Nidek Medical LM-7, Operator'S Manual

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3. OPERATING PROCEDURE : UV Transmittance Measurement
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Comparative measurement of UV transmittance
By measuring another lens, UV transmittance can be com-
pared.
1)
After replacing the lens and bringing the optical cen-
ter onto the nosepiece, press the compare measure-
ment button .
The measured results of the two lenses are displayed
on the UV comparison screen simultaneously.
• The left side of the screen shows the measured result of
the first lens, and the right side shows that of the suc-
ceeding lens.
• Perform measurement while checking the target in the
circle at the bottom of the screen. When the target
becomes (within 4 ∆ ), measurement can be per-
formed more precisely.
2)
Press the exit button to return to the mea-
surement screen.
♦
Harmful effects of ultraviolet rays on eyes
Ultraviolet rays included in sunlight are roughly classified into three types.
This device measures UV-A transmittance.
UV cut-off blocks ultraviolet rays with wavelengths shorter than a certain wavelength. Measure-
ment of UV-A transmittance is effective to assess protection.
• Pressing the retry button or compare measurement button repeatedly renews each mea-
sured result.
Classification Effect
UV-C
280 nm or less
• Absorbed by the ozone layer and hardly reaches the ground.
UV-B
280 to 320 nm
• Absorbed in cornea causing corneal injury such as keratitis.
• Causes sunburn and skin becomes red.
• Causes skin irritation and skin damage such as stains, freckles, and wrinkles.
UV-A
320 to 380 nm
• Accumulated in the crystalline lens resulting in cataract.
• Skin becomes dark after sunburn.
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