Ultrasound examination (ultrasound) completes the ophthalmological examination of the patient because it is contact. And any microdamage to the cornea can distort the readings of autorefractometry or aberrometry.
A-scanning (ultrasound biometry) determines the size of the anterior chamber of the eye, the thickness of the lens and the anteroposterior segment (APS - anteroposterior size of the eye) with an accuracy of hundredths of a millimeter. With myopia, the eyes become larger, which is recorded by the device. PZO is also used when identifying the degree of progression of myopia. The normal PZO is 24 mm (Fig. 15).
Rice. 15. Dimensions of the eyeball. The length of the anteroposterior segment of a normal eyeball practically coincides with the diameter of a five-ruble coin
A B-scan is a conventional two-dimensional ultrasound of the eye. It is possible to diagnose retinal detachment (urgent surgery is required, laser correction is at best delayed for a long time), destruction vitreous, intraocular tumors, etc.
Pachymetry. Measuring corneal thickness. The same indicator that most often provides contraindications for laser correction. If the cornea is too thin, correction is often impossible. The normal central thickness of the cornea is 500–550 micrometers (~0.5 mm). Now there are not only ultrasound, but also optical pachymeters that measure the thickness of the cornea without touching it.
Conclusion
All of the above are just the main stages ophthalmological examination. There may be a lot more research and devices, especially if you are found to have any eye diseases. There are optional but desirable examinations that I decided not to mention here (such as determining the dominant eye, deviation, etc.).
After completing the ophthalmological examination, the doctor makes a diagnosis and answers your questions, the main one of which is: “Can I do laser correction? It is extremely rare that situations arise in which laser correction is necessary for medical reasons (for example, when there is a large difference in the “pros” or “cons” between the eyes).
Features of filling out an advisory report
After the examination, the patient is given a consultation report, which reflects the main results, diagnosis and recommendations. Sometimes very short, sometimes an impressive work on several sheets, including various prints and photographs. Who's lucky? Volume doesn't mean anything here. However, to gain a little useful information it is possible from it. Let me give you an example.
Advisory opinion No....
Ivanov Ivan Ivanovich. Date of birth: 01/01/1980.
Examined at the Z clinic on 01/01/2008.
Makes complaints about poor eyesight away from the age of 12. Over the past five years, myopia has not progressed, which is confirmed by data from outpatient card. Preventive laser coagulation of the retina was performed on both eyes in 2007. Wears soft contact lenses daily for the last 3 years. I took them off for the last time 7 days ago. Hepatitis, tuberculosis, other infectious and general somatic diseases, denies allergies to medications.
For a narrow pupil:
OD sph –8.17 cyl –0.53 ax 178°
OS sph –8.47 cyl –0.58 ax 172°
In conditions of cycloplegia (with a wide pupil):
OD sph –7.63 cyl –0.45 ax 177°
OS sph –8.13 cyl –0.44 ax 174°
Visual acuity.
Currently developed a large number of formulas for accurate calculations optical power implantable intraocular lens(IOL). All of them take into account the value of the anteroposterior axis (APA) of the eyeball.
The contact method of one-dimensional echography (A-method) is widely used in ophthalmological practice for studying the PZO of the eyeball, however, its accuracy is limited by the resolution of the device (0.2 mm). In addition, incorrect position and excessive pressure of the sensor on the cornea can lead to significant errors in measuring the biometric parameters of the eye.
The optical coherent biometry (OCB) method, in contrast to the contact A-method, allows for more high accuracy measure the POV with subsequent calculation of the optical power of the IOL.
The resolution of this technique is 0.01-0.02 mm.
Currently, along with OCB, ultrasonic immersion biometry is a highly informative method for measuring PZO. Its resolution is 0.15 mm.
An integral part of the immersion technique is immersing the sensor in an immersion medium, which eliminates direct contact of the sensor with the cornea and, therefore, increases the accuracy of measurements.
J. Landers showed that partial coherent interferometry, carried out using the IOLMaster device, allows one to obtain more accurate results than immersion biometry, however, J. Narvaez et al. in their study did not find significant differences between the biometric parameters of the eyes measured by these methods.
Target- comparative assessment of eye POV measurements using IB and OCB to calculate IOL optical power in patients with age-related cataracts.
Material and methods. 12 patients (22 eyes) with cataracts aged from 56 to 73 years were examined. Average age of patients was 63.8±5.6 years. In 2 patients, mature cataracts were diagnosed in one eye (2 eyes), and immature cataracts were diagnosed in the paired eye (2 eyes); 8 patients had immature cataracts in both eyes; 2 patients had initial cataract in one eye (2 eyes). The fellow eyes were not examined in 2 patients due to pathological changes in the cornea (post-traumatic corneal cataract - 1 eye, opacification of the corneal graft - 1 eye).
Besides traditional methods studies including visometry, refractometry, tonometry, biomicroscopy of the anterior segment of the eye, biomicroophthalmoscopy; all patients underwent an ultrasound examination of the eye, including A- and B-scanning using the NIDEK US-4000 echo scanner. To calculate the optical power of the IOL, the PZO was measured using the IB on the Accutome A-scan synergy device and the OKB on the IOLMaster 500 (Carl Zeiss) and AL-Scan (NIDEK) devices.
Results and discussion. PPV ranging from 22.0 to 25.0 mm was recorded in 11 patients (20 eyes). In one patient (2 eyes), the POV in the right eye was 26.39 mm, in the left eye - 26.44 mm. Using the ultrasound IB method, it was possible to measure PZO in all patients, regardless of the density of the cataract. In 4 patients (2 eyes - mature cataract, 2 eyes - localization of opacities under the posterior capsule of the lens) during OCB using the IOLMaster device, PZO data were not determined due to high density lens opacities and insufficient visual acuity of patients to fix their gaze. When performing OCB using the AL-Scan device, PZO was not recorded only in 2 patients with posterior capsular cataract.
A comparative analysis of the results of a study of the biometric parameters of the eyes showed that the difference between the PPV indicators measured using IOL-Master and AL-scan ranged from 0 to 0.01 mm (on average - 0.014 mm); IOL-Master and IB - from 0.06 to 0.09 mm (average - 0.07 mm); AL-scan and IB - from 0.04 to 0.11 mm (average - 0.068 mm). The IOL calculation data based on the results of measuring the biometric parameters of the eye using OCB and ultrasound IB were identical.
In addition, the difference in anterior chamber (ACD) measurements between the IOL-Master and AL-scan ranged from 0.01 to 0.34 mm (mean 0.103 mm).
When measuring horizontal corneal diameter (white to white or WTW), the difference in values between the IOL-Master and AL-scan devices ranged from 0.1 to 0.9 mm (average 0.33), with WTW and ACDs were higher on AL-scan compared to IOLMaster.
It was not possible to compare keratometric indicators obtained on the IOL-Master and AL-scan, since these measurements are carried out in different departments corneas: on IOLMaster - at a distance of 3.0 mm from the optical center of the cornea, on AL-scan - in two zones: at a distance of 2.4 and 3.3 mm from the optical center of the cornea. The data for calculating the optical power of the IOL based on the results of measuring the biometric parameters of the eye using OCB and ultrasound immersion biometry coincided, with the exception of cases of myopia high degree. It should be noted that the use of AL-scan made it possible to measure biometric indicators in 3D control mode over the patient’s eye movements, which certainly increases the information content of the results obtained.
conclusions.
1. The results of our study showed that the difference in PZO measurements using IS and OCB is minimal.
2. When performing immersion biometry, the PZ values were determined in all patients, regardless of the degree of cataract maturity. The use of AL-scan, in contrast to IOLMaster, makes it possible to obtain PZO data for denser cataracts.
3. There were no significant differences between biometric parameters and IOL optical power indicators obtained using IB and OKB.
Ultrasound examination of the eye – advanced diagnostic method, which is based on the principle of echolocation.
The procedure is used to clarify the diagnosis in case of detection of ophthalmological pathologies and determine their quantitative values.
What is eye ultrasound?
Ultrasound of the eyeball and eye orbits allows you to determine localization areas pathological processes, which can be determined due to the reflection of high-frequency waves sent from such areas.
The method is quick and easy to perform and practically complete absence preliminary preparation.
In this case, the ophthalmologist receives the most complete picture of the condition of the tissues of the eye and the fundus of the eye, and can also assess the structure of the muscles of the eye and see abnormalities in the structure of the retina.
This is not only a diagnostic, but also a preventive procedure, which in most cases is performed both after surgical interventions, and before them in order to assess risks and prescribe optimal treatment.
Indications for use of this method
- cloudiness of various types;
- presence in the organs of vision foreign bodies with the ability to determine their exact size and location;
- neoplasms and tumors of various types;
- farsightedness and myopia;
- cataracts;
- glaucoma;
- lens luxation;
- pathology optic nerve;
- retinal detachment;
- adhesions in the tissues of the vitreous body and disturbances in its structure;
- injuries with the ability to determine their severity and nature;
- disturbances in the functioning of the eye muscles;
- any hereditary, acquired and congenital anomalies in the structure of the eyeball;
- hemorrhages in the eye.
In addition, ultrasound examination makes it possible to determine changes in the characteristics of the optical media of the eye and estimate the size of the orbit.
Ultrasound also helps to measure the thickness of fatty tissue and its composition, which is necessary information when differentiating forms of exophthalmos (“bulging eyes”).
Contraindications
- open injuries of the eyeball with violation of the integrity of its surface;
- hemorrhages in the retrobulbar area;
- any damage to the eye area (including eyelid injuries).
What does an ultrasound of the eye show: what pathologies can be detected
Ultrasound of the eye shows many ophthalmological diseases, in particular, it is possible to diagnose diseases such as refractive errors (farsightedness, myopia, astigmatism), glaucoma, cataracts, pathologies of the optic nerve, degenerative processes of the retina, the presence of tumors and neoplasms.
Also, through the procedure, you can monitor the conditions of pathologies during treatment, as well as any ophthalmological inflammatory processes And pathological changes lens tissues.
How is an ultrasound of the eye done?
In modern ophthalmological practice, several types are used ultrasound examination, each of which is designed to perform specific tasks and is done using its own technical features:
In B-mode, no anesthesia is required, since the specialist moves the sensor over the eyelid closed eye, and to ensure normal conduct During the procedure, it is enough to lubricate the eyelid with a special gel, which will facilitate such sliding.
Normal indicators of a healthy eye during ultrasound
After the ultrasound procedure, the specialist passes the completed patient card to the attending physician, who deciphers the readings.
Normal indications for the procedure are:
Useful video
This video shows an ultrasound of the eye:
Minor deviations of these characteristics are acceptable, but if the values go far beyond such indicators, this is a reason to undergo additional examinations in order to confirm the disease and prescribe adequate treatment to the patient.
Causes of myopia
Today this phenomenon occurs very often. Statistics show that about a billion people around the world suffer from myopia. Ophthalmologists diagnose it at any age. However, it is first discovered in children aged 7 to 12 years, and the disease intensifies in adolescence. Between the ages of 18 and 40, visual acuity usually stabilizes. So, let's learn about the causes of myopia.
Briefly about the disease
The second name for the disease used by doctors is myopia. It is a visual impairment in which the patient sees close objects perfectly and poorly those that are at a distance. The term “myopia” was introduced by Aristotle, who noticed that people who have poor distance vision squint their eyes.
Speaking in the language of ophthalmologists, myopia is a pathology of eye refraction, when the image of objects appears in front of the retina. In such people, the length of the eye is increased or the cornea has a high refractive power. This is why refractive myopia occurs. Practice shows that most often these two pathologies are combined. With myopia, visual acuity decreases.
Myopia is classified into strong, weak, and moderate.
Why does myopia occur?
Ophthalmologists name several reasons for the development of myopia. Here are the main ones:
- Irregular shape of the eyeball. In this case, the length of the anteroposterior axis of the organ of vision is greater than normal, and when focusing, light rays simply do not reach the retina. The elongated shape of the eyeball is a stretch back wall eyes. This state of the vision system can change the fundus of the eye, for example, contribute to retinal detachment, myopic cone, and dystrophic disorders in the macular zone.
- Excessive refraction of light rays by the optical eye system. The size of the eye corresponds to the norm, however, strong refraction causes light rays to converge in focus in front of the retina, and not traditionally on it.
In addition to these causes of myopia, ophthalmologists also identify factors contributing to the development of this eye disease. These are the following circumstances:
- Genetic predisposition. Experts in the field of ophthalmology state that people do not inherit poor vision, but a physiological tendency towards it. And the first at risk are those patients whose father and mother are myopic. If only one of the parents has myopia, then the chances of their son or daughter developing the disease are reduced by 30 percent.
- Weakening of the scleral tissue often increases the size of the eyeball under the influence of increased intraocular pressure. The consequence of this is the development of myopia in a person.
- Weakness of accommodation, which leads to stretching of the eyeball.
- General weakening of the body as the basis for the formation of myopia. It is often the result of both overwork and poor nutrition.
- The presence of allergic and infectious diseases(diphtheria, scarlet fever, measles, hepatitis).
- Birth and brain injuries.
- Diseases of the nasopharynx and oral cavity in the form of tonsillitis, adenoids, sinusitis.
- Unfavorable operating conditions visual system. Ophthalmologists include excessive strain on the eyes and their overstrain; reading in moving vehicles, in the dark, in a lying position; sitting for many hours without breaks in front of a computer or TV screen; poor workplace lighting; incorrect posture while writing and reading.
All of the above reasons and factors, especially a combination of several of them, contribute to the development of myopia in children and adults.
In the ninth week intrauterine development The sagittal size is 1 mm; by 12 weeks it increases to an average of 5.1 mm.
total length eyes of a premature infant (25-37 weeks after conception) increases linearly from 12.6 to 16.2 mm. Measurement results based on more than modern research are given in the table below.
Newborn eye measurement results during ultrasound examination:
1. Average depth anterior chamber (including cornea) 2.6 mm (2.4-2.9 mm).
2. The average thickness of the lens is 3.6 mm (3.4-3.9 mm).
3. The average length of the vitreous body is 10.4 mm (8.9-11.2 mm).
4. The total length of the newborn's eye is 16.6 mm (15.3-17.6 mm).
Postnatal growth of the emmetropic eye can be divided into three stages:
1. The phase of rapid postnatal growth, when during the first 18 months of life the length of the eye increases by 3.7-3.8 mm.
2. More slow phase, between the ages of two and five years, the length of the eye increases by 1.1-1.2 mm.
3. The slow juvenile phase, which lasts until the age of 13 years, the length of the eye increases by another 1.3-1.4 mm, after which the growth of the eye in length is minimal.
Relationships between various structures eyes during growth. Ultrasound examination results.
Anterior-posterior eye size in boys (mm).
Dimensions of extraocular muscles and sclera
The fastest eye growth rate is observed in the first six months of life. All its sizes increase. At birth, the size of the cornea and iris is approximately 80% of the size of the cornea and iris of an adult.
The posterior segment, on the contrary, grows to a greater extent in the postnatal period. Consequently, this creates additional difficulties in predicting the results of surgical treatment of strabismus in very young children.
The thickness of the sclera at 6, 9 and 20 months of age is 0.45 mm, the same as in adult eyes.
The anterior-posterior axis (APA) is an imaginary line connecting the two ocular poles and showing the reliable distance from the tear film to pigment epithelium retina. Among doctors, the anterior-posterior axis is the length of the eye and this parameter, together with the refractive power, has a direct impact on the clinical refraction of the eye.
Anterior-rear axle dimensions:
- for a healthy adult - 22-24.5 mm;
- for a newborn child - 17-18 mm;
- for farsightedness (hypermetropia) - 18-22 mm;
- for myopia (myopia) - 24.5-33 mm.
The most low performance, respectively, in newly born children. All newborns are farsighted; intensive eye growth occurs in the first 3 years of life. As the child grows older, the clinical refraction increases. Mostly, by the age of 10, normal vision is formed and the dimensions of the anterior-posterior axis are close to 20 mm.
The genetic factor also plays an important role in the development of eyeball length. Despite the fact that the optimal POV parameters for an adult are 23-24 mm, in some cases, with great height and weight, healthy values can reach 27 mm. Finally eyeball, like the anterior-posterior axis, ends its development when the active growth of the entire human body stops.
In the case when the eyes regularly have to adapt to intense stress in conditions of insufficient lighting, the dimensions of the anterior-posterior axis reach pathological indicators characteristic of such a diagnosis as myopia. Myopia develops in both adults and children, most often schoolchildren who study lessons in dim light and do not use a desk lamp. For prolonged periods professional activity, which requires special care when working with small objects, high-quality lighting and contrast are a must. In the absence of the above conditions, especially with poor accommodation, the development of myopia is inevitable.
Determining the length of the anteroposterior segment is mandatory if refractive error is suspected in children and adolescents. Studying the length of the eye's PZ is the only effective method today that allows one to reliably determine the progression of myopia.
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