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October 18, 2006

The Fitting Triangle

by @ 11:58 pm. Filed under Optical Guides

I have written my first article for a magazine called Opticourier. It’s a pretty good magazine. Tell me what you think.

Al

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The Fitting Triangle

(Written for Opticourier.com)
As an optician, it is our desire to make our patients happy with their eyewear choices. It may also be the case that despite buying premium products, patients may not be entirely happy with their purchase. Their dissatisfaction may be corrected with some simple adjustments that can greatly improve the way the spectacles feel on their face. Opticianry is as much an art as it is a science and knowing how to adjust glasses properly will ensure that your patients understand that you are more than just a salesperson. We can ease their pain and frustrations with their spectacles. In my studies of Ophthalmics, we went over a topic known as the fitting triangle.
The fitting triangle is a simple concept, but may be difficult to master at first. I would refer you to two textbooks that are reliable, accurate and which I will be gathering most of my information from; Russell L. Stimson “Ophthalmic Dispensing” 3rd edition. and Clifford W. Brooks, Irvin M. Borish “System for Ophthalmic Dispensing” 2nd edition. The triangle itself is an overhead view of a patient’s head with the frames making contact at the tops of the ears and at the nose. This is the only place frames should touch a patient’s face. So how does one make it happen and why is this concept important? Patient complaints can range from glasses slipping forward, allergies to a component in the frame and/or headaches or marks on the side of the patient’s head. By no means is this a comprehensive list of complaints, but it’s a good start.
Forward slipping glasses result as the frame’s temples push on the patient’s head. A patient who has marks on the side of their head from their frames will probably be complaining about their glasses slipping forward. We also find some patients with contact dermatitis caused by the contact between their skin and the frame. Most patients will be allergic to nickel more than other metals. Frame materials that contain nickel include… well, nickel frames obviously, as well as monel, German silver/nickel silver and some stainless steel frames containing traces of nickel. Some titanium frames that advertise as memory metal use nickel alloys in its construction. The best way to know which frames contain nickel is through your frame distributor.
Marks on the side of the head may also leave a patient with headaches. The constant pressure from the frame’s temples on the side of the head can be painful as well as leave the skin somewhat irritated as well as the patient. The best way to fix this is to bow the temples until they reach around the skull and touch at the tops of the ears. As you bow the frame, widen the temples until you finally achieve this. You can use your hand or nylon eyewire pliers. Do not be surprised at how much bowing you have to do. I can only describe my head as a bowling ball and the only way to get around to my ears is to bow the temples. Some frames now come slightly bowed and although this helps, you may have to add some more. Be careful not to bow too much or there will be excessive pressure on the bridge. Try not to make the frames into a head clamp. The temple bends are to be placed 1-2 millimeters behind the tops of the ears (a.k.a. ear root – where the top of the ear meets the skull) and follow the ear crotch down 1 – 1.5 inches. If the temple is too long, cut accordingly. The bend itself should be sharp. The temples should contour the skull and NOT the back of the ears. There should be a millimeter separation between the ear crotch (the posterior descending slope of the ear that meets the skull) and the temple. Letting the bent-down portion of the temple touch the ear (except at the top of course) can irritate the skin, especially in the elderly.
The next adjustment that needs to be tackled is adjusting nose pads. The goal is to make the nose pad sit flush against the side of the nose distributing the weight of the frame evenly. There are three angles to consider when adjusting nose pads: The frontal, splay and vertical angles. It goes without saying that both nose pads should look symmetrical unless the patient has some asymmetry such as a broken nose and should be equidistant from the frame.
The frontal angle is best viewed from the front, go figure. It is the angle that is closer at the top and wider at the bottom. This angle can usually be adjusted using nose pad pliers or a pair of snipe nose pliers. All that needs to be done is to match the angle of the nose as it widens.
The splay angle is viewed while looking through the spectacles. The splay angle is the angle that increases or decreases the amount of nose pad surface that faces you. Individuals who have shallow bridges on their nose tend to require more splay for example.
The vertical angle is changed by rotating clockwise or counter-clockwise while looking directly at the nose pad. The vertical angle should always follow gravity. If one changes the pantoscopic tilt of a frame, one must also adjust the nose pads vertical angle so that it follows gravity (sit vertically on the face) and distributes the weight of the frame evenly.
Finally, there should always be some pantoscopic tilt. Pantoscopic tilt is when you bend the temples so that the lower part of the frame sits closer to the face than the top. Most progressive manufacturers suggest between 8 – 12 degrees of pantoscopic tilt. There is also a correspondence between placement of the optical center of a lens and the amount of tilt needed to avoid inducing cylinder. Every 2 degrees of tilt is equivalent to decentering the optical center up a millimeter.
Following the concept of the fitting triangle will yield happier patients. Even though these guidelines are helpful, it’s important to know when to break the rules. Patients that use oxygen tanks with a nasal cannula will require some thought as to placement of the bend as well as frame selection, that minimally interferes with their breathing apparatus. For the most part, these guidelines will provide a way to establish loyal patients who appreciate our services. Good opticians can sell a patient premium eyewear, but the ability to make glasses comfortable and predictable is what makes a great optician.

Stimson, Russell L. (1979). “Ophthalmic Dispensing.” 3rd Ed.  Charles C. Thomas – Publisher: Springfield, Illinois

Brooks, Clifford W., & Borish, Irvin M. (1996). “System for Ophthalmic Dispensing.” 3rd Ed. Butterworth-Heinemann: Boston

One Response to “The Fitting Triangle”

  1. Theresa Says:

    Great article! I am just getting back into optical after an absence of 10 years! The information was helpful. Thanks!

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Optician n. One who is extensively trained in the interpreting of ophthalmic prescriptions and applies that knowledge to obtain the optimum visual and safety performance for the patient in a pair of spectacles or contact lenses.

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