Refractive errors are an ophthalmological disease in which reduced vision is associated with an abnormal focus of the image. Symptoms of the pathology are blurred vision along with rapid eye fatigue during visual work. In addition, discomfort from a headache with eye loads is possible. Visometry, refractometry, ophthalmoscopy, biomicroscopy and perimetry are used to diagnose refractive errors. Therapeutic tactics are reduced to the appointment of contact methods of optical correction. Modern methods of treatment are represented by laser and refractive surgery.
Refractive errors include myopia (nearsightedness), hypermetropia (farsightedness), astigmatism and presbyopia.
Reason for violation
There are many reasons for the development of refractive error of the eye, but it is far from always possible to establish the etiological factor. Hypermetropia is the result of a delayeye growth. Under normal conditions, this is diagnosed during the newborn. Other forms of refractive and accommodation disorders are associated with polyetiological pathologies, the main causes of which are:
- Anatomical feature of the structure of the eyes. In people with myopia, an elongated sagittal axis of the eyeballs is determined. In the presence of farsightedness, the anteroposterior axis of a person is shortened. A predisposing factor is also often a change in the refraction of the optical medium.
- Influence of hereditary predisposition. For example, myopia is a genetically determined pathology. In the presence of a dominant type of inheritance, this disease is characterized by a milder course and occurs later. The recessive form of the pathology is characterized by an early onset, and, in addition, an unfavorable prognosis.
- Influence of excessive visual loads. Prolonged visual work (whether reading along with watching TV or playing computer games) leads to spasms of accommodation. A decrease in the accommodative ability of the eyes is a risk factor for the subsequent development of myopia.
Violation of the refraction of the eye in children also happen. More on that below.
Additional factors affecting the appearance of pathology
In addition to the above reasons, it is necessary to note the following factors affecting the development of such a pathology as refractive errors:
- Influence of infectious diseases. The myopic variant of clinical refractions often becomes a consequence of the transferredinfections in the form of rubella, ophthalmic herpes and so on. Impaired optical function is often caused by congenital toxoplasmosis.
- Another cause of this disease is an organic change in the anterior ocular segment. Eye injuries along with keratitis, cicatricial changes and opacities of the cornea lead to a change in the radius of the lens. Failure of the light beam path acts as a trigger for acquired astigmatism.
- The impact of metabolic disorders. Persons suffering from impaired metabolism are at risk of weakening accommodation. Patients with diabetes are the most likely to develop this disease. This can be explained by the intensive synthesis of sorbin.
What refractive error leads to the development of myopia? Primary weakness of accommodation and imbalance of convergence and accommodation.
Symptomatics
The clinical manifestation of refractive error is determined by its type. In the presence of myopia, patients complain of vagueness of distant images. When looking at a short distance, vision is not impaired. In order to improve perception, people squint their eyes. Long-term optical loads provoke the appearance of discomfort in the frontal and temporal region along with pain in the orbit and photophobia. Myopia makes it difficult to travel in your own transport and when watching movies in the cinema. Age-related changes lead to an improvement in the visual indicator in the fourth decadelife.
Patients with this pathology note that their vision deteriorates only when reading or using a smartphone. Examining an object located far away is usually not accompanied by visual dysfunctions. With the first degree of farsightedness, the compensation mechanism provides good near vision. A high level of farsightedness is accompanied by optical dysfunction, which is not related to the distance to the objects in question. The deterioration of vision with age may indicate the development of presbyopia.
Diagnosis
The diagnosis is usually based on anamnestic data, and, in addition, on the result of an instrumental research method and a functional test. In patients with suspected refractive error, visometry is carried out using trial lenses, as well as using skiascopy. Diagnosis usually includes the following tests:
- Computer refractometry, which is the main method for studying clinical refractions. With hypermetropia, visual dysfunctions in patients are eliminated with the help of converging lenses.
- Visometry. In the presence of myopia, the decrease in vision can fluctuate over a wide range. In the case of performing visometry according to standard methods using the Golovin table, visual dysfunction in hypermetropia cannot be established.
- Ophthalmoscopy. During the examination of the fundus in patients with myopia, myopic cones are found along with staphylomas and degenerativedystrophic changes in the region of the macula. In the peripheral part of the retina, multiple round and, in addition, slit-like defects can be visualized.
Refractive error in children
The difference in eye refraction after the birth of a child can be quite large. Both myopia and severe hypermetropia may develop. At the same time, the average value of the refraction of the child is within the limits of hypermetropia, with a value of +2.5 - +3.5 diopters. The vast majority of babies have astigmatism, with rates of at least 1.5 diopters.
During the first year after birth, at the time of increased emmetropization, the difference in refractions is significantly reduced - the refraction of farsightedness and myopia shifts to emmetropia values, while astigmatism also decreases. The course of this process slows down a little in the time period of life from 1 to 3 years, after which the refraction in the vast majority of children is corrected, approaching emmetropia.
What other diagnostic methods are used?
During the diagnosis, if a refractive error is suspected, the following research and diagnostic options can be additionally carried out:
- Ultrasound examination of the eyes. Ultrasound examination is carried out in order to measure eye parameters. In the presence of myopia, the lengthening of the anteroposterior axis is determined, and in the case of hyperopia, its shortening is fixed. In the presence of the fourth degreemyopia often reveal changes in the vitreous body.
- Performing perimetry. Within the framework of this study, a narrowing of the angular space is observed, which is visible to the eye with a fixed gaze. For patients with astigmatism, the loss of certain areas from the visual field is typical. For a detailed diagnosis of the central region of visible space, the Amsler test is used.
- Carrying out biomicroscopy of the eyes. This study reveals a single erosive defect on the cornea. If the patient has hypermetropia, it is often possible to visualize injections of conjunctival vessels.
Next, we will find out how refractive errors are treated, and what therapeutic methods are currently used most often.
Treatment of pathology
The tactics of therapy are determined by the form of refractive error. Myopic patients are prescribed spectacle correction using diverging lenses. In the presence of the first degree of myopia, the compensatory mechanism allows the use of contact lenses and glasses only as needed. With the development of weak farsightedness, patients are prescribed glasses with converging lenses exclusively for working at a short distance. The constant use of glasses is prescribed in the presence of severe asthenopia. Contact lens use may have a less pronounced effect, which is largely due to the formation of a small image on the inner membrane of the eyes.
For the treatment of presbyopia, in addition to lenses for correction, converging lenses are prescribed,having a spherical shape. Patients suffering from astigmatism are individually selected glasses in which lenses of a spherical and cylindrical type are combined. Contact correction involves the use of a toric lens. Against the background of the low effectiveness of spectacle correction, microsurgical treatment is prescribed, which is reduced to the application of micro-cuts on the corneas. In the presence of the first degree of astigmatism, excimer laser correction is allowed. Against the background of a high degree of the disease, patients are prescribed the implantation of phakic lenses.
Forecast
Prognosis for this disease is often favorable. Timely correction of optical dysfunctions allows achieving full compensation.
Prevention
Specific methods of prevention have not yet been developed. As for non-specific preventive measures, they are aimed at preventing spasms of accommodation, and, in addition, at stopping the progression of the pathology.
This requires visual gymnastics, taking breaks while working at a computer or reading books. It is equally important in the framework of prevention to also monitor the lighting. Patients in middle and old age are recommended to undergo an annual examination by an ophthalmologist. In this case, it is necessary to measure intraocular pressure and carry out visometry.
