This article is best viewed in a PDF Format.
|
|
|
|
The Oriental face is known for its small nose projection (the 'flat' nose), creating difficulties for those who try to fit plastic frames to Asian faces. Due to the smallness of the Asian anatomical nose bridge, such frames typically sit too low on the face (Figure 1). A second, less obvious problem is that for frames that do manage to sit at the correct height, the back vertex distance is often too short (Figure 2), causing the wearer considerable annoyance as their eyelashes will often contact the back of the lenses, leaving oils, mascara, and causing the lenses to become dirty.
Some manufacturers have attempted to deal with these challenges by producing 'Asian-fit' frames that possess extended nose bridges (Figure 3) to fit the anatomically flat Asian nose, but these modifications often still prove inadequate. One way to improve the fit of these plastic frames is to mount accessory nose pads onto the frame bridge.
The first step is to have the patient wear the frame. For plastic frames that are 'close' to sitting at the correct height for the patient's eyes, or for frames that do sit at the correct height but are at an unsuitably short vertex distance (Figure 2), we recommend adding nose pads in the manner described here. For frames that sit significantly too low on the face (Figure 4), we recommend the addition of nose pad arms which we described in Part 1 (Optician, January 23, 2009).
For the current technique, while the patient is wearing the frame, observe where the patient's anatomical nose bridge contacts the frame nose bridge, and mark that area using a water-insoluble marker (Figure 5). In general, a narrow nose will be marked at a higher position along the bridge compared to a wider nose. A narrow nose will also be marked deeper into the bridge (namely, closer to the front of the frame) compared to a wider nose.
A hand-held drill is used to create the holes through the frame at the position of the markings (Figure 6). The diameter of the drill bit will vary depending on the size of the metal insert of the nose pad, but a diameter of 2.0mm should be adequate for most jobs.
Once the holes are made (Figure 7), the metal insert of the nose pads can be pushed through (Figure 8). The insert will usually be square or rectangular in shape with a length of approximately 2mm. Because the hole is circular and the insert is rectangular, the pad will fit snug. The drilled hole will also take the shape of the insert, and eventually become rectangular in shape (Figure 9).
The angle of insertion of the nose pads can also be controlled in this technique. An estimate of the desired angle can be made when the frame is sitting on the patient's face by comparing the splay angle of the frame bridge to the splay angle of the patient's nose. Drilling can be purposely done at an angle that will encourage the pads to be fixed at the desired angle. Otherwise, if the drilling is done perpendicular to the frame, the nose pad will permit some adjusting with gentle force even after it has been inserted. Once inserted, if the fit is snug, the nose pads should remain in place for the life of the frame. If they do become loose, epoxy or the addition of a screw may be used to fix them (Figure 10).
The addition of nose pads to plastic frames will allow patients with flat nose bridges wider access to frames that would normally not be a proper fit for them (Figures 11, 12). We have had considerable artistic and commercial success with the technique described here, but some level of practice is required before one becomes adept at using it. The effort, however, is indeed encouraged and we wish you good luck. ?