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4. REFERENCE TECHNICAL INFORMA-
TION
Corneal refractive index used for calculating corneal refractive power
The corneal refractive index is primarily n=1.376: however, n=1.3375,
which is converted refractive index used for many types of keratometer
measurement equipment, is used for this instrument.
The total corneal refractive index is determined by the sum of anterior
and posterior refractive powers. Since this instrument (RC-5000) mea-
sures the curvature of the corneal anterior part, the refractive power of the
whole cornea cannot be obtained.
For this reason, this conversion refractive index is clinically used to as-
sume the total refractive power of cornea.
Calculation for Residual Astigmatism
When put hard contact lens at Patient's eye, the tear fluid layer that is
form between cornea with hard contact lens become lens and correct cor-
nea astigmatism. This astigmatism degree of tear fluid lens is able to cal-
culate by supposing keratometer measurement data and back side curve
of hard contact lens as spherical.
This instrument calculate as Residual Astigmatism that can not corrected
by tear fluid lens against toal astigmatism that is measured by refractome-
ter measurement.
4 REFERENCE TECHNICAL INFORMATION
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