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A high-index 1.74 lens is a spectacle lens material with a refractive index of 1.74. This is the thinnest and lightest plastic lens material commercially available. It is reserved for wearers with the highest prescriptions.
read more about high index 174 eyeglass lens ...The main benefit is maximum thinness. Lenses made in the 1.74 index are up to 50 percent thinner than standard plastic lenses. This drastically reduces the size and weight of extremely thick prescription lenses, offering the best cosmetic outcome.
The 1.74 index is required for people with prescriptions of -8.00 diopters and higher. For these very strong corrections, the material is needed to reduce the extreme edge thickness that would be unwearable or uncomfortable in any other lens material.
The trade-off for maximum thinness is a slightly higher cost. Also, higher index lenses can sometimes have more peripheral distortion, so they must be paired with anti-reflective coatings and carefully fitted into a smaller frame.
Fitting 1.74 lenses requires careful frame selection. To maximize thinness, opticians often recommend smaller, rounder frames to minimize the thickest points of the lens edge. Precise pupil distance and fitting height measurements are also critical for optical performance.
Yes, 1.74 is the highest index plastic material available, making it the thinnest and lightest option.
Yes, 1.74 lenses are the most expensive plastic lenses due to the cost of the specialized material and manufacturing process.
No, but they are often fitted into small frames to further reduce the thickness of the exposed lens edge.
For prescriptions over +/- 6.00, 1.74 lenses provide the best cosmetic result. However, they must be fitted by a professional to ensure optical centers are exact; even a small error in these high-power lenses can cause significant double vision.
Optical Journal. Evolution of Ultra-High Index Lenses (opticaljournal.com). 2024.
ABDO. Spectacle Lens Design (abdo.org.uk). 2024.
College of Optometrists. Verifying Lens Accuracy (college-optometrists.org). 2024.
The Vision Council. Lens Surfacing and Finishing (thevisioncouncil.org). 2023.