1.67:
Advantages: Very thin lenses, exceptional optical accuracy.
Disadvantages: Potential cost increase, brittleness.
Suitable Prescription Strengths: Very high.
Abbe Value: Approximately 32-34.
Summary: Lenses with a refractive index of 1.67 offer exceptional thinness and optical accuracy, making them ideal for individuals with very high prescription strengths. However, they could be more costly and require careful handling due to brittleness.