Cataract

Introduction

Cataract is a clouding or opacity of the lens in the eyes that leads to a gradual loss of vision. It is one of the leading causes of blindness throughout the world especially in elderly people. In the Asian sub-continent, millions of people are affected by cataract.





Cause and Pathogenesis

Cataracts are associated primarily with ageing (senile cataracts) and changes in the chemical composition of lens proteins. Injuries, toxins, systemic disease, and intraocular inflammation can also cause cataract. Cataracts occurring at birth (congenital cataracts), are rare, and are the result of inborn errors of metabolism, exposure of a first-trimester foetus to rubella (german measles) or toxins, and congenital anomalies. Excessive exposure to ultra-violet light, and use of certain steroids might also lead to the development of cataract. More than 60% of those over 65 years of age and 90% of those over age of 85 have opacities of the lens.

Symptoms and Signs


The main symptoms of cataract include progressive, painless blurring and distortion of vision, glare from bright lights, and gradual loss of vision. Signs include a gray or white colouring on the pupil and myopia may also occur. Colour vision is also affected and objects may appear yellow. Halos or coloured rings may form around bright lights.

Investigations and Diagnosis


The following tests can be done to assess the eyesight and detect the development of cataract:

Visual Acuity Test, to assess distant and near vision
Refraction, to verify the strength of correction needed for best possible vision
Slit-lamp Examination, to detect abnormalities in the cornea, iris and lens
Tonometry, to check the intraocular pressure
Ophthalmoscopy, to detect abnormalities of the retina and optic nerve





Treatment and Prognosis

Surgery is the main treatment for cataract and produces the best results. Intracapsular or extracapsular removal of the lens can be performed and later, follow-up laser surgery to remove secondary membranes can be performed. Phaco- emulsification can be done. After the cataract is removed, intra-ocular lens (implanted at the same time as the lens is removed), contact lenses or glasses can be used to correct the refractive errors. After correction of the refractive errors, the patient will be able to regain good eyesight and perform most of the normal activities.

Prevention


Cataract is mainly a disease that occurs in the elderly people and tends to develop as the age increases. However, proper care of the eyes and control of the causative factors like injuries to the eyes, diabetes and hypertension can prevent the cataracts that develop due to these causes.