RU2258461C1 - Method for predicting optic neuropathy in case of endocrine ophthalmopathy - Google Patents

Abstract

FIELD: medicine, ophthalmology.

SUBSTANCE: one should perform computer-tomographic testing to detect the ratio of the length of optic nerve's orbital part to its diameter in the point being at the distance of about 10 mm against ocular posterior pole. At value of this ratio being above 7.29 one should diagnose optic neuropathy. The innovation enables to detect both early and latent stages of optic neuropathy.

EFFECT: higher accuracy of diagnostics.

3 ex

Description

The proposed method relates to ophthalmology and is intended for the early diagnosis of optical neuropathy (OH) in endocrine ophthalmopathy (EOP). OH occurs in approximately 1.9% -10% of patients with EIT (Char DH Thyroid Eye Disease. 3 ^rd ed. Boston: Butterworth-Heinemann, 1997; Tveten S., Mohr C., Esser J. Orbitadekompression in der Behandlung der endokrinen Orbitopathe Mund-Kiefer-Gesichschir., 1998; 2 (suppl. 1): 102-106). They diagnose OH, usually late, when pronounced changes in the fundus appear, accompanied by a decrease in visual acuity. Identification of the latent stage of OH will allow timely initiation of its adequate treatment and preservation of the patient's high visual functions.

Currently, OH is detected in its late stage using the method of ophthalmoscopy, perimetry, when there is a decrease in vision and a change in the field of vision. An important role in the diagnosis of image intensifiers belongs to instrumental research methods - computed tomography and magnetic resonance imaging. Using these methods, the length of the retrobulbar space, the thickness of the extraocular muscles and their density are determined. There is a known method for diagnosing OH by determining the “muscle index”: measure in frontal view at an equal distance between the posterior pole of the eye and the apex of the orbit, calculate the vertical index in percent according to the formula: add the thickness of the lower rectus muscle to the thickness of the superior rectus muscle, divide this value by the height of the orbit, measured along a vertical line passing through the optic nerve, and multiplied by the number 100. The horizontal index corresponds to the following value, expressed as a percentage: the thickness of the outer straight muscle thickness minutes add internal rectus, divided by the width of the orbit, as measured along a horizontal line passing through the optic nerve, and multiplying by 100. Most of these two values is taken as "muscle index". It is believed that with a "muscle index" of more than 50%, the likelihood of developing optical neuropathy is high. However, according to the authors, the method is uninformative and not accurate enough. In addition, the authors correlated changes in muscle size with an already developed OH (Giaconi JA, Kazim M., Rho T., Pfaff C. CT scan evidence of dysthyroid optic neuropathy. Ophthalmic Plast. Reconstr. Surg., 2002, vol. 18, No. 3, P.177-182). This method is taken as the closest analogue.

The technical result of the proposed method for the diagnosis of OH with EOP is the ability to diagnose OH, including at the stage of preclinical manifestations. The technical result is achieved by determining the ratio of the length of the orbital part of the optic nerve to its diameter at a point located 10 mm from the posterior pole of the eye, and evaluating this indicator with a boundary value (7.29).

Measurement of the length and diameter of the orbital part of the optic nerve is performed on computed tomograms of the orbits in axial projection with a slice thickness of 2 mm.

To identify the normal ratio of the length and diameter of the orbital part of the optic nerve, a computer-tomographic study of healthy individuals over the age of 18 years without any pathology of the orbit and optic nerve was performed. Using static processing Biostat 3.03, the dimensions of the unchanged optic nerve were calculated - the median length was 27.1 mm, and the median of its diameter at a point 10 mm from the posterior pole of the eye was 3.95 mm. The ratio of the length of the optic nerve to its diameter at a distance of 10 mm from the posterior pole of the eye was normally 6.94 (statistically significant maximum value in healthy orbits reached 7.28).

Having retrospectively analyzed a large group of patients with EOP, we found that when the ratio of the length and diameter of the orbital part of the optic nerve is 8.0 or more, ophthalmological signs of OH are revealed, which are also confirmed by methods such as ophthalmoscopy, computer perimetry, and electrophysiological studies. With a ratio of 7.29 to 7.99, clinical signs of OH developed over the next 3 months.

It is known that the orbital part of the normal optic nerve has a physiological bend and its length can increase by several millimeters. With the growth of exophthalmos, the reserve of physiological bending is exhausted and the optic nerve is stretched, while its diameter decreases. A decrease in the diameter of the optic nerve leads to compression of the nerve fibers of the optic nerve trunk with an inextensible dura mater, which leads to the development of nerve ischemia, metabolic disturbances in the axons of retinal ganglion cells and a slowdown of axoplasmic current. The result of these disorders is the development of optical neuropathy. On the clinical material, the normal ratio was reliably established, not exceeding 7.28, which is a reserve of physiological bending of the optic nerve. At the same time, clinically expressed OH develops at a ratio of 8 or more, when the reserve of physiological bending of the optic nerve is already exhausted. An interval in the range of 7.29 to 7.99 indicates the beginning of compression of the optic nerve trunk by the dura mater and a high likelihood of developing OH.

The method is as follows: computed tomography of the orbits according to the generally accepted method in axial projection. Then, in turn, the length of the orbital part of the optic nerve is measured from the posterior pole of the eye to the entrance to the optic nerve canal (value 1) and its diameter at a point 10 mm from the posterior pole of the eye (value 2). After obtaining the measurement results, a simple arithmetic division of indicator 1 by indicator 2 is performed.

The resulting ratio is compared with the normal one, amounting to no more than 7.28.

Example 1. Patient D., born in 1958 was admitted with a diagnosis of OU - EOP in st. compensation. The visual acuity of both eyes is 1.0. On the fundus of the OU - optic nerve discs are pale pink, with clear borders. The course and caliber of the vessels is not changed. In the macular region - without pathology. With computer perimetry, pathology was not detected. When computed tomography identified:

- the length of the optic nerves from the posterior pole of the eye to the entrance to the optic nerve canal and was for OD - 23.1 mm; for OS - 23.1 mm;

- the thickness of the optic nerves at a distance of 10 mm from the posterior pole of the eye and was for OD - 4.4 mm; for OS - 4.0 mm.

Thus, the ratio “length: diameter” was 5.25 for OD, 5.78 for OS, i.e. OH is absent, as confirmed by other ophthalmic methods.

Example 2

During a routine examination of patient P., born in 1956, it was noted that the patient did not show complaints of visual impairment, she did not find any static perimetry of changes in her visual fields, with ophthalmoscopy there was a slight stasis in the venous collector. In addition, computed tomography of the orbits was performed, in which retrospectively calculated:

- the length of the optic nerves from the posterior pole of the eye to the entrance to the optic nerve canal and was for OD - 31.8 mm; for OS - 34.3 mm;

- the thickness of the optic nerves at a distance of 10 mm from the posterior pole of the eye and amounted to OD - 4.3 mm; for OS - 4.4 mm.

The ratio of length to diameter of the optic nerve for OD was 7.4; for OS - 7.8.

The same patient returned again after 4 months with complaints of visual impairment and was admitted to the hospital with a diagnosis of OU - EOP in st. decompensation. Visual acuity OD = 0.8 does not correct; OS = 0.5 does not correct. On the fundus of the OU, the opticans are pale pink, the borders are faded. The course and caliber of the arteries are not changed, the veins are sharply dilated, convoluted, cyanotic (symptoms on OS are more pronounced). In the macular region, OD - without pathology, OS - the macular reflex is sharply weakened. With computer perimetry, numerous absolute and relative scotomas were found on the periphery of both eyes, in the OS - expansion of the blind spot, paracentral absolute and relative scotomas. When computed tomography identified:

- the length of the optic nerves from the posterior pole of the eye to the entrance to the optic nerve canal and was for OD 39.5 mm; for OS - 43.8 mm;

- the thickness of the optic nerves at a distance of 10 mm from the posterior pole of the eye and was for OD - 4.1 mm; for OS - 4.0 mm.

Thus, the ratio “length: diameter” was for OD - 9.63; for OS - 10.95, i.e. OH is present in both eyes, but is more pronounced in OS, as confirmed by other ophthalmic methods.

Example 3. Patient S., born in 1956 was admitted with a diagnosis of OU - EOP in st. decompensation. Visual acuity OD = 0.01 does not correct; OS = 0.5 does not correct. At the fundus of the OU, the optic nerve disc is pale, the borders are faded, and it is promoted to the vitreous. Arteries are sharply narrowed, their course is not changed, veins are sharply expanded, twisted, cyanotic. In the macular region OU - the macular reflex is sharply weakened. Computed perimetry revealed a significant narrowing of the visual field to 20º (due to the numerous absolute and relative confluent cattle on the periphery of both eyes. Computed tomography determined:

- the length of the optic nerves from the posterior pole of the eye to the entrance to the optic nerve canal and was for OD - 37.2 mm; for OS - 41.1 mm;

- the thickness of the optic nerves at a distance of 10 mm from the posterior pole of the eye and was for OD - 2.4 mm; for OS - 2.4 mm.

Thus, the ratio “length: diameter” amounted to OD - 15.5 for OS - 17.13, i.e. the far advanced stage of OH is present in both eyes, but is more pronounced in OS, which is confirmed by other ophthalmic methods. The patient underwent complex drug therapy, against the background of which there was a positive dynamics in the ophthalmic status of the patient, the improvement of visual functions in OD = 0.4 does not correct; OS = 0.5 does not correct. During the control computed tomography identified:

- the length of the optic nerves from the posterior pole of the eye to the entrance to the optic nerve canal and was for OD - 41.2 mm; for OS - 40.1 mm;

- the thickness of the optic nerves at a distance of 10 mm from the posterior pole of the eye and amounted to OD - 3.4 mm; for OS - 3.7 mm.

And the ratio “length: diameter” was in dynamics against the background of treatment for OD - 12.1 for OS - 10.8, which also confirms the positive effect of treatment.

Thus, the proposed diagnostic method allows to recognize OH in endocrine ophthalmopathy, including in the latent stage.

Claims (1)

A method for diagnosing optical neuropathy with endocrine ophthalmopathy, characterized in that the ratio of the length of the orbital part of the optic nerve to its diameter at a point located at a distance of 10 mm from the posterior pole of the eye is determined, and with its magnitude more than 7.29, optical neuropathy is diagnosed.