metabolic cataract
Introduction
Introduction to metabolic cataract Metabolic cataract is related to the metabolism of the lens. As the blood sugar increases, the glucose content of the lens increases, resulting in an increase in aldose-reducing plum activity. Glucose is converted into sorbus, sorbitol is accumulated in the lens, the osmotic pressure is increased, and the lens absorbs water. The formation of fiber swelling and denaturation results in turbidity. basic knowledge The proportion of illness: 0.3%-0.5% Susceptible people: no specific population Mode of infection: non-infectious Complications: Retinopathy Iris neovascularization Chronic progressive extraocular muscle paralysis
Cause
Causes of metabolic cataract
Diabetes (62%):
The resulting blood sugar rises. The mechanism of diabetic cataract has not yet been finalized, but an in-depth study of experimental diabetic cataract animal models found that there is a disorder of glucose metabolism in the lens, which is an important biochemical and pathological basis for the formation of cataract. The lens utilizes glucose through four metabolic pathways. The three pathways (glycolysis, pentose branch, tricarboxylic acid cycle) depend on the rate of conversion of glucose to glucose-6-phosphate, catalyzed by hexokinase, as a complementary metabolic pathway, in aldose reductase ( Aldose reductase catalyzes the conversion of glucose to sorbitol, which is further catalyzed by polyol dehydrogenase to produce fructose. Under normal conditions, hexokinase is more aldehyde than aldehyde. The sugar reductase has higher activity, the sorbitol pathway has almost no effect, and in diabetic patients, the blood sugar level is increased, and it can rapidly diffuse into the lens through aqueous humor to saturate the hexokinase activity and activate the aldose reductase. Excessive glucose is converted to sorbitol and fructose by the sorbitol pathway. When it is produced in the lens, it will not easily ooze out through the capsule, which will cause sorbitol to accumulate in the lens, increase the osmotic pressure of the lens, and excess water will enter the lens to maintain the balance of osmotic pressure, resulting in the formation of vesicles, water gaps and lamellar layers. Separation and other pathological changes, such as further aggravation, individual lens fibers rupture, sodium ions released into the lens, causing further water absorption, while the components inside the lens leak, making potassium, glutathione, amino acids and small molecules The protein is partially lost, which in turn produces opacity of the lens cortex and nucleus.
Prevention
Metabolic cataract prevention
Early onset, rapid progression, and mature senile cataracts should be checked for diabetes. When performing cataract surgery on patients with diabetes, it is necessary to control blood sugar and actively prevent infection and bleeding after surgery.
Complication
Metabolic cataract complications Complications retinopathy iris neovascular chronic progressive extraocular muscle paralysis
Diabetic retinopathy (DR), iris neovascularization, extraocular muscle paralysis, etc.
Symptom
Metabolic cataract symptoms Common symptoms Lens opacity edema Lens expansion increases ocular fissure oblique pupil whitening
Diabetic cataracts begin with the formation of small anterior subcapsular vesicles. In younger patients, these small vacuoles can rapidly develop into a typical gray-white patchy opacity, located in the anterior and posterior subcapsular cortex. The morphology is described as "like a little snow fluttering on the lead gray sky background" is very appropriate, and then, as the disease progresses, the lens finally falls into a comprehensive turbid state. During the progression of diabetic cataract, the characteristic pathological change is the rapid occurrence of the matrix. The high degree of edema, the formation of a large amount of water gap, the result of increased lens swelling, in any diabetic patients, especially young people, regardless of the presence of lens opacity, rapid increase in blood sugar can lead to significant myopia, such as rapid reduction of blood sugar to normal , there can be hyperopia, these changes can reach a peak in a few days, and it takes several weeks to return to normal refractive state.
Examine
Examination of metabolic cataract
Blood biochemical examination of blood glucose levels and glycosylated hemoglobin quantification, to determine the condition of diabetes.
1. Special eye examinations have doubts or special requirements for the surgical results. 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.
Diagnosis
Diagnosis and diagnosis of metabolic cataract
1. History of diabetes;
2. Vision loss;
3. The lens is turbid, snow flake turbidity is its characteristic, and sometimes turbidity spreads rapidly;
4. Laboratory tests such as blood sugar and urine sugar are consistent with changes in diabetes.
According to the age of onset of the patient, there is a history of diabetes, and the condition of the eye lesion can be clearly diagnosed.
The main distinguishing point from other metabolic cataracts such as galactose cataracts and low-calcium cataracts is the difference in systemic clinical manifestations of patients.
