Ophthalmoplegia

Ophthalmoplegia is a disorder of the eye's movement; it can be caused by one or more factors.

1. New formation of the orbit.
2. Restrictive myopathy in thyroid eye disease or orbital myositis.
3. Lesions of the oculomotor nerve in carotid-cavernous fistula, Tolosa-Huni syndrome and malignant tumors of the lacrimal gland.
4. Pinching of extraocular muscles or fascia in a rupture fracture.
5. Splitting of the optic nerve fibers by a meningioma of its sheath.

Difference between restrictive and neurological ophthalmoplegia

The following tests may help differentiate restrictive motor dysfunction from neurological dysfunction.

Forced displacement test

• instill drops of anesthetic;
• moisten cotton swabs with anesthetic solution and place them on both eyes in the area of the muscles being examined for 5 minutes;
• Use tweezers to grasp the muscle of the affected eye at the point of attachment and rotate the eye in the direction of limiting mobility.
• repeat the test for the fellow eye.

Positive: Difficulty or inability to move the eye suggests a restrictive cause such as thyroid myopathy or muscle entrapment at the fracture site. There is no resistance to movement on the opposite side unless the process is bilateral.

Negative result: resistance will not be observed in both eyes in case of neurological pathology and muscle paresis.

Intraocular Pressure Difference Test

• intraocular pressure is measured with the eye in its normal position;
• The measurement is repeated in the position of the eye when trying to look in the direction of limited mobility.

Positive result: an increase in intraocular pressure of 6 mm Hg or more indicates that the resistance is due to muscular restriction.

Negative result: an increase in intraocular pressure of less than 6 mm Hg suggests neurological pathology.

Mild pulsation is best detected by slit-lamp examination and especially by applanation tonometry.

The advantage of this test compared to the forced displacement test is less discomfort for the patient and a more objective result.

Saccadic eye movements in neurological processes are characterized by a decrease in speed, whereas with restrictive defects, sudden stops are observed at the normal speed of this type of movement.

Causes of visual impairment

1. Exposure keratopathy is the most common cause of visual impairment and is secondary in nature due to severe exophthalmos combined with lagophthalmos and impaired Bell's phenomenon.
2. Compressive optic neuropathy is characterized by signs of intraocular pressure disturbance: decreased visual acuity, impaired color vision and contrast sensitivity, visual field defects, impaired afferent conduction, and changes in the optic disc.
3. Choroidal folds in the macular area can sometimes cause visual disturbances.

Dynamic characteristics

The following dynamic signs can help in diagnosing the pathology.

1. Increased venous pressure with a certain head position, Valsalva maneuver, or jugular vein compression may lead to the appearance or increase of exophthalmos in patients with venous anomaly of the orbit, and also serve as a sign of capillary hemangioma of the orbit in children.
2. Pulsation, which may be caused by an arteriovenous anastomosis or a defect in the orbital vault.
   • In the first case, the pulsation is accompanied by noise depending on the size of the defect.
   • In the latter case, the pulsation is transmitted from the brain by the cerebrospinal fluid and is not accompanied by noise.
3. The noise is characteristic of a carotid-cavernous fistula. It is best heard with a stethoscope and decreases or disappears when the ipsilateral carotid artery is compressed.

Changes in the optic disc

1. Atrophy of the optic nerve, which may be preceded by its edema, is a manifestation of severe compression optic neuropathy. The main causes are thyroid eye disease and optic nerve tumors.
2. Opticociliary shunts consist of dilated, normally existing parapapillary capillaries that shunt blood from the retinal venous system into the parapapillary choroid when normal drainage pathways are occluded. On ophthalmoscopy, the vessels, most often in the temporal half, are dilated and tortuous and disappear at the edge of the optic disc. Rarely, this picture can be observed with an orbital or optic nerve tumor that compresses the optic nerve in the orbit and disrupts the outflow of blood from the central retinal vein. Shunts are most often seen with optic nerve sheath meningiomas, but can also be seen with optic nerve gliomas and cavernous hemangiomas.

Choroidal folds

This is a group of parallel alternating light and dark delicate lines and striae, most often located at the posterior pole. Choroidal folds are observed in various orbital pathologies, including tumors, dysthyroid ophthalmopathy, inflammatory processes, and mucoceles. The folds are usually asymptomatic and do not lead to deterioration of vision, although in some patients there is a shift in refraction towards hyperopia. Although choroidal folds are most often associated with significant exophthalmos and tumors of anterior localization, in some cases their appearance may precede clinically significant exophthalmos.

Changes in the retinal vessels

1. Tortuosity and dilation of veins is characteristic of arteriovenous anastomoses.
2. Venous dilation may also be associated with stagnation of the disc in patients with an orbital mass.
3. Vascular occlusions can be observed in carotid-cavernous fistula, orbital cellulitis, and optic nerve tumors.

Special research methods

1. CT is useful for characterizing bone structures, localization and size of space-occupying lesions. It is especially valuable in patients with orbital trauma, as it helps to detect even minor cracks, foreign bodies, blood, extraocular muscle hernia and emphysema. However, CT is of little use in differentiating various soft tissue structures that have the same radiographic density.
2. MRI can visualize processes at the orbital apex and extension of orbital tumors into the cranial cavity. STIR - fat suppression mode in Tl-weighted tomography - is very valuable for determining the activity of the inflammatory process in thyroid eye disease.
3. Radiographs have partially lost their significance with the advent of CT and MRI. There are 2 main projections:
   • Caldwell projection, in which the patient's nose and forehead touch the film. It is most often used for orbital lesions;
   • The Waters projection, with the patient's chin slightly elevated, is useful in diagnosing inferior orbital wall fractures.
4. Fine-needle biopsy is performed under CT guidance using a needle. This technique is especially necessary for patients with suspected orbital metastases and when tumors from adjacent structures invade the orbit. Complications such as hemorrhage and perforation of the eye are possible when performing a biopsy.

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