Keratoconus is a progressive disease of the cornea characterized by thinning of the cornea that leads to surface distortion. Vision loss is primarily due to the resulting irregular astigmatism and myopia with corneal scarring being a contributing factor. The following steps will show diagnose keratoconus.
Instructions
1. Obtain the presenting signs of keratoconus. These usually consist of gradually decreasing vision because of distortions, double vision, glare and ghost images. Patients with keratoconus usually have made a number of unsatisfactory attempts to improve their vision with corrective lenses. Glasses and soft contact lenses may work for a short time, but these patients eventually will require rigid contact lenses.
2. Gather the patient history. Specific risk factors include allergies (especially those affecting the eyes), rigid contact lens wear and vigorous eye rubbing.
3. Conduct basic vision tests. Even mild keratoconus will show oblique astigmatism with at least moderate myopia. A keratometry value of up to 45 diopters is consistent with mild keratoconus, 45 to 52 diopters is considered moderate keratoconus and more than 52 diopters is severe keratometry.
4. Observe stress lines in the deep stroma in 40 percent of moderate cases of keratoconus and 60 percent of severe cases. The cornea is actually scarred in 20 percent of moderate cases and this figure rises to 70 percent for severe cases.
5. Confirm the diagnosis with a corneal topography. This will show inferior corneal steepening in 80 percent of the cases and central steepening in 15 percent of the cases. Other types of steepening or no steepening at all are rare.
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