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With a highly-motivated patient with high refractive error, fitting specialty contact lenses is worth the challenge.
While the definition of the boundary between “low” and “high” refractive error may vary among clinicians, patients with a spectacle refraction greater than -10.00D and +6.00D may be considered as having extremely high myopia and extremely high hyperopia respectively. A large population-based study of people aged 4 to 74 years in the U.S. showed that over 500,000 people had high or extreme myopia.1
Compared with a “typical” -2.00D myope, these patients present a greater challenge to the contact lens practitioner and often require more time and greater care in the clinical setting. However, these patients are also likely to be successful fits. The optical and cosmetic advantages of contact lenses over spectacles in high refractive error make these patients particularly motivated to wear contact lenses.
Fitting high refractive error patients
Accurate measurement of vertex distance during the subjective refraction is particularly important in arriving at the correct spectacle plane refraction. Trial lens fitting takes on added importance as high powered contact lenses may center and move differently than their low powered counterparts. The different geometries also play a role in oxygen transmission to the eye. For example, a -15.00D soft lens may have the same center thickness (and thus the same Dk/t) as a low minus lens made from the same material. However, the -15.00D lens will be considerably thicker in the mid-periphery and thus allow less oxygen to the eye.
Keep an eye out for complications
In addition to providing optimal contact lens care, it is essential to remain alert to the possible pathological ocular complications that are associated with high refractive error.2 High myopia is associated with increased risks of primary open angle glaucoma and chorioretinal abnormalities such as retinal detachment, atrophy, and lacquer cracks. Myopes are more likely to have tilted, rotated, and larger discs as well as other optic disc abnormalities. High hyperopes have a shorter axial length and shallower anterior chamber depth, both of which are significantly correlated with a diagnosis of primary angle closure glaucoma.
Choose a lens that CIBA Vision Specialty Lens Group offers for high refractive error: CSI® DW; Durasoft® 2; Durasoft® 2 Colors; Durasoft® 3; Durasoft® 3 Colors; Durasoft® 3 Complements
References
- McCarty CA, Livingston PM, Taylor HR. Prevalence of myopia in adults: implications for refractive surgeons. J Refract Surg. 1997;May-Jun;13(3):213-5.
- Saw SM, Gazzard G, Shih-Yen EC, Chua WH. Myopia and associated pathological complications. Ophthalmic Physiol Opt 2005;25(5):381-91.
- Congdon NG, Quigley HA, Hung PT, et al. Screening techniques for angle-closure glaucoma in rural Taiwan. Acta Ophthalmol Scand 1996;74(2):113-9.
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