A comfortable fitting spectacle frame defines ultimate customer satisfaction. The process starts with selecting a frame with adequate dimensions, which will allow manipulation and adjustments once the lenses have been fitted. Nobody’s head or face is exactly symmetrical and each individual has unique features, which will impact on how a spectacle frame sits on the face. Ears are usually not positioned exactly at the same height. One ear may be higher or lower than the other. The bridge of the nose may be relatively high or low in relation to the eyes. A head may require very long temples (side pieces) or very short ones. The position of the ear, where the temple sits in relation to the place where the frame sits on the nose, can hugely influence the fit and optics of spectacles. It’s very important that the optical dispenser takes note of all these features and selects a frame that can be fitted to overcome them.
Sweeping the frame
This is a phrase my colleagues and I came up with many years ago. The reason for sweeping the frame, before we plunge into fitting it to the face, is that it will avoid a compensating error. This ensures that there are no misalignments hiding in the frame before you place it on the customer’s face. Misalignments an easily occur during the cutting and fitting process of the lenses and with temperature changes when frames are in storage.
Once the frame has been swept and then placed on the face, any misalignment can only be present because of anatomical features of the customer’s head and face. Now, if the frame is hanging lower on the left side, we know it is caused by uneven ear height and not by an inherent misalignment of the frame itself, such as a twist in the bridge.
Note: this is done before fitting the frame on your patient
Step 1: View from the top
- Look for a twist on the bridge. This is best done by holding the frame so that you can view it from the top (Fig.1). Tilt the frame slowly so that the bottom rims appear. They should appear at the same time. If you see more of one rim, there is a twist in the bridge.
- Look for excessive bend of the frame front, or a negative bend. It should never be dead straight; the ideal being a gentle curve around the face.
Step 2: Top view of angle of front with temples
The angle between the frame front and the temples should be more or less ninety degrees.
Moreover, they should be equal and symmetrical.
Step 3: Side view of temples – are they aligned?
You don’t want one temple pointing up or one pointing down. They must be exactly parallel. A twist in the bridge will result in this and should be seen as the primary cause. Heating the frame on the bridge, the twist can be corrected and the temples will be parallel. If you don’t notice the twist in the bridge and just angle the temples to bring them parallel, you will create the compensating error!
Step 4: Temple curl
You don’t want the curl at the temple tip to be too early ( A), because it will lift the specs and exaggerate the pantoscopic angle or make them appear lob-sided. Flatten the curls out. As a starting point you want the temples resting on top of the ears, without the curl interfering as is the case in B.
Step 5: Nose pad alignment
Very often, metal frames come out of manufacturing with the nose pads angled too far away from the frame rim. This will cause the lenses to sit too far out from the eyes. Apart from optical implications, it makes the frame look ugly on the face. As a starting point, push the nose pads in with your thumb and ensure that they are angled nicely.
Fitting the frame onto the face
Once the frame has been swept, a poor fit can only be induced by facial features. Now the dispenser can go to work by applying the normal rules of fitting.
1. FRONT VIEW
Look for horizontal tilt.
2. TOP VIEW
Both sides must be the same distance from the eyes ( eye brows not always symmetrical) You want a gently curve around the face – not straight or a negative curve.
3. SIDE VIEW
Pantoscopic angle. This angle is determined by the point where the temples rest on the ears and the top of the bridge of the nose. An incorrect pantoscopic angle, can definitely affect vision.
4. TEMPLE WRAP
Check that the temple wrap does not apply any unwanted pressure on the wearer’s temples. A temple wrap that is too narrow will push the frame forward to slide down the wearer’s nose, thus making it uncomfortable to wear and will produce indentations in the wearer’s temples. A temple wrap that is too wide will also result in a frame that is sliding down the nose.
5. TEMPLE LENGTH AND TEMPLE CURL
6. THE BRIDGE
Nose pads must be aligned to fit flush with the nose. There are three angles to consider when adjusting nose pads: The frontal, splay and vertical angles. Both nose pads should look symmetrical, unless the patient has some asymmetry such as a broken nose and should be equidistant from the frame.
Carefully compare the fit of the current spectacles with the fit of the new spectacles. Any significant difference should alert the dispenser to potential problem areas. I have seen some optometric staff place the spectacles with the temples on a flat surface, to see if they are aligned. If you are doing this, you are missing the plot.