Things to keep in mind when choosing a frame

One of the most important things when selecting frames is to look at their specifications. Sometimes, if a new salesperson in an optical store helps you pick frames, they often end up choosing ones that don't really suit you. By understanding the specs, you can make the right choice for yourself.

Lens width + bridge width – pupillary distance (PD) ≤ 6. This is especially important for those with high prescriptions. If you choose incorrectly, not only will it look bad, but more importantly, it can harm your eyes.

In a proper scientific eyewear fitting process, we recommend a frame parameter where Δ = (Lens width + Bridge width) – PD ≤ 6 mm. Why?

From a health perspective, lenses naturally have a prismatic effect. The closer you get to the edge of the lens, the stronger the prismatic effect (prism diopter = distance from the optical center × lens power). This prismatic effect causes blurred vision, distortion, and a sense of wobbling when looking through the edges of the lenses, significantly increasing the strain on your eyes, which leads to visual fatigue and worsening of your prescription.

The larger the Δ value, the more of the lens edge is retained, and, naturally, the stronger the prismatic effect. Many of you have probably experienced this when switching from small frames to large ones. As mentioned earlier, the prismatic effect is also directly proportional to your lens power. So if your prescription is low, the condition can be relaxed somewhat.

From an aesthetic point of view, the larger the Δ value, the more it gives the illusion that your eyes are squinting inward (commonly known as cross‑eye appearance). For example, if someone with a PD of 55 mm wears frames with an M value (lens width + bridge width) of 70 mm, then Δ = 53+17‑55 = 15 mm, far greater than 6 mm, and the visual appeal is significantly reduced.

Have you ever encountered these three situations while wearing glasses?

1. The top edge of the frame touches your eyebrows, and the bottom edge touches your cheeks.
2. Your freshly cleaned lenses get blurry in the center after a short time because your eyelashes keep brushing against them.
3. No matter how you adjust them, the glasses won't stay up — even after adding various anti‑slip sleeves behind your ears, the lenses still sit almost level with the top rim of the frame.

If any of the above happen, it means you chose the wrong frame.

For those who prefer plastic frames (with integrated nose pads): If your nose bridge is not very high, be sure to check whether the nose pad position of the frame suits you. So, how should someone with a low nose bridge choose plastic frames? The "nose pad position" does not refer to the bridge width marked on the frame, but rather the height of the nose pads and the distance between the highest points of the nose pads.

• The nose pad height typically ranges from 9 to 15 mm. If your nose bridge is low, we recommend choosing a height ≥ 13 mm.
• The distance between the highest points of the nose pads typically ranges from 20 to 28 mm. If your nose bridge is low, we recommend choosing a distance ≤ 24 mm.

Of course, the bridge width can also serve as a reference. As a rule of thumb, if your nose bridge is low, a bridge width ≤ 18 mm is advisable.

Crucially, an unsuitable nose pad position will cause the glasses to constantly slip down to a very low position, creating excessive prismatic effect, leading to visual fatigue and serious harm to your eyes. Because these measurements are not marked on the frames, ask the seller to measure them for you while you are selecting frames. Only then can you pick the frame that is truly best for your eyes.