Complete Guide to Eyeglass Lens Parameters & Prescription Values

How to Choose the Right Lenses for Clear, Comfortable Vision

Most people focus only on frame design when purchasing glasses. However, the quality of your vision and long-term wearing comfort depends entirely on two sets of professional optical data: lens material parameters and prescription eye-test parameters. Every value directly affects clarity, comfort, and eye health.

Part 1: Three Core Parameters of Eyeglass Lens Materials

All Prescription Lenses are defined by three key properties: refractive index, Abbe number, and optical coatings.

1. Refractive Index (Determines Lens Thickness & Weight)

The refractive index refers to the light-bending ability of a lens material. The most common indexes in the optical industry are 1.56, 1.61, 1.67, 1.71, and 1.74.

Key rules:

• The higher the refractive index, thethinner and lighter the finished lens.
• The refractive index only affects thickness and weight — it does NOT improve visual clarity.
• For myopia below 400 degrees, choosing a lower index provides better optical performance and higher cost performance.

High-index materials are only necessary for high myopia to reduce lens bulk and weight.

2. Abbe Number (Determines Visual Clarity & Purity)

The Abbe number is the core standard for judging lens imaging quality. It represents the degree of chromatic aberration.

General industry rule: The higher the refractive index, the lower the Abbe number (generally true but not absolute).

Key meaning:

• Higher Abbe number = less chromatic aberration, clearer and more natural vision.
• High-index thin lenses sacrifice partial visual definition. Blindly pursuing ultra-thin lenses will cause weaker imaging quality and easier eye fatigue.

3. Multi-Layer Optical Coatings

Lens coating technology determines the surface performance of finished glasses. Qualified optical lenses are coated with multiple functional layers to achieve anti-reflection, scratch resistance, water resistance, oil resistance, UV protection, and blue light filtering.

Multi-coating greatly improves light transmittance, makes vision brighter, and extends lens service life.

Part 2: Five Essential Prescription Parameters for Accurate Glasses

A precise prescription includes five indispensable data: myopia degree, astigmatism, axis, pupillary distance, and pupillary height. Each parameter cannot be ignored.

1. Myopia Degree (SPH / Sphere)

Myopia causes blurred distance vision. During professional optometry, doctors will first confirm the accurate myopia degree as the basic vision correction value.

2. Astigmatism (CYL / Cylinder)

Astigmatism is different from myopia. Myopia produces blurry vision, while astigmatism produces double vision, ghosting, and dragging shadows. Astigmatism is also called cylinder power and must be matched with an axis value.

3. Axis (AX)

The axis ranges from 0° to 180°. It is the directional angle for astigmatism correction. Astigmatism and axis are an inseparable pair of parameters.

Inaccurate axis position will lead to dizziness, eye soreness, distorted vision, and inability to wear glasses for a long time.

4. Pupillary Distance (PD)

Pupillary distance is the straight-line distance between the centers of the two pupils. It ensures the optical center of the lens accurately aligns with the human eye’s viewing position.

Wrong PD will cause persistent visual fatigue and affect vision correction effect.

5. Pupillary Height (PH)

Pupillary height is the final measured optometry data. It is particularly critical for large-frame glasses and progressive multifocal lenses.

Accurate pupillary height ensures the eye looks at the correct optical area of the lens, which is the key to stable and comfortable wearing.

Part 3: Quick Lens Selection Summary

• Higher Abbe number = clearer, purer vision
• Higher refractive index = thinner, lighter lenses
• Low myopia does not need high-index lenses
• Myopia, astigmatism, axis, PD, and PH must all be accurate for perfect glasses

Choosing the right lens parameters and precise prescription data allows you to obtain comfortable, high-definition, and eye-friendly eyewear.