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A dioptrimeter or lensmeter is a medical device, without which no laboratory, optical salon or ophthalmologist’s office can function. The device measures the refractive power of spectacle / contact lenses, determines the degree of surface protection from ultraviolet radiation and the distance between the centers of the lenses in the finished glasses. What you need to know about the device, what are the types of dioptrimeter and how to use it correctly?
General characteristics of the device
A dioptrimeter is a device for evaluating lens quality parameters. It measures optical power, reveals the position of the main meridians of astigmatic glass, the degree of protection from ultraviolet rays, and so on. A number of characteristics obtained will help you choose the best option for lenses, based on an individual prescription. In essence, the lens meter is a centered telescopic optical system. It is equipped with a rotating target, a standard optical lens and a powerful light source.
What exactly does a lensmeter show? The degree of refraction of the lens glass. Based on the result, the specialist can understand which particular problems of the patient can be solved by this or that lens. For example, to neutralize myopia, farsightedness, help focus and detail the image. The doctor compares the prescription with the results of the study and selects glasses that will help to cope with the anomaly as efficiently as possible.
The selection of lenses can be carried out both at the appointment with an ophthalmologist, and in the nearest optics, which has an office for checking vision.
The design of the lensmeter includes the following functional parts: a microscope, a telescope, a collimator, mechanisms for working with optical glass and a stand on which the lens is mounted. The device itself is located on the support bar. It can be a movable guide platform or a kind of table. The size and functionality of the support bar depends on the size and cost of the diopter.
Collimator – a device for obtaining parallel beams of light rays. An object or a concave mirror is located in it, in the plane of which the lens under study is placed.
Varieties of the dioptremeter
The main parameter for classification is the type of management. There are only two types of dioptrimeter – analog or manual and automatic or digital. Using an analog device, a healthcare professional can measure the optical characteristics of the glasses to be released. All measurements, preparation of materials and the apparatus itself are carried out manually, which takes a lot of time. The first hand-held lensmeters could not be used in large optics, through which dozens and hundreds of orders passed. But improved models allow you to process information with greater accuracy and speed.
Digital devices were introduced into ophthalmological practice in 1985. All measurements are carried out automatically after a given command. The processed information is displayed on the screen for review by a specialist. It can be saved on external media and shared with colleagues/patients. An automatic instrument can measure values that a manual lensmeter cannot, eliminate errors, and can analyze the full range of features in a short amount of time. The only drawback of digital technology is the high cost.
Instructions for using the handheld device
The automatic diopter works after a few button presses, which do not require separate consideration. Below is a general algorithm for working with a manual device, which may vary depending on the modification.
The first step is to install the lens on the work surface. The next step is to adjust the height and angle of the eyepiece. It is adjusted until the image in the lensmeter becomes clear. Once the specialist has set the desired viewing angle, he slowly turns the device counterclockwise to focus the eyepiece. This is followed by zooming (to zero), setting the maximum power and focusing through the eyepiece.
Once all adjustments have been made, the healthcare professional places the eyeglass lens face up on the lens. The lens is fixed to prevent slipping, after which its main parameters (optical power, position of the main meridians) are determined. Manipulations are repeated twice – for the left and right lenses.
Rules for choosing medical instruments
The main criterion for choosing a dioptrimeter is the price. The type and design features of the device depend on the cost. Manual lensmeters are much cheaper than automatic ones, but they are significantly inferior to them in terms of convenience, since they increase the burden on the doctor and the number of necessary actions. The manual device is operated only by qualified specialists who have undergone preliminary training. The automatic device is available to a wider circle of medical staff, since the collection and processing of information is automated.
In medical practice, both manual and automatic lensmeters can be used, since the reliability of the information obtained is at the same level. Ultimately, it all depends on the skills of the doctor who is trying to master this or that device.
What parameters should be considered when choosing medical instruments? First, the angle of inclination of the device. The optimal indicator is the range from 45 to 90 °. The specialist will have a whole set of options for tilting the device, which will increase the quality and accuracy of the study. Secondly, the possibility of changing the position of the lensmeter. Experts recommend paying attention to the type of lighting device. The safest, most convenient and durable option is the LED lamp. Automatic shutdown of the device is not included in the list of mandatory functions, but is a convenient addition. If the specialist forgets to turn off the device, he will stop working on his own after 2-6 minutes from the last action.
Pay attention to the error in the definition – it should not exceed 1 °.
Another important aspect is the ergonomics of the device. Be guided by the size of the room in which the diopter will be installed. For small offices, a miniature vertical mount is suitable, while large horizontal lensmeters are an excellent option for spacious rooms.