In recent years, myopia has become increasingly prevalent, bringing significant inconveniences to daily life and work. Wearing corrective optical glasses remains the most common solution for myopia.
However, many people lack a clear understanding of how to choose eyeglasses based on their myopia degree such as what type of glasses, Optical frames, or lenses are suitable for -4.00D (400 degrees) myopia, and other related questions.
Optical frame Selection
People with high myopia have a wide range of options when choosing Optical frames and lenses. In terms of Optical frame styles: rimless, semi-rimless, and full-rim Optical frames are all viable. Generally, rimless Optical frames have degree limitations, they are not suitable for very high myopia and are recommended for those with myopia below -6.00D (600 degrees).
In terms of materials: both metal frame and acetate frame are applicable. Acetate frame typically offer rich color options, making them easy to match with different outfits. Metal frame especially pure titanium ones, boast excellent texture, they are lightweight and comfortable to wear without causing pressure on the nose or ears. Therefore, you can choose the Optical frame style, material, and color based on your face shape and personal preferences.
Lens Selection
High-quality lenses for high myopia should meet the following criteria:
Optical clarity with no color distortion;
Strong chemical resistance household solvents and chemicals will not damage the lenses;
Lower reflectivity than glass lenses, avoiding glare and eye discomfort;
Compatibility with multiple functional coatings, such as anti-radiation, scratch-resistant, oil-repellent, and anti-glare coatings.
A refractive index of 1.67 or lower is perfectly sufficient for most users. While it’s true that for the same prescription power, a higher refractive index results in thinner lenses—a key consideration for consumer aesthetics—there’s a critical trade-off to prioritize from the consumer’s perspective: sufficient is better than higher.
Why “sufficient is better than higher”?
For most people with high myopia, a refractive index of 1.67 is more than adequate. While it’s true that for the same degree, a higher refractive index results in thinner lenses (a key concern for high myopia patients seeking a more aesthetically pleasing look), there is a critical trade-off: the higher the refractive index, the lower the Abbe number. Below is a detailed analysis of the pros and cons to help you make an informed decision:
1. Higher Refractive Index (e.g., 1.74, 1.76)
Advantages:
Thinner and Lighter: The most significant advantage. For high myopia (e.g., above -8.00D), lenses with a refractive index of 1.74 will be noticeably thinner and lighter than 1.67 lenses, reducing the “bulky” appearance and relieving pressure on the nose.
Better Aesthetics: Thinner lenses fit more seamlessly into Optical frames, avoiding the “bottle cap” effect common with thick, low-refractive-index lenses for high myopia.
Disadvantages:
Lower Abbe Number: The Abbe number measures a material’s ability to disperse light. Higher refractive index materials (e.g., 1.74 polycarbonate or MR-174 resin) typically have an Abbe number around 30-32, while 1.67 lenses have an Abbe number of 32-36. A lower Abbe number means more chromatic aberration—when looking at objects (especially edges or bright light sources), you may notice slight color fringing (e.g., red or blue edges), which can cause eye fatigue during prolonged wear.
Higher Cost: The production process for high-refractive-index lenses is more complex, so they are significantly more expensive than 1.67 lenses (often 2-3 times the price).
Potentially Lower Impact Resistance: Some ultra-high refractive index materials (e.g., 1.76) are less tough than 1.67 or 1.60 lenses, making them more prone to chipping if dropped or impacted.
2. Moderate Refractive Index (1.67, Recommended for Most High Myopia Patients)
Advantages:
Balanced Optical Performance: With an Abbe number of 32-36, 1.67 lenses have minimal chromatic aberration, ensuring clear, natural vision without color distortion. This is crucial for reducing eye strain, especially for those who wear glasses all day (e.g., office workers, students).
Cost-Effective: Offering a good balance between thinness and price, 1.67 lenses are more affordable than higher-index options while still meeting the aesthetic needs of most high myopia patients (lenses are sufficiently thin for Optical frames of standard size).
Reliable Durability: Most 1.67 lenses are made of MR-7 or MR-8 resin, which have excellent impact resistance and scratch resistance (when paired with a quality coating), making them suitable for daily use.
Disadvantages:
Slightly Thicker Than Ultra-High Index Lenses: For extremely high myopia (e.g., above -10.00D) or those who prefer very slim Optical frames, 1.67 lenses may be slightly thicker than 1.74 lenses. However, this difference can be minimized by choosing Optical frames with smaller lens diameters or thicker rims to hide the edge thickness.
Conclusion
The core principle for selecting a lens refractive index is to prioritize optical clarity and comfort while balancing thinness and cost. For most high myopia patients (-3.00D to -6.00D):
A refractive index of 1.67 is optimal—it provides sufficient thinness, minimal chromatic aberration, and cost-effectiveness, making it suitable for long-term wear.
For those with extremely high myopia (above -6.00D) or who prioritize ultra-thin lenses (e.g., for aesthetic reasons), 1.74 lenses can be considered, but be aware of the potential for increased eye fatigue from lower Abbe numbers and the higher cost.
In summary, “sufficient is better than higher” there’s no need to pursue the highest refractive index blindly. Choose based on your myopia degree, wearing habits, and budget to achieve the best balance of vision quality, comfort, and aesthetics.
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