radiation cataract
Introduction
Introduction to Radiation Cataract Clinically, there will be clear evidence that cataract caused by radiation is called radiationcataract. The subepithelial cells of the lens equatorial region are very sensitive to ionizing radiation. The damaged epithelial cells can produce granular substances in the capsule. The membrane migrates from the peripheral portion to the center, especially in the posterior pole. basic knowledge The proportion of illness: 0.06% Susceptible people: no special people Mode of infection: non-infectious Complications: ball adhesion radiation sickness
Cause
Causes of radiation cataract
Causes:
The lens is highly sensitive to the effects of radiation. The cataract caused by radiation is called radiation cataract. There are two kinds of lens injured people, one is the worker who touches the radiation, and the other is the radiation therapy. Radiation: X-ray, radium ray, 60Co, 90Sr , -ray, and neutron rays of krypton, xenon, krypton, infrared, ultraviolet and microwave.
Pathogenesis:
1. Pathogenesis: Radiation cataract occurs and develops in two aspects: 1 direct radiation of direct radiation to the lens; 2 radiation and other effects on the iris ciliary muscle vascular system, resulting in dynamic changes in aqueous humor circulation, thereby reducing the lens in Gas exchange in aqueous humor, both directly or indirectly affect the occurrence and development of cataracts.
In the epithelial cells of the growth zone under the anterior capsule of the lens, after being subjected to ionizing radiation, the nucleus is damaged, causing degeneration, chromosomal abnormalities, nuclear fragmentation, and cell mitosis are significantly inhibited. These damaged epithelial cells move to and accumulate in At the posterior part of the lens, such as by slit lamp microscopy, the examiner can see opaque spots, such as damage further development, damage caused by denatured cells can accumulate in the posterior lens of the opaque ring, lens fibrosis, the entire lens change turbid.
2. Threshold dose of cataract: Merrian et al studied the relationship between radiation cataract and dose, and concluded that X-ray or -ray resulted in the lowest radiation dose of cataract, with a single exposure of 51.6 mC/kg; 3 weeks to 3 months. The cumulative amount of multiple exposures is 103.2 mC/kg; the cumulative amount of multiple exposures over 3 months is 141.9 mC/kg; if the total amount of irradiation exceeds 296.7 mC/kg, regardless of the number of exposures and the length of time elapsed, Cataract, there is no uniform value for the threshold dose of cataract caused by beta rays.
Prevention
Radiation cataract prevention
Radiation cataract is the result of some kind of radiation acting directly on the lens. Therefore, medical personnel must take precautionary measures so that the external dose does not exceed the national standard of protection. In addition, in order to prevent radiation damage to the lens, radiation workers should wear it. Lead protective glasses.
Complication
Radiation cataract complications Complications, sacral adhesions
Orbital radiation dermatitis, acute pseudomembranous conjunctivitis, symblepharon adhesions, corneal ulcers, retinal radiation damage, acute radiation sickness, etc.
Symptom
Radiation cataract symptoms Common symptoms Visual impairment Seeing things have a ghost
1. The incubation period of cataract formation
The lens has the same performance after various radiation injuries. After receiving radiation, the incubation period varies. It can be several months, years or decades. It is related to the type of radiation received, the amount of radiation and the age. X-ray causes The onset is 2 to 4 years, and the neutron ray can cause symptoms in a few months. In short, the younger the age, the shorter the incubation period; the larger the dose, the shorter the incubation period; the conditions are different and the difference is very large.
2. Clinical morphology of cataract
The clinical morphology of cataract caused by X-ray, -ray and neutron irradiation is basically the same. The clinical process of human radiation cataract can be divided into four stages:
The first stage: several powdery turbid spots appear in the posterior capsule of the posterior lens, or white, gray, gold, iridescent, and small vacuoles in the posterior capsule. This stage does not cause visual impairment.
The second stage: After a period of time, the turbid small points gradually increase and accumulate to form a ring. When the turbid area is enlarged to a diameter of 1 to 2 mm, it is seen that there are vacuoles and particles scattered around it, and then the turbidity is expanded into a disk-like turbidity. 3 to 4 mm.
The third stage: longer time, more turbidity under the posterior capsule, gradually forming a disc shape, irregular shape, sometimes in the form of several layers of overlap, the disc-shaped turbidity gradually expands toward the equator and before and after, while the lens cortex occurs from the equator The wedge-shaped turbidity that extends toward the center sometimes occurs earlier from the turbidity in the center than in the central part, and the surrounding turbidity is often yellow-brown.
The fourth stage: the lens is completely turbid and cannot be distinguished from senile cataract.
Examine
Radiation cataract examination
1. Eye special examination
There are doubts or special requirements for the surgical results, and patients suspected of having other eye diseases should be examined.
(1) Corneal endothelial cell examination: observe the ratio of cell density (CD) and Hexagocyte (Hexagocyte). When the corneal endothelium is lower than 1000/mm2, the cataract surgery should be carefully considered to avoid postoperative cornea. Decompensation affects the surgical outcome and postoperative recovery.
(2) Retinal visual acuity test: a specific image or visual target is projected onto the retina, regardless of whether the refractive interstitial is turbid, directly check the visual acuity of the retina to understand the best visual acuity that can be achieved after the patient is operated, and is a preoperative evaluation of the macula. An important check method for function.
(3) Visual field examination: For patients with light opacity of the lens and a certain vision, other diseases with cataract can be found by visual field examination. For example, the central dark spot should be alert to the presence of macular degeneration, the expansion of physiological blind spots and the characteristic of visual field. Defects should be alert to the presence of glaucoma and other fundus lesions. Because cataracts can also cause changes in visual field, they should be identified by contacting the opaque area of the lens observed by the slit lamp.
(4) Retinal current map (ERG) examination: There are currently 3 kinds of ERG, such as flash, graphic and multi-focal, which can record the cone function of the retina, rod function and mixed function. The flash ERG reflects the function of the whole retina, graphic ERG mainly reflects the function of the macula. Multifocal ERG can simultaneously record ERG on more than 100 retinal sites in the central 30° field of view, which is conducive to the diagnosis and judgment of postoperative retinal function. The clinical application of flash ERG is as follows. Preoperative ERG was normal or slightly reduced, and postoperative visual acuity recovery was estimated to be good. If preoperative ERG was significantly reduced or not recorded, postoperative visual recovery was estimated to be unsatisfactory.
(5) Visual evoked potential examination (VEP): VEP includes flash VEP and graphic VEP for recording the function of the nerve pathway from the retina to the visual cortex. When the macular and optic nerves appear lesions, they can show amplitude reduction and latency. Prolonged, when the patient's preoperative visual acuity is less than 0.1, the flash VEP examination is generally used, and when the patient's visual acuity is good, the visual VEP examination can be used. Therefore, when the lens is obviously turbid, the VEP examination has a more accurate degree of recovery of postoperative visual function. Predictive.
2. Other related auxiliary examinations of the whole body
It is related to the time and dose of exposure to radioactivity.
Diagnosis
Diagnostic identification of radiation cataract
diagnosis
1. The patient has a history of exposure to radiation.
2. After exposure to radiation, the patient developed visual impairment, but later.
3. Chronic X-ray and other radiation damage to the lens, turbidity mostly begins from the posterior pole. There may be posterior subcapsular vesicle vesicles in the posterior capsule, haze turbidity in the posterior capsule and flaky opacity in the posterior capsule. Occurs, but mostly mixed.
4. The posterior capsule subcortex appears in vacuoles. The vacuoles are small and round, or remain unchanged for a long time, or become a small white spot through cheese, which cannot be absorbed by themselves and gradually expands toward the front and the equator.
5. For a long time, the cortical opacity of the posterior capsule is mostly foggy and dotted, and the whole is thin and round. The initial is limited to the radius of 2mm near the posterior pole, and is close to the posterior capsule and far from the nucleus.
6. Lens lesions can occur alone or with other eye damage.
Differential diagnosis
1. High myopic posterior capsule cortical opacity: often brown, and the cortex is completely turbid from the back of the nucleus.
2. Diabetes-caused lesions: Although it can be located under the posterior capsule, it does not reach the posterior pole. It is characterized by small and round shape, and the vesicles are stable in shape and long-term unchanged.
3. Concurrent with opacity of retinitis pigmentosa and uveitis: often have knee-like dust spots, not disc-shaped.
4. Age-related cataracts: Most of them have a wedge-like opacity in the peripheral cortex.
