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Keratoconus is a chronic, non-inflammatory disease of the cornea with onset in early adulthood.1,2 The National Eye Institute reports that keratoconus is the most common eye dystrophy in the U.S., affecting approximately 1 in every 2,000 Americans.3
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| Corneal Topography |
Diagnosis
Modern equipment with sophisticated software, such as corneal topographers, have helped greatly in identifying keratoconus, particularly the subclinical stages of this condition.4 In the basic office setting however, diagnosing keratoconus may be somewhat challenging as these patients usually have difficulty determining differences during forced-choice testing. There are a few telltale signs to look for though. Patients with keratoconus usually tell clinicians that their habitual correction is just not as clear and sharp as it could be. They also have decreased acuities and show high amounts of cylinder at an oblique axis.
Structural manifestations5,6
- Inferior steepening with medial shift
- Central thinning
- Irregular astigmatism
- One eye is usually more affected than the other
Clinical Features7
- Vogt striae
- Iron deposits at relative depressions in the cornea (Fleischer rings)
- Corneal scarring
- Distorted and steep mires with manual keratometry
Correcting for Keratoconus
Individuals with early, subclinical keratoconus may be corrected with either glasses or soft contact lenses. However, as the condition becomes manifest, gas permeable (GP) lenses are the modality of choice due to their ability to mask the refractive effects of the irregular cornea.
Piggyback Fit
Some patients may become intolerant to GP lenses as the condition progresses. Alternatives for these individuals include hybrid lenses such as the SoftPerm® or a piggyback fit whereby a GP lens is fit over the top of a high Dk soft lens.8 As the condition progresses to the more moderate and severe stages, contact lenses become a medical necessity. Keratoconus is a progressive disease and will require frequent changes in the contact lens prescriptions.
The overall time-course of treatment with contact lenses for keratoconus varies widely from patient to patient. Attempts should be made to manage the condition with contact lenses for as long as possible prior to opting for penetrating keratoplasty.
Click here to see the lens CIBA Vision Specialty Lens Group offers for keratoconus: SoftPerm®
References
- Kymes SM, Walline JJ, Zadnik K, Gordon MO. Quality of life in keratoconus. Am J Ophthalmol 2004;138(4):527-35.
- Pobelle-Frasson C, Velou S, Huslin V, et al. [Keratoconus: what happens with older patients?]. J Fr Ophtalmol 2004;27(7):779-82.
- Rabinowitz YS. Keratoconus. Surv Ophthalmol 1998;42(4):297-319.
- Arntz A, Duran JA, Pijoan JI. [Subclinical keratoconus diagnosis by elevation topography]. Arch Soc Esp Oftalmol 2003;78(12):659-64.
- Nichols JJ, Steger-May K, Edrington TB, Zadnik K. The relation between disease asymmetry and severity in keratoconus. Br J Ophthalmol 2004;88(6):788-91.
- Burns DM, Johnston FM, Frazer DG, et al. Keratoconus: an analysis of corneal asymmetry. Br J Ophthalmol 2004;88(10):1252-5.
- Zadnik K, Barr JT, Gordon MO, Edrington TB. Biomicroscopic signs and disease severity in keratoconus. Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study Group. Cornea 1996;15(2):139-46.
- O'Donnell C, Maldonado-Codina C. A hyper-Dk piggyback contact lens system for keratoconus. Eye Contact Lens. 2004;30(1):44-48.
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