Lately, I have been repeatedly asked about what effect FTD can have on the eyes. The answer to this question varies greatly depending on whom you ask. As you read this, please bear in mind that I have no medical training. I have, however, read an awful lot about how the eyes work and about different diseases of the eye. I have had diseases of the eyes for about 30 years now and that is why my avid interest in the subject. Much of my knowledge has also come from the many eye specialists that I have seen in many clinics across the country.
For me, one of the most interesting thing related to FTD and the eyes is research that is being conducted regarding early detection of FTD through images of the retina. In the research, retinal degeneration possibly can detect FTD before the patient experiences and clinical symptoms.
The retina is often called "the window to the brain" because it is made up of neurons that directly connect to the brain. Researchers have noted a significant decrease in cell activity in the retina of dementia patients. Much of the research, but not all, has been limited to the genetic form of FTD so far.
So, if early detection is possible through the retina, it seems possible that the retina could be the cause of eye problems in FTD. Each eye has its own retina and they each send their images to the Occipital lobe, located in the back of the brain. That is the end of the retina's job. Your eyes each see their own image and each sees approximately 3/4 of the image the eyes are seeing. It is up to the brain to overlay the two images into one image. It is up to the other areas of the brain to interpret those images. Much of this interpretation is done by the temporal lobes.
If the two images transmitted from the retinas are not interpreted by the brain properly, the images may causes many symptoms, including double vision. Double vision is a very troubling symptom to many with FTD.
Quite often in FTD, those who complain about blurry vision are actually experiencing a small amount of double vision. It is suggested to test this yourself by covering one eye at a time and determining if the vision is blurry in just one eye or only when you look through both. If both eyes, by themselves, are not blurry, the cause of the blurry vision is quite possibly a case of double vision.
In some cases, the double vision can be extreme. Instead of appearing as blurry vision, the patient may see two distinct images. This can be quite troublesome in many ways. For instance, when travelling in a car, I see two images of cars coming toward us. One of them appears to be in our lane which causes me to become frightened and I often distract the driver by my reactions.
Along with the double vision, there can be other differences in the image from each eye. For some, if you cover one eye at a time, you can often tell that one image is larger than the other. It can also reveal a different in color intensity and/or a difference in depth. This depth perception can be troublesome in itself.
Now, I would be negligent if I did not mention that there is no way for corrective lenses to correct these vision issues. For most people, double vision can be corrected with prism lenses to bring the two images together. In FTD, the two images fluctuate constantly. The prism lenses may help intermittently, but they can make it worse the rest of the time. I mention this because many optometrists will suggest this and, with the costs of glasses, it can become a huge waste of an investment.
The easiest way to explain why our double vision issues are different because of our FTD is to explain that it is the brain seeing double, not the eyes themselves. In the case of non-FTD patients, the cause for double vision is quite often muscular issues with the eyes. Not so for us.
Poor vision can also affect those with dementia with the loss or restriction of peripheral vision. Let me tell you, I am a terror in the grocery store because I cannot see other people or their carts until I am right up to them, usually bumping into them. I read that the loss of peripheral vision can also add to difficulties dementia patients experience eating. In the late stages, when they are needing to be fed, they don't see the food or utensil until it is right at their mouth and it scares them. This is also part of the issue of FTD patients being afraid of the shower. They cannot see the water until it hits them. Many experts will tell you that when approaching a dementia patient, approach from the front, not the back or sides because they can't see you and will be startled.
There are other things too. For instance, double vision can rapidly tire the eyes and lead to horrific headaches. Add that to the already existing problem of FTD headaches and you have a real mess. Eye strain is an issue as well. I can only watch television for short intervals, about 45 minutes. The only way to continue after that is to cover my left eye (which in addition to double vision has a huge blind spot) because the right is strongest and finish watching with one eye. I can't do that for very long either.
Fortunately, at least for me, the double vision gets worse with distance so I am still able to read and do things on the computer
The other thing I advise for those with FTD is, when you are wanting to have your eyes checked, please see an Ophthalmologist (preferably one who is quite knowledgeable about retina issues) and not an Optometrist. I have always found that Optometrists are the best when you are needed corrective lenses, but for diseases of the eye, always an Ophthalmologist.
I am probably forgetting some of the issues with FTD and vision, but this is certainly enough information for one blog. Again, please remember that I have no medical training and that if you have questions about your eyes, please see a professional!
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