Page 48
Instruction Manual Easygraph
7.5.3 Contact Lens Fitting (optional)
The measurement of corneal geometry is of great
assistance to the user during contact lens fitting.
Without burdening the patient, it permits the insertion
of a contact lens and the inspection of the contact
lens fit to be simulated on the computer screen.
Contact lens fitting is started by calling the
"Lens
fitting"
(cf. 7.5 page 21) menu to the screen after the
examination.
The screen then shows two data areas:
Left: Data of cornea
Right: Data of contact lens
The area
Data of cornea
shows the table of
Eccentricity and the usual keratometric values:
Rh:
Horizontal radius of curvature in the center
Rv:
Vertical radius of curvature in the center
Rm:
Mean radius of curvature in the center
Astigm.:
Corneal astigmatism in the center
Axis:
Axis position of the flat meriadian
∅
Cor:
Diameter of the iris or the cornea
Ecc:
Mean eccentricity of the cornea
Fix.dif:
Fixation difference. Distance between pupil
center and center of topographic corneal
map.
The circle diagram at the right of the data shows the
position of the major meridians.
The curve of corneal eccentricity on the major
meridians is listed above the keratometer data in the
form of numbers from the inside to the outside.
A mean of eccentricity is calculated and displayed for
each peripheral angle. The central radii of the
individual meridians are displayed at the left column.
These data give the contact lens adjuster a good
idea of the shape of the cornea from the center to
the periphery.
Eccentricity values at 30° are used to calculate the
average eccentricity.
The contact lens to be fitted is selected by means of
the
“Contact Lens Fitting”
data fields (see next
page).