Age-related cataract

Introduction to age-related cataracts Age-related cataract refers to the opacity of the lens that begins in middle-aged and elderly people. As the age increases, the prevalence increases significantly. Because it mainly occurs in the elderly, it used to be called senile cataract. Its occurrence is related to various factors such as environment, nutrition, metabolism and genetics. basic knowledge The proportion of illness: 0.15% Susceptible people: more common in middle-aged and elderly people Mode of infection: non-infectious Complications: lens-soluble glaucoma

Age-related causes of cataract

(1) Causes of the disease

Different types of cataracts have different risk factors and pathogenesis. Detailed etiological studies can distinguish the role of different risk factors in the formation of cataract. It is still a complicated and difficult subject, with some risk factors as a certain The formation of different types of cataracts, the establishment of different types of cataract animal models, is a very valuable research method for summarizing the role of many risk factors in the etiology of cataract, although this model has certain limitations, such as it often overlooks The influence of time in the formation of cataract and the complexity of cataract caused by different risk factors, but the role of regularity in revealing the formation and development of cataract is not doubtful.

The occurrence of cataract is the result of a combination of factors, such as radiation and free radical damage; nutrients, chemical deficiency and the use of antibiotics, glucose, galactose and other metabolic disorders, lipid peroxidation damage, etc. In addition, other factors Factors such as aging and genetics are also an important aspect. The most common link is oxidative damage.

(two) pathogenesis

1. Antioxidant system Oxygen free radical damage is the first risk factor of senile cataract. Many experiments have shown that the oxidative damage of the lens occurs before the lens opacity, and various physical and chemical factors can lead to free radical production of the lens through different ways, such as free radicals. Excessive or clearing obstacles can lead to free radical accumulation. The target of free radical damage is lens epithelial cells, followed by lens fibers, which cause protein and lipid peroxidation, cross-linking, denaturation, and accumulation. molecule.

Lens epithelial cells are the active center of antioxidant damage, exerting antioxidant effects through two pathways. The first pathway is scavenging free radicals represented by antioxidants such as reduced glutathione (GSH), vitamin C and vitamin E. Mechanism, the oxidative damage of the lens is the first to show a significant decrease in GSH content, an increase in oxidized glutathione (GSSG), a decrease in the GSH/GSSG ratio, and vitamin C as a free radical scavenger, which can quickly interact with O-, OH- and O2 reaction, generate vitamin C free radicals, vitamin C free radicals are inactive, but prone to disproportionation, the formation of a molecule of vitamin C and a molecule of dehydrogenated vitamin C, vitamin E is a group of isomers, of which alpha-nicotinic acid vitamin E It has the highest activity and can directly interact with O-, OH- and O2 to block lipid peroxidation. The antioxidant enzyme system is another antioxidant barrier of the lens, mainly glutathione peroxidase (GSHpx-1). , catalase (CAT) and superoxide dismutase (SOD), the level of SOD in the lens and serum of elderly patients with cataract is significantly lower than that of elderly non-cataract patients, and the two vigors decrease synchronously, CAT, GSHpx live Significantly decreased lipid peroxidation (of LPO), malondialdehyde (MDA) increased production.

Detection of glutathione transferase (GST) gene by polymerase chain reaction (PCR) revealed that the GST gene deletion rate in senile cataract patients was 6.95%, which was significantly higher than that in the control group. It is considered that the incidence of senile cataract is closely related to GST gene deletion. The deletion of this gene may be one of the genetic factors for individuals suffering from cataract.

The lens contains a variety of photodegradable pigment components, such as N-formyl kynurenine (NFK), 3-hydroxy- kynuric acid (3-OH-FK) -carboline, vitamin B2, flavin gland Mononucleotide (FMN), flavin adenine dinucleotide (FAD), etc., all of which have photosensitizer properties, repeatedly absorbing photons in an excited state, and energy can be transferred to adjacent oxygen molecules to form O-, The photosensitizer returns to the ground state and reciprocates. The free radicals in the crystal form are mainly O-, OH-, H2O2, among which OH-damage is the most serious, but O-, OH- has a short half-life and H2O2 is relatively stable. It can be transferred from one place to another, and disproportionation occurs in the presence of superoxide dismutase (SOD) and transition metals (Fe2, Cu2).

The lens is rich in components such as tryptophan (Trp) and tyrosine (Tyr). When ultraviolet light with a wavelength of 300 nm is absorbed by the lens, tryptophan is activated to form N-formyl kynurenine and other photochemical products. N-formyl kynurenine can produce reactive oxygen free radicals through multiple pathways, and the photosensitizer produced causes the lens to produce non-tryptophan blue fluorescence and pigment, which changes the color of the lens, which may be a brown or brown nucleus. The basis of cataracts.

The crystal fiber content of the lens fiber is rich. These proteins are composed of amino acids rich in sulfhydryl groups, which are easily damaged by oxidation. The oxidized damaged fiber cells are gradually squeezed to the center, and the photochemical products of proteins gradually become difficult to accumulate, and the accumulation of photochemical products is gradually accumulated. Further aggravating the absorption of light near the UV spectrum, resulting in photochemical reactions producing more oxygen free radicals, protein damage eventually leading to pigmentation and loss of light transmission, lens fibers at the core, the most aging in the lens Fiber, protein synthesis ability is almost lost, after racemization, glycosylation, carboxy terminal degradation, deamination and non-covalent bond aggregation and other post-transcriptional modifications, protein conformation changes significantly, in addition, in the core of the old fiber The expression of lens protein gene, and the expression of fiber in the outer part of the outer layer, the crystal protein composition will also change significantly, and the activity of the active metabolic component in the lens is reduced. Therefore, the core lens of the old part is the easiest. It is oxidized and turbid.

2. The protein and other components in cataracts change the light transmittance and diopter of the lens, which is related to the content of water-soluble lens structure protein. Most cytoskeletal proteins are mainly involved in the elongation and maturation of fiber cells, but not related to lens transparency. Growth and temperature decrease, -crystallin is prone to agglutination, and structural changes in this protein can cause light to scatter, thereby affecting the transparency of the lens.

With the increase of age, the content of water-soluble protein (WSP) in the lens decreased, the content of insoluble protein (WIP) increased, the main intrinsic polypeptide (MIP) decreased, and the content of -crystallin in WSP increased relatively. -, -crystallin content decreased, further analysis found that 1, 2, 3 lens protein, 1-crystallin content decreased most significantly, because the lens protein contains more cysteine (Cys), easy to form after H2O2 damage High molecular weight (HM) protein, high molecular weight protein is transformed into insoluble urea-soluble protein (USP). Analysis of WSP electrophoresis patterns in children and adults with lens reveals that some cytoskeletal proteins, such as actin, wave shape during fiber cell aging. Degradation of proteins (vimentin), etc., is associated with excessive activation of proteolytic enzymes in fibroblasts.

The lens is rich in free amino acids, including aspartame amino acid, threonine, serine, glutamic acid, alanine, cystine, proline, methionine, isoleucine, leucine and histidine. Etc., their concentrations are higher than those in aqueous water, where glutamic acid and glutathione are higher. Glutathione is a tripeptide containing glycine, cystine and glutamic acid, which is synthesized in the lens. Active to maintain the stability of the lens capsule, when the senile cataract occurs, the free amino acid content in the lens gradually decreases with the development of cataract, especially the reduction of glutamate is significant, further affecting the synthesis of glutathione, when the protein The amino acid of the ligand accumulates to a certain extent, causing the cell membrane to open or the cell membrane to rupture, causing amino acid and soluble components to leak through the lens capsule, protein loss and water accumulation, causing edema, denaturation, and decreased lens transparency of the lens fiber, eventually leading to cataract. form.

In the early stage of cataract formation, lens fibers will undergo a series of morphological changes such as edema, but it does not represent lens protein degeneration. This pathological process is reversible. At this time, if antioxidant drugs are used, the lens edema can be reversed. Treatment of cataract, if the condition is not controlled, once the lens protein cross-links, denaturation, the lesion will become irreversible, then the application of antioxidant drugs is difficult to achieve therapeutic effects.

Lipid changes in senile cataract may also be associated with oxidative damage. Oxygen free radicals cause lipid peroxides such as conjugated diene, triene, and MDA. MDA can form fat-soluble, water-soluble by crosslinking with amino compounds. Serotype 2 fluorescent substances, determination of serum and lens water-soluble fluorescent substances (WSFS) can represent lipid peroxidation levels, WSFS content in the lens of elderly patients with cataract increases with age, while Na-K pump function on the lipid membrane Impaired, lens pump balance damage, water, sodium retention, epithelial cell swelling, and eventually lead to cataract.

The results also confirmed that calcium-calmodulin (Ca-CaM) was abnormal in senile cataract. Under normal conditions, the calcium content in the lens was 100-10000 times lower than that of the anterior chamber fluid, and Ca2 ATPase and Na-K-in the lens epithelial cells. ATPase is also a thiol-containing enzyme, which is very sensitive to oxidative damage. Ca2 and CaM are active in cataract lens, and cAMP phosphorylase (PDE) is Ca2, CaM-dependent, cyclic guanosine monophosphate (cGMP). The PDE is Ca2-dependent, Ca2-CaM regulates cAMP and cGMP in both directions. The two systems interact and coordinate with each other. In the senile cataract, the cAMP content generally decreases, cGMP generally increases, and the cAMP/cGMP ratio decreases. Hydroxyl radicals act to activate guanylate cyclase. The increase of cGMP content is related to excess oxygen free radicals. The decrease of cAMP content is related to adenylate cyclase (AC) on oxygen free attack membrane. AC enzyme activity Decreased leads to decreased cAMP synthesis, Ca2 and ATPase have two parts of CaM and cAMP regulatory regions, cAMP decreases Ca2 -ATPase regulation uncontrolled, Ca2 increases, high calcium activates lens cells Calpain I, II causes abnormal hydrolysis of lens protein, Ca2 can Make Cross-linking between two intact polypeptide chains of -crystallin or its subunits; -crystallin can also be cross-linked by disulfide bonds due to activation of glutaminase by Ca2, in short, elevated lens Ca 2 It is the result of many factors, and is also the initiator of the development of cataract caused by various causes. The calcium channel blocker Verapamil has been used to prevent the occurrence of cataract.

The content of Cu2 and Zn2 in the lens of senile cataract is decreased, which is related to the decrease of SOD activity of Cu2 and Zn2. It may be one of the causes of cataract caused by the decrease of antioxidant capacity of senile cataract. The study shows the relationship between selenium (Se) and cataract. The most closely related, serum Se too high or too low is related to cataract occurrence, posterior subcapsular cortical opacity, nuclear selenium in serum senile cataract increased selenium content, while cortical senile cataract serum Se content decreased, animal experiments found selenium deficiency The activity of glutathione peroxidase (GSHpx) in rats decreased, and the activity of GSHpx in the lens was positively correlated with the level of selenium in red blood cells, while the content of free radicals in the lens was negatively correlated with the level of selenium in red blood cells. Higher than the control group.

3. Risk factors for age-related cataracts

(1) lens opacity is related to long-term exposure to ultraviolet light, especially long-wave ultraviolet light. Ultraviolet light with a wavelength above 295 nm can easily penetrate the cornea and be effectively absorbed by the lens. In animal experiments, short-term high-dose or long-term ultraviolet radiation can cause lens transparency. Changes have been proven, and epidemiological studies suggest that long-term exposure to sunlight can significantly increase the risk of cataract in humans. These studies can be divided into two types, one based on the study of the prevalence of population based on ecological characteristics. The other is to explore the relationship between individual dose and incidence or case-control study. Although these studies are limited and affected by various experimental conditions, the results are still universal. Strict control of cumulative doses of UV radiation has found that cortical The risk of posterior subcapsular opacity is positively correlated with the cumulative dose. It has also been suggested that the ozone hole cavity leads to an increase in ultraviolet radiation, and thus the incidence of cataract may increase, but this speculation lacks sufficient evidence.

(2) The results of diabetes research showed that the incidence of cataract in diabetic patients was significantly higher than that in normal people. With the increase of blood glucose levels, the incidence of cataracts also increased. Other studies reported that senile cataracts in diabetic patients were significantly advanced. Biochemical studies of cataractous lenses with diabetes and galactosemia show that the electrolytes, glutathione, glucose or galactose content in the lens are abnormal, and glucose or galactose can form sugar alcohols under the action of aldose reductase. The lens is hyperosmotic, resulting in swelling of the lens fibers, vacuolation, and eventually turbidity. For younger diabetic patients, the most important factor is the duration of diabetes, the most important factor for adults with diabetes. It is the age at the time of the survey, and the high degree of consistency in the results of different epidemiological studies suggests that we should regularly check the lens of diabetic patients.

(3) Frequent diarrhea may be related to the occurrence of cataract, and four intermediate links may explain the role of diarrhea in the occurrence of cataract: nutrient deficiency caused by poor absorption of nutrients, relative alkali caused by the use of bicarbonate Poisoning, dehydration caused by osmotic pressure between the lens and aqueous humor, increased urea and ammonium cyanate content, resulting in lens protein denaturation, etc. However, most studies have not found a necessary link between the two, and thus important from the public health From a sexual and biological perspective, the relationship between diarrhea and cataract needs further research.

(4) When the enzyme system in the lens, the ability of proteins and biofilms to resist oxidative attack is insufficient, it can cause cataracts, such as light, heat, electromagnetic, microwave radiation and other damage, which can make active oxygen such as hydrogen peroxide, superoxide Anions, singlet oxygen and hydroxyl radicals participate in the oxidation reaction, causing lens damage, so the lens contains enough antioxidants, such as peroxidase, catalase, glutathione peroxidase and vitamins such as carrots. Vitamins B2, vitamins C and E can enhance the resistance to these damages.

(5) Drugs:

1 long-term systemic or topical application of large doses of glucocorticoids, can produce posterior subcapsular opacity, its morphology is similar to radiation cataract, the occurrence of cataract is related to the dose and duration, the greater the dose, the longer the cataract occurs The higher the rate, the higher the dose of prednisone for 1 to 4 years, the incidence of cataract can be as high as 78%, some early studies have confirmed in rheumatoid arthritis, asthma, pemphigus, kidney disease, lupus and kidney transplantation In patients with a large number of immunosuppressive agents, glucocorticoids have a cataract-causing effect, and studies have reported that long-term (more than 1 year) large doses of glucocorticoids (15 mg/d prednisone) can cause the incidence of posterior capsule cataract. Increased, other studies on the epidemiology of senile cataract have also confirmed that glucocorticoids can cause cataract under the posterior capsule.

2 The plasma tryptophan content and aldose reductase activity in the lens are increased in cataract patients, while aspirin or its active ingredient (salicylate) can inhibit aldose reductase and reduce plasma tryptophan content, so it is speculated that aspirin There may be cataract prevention, salicylate and tryptophan compete for a common binding site in plasma proteins, resulting in decreased binding and total tryptophan levels, although a few studies have reported that aspirin or its analogues have a certain effect on cataracts. Prevention and treatment, but most clinical research evidence is not sufficient.

3 Allopurinol is an anti-hyperuric acid preparation widely used in the treatment of gout. Some sporadic reports suggest that long-term oral allopurinol may be associated with posterior subcapsular cataract formation.

4 phenothiazine can be combined with melanin to form a photosensitizing substance to cause pigmentation. In the 1960s, it was reported that patients with phenothiazine, especially chlorpromazine, may have ocular pigmentation and lens opacity, and lens opacity may occur. Non-drugs act directly, but are the result of increased photoradiation due to hyperpigmentation.

(6) Extensive social and epidemiological surveys have also found that cataracts are associated with education, smoking and drinking history, blood pressure, and even gender, although there is no significant biological link between low education and cataracts, It is consistently shown to be associated with the onset of various types of senile cataracts. Of course, the effects of social status, economic conditions and occupational differences are not excluded. The study on the relationship between gender and cataract shows that the risk factors for cataract in women are slightly higher than those of males. While women taking estrogen after menopause can reduce the risk of developing nuclear cataracts, most studies have shown that smoking can increase the risk of developing cataracts, leading to the mechanism of cataracts and the presence of oxidants that can damage antioxidant structures. , or directly damage the structure of the lens protein, long-term heavy drinking caused by cataract has been reported in the literature, the mechanism of drinking cataract is still unclear, may be related to ethanol in the body converted to acetaldehyde and damage lens protein, senile cataract occurs Related to high blood pressure, The risk of posterior subcapsular opacity is 2 times higher than that of systolic blood pressure of 120 mmHg. There is no definite evidence of whether cataract is directly related to blood pressure. Some people think that cataract has nothing to do with hypertension, and may take antihypertensive with long-term. Drugs such as thiazide diuretics may also be associated with other factors such as diabetes.

Age-related cataract prevention

Avoid ultraviolet radiation, take anti-oxidant and anti-free radical drugs, etc. for some patients.

Age-related cataract complications Complications, lens-soluble glaucoma

Acute exacerbation of angle-closure glaucoma, lens component allergic endophthalmitis, lens-soluble glaucoma, and lens nucleus detachment into the vitreous may occur during different stages of age-related cataract development.

Age-related cataract symptoms common symptoms lens opacity visual impairment blisters

According to the difference of opaque sites, age-related cataracts are clinically divided into three types, namely cortical, nuclear and posterior subcapsular opacity cataracts. In fact, there is no strict distinction between various types of age-related cataracts, only It is the condition that the opacity is dominated. Corticality is the most common in age-related cataracts, accounting for 65% to 70%; followed by nuclear cataracts, accounting for 25% to 35%; subcapsular opaque cataracts are relatively rare. , only 5%.

1. Cortical age-related cataract Cortical cataract is the most common type of age-related cataract. It is characterized by opacity starting from the peripheral superficial cortex and gradually expanding to the central part, occupying most of the cortical area. According to its clinical development process and manifestations, cortical cataract can be divided into four phases: initial stage, advanced stage, mature stage and over-ripe stage.

(1) Initial stage: The earliest change is the presence of sprue-like transparent water clefts or blisters under the anterior and posterior capsules of the peripheral part. The water gap or blisters are mainly due to the lens epithelial cell pump transport system. The abnormality causes the liquid to accumulate in the lens. The liquid accumulation can make the lens fiber radial or lamellar. In the former, the liquid can expand along the direction of the lens fiber to form a typical cuneiform turbidity. The bottom edge is located at the equator of the lens. The tip points to the center of the pupil area, and the dilated examination has a typical spoke-like appearance under back-illumination or direct diffuse illumination. This spoke-like turbidity can be located at the superficial part of the cortex, and then expands to the deep, and the layers can be mutually Overlapping, finally replacing the spoke-like turbid appearance with a full gray-white opacity of the lens, representing the age-related cataract entering the advanced phase.

(2) Progression period: the edema of the lens fiber and the increasing fluid between the fibers cause the lens to expand and increase in thickness, so it is also called the inflation period. On the one hand, the tension of the capsule with the background of turbidity increases. Reflective, on the other hand, due to the expansion of the anterior chamber shallow, the latter in a patient with glaucoma constitution, it is easy to induce acute exacerbation of glaucoma, but not all patients with cortical cataract have to undergo expansion process, Even if there is a considerable difference in duration and severity between individuals, it may not always induce glaucoma attacks. The main symptoms of this stage are visual loss, sometimes accompanied by glare, occasional monocular double vision, due to Some of the cortex is transparent, so the iris new moon projection test is positive.

(3) Maturity: This stage is characterized by all opacity of the lens. The slit lamp can only see the cortex with limited depth in front, showing an unstructured white turbid state. At this time, the iris new moon shadow projection test turns negative. The lens fiber undergoes a series of pathological processes such as edema, degeneration, and membrane rupture. Eventually, the lens fiber collapses and loses its normal morphology as a result. Histologically, it represents a characteristic change of fiber matrix degeneration, forming a so-called Morgagnan body, applying histochemistry. Techniques and X-ray diffraction methods for the study of diabetic and age-related cataract lenses have revealed that the spheroids have a lipid bilayer membrane containing -crystallin, a small amount of - and -crystallin and fibrin, Prove the source of its fibrous matrix.

By the maturity stage, the lens capsule can maintain the original toughness and tension, and then gradually develop to degeneration. Therefore, extracapsular cataract extraction, phacoemulsification and intraocular lens implantation are appropriate before cataract maturation.

(4) Over-ripening period: due to the majority of the liquefaction of the matrix, the loss of certain basic components reduces the content of the lens, and the anterior capsule loses its original tension and exhibits a relaxed state. Sometimes it can be seen that the core that has not yet been liquefied sinks into the capsular bag. Below, as the eyeball rotates and shakes, at this time, it can be accompanied by iris tremor. In special cases, due to trauma or severe vibration, the core can penetrate the capsule and break into the anterior chamber or the vitreous cavity, such as accompanied by loss of liquefied matrix. The patient will have a clear and unhealed result.

When the capsule is denatured or microscopic cracks are formed due to trauma, the protein component may overflow into the anterior chamber, causing an autoimmune reaction, causing phaco-anaphylactic endophthalmitis, which is different from general iridocyclitis. The onset of the disease is sudden, sudden swelling of the eyelids, corneal edema, dense distribution of KP after the cornea, extensive post-iris adhesion, and even the formation of pupillary membrane closure, and tissue debris can accumulate in the iris corneal corner, blocking the trabecular meshwork, resulting in Secondary glaucoma, the so-called phacolytic glaucoma, in most cases, drug treatment is ineffective, surgical removal of the lens is the only means.

2. Nuclear age-related cataract nuclear age-related cataract (nuclear cataract) is far less complicated than morphologic changes and development stages like cortical cataract. Nuclear cataract often coexists with nuclear sclerosis. Initially, opacity occurs in embryos. The nucleus, then expanding outward until the senile nucleus, this process can last for several months, years or longer, in the process of lens nucleus turbidity can be accompanied by color changes, early, a small amount of brown pigment only accumulated in the nuclear region Does not extend to the cortical area, but sometimes the cortical area is very thin, but also the appearance of the entire lens is brown reflective, when the pigment accumulation is less, the core is pale yellow, can not affect the vision, the fundus is also clearly visible, the gap The lamp inspection outlines the turbid contour on the optical cut surface with a difference in density.

As the degree of cataracts worsens, the color of the lens nucleus gradually deepens, turning from pale yellow to brown or amber. In the case of so-called persistent nuclear cataracts that have not been treated for a long time, especially in diabetic patients, the lens nucleus eventually changes. Black, forming a so-called black cataract, the color of the lens nucleus has a certain correlation with the nuclear hardness, that is, the deeper the color, the harder the nucleus, especially when selecting the case before the phacoemulsification surgery. From the surgical point of view, The significance of identifying cortical and nuclear cataracts is that the former lens nucleus is generally small and soft, and is most suitable for phacoemulsification cataract extraction; while the latter in the selection of cases, especially considering the nuclear hardness factor, this is the beginning It is especially important for scholars.

It is worth mentioning that as the lens nucleus hardens, the refractive index gradually increases, thus forming a special clinical phenomenon of progressive increase of myopia. If nuclear hardening is limited to the embryonic nucleus, the adult nucleus is not affected, and the result will be produced. A more special double refractive phenomenon, that is, the central area is high myopia, and the peripheral area is hyperopia, resulting in monocular double vision.

3. Subcapsular cataract cataract refers to the type of cataract with subcapsular opacity as the main feature. The opacity is mostly under the posterior capsule, which is brown fine granular or shallow cup. Shaped vesicles, sometimes similar changes can occur under the anterior capsule. The lesions generally start from the posterior subcapsular axis, showing small opacity, no obvious boundary with the posterior capsule, sometimes under the slit lamp examination. It can be found that the capsule near the turbid area is involved, showing yellow, blue, green and other reflections, forming a so-called polychromatic luster phenomenon, because the lesion is closer to the node, so even if the disease is early, or the lesion range is very small Light, it can also cause severe visual impairment. Clinically, it is often found that vision is not consistent with the degree of opacity of the lens. Careful examination can be found that posterior capsule opacity is the main reason. When there is a similar change under the current capsule, the capsule The transparent area under the membrane disappears and can evolve into anterior subcapsular cataract. This type of cataract occurs mostly in the 60-80 age group, but at maturity or over-cooked cataract, Like body into full opacity is characterized by its former involvement subcapsular necessarily a concurrent phenomenon, and this should not be confused.

Subcapsular opaque cataract, except for the subcapsular shallow cortical involvement, other parts of the cortex and lens nucleus are transparent, so it belongs to the type of soft nuclear cataract. From this point, subcapsular opacity cataract is phacoemulsification The best indication.

Age-related cataract examination

Most of the necessary biopsy related to cataract surgery, such as blood routine, blood biochemical examination, urine routine examination, to understand the basic state of the patient's body, and to rule out other risk factors for cataract.

It is possible to predict abnormal conditions and postoperative visual acuity during surgery.

1. Intraocular pressure examination excludes visual impairment caused by high intraocular pressure.

2. The angle of the corner of the room should be examined by ultrasonography (UBM) to detect the width and openness of the iris cornea angle, mainly in patients with a history of glaucoma. Provide the basis for the formulation.

Ultrasound biomicroscopy is an important method to understand the structure of the anterior segment of the eye. It can check the iris, angle of the anterior chamber, lens and suspensory ligament, especially in the anterior segment of the anterior segment of the refractive interstitial opacity or small pupil, it is cataract surgery. The former is an important auxiliary diagnostic tool.

3. B-ultrasonic scanning (B-ultrasonic Scanning) is a routine examination method for cataract patients, which can exclude vitreous hemorrhage, retinal detachment and intraocular tumors, etc., when the lens is obviously turbid, and the fundus examination can not distinguish the fundus condition. important.

4. 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.

Clinically, it is mainly used in patients with lensic nucleus or abnormal corneal endothelial cells such as the elderly (over 80 years old), patients with secondary intraocular surgery, patients with keratopathy and patients with history of ocular trauma.

(2) Retinal visual acuity test: a specific image or visual target is projected onto the retina, and the visual acuity of the retina is directly examined regardless of whether the refractive interstitial is turbid or not, so as to understand the optimal visual acuity that the patient may achieve after surgery.

(3) 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.

Clinically, it is mainly used in patients with retinitis pigmentosa or whole retinal detachment. It shows the reduction or even disappearance of the visual and scotopic reactions. The patients with retinal vascular disease mainly show a decrease in oscillatory potential, but when performing ERG examination on very dense cataract, Light is hard to reach the retina, so false positive results can occur.

(4) Visual evoked potential test (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.

(5) Optical coherence tomography examination: the use of near-infrared light for tomographic scanning of the anterior and posterior segment of the eye is a high-resolution cross-sectional imaging imaging method that visually displays the subtle layers of the retina in vivo. The structure, especially for the diagnosis of macular diseases, has significant clinical value (Figure 16).

Clinically applied to patients with suspected macular hole, age-related macular degeneration, and anterior membrane of the retina.

(6) Fundus examination and fundus angiography: may be considered when conditions permit.

1 fundus examination: the use of direct ophthalmoscopy or indirect ophthalmoscope red light reflection method to understand the degree of lens opacity, through the ophthalmoscopy, to exclude fundus lesions, especially when the lens opacity and visual acuity does not match, the common fundus that affects postoperative visual recovery The changes were: A. diabetic retinopathy, B. high myopia fundus lesions, C. senile macular degeneration, D. macular hole, E. central retinal vein occlusion, F. ischemic optic neuropathy, G. retinal detachment.

2 fundus angiography: when using the fundus to examine the fundus, static and superficial phenomena are observed, while fundus angiography provides dynamic and intrinsic conditions, which can be comprehensively utilized by the use of contrast agents in retinal and choroidal imaging. Understanding the condition of the retina and choroidal blood vessels can help to detect abnormal neovascularization and vascular leakage. There are two types of imaging methods:

A. Fluorescein angiography (FFA): Fluorescein is used as a contrast agent, mainly reflecting retinal blood vessels.

Clinical application: diabetic retinopathy, central retinal artery occlusion, retinal vein occlusion, age-related macular degeneration (dry type).

B. Indocyanine green angiography (ICGA): Indocyanine green angiography (CTGA) is a contrast agent that mainly reflects choroidal vasculature and is used in hemorrhagic fundus diseases.

Clinical application: age-related macular degeneration (wet type), intermediate osmotic retinal choroidal lesion, high myopia neovascular membrane.

Diagnosis of age-related cataract

Diagnostic criteria

According to the medical history, clinical manifestations and clinical examination signs can be clearly diagnosed. In the epidemiological investigation of cataracts, due to different diagnostic criteria, the research results will be very different, and it is difficult to compare the research data. Therefore, it is necessary to work out Clear diagnostic criteria and standardized survey methods. At present, the cataract epidemiological survey adopted in China is mainly carried out with reference to the following three criteria.

1. World Health Organization (WHO) blind and low vision standard corrected visual acuity <0.05 for blindness, 0.05 ~ <0.3 for low vision.

2. WH0 and the National Institute of Ophthalmology Diagnostic Criteria 1982 WHO and the National Eye Institute of the United States proposed visual acuity <0.7, lens opacity, and no other eye diseases that cause vision loss as a diagnostic criteria for cataract.

3. The criteria for specific age groups are designed to investigate the prevalence of cataract in a certain age group, such as age 50 years old, opacity of the lens, and no other eye diseases that cause vision loss. The results of this method are only Describe the condition of cataracts in a specific age group.

In addition to the epidemiological survey criteria described above, there are several other diagnostic criteria for cataract in the clinic, such as the lens opacity recording method of Chylack et al., the LOCS system (LOCS). The location, range, color and density of the opacity of the lens are compared with the standard photos, and the grades are divided to determine the degree of opacity of the lens. This diagnostic standard is complicated to operate, and is mostly used for experimental research of cataracts, not suitable for epidemics. Applied in the survey.

Differential diagnosis

The distinguishing point from the complicated cataract is that the latter is caused by systemic or ocular local lesions, and the age-related cataract is generally older.

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