Surprisingly, such a small-sized organ of vision is targeted by a huge arsenal of examinations and diagnostic procedures: from simple letter tables to obtaining a layered image of the retina and the optic nerve disc using OCT and a detailed study of the course of vessels on the fundus in FAG.
Most studies are conducted according to strict indications. Nevertheless, when going to an appointment with an ophthalmologist, be prepared to spend from half an hour to an hour or more, depending on the number and complexity of the studies you need, and on the workload of your doctor.
Determination of visual acuity and refraction
Visual acuity is determined for each eye separately. At the same time, one of them is covered with a shield or palm. At a distance of 5 meters, you will be shown letters, numbers or signs of various sizes that you will be asked to name. Visual acuity is characterized by signs of the smallest size that the eye is able to distinguish.
Next, you will be given a frame in which the doctor will put various lenses, offering you to choose which one is more clearly visible. Or, a device called a foropter will be installed in front of you, in which the lens change is carried out automatically. Refraction is characterized by the strength of the lens, which provides the highest visual acuity for this eye, and is expressed in diopters. Positive lenses are required for farsightedness, negative lenses for myopia, cylindrical lenses for astigmatism.
Automatic refractometry and aberrometry
Autorefractometers and aberrometers are designed to automatically detect refraction. All that is required of you is to place your chin on the stand and fix the mark presented with your eye.
The autorefactometer evaluates in which position light rays are focused relative to the retina and measures the refractive power of the cornea.
The aberrometer, based on the analysis of the wavefront of the eye, determines even imperceptible optical imperfections of its media. This data is important when planning LASIK.
Field of vision research
It is carried out using a perimeter device, which is a hemispherical screen. You are asked to fix the mark with the examined eye and, as soon as you notice the luminous dots appearing in different parts of the screen with your peripheral vision, press the signal button or say “yes”, “I see”. The field of vision is characterized by a space in which the eye with a permanently fixed gaze determines visual stimuli. Characteristic visual field defects occur in eye diseases, for example, with glaucoma, as well as when the optic nerve and brain are affected by a tumor or as a result of a stroke.
Measurement of intraocular pressure
Non-contact measurement is carried out using an automatic tonometer. You are asked to place your chin on the stand of the device and fix the glowing mark with your eyes. The autotonometer releases a jet of air in the direction of your eye. Based on the resistance of the cornea to the air flow, the device determines the level of intraocular pressure. The technique is absolutely painless, the device does not come into contact with your eyes.
The contact method of measuring intraocular pressure is accepted as standard. After instilling the “freezing” drops, the doctor touches your cornea with a weight with a painted pad. The level of intraocular pressure is determined on paper by the diameter of the print of the unpainted area. This technique is also painless.
Since glaucoma is a disease associated with increased intraocular pressure, regular measurement of it is a necessary condition for maintaining the health of your eyes.
Test with “cover-up”
There are many methods for diagnosing strabismus. The simplest of them is a “cover–up” test. The doctor asks you to fix an object in the distance with your gaze and, alternately covering one of your eyes with his palm, watches the other: will there be an installation movement. If it occurs internally, divergent strabismus is diagnosed, if outward – convergent.
Biomicroscopy of the eye
A slit lamp or biomicroscope allows you to examine the structures of the eye under high magnification. You are asked to place your chin on the stand of the device. The doctor illuminates your eye with the light of a slit lamp and under high magnification first examines the anterior part of the eye (eyelids, conjunctiva, cornea, iris, lens), and then with the help of a strong lens examines the fundus (retina, optic nerve disc and vessels). Biomicroscopy allows you to diagnose almost the entire spectrum of eye diseases.
With the help of an ophthalmoscope, the doctor directs a beam of light into your eye and examines the retina, the optic nerve disk and blood vessels through the pupil.
Often, for a more complete overview, you are pre-instilled with drops that dilate the pupil. The effect develops after 15-30 minutes. During their action, sometimes for several hours, you may have difficulty focusing your gaze on objects located nearby. In addition, the sensitivity of the eye to light increases, it is recommended to wear sunglasses on the way home after the examination.