RU2275842C2 - Method for detecting the value of eyeball's shift - Google Patents

Abstract

FIELD: medicine, ophthalmology.

SUBSTANCE: the present innovation deals with pre-operational diagnostics and therapy in patients with orbital lesions and its post-traumatic deformations. One should carry out spiral computed tomography of facial cranium to obtain image cut-off either in frontal and/or axial planes. Upon tomograms obtained one should make a random horizontal crossing the images of both eyeballs and measure the chords against external up to internal borders of every eyeball image and the height of segments, as well. Then one should calculate the value of shift by the following formula:

where - absolute value of shift (mm), a₁ - a chord's size at cut-off on tomogram of healthy eyeball (mm), a₂ - a chord's size at cut-off on tomogram of shifted eyeball (mm), h₁ - segment's height at cut-off on tomogram of healthy eyeball (mm), h₂ - segment's height at cut-off on tomogram of healthy eyeball (mm).

EFFECT: higher accuracy of detection.

1 cl, 1 dwg, 1 ex

Description

The invention relates to medicine and can be used for preoperative diagnosis and treatment of patients with injuries and post-traumatic deformations of the orbit.

A known method of determining the magnitude of the displacement of the eyeball using an exophthalmometer, consisting of two oblique mirrors, under which there is a millimeter scale. Mirrors are applied to the outer edges of both orbits. According to the reflection of the corneas of the patient’s directly set eyes in the mirrors, the displacement of the eyeball is determined on a scale [B. Brodsky Ophthalmology. M., 1934, p. 153-155].

However, in this way you can measure the displacement of the eyeball with exo- or enophthalmos only in cases where there is no change in the proportions of the bones of the middle zone of the face.

The magnitude of the displacement of the eyeball with hippophthalmus in this way cannot be measured.

The aim of this invention is to improve the accuracy of determining the magnitude of the displacement of the eyeball.

This goal is achieved by the fact that in the method for determining the displacement of the eyeball, a distinctive feature is that they conduct spiral computed tomography of the facial skull, obtain slices of the image of the eyeballs in the frontal and / or axial planes, on which a horizontal line intersects the images of both eyeballs, measure the chords from the outer to the inner borders of the image of each eyeball and the height of the segments and calculate the amount of displacement according to the formula:

where | ε | - the absolute value of the displacement (mm),

and ₁ - the size of the chord of the slice on the tomogram of a healthy eyeball (mm),

and ₂ - the size of the chord of the slice on the tomogram of the displaced eyeball (mm),

h ₁ - the height of the slice segment on the tomogram of a healthy eyeball (mm),

h ₂ - the height of the slice segment on the tomogram of the displaced eyeball (mm).

The magnitude of enophthalmos or exophthalmos is determined in the frontal projection. The magnitude of the hypophthalmus or hyperphthalmus is determined in axial projection.

It is desirable that the thickness of the slice and the interval between the slices of the spiral computed tomogram were 1 mm. As the thickness of the slice and the intervals between the slices of the spiral computed tomogram increase, the accuracy of determining the displacement of the eyeball decreases.

The method is as follows.

Spiral computed tomography (CT) of the facial skull is carried out, which is carried out with a slice thickness and an interval between slices of up to 1 mm. A very important detail of the survey is to observe strict symmetry of the patient’s head with respect to the mid-saginal plane of the skull when laying on an SC tomograph. It is determined by the fact that the main lines of the skull, connecting the middle of the tragus of the ear and the outer corner of the eye, are located strictly vertically on both sides. Sections of a computer image in frontal (direct) and axial projections are analyzed.

On an arbitrarily taken slice, on which both eyeballs are displayed, in any department, a horizontal line is crossed that intersects both images (Fig. 1). Chords measuring from the outer to the inner borders of each eyeball are measured along this horizontal. The height of the segments is also measured along perpendiculars extending from the chords to the front borders of the eyeballs.

The magnitude of the displacement of the eyeball is determined by the formula:

where | ε | - the absolute value of the displacement (mm),

and ₁ - the size of the chord of the slice on the tomogram of a healthy eyeball (mm),

and ₂ - the size of the chord of the slice on the tomogram of the displaced eyeball (mm),

h ₁ - the height of the slice segment on the tomogram of a healthy eyeball (mm),

h ₂ - the height of the slice segment on the tomogram of the displaced eyeball (mm).

Example.

Patient G., born in 1961, was admitted to the TsNIIS clinic with post-traumatic deformation of the middle third of the facial skull after a traffic accident that took place 2 years before admission. There is a change in the proportions of the face due to the displacement of the zygomatic bone and retraction in this zone. The right nasal bone is rotated and causes retraction of the back of the nose. In profile, the nose is shortened. Difficulty breathing through the nose. The upper jaw is displaced back, closing of teeth is broken. The right lower orbital margin is deformed. The eyeball on the right is lowered and shifted back.

On spiral computed tomograms produced with a slice thickness of 1 mm and an interval between slices of 1 mm, the following was found.

The patient has damage to the bottom of the right orbit of the cheek-eye complex. When calculating the magnitude of enophthalmos and hypophthalmus of the right eyeball on sections of a computer tomogram, the following data were obtained.

In axial projection:

h ₁ = 8.5 mm, and ₁ = 22.7 mm, h ₂ = 2.2 mm, and ₂ = 8.1 mm.

Thus, the hypophthalmus was 3.4 mm.

In the frontal projection:

h ₁ = 5 mm, a ₁ = 17.9 mm, h ₂ = 3.33 mm, and ₂ = 11.6 mm.

Thus, enophthalmos was 4.6 mm.

After surgery during the control study during the first week, these indicators were 0.5 mm and 0.72 mm, respectively. Three months later, the symmetry of the eyeballs was fully restored.

Thus, the advantages of the proposed method are expressed in that it can be used for deformations of the bones of the middle zone of the face and it provides a high degree of accuracy in determining enophthalmos, hypophthalmos, or a combination thereof.

Claims (2)

1. The method of determining the displacement of the eyeball, characterized in that they conduct a spiral computed tomography of the facial skull, get a slice of the image in the frontal and / or axial planes, which spend an arbitrary horizontal intersecting the image of both eyeballs, measure the chords from the outer to the inner borders images of each eyeball and the height of the segments and calculate the amount of displacement according to the formula

where | ε | - the absolute value of the displacement (mm); and ₁ - the size of the chord of the slice on the tomogram of a healthy eyeball (mm); and ₂ - the size of the chord of the slice on the tomogram of the displaced eyeball (mm); h ₁ - the height of the slice segment on the tomogram of a healthy eyeball (mm); h ₂ - the height of the slice segment on the tomogram of the displaced eyeball (mm). 2. The method according to claim 1, characterized in that the thickness of the image slice and the interval between the slices of a spiral computed tomogram are 1 mm.