Cataracts are classified in the following ways:
(1) traumatic; (2) concurrent; (3) metabolic; (4) drug and toxicity; (5) developmental; and (6) posterior. Zhang Jian, Ophthalmology, Xuanwu Hospital, Capital Medical University
2.According to the age of occurrence (1) congenital; (2) infantile; (3) youthful; (4) adult; (5) geriatric.
3.According to the site of clouding (1) cortical; (2) nuclear; (3) subcapsular; (4) cystic.
4.According to the degree of turbidity (1) immature stage; (2) swelling stage; (3) mature stage; (4) overripe stage.
5.According to the morphology of turbidity (1) punctiform; (2) coronal; (3) laminar; (4) other morphology.
6.According to whether the progression (1) stationary; (2) progressive.
Mild clouding of the lens that does not affect vision is not clinically significant. Cataract is considered clinically significant when the clouding causes vision loss.
Senile cataracts
Geriatric cataract is the most common type of cataract, mostly seen in elderly people over 50 years old, and the incidence increases with age. According to a survey on cataract disease and surgery in Beijing in 2001, the prevalence of cataract in people aged 50-60 was 4.34%, while the prevalence of cataract in people aged 70 and above was 63.2%, and the low vision caused by cataract was more concentrated in the elderly group. It is a degenerative change that occurs gradually during the aging process of the lens. Its pathogenesis is not fully understood and is associated with ultraviolet light. Systemic diseases such as diabetes mellitus, hypertension, atherosclerosis, genetic factors and nutritional and metabolic status of the lens are involved.
Age-related cataract is a bilateral disease, but the onset of the two eyes can be sequential. Patients feel that there is a cloudy obscuration or a fixed black spot in front of their eyes, and there is progressive, painless vision loss. The timing of visual impairment varies depending on the location of the clouding. There may be monocular diplopia, hyperopia and refractive changes. According to the site of cataract formation, senile cataract is divided into three categories: cortical, nuclear and subcapsular.
1. Cortical cataract.
This is the most common type of senile cataract and is divided into 4 stages according to its development process.
(1) Initial stage: wedge-shaped clouding appears in the peripheral part of the anterior and posterior cortex, with its base in the equatorial part and the tip toward the center. Initially it occurs mostly inferiorly, followed by mostly transparent, pupillary area vermilion invasion, which generally does not affect vision or the patient complains of cloudy obscuration. The earliest wedge-shaped clouding visible under the slit lamp after pupil dilatation is the separation of the lens fiber plate layers in a feathery pattern, sometimes with vacuoles. The period can be several years before reaching the next stage.
(2) Swelling phase or end-ripening phase: the clouding gradually increases at the same time, the cortex absorbs water and swells, and similar clouding occurs on both sides and above the lens, later forming a spoke-like clouding. At this time, the lens volume increases, pushing the iris forward to make the anterior chamber shallow, and for those with closed-angle glaucoma qualities, the shallowing of the anterior chamber may cause an acute attack of glaucoma. At this stage, visual acuity is significantly reduced and the fundus of the eye can no longer be peered into.
(3) Mature stage: the lens is completely cloudy and milky, the lens swelling subsides, the anterior chamber depth returns to normal, and the fundus cannot be peeked into. Visual acuity is reduced to photopic or manual, but light localization and color vision are normal.
(4) Overmature stage: The mature stage lasts too long, usually after several years, the water in the lens continues to be lost, the lens volume shrinks, the anterior chamber deepens, and the iris has tremor. As the disease continues to progress, the lens fibers break down and melt into a milky liquefaction, and the brownish-yellow hard nucleus sinks below, which can cause a sudden improvement in vision. The lens cortices that are present in the atrial water for a long time can be phagocytosed by macrophages, blocking the anterior chamber angle and causing secondary open-angle glaucoma, called lens lysis glaucoma; violent shaking can rupture the lens capsule and cause the lens nucleus to dislodge into the anterior chamber or vitreous humor. Degenerative changes often occur in the lens ligament during this period, which can easily cause lens dislocation.
2. Nuclear cataract.
Cortical cataract is less common than cortical cataract, with an early onset, usually starting at the age of 40 and progressing slowly. The clouding starts in the center of the lens nucleus and gradually develops to complete clouding of the nucleus later. In the early stage, the vision is not affected, but later the density of the lens nucleus increases and the convex lens is enhanced, so myopia is often present. When the pupil is narrowed or dilated, the light passes through the central or peripheral part of the different refractive states respectively, so both distance and near vision are still clear. It is important to note that the patient feels that the near objects are clear again, but this is not a return to old age, but a manifestation of aggravation of nuclear cataract. With the increase of nuclear clouding, the nucleus starts to be grayish yellow, and then gradually becomes yellowish brown, brown or brownish black, which is clinically called brown or black cataract. At this time, vision is extremely diminished and the fundus cannot be checked.
3. Subcapsular cataract.
It is a special manifestation of cortical cataract and can occur in the anterior subcapsular and posterior subcapsular. In the early stage of posterior subcapsular cataract, the subcapsular clouding in the posterior pole is composed of many dense dots with small vacuoles and crystalline particles, which looks like the surface of slag bricks, also known as disc cataract. Although the clouding of the lens is not obvious during examination, the only clouding is in the center of the visual axis, so the blurred vision is obvious and also requires surgery. Subcapsular cataracts can later develop into cortical clouding and gradually develop into complete cataracts.
Congenital cataracts
Most congenital cataracts exist before and after birth, and some of them are formed gradually after birth. 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 latter two require surgery. Most congenital cataracts are combined with amblyopia or other eye diseases. After pediatric cataract surgery, we should insist on amblyopia training and check other eye diseases.
Complicated cataracts
Complicated cataracts are caused by inflammatory or degenerative diseases of the eye, which affect the nutrition and metabolism of the crystal and lead to clouding of the crystal. It is common in uveitis, retinitis pigmentosa, retinal detachment, glaucoma, intraocular tumors, high myopia and low eye pressure. Complicated cataracts are more difficult to treat and operate, have more complications, and have a poorer prognosis than age-related cataracts.
Traumatic cataracts
Mechanical injuries to the eye (contusions, perforation injuries), chemical injuries, electric shock injuries and radiation injuries can all cause lens clouding, collectively known as traumatic cataracts.
1, contusive cataract: rupture of the lens capsule membrane, total or limited clouding of the lens; the anterior capsule of the lens can appear pigment ring clouding, and the corresponding part of the lens can be out of the ring clouding under the capsule.
2. Perforated traumatic cataract: There is a rupture in the lens capsule membrane. If the rupture is large and deep, all of the lens is cloudy; cloudy cortex protruding into the anterior chamber may be followed by uveitis or glaucoma.
Radiation cataract: Infrared cataract can be manifested as golden yellow reticular clouding in the outer layer of the posterior pole cortex, gradually forming irregular disc-shaped clouding at the edges and stretching to the cortex or developing into lamellar clouding, finally forming complete cataract. The anterior capsule can also have dotted or linear clouding and vacuoles underneath, gradually developing into complete clouding, and microwave cataracts have dotted clouding in the lens cortex.
4. Electrocution cataract: electrocution is often unilateral, and lightning injury is mostly bilateral; the anterior subcapsular cortex of the lens is cloudy in electrocution injury, and both anterior and posterior subcapsular cortex can be cloudy in lightning injury; in most cases, the clouding is static and does not develop, but it can also gradually develop into complete cataract.
Diabetic cataract
Diabetic cataract is a type of metabolic cataract. In diabetes mellitus, the elevated blood glucose increases the osmotic pressure of the lens and causes the fibers to swell and degenerate due to the absorption of water, which leads to clouding. The other is “true diabetic cataract”, which often occurs in severe juvenile diabetic patients. The other type of cataract is “true diabetic cataract”, which often occurs in severe juvenile diabetic patients, with rapid onset and progression in both eyes. When diabetes is well controlled, the above symptoms may be relieved or disappear to varying degrees.
It is important to note that regardless of the type of cataract, for moderate to severe lens clouding, surgery is currently the only internationally recognized and effective treatment method.