How You See
Light enters the eye and focuses on the retina
The eye functions like a camera. Light rays enter the eye through the cornea (the clear front window), pass through the pupil (the hole in the center of the iris), and then through the lens, finally reaching the retina (the film) at the back of the eye. When light rays land on the retina, they form an upside-down image. The retina converts the image into impulses that travel through the optic nerve to the brain, which converts them into upright visual images.
Vision is clear only if the cornea and lens correctly bend or "refract" the light rays and focus them on the retina. Blurry vision may be due to what is called a "refractive error" --- the failure of the cornea and lens to focus light properly. Prescription eye glasses, contact lenses, and refractive surgery correct or improve refractive errors by focusing light rays closer to, or directly onto, the retina.
What is Cataract?
Cataract is clouding of the lens in the eye.
Normally light enters the eye from the front, passes through a clear lens, and reaches the retina so one can see. If the lens becomes cloudy, light cannot pass through properly leading to blurred vision.
Most people with cataracts have it in both eyes. However, one eye may be worse than the other because each cataract develops at a different rate. The rate of progression also varies from person to person. In most, the cataract slowly becomes increasingly dense over years, but in others it may mature in a shorter time.
What Will You Feel If You Have Cataracts?
Some people with cataract may not even know it. Their cataract may be immature, or the changes in their vision may not bother them. Whilst in others, the cataract impairs their vision and disrupts their daily activities.
Here are some signs of a cataract:
- Cloudy or foggy vision.
- Changes in the way one sees colours.
- Problems with driving at night because headlights seem too bright.
- Problems with glare from lamps or the sun
- Frequent change in spectacle prescription
- Double vision
- Poor night vision
How Will The Doctor Know You Have It?
During your visit to our eye specialists, we will check your vision and spectacle power. We will use special eye drops to dilate your eyes temporarily. The eye specialist will then look at your dilated eye to assess the presence of a cataract as well as conduct a general eye screen for any other eye disease that may be causing your visual symptoms.
How Is It treated?
Insertion of new lens
The most effective treatment for cataracts is a small operation to remove the cloudy lens, and replacing it with a lens implant. It is highly successful, with a complication rate less than 1 %. Not all cataracts require surgery, and for some, a change in their glasses, stronger bifocals, or the use of magnifying glasses may improve the vision to an acceptable level.
For others who cannot see well enough with glasses to perform their normal activities, surgery is indicated. Usually the patient can decide if, and at what stage to have the operation. In the past, eye specialists often waited until the cataract became “ripe” before suggesting surgery. Nowadays, with modern surgery the operation can be carried out at any stage of the cataract’s development.
Following the removal of the cataract, an artificial implant is needed to substitute the function of the natural lens. In the past, this was achieved by the use of thick cataract glasses, or contact lenses. Nowadays, lens implants are routinely used. These are silicone or acrylic discs implanted inside the eyeball during cataract surgery. The standard lenses used are monofocal i.e. allows clear vision in the distance but requires reading glasses for near. Other implants include multifocal and accommodative lenses. Both allow the eye to focus at various distances.
What Lenses Are Available?
Conventional monofocal lens implants inserted after cataract extraction allows you to see far clearly, but would still require you to use reading glasses for near work or reading.
|Multifocal Lenses |
Now, you may choose special multifocal lens implants, which will allow you to see clearly for distance as well as near. A range of new multifocal lens are available at the NUH Eye Surgery Centre.
What You Should Know?
As in all surgical procedures, there are some side effects that may occur after cataract surgery. While this surgery is very accurate, perfect vision cannot be guaranteed.
Cataract surgery is usually safe, but complications can occur e.g. infection, retinal detachment. It is important to seek prompt consultation if one experiences loss of vision, excessive pain or increase in eye redness following cataract surgery.
Cataracts cannot recur after surgery. Occasionally the lens capsule holding the intraocular lens may become cloudy and cause vision to deteriorate months or years later. This can be treated with a simple outpatient laser procedure called YAG capsulotomy.
Once a decision to have an operation is made, certain tests are required before surgery. Eye investigations are carried out to determine the strength of the implant to be placed in the eye during surgery. One may also need to undergo blood tests, chest X-ray, and ECG (electrocardiogram) to ensure fitness for operation. Almost all operations for cataract are performed on a day care basis. There is no need for hospitalisation.
Frequently Asked Questions
1. How long does cataract surgery take?
- Registration to discharge 3 hours
- Actual surgery 20 to 45 minutes
2. Is it painful?
Anaesthetic eye drops or injection will be given, so no pain will be felt during surgery.
3. Can I use Medisave?
4. How long does it take to recover?
Improvement in vision by the next day. Good, stable vision by 1 week after phacoemulsification and 1 month after extracapsular surgery.
5. When can I exercise or swim?
Light exercise after one week No swimming for 2 weeks
6. Can the cataract regrow?
No, once removed, the cataract will not form again. Occasionally, the lens capsule holding the intraocular lens may become cloudy and cause a drop in vision months to years later. This can be treated with a simple outpatient laser procedure called YAG capsulotomy.
7. Can cataract surgery cure my short-sightedness?
Yes, the power of the intraocular lens implant is tailored according to the amount of myopia or hyperopia the patient has. This lens, however, does not correct astigmatism. Any remaining astigmatism can be corrected by wearing glasses or undergoing a laser vision correction.