This document provides information on how to use a lensmeter and keratometer to measure eyeglass lenses and corneal curvature. It describes the parts and functions of a lensmeter, including how to focus the eyepiece, position lenses, and measure sphere, cylinder, and prism powers. It also outlines the Javal-Schiotz and von Helmholtz methods used in keratometry to measure corneal curvature based on the shadow cast by the cornea. Step-by-step instructions are provided for using both devices to obtain measurements of patients' lenses and corneas.

1. Lensmeter and
Keratometer
Residen Pengayaan

2. Lensmeter
Is an instrument used to measure the power of patient’s present spectacle lenses.

3. ◉ Spherical and cylindrical
power
◉ Cylindrical axis
◉ Presence and orientation
of prism

4. Parts of lensmeter
•Eyepiece: to focusing the instrument
according to examiner’s eye
•Lens stop: where the measured lens to be
placed
•Lens holder/gimbal: to support the lens
•Spectacle table: to support the lens
•Spectacle table lever: to adjusting the
spectacle table
•Power drum: for reading the refractive
power of the lens
•Cylindrical axis wheel: for reading the axis
of cylindrical lens

5. Part of lensmeter
Triple line
Single line

6. Automatic :
-Easy and printable
-Less accurate compared to manual
lensmeter
Manual :
-Manual lensmeter gives the accurate power
of a lens and were used in optical industries
-Portable and easy to carry

7. Focusing the eye piece
Positioning the eyeglasses
Measuring sphere & cyclinder power

8. Measuring
sphere &
cylinder
power
1. Turn the power drum to read high minus ( about – 10.00D)
2. Bring the closely spaced mires (single lines) into sharp focus by rotating the
powerdrum counterclockwise while at the same time rotating the cylinder
wheel to straighten the single lines where they cross the widely spaced
perpendicular set of mires (triple lines)
3. If single line & triple lines  focus  the lens is sphere
4. If only the single line focus  spherocylinder. Record the power drum
reading at this point as the power of the sphere
5. Calculate the difference between the first powerdrum reading or the 2nd for
focused triple lines.
6. Read the axis of the cylinder from the cylinder axis wheel

11. Keratometer

12. Principle Keratometer

14. Keratometer
Metode Javal-Schiotz
Metode Van helmholtzs
Automated keratometer

15. Von Helmholtz Javal-Schiotz

16. 2 methods • 1 methods

18. Focusing the mires :
Turn the focusing knob

21. Rotate the AXIS

23. Thankyou

24. Lensmeter and
Keratometer
Residen Pengayaan

25. Measuring
bifocal
power
After measuring the sphere and cylinder distance portion of a
bifocal eyeglass lens, center the bifocal add at the bottom of the
lens in lensmeter gimbal ( the ring-like frame) and refocus on the
triple lines.
The difference between the distance reading of the triple line
focus and the new triple line focus is the add, or bifocal power.
If the distance portion of the eyeglass lens is a sphere, just refocus
the bifocal segment and calculate the algebraic difference between
the power in the top segment and the power in the bifocal
For a trifocal lens, follow the same procedure as for the bifocal
segment to measure the trifocal segment directly. Customarily at
trifocal is one half the power of the bifocal.

26. Measuring
prism
power
and
orientation
Prism power in a spectacle lens generally is revealed when the lensmeter
mires cannot be centered in the central portion of the lensmeter target
With a nonpermanent marker, mark the position on the lens through which
the patient is viewing while he is looking straight ahead. Center this mark in
the lensmeter target.
Count the number of black concentric circles from the central cross of the
lensmeter target to the center of the vertical and/or horizontal crossed mires.
Each circle represents 1 prism diopter.
Record the direction of the thick portion (base) of the prism by determining
the direction of the displacement of the mires. For example, if the mires are
displaced upward, the prism base is base up; downward displacement
indicates base-down prism; displacement toward the nose, base-in prism;
and displacement toward the temples, base-out prism.

27. Step by step :
Ask the patient to put off the contact lens or the spectacles
Position the patient in front of the head unit of keratometer, chin and head
on it’s place
Check each eye separatedly, with covering unexamined eye
Put the examination eyes on the eyepiece, look through the eyepiece and
examine the shadow from the cornea ( round shape)
Adjust the focus to sharpen the images

28. Step by step
Adjust the vertical prism until the round shape separated vertically in line
with first round shape ( following the minus sign)
Adjust the horizontal prism to divide the round shape horizontally, in line
with the first round shape ( following the plus sign)
Read the measurements of corneal curvature and corneal power in
keratometer
In astigmatism cornea, plus sign or minus sign in round shape is
misaligned with the sign in the first round shape.

29. Step by step
Turn the keratometer in optical axis to make third of round
shape align
Measure the astigmatism of cornea
Do the same step for the other eye