VisualTech (Shanghai) Corporation, commonly referred to as VisualTech, is a professional supplier of ophthalmic equipment, optometry and ophthalmic medical instruments, as well as optical lab equipment for the eyeglasses. The company is located in the bustling metropolis of Shanghai, China. VisualTech provides comprehensive global coverage, responding to the ever-changing needs of the times. The company has adapted to the transition of traditional offline exhibition models to convenient & efficient online shopping methods. Wherever the need arises, VisualTech is there to provide its superior products and exceptional customer service.
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Professional Team
VisualTech (Shanghai) Corporation, commonly referred to as VisualTech, is a professional supplier of ophthalmic equipment, optometry and ophthalmic medical instruments, as well as optical lab equipment for the eyeglasses.
Wide Range of Products
VisualTech offers a diverse range of products to the ophthalmic industry. Includes combined tables, autorefractor, digital lensmeter, phoropter, visual charts, trial lens sets, trial frames, ophthalmic slit lamp, non-contact tonometer, fundus camera, retinoscope & ophthalmoscope, perimeter, AB scan, Biometer, dry-eye analyzer etc.
Global Shipping
VisualTech provides comprehensive global coverage, responding to the ever-changing needs of the times. The company has adapted to the transition of traditional offline exhibition models to convenient & efficient online shopping methods. Wherever the need arises, VisualTech is there to provide its superior products and exceptional customer service.
Quality Control
VisualTech is committed to innovative self-development, constantly striving to lead the industry while adhering to the highest standards of quality. The company provides customers with high-quality, innovative and trustworthy services.
This optical lensometer is suitable for measurement testing departments, spectacle manufacturers, retail dealers of spectacles, hospital ophthalmology departments, and optical element factories.
This auto focimeter adopts Hartmann Wavefront Sensor with 145 multiple measurement points.
Digital lensmeter is designed to measure vertex powers and prismatic effects of spectacle and contact lenses, to orientate and mark uncut lenses, and to check the correct mounting of lenses in spectacle frames.
Automatic lensmeter is used for measuring single vison Lenses, bifocal(trifocal)lenses,progressive power lenses (PPL) and contact lenses(CL). The display unit utilizes a full-graphic LCD, displaying measured values of right-eye and left-eye Lenses at one time, and showing the alignment condition in the shape of cross.
The automatic lensmeter is a high precision digital optical equipment that accurately measures the distance and angle between two objects by using only two laser beams. This sophisticated laser technology helps to measure the distance between the object and the camera or any other lens system, which can be utilized for various purposes.
The Lenses That Can Be Calibrated by an Automatic Lensmeter
Automatic lensmeter can neutralize various types of lenses, including single-vision, bifocal, trifocal, progressive, prismatic, and rigid gas-permeable lenses. These lenses contain four primary types of powers: spherical, cylindrical, additions for near vision, and prismatic powers.
Single-vision lenses correct either spherical or astigmatic refractive errors. Unlike bifocal, trifocal, or progressive spectacles, they do not have additional reading power.
Multifocal lenses include various types of lenses, including bifocals, trifocals, and progressive lenses. They possess two or more optical powers that enhance both distance and near vision.
They are frequently prescribed for correcting myopic, hyperopic, and/or astigmatic refractive, and presbyopia. The additional plus spherical power for near vision is located in the lower portion of the spectacles. Bifocal lenses incorporate both a distance and near lens. Trifocal lenses exhibit three discernible sections on the lens with correction for distance, an intermediate distance, and near vision. Progressive lenses feature intermediate and add powers that gradually increase as the wearer looks down through the lens.
The gradient begins at the top portion of the glasses and reaches its maximum power at the bottom of the lens. The amount of added lens power varies from +0.50 to +3.50 diopters, depending on the amount of add required to see clearly at near. Progressive lenses have markings that indicate the manufacturer, the position of the distance power, the optical centers, and the near vision section. These markings are most visible when held up to a fluorescent light.
Prismatic lenses shift the observed image in the horizontal, vertical, or oblique meridian. They are frequently used to aid in ocular disorders such as strabismus, nystagmus, and diplopia, and/or asthenopia. Prisms consist of both a dioptric power and a base direction. Prisms can be prescribed alone or in combination with spherical correction in a spectacle prescription.
Three types of prisms can be present in glasses: incorporated, prism by decentration, and temporary Fresnel prisms. Incorporated prisms cannot be centered in the lensometer. When the lens is moved, the target will appear to jump from side to side. The higher the prismatic power, the more movement will be observed.
Incorporated prisms are ground into a lens. Prisms by decentration are relatively easier to be centered in the lensometer than incorporated prisms. They are apparent when the optical center of the lens is displaced in comparison to the pupillary center of the patient.
A rigid gas-permeable lens (RGP) is a type of contact lens made from a silicone material that is smaller than conventional soft contact lenses. Unlike soft lenses, which conform to the shape of cornea, RGP lenses maintain their shape and create a tear layer between the lens and the cornea.
This design allows for greater oxygen permeability compared to soft contact lenses. RGP lenses are used to correct visual abnormalities such as astigmatism and keratoconus. While they offer certain advantages over soft lenses, RGP lenses require a period of adaptation due to their rigidity.
What Does an Automatic Lensmeter Do
An automatic-lensometer measures the prescription of eyeglass lenses. It determines sphere, cylinder, axis, prism and distance between each optical center (pupillary distance). The lensometer is also used to accurately mount lenses into their frames as well as for orienting and marking lenses prior to cutting the lenses.
How Accurate Is the Automatic Lensmeter
Accuracy was found to be +/- 0.2 diopter in 95% of the lenses tested. The greatest error was 0.37 D. The automatic lensmeter correctly identified 125 of 128 lenses that were greater than 160 line pairs per millimeter (LP/mm) resolution and correctly identified nine lenses that had less than 100-LP/mm resolution. All other important optical aberrations were identified with the automatic lensmeter.
The greatest problem was the variation from company to company in terms of the calculated power in aqueous as determined from the back focal length in air.
How Do You Use Automatic Lensmeter Step by Step
Here are the steps:
1. Place glasses on platform and secure.
2. Turn axis and focus nobs so that the small lines are straight and focused.
Write down the number. This is your sphere.
3. Turn the focus nob until the fat lines become focused, and look at the new number on the focus nob. The difference from your prior sphere value is the cylinder value. If you changed from +1.00 to +4.00, then your cylinder is +3.00. If you changed from +1.00 to -1.50, then your cylinder is -2.50. In other words, the cylinder can be a positive or negative number, depending upon the direction you have to turn the focus nob.
4. Check the degrees on the axis dial. This is your cylinder axis.
Automatic Lensmeter Functions
The function of an automatic lensmeter is to determine the characteristics of a lens, including:
● Power
● Optical center location
● Major reference point location
● Prism power/direction
● Cylinder axis orientation
What Is the Most Common Error Using an Automatic Lensmeter
Failing to properly focus the eyepiece:
If the eyepiece is not focused to the examiner's eye, it can lead to inaccurate measurement of power.
Incorrectly positioning the lens:
If the lens is at the wrong angle or not properly centered on the reticle it can cause errors in both axis and power measurements.
Not compensating for calibration errors:
If the automatic lensmeter is not properly calibrated to read 0D with no lens, then the measured powers will be inaccurate by the same amount.
Misinterpreting principal vs spherocylindrical powers:
Automatic lensmeters measure these two principal powers, which then need to be converted to sphere, cylinder and axis. Failing to do this conversion correctly can lead to 90° axis errors.
Not verifying against the original prescription:
Checking the lenses against the lab invoice rather than the doctor's original rx can miss 90° axis errors made by the lab.
The eyepiece: It is mounted in a screw-type focusing mechanism. It plays an important role in the accuracy of your readings and is essential due to the different focusing ability of the individual eye of each user. It may be fitted with a rubber guard to prevent scratching of the user's own eyewear.
Chrome knurled sleeve: It is used to rotate the Reticle to orient prism base.
Prism compensating device knobb: It is used to read prism amounts greater than five prism diopters.
Lens holder handle: It is used to hold a lens in place against the aperture.
Marking device control: It is used to spot the lens at either the optical center or prism reference point (PRP).
Gimbal: It is a pivoting holder that holds the lens in place.
Ink pad: It holds the spotting ink.
Spectacle table lever: It is used to raise, or lower the level of the spectacle table.
Spectacle table: It is the resting place for the frame when neutralizing finished eyewear.
Power drum: It is a hand wheel with numbered scale readings between +20 and -20 D.
Locking lever: It is used to elevate or depress the position of the instrument for individual's height or posture.
Prism axis scale: It is used for orientation of prism axis
Prism compensating device: It is used to verify or layout large amounts of prism.
Prism diopter power scale: It displays prism amount.
On-off switch: It is the power switch.
Lens stop: It is the aperture against which the lens rests.
Cylinder axis wheel: It is used to orient or neutralize cylinder axis.
Filter lever: It is used to engage or remove green filter.
Lamp access cover: It provides access to change the lensmeter bulb.
How Do You Calibrate an Automatic Lensmeter
Periodically ensure that the power calibration of your lensmeter is accurate by following these steps:
● Turn on the lensmeter.
● Turn the eyepiece ring so that the reticule appears in focus.
● Turn the power wheel into the plus, then slowly decrease the power until the lensmeter target is sharply focused. Do not oscillate the wheel back and forth to find the best focus. The power wheel should read zero if the instrument is properly calibrated.
● If the power wheel does not read zero, re-focus the eyepiece and re-check the calibration. If the power wheel still does not read zero, the error must be compensated for in all future measurements made with the lensmeter, or the lensmeter needs maintenance. (Note: subtract the calibration error from the power measurement to compensate for calibration errors.)
An automatic lensmeter is an instrument used to verify the prescription of eyeglasses or spectacles. Many automatic lensmeters can also verify the power of contact lenses with the addition of a special lens support.
The values obtained from an automatic lensmeter are the values specified on the patient's eyeglass prescription: sphere, cylinder, axis, add, and in some cases, prism. It is commonly used prior to an eye examination to obtain the last prescription the patient was given, in order to expedite the examination.
In one commonly used type of automatic lensmeter the target seen through the eyepiece consists of a set of three wide lines with wide spacing between them and another set of three narrow lines with smaller spacing between them. These two sets of lines intersect at right angles. The closely spaced lines represent the sphere component of lens power and the thicker, widely spaced lines represent the cylinder power. In the case of a spherical lens, all of the lines of the target will focus at the same time, while in the case of a sphero-cylindrical lens, the lines will focus separately at different power drum readings (see illustration).
In another type of automatic lensmeter, a series of light dots forming a circle is used as a target instead of the two sets of parallel lines described earlier. If a spherical lens is measured, the circle remains a circle and the power drum is adjusted to obtain a sharp image of the dots. For sphero-cylindrical lenses the dots, when focused, will display a sharp ellipse. The major and minor axes of the ellipse can be read on the scale provided in the instrument.
The target is imaged through a lens. The eyeglass lens under test is placed at the rear focal point of this lens. Light emerging from the spectacle lens enters the eyepiece which contains a reticle. The reticle is a permanently etched series of concentric rings used to measure and locate the prism base direction, and also contains orientation lines for each lens meridian and a protractor scale.
For measuring the power of the lens, the power drum is turned until a clear and sharp image of the target is seen through the eyepiece. The power (in diopters) can be read on the scale on the wheel. For measuring the focal power of cylindrical and sphero-cylindrical lenses that have different powers in different meridians, the optics of the equipment can be rotated by turning the axis wheel. The angular position can be read on the circular scale of the axis wheel.
The eyeglass lens to be tested should be placed on the lens stop so that the outside of the lens is facing the eyepiece and the side of the lens that sits closest to the user's eye is facing the instrument's light source. Before using the instrument, you should look through the eyepiece. The reticle should be in focus. If it is not, adjust the eyepiece until it is sharply focused.
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Specifications:
|
Automatic Lensmeter Basic Measurement |
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Sphere: |
-25.00D - +25.00D (0.01/0.12/0.25D steps) |
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Cylinder: |
-10.00D - +10.00D (0.01/0.12/0.25D steps) |
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Axis: |
0 - 180º (1º steps) |
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ADD: |
-10.00D - +10.00D (0.01/0.12/0.25D steps) |
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Prism Degree: |
0△-15△ (0.01/0.12/0.25△steps) |
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Measurement Mode |
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Cylinder Form: |
+, -, mixed |
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Prism: |
X-Y, P-B |
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Contact lens: |
Hard or soft |
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Measuring Mode: |
Single/progressive/auto recognition |
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Others |
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Diameter of Lens: |
Ф 20 -Ф100mm |
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PD: |
0mm - 80mm |
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Speed of measurement: |
0.1s |
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Display: |
TFT LCD (5.7") |
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Printer: |
Thermal Printer |
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Dimension: |
192(L) * 208(W) * 416 (H) MM |
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Weight: |
5.5 KGS |
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Power: |
AC100~240V 50~60HZ |
