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Who is Charles Bonnet?  He was a Swiss naturalist, philosopher, and biologist (1720-1793) who first described the hallucinatory experiences of his 89-year-old grandfather, who was nearly blind in both eyes from cataracts.   Charles Bonnet Syndrome is now the term used to describe simple or complex hallucinations in people who have impaired vision.  

Symptoms

People who experience these hallucinations know they aren't real.  These hallucinations are only visual, and they don't involve any other senses. These images can be simple patterns or more complex, like faces or cartoons.  They are more common in people who have retinal conditions that impair their vision, like macular degeneration, but they can occur with any condition that damages the visual pathway.  The prevalence of Charles Bonnet Syndrome among adults 65 years and older with significant vision loss is reported to be between 10% and 40%.  This condition is probably under reported because people may be worried about being labeled as having a psychiatric condition. 

Causes

The causes of these hallucinations are controversial, but the most supported theory is deafferentation, which is the loss of signals from the eye to the brain; then, in turn, the visual areas of the brain discharge neural signals to create images to fill the void.  This is similar to the phantom limb syndrome, when a person feels pain where a limb was once present.  In general, the images that are produced by the brain are usually pleasant and non-threatening.

Treatment and prognosis

If there is a reversible cause of decreased vision, such as significant cataract, then once the decreased vision is treated, the hallucinations should stop.

There is no proven treatment for the hallucinations as a result of permanent vision loss but there are some techniques to manage the condition.  Give these a try if you have Charles Bonnet Syndrome.

• Talking about the hallucinations and understanding that it is not due to mental illness can be reassuring.
• Changing the environment or lighting conditions.  If you are in a dimly lit area, then switch on the light and vice versa. 
• Blinking and moving your eyes to the left and right and looking around without moving your head have been reported as helpful.
• Resting and relaxing.  The hallucinations may be worse if you are tired or sick.
• Taking antidepressants and anticonvulsants have been used but have questionable efficacy. 

Over time, the hallucinations become more manageable and can decrease or even stop after a couple of years.

If you experience any of these symptoms, please get evaluated by your eye doctor to make sure there is not a treatable eye condition.  Don’t be embarrassed or ashamed—your issue is likely caused by a physical disturbance and we are here to help!

Article contributed by Jane Pan

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What Is Intraoperative Aberrometry?

Yes, that is a mouthful, but the concept isn’t quite as hard as the name.

An Intraoperative Aberrometer is an instrument we can use in the operating room to help us determine the correct power of the implant we put in your eye during cataract surgery.

Cataract surgery is the removal of the cloudy natural lens of your eye and the insertion of a new artificial lens inside your eye called an intraocular lens (IOL).

The cloudy cataract that we are removing has focusing power (think of a lens in a camera) and when that lens is removed, we need to insert an artificial lens in its place to replace that focusing power. The amount of focusing power the new IOL needs has to match the shape and curvature of your eye.

To determine what power of lens we select to put in your eye, we need to measure the shape and curvature of your eye prior to surgery.  Once we get those measurements, we can plug those numbers into several different formulas to try and get the most accurate prediction of what power lens you need.

Overall, those measurements and formulas are very good at accurately predicting what power lens you should have. There are, however, several eye types where those measurements and formulas are less accurate at predicting the proper power of the replacement lens.

Long Eyes: People who are very nearsighted usually have eyes that are much longer than average.  This adds some difficulty with the accuracy of both the measurements and the formulas. There are special formulas for long eyes but even those are less accurate than formulas for normal length eyes.

Short Eyes: People who are significantly farsighted tend to have shorter-than-normal eyes.  Basically, the same issues hold true for them as the ones for longer eyes noted above.

Eyes with previous refractive surgery (LASIK, PRK, RK): These surgeries all change the normal shape of the cornea.  This makes the formulas we use on eyes that have not had previous surgery not work as well when the normal shape of the cornea has been altered.

This is where intraoperative aberrometry comes in. The machine takes the measurements that we do before surgery and then remeasures the eye while you are on the operating room table after the cataract is removed and before the new implant is placed inside the eye. It then presents the surgeon with the power of the implant that the aberrometer thinks is the correct one.  Unfortunately, the power that the aberrometer isn’t always exactly right, but with the combination of the pre-surgery measurements and the intra-surgery measurements the overall accuracy is significantly enhanced.

The intraoperative aberrometry is also very helpful in choosing the power of specialty lenses like multi-focal and toric lenses.

We would encourage you to consider adding intraoperative aberrometry to your cataract surgery procedure if you have either a long or short eye (usually manifested as a high prescription in your glasses) or if you have had any previous refractive surgery.

Article contributed by Dr. Brian Wnorowski, M.D.