What is the lens?
The lens is a small transparent structure in the eye, which helps in focusing light rays. It is a biconvex disc made up of mostly water and proteins. It is comparable to a small bag full of transparent material. When light rays enter the eye they have to pass through the transparent cornea and the lens before they make an image on the retina.
What is cataract?
The clouding of the lens is called a cataract. Due to the opacity (or clouding) of the lens, the light rays cannot reach the retina with the same clarity and this leads to a deformed image. A person may be born with cataract or it may develop at any time during a person’s life.
What are the types of cataract?
* Senile cataract: Most cataracts are the result of age-related degenerative changes in the lens. By the age of 90 years nearly 98% of people suffer from cataract. The main factors thought to cause cataract are sunlight exposure, smoking, systemic diseases and poor nutritional status.
* Congenital cataract: Babies may have cataract at birth. Some infections and metabolic disorders may lead to the opacity of the lens during gestation.
* Traumatic cataract: Any trauma (blunt or penetrating) may lead to cataract formation.
* Secondary cataract: When the cause of cataract is some other primary pathology in the eye.
What are the symptoms?
The most important symptom is a decrease in near and distance vision. The vision will be cloudy and blurred, colours will be faded and contrast will be reduced. There will be a glare problem and a scattering of light. Some may have double vision and there may be difficulty in night vision. In the advanced stages one may see a white reflex in the centre of the pupil.
Cataract directly reduces the sharpness of vision. Initially people may find difficulty in night driving, later it may affect all tasks at near and far distance. Cataract can directly affect the quality of life and is often related to a higher risk for accidents. Cataract may progress very slowly so one may not be able to appreciate the gradual decrease in vision.
What is the treatment?
Surgery is the only scientific and proven method of treatment for cataract. Many eye drops are marketed for the prevention of cataract, but they are as good as a placebo in many studies. Cataract is one of the most common surgeries performed world wide. Cataract surgery has more than a 90% success rate, which means more than 90% of people will have better vision after the surgery.
When should I opt for the surgery?
The decision is entirely up to the patient. Whenever the patient feels his vision has decreased to a level where it interferes with his daily routine or professional needs, he can be operated on. It is no longer advised to wait till the cataract becomes mature. Rather, early surgery has fewer complications and a better surgical outcome.
What are the methods for surgery?
Generally any of the three methods below are performed,
* Extra capsular lens extraction(ECCE),
* Small incision cataract surgery (SICS)
* Phacoemulsification
Extra capsular cataract extraction: In this method an 8-12 mm incision is made, and the cataract is extracted manually. After the cataract has been removed, an artificial lens is placed inside and the incision is sutured back with the help of 5-8 very fine sutures (stitches).
Small incision cataract surgery: In this method a 5-8 mm incision in made in the sclera and through the incision the lens is extracted manually. After cataract removal an artificial lens is put in place and the incision is closed by 1-2 stitches – or no stitches may be needed.
Phacoemulsification: This is the best method for cataract removal so far. In this method a small incision of 2.8 mm is made and the cataract is removed with the help of a machine known as phacoemulsifier. The machine has a probe which delivers ultrasonic energy through a needle to the lens. The lens is broken up into many pieces and then sucked out by the same probe. After cataract removal, an artificial lens is implanted and generally no stitch is required.
Fig 2 Incision size and placement site in different cataract surgeries
What are the advantages of phacoemulsification surgery?
With regards to ECCE and SICS, the incision made during the surgery leads to changes in corneal curvature. This is called surgically induced astigmatism. The bigger the incision is, the greater will be the induced astigmatism. In phacoemulsification the incision size is small (2.8 mm) and thus it creates minimal astigmatism when compared with other techniques (ECCE 8-12mm and SICS 6-8mm). The small incision is self sealing and more stable, thus it allows a very fast rehabilitation in comparison to the other techniques. The patient requires fewer follow-up visits, and performs better in early post-operative days.
The phaco machine works with high vacuum which helps in a good cortical clean-up and capsular polishing. This enhances the quality of vision in the long term and makes it superior over SICS and ECCE.
In conclusion: Whenever available, in modern eye care phacoemulsification is preferable to other methods of cataract surgery, due to its distinct advantages. It is also advisable to have surgery done in the early stage of cataract than waiting for it to ‘mature.’
