Corneal hydrops
In advanced cases, bulging of the cornea can result in a localized rupture of Descemets membrane, an inner layer of the cornea. Aqueous humor from the eyes anterior chamber seeps into the cornea before Descemets membrane reseals. The patient experiences pain and a sudden severe clouding of vision, with the cornea taking on a translucent milky-white appearance known as a corneal hydrops.Although disconcerting to the patient, the effect is normally temporary and after a period of six to eight weeks, the cornea usually returns to its former transparency. The recovery can be aided nonsurgically by bandaging with an osmotic saline solution. Although a hydrops usually causes increased scarring of the cornea, occasionally it will benefit a patient by creating a flatter cone, aiding the fitting of contact lenses. Corneal transplantation is not usually indicated during corneal hydrops. Epidemiology
The National Eye Institute reports keratoconus is the most common corneal dystrophy in the United States, affecting about one in 2,000 Americans, but some reports place the figure as high as one in 500. The inconsistency may be due to variations in diagnostic criteria, with some cases of severe astigmatism interpreted as those of keratoconus, and vice versa. A long-term study found a mean incidence rate of 2.0 new cases per 100,000 population per year.
A number of studies suggest vigorous eye rubbing contributes to the progression of keratoconus, and people should be discouraged from the practice. Keratoconus differs from ectasia, which is caused by LASIK eye surgery. Post-LASIK Ectasia has been associated with the excessive removal of the eyes stromal bed tissue during surgery. Diagnosis
Prior to any physical examination, the diagnosis of keratoconus frequently begins with an ophthalmologists or optometrists assessment of the persons medical history, particularly the chief complaint and other visual symptoms, the presence of any history of ocular disease or injury that might affect vision, and the presence of any family history of ocular disease. An eye chart, such as a standard Snellen chart of progressively smaller letters, is then used to determine the persons visual acuity. The eye examination may proceed to measurement of the localized curvature of the cornea with a manual keratometer, with detection of irregular astigmatism suggesting a possibility of keratoconus. Severe cases can exceed the instruments measuring ability. A further indication can be provided by retinoscopy, in which a light beam is focused on the persons retina and the reflection, or reflex, observed as the examiner tilts the light source back and forth. Keratoconus is amongst the ophthalmic conditions that exhibit a scissor reflex action of two bands moving toward and away from each other like the blades of a pair of scissors.If keratoconus is suspected, the ophthalmologist or optometrist will search for other characteristic findings of the disease by means of slit lamp examination of the cornea.