|The Y Stick consists of a lightweight clip, measuring scales for each eye, a free-swinging pendulum-like assembly, and a break.|
|Notice how the two sets of horizontal pins are not in alignment in this photo. This means the patient’s natural-looking straight-head posture is not in alignment. Lowering the head in this case will bring the pins into alignment.|
Each issue, Tech Tips will explore some interesting aspect of optical technology. This month we look at obtaining more accurate fitting heights.
Here are some tips to follow when using measuring devices.
Any lab will tell you that the most common reason for lenses being returned is that they weren’t properly positioned for the wearer. That’s terribly inconvenient for the patient and horribly costly for the lab, lens manufacturer, and retail office. While the ultimate solution for this problem is obtaining and properly using one of the new digital measuring devices that have come on the market in the last few years, many offices still don’t have one so some kind of analog solution is needed.
There’s one product that has found favor with a number of opticians-the Y-Stick. Invented by an optician, the Y-Stick works to find and maintain the patient’s natural head posture so accurate fitting height measurements can be taken.
The most common problem occurs when the optician and the patient are not positioned along the same line of sight. If the optician sits higher than the patient, the measurement taken will be higher than it should be and if she sits lower than the patient, the measurement will come out lower than it should be. This occurs even though the optician has taken the measurement, viewed the patient’s eye properly, and measured super precisely. The reason for the error is called parallax, which occurs when the optician and the patient don’t view along the same line of sight.
It is possible for the optician to adjust her chair or stool to position herself higher or lower as needed, but not every office has adjustable furniture and quite frankly, this is time-consuming and may appear a little silly to the patient. Some opticians (like me, for example) have suggested having the tallest person (you or the patient) lean forward to effectively reduce his height. That’s a simple solution and although it isn’t perfect, it’s convenient.
The Y-Stick is the perfect analog solution for this problem. This device consists of a lightweight clip, measuring scales for each eye, a free-swinging pendulum-like assembly in the center of the device, and what the manufacturer calls a “break” that locks the pendulum in place. The pendulum always orients itself 90Ëš to the floor, no matter how the patient holds her head.
The Y-Stick is positioned onto the frame and secured. Once done, the optician places the frame on the patient and asks them to stand and face some object at a distance. As they do, they comfortably assume their natural head position. As they look at the distant object, the optician locks the break. This locks the patient’s natural head posture in place on the device. From this point on, no matter how the patient may move, the optician can always return the patient to the “straight ahead” viewing position locked in the device. This is done by viewing two sets of horizontal pins near the center of the device. When they are parallel to each other, the patient’s head position is in its original straight ahead natural head position. It’s simple and ingenious, and it works!
Taking fitting height measurements is not as easy since the millimeter scale for each eye is positioned far from the patient’s eyes. Determining which line on the scale intersects the patient’s pupil for each eye is made easier by shining a penlight into the patient’s eye and determining where the corneal reflex intersects the scale. It should be mentioned that the fitting height measurements should be taken only when the two sets of horizontal pins are properly aligned. If they are not aligned, a parallax error will occur.