Keratoconus (from Greek: kerato- horn, cornea; and konos cone), is a degenerative non-inflammatory disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than its normal gradual curve. Keratoconus can cause substantial distortion of vision, with multiple images, streaking and sensitivity to light all often reported by the patient. Though frequently thought of as a rare condition, keratoconus is the most common dystrophy of the cornea, affecting around one person in a thousand, and it seems to occur equally in all ethnic groups worldwide. It is typically diagnosed in the patient's adolescent years and attains its most severe state in the twenties and thirties.

Keratoconus is a little-understood disease with an uncertain cause, and the course of its progression following diagnosis is unpredictable. If in both eyes, the deterioration in vision associated with the disease can affect the person's ability to drive a car or read normal print. It does not lead to blindness, and in most cases, corrective lenses are effective enough to allow the patient to continue to drive legally and likewise function normally. Further progression of the disease may lead to a need for surgery. Keratoconus continues to be a somewhat mysterious disease, but it can be successfully managed with a variety of clinical and surgical techniques, and often with little or no impairment to the patient's quality of life.

History

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In a 1748 doctoral dissertation, a German oculist named Burchard Mauchart provided an early description of a case of keratoconus, which he called staphyloma diaphanum. However, it was not until 1854 that British physician John Nottingham clearly described keratoconus and distinguished it from other ectasias of the cornea.Nottingham J. Practical observations on conical cornea: and on the short sight, and other defects of vision connected with it. London: J. Churchill, 1854. Canadian archives. Nottingham reported the cases of "conical cornea" that had come to his attention, and described several classic features of the disease, including polyopia, weakness of the cornea, and difficulty matching corrective lenses to the patient's vision. In 1859 British surgeon William Bowman used an ophthalmoscope (recently invented by German physician and physicist Hermann von Helmholtz) to diagnose keratoconus, and described how to angle the instrument's mirror so as to best see the conical shape of the cornea.Bowman W, On conical cornea and its treatment by operation. Ophthalmic Hosp Rep and J R Lond Ophthalmic Hosp. 1859;9:157. Bowman also attempted to restore the vision by pulling on the iris with a fine hook inserted through the cornea and stretching the pupil into a vertical stenopeic slit like that of a cat. He reported that he had had a measure of success with the technique, restoring vision to an 18-year old woman who had previously been unable to count fingers at a distance of 8 inches (20 cm). By 1869, when the pioneering Swiss ophthalmologist Johann Horner wrote a thesis entitled On the treatment of keratoconus,Horner JF, Zur Behandlung des Keratoconus. Klinische Monatsblätter für Augenheilkunde. 1869. the disorder had acquired its current name. The treatment at that time, endorsed by the leading German ophthalmologist Albrecht von Gräfe, was an attempt to physically reshape the cornea by chemical cauterization with a silver nitrate solution and application of a miosis-causing agent with a pressure dressing. In 1888 the treatment of keratoconus became one of the first practical applications of the then newly-invented contact lens, when the French physician Eugène Kalt manufactured a glass scleral shell which improved vision by compressing the cornea into a more regular shape.Kalt E, reported by Panas P, translated by Pearson R. Kalt, keratoconus and the contact lens. (1888). Bull Aced Med, 19, 400 Optom Vis Sci; (1989) 66, 643 PMID 2677884 Since the start of the twentieth century, research on keratoconus has both improved understanding of the disease and greatly expanded the range of treatment options.

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