It may cause luminous objects to appear as cylindrical pipes with the same intensity at all points. The classic symptom of keratoconus is the perception of multiple "ghost" images, known as monocular polyopia. This effect is most clearly seen with a high contrast field, such as a point of light on a dark background. Instead of seeing just one point, a person with keratoconus sees many images of the point, spread out in a chaotic pattern. This pattern does not typically change from day to day, but over time, it often takes on new forms. People also commonly notice streaking and flaring distortion around light sources. Some even notice the images moving relative to one another in time with their heartbeat. The predominant optical aberration of the eye in keratoconus is coma. The visual distortion experienced by the person comes from two sources, one being the irregular deformation of the surface of the cornea, and the other being scarring that occurs on its exposed highpoints. These factors act to form regions on the cornea that map an image to different locations on the retina. The effect can worsen in low light conditions, as the dark-adapted pupil dilates to expose more of the irregular surface of the cornea. Genetics
Six genes have been found to be associated with the condition. These genes include BANP-ZNF469, COL4A4, FOXO1, FNDC3B, IMMP2L and RXRA-COL5A1.
Reactive perforating collagenosis is a rare, familial, nonpuritic skin disorder characterized by papules that grow in a diameter of 4 to 6mm and develop a central area of umbilication to which keratinous material is lodged. The cause of reactive perforating collagenosis is unknown. Clinical Features
Inherited form
Keratotic papules measuring 1 to 6 mm develop on the extensor surface of the hands, the elbows, and the knees following superficial trauma. These lesions are painless. They appear as pin-sized lesions that grow to a papule of about 6mm in the following 3–5 weeks. They undergo spontaneous resolution in about 6–8 weeks leaving residual scarring. Lesions may recur throughout life. Cold weather is one of the factors known to trigger recurrences. Acquired form
In this form, keratotic papules develop on the trunk and extremities. These are commonly associated with pruritus. Lesions may or may not be related to superficial trauma. See also
Elastosis perforans serpiginosa
List of cutaneous conditions

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