Glasses Fitting Guide Part 1: Basic Knowledge

Introduction

A few days ago, I noticed a user on a certain website purchasing a pair of glasses online. Looking closely at the comments, I found many people didn’t understand the process of fitting glasses. Considering the increasing number of people wearing glasses today and my own long-term experience with myopia and high diopter lenses, I have accumulated some knowledge in this area and have become something of an ‘expert patient’. Thus, I’ve decided to write a series of informative posts about glasses fitting.

Foreword

This article will primarily discuss the relevant knowledge of fitting glasses. The main purpose is to introduce the basic knowledge of glasses fitting and to discuss some key points that I believe are important in the process. The primary sources of knowledge in this article come from the internet, including but not limited to various official manuals, official websites, and encyclopedias. The knowledge related to glasses fitting in this article cannot guarantee complete accuracy, but most views in this article are applicable to the majority of people who may read it.

This article is applicable to the majority of the glasses-wearing population, namely those aged 16-45 years old who possess the following characteristics:

both eyes are myopic, the difference in the diopter of myopia between both eyes is not large (e.g., R: -5.00, L: -6.00), both eyes can have astigmatism but the diopter is not high and the difference is not large, both eyes are not aged, and there are no other ocular diseases in addition to myopia.

Basic Knowledge of Glasses Fitting

Glasses fitting is mainly divided into two parts: the first part is optometry, and the second part is fitting glasses based on the optometry results.

Optometry

I want to emphasize my basic understanding of optometry:

Optometry is a medical act, not a commercial one, so please be responsible for yourself!

If you know that you are myopic, then you should definitely know what diopter of glasses you need to wear. The purpose of optometry is to find the parameters for your glasses, these parameters mainly include the following: the diopter of myopia in both eyes, the diopter of astigmatism and axis in both eyes (if there is astigmatism), and the pupil distance of both eyes. There are a total of 8 pieces of data (the number may vary depending on personal circumstances).

If you don’t have accurate optometry data, it doesn’t matter how good the glasses you fit are, because they are not suitable for you! Please ensure that glasses are only fitted when the optometry results are reliable.

In order to obtain accurate optometry parameters, accurate instruments and experienced optometrists are necessary. I believe that the optometrist plays a crucial role in the optometry process, as optometry is adjusted by people, and various parameters need to be confirmed through interaction and feedback between the person being fitted for glasses and the optometrist. Therefore, it’s also essential for the person being fitted for glasses to communicate sincerely with the optometrist. So how can we obtain accurate optometry parameters?

There are many types of optometry instruments, from the simplest Optometry equipment with a single device to the more complex comprehensive optometry instruments. At present, the instruments in regular glasses stores and regular ophthalmology hospitals are roughly the same. As long as you go to a regular place, you generally don’t need to consider the difference in optometry instruments during the optometry process.

The difference in optometry is reflected in the optometrist. The experience of the optometrist is particularly important, and of course, there are different levels of optometrists. The higher-level certificate requires a longer period of practice, so generally speaking, higher-level optometrists have more experience. In large glasses stores, there are usually one or two experienced optometrists, as long as you find the right optometrist, you won’t have any major problems with your optometry.

I recommend getting your eyes tested at the following places:

1. Large chain glasses stores
2. Ophthalmology hospitals
3. Large optometry and glasses fitting centers.

As for which type of optometry location is better, I believe it still depends on the optometrist.

Of course, how to judge whether an optometrist is reliable depends on your own communication skills and judgment.

Through optometry, we can obtain the 8 data points previously mentioned. Once we have these 8 pieces of data, we can proceed with glasses fitting.

Glasses Fitting

Before fitting glasses, we need to understand the basic components of glasses. Glasses are assembled from two parts, one is the lens, and the other is the frame. Of the two, the lens directly determines the visual experience you can get from these glasses, while the frame is just an auxiliary device to fix the lens in a scientific position. In my opinion, you need to first confirm the appropriate lens specifications, and then choose the frame you need based on the lens. Meanwhile, since I don’t know much about the latest development of frames, some of my knowledge may not be comprehensive enough, please understand.

I suggest that you must choose the lens you can afford based on your optometry data first, and then choose the frame you like based on the lens. If you think the decorative effect of glasses (fashion role) is more important, you can also consider the frame first, and then the lens (after all, many people only fit plano glasses just for good looks).

We will divide the following into 8 parts, the first four parts talk about the knowledge of lenses, and the last four parts talk about the knowledge of frames. At the same time, I will give my recommended lens (frame) selection process.

Lenses

Types of Lenses

First, let’s refer to the lens classification on the JINS official website (screenshot below). Then you find that there are more than 10 types of lenses!

So let’s take a look at the lenses here, how many types do we need to consider? In fact, only the following few:

• Ordinary single vision lens (the first one in the picture);
• Blue light blocking lens (the second one in the picture);
• Photochromic lens (the fourth one in the picture);
• Progressive multifocal lens (the sixth one in the picture), should we consider it? For the vast majority of myopic people aged 16-45, I think unless you have too much money, there is no need to consider.

So what’s the difference between the above 3 types of lenses (except for the progressive multifocal lens)?

• Single vision lenses are very ordinary glasses lenses that let you see distant objects clearly;
• Blue Light Blocking lenses add a function to the single vision lenses, which is to reduce harmful blue light entering the eyes through the lenses (blue light is generally believed to be bad for eye health);
• Photochromic lenses add another function to the single vision lenses, which is when there is sunlight or the temperature rises (the specific conditions for the glasses to change color are different, here is a common example), the glasses will automatically turn into sunglasses with diopter (or a specific color).

The latter two types of lenses mentioned above are “functional lenses“. If your money is not particularly much or you don’t have special needs, then you can ignore them, we will only discuss the most widely used single vision lenses next.

For Blue light blocking lenses, many people are interested, but this needs to be analyzed according to specific situations. I will share my personal opinion: if you look at electronic screens a lot (use computers and mobile phones for more than 8 hours a day), and you are also willing to spend a little more money, then you can consider. But in fact, the effect of blue light blocking lenses in this situation is limited, it is not as good as reducing your screen time by half an hour a day.

Optical Parameters of Lenses

Currently, most of the lenses we use are resin lenses, most people will consider aspheric lenses, and there are better double-sided aspheric lenses (this is generally only needed to consider on high refractive index lenses, unless money is not a concern). Our following discussions are all based on resin aspheric lenses.

1. Refractive Index. The refractive index generally has five types: 1.56, 1.60, 1.67, 1.70 (1.71), 1.74 (1.76, 1.78). For most people, I recommend that you only need to consider these four refractive indices of 1.56, 1.60, 1.67, 1.74. Generally, 1.67 is referred to as a high refractive index, and 1.74 is referred to as an ultra-high refractive index. For the high-diopter population (myopia diopter exceeds 8 diopters, all use this standard), generally only 1.67 or 1.74 can be used. For the low-diopter population, it depends on your wallet and your personal requirements.
2. Thickness. As the refractive index increases, the thickness of the lens with the same diopter decreases. Under the same refractive index, the higher the diopter, the thicker the lens.
3. Abbe number. The Abbe number is an indicator to measure the dispersion of the material. For glasses, it can be understood that the higher the Abbe number, the better the lens. Generally speaking, as the refractive index increases, the Abbe number of the lens decreases. But there are exceptions. The Abbe numbers of most 1.67 and 1.74 are all 32. The Abbe number of Tokai’s 1.70 (38) is higher than the same brand’s 1.67 and 1.74 of 32. For specific details, you can refer to the table of Essilor single vision lenses below, which has the Abbe numbers corresponding to each refractive index lens.

Lens Brands and Prices

Because my diopter is relatively high, I usually only consider the following four international brands: Zeiss, Essilor, HOYA, and TOKAI.

Among the four international brands, Zeiss has the top-notch optical level (high-demand lenses in optical laboratories are basically Zeiss, occasionally there will be Olympus, but Olympus optical lenses are relatively rare, so they are not discussed, this is just a side proof of the high level of Zeiss), followed by Essilor, HOYA and TOKAI are Japanese brands, these two are basically the same, most people don’t need to worry about some very subtle differences in quality, so they are not discussed.

About the prices of the four brands, generally speaking, the price order of the same refractive index and the same positioning lens (whether the lens needs to be customized) is as follows: Zeiss > Essilor > HOYA ≈ TOKAI

Of course, the price of 1.67 is far more than 1.60, and the price of 1.74 is even twice that of 1.67.

At the same time, please also note that Zeiss’s low-end lenses (for example, the most common lotus film) definitely can’t match the low-end level lenses of the last three brands (for example, Essilor’s A3 or HOYA’s VG), and it’s not to say that Zeiss’s lenses are definitely better than TOKAI. Specific products, specific analysis is still required.

How to Choose the Right Lenses for Yourself

When you see such a table, are you a bit confused? What should I look at first, and then what?

Here are my suggestions (taking Essilor as an example in the table above).

1. First look at your diopter, if the diopter is low, there is no need to consider 1.67 and 1.74, because the high refractive index is expensive and the Abbe number is also low. If the diopter is high, you can only choose 1.67 and 1.74. If you are wealthy, choose 1.74, if not, then 1.67. People with high diopters of vision are relatively less entangled. After all, they are all customized lenses, so just find the highest price you can afford.
2. Once you determine the refractive index range of the lens, you need to consider the balance between “price-optical performance-thickness“. Everyone has different emphasis on these three points. Some students who don’t have much money can only prioritize price and choose 1.56. Some people only value optical performance, then go directly with 1.60.

Some people are willing to sacrifice the optical performance of the lens for ultra-thinness, that can also be low diopter with 1.67 or 1.74. It’s just a matter of personal preference.

When you have read these, I believe you have a certain understanding of lenses and have a preliminary understanding of how to choose lenses. The suggestions given above can be applied to all brands of lenses. The key is to analyze specific situations.

Frames

Types of Frames

The types of frames are actually not many. I generally classify them into full frames, half frames, and rimless. Here is a simple introduction.

• Full frame: This type of frame completely surrounds the lens, providing a good fixed effect, but it may also break under strong external force.
• Half frame: This type of frame is based on the full frame, and the lower half of the frame is removed and replaced with a nylon cord for fixing. In this case, a balance can be achieved between the fixing effect and the deformation under strong external force.
• Rimless: This type of frame is the most radical way to fix the lens. Each lens is only fixed on both sides. Because the lens fixing method is relatively thin, this fixing effect is the worst. (This is also why rimless glasses are more recommended to use PC lenses, because PC lenses are more impact resistant, have better hardness, but the optical parameters are not so good.)

Frame Materials

Basically, any material that can be made into a strip can be made into a frame. To my understanding, metal, plastic, resin, etc. are all common frame materials. The mechanical properties of the frame are related to the properties of the frame material itself and the processing method of the material. This part is too complicated, so we won’t go into details.

Generally speaking, among metal frames, pure titanium frames have a higher overall quality (and also a higher price), followed by titanium alloys, ordinary aluminum alloys are also okay, stainless steel seems to be not common. There are many types of plastics, which won’t be elaborated on. As far as I know, TR-90 is a pretty good material. If you want to learn more about frames, click here to see my other articles.

Frame Brands

Compared to lenses, because the industry entry standard for frames has been significantly lowered (even small family workshops can do it), there are too many frame brands in the world! The frame market is also complex! I won’t say much here, if there are industry insiders, they can introduce it in detail.

I must emphasize that those who wear glasses should not pay too much attention to whether the frame brand is an international or domestic brand. At present, the vast majority of frames in the world are made in China, nothing more than different places of origin, different foundries.

Of course, if you have money, you can directly consider some big brands (for example, Charmant, Silhouette), these big brands are expensive, but what you get in return is that the design, quality, quality control, and after-sales of the products are all guaranteed.

Click here to see the introduction of the brand of frames.

How to Choose a Frame Suitable for Yourself

Actually, there is not as much professional knowledge about frames as lenses, and it is relatively easier to understand, so I will directly talk about my personal suggestions.

As mentioned earlier, “I suggest that you must choose the lens you can afford according to your optometry data first, and then choose the frame you like according to the lens. If you think the decorative effect of glasses (fashion function) is more important, you can also consider the frame first, and then the lens.” So here I assume you have already chosen the lens, so let’s start choosing the frame. (Actually, it’s fine to choose the frame first, just reverse your thinking)

Let me first declare the most important point in choosing a frame: as long as you are patient to choose, you can definitely find a frame that best suits your aesthetics and is suitable for you. Others’ aesthetics of frames are not your aesthetics of frames, so don’t rely too much on others!

Let’s first discuss based on the above frame categories. In fact, choosing a frame needs to consider the following points:

1. diopter of myopia
2. Lens thickness
3. Personal face shape (Click here to learn to match your face shape)
4. Size of the frame
5. The most important thing—your aesthetics. (Click here to learn to choosing the Perfect Eyeglass Frames)

Each of us chooses a frame, which is a balance adjustment among the above 5 points. Different people value different things, so it is impossible to give detailed suggestions. The following are my views.

• If you have a high diopter of myopia, you are basically not suitable for rimless frames, because even if the lens of high diopter is 1.74, it is not thin. With rimless frames, the edge will be relatively thick, even if it is thinned, it is relatively ugly, so I still recommend full frame or half frame. In my case, although my diopter is high, using 1.74 is not very thin, but I only like pure titanium half frames, so I choose half frame;
• If your diopter is not high, then the range of frames you can choose is very large. I suggest you first understand the available frames according to the money in your pocket, and then according to your own aesthetics, just choose the one that looks most pleasing to the eye.

The frame selection process mentioned above needs to satisfy one premise: the design and production of the frame both conform to the scientific nature of human optical fitting. If a frame is expensive, but does not conform to the original intention of fitting glasses (for the health of glasses), it is also a substandard frame.

Conclusion

This is the first article in the eyeglasses selection guide. After you have carefully read this article and understood the key points in it, I believe you can successfully fit a pair of glasses that meet your requirements.

Regarding the two most common channels for glasses fitting, brick-and-mortar stores and online stores, I will conduct a series of analyses in the next article, click here to read more. I will also combine this with my personal glasses fitting experience to discuss the optometry and glasses fitting experiences in these two different channels.