Cataract
A cataract is a cloudy or opaque area in the lens of the eye. The lens of an eye is normally clear. If the lens becomes cloudy, the condition is known as a cataract. Rarely, cataracts may be present at or shortly after birth. These are called congenital cataracts. Adult cataracts usually develop with advancing age and may run in families. Cataracts are accelerated by environmental factors, such as smoking or exposure to other toxic substances, or they may develop at any time after an eye injury. Metabolic diseases such as diabetes also greatly increase the risk for cataracts. Certain medications, such as cortisone, can also accelerate cataract formation. Vision problems associated with cataracts generally progress to decreased visual acuity, even in daylight.

Adult cataracts are classified as immature, mature, and hypermature. A lens that has some remaining clear areas is referred to as an immature cataract. A mature cataract is completely opaque. A hypermature cataract has a liquefied surface that leaks through the capsule and may cause inflammation of other structures in the eye.

Cataract is diagnosed by a Standard ophthalmic examination, including slit lamp examination. Ultrasonography of the eye may also be carried out in preparation for cataract surgery. Other tests that may be done (rarely) include: Glare test; Contrast sensitivity test; Potential vision test; and Specular microscopy of the cornea in preparation for cataract surgery.

The only treatment for cataract is surgical removal. This is done when a person cannot see well enough with glasses to perform normal activities. For some people, changing glasses, getting stronger bifocals, or using a magnifying lens is helpful enough. Others choose to have cataract surgery. Cataract surgery consists of removing the lens of the eye and replacing it with an artificial lens. A cataract surgeon will discuss the options with the patient, and together they will decide which type of removal and lens replacement is best.

There are 2 types of surgery that can be used to remove lenses that have a cataract. Extracapsular surgery consists of surgically removing the lens, but leaving the back half of the capsule (the outer covering of the lens) intact. High-frequency sound waves (phacoemulsification) may be used to soften the lens to facilitate removal through a smaller incision. Intracapsular surgery involves surgically removing the entire lens, including the capsule. Today this procedure is done very rarely.

People who have cataract surgery are usually fitted with an artificial lens at the same time. The artificial lens is a synthetic disc called an intraocular lens. It is usually placed in the lens capsule inside the eye. Other options include contact lenses and cataract glasses. Surgery can be done in an outpatient center or hospital. Most people do not need to stay overnight in a hospital. For most people, cataract surgery has a low risk of complications. With implanted artificial lenses, most people no longer need corrective lenses for distance vision. Glasses are usually necessary for reading.

Corneal Surgery
Corneal surgery corrects mild to moderate nearsightedness (myopia). Procedures are also available for farsightedness and astigmatism. Topical anesthesia (numbing eye drops) is used. The exact surgical method depends on the patient. In many cases, the ophthalmic surgeon will use an instrument called a keratome to lift a piece of tissue from the surface of the cornea. A laser re-shapes the surface of the cornea and the tissue is put back into place. The procedure is usually painless and the improvement in vision is usually immediate. The patient can quickly return to most activities, but must avoid bumping the eye or submerging in water (swimming, for example). This method of refractive surgery offers fewer side effects compared to radial keratotomy, which was common in the 1980's. Usually both eyes are done in the same session.

Refractive surgery is used to treat nearsightedness so that corrective lenses will no longer be necessary. Most forms of nearsightedness can be reliably corrected. For those older patients who needed bifocals before surgery, reading glasses will still be needed even though distance vision may be clear without glasses.

Eye muscle repair
Eye muscle repair is surgery to align eyes or correct eye muscle abnormality (strabismus). The surgery is most commonly done on children, but is also performed on adults with similar problems. While the child is under general anesthesia (asleep and pain-free), a small incision is made in the tissue between the eye and eyelid (conjunctiva ). One or more of the muscles of the eye are strengthened (resected) or weakened (recessed) to allow proper position and help the eye to move correctly. After a few hours of recovery, the child may go home. The surgery for adults is similar. Adults are usually awake or sleepy, but pain-free. Often, in adult surgery, an adjustable suture will be used so that minor adjustments can be made later that day or the next day. This technique usually gives a very good result. Surgery may be recommended when strabismus or crossed eyes does not respond to medicine or glasses.

Glaucoma
Glaucoma refers to a group of disorders that lead to damage to the optic nerve, the nerve that carries visual information from the eye to the brain. Damage to the optic nerve causes vision loss, which may progress to blindness. Most people with glaucoma have increased fluid pressure in the eye, a condition known as increased intraocular pressure.
There are four major types of glaucoma:
(i) Open angle (chronic) glaucoma;
(ii) Angle closure (acute) glaucoma;
(iii) Congenital glaucoma;
(iv) Secondary glaucoma.
The buildup of fluid in the anterior chamber of the eye causes increased pressure in the eye. This increased pressure pushes on the junction of the optic nerve and the retina at the back of the eye, reducing the blood supply to the optic nerve. As the optic nerve deteriorates due to decreased blood supply, blind spots develop in the field of vision. If you have had acute glaucoma in one eye, you are almost certainly at risk for an attack in the second eye. Secondary glaucoma is caused by other diseases, including eye diseases such as uveitis, systemic diseases, and drugs such as corticosteroids. Congenital glaucoma, which is present at birth, is the result of abnormal development of the fluid outflow channels of the eye. Surgery is required for correction. Congenital glaucoma is often hereditary.

The objective of treatment is to reduce intraocular pressure. Depending on the type of glaucoma, this is achieved by medications or by surgery. Most people with open angle glaucoma can be treated successfully with eye drops. Some patients will need additional forms of treatment, such as a laser treatment, to help open the fluid outflow channels. This procedure is usually painless. Others may need traditional surgery to open a new outflow channel. Acute angle closure attack is a medical emergency. The patient may also need an emergency operation, called an iridotomy. Congenital glaucoma is almost always treated with surgery to open the outflow channels of the angle.

LASIK eye surgery
LASIK is a surgical procedure that can reduce a person's dependency on glasses or contact lenses. The procedure permanently changes the shape of the cornea (the delicate clear covering on the front of the eye). For clear vision, the eye's cornea and lens must bend (refract) light rays properly, so that images are focused on the retina. If the light rays aren't clearly focused on the retina, the blurred images are seen. This blurriness is referred to as a "refractive error." It is caused by an imperfectly shaped eyeball, cornea, or lens. LASIK uses an Excimer Laser (an ultraviolet laser) to precisely remove corneal tissue to correct the shape for better focusing. LASIK eye surgery is performed most often on people who have nearsightedness (myopia), which means that they only clearly see nearby objects; anything far away is blurry. LASIK is an outpatient surgical procedure and will take 10 to 15 minutes for each eye. LASIK may be done on one or both eyes during the same session. During LASIK, a special knife (a microkeratome) is used to cut a hinged flap of corneal tissue off the outer layer of the eyeball. The flap is lifted out of the way and a special laser is used to reshape the underlying corneal tissue. The calculation for how much tissue is removed by the laser is done ahead of time. Once the reshaping is done, the surgeon replaces and secures the flap. No stitches are needed. An eye shield or patch will be placed over the eye to protect the flap and to help prevent rubbing or pressure on the eye until it has had enough time to heal.

Visual Field Testing
The visual field is the total area in which objects can be seen in the peripheral vision while the eye is focused on a central point. Confrontation visual field exam: A quick and basic evaluation of the visual field done by an examiner sitting directly in front of you. With one eye covered, one is asked to look at the examiner's eye and tell when s/he can see the examiners hand.

Tangent screen or Goldmann field exam: one will be asked to sit about 3 feet from a screen with a target in the center. S/he will be asked to stare at the central target and let the examiner know when s/he can see an object brought into your peripheral vision. The extent of your peripheral vision is mapped.

Automated perimetry: One sits in front of a concave dome and stare at a central target within the dome. A computer-driven program flashes small lights at different locations within the dome's surface, and s/he presses a button when s/he sees the small lights in your peripheral vision. The responses are compared to age-matched controls to determine the presence of defects within the visual field.

The test will detect any loss of peripheral vision and provide a map of that loss which will be helpful in diagnosing the cause. Abnormal results may indicate diseases or central nervous system problems such as tumors that damage or compress the parts of the brain that deal with vision. Other diseases that may affect the visual field of the eye include diabetes, hyperthyroidism (a condition where the thyroid produces an excess of hormones), hypertension, diseases of the pituitary gland, and multiple sclerosis.

(Information given here has been abridged from authentic sources like NIH, USA)