An instrument called a keratometer is used to measure the curvature of your cornea front surface of the eye where the contact sits. Sometimes we need to map out the entire cornea with a device called a topographer.
The size of the lens is based on how curved the cornea is. Most contacts look and feel great when they are first inserted, but after a few hours of wear can be very different.
That is why in most cases a follow up contact lens check is important. This is usually scheduled a week or two after your fitting. What are you planning on using your contacts for? Will you be using them every day? Do you only use them only for special occasions? Contacts come in daily, weekly, biweekly, monthly, and annual replacement schedules. Depending on your wearing schedule and eye health, we will suggest one that will be the healthiest and most cost effective.
There are various types of contacts, some for sensitive eyes, some for astigmatism, and even some for those who need bifocals. You can even select colored contact lenses. He might try a couple of different pairs depending on your vision and comfort. Once you both have determined which type of contact lenses are right for you, your doctor will order a full set of contacts.
Come in to any Stanton Optical store the next time you need either an eye exam for prescription glasses or want to be fitted for contact lenses. Using an instrument known as a keratometer, your doctor will determine the curvature of your cornea, the clear part of your eye. Keratometers only measure a small section of the cornea, so a corneal topographer may be used as well. During this test, you will sit facing the machine with your forehead resting on a brace. A light is then shined into your eye.
The corneal topographer analyzes how your eye reflects the light, which gives the precise measurements of your cornea. Your optometrist may need even more information about your eyes, so he or she may also utilize a device for wavefront measurements. This test will also reveal if you have astigmatism. Astigmatism is quite common and refers to any irregularities in the curvature of the cornea or lens.
This condition can be treated using either gas permeable or toric contact lenses. Although there are machines that measure the horizontal and vertical diameter of your pupil, many optometrists still prefer the ruler approach. Whichever method your doctor chooses, he or she will likely use the same one to measure your iris, the coloured part of the eye.
Your contact lenses should not only fit your eye perfectly, but also blend in. These measurements will ensure that your lenses look natural. One of the biggest issues contact wearers face is dry eye syndrome. If left unchecked, this dryness can damage the surface of your eye, which can, in turn, lead to infection. Any of the following conditions can make contact lens fitting and comfortable contact lens wear more challenging:.
Giant papillary conjunctivitis GPC. If you have or suspect you have any of these conditions and you want to wear contacts, visit an eye care professional who specializes in contact lenses and welcomes hard-to-fit patients.
Contact lens specialists usually are more aware of the latest contact lens technology and options than a general eye doctor. Many also use advanced equipment that can measure your cornea more precisely to achieve the best contact lens fit possible. If you have keratoconus and cannot see as clearly as you would like to with glasses , you typically will see better if you are fitted with contact lenses specially designed for irregular corneas.
Contacts for keratoconus improve vision by optically replacing the irregular shape of the cornea with a smooth, uniform surface that enables light to form a sharper focus on the retina. Today several types of contact lenses can correct vision problems caused by keratoconus. They include:. Gas permeable contact lenses. For mild to moderate keratoconus, many contact lens specialists recommend rigid gas permeable contact lenses.
These lenses — also called GP or RGP lenses — are made of a rigid oxygen-permeable material, so they retain their shape on the eye and do not conform to the shape of the underlying cornea.
Because of this feature, GP contacts eliminate blur caused by irregularities in the cornea and therefore provide sharper vision than glasses. Piggybacking contact lenses. Sometimes, GP lenses will provide excellent vision for a person with keratoconus, but the wearer finds the rigid lenses uncomfortable and cannot wear them for an entire day. In these cases, a fitting technique called piggybacking may be used. In piggybacking, a soft contact lens is worn under the gas permeable lens, acting as a cushion to reduce or eliminate any discomfort caused by the GP lens.
Large-diameter scleral and semi-scleral GP lenses rest on the sclera and vault over the misshapen cornea in keratoconus. Scleral contact lenses. For these situations, a contact lens specialist may recommend large-diameter GP lenses called scleral contact lenses. Scleral lenses rest on the white sclera of the eye and vault over the irregularly shaped cornea.
In addition to providing a more stable fit, scleral lenses sometimes are more comfortable than smaller GP lenses on a keratoconic eye because they don't exert any pressure on the sensitive corneal tissue. Hybrid contact lenses. Hybrid contacts are large-diameter lenses that have a rigid gas permeable central zone, surrounded by a peripheral zone made of soft or silicone hydrogel material.
The purpose of this design is to provide the visual clarity of GP lenses, combined with wearing comfort that is comparable to soft lenses.
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