Essilor Instruments VISION-R 700, User Manual

Page: 54 / 128

> Start the test again until the patient sees equal clearness between the horizontal and vertical lines or
a greater clearness for the vertical ones.
In the event of preferred inversion between the horizontal and vertical lines between two sphere steps,
retain the last values:
vertical
for a patient
with myopia
horizontal
for a patient
with hypermetropia
Notes
To avoid the disturbing effects of accommodation, it is possible to blur the patient (with a convex power)
until you obtain the preference for the vertical lines and to then clear up it until you achieve a balance
between the horizontal and vertical lines.
The test of the fixed cross cylinders supposes an exact correction of the astigmatism of the eye. The result
can be distorted if a direct astigmatism (cylinder axis further from 0°) or the opposite (cylinder axis
further from 90°) is over or under-corrected.
At the end of the test, the horizontal and vertical lines are slightly fuzzy (because the patient looks at
them through a cylinder of 1.00 D). The important thing is that the blurring is identical on the horizontal
and vertical lines.
(*)
This information corresponds to the phoropter default settings. The
sphere variation step is by default
0.25 D but can be adjusted in settings.
Reserved cross cylinders
Objective
Determine the value of the patient's cylindrical correction:
Axis,
In power,
In far vision,
In single-eyed vision (right eye or left eye).
Historically, the reserved cross cylinders test was performed using a lens made up of a positive cylinder
and a negative cylinder of the same powers and perpendicular portions between them. This lens was
mounted on a shaft and allowed the position of positive and negative cylinders to be manually reversed
by turning the lens over itself.
Unlike traditional manual and automated phoropters, there is no reversal in the Vision-R
TM
700 or
"changing" lens manuals. The cross cylinder move positions instantaneously. It is determined by a
calculation which, in combination with the correction in place, is directly generated by the optical module.
The patient sees a change occurring instantly and without interruption and thus perceives differences
more easily.
Principle
The principle of the test is to combine the astigmatism of the lens with the uncorrected residual cylinder value of
the eye (the one resulting from the combination of the eye’s astigmatism and the correction in place).
If the astigmatism is properly corrected, the patient does not perceive any difference between the
positions of the cross cylinder. They are seen as equally blurred.
If the astigmatism is not perfectly corrected, the patient perceives a blurring difference between the
different positions of the cross cylinder.
The reversed cross cylinder test takes place in three stages:
1. Cylinder axis search
2. Cylinder power search
3. Sphere power adjustment (based on the cylinder value)
- equality of darkness between the horizontal and vertical ones
retain this sphere value. >
U
SER MANUAL
> P
ERFORMANCE OF TESTS DURING A REFRACTION EXAMINATION
Vision-R 700 - Essilor automatic phoropter > V1 - 09-2020 54