What are high index lenses?

In the world of eyewear, there is a continuous ongoing debate: contact lenses vs glasses. Both parties have their vocals fans, but at the end of the day, it usually comes down to personal preference. There are a few situations when a patient is unable to wear contact lenses due to medical conditions such as dry eyes syndrome, blepharitis or other such illnesses. In that case, glasses are the obvious alternative. Many factors are considered when choosing lenses for glasses. One important factor is the index of refraction of the lens.

When it comes to lenses, a “high index” lens has a higher refraction index. This translates into a better optical lens when compared to standard CR39 1.50 index lenses.  The benefits are most apparent for patients with stronger spectacle prescriptions. While their effect can be small for conditions below +/- 2, they begin to shine in moderate to severe refractive cases. High index lenses come with some additional benefits:

• They are thinner, about 20% thinner than normal index lenses, providing both comfort and more stylish look to the wearer. This feature is critical because they are usually used for higher prescriptions. Getting standard lenses for a -5.00 prescription, for example, will result in a significantly thick, bulky lens.

• They are lighter, due to the excellent materials they are made of. This again translates into improved comfort, making them much harder to slip or cause discomfort.

• They have excellent optical quality, greatly helping patients with several eyesight conditions. High index lenses often come with add-ons such as anti-reflective treatment (AR) for premium vision quality, which works for both + and – prescriptions.

There are several manufacturers that offer high index lenses for patients. One of them is Nikon.  Nikon provides excellent lenses for everything from photo cameras to glasses. They even provide 1.74 index lenses, the highest index currently available on the market. Bear in mind, the standard, plastic lens has an index of 1.50 and is considered a “low index” lens. High index lenses begin at 1.60.

The typical process for buying Nikon high index lenses has three steps:

1. Choosing the type of lens

single lens or progressive lens. The latter is typically for patients 40 years of age and older and are great in treating presbyopia – providing clear vision for both near and far objects.

2. Choosing the material for the lens.

Here you have the standard glass lens, as well as low index and high index plastic.

3. Choosing coatings.

The final step is choosing from the range of coatings that Nikon has to offer. Anti-Reflective coating helps reduce glare and is somewhat standard, but the manufacturer also offers several other coatings.

Of course, there are multiple manufacturers on the market who specialize in producing quality ophthalmic high index lens.  Other lens manufactures include Hoya, Zeiss and Essilor.  Before purchasing your next pair of glasses visit our clinic, 360 Eyecare in Toronto and ask to speak to one of our opticians or book an appointment with one of our optometrists for further information on what the best lens option is for your prescription.