Lensometry

Lensometry: The procedure for measuring the prescription of eyeglass lenses using an instrument called the lensometer. Simply put: Determining the prescription in a lens.

Lensometry Lensometers verify the overall optical quality in lenses and the prescription by checking the Spherical and Cylindrical Power Axis Prism Optical Centers of a Lens

Lensometry The lensometer is helpful for finding the prescription in patient’s existing eyeglass lenses or verifying the power in a lens by the lab before glasses are dispensed.

Manual Lensometer Automatic lensometer Lensometry There are two kinds of lensometers: Manual Lensometer Automatic lensometer

Lensometry There are two kinds of lensometers: The manual lensometer is an instrument that an individual must have a thorough understanding of optical principles and lensometry before using efficiently. The automatic lensometer requires very little knowledge, skill, or ability to understand optics or lensometry.

Lensometry If there is ever a question about the center power, axis, or prism of a lens, then the manual lensometer must be the final authority on the lens.

Lensometry In general, it is a simple rule that before placing a lens on any lensometer, look at the lens visually 16 inches from your face and move the lens around to see if there is a bifocal in the lens. Progressive lenses are often hard to see; you should be able to recognize this before reading the lens power, otherwise a lensometer reading may be off.

Lensometry Something to remember: Optometrists measure lenses in minus cylinder, ophthalmologists measure lenses in plus cylinder.

Manual Lensometer

Manual Lensometer The manual lensometer is an instrument used for measuring the prescription in an optical lens which requires a skilled individual to operate by hand. The manual lensometer is the most accurate way of measuring the prescription of a lens.

Manual Lensometer This instrument requires an individual to have a thorough understanding of optics, especially lensometry, before operating.

Manual Lensometer [1] Focus the lensometer eyepiece. The first three steps that must be performed on an automatic lensometer (regardless of manufacturer) are: [1] Focus the lensometer eyepiece. If the eyepiece is not focused prior to using the lensometer, the reading could be flawed. The lensometer should be focused while there is NO LENS IN THE LENSOMETER.

Manual Lensometer The first three steps that must be performed on an automatic lensometer (regardless of manufacturer) are: [2] Position the lens to be measured on the specific table or platform of the lensometer. Start with the power wheel at a very high plus power. Turn the power wheel to reduce plus power, while turning the axis wheel, until a set of mire stripes (the perpendicular crossed lines) come into focus and the bars appear straight and unbroken. Refine the axis and power wheels until the set of stripes is very sharply focused and unbroken.

Manual Lensometer [3] Measure the sphere power. The first three steps that must be performed on an automatic lensometer (regardless of manufacturer) are: [3] Measure the sphere power. Measure the cylinder, either plus or minus, and axis if they are present also.

Manual Lensometer [1] Focus the lensometer eyepiece. The first three steps that must be performed on an automatic lensometer (regardless of manufacturer) are: [1] Focus the lensometer eyepiece. [2] Position the lens to be measured on the specific table or platform of the lensometer. [3] Measure the sphere power.

Automatic Lensometer

Automatic Lensometer The automatic lensometer, or lens analyzer, is a device for automatically measuring the lens power (sphere, cylinder, and axis) for single, multifocal, and progressive lens.

Automatic Lensometer The automatic lensometer is a gross screening device and is not as accurate as a manual lensometer. It is also difficult to give accurate prism measurements on an automatic lensometer.

Automatic Lensometer The automatic lensometer is generally used by clinic technicians or by the optical to understand the patient’s situation better.

must be the final authority on the lens. Automatic Lensometer If there is ever a question about the center power, axis, or prism of a lens, then the manual lensometer must be the final authority on the lens.

Automatic Lensometer The information provided by the automatic lensometer is helpful in several ways: It allows the doctor to know if the patient’s current prescription (Rx) is correct. It allows the doctor to quickly find out what Rx a new patient has. It allows the doctor to diagnosis the patient’s situation better. It is quick. It also measures the Rx in contact lens.

Automatic Lensometer Instructions [A] Setting Up the Automatic Lensometer [B] Instructions for Single Vision Lens with or without a Lined Bifocal [C] Instructions for Progressive (No-Lined Bifocal) Lens

Automatic Lensometer Instructions [A] Setting Up the Automatic Lensometer [B] Instructions for Single Vision Lens with or without a Lined Bifocal [C] Instructions for Progressive (No-Lined Bifocal) Lens

Automatic Lensometer Instructions [A] Setting Up the Automatic Lensometer Turn the automatic lensometer on. Make sure mode is in minus cylinder. Optometrists measure lenses in minus cylinder, ophthalmologists measure lenses in plus cylinder.

Automatic Lensometer Instructions [A] Setting Up the Automatic Lensometer Turn the automatic lensometer on. Make sure mode is in minus cylinder. Optometrists measure lenses in minus cylinder, ophthalmologists measure lenses in plus cylinder.

Automatic Lensometer Instructions [A] Setting Up the Automatic Lensometer Verify the power to round off to the nearest 0.25 The unit used to measure power of glasses is called a diopter. Think of it like dividing a dollar into four quarters – you have a quarter, a half dollar, seventy-five cents, and then a dollar. This is the same principle for measuring lens powers and for writing them down. For example: 0.25, 0.50, 0.75, and 1.00. There is plus power and minus (negative) power. F.Y.I. – iZon lenses round off to the nearest 0.12 power (instead of 0.25).

Automatic Lensometer Instructions [A] Setting Up the Automatic Lensometer Verify the power to round off to the nearest 0.25 The unit used to measure power of glasses is called a diopter. Think of it like dividing a dollar into four quarters – you have a quarter, a half dollar, seventy-five cents, and then a dollar. This is the same principle for measuring lens powers and for writing them down. For example: 0.25, 0.50, 0.75, and 1.00. There is plus power and minus (negative) power. F.Y.I. – iZon lenses round off to the nearest 0.12 power (instead of 0.25).

Automatic Lensometer Instructions [A] Setting Up the Automatic Lensometer Ask the patient for his or her glasses. Tell them: “I will measure your present lens prescription. Dr. needs this information to identify the amount of change in your lens prescription. This computer reads your lens power automatically; it is the most accurate way to measure a lens prescription.”

Automatic Lensometer Instructions [A] Setting Up the Automatic Lensometer When measuring on the auto lensometer, watch for progressive or invisible bifocals. Before placing a lens on the lensometer, look at the lens visually 16 inches from your face and move the lens around to see if there is a bifocal in the lens.

Automatic Lensometer Instructions [A] Setting Up the Automatic Lensometer [B] Instructions for Single Vision Lens with or without a Lined Bifocal [C] Instructions for Progressive (No-Lined Bifocal) Lens

Automatic Lensometer Instructions [A] Setting Up the Automatic Lensometer [B] Instructions for Single Vision Lens with or without a Lined Bifocal [C] Instructions for Progressive (No-Lined Bifocal) Lens

Automatic Lensometer Instructions [B] Instructions for Single Vision Lens with or without a Lined Bifocal If the Bridge Adjustment Holder is not on the left side of the instrument, slide it to the left so that the right lens can be read first.

Automatic Lensometer Instructions [B] Instructions for Single Vision Lens with or without a Lined Bifocal Place the bridge of the glasses into the Bridge Adjustment Holder.

Automatic Lensometer Instructions [B] Instructions for Single Vision Lens with or without a Lined Bifocal Place right lens upon Laser Light. Level glasses and adjust lens so that the screen lines up to read the power on the lens. The instrument will guide the reading as you center the “+” sign in the grid.

Automatic Lensometer Instructions [B] Instructions for Single Vision Lens with or without a Lined Bifocal The power is best read in the center of a lens for a single vision lens. If a lens has a lined bifocal, the power for the distance is read in the top middle of the lens and the power for the bifocal is read in the middle of the bifocal – or the bottom half of the lens. Two readings must be found for a bifocal lens.

Automatic Lensometer Instructions [B] Instructions for Single Vision Lens with or without a Lined Bifocal When you align the “+” sign and grid, lower the Lens Holder (or clamp) down onto the lens (to lower the Lens Holder push up on the bar and it will come down). Be careful not to scratch the lens.

Automatic Lensometer Instructions [B] Instructions for Single Vision Lens with or without a Lined Bifocal Get accurate readings of axis. Compare reading to the Rx listed in the record.

Automatic Lensometer Instructions [B] Instructions for Single Vision Lens with or without a Lined Bifocal If the glasses have a lined bifocal, two readings are required – one for distance vision (the top half of the glasses) and one for near vision (the bifocal located at the bottom half of the lens). After getting the distance vision reading, move the lens on the Laser Light to the middle of the lined bifocal area – you must lift the Lens Holder to move the lens over the Laser Light. Level the glasses and adjust the lens so that the screen lines up to read the power of the lens. Get an accurate reading of the axis.

Automatic Lensometer Instructions [B] Instructions for Single Vision Lens with or without a Lined Bifocal At the end of a reading, lift the Lens Holder.* Slide the Bridge Adjustment Holder to the right side of the auto lensometer to get a reading for the left lens. *Some instruments are designed that the glasses do not need to come off the Bridge Adjustment Holder.

Automatic Lensometer Instructions [B] Instructions for Single Vision Lens with or without a Lined Bifocal Repeat steps 2 through 5 above to get the readings for the left lens. Once all readings are gathered, place the information in the patient’s record.

Automatic Lensometer Instructions [A] Setting Up the Automatic Lensometer [B] Instructions for Single Vision Lens with or without a Lined Bifocal [C] Instructions for Progressive (No-Lined Bifocal) Lens

Automatic Lensometer Instructions [A] Setting Up the Automatic Lensometer [B] Instructions for Single Vision Lens with or without a Lined Bifocal [C] Instructions for Progressive (No-Lined Bifocal) Lens

Automatic Lensometer Instructions [C] Instructions for Progressive (No-Lined Bifocal) Lens After asking the patient for his or her glasses, press the button on the automatic lensometer that allows you to measure a progressive (no-line bifocal) lens. Two readings are made for a progressive lens – one for the far vision and one for the near (bifocal) vision.

Automatic Lensometer Instructions [C] Instructions for Progressive (No-Lined Bifocal) Lens If the Bridge Adjustment Holder is not on the left side of the instrument, slide it to the left so that the right lens can be read first. Place the bridge of the glasses into the Bridge Adjustment Holder. Place right lens upon Laser Light.

Automatic Lensometer Instructions [C] Instructions for Progressive (No-Lined Bifocal) Lens Level glasses and adjust the lens so that the screen lines up to read the power on the lens. The instrument will guide the reading as you center the “+” sign in the grid. The power for far distance is found in the top half of the lens; power is best read in the center of the top half. The power for the bifocal is read in the middle of the bottom half of the lens.

Automatic Lensometer Instructions [C] Instructions for Progressive (No-Lined Bifocal) Lens When you align “+” sign and grid, lower the Lens Holder (or clamp) down onto the lens (to lower the Lens Holder push up on the bar and it will come down). Be careful not to scratch the lens. Get accurate readings of axis. Compare reading to the Rx listed in the record.

Automatic Lensometer Instructions [C] Instructions for Progressive (No-Lined Bifocal) Lens For the progressive bifocal reading, lift the Lens Holder up to move the glasses over the Laser Light. Move the lens on the Laser Light to the middle of the bottom half of the glasses – the instrument should guide you. Level the glasses and adjust the lens so that the screen lines up to read the power of the lens. Lower the Lens Holder. Get an accurate reading of the axis.

Automatic Lensometer Instructions [C] Instructions for Progressive (No-Lined Bifocal) Lens At the end of a reading, lift the Lens Holder.* Slide the Bridge Adjustment Holder to the right side of the auto lensometer to get a reading for the left lens. *Some instruments are designed that the glasses do not need to come off the Bridge Adjustment Holder.

Automatic Lensometer Instructions [C] Instructions for Progressive (No-Lined Bifocal) Lens Repeat steps 3 through 8 above to get the readings for the left lens. Once all readings are gathered, place the information in the patient’s record.