A regular, comprehensive eye exam is an important part of maintaining your ocular health. Those of us who have a refractive error in the form of myopia (nearsightedness), hyperopia (farsightedness), presbyopia (age-related farsightedness), or astigmatism (irregularly shaped cornea), also visit the optometrist to make sure we have the correct prescription for the best vision possible. Eyeglasses and contact lenses are the most common options for correcting refractive error; laser refractive surgery is another option this is becoming common.
Corrective eyeglasses were first made in the 13th century, and were far less sophisticated and fashionable than they are now. Frames now come in a wide variety of styles and brands to fit both your visual needs and your fashion sense.
Your prescription will determine whether you need single vision, bifocal, or progressive lenses. Most people who wear glasses will start off with single vision lenses, which correct for one distance only, and will begin to wear bifocals or progressives in their 40s or 50s when they start to develop presbyopia and need correction for reading.
Here are a few things to know about lenses:
- There are varying degrees of lens compression, which are referred to as indexes. A higher index lens will be thinner than a lower index lens of the same prescription. The level of index that you want or need will be primarily related to the strength of your prescription. If you need a high degree of correction, you may need a higher index lens in order for the lens to fit neatly into a frame.
- Lenses are available in different materials and with a variety of coatings. You may consider options such as tints, UV protection, impact resistance, scratch resistance, etc.
- You may be given the option of choosing traditional or digital lenses. This relates to the way the lens surfacing is done. The recommended option may vary depending on your prescription.
- Specialty lenses and/or frames may be desirable if, for example, you work in an industrial setting and need safety glasses; or if you are sensitive to digital viewing and need an anti-reflective coating on your lenses or eyewear specifically designed for blue light.
Selecting and Fitting Eyeglasses
There are a few steps involved in selecting and fitting eyeglasses:
- Frame size, lens size, bridge width, temple length, shape, wrap, material, and overall fit are important parts of choosing frames.
- Measurements will be taken by the person who is fitting you for glasses to determine your pupillary distance (PD) and optical centres (OC). These measurements are taken as part of the eyeglass fitting process and are not part of the prescription provided by your optometrist.
- Other measurements including face form, eye size, and temple length may also be required to get a perfect fit.
- Lenses, tints, and coatings will be decided based on your individual needs/wants, your prescription, lifestyle, and work demands.
After your lenses have been made and placed in the frames, the person fitting your glasses will confirm that they have been properly manufactured within acceptable tolerance, and will adjust the frames to your face, making sure they are sitting properly. Periodic adjustments will likely be necessary to maintain the correct fit of your glasses. Poorly fitting eyeglasses can cause eyestrain, a pulling sensation, headaches, nausea, and blurry vision.
Eyewear: Contact Lenses
The first usable contact lenses were made in the 19th century out of glass that covered the whole eye. Contact lenses have gone through many changes in process and material since then to become the comfortable, long-wearing, and popular vision correction option available today. Contact lenses have also been developed for therapeutic uses in the treatment of some eye conditions.
Contact lenses are medical devices. They require a special prescription which is different from an eyeglass prescription, and they must be fitted by a licenced eye care professional. Every eye is different, even your own two eyes. The unique characteristics of your eyes need to be accommodated with precision. Poorly fitting contacts can result in irritation, infections, corneal scratches, and sometimes even blindness.
There are a few steps involved in proper contact lens fitting:
- During your eye exam, your overall eye health will be evaluated to ensure your eyes are suitable for wearing contacts. If you require vision correction, a prescription will be issued for the eyeglass lens correction you need. This value wil be converted into your contact lens correction.
- A keratometer will be used to determine the curvature of your eye, which will determine the curvature and size of your contact lenses.
- The health of your cornea and the dryness of your eyes will be assessed to determine the best contact lens composition and solution. This requires a test to evaluate the tear film of your eyes. Allergies and lifestyle will also be considered.
- You will need to use a trial pair of contact lenses for a period of time. At a follow-up appointment, your optometrist will determine if your contacts are providing optimal comfort and clarity, while maintaining healthy eyes. If they are, a final contact lens prescription will be provided.
It's important to understand that every contact lens product is unique and designed for a particular purpose. This includes everything from material, curvature, fit, oxygen permeability, deposit resistance, moisture content, and lifespan. It is never recommended to switch the brand of lenses you are using without consulting a licenced eye care professional.
Multifocal Contact Lenses
Similar to bifocal or progressive eyeglasses, multifocal contact lenses provide correction for multiple distances.
Scleral Contact Lenses
The sclera is the protective outer layer of the eye which is commonly called the white of the eye. Scleral contact lenses get their name from the fact that they rest on the sclera as opposed to regular contact lenses that rest on the cornea. Scleral lenses are larger than regular contact lenses and have a raised area in the centre that serves as a reservoir for artificial tears. Scleral contacts are used to treat conditions such as severe dry eye, keratoconus (cone-shaped cornea), Sjögren's syndrome (autoimmune disease casing dry eyes), microphthalmia (developmental disorder causing one or both eyes to be abnormally small), aniridia (absence of the iris), and other eye complications, disorders, or injuries.
Cosmetic or Decorative Contact Lenses
Decorative contact lenses do not necessarily provide refractive correction, but rather are used to alter the appearance of the eye. Some examples of decorative contact lenses are those that change eye colour, give the appearance of a cat eye, or circle contact lenses which enlarge the eyes to make them look like a doll's eyes. In the past, decorative contact lenses have been unregulated and available at costume shops and drug stores; however as of July 16, 2016, a new law is in place to regulate decorative contact lenses as Class II medical devices in Canada, with a one year compliance grace period for manufacturers and full regulation in July 2017.
Contact lenses of any type carry risks, and the risk is heightened when the manufacture and distribution is not regulated according to appropriate medical standards. There have been reports of serious complications resulting from unregulated cosmetic contact lens use. Under the regulation, decorative contact lenses will require fitting by a licenced eye care professional.
Internet providers are not regulated and therefore are not held to the same standards that optometrists and opticians are held to under Manitoba legislation. In Manitoba, the Manitoba Association of Optometrists and the Opticians of Manitoba both regulate the dispensing of eyewear, ensuring the safety and accuracy of your eyewear. Research has found that almost half of the eyewear ordered online failed at least one parameter of optical or impact testing.
When ordering eyeglasses online, the consumer is taking on the role of a trained optical dispenser. This includes taking technical measurements and making critical decisions with respect to frame, lens, and material selection. Common complaints regarding improperly ordered or fit eyewear include headaches, fatigue, an "eye pulling" sensation, nausea, and pain or pressure marks on the nose or around the ears.
Contact lenses are medical devices and lenses that don't fit correctly or are used improperly can cause serious damage to your eyes, including blindness in some cases. Many online sites, including those based in Canada, sell products that have not been approved by Health Canada and have not been tested for safety.
Laser Refractive Surgery
Refractive surgery is done to correct a refractive error such as myopia (nearsightedness), hyperopia (farsightedness), presbyopia (age-related farsightedness), or astigmatism (irregularly shaped cornea). The refractive error is corrected by reshaping the cornea (the front part of the eye that covers the pupil and iris) or by implanting a lens in yoru eye. The most common type of laser refractive surgery is LASIK. Laser surgery techniques have improved in recent years, but still carry some risks and surgery may not be recommended for people with certain conditions. If you are considering laser refractive surgery, ask your optometrist about your eye health and suitability.