What is a cherry-red spot
One of the signs of Tay-Sachs is the presence of a cherry-red spot. When this is found, you will probably be told in technical terms that it occurs in the eye and that it is a sign of a lipid storage disease.
However, people are rarely actually told what a cherry-red spot is in language that us non-scientific people can understand. So, we have put together a simple explanation and we hope it helps – please let us know if it there’s anything that could be made clearer!
To understand what a cherry-red spot is, it is important to know that the Hex-A enzyme is vital to the body as it naturally prevents the build up of waste proteins (GM2 gangliosidosis). Normally the Hex-A enzyme clears away these waste products and prevent a number of major health issues occurring.
Tay-Sachs is the lack or a reduced level of the Hex-A enzyme and is known as a lipid storage disease.
The medical explanation of a cherry-red spot is:
“A cherry-red spot is an indicator of a number of different lipid storage disease and it describes the appearance of a small circular shape as seen through the fovea centralis which is located in the center of the macula region of the retina.”
In simple terms, it means that there is an appearance of a red shape that appears in the eye and is seen by the doctor by using drops to dilate the pupils. With a special microscope the red shape can be seen.
The effect on the eye
The medical explanation goes on:
“Its appearance is due to a relative transparency of the macula; storage disorders cause the accumulation of storage material within the cell layers of the retina, however, the macula, which is relatively devoid of cellular layers, does not build up this material, and thus allows the eye to see through the macula to the red choroid below.”
The doctors say that the retina is like a passport into what is going on in the body in terms of a lipid storage disease. There is a certain part of the eye (called the macula) which is not affected by these diseases in terms of visible changes, and appears like a beacon compared to other parts of the eye which are affected by it. This allows the doctors to detect whether a cherry-red spot is present or not. If it is seen, then more testing is requested (normally genetic testing) to rule out a lipid storage disease as a cherry-red spot is present in relation to central retinal artery occlusion (this is where blockage of the retinal artery happens).
If a cherry-red spot is detected then you should be aware that in many of the lipid storage diseases it is a very common sign and you should prepare yourself that your family member may have one of these major conditions.
Tay-Sachs and a cherry-red spot
A more specific Tay-Sachs description is shown below in terms of a cherry-red spot:
“All patients with Tay–Sachs disease have a “cherry-red” macula, easily observable by a physician using an ophthalmoscope, in the back of their eyes (the retina). This red spot is the area of the retina which is accentuated because of gangliosides in the surrounding retinal ganglion cells (which are neurons of the central nervous system). The choroidal circulation is showing through “red” in this region of the fovea where all of the retinal ganglion cells are normally pushed aside to increase visual acuity. Thus, the cherry-red spot is the only normal part of the retina seen. Microscopic analysis of neurons shows that they are distended from excess storage of gangliosides. Without molecular diagnostic methods, only the cherry red spot, characteristic of all GM2 gangliosidosis disorders, provides a definitive diagnostic sign.”
This basically says that the build up of the waste protein (GM2 gangliosidosis) affects vision which is why children with infantile Tay-Sachs generally go blind as there is damage to the eye. The cherry-red spot is actually the only normal looking part of the eye.
However, if there is any of the Hex-A enzyme present, as can be the case in Juvenile and Late-Onset, it is sometimes possible that the damage to the eye can improve or not deteriorate as bad as other cases as the waste products are slowly eliminated.
Helping someone with a cherry red spot
Some eye specialists will recommend the use of glasses and/or a patch. Specially designed glasses may be able to by-pass the problems associated with the cherry-red spot. A patch may help if one eye has much better vision than the other. In this case, the child will wear a patch over the good eye for a period of time, forcing them to use the bad eye.
However, it is important to note here that in most cases where a cherry-red spot is present there will be a continual loss of vision leading to blindness. It may be possible to help delay the onset of this vision loss but it is completely dependent on the individuals severity of Tay-Sachs.
On a factual front, a cherry-red spot was one of the first symptoms of Tay-Sachs discovered and diagnosed. Waren Tay is the opthamologist who discovered it in a patient in 1881 and the disease is in part named after him (the other being Bernard Sachs).