PROGRESSIVE LENS Explanation, technology and advantages

What are progressive lens?

Progressive lens are advanced multifocal eyeglass lens that offer a seamless progression of multiple lens powers in a single lens. Unlike bifocal or trifocal lenses, they do not have visible lines separating the different fields of vision. These lenses allow for clear vision at all distances — near, intermediate and far — with smooth transition between them.

Technology behind progressive lens

1. Gradient power distribution: Progressive lens are digitally surfaced using freeform technology that precisely controls the surface curvature. The power of the lens gradually changes from the top (for distance vision) to the bottom (for near vision), with a middle section for intermediate viewing.

2. Wavefront technology: Some progressive lens use wavefront-guided technology to minimise optical aberrations and improve visual clarity.

3. Digital/freeform surfacing: Computer-controlled surfacing equipment sculpts the lens with micron-level accuracy, based on individual eye measurements and frame shape.

4. Customised lens mapping: Progressive lens can be customised according to the wearer’s prescription, pupillary distance, lifestyle needs (e.g., computer use), and even head movement patterns.

How are they more helpful than normal (single vision) lens?

1. Multiple vision zones: Normal lens correct only one field of vision (e.g., distance or reading), while progressive lenses combine all three (distance, intermediate, near) in a single lens.
2. Seamless visual transition: No abrupt image jumps like in bifocals or trifocals; transition between focal points is gradual and natural.

3. Aesthetically superior: No visible segment lines, making them look like regular lenses — more fashionable and modern.
4. Convenient and cost-effective: Eliminates the need to carry multiple pairs of glasses for different tasks like reading, driving, and computer work.

5. Personalised vision experience: Advanced designs offer customisation based on user habits and visual requirements, enhancing comfort and clarity.

Limitations

• Initial adaptation period required for new users
• May cause peripheral distortions if not properly fitted
• More expensive compared to regular lens

Analytical/examination-based questions

1. Short answer

• What are progressive lenses and how do they differ from bifocal lens?
• What is meant by gradient power distribution in progressive lens?

2. Long answer

• Explain the technology behind progressive lenses and discuss their advantages over single-vision lens.
• Compare and contrast the design and functionality of progressive lenses with bifocal and trifocal lens.

3. Analytical/applied

• A 50-year-old office worker is experiencing difficulty in reading up close and viewing distant objects clearly. Justify the suitability of progressive lenses for such a user.
• Discuss how advancements in lens manufacturing technology have improved the effectiveness of progressive lenses.