The lenses of prescription glasses bend light in such a way that it focuses clearly on the retina.
But as time goes on and visual anomalies become more common, prescription strengths are increasing with each generation.
Conventional glasses for high prescriptions are bulky and look unsightly to many people. And no one wants to compromise on the aesthetic of their glasses. That is where high index glasses become beneficial.
They offer the same power as your bulky lenses but are extremely thin and lightweight. Let us look at what are high index lenses and how they are different from usual lenses.
What is a High Index Lens?
A High Index Lens is one with a higher index than a normal one. What that means is that these lenses have a higher index of refraction or the ability to bend light and focus it on the retina (the innermost layer of the eye) than other glass or plastic lenses.
The actual index of refraction of these high index glasses is about 1.74 compared to 1.52 of crown glass lenses and 1.48 of plastic lenses.
The high index glasses are made of materials that are much denser than regular plastic or glass used in normal glasses. This helps them focus light more efficiently while saving up on space.
High Index Lenses vs Regular Lenses
Regular lenses tend to be heavier and bulkier than high index lenses for the same prescription strength.
They also have a lower refractive index than high index glasses so that they do not focus on light as efficiently.
Having said that regular glasses can cover a wonder range of prescription strengths. High Index Lenses are mostly reserved for people with high values of prescription strengths while regular lenses can cover slight vision defects too.
The price point for regular lenses is also lower than high index glasses. Also, high index glasses can be brittle and can scratch easily. That is why people like putting scratch-resistant coatings on them.
A small defect with high index lenses that may require you to spend another extra buck is that they are usually more reflective than ordinary glasses. That is why you may need to get an AR coating on them to prevent any glare. You may also need to get a blue light protective covering if you use screens as well. This may further increase the cost of your glasses.
Benefits of High Index Lenses
A major benefit of high index lenses is that they are particularly lightweight in comparison to other glasses. The materials used are dense and as you move up the refractive index you get some of the thinnest glasses you can find.
High Index Lenses also have much better aesthetics in comparison to regular glasses. While delivering higher prescription strengths, the lenses of regular glasses can get quite thick and that can hide your eyes and make them invisible.
In comparison, high index lenses are thin and make it easy for people to see your eyes and keep eye contact with you especially when you add an anti-reflective coating to them.
Who should get High Index Lenses?
The ideal high index lenses user should be someone with a high prescription strength and is someone who is at peace with paying a little extra for aesthetics and overall comfort.
What that also means is that if you have low prescription strength, for example, a -1 for nearsightedness you do not need high index glasses and can get decent enough regular glasses to help with your refractive error.
High Index Lenses are lenses with a high refractive index that focus light rays more efficiently than regular glass or plastic lenses.
They are much more comfortable than regular lenses and carry much greater aesthetic appeal. Having said that, they may be heftily priced and are more reflective than regular glasses. What all this means is you should give it decent thought before buying high index lenses.
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