Keratoconus: Corneal topography
Diagnosis of keratoconus: Topography Corneal
The keratoconus leads with time a myopia, un astigmatism pronounced often oblique or inverse, and a decrease in visual acuity not completely correctable by glasses glasses. It mainly affects patients under 40 years of age, as it appears a few years after the installation of eye rubbing repeated. The cause of these frictions (allergy, visual fatigue) usually occurs in childhood or adolescence.
The keratoconus is manifested by a deformation of the cornea that is not well visible to the slit lamp (except for highly evolved forms, where corneal thinning and some corneal anomalies can be seen).
The objective diagnosis of keratoconus is based on the corneal topography.
The realization of a topography of the cornea is indispensable to diagnose the keratoconus.
The topographic signs for the topographic diagnosis of the keratoconus concern the anterior face of the cornea, the posterior side of the cornea, and the thickness of the cornea (distance between the anterior and posterior sides). These signs indicate the presence of an irregular strain on both surfaces (anterior and posterior), and a central or paracentral thinning.
Here are, in short, some topographic signs of the keratoconus.
The site " Defeatkeratoconsu.com is full of examples of case of Keratoconus Very well documented on the topographic level.
On the maps of anterior curvature (topography in axial mode or instant):
– Increase of the central camber, with peripheral flattening:
– Increase in negative asphéricité (Hyper-prolate form).
– Increased corneal asymmetry (more pronounced camber in lower, irregular astigmatism, etc.)
On the maps of anterior and posterior elevation:
Increase of the amplitude between the points of elevation more positive and negative.
On maps of thickness (pachymetry, or corneal tomography):
Marked reduction of the central thickness of the cornea, lower vertical shift of the thinnest point
- Corneal profile shots reported in elevation topography (Orbscan) of a patient with a more advanced bilateral keratoconus on the right, where the deformation is perceptible in a "macroscopic" manner, and more difficult to discern on the left side ( Even if a slight asymmetry of the corneal curve is guessed. These highly evolved forms are found in patients who have rubbed their eyes for a long time and in a very vigorous manner.
The keratoconus affects both eyes (frictions are often bilateral), but often there is a difference in the evolutionary stage between the right eye and the left eye, especially when the patient reaches keratoconus Rub more one eye than the other, or even that it Sleeps more systematically on one side than on the other (with extended support of the eye on the hand, the mattress, or the pillow), or on the belly, being forced to turn the head on one side.
The most reached side is very often the one that corresponds to the one that is in contact with the pillow. It is likely that the irritation caused by the support, contamination by bedding mites, the local increase in heat contribute to induce a sensation of discomfort, itching, leading to predominant eye rubbing on this side.
- Bilateral keratoconus more marked on the left side. The patient had been rubbing his eyes for several years, with a particularly violent technique on the left side, using his left forefinger as "crochet to better scratch and soothe the eye". The left cornea presented the biomicroscopic examination of the opacity. Contact Opacities characterize a highly evolved stage of keratoconus, and are always found in patients rubbing their eyes very vigorously. On the left, the corneal deformation is visible to the naked eye. The optical cuts by Scheimpflug camera (above) also show eloquently the corneal deformation, major on the left.