DEFINITION:  It is a progressive disease where the perpendicularity of the cornea increases (conically tapering of the cornea toward the front) and its thickness decreases and which is characterized by irregular astigmatism.

Figure 1. Slit-lamp photograph of a healthy eye (left), an eye with keratoconus demonstrating increased corneal curvature (ectasia) (right). 

SYMPTOMS AND FINDINGS: Patients come to the clinic with the complaint of decrease in vision due to increasing irregular myopia-astigmatism. Although asymmetrical in general, the involvement of both eyes is in question. The disease may start in puberty and proceed up to the ages of 30-40. There are such examination findings as oil-drop reflect in direct ophthalmoscope, scissors reflect in skiascope, thin vertical streaking in deep stroma (vogt lines), iron accumulation at the bottom of the cornea (fleischer ring), corneal thinning, and increase in the perpendicularity of the cornea.

CAUSES AND RISK FACTORS: This disease may occur along with such systemic diseases as Down, Turner, Ehlers Danlos, Marfan syndrome, atopy, osteogenesis imperfecta, mitral valve prolapse, and mental retardation. It may also emerge along with such ocular diseases as vernal keratoconjunctivitis, blue sclera, aniridia, ectopia lentis, Leber’s congenital amaurosis, and retinitis pigmentosa.

Figure 2. Tomography map of an eye diagnosed with keratoconus.

AUXILIARY INVESTIGATIONS AND DIAGNOSIS: Diagnosis is made through clinical history and examination. To finalize the diagnosis and follow the progress of the disease, corneal topography, keratometry, and pachymetry are used.

TREATMENT: Glasses are used in the early stages, and solid contact lenses (keratoconic lenses) are used when glasses are insufficient. In advanced cases where vision notably decreases, cornea transplantation can be made. Corneal cross-linking and corneal ring treatments are among surgical treatments applied recently in early and mid terms.