Categories Eyewear, Lenses, Vision Care
anti-reflective lens coatings eyeglasses on table - 360 eyecare blog

Anti-Reflective Coatings

If you have a pair of glasses, or if you know someone who wears glasses, then you may have noticed the lenses reflecting light with a bit of colour in it, sometimes blue or green. Or maybe you’ve looked at an older pair of glasses that appears to reflect light at a much stronger rate with no colour visible. Perhaps you’ve heard others asking if their new glasses have the “anti-glare coating”. But what is this coating, and why is it considered a standard part of modern lenses?

What is an Anti-Reflective Coating?

anti-reflective lens coatings eyeglasses on table - 360 eyecare blog

An anti-reflective coating, sometimes referred to as an AR coating, or anti-glare coating, is a coating that is applied during the manufacturing of ophthalmic lenses. Originally developed for camera lenses to improve clarity and resolution in film, lens manufacturers brought the technology over to help improve optical clarity for glasses wearers.

Our vision relies on light entering the pupil and hitting the retina, which sends signals to the brain to convert into visual images. Conventional lenses without any coatings will reflect a small percentage of light away from the eye; less light entering the eye means less visual information for the brain to interpret, which results in slightly reduced optical clarity. With an anti-reflective coating in place, up to 99.5% of light rays are allowed to enter the eye, and this results in sharper vision.

Anti-reflective coatings also have the added benefit of improving the look of glasses aesthetically. With less light reflected, lenses look more invisible to those observing them and allows others to see the wearer’s eyes rather than their lenses. And while this coating does reflect some light back, lens labs are able to manipulate the coating to reflect a much dimmer colour in comparison to white, such as green or blue.

Are There Different Kinds of Anti-Reflective Coatings?

There are several coatings that may be applied to lenses. The first is a clear hard coat, which treats the surface of the lens with a scratch-resistant protective layer. This coating is usually the base layer and has no colour or other optical properties to it, and is considered standard just as an anti-reflective coating is.

Anti-reflective lens coatings - uncut lenses - 360 Eyecare blogAn anti-reflective coating can vary in quality between manufacturers. Some may offer a coating that includes oleophobic and hydrophobic properties, which help to repel water and oils secreted from our skin and make it easier to clean with proper lens cleaner and microfibre cloths and stay clean longer. These advanced coatings will cost a bit more in comparison to basic anti-reflective coatings but are worth the price for the ease of care and higher quality vision as a result.

Older anti-reflective coatings were factory applied onto lenses almost like a layer of paint. These coatings were softer and could scratch off over time or through improper handling of the glasses. These coatings were also very sensitive to temperature fluctuations and would crackle and start to break down after a few years.

With newer advancements in chemical engineering technology, coatings are more consistently adhered to the lenses down to the microscopic level with vacuum deposition technology, which results in a stronger coating layer that resists “flaking away” like its older counterparts. Newer, better coating techniques and technologies improve even on this, greatly extending the usable life of the lenses. Most companies will offer several tiers of anti-reflective coatings, and the more expensive options will typically be using these newer technologies.

Want to discuss anti-reflective coatings and how they can improve your visual quality? Feel free to contact or drop by either of our offices – 360 Eyecare – Rosedale or 360 Eyecare – Beaches and speak with our trained and licensed opticians.

Categories Lenses
high index lenses

High index lenses

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.

Notebook and pencil next to folded pair of glasses

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.

Categories Lenses
Diagram of eye surface profile

Orthokeratology

Orthokeratology or ortho-keratology also referred to as “Ortho- K”, “overnight vision”, and “Corneal Refractive Therapy”. Is a lens that is prescribed in cases of nearsightedness, astigmatism, hyperopia, childhood myopia and in some mild cases of presbyopia. Ortho keratology takes the place of daily wear and use of glasses and contact lenses by lens wear overnight to temporarily re-shape the cornea.

Ortho-keratology acts like a retainer for the eyes it helps to reshape the cornea and how the light is refocused at the retina while you sleep providing you with clearer, crisp vision when you wake up. Through the process of reshaping the corneal tissue Ortho- K RGP lenses help to better control myopia so the patient is able to see without the daily use of contact lenses or glasses.

Who is a good candidate for ortho-k?

The best candidates for Orthokeratology are people who have mild to moderate myopia with/without astigmatism. The best candidates are those patients with an Rx less than -4.00 and astigmats lower than -1.50 .Children and Teenagers that want to be glasses free but are too young for refractive surgeries.  Also patients who are physically more active are great candidates as well because they are able to see clearly and not worry about contacts or glasses.

To determine whether or not a patient is a good candidate for these therapeutic lenses, the first step is to have a visit with an optometrist and from there will be referred to an orthokeratologist who will overview the overall ocular health of the eye and also takes a map of your cornea using a machine called a topographer.

With measurements and a map of your cornea, a computer controlled lathe shapes the lens with various specialized curves which further helps to reshape the corneal tissue.

Child fitting and Myopia.

Orthokeratology is also a great alternative for children as it may be a struggle of consistently making sure that the child is wearing their glasses or contacts during the day to further reduce myopia.  With the help of ortho-k it makes it easier on the parents as most myopia control involves the cooperation of not only the child but most importantly the parent/guardian of the children. As a child the cells in the eye tend to regenerate and grow more rapidly than an adult’s eye would progress.  It has been proven to be more effective because the more a child ages the possibility of becoming more myopic increases.

Benefits of Ortho- Keratology

The benefits of ortho-k is that it is a non-surgical method, no need for daily contacts or glasses wear. And an overall vision improvement.

Disadvantages

Takes longer to see results, currently only for myopia patients, not a permanent solution to vision correction. The ortho-K lenses are more expensive to start compared to glasses and contacts.

Side effects

Ortho-k has been proven to be effective but can only be as effective if the candidate is consistent with wearing time. Upon removal of lenses for an extended period of time the eye will return to original shape and refractive error will come back. As this procedure is reversible there have been reported side effects of blurry and fluctuating vision. As these are a variation of an RGP lens the same risks and side effects still apply.

Works Cited

“Overnight Ortho-K in Children Significantly Reduces Peripheral Myopia.”Healio: Medical News, Journals, and Free CME. N.p., n.d. Web. 27 May 2016.

“Orthokeratology: Reshaping Your Eyes With Contact Lenses.” All About Vision. N.p., n.d. Web. 04 May 2016.

“What Is Orthokeratology?” AAOMC. N.p., n.d. Web. 04 May 2016.

“What You Should Know About Orthokeratology (ORTHO-K).”EyeHealthWeb.com. N.p., 26 Jan. 2013. Web. 24 May 2016.