What is cataract?
Cataract is a common ophthalmological disorder that causes progressive loss of vision through loss of lens transparency. Studies show that about 50% of the population loses their vision due to this disorder.
Cataract represents the change in the transparency of the lens. It reacts when subjected to an aggression by opacification, a process induced by:
- change in water content of the lens
- increased concentration of sodium and calcium ions
- decrease of potassium, glutathione and vitamin C
- decrease of the amount of glucose consumed
Most cataracts develop slowly and don’t bother your vision all at once. But over time, cataract will eventually interfere with your vision. At first, brighter lighting and stronger glasses can help you cope with cataract. But if your vision impairment interferes with normal activities, you may need cataract surgery. Fortunately, cataract surgery is generally a safe and effective procedure.
Some inherited genetic disorders that cause other health problems can increase your risk of cataract. Cataract can also be caused by other eye disorders, past eye surgeries or medical conditions such as diabetes. Long-term use of steroid medication can cause cataracts.
How a cataract is formed
The lens, where the cataract forms, is located behind the colored part of the eye (iris). The lens focuses light passing into your eye, producing clear images on the retina – the light-sensitive membrane in the eye that works like film in a camera.
As we age, the lenses in our eyes become less flexible, less transparent and thicker. Age-related and other medical conditions cause the tissues in the lens to break down and clump together, opacifying small areas of the lens.
As the cataract continues to develop, the blurring becomes denser and involves a larger part of the lens. A cataract scatters and blocks light as it passes through the lens, preventing a clearly defined image from reaching the retina. As a result, your vision becomes blurred.
Cataract generally develop in both eyes, but not evenly. The cataract in one eye may be more advanced than the other, causing a difference in vision between the eyes.
What symptoms do you experience in case of cataract?
Signs and symptoms of cataract include:
- cloudy, blurred or poor vision
- increased difficulty in night vision
- sensitivity to light and glare
- you need brighter light for reading and other activities
- appearance of halos around light sources
- frequent changes in the prescription of glasses or contact lenses
- near vision improves and distance vision decreases (at first, some patients, who had plus diopters, are happy to have their “vision restored” – they can read without glasses or with older glasses with smaller numbers)
- increase in diopters in those with myopia (minus lenses)
- fading or yellowing of colors
- double vision in one eye
- Chromatic sense may be altered in nuclear cataract, accompanied by a deficit in the yellow/blue axis;
- the visual field may show a general decrease in sensitivity (in automated perimetry) or contraction of isopters, localized scotomas (in kinetic perimetry)
At first, the vision disturbance caused by cataract may only affect a small part of the lens of the eye and you may not be aware of any vision loss. As cataract grow, it opacify the lens more and distort the light passing through the lens. This can lead to more noticeable symptoms.
What are the risk factors?
Factors that increase the risk of developing cataract are:
- Ageing
- Diabetes
- Excessive exposure to sunlight
- Smoking
- Obesity
- High blood pressure
- Previous eye injury or inflammation
- Other eye operations for other disorders
- Prolonged use of corticosteroid drugs
- Excessive alcohol consumption
- Heredity
How can you prevent cataract?
No studies have shown how to prevent cataract or slow the progression of cataract, but the following are recommended:
Examine your eyes regularly. Regular examinations can help detect cataract and other eye problems in the early stages.
Quit smoking. Ask your doctor for suggestions on how to quit smoking. Medications, counseling and other strategies are available to help you.
Manage other health problems. Follow your treatment plan if you have diabetes or other medical conditions that may increase your risk of cataract.
Maintain a healthy diet that includes plenty of fruits and vegetables to ensure you get plenty of vitamins and nutrients. Fruits and vegetables have many antioxidants, which help maintain your eye health.
Wear sunglasses. Ultraviolet light from the sun can contribute to the development of cataract. Wear sunglasses that block ultraviolet B (UVB) rays when outdoors.
Reduce alcohol consumption. Excessive alcohol consumption can increase the risk of cataract.
What types of cataracts are there?
Congenital cataract
With an incidence of 1 in 2000 newborns, this type of cataract represents lens transparency abnormalities characterized by progressive or non-progressive opacities, total or partial, unilateral or bilateral, developed during intrauterine life and detected at birth or later. They can be divided into two broad categories:
- capsular-lenticular opacities, which involve only the lens capsule and the immediately underlying lens layers
- lenticular opacities that develop primarily in the lens substance.
Risk factors for congenital cataract
- Maternal infection with rubella virus in the first trimester of pregnancy is the most common cause. Generally, this type of cataract is not accompanied by other major ocular abnormalities, but iris atrophy, ciliary body atrophy, microphthalmia and pigmentary retinopathy may occur.
- There is also a risk of general abnormalities (cardiac, cranial, dental, skeletal, deafness, mental deficiencies).
- Other incriminated infections are those with rubella virus, herpes viruses, influenza viruses, mumps virus, toxoplasma gondii (in congenital toxoplasmosis the lens develops opacities during significant uveal inflammatory phenomena).
- Irradiation of pregnant women in the first trimester of pregnancy
- Ingestion of medicinal substances during pregnancy (corticosteroids, sulfonamides, etc.).
- Maternal deficiency factors, avitaminosis, folic acid deficiency, etc.
Presenile cataract
It occurs before the age of 60 and it comes in several clinical forms:
- progressive presenile cataract, which is identical to senile cataract but is more often cortical than nuclear, is bilateral and asymmetrical.
- non-progressive presenile cataract, which insignificantly affect visual acuity.
- coronary presenile cataract occurs early, in adolescence, and develops in the outer layers of the nucleus and deep layers of the cortex. The opacities are stationary and do not produce total opacification of the lens.
- cerulean presenile cataract: fine, bluish-tinted opacities appear at the nucleus level, which do not affect vision.
Age-related senile cataract
Senile cataract represents the partial or total loss of lens transparency. It is the most common form of cataract and comes with age. It is a primitive cataract, the prevalence of which increases with age, 50% in the population aged 65-74, 70% in the population over 75.
The causes of lens opacification with age are related to the physiological changes produced by lens ageing, i.e. increased volume and yellowing of lens fibers, to which chronic UV exposure is added, drug medication, local metabolic disorders, race and heredity.
Classification of lens opacities according to their location in the lens:
Nuclear (central) cataract
- Opacities in the lens nucleus in 25% of cases and increasing with age. They are the result of progressive sclerosis of the nuclear lens fibers which dehydrate and turn yellow-brown, the cortical layers remaining transparent.
- The central topography of this type of cataract results in a pronounced visual disturbance in bright light due to myosis – manifested by decreased visual acuity especially in bright light. Darkness, through the mydriasis it produces, improves visual acuity. Lens myopia occurs, due to condensation of the lens nucleus, gradually progressing to -6-10 D.
- Colored halos
- Monocular diplopia
- In daylight no change in pupil color is observed. Under the biomicroscope the nucleus appears greyish or with a reddish-brown reflection due to the deposition of melanic pigment in the nucleus. With the ophthalmoscope a greyish shadow is observed. The progression is long term.
Cortical (peripheral) cataract
- Cortical opacities that occur due to hyper-hydration of lens fibers that deform and then disorganize. Opacities arise from the lens periphery and converge towards the pupillary axis
- This type of cataract develops in 4 stages:
- early stage is subjectively manifested by slow decrease in visual acuity, miodesopsia, monocular diplopia, transient myopia leading to decreased presbyopia. Objectively there are fine cuneiform or spiculiform opacities located peripherally in the anterior, posterior or equatorial cortex. The opacities appear greyish white on biomicroscopic examination, black against the pink background of the pupil on ophthalmoscopic examination.
- intumescent stage – due to water soaking, the lens becomes intumescent, bulging. Visual acuity is greatly diminished. Objectively, the pupil is greyish white and the opacified lens has an icy appearance. On biomicroscopic examination the opacified lens fibers appear separated by fluid layers, the anterior chamber is shallow due to the bulging of the lens. The iris is pushed forward due to the increased volume of the lens and can sometimes lead to mechanical blockage of the chamber angle with the onset of acute secondary glaucoma.
- mature stage – characterized by opacification of all lens layers, excess water is removed and the lens returns to normal volume. Subjectively, visual acuity is reduced in the shadow of hands or perceive light sensation. Objectively, in daylight and biomicroscopically, the anterior chamber is of normal depth, the pupillary field is greyish white and the lens is completely opaque with an icy appearance.
- hypermature stage (morgagnian cataract) – degeneration and liquefaction of the fibers in the lens cortex occurs, with their fragmentation into morgagnian, protein particles that give the lens contents a milky white appearance. The nucleus, while remaining dense, falls into the descending half of the lens. At the same time, the degenerative process also affects the lens capsule, which becomes permeable and allows the proteins to pass outside the lens, sometimes resulting in secondary phakolytic glaucoma, through obstruction of the trabecular pores by the protein particles. Visual acuity is maintained in the shadow of hands or perceives light sensation.
Posterior (central, posterior) subcapsular cataract
- posterior subcapsular opacities occur in the posterior layers of the lens in the axial region, from where they extend to the periphery
- photophobia and progressive and marked decrease in vision set in
- near vision is affected early due to accommodation myosis
Pathological cataract
This type of cataract occurs in connection with various genetic, metabolic and dermatological disorders from which the patient suffers, such as:
a. Diabetes mellitus – induces lens opacity in the young and accelerates the progression of cataracts in the elderly. These cataracts are frequently accompanied by other ocular complications of diabetes: diabetic retinopathy, increased risk of hemorrhage and infection during cataract surgery.
b. Hypoglycemia – rarely induces bilateral lamellar opacities between transparent lens fibers
c. Hypoparathyroidism – can cause bilateral posterior subcapsular cataract and treatment of hypocalcemia stops the progression of cataract
d. Hypothyroidism – produces cortical “snowflake” opacities
e. Wilson’s disease – is characterized by low ceruloplasmin levels and induces “sunflower-like” lens opacities
Complicated cataract
This type of cataract occurs as a result of local inflammatory, degenerative, ischemic disorders and glaucoma.
Inflammatory disorders
- Severe infectious keratitis induces anterior subcapsular, pyramidal or total lens opacities
- Chronic iridocyclitis produces anterior subcapsular opacities, especially in the iris-lens synechiae
- Fuchs’ heterochromic iridocyclitis involves the following ocular changes
- chronic cyclitis with corneal endothelial precipitates, without iris-lens synechiae
- heterochromia iridis (color difference between the two eyes due to iris atrophy in the affected eye, which appears more discolored)
- early unilateral cataract with posterior cortical onset and slow progression to total cataract
- uveitis
Degenerative disorders
- Hereditary retinal dystrophies (retinopathy pigmentosa, gyrate atrophy, Leber congenital amaurosis, etc.) and progressive iris atrophy
- High myopia is frequently associated with posterior subcapsular or nuclear cataract
- Intraocular tumors
- Retinal detachment
- Glaucoma
- Acute glaucoma leads to the formation of anterior subcapsular opacities (glaucomflecken) in the pupillary area.
- Chronic closed-angle glaucoma through subacute closed-angle crises leads to the formation of well-defined anterior subcapsular opacities in the pupillary area, which may resorb.
- Chronic open-angle glaucoma leads over time to the development of nuclear cataract
Complicated cataract in old retinal detachment, intraocular tumors, absolute glaucoma, pigmentary retinopathy, do not benefit from surgical treatment. Cataract in uveitis can be operated at least 6 months – 1 year after the acute inflammatory process. Myopigenic cataract benefit from surgical treatment if the macula is not affected in the context of high myopia.
Traumatic cataract
It is the total or partial opacification of the lens that occurs after eye trauma. Depending on the mechanism of occurrence, traumatic cataracts can be:
a. indirect traumatic or contusive cataracts – occur after an ocular contusion a few hours later or later on
b. direct traumatic cataracts – occur following ocular puncture wounds with concomitant opening of the anterior lens capsule. Aqueous humor rapidly penetrates the interior of the lens, soaks and opacifies the lens fibers. If the rupture of the capsule is large, the lens fibers herniate into the anterior chamber. The presence of lens masses in the anterior chamber triggers anaphylactic uveitis or secondary phacogenic glaucoma.
c. Traumatic cataracts due to intra-lens or intraocular foreign objects, occurring after ocular puncture wounds with foreign object retention
d. Cataracts due to physical agents: infrared rays (the long exposure for years causes heat cataracts – as occupational disease in glassblowers, smelters, furnace workers (atmospheric electricity or electrocution, ionized electromagnetic and corpuscular radiation, atomic explosion).
The treatment of traumatic cataract is surgical, depending on the etiology, clinical appearance and age of the patient. Most of these cataracts are monocular and raise the problem of optical correction of aphakia. For the recovery of binocular vision, optical correction of monocular aphakia can only be done with contact lenses or artificial lens implants. Classical correction with aerial lenses results in aniseikonia of about 30%, which prevents image fusion in the occipital cerebral cortex.
What treatment methods exist for cataract?
The only effective treatment for cataract is surgery. It cannot be treated with medication or corrected by wearing glasses.
Phacoemulsification cataract surgery
Phacoemulsification is the most common procedure for cataract. A small incision is made in the eye to reach the opacified lens. Using high-frequency sound waves (ultrasound) the lens is broke into tiny pieces by phacoemulsification, then removed from the eye (aspirated). A new artificial lens is then inserted.
Learn more about Cataract Surgery.
Reference:
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