What is keratometry and how is it conducted?

Keratometry is an ophthalmological examination in which the degree of curvature of the anterior surface of the cornea of ​​the eye is assessed. These data are necessary for the correct selection of contact lenses, accurate diagnosis of keratoglobus or kerakonus.

Keratometry is done by the newborn in order to determine the visual acuity and diagnosis of glaucoma in the early stages. Also, the study is necessarily performed before the operation of lens replacement - it allows you to accurately calculate the index of the optical power of artificial lenses. The results of keratometry are obtained in diopters (more often) or in millimeters (less often).

Method definition

Keratometry is performed manually or with the use of a keratometer.In the first case, the doctor brings the optical ruler as close as possible to the patient's eye, the second eye must be closed. In the course of the study, the nasal and temporal edges of the cornea are measured, the result is fixed in millimeters.

With the help of a keratometer, the diagnosis is more convenient, and its results are more accurate.A special formula R = 2dI / O is recorded in the memory of the device, allowing to calculate the distance between objects and the surface of reflection, the size of the image and the object in automatic order.

Keratometry is carried out manually and using a special device. The second option allows you to get more accurate results.

In the framework of the Zhaval-Schiotz technique, a keratometer with a given picture is used - it is located at a certain distance from the patient.The device can be fixed in two positions. The refractive power of the eyeball in this case will depend on the radius of curvature of the surfaces, the refractive indices in the environment of the eye, the distance between the surfaces.

Device for keratoplasty using the Zhaval-Schiotz method

Application area

Keratometry is carried out:

• in the individual selection of contact lenses;
• in newborn babies for visual diagnosis;
• in preparation for the operation of lens replacement.

This is one of the most accurate ophthalmological studies used to assess the degree of curvature of the anterior surface of the cornea of ​​the eye.

Procedure

Ophthalmologists can use an absolute scale or a relative scale as part of the diagnostic.Absolute allows you to monitor the dynamics and compare changes occurring in the cornea of ​​the eye at different periods. In it, the values ​​of the test points are given initially, and different diopter ranges are indicated by this or that color.

Results of keratometry

If the cornea of ​​the patient is completely healthy, on the absolute scale during the examination the doctor will see a yellow-green color.

On the relative scale, the values ​​are not fixed, since they adjust to the dioptric range of a certain area of ​​the cornea.To decipher the testimony, the physician must first read the scale.

The values ​​of the relative check scale are adjusted to the range of the specified area of ​​the cornea.

Keratometry is performed manually or with the use of apparatus.If the measurements are done manually, the doctor puts the optical ruler as close to the patient's eye as possible. The second eye should be closed by hand. The results are recorded in millimeters and recorded.

Hardware diagnostics is carried out as follows:

1. The patient sits as close as possible to the device.
2. The view is fixed at one point, the eyes will need to relax as much as possible.
3. A laser beam scans the cornea.
4. The computer processes the results.

Automated diagnostics takes a few seconds.

Carrying out keratometry

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results

The result of keratometry is a keratogram, a topographic drawing showing the changes in the optical power of the cornea.Interpret the results of the study can only a qualified ophthalmologist taking into account the patient's history and data from other studies. The diagnosis of keratoconus is made if in one of the axes with complex myopic astigmatism the indicator is 46 diopters.If it is less than 40 diopters, most likely the patient has previously treated myopia surgically.

During the diagnosis, you need to carefully monitor the proportions of the posterior-anterior axis and the keratometry parameter, since the anteroposterior axis is inversely proportional to the keratometry.

Normally, the higher the test score, the smaller the anterior-posterior axis. In case of visual impairment, myopia or hyperopia develops.

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conclusions

Keratometry is a modern method of assessing the curvature of the anterior surface of the cornea of ​​the eye. Diagnosis is carried out manually or using a special device - the second method is more accurate. The doctor should decipher the keratogram. The higher the keratometry obtained for normal vision, the smaller the anterior-posterior axis, and vice versa. If there are diseases, these proportions are violated.

Read also about such diagnostic methods as pachymetry and keratotopography.