Visual impairment

Introduction Eye functions include shape, color perception, and light perception. Vision is a function that more accurately represents the shape and can be divided into central vision and peripheral vision. Central vision is obtained through the center of the macula, which refers to retinal function outside the macula. Therefore, vision is one of the specific manifestations of visual function. Visual impairment, although very mild, also indicates that vision function has been affected.

Cause

First of all, we should understand the path from the retina to the visual information, to the entire nerve impulse that forms the vision in the visual cortex of the brain, that is, the visual path. The nerve fibers from the retinal ganglion cells are collected into the optic nerve through the scleral sieve. In the optic nerve segment, the fiber fibers from the retina and the temporal side of the retina, to the optic chiasm, the nerve fibers in the nasal part of the retina cross each other to the opposite side, and the nerve fibers of the retinal side of the retina that do not intersect with the lateral optic nerve constitute a visual bundle. Stretching the person to the lateral geniculate body, after exchanging the neurons, they enter the human eye and then enter the visual cortex of the occipital lobe through the inner capsule. When light hits the human eye, the refraction of the ocular refractive system (corneal, crystal, vitreous) focuses on the retina, through the ganglion cell layer and the bipolar cell layer, reaching the photoreceptor layer, which is rich in photoreceptor cells. The photosensitive substance of the combination of vitamin A and protein, called photoreceptor (rhodopsin and rhodopsin), produces a series of photochemical changes under the action of light - fading decomposition, and produces energy, will Light energy is converted into electrical energy, and a potential is generated, which in turn causes visual impulses, which are transmitted through the visual path and reach the visual center of the cortex of the posterior occipital lobe of the brain to produce vision. Therefore, some reasons, such as inflammation, trauma, tumors, vascular diseases, etc., can cause visual impairment in any part of the lesion from the cornea to the occipital lobe.

The lesions that cause visual impairment are extensive, and the causes of visual impairment are also diverse.

1. Inflammation is the most common cause of visual impairment.

(1) Infectivity: keratitis, corneal ulcer, iridocyclitis, choroiditis, endophthalmitis, total ocular inflammation, orbital cellulitis caused by bacteria, viruses, chlamydia, fungi, parasites, and the like.

(2) Non-infectious: vesicular keratitis, keratitis, uveitis (including iridocyclitis, choroiditis), sympathetic ophthalmia, Harada disease, Behcet's disease, etc.

2. Refractive error: myopia, hyperopia, astigmatism, presbyopia.

3. Strabismus, amblyopia.

4. Eye trauma: Eyeball perforation, blunt contusion, blast injury. Chemical burns, radiation injuries, etc.

5. Glaucoma

6. After-effects caused by various eye diseases: corneal scar, pupillary membrane closure, pupillary atresia, vitreous opacity.

7. Systemic circulatory disorders and metabolic disorders as well as various eye diseases caused by hereditary diseases: hypertensive retinopathy, diabetic retinopathy, nephritic retinopathy, pregnancy-induced hypertension retinopathy, hematologic retinopathy, Retinal pigmentosa, macular degeneration, ischemic optic neuropathy, Leber disease and other fundus lesions, diabetic cataract.

8. Retinal vascular disease and retinal detachment: retinal artery occlusion, retinal vein occlusion, middle serous chorioretinopathy, retinal vasculitis, retinal detachment, etc.

9. Senile and degenerative diseases: senile cataract, corneal degeneration, age-related macular degeneration.

10. Tumor: Intraocular tumor, orbital tumor or eyelid tumor that invades the eyeball.

11. Others: visual path lesions, fraud.

an examination

Related inspection

Adrenal MRI examination of arterial oxygen partial pressure (PaO2). Ultrasound examination of the eye and eyelids by brain ultrasonography and CT examination of the temporal region

Patients complain of vision loss, first of all should know the exact vision, including far vision and near vision, in addition to refractive errors and presbyopia. If the distance and near vision are not good, you should see if there is any redness, that is, ciliary congestion. If there is ciliary congestion, keratitis, iridocyclitis (including trauma), and angle-closure glaucoma should be considered. If there is no ciliary congestion, check the refractive interstitial for turbidity, such as corneal epilepsy, degeneration, cataract, vitreous opacity. Or open angle glaucoma, fundus lesions. Through the fundus examination, the retina, choroid, and optic neuropathy can be clarified. If the above lesions are not obvious, it is necessary to pass the visual field examination to exclude the visual path lesions. If they are all negative, amblyopia should be excluded. Of course, it is necessary to comprehensively analyze the other symptoms in the main complaint. Therefore, it is very important to ask in detail about the medical history and to gradually and carefully examine it from front to back.

First, medical history

Ask in detail about the occurrence and development of visual impairment. Whether the visual impairment is monocular or binocular; it occurs simultaneously or sequentially; whether it occurs rapidly or gradually; it is poor distance vision, or poor nearsightedness, or poor near and far vision. Are there other symptoms, such as eye congestion, shame, tearing, pain, to exclude keratitis, iridocyclitis. Headache, eye swelling, fog vision, and rainbow are considered as except for glaucoma. Monocular double vision, considering the opacity of the cornea, crystal, and vitreous midline. The crystal is subluxated. Dark spots, color vision, small vision, night blindness, visual distortion, visual field defects, black shadows in front of the eyes, flashing sensation, etc. should be considered for fundus lesions. And pay attention to the history of trauma.

Second, physical examination

Visual impairment can be caused by systemic diseases, so a comprehensive physical examination is very important. In particular, attention should be paid to the examination of systems such as nerves, cardiovascular and endocrine. Eye examination: The examination must be performed systematically and comprehensively from the outside to the inside of the eye. Right and then left to prevent missing important signs.

(1) Vision

Vision includes far vision and near vision, as well as a preliminary impression of visual impairment. Poor vision, near vision, may be myopia, astigmatism and so on. Poor near vision, good distance vision, may be hyperopia. Those over the age of 40 are considered to be presbyopia. Far and near vision are not good, can be hyperopia or astigmatism, or refractive interstitial opacity, fundus or optic neuropathy, intracranial lesions. If there is ciliary congestion, keratitis, iridocyclitis, and glaucoma should be considered. A sudden visual impairment, which may be a central retinal artery occlusion, ischemic optic neuropathy. Visual acuity rapidly diminish within a few days, possibly central retinal vein occlusion, retinal detachment, vitreous hemorrhage, eye and craniocerebral trauma, poisoning, acute intracranial lesions, etc. No light perception may be caused by optic atrophy and eyeball atrophy. Eyeballs, absolute glaucoma, cortical blindness, etc. After giving a preliminary impression of the above-mentioned vision, it should be checked step by step from the front to the back according to certain steps.

(two) external eye examination

1. Eyelids: General eyelid lesions rarely cause visual impairment, and visual impairment occurs only when the eyelid lesions cause irritation. Such as intraocular lens, valgus, trichiasis, conjunctival calculus, blepharitis, and the formation of epilepsy.

2. Eyelids and eyeballs: Is the eyeball protruding and depressed? Is there any abnormality in the position of the eyeball? Whether the sacral can touch the mass, the eyeball rotation is limited.

3. Cornea: size, with or without vasospasm, infiltration, ulcers, scars, degeneration, foreign bodies, deformities.

4. Anterior room: The depth of the room, the degree of turbidity of the aqueous humor, and the presence or absence of empyema. Blood, exudate.

5. Iris: color, texture, with or without defects (congenital, surgical) with no nodules, atrophy, anterior and posterior adhesions, neovascularization, tremor (note the contrast of both eyes).

6. Pupil: shape, size, edge, photoreaction (direct, indirect, convergent). Whether there are exudates or pigments in the pupil area.

7. Crystal: presence, location and transparency.

(3) Vitreous and fundus examination

Check with direct or indirect ophthalmoscope in a dark room. Observe the vitreous for turbidity, hemorrhage, liquefaction, degeneration, foreign bodies, parasites, and the like. Check the fundus should pay attention to the optic disc, retinal blood vessels and macular and the entire fundus, with or without inflammation, bleeding, exudation, degeneration, deformity and so on.

(4) Special inspection

1. Slit lamp microscopy: The microscopic changes in the tissues of the eye can be further observed. Pay attention to the fine lesions of the cornea, aqueous humor, crystals and anterior vitreous. Combined with corneal staining (2% fluorescein solution staining) to identify fresh and old lesions of the cornea. The changes of anterior chamber angle were observed by anterior chamber angle mirror, and the changes of various parts of the fundus were observed by three-sided mirror.

2. Vision: Includes central and peripheral vision to understand functional changes in the optic nerve, retina, and visual pathway.

3. Reconnaissance, audition: understand the refractive status.

4. Measurement of intraocular pressure and eyeball protrusion: Intraocular pressure measurement of glaucoma is indispensable, but for the diagnosis is difficult to determine, it is necessary to further make 24 h day and night intraocular pressure curve, water flow elapsed C value and eye Pressure excitation test.

Third, laboratory inspection

In order to confirm the diagnosis or investigate the cause, blood pressure, blood, urine routine, erythrocyte sedimentation rate, blood sugar, tuberculin test, thyroid function, pathological examination, etc. have important reference value.

Fourth, equipment inspection

1. Fundus fluorescein angiography: It can further understand the fine structure, dynamic changes and functional changes of fundus blood circulation (up to capillary level), and provide more and more detailed diagnosis basis for fundus diseases.

2. Visual electrophysiological examination: including electroretinogram (ERG), electrooculogram (EOG), visual evoked potential (VEP), etc., to understand the function of the retina and visual pathway.

3. Image examination: including chest and eyelid X-ray examination, ultrasound exploration of type ultrasound (A type ultrasound, B type ultrasound, ultrasound Doppler), CT scan, magnetic resonance imaging (MRI) and so on. It can show the structure of the eye and pathological changes, and the opaque tissue of the eye can achieve direct visual inspection.

Differential diagnosis

Distinguish from the following similar symptoms: Blindness, also known as blindness, refers to a more severe type of visual disability. Narrow refers to the loss of vision to a total lack of light; broadly refers to the ability of a single eye to lose the ability to distinguish the surrounding environment.

Two eyes can't look at one target at the same time, but can only use one eye to look at the other eye's visual axis to show different degrees of skew. This phenomenon is called strabismus. The degree of skewness of the squint can be obtained by measuring the angle between the axes of the two eyes.

Pseudo-Parinaud syndrome is the most characteristic manifestation of nuclear damage. The lesion side is completely oculomotor palsy with contralateral superiority. Confinement of the contralateral view is due to destruction of the rectus muscle on the lesion side.

It is especially hard to see things; or an object can be seen as two, causing double vision, that is, double vision.

Vertical gaze was paralyzed, and both the patient's random and reflexive vertical gaze disappeared. This was due to the upper apex of the anterior and posterior commissures, and the medial and dorsal infarction of the red nucleus caused the paralysis of the lower eye. If the latter half of the upper part of the hill is damaged, the two eyes cannot be seen.

Patients complain of vision loss, first of all should know the exact vision, including far vision and near vision, in addition to refractive errors and presbyopia. If the distance and near vision are not good, you should see if there is any redness, that is, ciliary congestion. If there is ciliary congestion, keratitis, iridocyclitis (including trauma), and angle-closure glaucoma should be considered. If there is no ciliary congestion, check the refractive interstitial for turbidity, such as corneal epilepsy, degeneration, cataract, vitreous opacity. Or open angle glaucoma, fundus lesions. Through the fundus examination, the retina, choroid, and optic neuropathy can be clarified. If the above lesions are not obvious, it is necessary to pass the visual field examination to exclude the visual path lesions. If they are all negative, amblyopia should be excluded. Of course, it is necessary to comprehensively analyze the other symptoms in the main complaint. Therefore, it is very important to ask in detail about the medical history and to gradually and carefully examine it from front to back.

The material in this site is intended to be of general informational use and is not intended to constitute medical advice, probable diagnosis, or recommended treatments.