Cataract is a disease that occurs in the lens inside the eye. Any clouding of the lens can be called a cataract, but when the clouding of the lens is mild, it does not significantly affect vision and is not noticed or ignored and is not included in the cataract category. According to surveys, cataracts are the most common cause of blindness and visual disability, with approximately 25% of humans suffering from cataracts.
Etiology.
1. Sunlight and ultraviolet light Over the years, it has been noted that sunlight is involved in the formation of human cataracts. Under the influence of UV light, phosphorus ions may combine with calcium ions in the aging lens to form insoluble calcium phosphate, which leads to hardening and calcification of the crystal. This is one of the causes of cataracts.
2. Hypoxia in the case of hypoxia may increase sodium and calcium in the crystal, correspondingly decrease potassium and vitamin C, and increase lactic acid, prompting the formation of cataract. This is one of the more common causes of cataract.
3. Nutrient metabolism, vitamin and trace element deficiency are related to cataract formation, such as calcium, phosphorus, vitamin E, A, B2, etc. This also belongs to the causes of cataract triggering.
4, endocrine disorders can contribute to cataracts, as illustrated by the higher occurrence of cataracts in diabetic patients compared to the general population.
Symptom manifestation.
Onset symptoms are bilateral, but the onset of the two eyes may be sequential. Visual acuity is progressively diminished, and sometimes fixed black spots can be seen against a bright background. Due to changes in refractive power in different parts of the crystal, there may be hyperopia, monocularity, diplopia, and increased myopia. Clinically, senile cataracts are classified into three types: cortical, nuclear and subcapsular.
1. Cortical cataract is mainly characterized by grayish-white clouding of the crystal cortex, and its development process can be divided into four stages: incipient, immature, mature, and over-ripe stages.
2.Nuclear cataract: The clouding of the crystal starts from the embryonic nucleus and gradually expands to the adult nucleus. The early stage is yellow, and as the clouding increases, the color deepens such as dark yellow and dark brownish yellow. The density of the nucleus increases, the refractive index increases, and the patient often complains of reduced presbyopia or increased myopia. In the early stage, the peripheral cortex is still transparent, therefore, the pupil is dilated in the dark to improve vision, while the pupil is narrowed in bright light to reduce vision. Therefore, surgery is usually performed without waiting for complete cortical clouding.
3. Posterior subcapsular cataract: Because the clouding is located in the visual axis area, it affects vision at an early stage.
Pathophysiology.
There are many factors that cause cataracts. Cataracts in the elderly due to age-related metabolic decreases are the most common “senile cataracts”, while other systemic diseases such as diabetes are often complicated by cataracts. A contusion of the eye without perforation can also cause cataract. Secondly, intraocular inflammation (e.g. uveitis) and intraocular diseases (e.g. retinal detachment, intraocular tumor) can cause cataracts.
Congenital cataracts can occur before or after birth, and family genetic factors can also cause early onset of cataracts in children.
Other factors associated with the development of cataracts are excessive exposure to ultraviolet light from the sun, which may be one of the reasons for the high incidence of cataracts in tropical countries. In developing countries, malnutrition may also be a cause of early onset of cataracts. Recent studies have also shown that recurrent acute diarrhea in early childhood can also contribute to the development of cataracts. Certain commonly used medications, especially long-term ocular or systemic corticosteroid applications, can lead to cataracts.
Complications.
Several complications can occur after cataract surgery, and symptomatic treatment must be made according to the cause of each complication.
1. For shallow anterior chamber caused by incision leakage, it is mostly advocated to re-suture the incision; if the degree is mild, the shallow anterior chamber can sometimes be restored by pressure bandaging the operated eye, if choroidal detachment is accompanied by incision leakage, the incision should be re-sutured to form the anterior chamber; if the scope of choroidal detachment is large, post-scleral incision and drainage in the detached area can accelerate the recovery of IOP and reset of choroidal detachment; if the scope of detachment is small and there is no obvious However, the most fundamental measure is to re-communicate the traffic between the anterior and posterior chambers, and iridotomy can achieve this purpose.
2, because the damage to the corneal endothelium is irreversible, once the persistent corneal edema occurs, the recovery of corneal optics depends on partial penetrating corneal transplantation; for patients who are inconvenienced by corneal transplantation, the symptoms can be relieved locally by hypertonic agents, with soft contact lenses or by removing the epithelial cell layer of the lesion area and covering it with a conjunctival flap. The corneal endothelium should be protected with viscoelastic, and the anterior chamber should be flushed for a long time.
3, a small amount of anterior chamber blood accumulation is generally absorbed naturally within a few days, the accumulation of blood filled with anterior chamber with high intraocular pressure should be immediately flushed anterior chamber, vitreous accumulation of blood in a small amount can be absorbed, a large number of posterior segment vitrectomy should be performed, epithelial implantation of the anterior chamber of the treatment effect is not good, the prognosis is poor, once diagnosed, should immediately remove the deep sclera near the incision of the lesion area, and freeze the hyperplastic epithelial tissue behind the affected area corneal, remove To ensure that the vitreous body does not adhere to the cornea, anterior vitrectomy should also be performed. Postoperative uveitis can generally be controlled with corticosteroids, prostaglandin inhibitors and pupil dilators, but the cause of the disease should be searched for and treated.
Once endophthalmitis is suspected after cataract surgery, the atrial fluid and vitreous should be immediately aspirated for bacterial or fungal culture and drug sensitivity test, the affected vitreous should be removed with vitreous cutter and antibiotics should be injected into the vitreous cavity, vein and subconjunctiva, the treatment of postoperative glaucoma should be local and systemic hypotensive treatment and etiological treatment at the same time. YA G laser capsulotomy is the simplest and most effective method to treat posterior capsular clouding, if an IOL has been implanted, laser incision should avoid damaging the IOL; in addition, a puncture knife can be used to enter the eye from the flat part of the ciliary body to incise the clouded and thickened central part of the posterior capsulorhexis, for retinal complications such as macular cystoid edema apply anti-inflammatory pain, corticosteroids, and for retinal detachment when surgical treatment.
Diseases that are easily misdiagnosed.
1. Congenital cataracts mostly exist before and after birth, and a small proportion gradually forms after birth. They are mostly hereditary diseases, and there are two types: endogenous ones are related to fetal developmental disorders, and exogenous ones are caused by damage to the lens caused by maternal or fetal systemic lesions. Congenital cataracts are classified into anterior pole cataract, posterior pole cataract, round nucleus cataract and total cataract. The first two do not require treatment, while the second two require surgery.
2. Acquired cataracts are clouding of the lens after birth due to systemic diseases or local eye diseases, abnormal nutrient metabolism, poisoning, degeneration and trauma. It is further divided into 6 types.
① Age-related cataract. The most common. The cause is related to slow metabolic degeneration in the elderly, and some believe it is related to long-term sunlight exposure, endocrine disorders, and metabolic disorders. According to the location of the initial clouding, it can be divided into two categories: nuclear and cortical. The visual impairment is related to the location and density of the clouding, and the post-cortical and nuclear clouding affects visual acuity earlier.
(2) Complicated cataract (complicated by other eye diseases).
(iii) Traumatic cataract.
④Metabolic cataract (due to endocrine insufficiency, such as diabetic cataract).
⑤Radioactive cataract (related to X-rays, β-rays, γ-rays, etc.).
⑥Drug and toxic cataracts. If left untreated, the bleaching in the lens will become more and more severe and eventually become completely blurred and the nucleus of the lens disintegrates, resulting in complete loss of vision.