LASIK and Cataract

Topic Highlights

●    This visual presentation covers two topics, both LASIK & Cataract.

●    The first section on LASIK discusses in detail the anatomy of the eye, the function of the eye, refractory errors of the eye, correction with LASIK, advantages of LASIK, and steps to be taken during recovery.

●    The second section on Cataract deals with the condition in which the eye lens is clouded and affects vision, diagnosis of cataract, surgery, and recovery after surgery.

Transcript

The eye is a very complex sense organ which responds to changes in light and enables us to see. The ability to see depends on various structures in the eye. The outermost part of the eye is the eyelid, which protects the eye and lubricates the eyeball. The outermost layer of the eye is the sclera, the white of the eye. Muscles connected to the sclera control eye movements. The cornea is transparent and covers the front of the eye. It is a powerful refracting surface where light rays are bent, refracted and focused.

The colored part of the eye is called the iris. It controls light levels inside the eye. The pupil is the round opening in the center of the iris. Dilator and sphincter muscles of the iris change the pupil size according to the amount of light. The soft lens located behind the pupil allows the muscles to adjust its shape and focus. This allows us to focus on something close to us and far away. The retina is a sensory tissue lining the back of the eye. The lens focuses light in the retina with the help of muscles attached to it. Photoreceptors in the retina capture light rays and convert them into electrical impulses. The optic nerve carries these impulses to the brain.

Myopia, or short sight, is the inability to see distant objects as clearly as near objects. With myopia, the cornea is too steep, causing images to focus in front of the retina instead of directly on it. Persons with hyperopia, or long sight, have more difficulty seeing near objects as clearly as distant objects. Hyperopia occurs when the cornea is too flat, causing images to focus behind the retina. People with astigmatism have distortion of the image on the retina caused by irregularities in the cornea or lens of the eye.

There are many different treatments available depending on the individual's needs. Glasses or contact lenses are designed to compensate for the eye's imperfections. Several new techniques such as LASIK offer millions of people the opportunity to reduce or eliminate their need for glasses or contact lenses. LASIK, or laser-assisted in situ keratomileusis, is a surgical procedure which can correct a wide range of refractive errors such as myopia, hyperopia and astigmatism.

To be eligible for LASIK surgery, the patient should be over 18 and should not suffer from aliments such as diabetes and eye diseases. Patients should not be taking medications such as steroids. Women should not be pregnant or breast-feeding. People with unstable vision are not eligible for LASIK. Vision should be stable at least for a year. People with large pupils are not eligible.

A baseline evaluation of the eye is done to decide whether the patient is a candidate for surgery. Current medical history is also discussed. When surgery is scheduled, patients are advised on preparation for surgery. Contact lens wearers need to discontinue and switch to glasses at least 2 weeks prior to surgery in the case of soft contact lenses, 3 weeks in case of rigid gas permeable lenses and 4 weeks in the case of hard lens. Cosmetics should be avoided the day before surgery.

Before LASIK surgery, anesthetic drops are administered into the eyes. A suction ring is placed on the eye to stabilize and check the eye pressure. The microkeratome, a cutting instrument, is attached to the suction ring. A thin flap of the cornea is lifted and the inner tissue of the cornea is exposed. The exposed layer of the cornea is then reshaped with an excimer laser. Each pulse removes a microscopic layer. The actual laser treatment typically lasts less than one minute. The flap is folded back over the eye and the cornea heals naturally without the need for stitches.

To treat nearsightedness, the laser removes tissue from the center of the cornea, thereby making it flatter. In the case of farsightedness, the central part of the cornea is made steeper. This is done by directing the laser beam to remove tissue from around this area. To treat astigmatism, the cornea is made more spherical. This is done by removing tissue in one direction more than the other by changing the pattern of the beam.

Surgery usually takes less than 5 minutes for each eye. Patients often experience a blurring of vision immediately after the surgery. Patients are given eye shields to protect the eye from touching or rubbing. Eye drops are administered to prevent eye infections. Vision improves and continues to clear. Pain is rare and mild, and goes away in a few hours. Patients may experience dry eyes, sensitivity to light, and glare and halos, which normally subside as the eyes heal. Artificial tears are used to lubricate the eye. The patient should avoid contact sports and swimming for a couple of days. The patient is also advised to avoid any lotions or creams near the eyes for two weeks following surgery. Strenuous work should be avoided the four weeks following surgery. Eyes are examined and tested within the next two days.

While good vision is possible, expectations of perfection may be unrealistic. Some people require glasses for fine tuning vision for conditions such as night driving, computer work and heavy reading. Complications of surgery, though rare, may occur in less than 1% of the patients. Overcorrection or undercorrections can happen occasionally. In this case the patient is prescribed contact lenses or glasses. The flap could develop wrinkles, which may need repositioning. Some patients develop problems in night vision such as glare or halo. Permanent dry eye is another complication, which can be treated with artificial tears. In rare cases repeat surgery may be done after 3 months by raising the same flap.

Cataract is clouding of the lens of the eye due to the deposition of proteins, which obstructs the passage of light. It can result in a partial or severe decrease in vision. Cataract is a significant cause of low vision or blindness. Age related cataract is responsible for 48% of blindness in the world, which is nearly 18 million people. The number of people suffering from cataract is growing as people live longer.

Cataract may cause cloudy, fuzzy or blurred vision and faded colors, halo around lights, double vision, and poor night vision. Cataracts usually progress gradually. Most age-related cataracts may progress over a period of two years. Other types of cataracts, especially in younger people and diabetics, may progress faster.

The majority of cataracts are related to aging, although cataracts are sometimes seen in babies. This type of cataract is called congenital cataract. Cataracts may also develop as a result of other diseases such as diabetes or trauma to the eye. Medications such as steroids and long-term exposure to sun may cause cataracts.

Cataracts are classified according to the location on the lens. Nuclear cataract is usually associated with aging and is the most common type of cataract. Nuclear cataracts develop in the center of the lens. Cortical cataract develops in the lens cortex, and gradually spreads its wedge shaped spokes towards the center of the lens. This is more common among people with diabetes. It may impair both distance and near vision and may require surgery at early stages. Subcapsular cataract develops at the back of the lens. People with diabetes, high myopia and those taking high doses of steroids are more susceptible.

Your doctor will examine the eyes thoroughly. Glare testing and contrast sensitivity tests are sometimes done. Cataracts can only be removed with surgery and the decision for surgery depends on the loss of vision. Even after surgery problems such as macular degeneration, glaucoma and diabetes may affect vision in some people. The chances of restoring good vision following the surgery are excellent depending on the health of the eyes.

Anesthetic drops are used to numb the eye and a small incision about 3mm is made on the cornea. Special microsurgical instruments break the cataract in a process called phacoemulsification and suck the fragments of the lens from the eye. The back portion of the lens capsule is left intact to support the small foldable intraocular lens, which is folded and inserted through the wound. It is then opened and implanted in place of the natural lens. The lens is held in place by the arms of the lens, known as haptics. The incision is self-sealing so no stitches are needed.

Patients may be asked to wear a shield to protect the eye, especially while sleeping. Avoid rubbing the eyes during the first few weeks following surgery. Antibiotic and anti-inflammatory eye drops will be administered during the first few days. Your surgeon may prescribe new glasses after vision has stabilized. This may take four to six weeks. Patients can resume normal activities following surgery. Patients may read, watch television or do light work.

Cataract surgery is generally safe. In rare cases infection, inflammation or bleeding may occur in the eye following surgery. Dislocation of the implanted lens and retinal detachment are also possible complications. A thickening of the membrane behind the lens known as after cataract may occur months later.