[Transient visual deterioration by exposure to cold, phacic anterior chamber lens and forme fruste keratoconus. How can this be explained?].

This article reports on a 41-year-old male patient with forme fruste keratoconus and intolerance to contact lenses. An iris-supported intraocular lens was inserted in this eye with initially satisfactory results. During wintertime the patient coached a team of biathletes even in very low temperatures and/or windy conditions and after 2-3 h experienced a deterioration of vision in this eye. The contralateral eye with a contact lens never gave any such problems in this cold environment. Several factors might be responsible for this deterioration of vision. A very low outside temperature with or without wind induces evaporation of the tear fluid resulting in a more viscous lipid content than in warm conditions. A thin cornea facilitates faster cooling of the aqueous humor and less warming of the aqueous humor due to a deep anterior chamber where the warming iris is more distant from the cornea and partially covered by the optic and haptic of the implanted lens both of which have low heat transmission and slower exchange of the aqueous humor via the small peripheral iridotomy in comparison to the pupil which is covered by the implanted lens. Populations, such as Inuits and Mongolians who permanently live in cold environments, have developed shallow anterior chambers during evolution which protects the cornea from the cold due to the reduced distance from the warming iris to the cornea. In retrospect the implantation of a refractive lens into the posterior chamber would probably have been the better choice in this particular patient constellation.