EyeWitness

Spring 2017

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18 CLSA EyeWitness Spring 2017 amblyopia can develop. Hybrid lenses may be considered when GP lenses are not tolerated. In addition, tandem (pig- gy-back) lenses have been reported as useful in the pediatric population. Application and Removal Small, tight fissures along with the pro- tective mechanism of closing the eye and Bells' phenomenon can make con- tact lens application and removal chal- lenging. One factor that determines which lens may be best may be the one that can be applied and removed by the caregiver or the child. Larger diameter soft lenses are more difficult to apply than smaller GP lenses. Sil- icone hydrogel materials are easier to apply than other soft lenses due to in- creased modulus. The child should be encouraged to apply and remove their properly fit and more adaption time to tolerate. Although somewhat difficult, us- ing scleral lenses in children may be the best option in some cases. In my hands, children who have exposure due to a cranial nerve disorders have benefited with a scleral lens. that is highly sensitive to light may control how the eye grows and devel- ops. This special cell was named "ON Delayed" in reference to its "slow re- sponses to lights becoming brighter." Until we know more, the ophthal- mic community should continue to advocate children spend some amount of time outdoors and less time with the cell phones. CONTACT LENS OPTIONS Soft material designs All soft lenses are categorized in one of four groupings based on water content and iconicity (Groups 1-4). In 2014, the FDA added an additional category (group 5) for silicone hydrogel mate- rials. Many pediatric patients may be fitted with a "commodity" lens that is mass-produced for frequent replace- ment. The lens manufacturer suggests the frequency of replacement. This in- creased frequency of replacement helps avoid complications associated with soiled lenses. In addition, spare lenses are readily available. Single use modal- ities should be considered for children when lens parameters allow. Soft lens- es that are not marketed for single use require an appropriate care system. However, some patients may not be op- timally fitted with these "boxed" lenses due to corneal curvature and corneal diameter. Patients who desire soft con- tact lenses that cannot obtain good vi- sion or comfort may require custom soft lenses. These custom soft lenses can be fabricated in any curvature, diameter, material and prescription required. All soft lenses should demonstrate centra- tion with full corneal coverage and ap- proximately two millimeters of the lens on the sclera along with some degree of movement. Gas Permeable Lenses Gas permeable lens materials and de- signs may be used to maximize visual acuity with all refractive errors. They are most frequently used to correct ir- regular corneal astigmatism following trauma and other conditions that re- sult in irregular corneal astigmatism. However, they do require more skill to CONTACT LENS SELECTION There are a number of factors to con- sider when determining the most appro- priate contact lens for a patient. These considerations are increased when the patient is an infant or young child. Refractive error Common refractive errors such as my- opia, hyperopia and astigmatism can be corrected with soft and gas perme- able (GP) contact lenses. Soft toric lens designs with relatively high degrees of cylindrical correction may cause vari- able vision due to lens instability and rotation. Irregular corneal astigmatism Corneal irregularities are best correct- ed with GP lenses. A rigid lens will pro- vide a new, smooth refracting surface to maximize vision. This is most im- portant when the child is of the age that lenses at an early age. Obviously, this is not possible for the infant patient but children attempting to manage their own lenses often become proficient at a young age. GP FITTING TECHNIQUES The techniques the contact lens pro- fessional utilizes to fit an adult with a GP lens must be altered to fit an infant or small child. The ability to capture a reliable image with a topographer or accurate keratometric readings is often impossible to obtain in small children. Keratometric readings obtained at the time of surgery or an exam under an- esthesia should only be considered as a starting point or a guide to the initial diagnostic lens. The application and evaluation of a diagnostic lens is the best method to obtain an appropriate fit in small children. Diagnostic lenses that do not have a UV filter allow better in- The retinoscope is not only used to determine the final lens power with any type of lens but also an important instrument to guide you to the best cornea lens relationship. Pediatric fitters of contact lenses should be proficient with a retinoscope.

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