Aesthetic, comfort level, functionality factors are all equally important when selecting frames. But comfort level of a frame can be affected by the material of the frame, size of the lenses, and how the frames are fitted on the wearers. The following factors should be considered when choosing a frame:
- Structure - The type of the prescription and the lens material play a major role in terms of the overall structure of the frame, especially semi-rimless and rimless frames. For example, installing thinner lenses on rimless are more likely to fracture, unless you use certain materials. And screws on rimless frames may loosen easily, which can cause vision disruption for astigmatism wearers because the optic axes of the lenses change. On the other hand, overly thick lenses are also not recommended with half or rimless frames due to aesthetic factor. For people who have stronger prescription on one and minor prescription on the other eye, when choosing rimless frames, it will visually emphasize the difference in lens thickness. As for far sighted vision, the lenses are more curved, which causes the temples to close in when finished. For this kind of lenses, rimless frames installed on the back of the lenses are recommended.
- Frame Size - In order to select the right-sized frames, there are few things we should consider: face shape and size, pupil distance, viewing area and the lens edge thickness. Ideally the geometric center of the frame shape should be as close to the center of the pupil as possible to avoid decentration. But in some cases pupil height in the frames (aka seg height or OC height) are required more. For example, bifocal and progressive lenses should have more seg height to ensure enough viewing area for the near vision. Under some circumstances, (such as drivers) wearer may need a larger frame for broader viewing range. Therefore, wider rims and bigger frames are usually recommended. However, the sizes of the frames are proportional to the mass of the lenses. So for patients with higher prescription, we would suggest smaller frames to reduce the pressure on the nose caused by the weight of the glasses. Another way to decrease such pressure is to choose the frames with larger nose pads, which can evenly distribute the weight on the nose. As for kids, we should consider low price range, high durability and flexibility as well as safety, because they grow fast and are usually careless with glasses.
- Nosepads (Bridge) - The main function of the nose pads is to support the weight of glasses on the nose. Ideally it would distribute the weight on both sides of the nose evenly. There are no standard guidelines for nose pads. However, we must consider the size of the nose, length of the eyelashes, and the space between the forehead and eyes. It would be unpleasant to have eyelashes touching the lenses or cheeks touching the bottom of the frames when smiling. For bifocal or progressive lenses, it is important to pick frames with adjustable nose-pads in order to fine tune the fitting for individuals.
- Frame selection for progressive lenses - It is very important to match progressive lenses with suitable frames. The followings must be considered: (1) The seg height of the frame must be able to accommodate the design of the progressive lenses. (2) The reading area of the frames should adequate. For example, aviator styles tend to be narrower towards the inner corner, hence, it is not recommended for progressive lenses. (3) The adjustable nosepads are preferred, where after adjustments, the distnace between the eye and lenses should be about 12mm in order to achieve the best visual field. (4) To maximize the reading area, adjust the lenses to tilt foward about 12 degrees. (5) To avoid poor visual resolution, the selected frame should be made of durable materials and resistant to distortion.
- Frame selection for high-prescriptions - For people who have high prescriptions, it is important to consider the frame shpae, size and structure. Eg. (1) A bolder frame should be chosen to minimize the lens thickness showing on the sides. (2) Smaller frames can minimize the lens mass. (3) Find a frame that the wearer's pupil is closer to the middle, which could also minimize the thickness and weight. (4) Nosepads with bigger size and silicone material would help reduce the pressure on the nose and prevent glasses from slipping due to the weight of the glasses. (5) The position of the nosepads should remain some distance apart from the rims to ensure that the thick lenses can be assembled without affecting the fitting. (6) Select sturdier and more durable frames to support the heaviness of the glasses.
