3.5 Eyes · ThinkerQAQ

This is a historical learning note and may contain outdated or incomplete understanding.

2. Optometry

2.1. Myopia

The axial length of the eye becomes longer, causing light refracted through the lens to focus at a point that does not correctly fall on the retina, resulting in blurred vision.

2.2. Astigmatism

The curvature of the cornea is inconsistent, causing radial blur after light passes through the cornea. In simple terms, some directions have a greater degree of myopia. 25 degrees of astigmatism is approximately equivalent to 50 degrees of myopia.

3. Eye Examination

Nearly 30 Years of Wearing Glasses: My Method and Basic Experience With Eyeglass Fitting - SSPAI

3.1. Before the Examination

3.1.1. Rest

Do not overuse your eyes.
Get adequate rest.

3.1.2. Choosing an Institution

Paid optometry at a large offline chain > private ophthalmology hospital > public ophthalmology hospital > free offline optometry.

3.1.3. Examination Time

Weekday morning, 10–11 a.m.

3.2. During the Examination

Don’t Ruin Online Eyeglass Ordering at the Optometry Step — Learn the Basics of Refraction - Bilibili

Autorefraction

Existing-prescription measurement
Subjective refraction

    1. Fogging

    2. Fine-tuning myopia
    3. Red-green test for myopia
    4. Fine-tuning astigmatism
    5. Red-green test for astigmatism

4. Dominant eye 5. Trial wear 1. Look at distant objects 2. Look at near objects

3.3. After the Examination

3.3.1. Prescription

Sphere is the degree of myopia, cylinder is the degree of astigmatism, axis is the axis angle of astigmatism, and PD is the distance between the pupils of the two eyes. Pupil height is not always included, but it may be needed if you wear large-frame glasses.

4. Choosing Glasses Online

Save This: How to Scientifically Fit a Good Pair of Glasses? After 20 Years of Myopia, I Realized I Had Never Worn Good Glasses - Bilibili Is This the Frame You Chose Yourself? What About Comfort? How to Choose a Good Frame - Bilibili

4.1. When Online Eyeglass Ordering Is Suitable

Stable prescription
Single-vision glasses

4.2. Choosing a Frame

Consider comfort first, then appearance.
Parameters: for example, a marking such as 54□18-140 on the inside of the temple means a maximum lens width of 54 mm, bridge width of 18 mm, and temple length of 140 mm.
Materials: pure titanium, β-titanium, and TR90.

For high myopia, the lens edge is thick; for horizontal astigmatism, avoid frames that are too wide.
The eyewire size should align with the width of the cheekbones.
Wraparound temples.

4.3. Choosing Lenses

Lens material is generally resin MR-174.

4.3.1. Choosing a Brand

4.3.1.1. How to Divide Product Tiers

Thickness

1. Double aspheric < internal aspheric < external aspheric

    1. [Are Double-Aspheric Lenses Really Better for High Myopia and High Astigmatism? Don't Be Misled - Bilibili](https://www.bilibili.com/video/BV1GF4m1K7y9/?vd_source=79c9f80f56384444d88bfb3e4cf579df)
2. The smaller the decentration, the thinner the lens. For example: ((52 + 17) - 64) / 2 = 2.5.

Brand choice

2. First-tier recommendations: Nikon and ZEISS.

    1. Nikon: HCC, ECC, SEE.
    2. ZEISS: A Series, ClearView, SmartLife, **SmartLife Individual**.
        1. ClearView: stock lenses. Center power increases by 25–50; pupil height is set 3–5 mm below the actual height. There are two coating options, Green Diamond and DuraVision, which replace the A Series and previous ClearView series respectively.
        1. **SmartLife Single Vision**, SmartLife Asian Fit, SmartLife Individual.
1. Essilor.
2. Selection:
    1. If appearance is not important and the priority is visual experience, choose ZEISS.
    2. If you do not want to deal with many details, choose Essilor for prescriptions below 1000 degrees.
    3. If thinness is the priority, choose Nikon.

4.3.2. Choosing a Coating

4.3.3. Choosing Refractive Index / Abbe Number

4.3.4. Custom vs. Stock Lenses

When Do Lenses Need to Be Custom-Made? Are Custom Lenses Always Better Than Stock Lenses? How to Read a Lens Power-Range Chart - Bilibili

Prescription
- Above a certain prescription, custom lenses are required.
Function
- Double-aspheric and similar designs are recommended as custom lenses.

4.4. Precise Fitting

Opticians who explain fitting knowledge on major platforms through self-media.

5. Bilibili

6. Lenses

Refractive index 1.74 and double-aspheric design. A Small Guide to Glasses for People With High Myopia - Zhihu

SmartLife: digital-type lenses. Digital Lenses Who Are ZEISS Digital Lenses Suitable For, and for What Ages? - Zhihu

2018: Where in Guangzhou Is a Good Place to Get Glasses? Mine Broke While Playing Basketball - V2EX

6.1. ZEISS Series

The Seven ZEISS Lens Series Most Commonly Bought by Ordinary Consumers: How to Choose and Compare Them ZEISS SmartLife Single Vision: Is It Thinner Than Ordinary Lenses? - Zhihu Should You Choose the SmartLife Asian Version? How Is It Different From the Standard Version? - Zhihu Who Are ZEISS Digital Lenses Suitable For, and for What Ages? - Zhihu Successfully Ordering ZEISS SmartLife Digital Asian-Version Lenses Online - Sina Testing

Collection: Why I Don’t Recommend ZEISS ClearView Rodenstock’s Lens Has No 1.74 Refractive Index — What Should High-Prescription Users Do? - Bilibili

6.2. Tokai

The Thinnest Resin Lens at 1.76: Comparing Different Brands’ 1.74 and 1.76 Lenses Which Is Thinner: ZEISS 1.74 or Tokai 1.70 Double-Aspheric? - Zhihu

Do ZEISS ClearView Lenses Really Completely Outperform the Previous ClearView Series? - Zhihu What Are Ordinary Single-Vision Lenses, Multifocal Lenses, and Functional Lenses? - Zhihu What Is the Difference Between Single-Aspheric and Double-Aspheric Lenses? - Zhihu Unboxing ZEISS ClearView Lenses - Zhihu Eyeglass Buying Guide Part 11: Lens Edition — Reconstructing the Visual World With Optical Art and Science Tokai Factory’s 1.76 Production Line Is Gone — What Can Replace 1.76 Lenses? - Zhihu Which Is Better, Tokai or Carl ZEISS Lenses? - Zhihu For High Myopia and Blue-Light Filtering, Tokai 1.76 or ZEISS 1.74? - Zhihu Case Study: Frames Suitable for Ultra-High Myopia - Zhihu How Can People With High Myopia Avoid Ugly Thick Lenses? - Zhihu How Should People With High Myopia Choose Lenses and Frames to Reduce Visible Edge Thickness? - Zhihu What Good-Looking Frames Are Suitable for High Myopia? - Zhihu

7. Contact Lenses

How Your First Pair of Contact Lenses Should Be Fitted - Zhihu How Should Contact Lenses Be Chosen If You Have Astigmatism? Five Situations Where You Should Avoid Them - Zhihu

8. Frames

Take front and side photos.

Myopia Eyeglass Buying Guide Part 1: Frames - Zhihu

Materials: Pure titanium Titanium alloy / pure titanium Z-titanium Memory alloy TR-90

Choose lightweight frames, such as non-metallic ones. Nose pads: fixed nose pads. Frame: full-rim, small frame, thick frame (wide rim), thick temples. Temple tips: metal frames usually have plastic or silicone sleeves at the ends of the temples to increase the contact area between the temples and the head. Acetate, TR-90, or plastic frames already have relatively thick temples, so extra sleeves are not needed.

With a fixed PD, the smaller the value of lens width + 1/2 bridge width, the thinner the lens edge. Frame shape also matters: with the same value, a squarer frame has thicker edges. When comfortable, it is ideal for frame lens width + bridge width to equal the PD. If that is not possible, make it as close as possible. When lens width + bridge width is the same, smaller lenses are thinner. The key point is comfort.

Is Pure Titanium or β-Titanium Better for Frames, and Which Is More Expensive? - Zhihu For 1000-Degree Myopia, Should Ultra-Thin Glasses Use Pure-Titanium or Acetate Frames? - Zhihu What Eyeglass-Frame Brands Under RMB 500 Are Good? - Zhihu 2023 Frame Recommendations: How to Choose Frames and Which Brands Are Worth Considering With 1000-Degree Myopia, Can You Get the Thinnest Possible Lenses? - Zhihu How Should People With High Myopia Choose Lenses and Frames to Reduce Visible Edge Thickness? - Zhihu With the Same Decentration, Which Frame Produces Thinner Lenses? A Summary - Zhihu Eyeglass Science: How to Avoid Making Your Eyes Look Smaller Behind Glasses — Important Frame-Selection Factors - Bilibili Men’s Wet-Hair Hairstyle Tutorial - Bilibili

8.1. Lindberg

Why Are Lindberg Glasses So Expensive Yet So Popular? - Zhihu

9. Ordering Glasses Online

10. Eye Examination

Visual acuity examination.
Slit-lamp examination: dry eye.
Intraocular pressure and visual-field examination.
Fundus examination: SLO.
Eye CT examination: OCT.
Ocular A/B ultrasound: understand axial length, vitreous and retinal condition, and whether posterior scleral staphyloma is present.

Everyone Should Have a Fundus Examination Once in Their Life — How Much Does It Cost for High Myopia? Is Dilation Necessary? - Bilibili What Eye Examinations Should People With High Myopia Have? - Zhihu Fundus Examination 1 - Bilibili My Frightening Fundus Examination Experience - Zhihu Expert Consensus on High-Myopia Prevention and Control (2023) — Is High Myopia No Longer Defined as 600 Degrees? - Bilibili Study of Macular Retinal Thickness in Myopic Eyes - Chinese Journal of Experimental Ophthalmology Formula for Choosing Eyeglass Frames - Bilibili

11. National Eye-Care Strategy

11.1. Mechanism of Myopia

Choroidal blood-flow regulation: two optical signals, low light and hyperopic defocus, trigger a chain reaction through dopamine and other signaling mechanisms in the retina, reducing choroidal thickness and blood flow. This then affects nutrition of the sclera, making the sclera thinner and less strong. Under intraocular pressure, the axial length becomes progressively longer, resulting in myopia.

11.2. How to Prevent and Control Myopia

11.2.1. Pay Attention to “Light Nutrition”

“Light nutrition” has two parts:

Light intensity
Spectral continuity

11.2.1.1. Outdoor Activity

Light intensity: on a bright sunny day it can reach 100,000–200,000 lux.
Spectral continuity: the content of different wavelengths is relatively balanced.

Use:

Extensive outdoor time: 4–6 hours of outdoor activity per day.
Basic outdoor time: 2 hours of outdoor activity per day.

11.2.1.2. Improve Indoor Lighting

Light intensity and color temperature:
1. Ceiling light: 7 W/m².
2. Desk illumination: 900–1500 lux; color temperature around 4000 K, or 5000 K in daytime and no more than 4000 K at night.
Spectral continuity: full spectrum, Ra > 90, R9 > 90.

11.2.1.3. Red-Light Treatment

Extract deep red light and use a laser to expose children’s eyes briefly, supplementing “light nutrition”; this is low-level red-light therapy.

Use low-level red laser light at 630–670 nm twice per day for three minutes each time to illuminate the fundus. This can activate mitochondrial function in fundus cells and prevent choroidal thinning.

11.2.2. Improve the Position of Focus

Where light focuses is a very important signal for the eye. If light is focused correctly on the photosensitive layer at the back of the eye — the retina — the eye can clearly identify objects. If the image is focused behind the retina, the eye attempts to follow that point, the axial length becomes longer, and hyperopic defocus occurs. This generally happens when looking at near objects. Conversely, the axial length becomes shorter and myopic defocus occurs, which generally happens when looking at distant objects.

One goal is to reduce hyperopic defocus when looking near; another is to create more myopic defocus during near work.

11.2.2.1. Reduce Hyperopic Defocus

11.2.2.1.1. Control Viewing Distance and Time

One fist, one chi, one cun.

11.2.2.1.2. Improve Accommodation

When looking near, positive accommodation is needed: the crystalline lens becomes more convex and pulls the focal point toward the retina, reducing hyperopic defocus. When looking far, negative accommodation is needed: the crystalline lens becomes flatter and shifts the focal point in the opposite direction, reducing myopic defocus.

Training mainly targets negative accommodation, for example with manual flippers or VR training devices.

11.2.2.1.3. Low-Power Convex Lenses

Also called reading/writing lenses. If positive accommodation is insufficient during near work, a convex lens can be added.

11.2.2.2. Create Myopic Defocus

11.2.2.2.1. Fogging Training

Wear fogging lenses with an appropriate power and gaze into the distance. This is the most basic form of fogging treatment. It can relax the crystalline lens and thicken the choroid.

11.2.2.2.2. Peripheral Myopic Defocus

After myopia reaches at least 100 degrees, lenses such as overnight orthokeratology lenses (Ortho-K), daytime RGP lenses, or defocus soft lenses are recommended.

11.2.2.2.3. Distant-Image Devices

Eyeglass-based methods create myopic defocus by changing the optical path of the eye. Distant-image devices instead optically process the object being viewed and use a virtual image to move a near visual target farther away.

Freeform-surface technology can be divided into coaxial and off-axis freeform surfaces. The former has no deformation, provides better image quality, and is less likely to cause visual fatigue.