Eye Cataracts And Cataract Surgery - Causes, Symptoms And Treatment

A cataract is a gradually developing opacity of the lens or lens capsule of the eye light shining through the cornea is blocked by this opacity, and a blurred image is cast onto the retina. As a result, the brain interprets a hazy image. Cataracts commonly occur bilaterally, and each progresses independently. Exceptions are traumatic cataracts, which are usually unilateral, and congenital cataracts, which may remain stationary. Cataracts are most prevalent in people older than age 70 as part of the aging process. The prognosis is generally good; surgery improves vision in 95% of affected people. However, in recent studies, cataracts have been associated with a higher risk of mortality in older women.

Cataracts are classified as one of three types:

• A nuclear cataract is most commonly seen as it forms. This cataract forms in the nucleus, the center of the lens, and is due to natural aging changes.
  
• A cortical cataract , which forms in the lens cortex, gradually extends its spokes from the outside of the lens to the center. Many diabetics develop cortical cataracts.
  
• A subcapsular cataract begins at the back of the lens. People with diabetes, high farsightedness , retinitis pigmentosa or those taking high doses of steroids may develop a subcapsular cataract.

Causes of cataract

Causes of cataracts include:

• aging (senile cataracts)
• congenital disorders
• genetic abnormalities
• maternal rubella during the first trimester of pregnancy
• traumatic cataracts
• foreign body injury
• complicated cataracts
• uveitis
• glaucoma
• retinitis pigmentosa
• retinal detachment
• diabetes mellitus
• hypoparathyroidism
• myotonic dystrophy
• atopic dermatitis
• exposure to ionizing radiation or infrared rays
• drugs that are toxic to the lens and that cause photosensitivity, such as prednisone (Deltasone), antihistamines, hormonal contraceptives, antidepressants, sulfa drugs, fluroquinone antibiotics, and tranquilizers.
• exposure to ultraviolet rays.

Some causes of cataract occur only in women researchers suspect that these causes may be related to hormonal changes and adverse events in pregnancy and childbearing, which are linked to higher mortality. These and other factors are undergoing investigation.

Pathophysiology may vary with each form of cataract. Senile cataracts show evidence of protein aggregation, oxidative injury. and increased pigmentation in the center of the lens. In traumatic cataracts, phagocytosis of the lens or inflammation may occur when a lens ruptures. The mechanism of a complicated cataract varies with the disease process; for example, in diabetes, increased glucose in the lens causes it to absorb water.

Typically, cataract development goes through four stages:

1. immature. The lens isn't completely opaque.
2. mature. The lens is completely opaque and vision loss is significant.
3. tumescent. The lens is filled with water, which may lead to glaucoma.
4. hypermature. The lens proteins deteriorate, causing peptides to leak through the lens capsule. Glaucoma may develop if intraocular fluid outflow is obstructed.

Cataract Symptoms and Signs

Possible signs and symptoms of cataracts include:

• gradual painless blurring and loss of vision due to lens opacity
• milky white pupil due to lens opacity
• blinding glare from headlights at night due to the inefficient reflection of light rays by the opacities
• poor reading vision caused by reduced clarity of images
• better vision in dim light than in bright light in patients with central opacity; as pupils dilate, patients can see around the opacity.

Complications of cataracts include blindness and glaucoma. Surgical complications may include:

• loss of vitreous humor
• wound dehiscence from loosening of sutures and flat anterior chamber or iris prolapse into the wound
• hyphema, which is a hemorrhage into the eye's anterior chamber
• vitreous-block glaucoma
• retinal detachment
• infection.

Diagnosis information

Diagnosis is based on the following tests:

• physical examination (shining a penlight on the pupil to show the white area behind the pupil, which remains unnoticeable until the cataract is advanced)
• indirect ophthalmoscopy and slit lamp examination to show a dark area in the normally homogeneous red reflex
• visual acuity test to confirm vision loss.

Cataract treatment

Treatment for cataract may include:

• extracapsular cataract extraction to remove the anterior lens capsule and cortex and intraocular lens (101) implant in the posterior chamber; typically performed by using phacoemulsification to fragment the lens with ultrasonic vibrations, then aspirating the pieces.
• intracapsular cataract extraction to remove the entire lens within the intact capsule by cryoextraction (rare procedure in which the moist lens sticks to an extremely cold metal probe for easy and safe extraction) with subsequent placement of an IOL in the anterior or posterior chamber after lens removal; alternatively, use of contact lens or aphakic glasses to enhance vision.
• laser surgery after an extracapsular cataract extraction to restore visual acuity when a secondary membrane forms in the posterior lens capsule that has been left intact
• discission (an incision) and aspiration in children with soft cataracts.
• contact lenses or lens implantation after surgery to improve visual acuity, binocular vision, and depth perception.

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PREVENTION POINTER

A study showed that older women who took vitamin C consistently during their younger and middle-age years had a decreased risk of cataracts. However, the study isn't conclusive and advises women that large doses of vitamin C shouldn't be taken without the advice of their health care provider because it may cause renal calculi.

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Special considerations

Consider these patient care measures after surgery to extract a cataract:

• Because the patient will be discharged after she recovers from anesthesia, remind her to return for a checkup the next day, and warn her to avoid activities that increase intraocular pressure such as strainmg.
• Urge the patient to protect the eye, from accidental injury at night by wearing a plastic or metal shield with perforations; a shield or glasses should be worn for protection during the day.
• Before discharge, teach the patient to administer antibiotic ointment or drops to prevent infection and steroids to reduce inflammation; combination steroid-antibiotic eye drops can also be used.
• Advise the patient to watch for the development of complications, such as a sharp pain in the eye uncontrolled by analgesics as a result of hyphema, or clouding in the anterior chamber (which may herald an infection), and to report them immediately.
• Caution the patient about activity restrictions, and advise her that she'll receive her connective reading glasses or lenses in several weeks.