Lensometers

Detailed instumentaion and use of manual Lensometer and just a outline of automated lensometer.

I have used the picture of manual lensometer with out the parts describtion because i have explained orally by showing the picture..

Hope u all like it and may help you in learning better. :)

1. LENSOMETERS By :- M.A.Rasheed, Id:-12IMMO06, I.M.Sc in Optometry & Vision Sciences, School of Medical Sciences, University of Hyderabad.

2. LENSOMETER :- It is a device designed to measure the refractive power prescription of a unknown lens . (spherical, cylindrical with axis and also the optical center) Types :- Manual & Automated URL:- GOOGLE images/ lensometers /html

3. Manual Lensometer :- Manual lensometer gives the accurate power of a lens and were used in optical industries. A manual lensometer is portable and can be carried anywhere But a person needs to have a better idea to measure the power of a lens. (specially in case of a toric lens) Automated Lensometer :- It is a fully automatic well programmed device mostly used in clinics. It is easy and faster and can print prescription. It is less accurate when compared to manual lensometer .

4. Manual Lensometer URL:- GOOGLE images/ lensometers /html

5. Steps to n eutralize spectacle lenses in manual lensometer Calibration :- A djusting the device to perform smoothly in order to get accurate power of the lenses. Notes :- Eye piece should be focused manually. Power drum should level zero. All the knobs should be placed rightly and the device should be neat and clean to avoid errors. URL :- GOOGLE images/ lensometers /html

6. Adjustment of Eye piece:- It is very important to focus the eye piece so that the observer’s eye is relaxed and to avoid errors . In adjusting the eye piece the blurred black protractor is focused . At first the eye piece is rotated completely Anti-clock wise, the protractor views blurred . Then slowly rotate the eye piece clock wise and stop at once where it is sharp and clear . Now the eye piece is set and focused . Blurred protractor Focused protractor

7. Placing the spectacles lens on the device with its front surface facing towards the eye piece. Placing the spectacle lenses on the device. There are 2 knobs on the lensometer :- Lens stop (holds the lens/frame in place ) Frame leveling knob (makes sure that the frame is leveled and helps in accurate axis measurement )

8. Target It is green in colour and appears when the device Is switch on. It shows the position of the optical center of the lens. There is a ring of round dots at the centre of the target. This represents the power orientation of the lens as it rotates with the lens rotation These round dots become small lines oriented in one direction in case of a toric lens

9. • Move the lens such that the target is exactly at the centre. •Rotate the power drum until target is clear and sharp (all the dots at the center should be separate & sharp ) •Stop rotating the power drum when the target is sharp for the first time. •Always count the upper mark on the power scale for accuracy of the spherical power of the lens. Analyzing the Spherical lenses

10. Analyzing the Cylindrical lens The process of Neutralizing a toric lens when compared to spherical lens is completely a different concept. However , with the help of few tips we will be able to measure the lens power very fast and accurately. The key and the most important thing to remember is the central orientation of the dots.

11. Process of toric lens neutralization :- • Step 1: Move the lens so that the target is at the center of the protractor. •Step 2: Rotate the power drum so that the central lines (oriented in one direction) are sharp. •Step 3: Rotate the axis wheel so that one meridian of the target is parallel to the orientation of the central lines. Note that only one meridian of the target will be sharp •Step 4: Rotate the power drum so that the opposite meridian in the target is sharp. Note that the central lines will change in direction and will be oriented in the opposite direction.

12. Step 1:- • Move the lens so that the target is at the centre of the protractor. •This gives the optical centre location.

13. Step 2:- •Rotate the power drum so that the central lines (oriented in one direction) are sharp

14. Step 3 :- Rotate the axis wheel so that one meridian of the target is parallel to the orientation of the central lines. Note that only one meridian of the target will be sharp. As the 180° meridian is sharp in this picture, we will write the power and the axis as 180° Ex : ---DC X 180s°

15. Rotate the power drum so that the opposite meridian in the target is sharp. Note that the central lines will change in direction and will be oriented in the opposite direction. As the 90° meridian is sharp in this picture , we will write the power and the axis as 90° Ex : ----DC X 90 ° Writing the power • As the Lensometer gives the readings of a toric lens power in 2 cylinder format, we need to transpose the power and write in sphero – cylindrical format • The power which we got in the example shall be written as: -----DS/----DC X 180 °

16. Important points to remember :- Always focus the eyepiece before using the instrument Concentrate on the central circular orientation of dots (especially in case of toric lenses) One meridian of the target should always be parallel to the orientation of central small lines (in toric lens) Each dot at the center will not be round, instead they will be small lines oriented in one particular meridian Except the protractor, everything will be blur when a lens is placed The target moves with the movement of the lens Instrument should not be used more on battery

17. Automated Lensometer

18. Automated Lensometer offers a fast and easy way to accurately measure all lenses including: Single Vision, Bi-focal, Progressive, and Prism . Automatic measurements can be taken quickly by simply positioning the lens on the lens table. Progressive lenses are recognized and measured automatically, with the rate of addition and diopter change graphically displayed . Features:- UV transmittance measurement Pupillary distance measurement Measurement of soft and hard contact lenses Space saving vertical orientation Full color tilt-screen for easy viewing while standing or seated Easily accessible menu to customize your settings Data output options including a built-in printer and USB ports Can be configured to interface with EMR systems

19. References URL:- GOOGLE images/ lensometers /html Few pictures are taken from lensometry manual by Mr. Sunny Mannava (HCU). THANK YOU “Because e yes speaks a lot”