Tomey TMS-5, Инструкция по эксплуатации

Страница: 181 / 216

4-1
4. TECHNICAL INFORMATION
4.1 Corneal refractive index used to calculate refractive
power distribution
Although the corneal refractive index is originally n = 1.376,
this instrument uses a corneal conversion refractive index
of n = 1.3375, which is used in many corneal topography
and keratometers.
The total refractive index of the cornea is determined
by the sum of the refractive powers of the front and rear
sides. However, since this instrument measures the radius
of corneal curvature of the front surface of the cornea, the
refractive power of the entire cornea cannot be calculated.
Therefore, this cornea equivalent refractive index is used
clinically to analogize the total refractive power of the
cornea.
4.2 Calculating the keratometer simulation values
SimK, Kf, Ks, MinK, AvgK, CYL
This instrument assumes a radius of corneal curvature of
8 mm as the reference spherical surface, and displays the
refractive power of a point at a radius of 1.5 mm (
f 3) from
the center of analysis as the keratosimulation value.
SimK averages the measurement values of 3 rings around
the aforementioned point on the measurement meridian,
and calculates the meridian with the maximum refractive
power on the cornea and its value [Ks], and displays the
average value of a meridian orthogonal to the meridian
with the maximum refractive power, just like a conventional
keratometer [Kf]. MinK represents the meridian with the
minimum refractive power, as well as its value used for
calculating SimK.
AvgK (AveK in case of TMS-4) represents the average of
SimK. CYL shows the difference of the refractive power of
Kf and Ks as the components of a corneal cylinder.