retina cell diagram.jpg
The above is from an OCT scan. I have never found the perfect diagram that shows all of the cell and layer types.
Following is a link to a collage of a few. You can usually find what you are looking for on one of them. These are
helpful in understanding research or other documents that speak of cell types and layers.




Quantitative optical coherence tomography angiography of vascular abnormalities in the living human eye Jia Y, Bailey ST, Hwang TS, McClintic SM, Gao SS, Pennesi ME, Flaxel CJ, Lauer AK, Wilson DJ, Hornegger J, Fujimoto JG, Huang D. Proc Natl Acad Sci U S A. 2015 Apr 20. pii: 201500185 PMID: 2589702


The first paper below, particularly Figures 1 & 2 therein, gives a good overview of the order of cell loss in CHM.There
is generally an overall thinning of the RPE, followed by loss of the outer segments of the photorecepters (rods then
cones) followed by loss of the remaining nuclear layer of thephotoreceptors and the outer limiting membrane.

IN VIVO IMAGING OF HUMAN CONE PHOTORECEPTOR INNER SEGMENTS-Drew Scoles, Yusufu N. Sulai, Christopher S. Langlo, Gerald A. Fishman, Christine A. Curcio, Joseph Carroll, Alfredo Dubra - IOVS 6-6-2014:


Other news items:



What is choroideremia?


Choroideremia (CHM - click here for images) impairs the vision of about 1 in 50,000 males who begin to experience difficulty seeing at night during their teens. As this is a progressive condition, peripheral vision loss becomes prominent and often leads to legal blindness by the age of 40. At this time, there is no cure for this condition. Choroideremia is caused by a change in the REP1 gene found on the X chromosome. This change prevents the gene from functioning properly. This gene encodes the Rab escort protein 1. Since men have an X and a Y chromosome whereas women have two X chromosomes, men with a faulty REP1 gene are affected but it is rare for female carriers to be severely affected. This is because the copy of the REP1 gene found on the second X chromosome in women is typically able to compensate for the faulty gene.
external image X-Linked-carrier-mother.jpg
X-linked inheritance with a carrier mother.

This genetic eye condition has an X-linked inheritance pattern. Female carriers have a 50/50 chance of having an affected son or a carrier daughter and a 50/50 chance of having an unaffected son or a non-carrier daughter. Affected men will not have affected sons but all of their daughters will be carriers.
external image X-Linked-affected-father.jpg
X-linked inheritance with an affected father.

What is gene therapy?
Gene therapy is an experimental technique that introduces genes into cells in the body to treat or prevent diseases. Many refer to human gene therapy as human gene transfer. Gene therapy is not a drug.
Although gene therapy is promising for a variety of conditions, the technique is experimental and remains risky. Research about gene therapy focuses on inherited disorders, some types of cancer, and certain viral infections. Currently, gene therapy is only being tested for diseases that have no curative treatment options such
as choroideremia. Gene therapy still needs to be proven to be safe and then effective in clinical trials before it can become a part of standard clinical care.
In the future, gene therapy may allow doctors to treat a disorder by inserting a working copy of the gene into the cells of a patient instead of using drugs or surgery. Researchers are testing several approaches to gene therapy, including:

      • Inserting a healthy copy of a gene into specific cells to replace the function of a mutated gene. The choroideremia gene therapy clinical trial takes this approach.
      • Inactivating, or “knocking out,” a mutated gene that causes the disease in the body.
      • Inserting a new gene to help fight a disease in the body.
Adapted from Genetics Home Reference, accessed October 31, 2012.


How is gene therapy expected to work in choroideremia gene therapy clinical trials?
Genes produce proteins that are necessary for cells to grow and function properly. Choroideremia is caused by a mutated gene that makes a faulty protein in specific eye cells in the retina. Gene therapy is designed to introduce a healthy copy of the gene into these cells to test whether the normal function of the protein can be restored. It can only work in living cells. This technique cannot revive dead cells and then improve cellular function.

A carrier called a vector is required to introduce the healthy copy of the gene into the cells. Certain viruses are often used as vectors because they have natural infective properties as well as other beneficial characteristics. The viruses are modified so they can no longer cause disease when used in people. The healthy copy of the gene is then attached to the virus through genetic engineering. Some types of virus, such asretroviruses, integrate their genetic material (including the new gene) into a chromosome in the human cell. Other viruses, such as adenoviruses, introduce their DNA into the nucleus of the cell, but the DNA is not integrated into a chromosome. The choroideremia gene therapy trial will use a version of an adenovirus. There are also other types of vectors that are not viruses, which are being tested for gene therapy.

The vector can be injected or given intravenously (by IV) directly into a specific tissue in the body (
in vivo), where it is taken up by individual cells. The gene therapy in the choroideremia gene therapy trial will be given by injection underneath the retina. If the gene therapy is successful, the new gene delivered by the vector will make a functioning protein. Researchers must overcome many technical challenges before gene therapy will be a practical approach to treating disease. For example, scientists must find better ways to deliver genes and target them to particular cells. They must also ensure that new genes are precisely controlled by the body (adapted from Genetic Home Reference, accessed November 16, 2012).
We do not expect gene therapy to reverse the effects of choroideremia and restore vision. If this type of intervention is successful, we hope that it will stop further progression of vision loss.