Hemianopia

Introduction Partial hemianism: Medical terminology refers to the partial diagnosis of a part of the visual field. The hemianopia caused by visual pathological lesions often contributes to the localization diagnosis of neuropathy. When the optic chiasm is oppressed by the tumor, it often causes typical bilateral hemianopia. Some ophthalmic diseases can also cause hemianopia-type visual field defects, such as nasal visual field defects in advanced glaucoma, blunt-type visual field defects in retinal vascular occlusion, and visual field defects in the opposite direction when the retina is partially detached.

Cause

When the optic chiasm is oppressed by the tumor, it often causes typical bilateral hemianopia. Some ophthalmic diseases can also cause hemianopia-type visual field defects, such as nasal visual field defects in advanced glaucoma, blunt-type visual field defects in retinal vascular occlusion, and visual field defects in the opposite direction when the retina is partially detached.

There are two types of visual field defects:

1 sacral hemianopia: If the bilateral nerve conduction to the nasal retinal vision caused by tumor compression is involved, bilateral stimuli may not be accepted and bilateral sacral hemianopia may occur. When the tumor grows up, the side loses its visual function due to the weight on one side, and the other side is blind, and the other side is unilaterally blind.

2 omnidirectional hemianopia: damage to the pathway after the optic tract or the lateral geniculate body can produce a visual field defect on one side of the nasal side and the other side of the iliac crest, which is called co-directional hemianopia. The visual beam is different from the central hemianopia. The former is accompanied by the disappearance of light reflection, and the latter has light reflection. The former is blunt and complete, while the latter is more incomplete and quadrant hemian; the former patient's subjective sensory symptoms are more significant than the latter. No self-conscious symptoms; the latter's visual field center of vision is preserved, showing macular avoidance.

an examination

Related inspection

Eye and sacral area CT examination blood routine

CT examination of the eye and temporal area:

CT examination of the eye and temporal region is a method of examining the eye and temporal region by CT.

The CT scan provides a high-resolution, cut-off image and gray-scale eye image that displays the human-level image with X-rays as an energy source. At present, CT has become very popular, providing a superior examination method for the diagnosis of ophthalmic diseases. However, for various reasons, there are still many problems in CT analysis and diagnosis of ocular lesions. Diagnostic ultrasound for intraocular disease is superior to CT, and CT is superior to ultrasound in the diagnosis of orbital lesions. This article discusses some of the problems in CT diagnosis of orbital lesions, and introduces the basic knowledge of CT related to diagnosis, which is very important for comprehensive analysis of ocular CT films.

1. Eye CT scanning method:

Transverse scan

The patient was placed on the supine examination bed, and the top side of the 1cm skull below the ear line was continuously scanned. The level of the 5 mm thick layer of the straight axis required 6 to 8 layers. For thin layer scanning (1 mm layer thickness), nearly 40 layers are required for all eyelids.

b. Coronal scan

The patient is supine or prone on the examination table, and the head is over-extended so that the sagittal line of the head is consistent with the bed surface. The ear lines on both sides are perpendicular to the scanning baseline, and the front ear canal is continuously scanned 4 cm in front of the ear canal, and the layer thickness is 4 to 5 mm). For CT scan of intraocular lesions, the eyeball begins to scan backwards.

c. Contrast Enhancement Method The method of intravenous administration of the contrast agent is to inject the contrast agent within a few minutes, and then start the scan after the full amount of the injection is completed.

d. neck examination

Intra-arterial varices are often not developed during routine CT scans, or only a small part of the lesions are displayed. Wrap the sphygmomanometer bag around the patient's neck, position it, pressurize it to 5.33 kPa (higher than the venous pressure), and then scan it. The balloon will be relaxed immediately after the scan.

e. Optic nerve and optic nerve scanning methods

Sometimes a detailed CT examination is required for detailed observation of optic neuropathy (tumor, trauma, etc.). First, a 1mm thin layer is needed, because the normal optic nerve is about 4mm thick, and the thicker layer is not conducive to analysis. The second special scanning angle is to make a scan line with a negative 15° to the ear line, and then let the patient's eye look upwards. At this time, the optic nerve is straight and parallel with the scan line. CT can observe the optic nerve on one level. The length of the inner section or even the inner section of the tube.

2. CT scan thickness of the eye

The thickness of the conventional ocular CT scan is 5 mm, and the normal height of the normal eyelid is about 40 mm. Therefore, the general horizontal scanning of 8 layers can include all the intraocular structures. The lesion in the iliac crest is large in size and is suitable for a scanning surface of 5 mm thickness. However, in some special cases or lesions requiring thinner thickness scanning, such as intrabulbar lesions, extraocular muscle lesions, optic neuropathy, or estimated lesion diameter less than 5mm, 3mm or 1mm layer thickness scan is required, otherwise the thickness is thick. Small, and only one level shows lesions, which is not conducive to diagnosis and analysis, and may even miss the display of lesions. Since the thin section is less affected by the volume average, the image resolution is improved, and the lesion is more clearly displayed.

intraocular pressure:

Diagnosis of glaucoma detection methods.

Ophthalmoscopy: Fundus examination should be performed in a dark room. The patient takes a seat and the doctor can take a seat or stand. The right hand held ophthalmoscope is located on the right side of the patient.

Differential diagnosis

1 sacral hemianopia: If the bilateral nerve conduction to the nasal retinal vision caused by tumor compression is involved, bilateral stimuli may not be accepted and bilateral sacral hemianopia may occur. When the tumor grows up, the side loses its visual function due to the weight on one side, and the other side is blind, and the other side is unilaterally blind.

2 omnidirectional hemianopia: damage to the pathway after the optic tract or the lateral geniculate body can produce a visual field defect on one side of the nasal side and the other side of the iliac crest, which is called co-directional hemianopia. The visual beam is different from the central hemianopia. The former is accompanied by the disappearance of light reflection, and the latter has light reflection. The former is blunt and complete, while the latter is more incomplete and quadrant hemian; the former patient's subjective sensory symptoms are more significant than the latter. No self-conscious symptoms; the latter's visual field center of vision is preserved, showing macular avoidance.

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