Winter 2017

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Page 26 of 35

References on file at the CLSA office Brianna Ryff, OD, FAAO joined Midwestern University after completing a residency in cornea and contact lens at Northeastern State University Oklahoma College of Optometry. She received her Doctorate of Optometry from the Southern California College of Optometry and is a Fellow of the American Academy of Optometry. She enjoys working with students and patients, but her passion is fitting specialty contact lenses for irregular corneas. Dr. Ryff also works in private practice at Desert Eye in Tempe, AZ. She is a member of the Scleral Lens Education Society and the Arizona Optometric Association. Florencia Yeh, OD, FAAO is an assistant professor at the Arizona College of Optometry – Midwestern University where she teaches in the contact lens curriculum. She is also an attending optometrist at the Midwestern University Eye Institute where she sees specialty contact lens patients. She earned her Doctor of Optometry from the New England College of Optometry and completed a Cornea and Contact Lens residency at the Indiana University School of Optometry. She is a Fellow of the American Academy of Optometry and is on the executive committee for the Arizona Chapter of the American Academy of Optometry. CLSA EyeWitness Winter 2017 25 lens on a patient's eye. Stabilization is important otherwise a patient will com- plain of fluctuating vision every time they blink. Many different companies have come up with different stabilization techniques: prism ballasting, dynam- ic stabilization (aka thin-zone designs), peri-ballasting, eccentric lenticulation, and back-surface toricity. Currently, many lens designs on the market com- bine different methods of stabilization and have been successful in maintaining clear vision throughout the day. One tip to help with faster settling of a lens on a patient's eye is to ensure that the 6 o'clock marker of a lens is placed onto the eye at the 6 o'clock position. If it were placed in any other orientation, it may take a little longer for the lens to settle. When assessing the fit of a toric lens, it is important to remember Left Add, Right Subtract (LARS). If a contact lens is rotated in a certain direction, take it into account from the spectacle prescription. For example, if the patient's spectacle pre- scription is -0.75 -2.25 x 180, but the pa- tient has a -0.75 -2.25 x 170 contact lens on the eye and the contact lens is rotated 20° right, the next contact lens chosen will have an axis of 160°. To obtain this answer, subtract (right rotation = subtract per LARS) the 20° rotation from the spec- tacle axis of 180°. Another important thing to remember is that even though the contact lens axis is changing, when it is placed back on the patient's eye, the lens will still be rotated 20° to the right. The new calculated axis has already adjusted for this amount of rotation. After performing an over-refraction and assessing a toric contact lens on a pa- tient's eye, how do you decide what contact lens to order next? If LARS is not suffi- cient to fix the patient's vision, it is helpful to remember that there are cross-cylinder calculators available through a variety of resources. These calculators can help de- termine the next contact lens to place on a patient's eye, and are especially helpful if there is a sphero-cylindrical over-refrac- tion. These calculators incorporate the patient's spectacle Rx, the contact lens that is currently on the patient's eye, the rotation amount and direction, and the over-refrac- tion. It will then compute the next best con- tact lens. While cross-cylinder calculators work well, remember that the calculator usually will not give an answer in available contact lens parameters – looking at a pa- rameter guide can help determine the pa- rameter availability. The number one rule in multifocal contact lens fitting is FOLLOW THE FITTING GUIDE. Contact lens man- ufacturers have spent a lot of time, effort, and money on creating the fitting guide to make them work! The fitting guides will not only assist in choosing an initial lens pair, but also give tips for trouble- shooting vision complaints. When fitting multifocal contact lenses, it is important to remember that the majority of multifocal contact lenses available on the market are aspheric or concentric in design. If a contact lens is decentered on a patient's eye, it is almost impossible for a patient to see clearly. Therefore, checking for decentration is a very important aspect of multifocal con- tact lens fitting. When checking visual acuity through multifocals, have the patient read the acuity chart with both eyes open first. This reinforces the fact that they can in fact see well with both eyes open before checking monocular acuities. It is also worthy to mention that over-refraction of multifocal lenses should be performed out-of-phoropter, with loose lenses. Loose lenses will allow the patient to experience a more "real-world" representation of their vision. Fitting soft contact lenses is much more simplified than GP contact lenses. As a result, they have become more and more wide spread with improved technol- ogies in toric stabilization and multifocal lens clarity. Learning the parameters and the benefits of each lens available on the market will enable a contact lens fitter to practice with ease and confidence. CONCLUSION With a multitude of soft and GP lens options available, contact lenses can be a great option for patients of all ages. For all modalities, finding out the pa- tient's goals, visual demands, and ex- pected wear time can help you deter- mine the most appropriate contact lens. Setting realistic expectations from the start can improve overall success for you and your patients. EW Acknowledgements: Thank you to Mike Johnson at Art Optical for his expertise!

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