include:

  • Boston Retinal Implant Project – Boston, Massachusetts
  • Second Sight – Sylmar, California
  • Retina Implant AG – Reutlingen, Germany
  • Intelligent Medical Implant – Bonn, Germany
  • Epi-Ret – Bonn, Germany
  • Optobionics

The two groups that appear to be further along in development are Second Sight and Retina Implant AG.

Second Sight Argus II Prosthesis System

The Second Sight device uses a camera and transmitter mounted to eyeglasses, an implanted receiver, and an array of electrodes secured to interface epiretinally with retinal ganglion cells. A battery pack worn on the patient’s belt powers the system.

The camera captures images as the subject’s head moves to view objects and track movement. These images are processed by the transmitter and receiver and turned into electrical impulses on the epiretinal array. These electrical impulses are intended to stimulate the retina’s remaining cells and generate corresponding perception of patters of light in the brain, which patients interpret as meaningful images.

Retina Implant AG Prothesis

The Retina Implant AG prosthesis doesn’t have an external camera. Rather, it uses a light-sensitive microchip that is surgically implanted under the retina, in the macular region where photoreceptor cells are located. The implant moves with the eye, which provides for “more natural processing of the image.” Aside from the subretinal micro-photodiodes, the only other equipment is a power module implanted behind the ear.

It is my expectation that the Retina Implant AG will probably prove to be the most helpful artificial vision device for restoring useful vision in patients with retinal dystrophies and possible dry age-related macular degeneration. There are multiple reasons for this point of view:

  1. The device’s imaging functionality of the implant is in the eye, hence being coupled with eye movement.
  2. They were able to report letter reading, providing strong support for functional vision via electrical stimulants.
  3. Personal communication with Dr. Robert MacLaren in Cambridge, England, a surgeon who so far implanted six of these devices, stated that, “A great advantage of the subretinal device is that it moves with the eye and is therefore in a more natural position for acquiring a retinal image.” He also added, “The use of the bipolar cells also adds an additional level of processing on top of the epiretinal approach developed by Second Sight.”
  4. It is presently being studied at Wills Eye Institute in Philadelphia, Pennsylvania with Dr. Jay Federman. Its light sensitivity certainly is a great advantage for the Retina Implant AG. Stimulating the bipolar/horizontal cells from the subretinal space rather than ganglion cells from the retinal surface seems more physiological.

There are an estimated 1.2 million people worldwide with retinitis pigmentosa, including 100,000 in the United States. We can give our patients hope for improved vision in the future. The devices are well tolerated in the eye, and as the quality of the devices gets better, we may be able to show that there is real benefit from them for improved vision to change people’s lives.

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Treatment Update For Retinitis Pigmentosa

Vitamin Palmitate A

The recommendations from the clinical trial are that most adult patients with the common forms of RP take a daily 15,000 IU supplement of vitamin A palmitate under supervision of an ophthalmologist and avoid the use of high dose supplements of vitamin E, such as 400 IU. Consult with your physician regarding dosage for children.

A limited review of sources for vitamin A palmitate indicates that each supplier currently known to us (see below) is a company of good business standing that adheres to generally accepted good laboratory practices for manufacturing their products. The Retina Vitreous Resource Center can make no recommendation of one supplier over another regarding the quality of their product. Comparison and selections are your responsibility. You should call the listed companies for more information. The Retina Vitreous Resource Center has no further information to provide regarding these suppliers. (The prices are subject to change without notice.)

Disclaimer

The product described below have not been tested or evaluated by the Retina Vitreous Resource Center to determine their safety or effectiveness. Listing here of these suppliers and their products should not be misinterpreted as a recommendation or indication of proprietary interest in any of these companies.

Sources of Vitamin A Palmitate 15,000 IU

J.R. Carolson Laboratories Inc.
Attn: Customer Service – 1-800-323-4141
Pricing:
10 gel-caps is $8.90
240 gel-caps is $15.50 (shipping and handling $10.00)

Freeda Vitamins Inc.
1-800-777-3737 or 1-212-685-4980
Pricing:
100 tablets is $7.95

What Should You Do To Begin Vitamin A Treatment?

This is a serious undertaking. First consult with an ophthalmologist or another medical doctor. Do not start taking the vitamin A supplements on your own. Your doctor will want to do initial and subsequent annual evaluations, including tests to measure your blood level of vitamin A and to assess liver function. If these tests show that you have a pre-existing liver disease or abnormally high blood levels of vitamin A, your doctor may need to decrease your vitamin A intake accordingly. If you are not going to an ophthalmologist now, we suggest that you seek one who is willing to advise you regarding your eye care.

Since vitamin A in the palmitate form was used in the clinical trial of RP, the recommendations derived from that study apply specifically to the palmitate form. Although some other forms might be effective, that is not known because it was not studied. However, beta carotene, a natural precursor of the active form of vitamin A, is not a suitable substitute because it is not a predictable source of the vitamin.

Other Sources That May Help Retinitis Pigmentosa

1) Lutein 12mg Per Day
Puritans Low price at www.puritan.com
or 1-800-645-1030.
Pricing:
Lutein 6mg 100 caps (buy 1 get 1 free) total $13.59 Take (2) per day. Item #003481.

2) Omega 3 DHA 200mg Per Day
Puritans Low price at www.puritan.com
or 1-800-645-1030.
Pricing:
Omega 3 DHA 100mg soft-gels 120 soft-gels per bottle (buy 1 get 1 free) total $17.59. Take (2) per day item #001032.
– and –
Walgreens.com
or 1-877-250-5823
Pricing:
Omega 3 DHA 100mg, soft-gels #30 Take (2) per day. $13.99

Omega 3 DHA can also be found in Salmon and Tuna (1) or (2) 3 ounce servings per week.

If you go to your local pharmacy to purchase Lutein or Omega 3 DHA, be sure the dosage is correct. As stated for the vitamin A, Retina Vitreous Resource Center can make no recommendation of one supplier over another regarding the quality of their product.

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TruSopt

TruSopt (dorzolamide) reduces cystoid macular edema in patients with Retinitis Pigmentosa.
Gerald Fishman, M.D., University of Illinois at Chicago, demonstrated that all patients in his study showed a significant reduction in swelling in at least one eye after using TruSopt three times a day for one to two months. Results of the study were published in the January 10, 2007, issue of the British Journal of Ophthalmology.

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