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Laser Eye Beams

As the editor of Photonics Tech Briefs, I cover laser technology for a living. They’re pretty fascinating devices, but that doesn’t mean I ever wanted to have a laser beam shot into my eye. Unfortunately, Father Time and our own bodies do not always give us a choice.

I was recently diagnosed as a prime candidate for narrow angle glaucoma. According to my optometrist, fluid in the eye normally drains through the space, or angle, between the cornea – the clear element covering the front of the eye – and the colored part of the eye, called the iris. In some people, like me, as we get older the lenses in our eyes continue to grow while the anterior chambers get shallower, causing the drainage angle to narrow. This causes pressure in the eye to increase. If it gets too high, it can result in a very serious condition known as acute angle closure glaucoma, which can send you to the emergency room with severe eye pain, nausea, vomiting, blurred vision, and some other very unpleasant symptoms. If they can’t relieve the pressure immediately, it could result in permanent damage or loss of vision.

The way to prevent that is a relatively simple medical procedure called laser iridotomy, which involves using a precisely focused laser to burn a tiny microscopic hole in the iris, causing it to move away from the fluid drainage area, thereby relieving the pressure. Notice I said “relatively simple” because that’s how the eye surgeon described it. As for me, getting shot in the eye with a laser sounded anything but simple.

The laser used for this procedure, at least in my case, was a Nidek combo YAG/green laser that combines their YC-1800 ophthalmic Nd:YAG laser and GYC-1000 green laser photocoagulator into one machine. According to my surgeon, having both types of laser combined in one system allows for “on the fly switching.” I was about to ask him why that’s important when I realized his answer my only increase my fear factor, so I just let it go.

The procedure, which takes all of about 2 or 3 minutes, is painless, but it does involve some degree of discomfort. After anesthetic drops are placed in the eye and the patient’s head is positioned on the machine, a small device is placed over the eye to hold it open throughout the procedure. The patient is then instructed to focus their other eye on some point – the doctor’s shoulder, for example – told not to blink, and the procedure begins. For the next few minutes the eye being treated endures a series of very bright flashes of light – like a strobe light – and an uncomfortable feeling of pressure being exerted on the eyeball. I counted a total of 62 flashes in all, which is a lot when you’re trying not to blink…or panic. When it was over, vision in that eye was slightly blurry and it felt irritated, like a bad case of dry eye, for several hours. After that everything was fine.

Afterwards, I asked my doctor about the flashes. As he explained it, that was the laser being triggered. The hole in the iris is not formed with one long, continuous burst, as one might assume from watching old sci-fi movies. Rather, each burst removes a microscopic amount of material until the hole is created. He seemed somewhat surprised when I told him how many flashes I’d counted.

I don’t know about you, but any surgical procedure involving my eyes terrifies me. I mean, if a doctor operating on your leg makes a mistake, you may walk with a limp for the rest of your life, but if your eye surgeon makes a mistake…

I understand before the advent of lasers, they used to perform iridotomies by hand. Isn’t technology wonderful?