A cataract is a clouding or opacification of the lens (normally clear) of the eye or its capsule (surrounding transparent membrane) that obscures the passage of light through the lens to the retina of the eye. This blinding disease can affect infants, adults, and older people but it predominates the latter group. It can be bilateral and vary in severity. The disease process progresses gradually without affecting daily activities early on, but with time, especially after fourth or fifth decade, the cataract will eventually mature making the lens completely opaque to light interfering with routine activities. Cataracts are a significant cause of blindness worldwide. Treatment options include correction with refractive glasses only at earlier stages and if cataract mature enough to interfere with routine activities, surgery may be advised, which is very fruitful.
Multiple factors responsible for developing cataracts include the following:
Congenital Cataract: Can be unilateral or bilateral - studies have documented a close association between congenital cataract and maternal nutrition, infections (rubella & German measles) and deficiency of oxygenation due to placental hemorrhage.
Age-related (Senile Cataract): Most common type of cataract
Primary Ocular Diseases:
Drugs: Corticosteroids and anticholinesterase inhibitors can cause both posterior and anterior subcapsular opacities respectively
Poor Nutrition: a diet deficient in anti-oxidants and vitamins
Prevalence and Incidence
Many studies in 2010 reveal that cataracts are most common in the White American race, where prevalence ranges from 17 to 18% per 100 people. Blacks were the second highest affected by cataracts with a 13% prevalence rate followed by Hispanics with a prevalence rate of almost 12%.
Onset is gradual and progressive commonly in old age group, typically in the fifth and sixth decade, though cases have been reported in children and the elderly as well.
Recent studies reveal that the disease is more common in women than men, with a male to female ratio of 1 to approximately 1.3.
The lens is a transparent structure made up of fibers (modified epithelial cells) enclosed in a membranous structure called lens capsule. Lens matter consists of two main parts:
Many degenerative processes denature and coagulate lens proteins present in lens fibers by different mechanisms which result in loss of transparency and ultimately cataract formation. The various mechanisms involved are as follows:
All these processes ultimately lead to an opaque lens behind the pupil making it extremely difficult for the patient to carry on with routine activities.
The patient may present with one of the following symptoms:
Following findings can be noticed during a thorough ophthalmic examination depending upon the part of the lens involved:
Cataracts can be evaluated by a number of steps as follows:
Comprehensive ophthalmic examination
The following investigations can help diagnose and plan the management of the disease:
The treatment choice depends upon the degree of opacity sufficient enough to cause difficulty in performing essential daily activities. Following treatment modalities are available:
The differential diagnosis of cataract includes many disorders such as:
Prognosis of cataract depends upon multiple factors such as:
In most cases, surgery restores vision very effectively. Presence of another systemic disease, time of intervention, and mode of surgery can be instrumental in determining the visual outcome. Recent studies reveal that in most of the cases the prognosis is excellent after surgery almost 70 to 80%. Most patients show excellent results after surgery if they strictly follow postoperative instructions and medication regimens advised by their ophthalmologist. A routine eye examination is advisable which will detect any cataract development in the other eye. Many patients with a monofocal IOL may require refractive glasses to achieve their best visual acuity after surgical cataract removal. Gradual opacification of the posterior capsule can develop in a large number of patients that can affect the patient's vision (secondary cataract).
Cataract cause multiple complications discussed as follows:
Congenital Cataract: These can be disease related or surgery related:
Acquired Cataract: These can be disease related or surgery related:
The patients should receive education about:
Visual acuity charts and slit lamp examination should be used on regular bases at every follow-up to detect any impairment in visual acuity, after cataract or any complication of the surgery. The patient should be advised to wear spectacles in the sunlight to avoid damage by ultraviolet rays. A thorough systemic evaluation is advisable to rule out any systemic disease which may affect the outcome of the treatment.
Anytime a patient visits a clinic or emergency department for symptoms of visual impairment the primary care provider should be responsible for quick referral of the patient to an ophthalmologist. The management of cataract differs based on the severity of disease, visual impairment, and age of the patient. The mainstay of treatment is usually surgical cataract extraction. Patients who have mild symptoms can receive treatment as an outpatient with refractive glasses and pupillary dilatation. Those with more severe disease or with advanced age should be advised elective surgery as a day-case procedure.
Response to refractive glasses in the early stage of cataract is usually satisfactory. If outpatient therapy by refractive glasses and pupillary dilatation fails to show improvement, patients should undergo hospitalization for surgical cataract removal with intraocular lens implantation. No studies have revealed any link between prescription of systemic steroids or steroids eye drops and the recurrence or complication of cataract, and thus steroids are not routinely prescribed. For most patients who obtain prompt treatment, the results are excellent, but for those who have a delay in treatment or have a mature or complicated disease, there may be steady or poor vision following recovery.
Diagnosis and treatment of cataracts require an interdisciplinary team approach, to include primary care providers (physicians, PAs, NPs), specialists (ophthalmologists, ophthalmic surgeons), and nursing support. This approach helps to ensure timely and effective patient care and optimal outcomes. [Level V]
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