It is the age of state-of-the-art technology: free-form lens designs, ultra-thin materials, high-quality anti-reflective coatings and light weight frames, to name but a few. Opticians are in a position to make patients the finest pair of glasses they have ever had by using all the resources at their disposal.
However, without precisely fitting and adjusting the finished product to the patient, with the very same attention to detail given to the choice of material, design and treatment, it may compromise both you and your patient’s expectations. In fact, without quality dispensing techniques, the eyewear may as well be a pair of 62-eye aviators, photogray glass, executive trifocals. No offence to those out there who like these. The point is fashionable, high-quality eyewear deserves professional, high-quality dispensing. New products and sophisticated technology purchases today require precision and comfort to go along with great vision and looks.
The patient’s long-term satisfaction with their new eyewear depends on how comfortable the eyewear is and how well the optician has done their job in the fitting and adjustment process. The following information is intended to provide an overview of the fitting and adjustment process and its importance in the services performed by the optician.
It Starts at Frame Selection
Eyewear adjustments should begin at the time of frame selection. It is important to pre-fit the frame to the patient prior to measuring segment and optical center (O.C.) heights. Attention should especially be made to the degree of pantoscopic tilt and the way the nose pads, if present, sit on the bridge of the nose. These details can dramatically affect the measurements taken.
First, inspect the touch of the nose pads, or the way the bridge of the frame rests on the nose: look for good alignment of adjustable nose pads, or good touch of a zyl saddle or keyhole bridge. For adjustable pads, each pad should be flat on the side of the nose without their edges bunching up the skin. The bridge of a zyl frame should touch a large portion of the side of the nose for good support and comfort. Be sure that the edges or corners of the bridge won’t leave red marks or indentations on the nose. This is especially important on the crest of the nose.
Once the frame is in good alignment, take any measurements that are required, place the order with the lab and wait for the lenses, or completed glasses, to be returned.
Once the lenses have been fabricated and mounted, the frame should be put in “Standard Alignment” (also called four-point touch) as part of the verification process. Standard alignment refers to the process of preparing the frame for the patient by making sure it is not distorted from its natural shape.
Check the frame for horizontal and vertical alignment; temples should be at 90 degrees to the frame front when extending backwards (Figure 3A) and the frame front should not be propellered, or skewed in one direction or the other, when viewed from above and sideways sometimes referred to as “Xing” (Figure 3B). It should also have a small amount of faceform.
The “Table Top Test” is a good way to check for standard alignment: Sit the inverted frame on a table top with the temples open and there should be no wobble. (Figure 3C)
Dispensing is the optician’s opportunity to shine. The patient gets to see the eyewear that has been carefully designed for them. Do not take the plastic lab tray out to the patient when dispensing new eyewear—this just kills the presentation.
Let the patient know how special their glasses are by presenting them like a piece of fine jewelry. Make it known that their purchase has been handled with the utmost care—for example, any cloths used to clean the lenses should be clean, not stained and dirty. It is recommended the optician place the glasses on the patient for the first time in case substantial additional adjustment is needed, in which case the eyewear can be removed immediately to avoid a negative first impression for the patient.
Adding the correct amount of pantoscopic tilt brings the optic axis of the lens in line with the center of rotation of the eye—improving visual comfort for the patient. With zero pantoscopic tilt, the lens optical center and optical axis will pass through the center of rotation of the eye only if the pupil is at the same height. However, the pupil is rarely vertically centered within the lens—it is generally positioned approximately 5mm above the datum line, or frame midline.
If zero pantoscopic tilt is applied to the frame, the wearer may experience some visual discomfort from lens aberrations induced by changes in sphere and cylinder powers due to the misalignment. In addition, glasses look better with some degree of tilt, on average 7 to 10 degrees.
It is important to note that for every 2 degrees of pantoscopic tilt added to the frame front, the O.C. of the lens should be lowered 1mm. As mentioned above, most eyes sit about 5mm above the frame mid- line, so it is important that the amount of pantoscopic tilt needed, usually 5 to 15 degrees, is applied to the frame prior to measurements being taken. The O.C. height ordered must factor in the degree of tilt applied to the frame—if no O.C. height is specified, most labs will place it at, or just above, datum, assuming approximately 7 to 10 degrees of tilt. If the frame is not pre-fit, the relative (Figure 1: Pantoscopic Tilt) placement of the segment, or O.C., will be misaligned with the line of sight of the eye in the finished lens. (Figure 2)
To place the glasses on the patient, carefully slide the eyewear on, gently spreading the temples if necessary, guiding the temples over the ears and down behind the ears.
If the patient prefers to wear the glasses at a specific place on their nose (vertex distance), this should have been considered during the initial selection and measurement process. Changing the vertex distance can change the effective power if dealing with high powers, and also affects the segment and O.C. heights. Increasing the vertex distance will make a “plus” lens effectively more plus and a “minus” lens effectively less minus. Conversely, decreasing the vertex distance will make a “plus” lens less plus and a “minus” lens more minus. When dealing with high powers, above +6D the optician must factor in any significant variations from the refracting vertex distance to the worn vertex distance when ordering lenses.
If vertex compensation is not applied to the written Rx, the patient will be unhappy with the quality of vision using their new eyewear. With regards to the effect of varying the vertex distance on segment and O.C. height—decreasing the vertex distance generally results in sliding the frame higher up on the nose effectively raising the relative heights. On the other hand, increasing the vertex distance will effectively lower the relative heights, generally moving the frame lower down the nose. This will become increasingly more important as free-form lenses become more widely used—many requiring vertex distance measurements to be provided when the lenses are ordered. A distometer (Figure 4) can be used to quickly and easily measure the vertex distance of the glasses in the “as worn” position.
Although the frame was prefit to the patient, the process of glazing and insertion of the lenses can frequently cause some mis-alignment and create the need for fine-tuning. If present, the nose pad position should be fine tuned so the frontal/spread angle, the splay angle and the vertical angle are all correct for the patient. Slim pad arm adjusting pliers (Figure 5) work well for this. The frontal/spread angle is how far apart the pads are. The splay angle is their angle to the nose, which should complement the angle of the nose at the point at which the nose pad is sitting. The vertical angle is controlled by the size of the loop of the pad arm—the standard position requires the bottom edges of the pads be closer to the eye wires than the top edges of the pads. The objective is to make all three angles sit flush with the skin to achieve superior comfort.
Generally, the angles should be such that the pads are angled slightly toward the face to follow the natural contour of the side of the nose (Figure 6). A good test is to raise and lower the frame and closely observe the nose pads from the front as they touch down on the nose.
The top and bottom tip of the pads should touch down at the same time. If one tip or the other touches first, that part is going to apply too much pressure on the nose and possibly cause irritation. Also, looking at the nose pads from a “head on” position, the cushion side of the pad should not be visible. In addition, to maintain the correct vertical angle, the loop of the pad arm should be small in order to keep the vertex distance to a minimum (Figure 7).
When fitting patients with very flat bridges, such as those of Asian ethnicity, frames with nose pads are usually the best option. However, fitting nose pads to these patients can be very challenging and takes some practice. The splay angle has to be changed so the pads are sitting almost parallel to the face. Also, the loop of the pad arm may need to be made larger than standard to keep the frame off the patient’s lower cheeks by changing the vertical angle (Figure 8). Bent Snipe pliers are good tools for this purpose (Figure 8a).
Once the nose pads are sitting well, check the alignment of the frame front. It should be level. If the patient’s face is asymmetric, this can be challenging. In order to achieve premium vision, the horizontal optical centers of the lenses should be level with the pupils. However, if the eyes are vertically uneven, the patient is not going to be happy with a crooked frame, regardless of how detailed an explanation of the effects of prism may be presented. In a situation like this, try to achieve a happy compromise. Remember, a patient is basing their first impression of how their new eyewear fits on several things including how level their eyebrows are relative to the top of the frame and how comfortable the frame feels.
There are two schools of thought when dispensing progressives—ink markings or no ink markings. If you are of the ink markers, make sure that the markings are still on the lenses; if not, re-mark the location of the fitting cross. If markings are on the lenses, advise the patient that initially these may obscure their vision and will be removed once alignment has been verified. Let the patient know the fitting marks are there to allow the fine adjustments necessary to customize the fit of their eyewear. Inform them that handling during glazing and insertion of the lenses can occasionally cause misalignment and the need to re-verify alignment.
The no ink marks folks believe if the lenses were measured correctly, there’s no need to check, only if troubleshooting is required. In fact, the lenses should be pristine to show off those great AR lenses the patient ordered. Also, suggesting the markings be left on to verify fitting could suggest to the patient that the optician lacks confidence in his or her abilities to measure accurately. It’s your choice.
If the frame front is tilted, always correct in the direction of the error.
If the right side of the frame front is lower than the left, increase the pantoscopic tilt of the right side (angle temple down), or decrease the pantoscopic tilt of the left (angle temple up) (Figure 9). Use a pair of wide jaw angling pliers for this task. It securely holds the temple and end piece together so as not to put excessive strain on the hinge. (Figure 10).
Here’s the scene: The lab has returned the patient’s new eyewear and you sit before the patient ready to dispense the glasses. The nose pads are sitting well on the bridge and the frame front has been made level.
Pantoscopic Tilt — Check the amount of pantoscopic tilt applied—as mentioned earlier, it should be between 5 and 15 degrees. Have the patient turn their head so the angle of tilt can be evaluated from the side. For most lenses, the need to precisely measure the pantoscopic angle rarely presents itself. However, for new personalized lenses, there are PD rulers and gauges that display protractor markings or have a needle device that points to a particular angle. The new personalized freeform lenses do require vertex, tilt and faceform measurements so get ready.
Become familiar with the visual appearance of angles between 5 and 15 degrees (Figure 11). This allows the optician to estimate the angle required when the patient is wearing the frame.
This is especially important with a bifocal or progressive, making sure the segment is in the correct position when looking down to read. If there is an insufficient amount of pantoscopic tilt, the patient can be looking under the frame or, at least, the field-of-view for near work will be narrowed due to the increased vertex distance between the eye and the segment. This is also referred to as the “keyhole effect.”
As the eye rotates along the vertical axis, to look up or down to read, the tilt of the frame maintains equal distances between the lens and eye maximizing fields-of-view, ensuring the optical axis of the lens passes through the center of rotation of the eye to maximize visual comfort.
When changing pantoscopic tilt, use the wide-jaw angling pliers to change the angle of the temples while bracing the frame front with a separate pair of pliers. Carefully apply force in the direction needed. This is especially important when handling three-piece rimless mountings. Protect the lens from the force necessary to change the tilt (Figure 12) with bracing pliers such as the “three-piece adjusting pliers.”
Vertex Distance— Lenses should appear equidistant to each eye. With the patient seated and tilting their chin down, observe the frame front from above by standing and looking down. If one lens appears closer to the eye than the other, the fitting error may be due to the temples being at unequal angles to the frame front from the endpiece, when extending backwards. On the other hand, the patient’s eyes may simply be more inset on one side than the other. (Figure 13)
Whichever lens is closer to the eye, the same side temple needs to be brought closer to the head. Reduce the horizontal angle between the frame front and the temple using a pair of flat/round metal pliers at the end piece. (Figure 14)
Conversely, increasing the horizontal angle between the frame front and the temple of the opposite side is also an option, effectively moving the temple away from the head. The same way pantoscopic tilt affects the vertical placement of the lens optical center, face form—positive or negative—will also affect the horizontal placement of the lens optical center.
However, it is NOT recommended to compensate for face form by ordering an incorrect PD. It will create lateral prism. On occasion, patients’ glasses will get out of adjustment due to wear and tear, and the patient resorts to bending them—adding face form. The patient then adapts to looking through their lenses this way and when receiving new glasses, may complain about the difference in the PD and its effects on vision. Some adjustment and period of adaptation may be necessary to make the patient comfortable while the optician works with the patient to get back to the way their eyewear should fit. Applying positive face form so the frame follows the natural curve of the face is a good rule of thumb, thus minimizing visual problems for the patient as their eyes move laterally. (Figure 15)
The Fitting Triangle
The frame should touch at only three points, which form “the fitting triangle”— the nose, and the top of each ear. If the frame is touching the head at other places, the frame selected may be too small for the patient.
Temples leave “railroad tracks” (impressions of the temples) along the sides of the head toward the ears; this will actually force the frame to slide forward. Try spreading the temples out horizontally away from the frame front at the end piece; again for metal frames use a flat/round metal plier. With zyl frames, heat up the frame at the end piece and apply pressure using the hands to increase the horizontal angle between the temple and frame front equally on both sides. Then using eye-wire shaping pliers (or well-trained fingers) with the concave side facing toward the inside (Figure 16), apply a gentle curve to the temples so they are not in contact with the head. With zyl temples, heating may be necessary to permit this manipulation. Try for touch only at the top of the ear.
Behind the Ears
When adjusting behind the ears, the temple should curve just above the ears and follow the line of the back of the ear. Temple bending pliers can be used or welltrained fingers. (Figure 17) It should be at an angle of approximately 45 degrees from the temple bend at the crest of the ear and it should not put excessive pressure on the back or top of the ear. (Figure 18)
If the bend begins too soon before the crest of the ear, it will rub and irritate the top of the ear. It will also cause the temples to rise up from the ears adding tilt to the frame front. If the bend begins after the top of the ear, the temple will either not conform to the curve of the ear or it will need to be bent at a greater angle than 45 degrees and the tip will rub and irritate the back of the ear. The glasses will also slide down the nose.
When adjusting temples, be careful to be aware of the mastoid process. This is a bone that protrudes from the skull, behind the ear; in some patients it is more prominent than others. If the temple tip rubs against the mastoid process, it can cause serious discomfort so should be avoided. Regardless of the optician’s skill level, a visual inspection of the temples behind the ears should always be done to ensure optimum comfort for the patient.
Prior to checking behind the ears for fit, always ask the patient for permission. Some patients are uncomfortable with an invasion of their personal space. If the patient is a minor, always check with the parent. When checking behind the ears, look for white pressure points where the temple tip is touching the head and ear. If present, adjust the temple tip away from the pressure points until resolved. The temple bend should also follow the line of the side of the head. In order to do this the tip will need some angling in toward the head.
Be sure the bend point of the temple is NOT the only part of the temple touching the head behind the ear leaving a space at the bottom between the head and temple tip. Conversely, the temple should not just be touching the head with the lower tip of the temple creating a space between the head and the temple at the top of the ear. In the first instance, if the temple is in contact with the head only at the bend at the top of the ear, adjust the temple tip so that it angles in toward the head just enough to gently touch. In the second, if there is a space between the temple and head at the bend, the tip is angled in toward the head an excessive amount; adjust the temple tip away from the head so it is bending in less.
Occasionally, in this case, the temple itself may need angling “in” a little at the end piece. A flat/round metal plier can be used with a metal frame to reduce the horizontal angle between the temple and frame front, in order to provide a snug fit. Heat and pressure using the thumbs, or a tabletop, at the end piece may need to be used with a zyl frame to obtain the same result. The more touch, the more friction and the better the temples will do the job i.e., hold the glasses in place.
Although temple length should be evaluated as a part of the initial frame selection, sometimes a frame may be selected that does not offer the option of an alternate temple length. Although patients may not express a concern if a temple is a little short, extending the temple bend backwards toward the end may provide an acceptable fit. Be sure that there is enough touch to provide good frame stability. If the temple is too long, however, most patients will be unhappy with an inch or more of the temple sticking out below their ear. Once again, don’t settle for second best—take care of every detail.
If the standard temple is metal with slipon covers as temple tips, it can often be easily modified to accommodate the need for longer or shorter, temples. In the case where the standard temple is too short, straighten the temple out and simply slide the tip cover off about 5mm and then readjust the bend. If the standard temple is too long, straighten the temple out and completely remove the tip cover. Using a pair of cutting pliers (Figure 19), shorten the metal temple core by 5mm to 10mm, slip the tip cover back on and reapply the bend. Some metal temples have a different shape or form beyond the tip cover so it may also be necessary to modify the tip cover by shortening it by the same amount as the temple. Using a file or fine emery paper, smooth the rough tip of the core and the left over rough edges of the tip cover before sliding on the temple cover.
Often polishing the cover opening helps reduce any roughness that might irritate the ear and get caught in the patient’s hair. Re-adjust the bend and repeat as needed until the required length is determined. Initially, this may take some time to perfect, but with practice you will become skilled in determining the shortening required.
Unfortunately, this is more complex with zyl temples and often not possible since zyl has a metal core that may protrude from the end once cut. While modifications can occasionally be done, it is often best to discourage zyl frames with inappropriate temple lengths. Most metal temples can also be modified to accommodate cable temple tips, if beneficial for the patient, by using a similar procedure as described above. Specific directions on temple modifications can be found in “System for Ophthalmic Dispensing” 3rd Edition by C.W. Brooks, an excellent reference for opticians of all levels.
How Important are Adjustments
In order to determine what patients expect the most from opticians, 100 patients were randomly surveyed over a two-month period in a private, three-doctor optometric office.
On a scale of 1 to 5, (1 = “Not at all,” 5 =“The most important”) patients were asked
How important is it to you that your optician is:
- Able to fit your glasses well
- Able to select a good choice of frame
The results of the survey were:
- 93 percent of the patients consider being able to fit glasses well as their most important need from their optician.
- 73 percent of the patients indicated their greatest frustration with previous eyewear was that the eyewear was poorly fit and uncomfortable.
This strongly suggests that opticians need to be skilled in the art of eyewear adjusting and fitting, and patient comfort is the key to happier patients.
The optician’s major role, although highly technical, is to use their skills and expertise to ensure patient comfort and satisfaction with their eyewear. Taking the extra steps at the time of dispensing will result in less time spent re-adjusting glasses because the patient has to return due to a poor initial fitting. It also ensures less inconvenience for a patient having to return to have done what should have been done in the first place.
Most importantly, having the patient leave the office totally satisfied with ALL of the services they received—having the utmost confidence in the entire staff and their abilities, and excited to tell others about their wonderful experience and show off their new eyewear that they will enjoy wearing for many years to come.
by Andrew Bruce, ABOM