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Contact Lens Evaluation Q&A with Dr. Coker

Q: What is the difference between an eye exam geared towards wearers of glasses and an eye exam geared towards wearers of contact lens? What can be expected during a contact lens evaluation?

Dr. Coker: A comprehensive eye examination geared towards an eyeglasses wearer includes checking vision with and without current glasses, checking eye pressures, peripheral vision, refraction (determine the strength of glasses necessary to see our best), and health of the front and back of the eye. In contrast, an exam geared towards a contact lens wearer includes everything in a comprehensive exam as well many additional tests and procedures. These include measurement of the curvature of the eye where the contact sits (cornea), careful determination that the whole front of the eye (cornea, conjunctiva, and eyelids) is appropriately healthy for contact lens wear, calculation of a contact lens prescription using the glasses prescription (the strength is often not the same in our contacts as our glasses) and review of contacts available with such prescription, and, if necessary, teaching the patient how to care for, insert and remove the contact lenses. After the health of the eye is determined sustainable for contact lens wear, the best matching brand and strength contact lens is placed on the eye and evaluated for fit. This includes if the contact lens is too tight or loose and appropriately aligned (especially important with astigmatism). After the contact lens is appropriately fit the vision will be tested again, and if the contact is new to the patient, we will schedule a follow-up examination to re-evaluate the contact lens fit after 1-2 weeks to ensure that with daily wear the contact remains comfortable and with good vision. At this point the contact lens prescription is "finalized" and contacts are ready to be ordered!

Q: What are contact lens measurements?  How is that determined?  Does it change if a patient has astigmatism?

Dr. Coker: Contact lens measurements include the sphere, cylinder, axis, base curve, and diameter. The first three are similar to glasses measurements and the "sphere" is the strength to necessary to correct near-sightedness or far-sightedness, the "cylinder" is the strength of astigmatism necessary to correct for glare and distortions, and the "axis" determines how the astigmatism is aligned on the eye, and therefore helps best correct the glare. The base curve tells us how steep or flat the contact is. Some corneas (the front, clear part of the eye) are shaped more like a pointed mountain and need a steep lens (which has a low base curve) while others are shaped more like a rolling hill and need a flat lens (high base curve). Last is the diameter, this tells us how large the lens is. Contact lenses come in a variety of sizes, however, most soft disposable contact lenses are around 14 millimeters in diameter.

Q: What kind of instruments and tests can I expect to see during a contact lens exam?

Dr. Coker: During a contact lens exam you can expect to have all normal tests conducted for glasses as well as topography to determine the curvature of the eye, close evaluation of the front of the eye and eyelids for signs of dry eye, allergies, or other problems that may interfere with contact lens wear, evaluation of the fit of the contact lens on the eye itself, and acuity testing to ensure that you are seeing your best with your new contacts.

Q: What are trial lenses?  How can an eye doctor best determine the right contact lens prescription?

Dr. Coker: Contact lenses come in many different brands, materials, wear modalities (contacts that last 1-month, 2-weeks, 1-day, etc) strengths, shapes, and sizes. We have many single containers of these different contact lenses in our office for our patients to try during their contact lens exam. These are called trial lenses. Every contact lens evaluation will include trial lenses to ensure the best contact fit and vision before ordering contacts. The best contact lens prescription is determined first by using the glasses prescription, calculating any differences necessary, finding the correct strength trial contact lens, and checking (and correcting, if necessary) the strength of the contact once it is on the eye.

Q: Will I know right away if the contact lenses fit or is that something that can only be felt with the passage of time?

Dr. Coker: Often a contact lens will feel comfortable initially but may dry out or become uncomfortable over time. Similarly, sometimes a contact will feel clear at first and become blurry over time as it dries or the fit changes. This is why with any new contact lens or change in contact lens strength or fit we provide trial lenses and follow up with an additional appointment 1-2 weeks later before ordering contacts.

Q: Why does a contact lens exam cost more than an eyeglass eye exam?

Dr. Coker: A contact lens exam costs more than an eyeglass exam because there are many additional tests, procedures, and trial lenses involved. Often one (or more) follow-up exams and multiple contact lens trials are required. Also, anyone wearing contact lenses for the first time must be taught appropriately how to insert, remove, and care for their new contacts. The contact lens evaluation fee covers all of these tests, procedures, trials, follow-ups, and instruction.

Q: What are some advantages and disadvantages of contact lenses?

Dr. Coker: Some of the advantages of contact lenses are increased peripheral vision (no longer limited by the frame of your glasses), no pressure from the frame of glasses on your nose or behind the ears, no glasses to slide down your nose or off of your face when sweating or being active, no change in the size of your eyes and head behind your glasses (more noticeable for those with strong glasses), no glasses to get dirty, and more. The disadvantages of contact lenses include that they must be carefully cleaned and maintained. Contacts can be dangerous and even cause permanent loss of vision if not properly taken care of. This includes not sleeping in or swimming in contacts, replacing solution nightly and cleaning the lenses before inserting them, disposing of contacts based on the proper schedule (some contacts are good for 1 month, some 2 weeks, some 1 day).

Q: How does an eye doctor determine which contact lens brand to recommend to a patient?  Whether to use daily contacts or reusable?

Dr. Coker: Different brands of contacts use different materials, shapes, and designs and the brand is best determined based on the particular needs of each patient. For example, if a patient has dry eyes or allergies they will most likely like or require a daily disposable lens that is thinner and less likely to get buildup or deposits.

Q: Are contact lenses for everyone?

Dr. Coker: Contact lenses are not for everyone. There are many eye conditions that may get worse with contact lens wear such as extreme dry eye or allergies, too small of an opening between the eyelids, bumps or irritation on the eye or eye lids, or others. Also, some people may need a certain strength that is not available in a contact lens. In other cases, a person may be a good candidate for contacts but are unable to put the contacts on or take them off themselves.

Q: Are there special contact lenses for dry eye?  Astigmatism?  Insert other eye problem?

Dr. Coker: For those with dry eyes or allergies it is best to use a daily disposable contact lens that is thinner and lighter than others. Using a fresh, new clean lens every day causes less irritation to the eyes and some daily disposable contact lenses have a special smooth/oily coating that protects against dry eye and irritation. Those with astigmatism will need a "toric" contact lens. A toric contact lens is shaped differently than a regular contact lens and often is weighted to allow for the contact to sit on the eye in a particular orientation. As the contact orients correctly on the eye it better corrects the glare caused by astigmatism.

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