The main differences between these two lenses are price, thickness, weight, color options, and general appearance. People purchasing 1.67 high index lenses generally either do not have an extremely high prescription or are shopping on a budget. 1.74 high index lenses, on the other hand, are the thinnest and lightest plastic lenses currently in existence.1.74 high index lenses are thinner and lighter than 1.67 high index lenses. 1.67 high index lenses are much less costly compared to 1.74. Though both reduce the eye distortion caused by strong prescriptions (making your eyes look bigger or smaller than they are), 1.74 high index lenses accomplish this better than 1.67 high index lenses do. 1.67 high index lenses are available in more colors: both come in clear, gray tinted, and brown tinted, but only 1.67 comes in Transitions brown or gray.1.74 high index lenses are better for those looking for the thinnest lens possible; generally, people with extremely high prescriptions choose this option.1.67 high index lenses are better for those looking to save money or those who do not have extremely high prescriptions.