Keratoconus Case Studies

(2) Orbscan:
(A) Screening for subclinical keratoconus: The data depicted and displayed by the Orbscan system have added a very important value to the diagnostic tools that may detect early keratoconus. The early diagnosis of subtle changes is critical for the evaluation candidates for laser vision correction, as well as providing early diagnosis and sensitive follow up of progression in the era of procedures designated to stabilize the corneal shape such as cross-linking. Being the first widely spread “catch-all” corneal topographer that provides posterior corneal surface mapping, Orbscan introduced a new era in refractive surgery and keratoconus diagnosis. Thus, the topography of anterior corneal surface became insufficient in

An additional keratoconus-related parameter provided in the stat box is pachymetry of the thinnest point (displayed as: “Thinnest”) and its distance (mm) from the visual axis. Although there is no strict clearcut of corneal thickness that specifically characterizes keratoconus, the color code will define by warm colors corneas of 500 μm or less as suspicious. If the thinnest point is located on the right to the vertical line, the first coordinate (x-axis) will be positive (Liu et al., 1999). If it is located to the left – the first coordinate will be negative; if the thinnest point is located above the horizontal line, the second coordinate (y-axis) will be positive, otherwise it will be negative. The location of the thinnest point of the cornea may be helpful in the diagnosis of keratoconus: in 70% of normal individuals it is located in the inferotemporal quadrant at an average distance of 0.90 mm (SD 0.51) from visual axis (Liu et al., 1999), thus any readings outside of 2 standard deviations from this value (i.e. 1.92 mm) may be considered as