VISUAL FIELD TEST
Visual field testing (perimetry) is used to check the whole area that each eye can see (the visual field). The development of blank sections in the visual field may be casued by various underlying disorders. Many eye disorders cause characteristic visual field defects that can develop without being noticed. Testing allows early detection and treatment.
VISUAL FIELD TEST
One eye is covered while you look at a central target inside the test bowl. When you see lights flashing in different parts or your visual field, you press a response button.
SURGERY FOR REFRACTIVE EFFORS
Surgery can be used to correct some refractive errors permanently. The three main surgical techniques.The three main surgical techniques are—laser-assisted in-situkeratomileusis (LASIK), radial keratotomy (RK), and photorefractive keratectomy (PRK). LASIK, in which the cornea is reshaped by a laser, causes the least scarring and is the most widely used method. RK, in which the cornea is flattened by scalpel cuts, can weaken the cornea. In PRK, areas of the cornea are shaved away by laser and mild corneal scarring may result.
VISION TEST
You should have your vision tested once every 2 years, especially if you are over age 40. The most common vision tests assess the acuity (sharpness) of you distance vision and your ability to focus on near objects. The tests also show which corrective lenses, if any, you need. Additional tests for specific eye disorders, such as glaucoma may be performed, depending on your age and medical history.
HAVING A VISION TEST
Lenses in the phoropter are changed until you can read letter near the bottom of the Snellen chart.This enables the ophthalologist to make the appropriate prescription for you corrective lenses.
OPHTHALMOSOCPY
In this technique an instrument called an ophthamloscope is used to examine the inside of the eye. You will be asked to focus on a distant object while the instrument directs a beam of light into your eye. Through the lenses in the ophthalmoscope the ophthalmologist can examine the light-sensitive retina; the retianal blood vessesl; the head of the optic nerve, which carries nerve signals from the eye to the brain; and the jellylike vitreous humour, which fills the back of the eye. Ophthalmoscopy is painless, but if eyedrops are used to dilate the pupils you vision may become temporarily blurry.
TRABECULECTOMY
This surgical technique is used to treat chronic glaucoma in which the pressure in the eye gradually rises due to a blockage of the trabecular meshwork, a sievelike structure through which the fluid in the eye normaly drains. Trebeculectomy may be done under general or local anesthesia and involves cutting out a section of the blocked meshword so that fluid can flow freely out of the eye. Your doctor may advise you to wear an eye shield for a few days while the eye heals. You should also avoid strenuous activity for severa weeks after the procedure.
APPLANATION TONOMETRY
The eye condition glaucoma, in which the pressure inside the eye is elevated can be detected using an instrument called an applanation tomometer. Anesthetic drops are put into your eye, then the tonometer is pressed gently against the cornea, the transparent front part of the eye and the force needed to flatten the cornea is measured. The test takes only a few seconds and is painless.
During the test the tonometer is held against the cornea. As the internal pressure is measured, the pressure on your eye will increase slightly.
FLUORESCEIN ANGIOGRAPHY
This technique is used to study the blood vessels in the light-sensitive retina of the eye. A fluorescent dye (fluorescein) is injected into the circulatory system through one of the veins in the arm. As the dye passess through the retinal vessels, a series of photograps (fluorescein angiograms) is taken to define any underlying abnormalities. The ophthalmologist can then assess the extent of the damage. The test is painless, but your skin and urine may turn dark yellow untill all the dye has been excreted.
CATARACT SURGERY
A cataract is an opaque region in the lens of the eye causing loss of vision. During cataract surgery, the affected lens is removed and repalced with an artificial lens. The operation is usually performed under local anesthesia, and you will probably be able to go home the same day. In the technique shown here, the lens is first softened by an ultrasound probe. The softened tissue is extracted, and a new lens is inserted.
LASER SURGERY FOR RETINOPATHY
Laser surgery is used in diabetic retinopathy to destroy abnormal blood vessels growing out from the retina and to prevent abnormal vessesls from forming.Treatement is performed under local anaesthesia, usually over several sessions.The laser makes thousands of tiny circular burns that destroy parts of the outer retina and associated blood parts of the outer retina and associated blood vessels but leave the macular area of the retina intact. Some outer vision may be lost, but blindness is prevented.
SLIT-LAMP EXAMINATION
The slit-lamp is used to examine structures at the front of the eye: the transparent cornea, which covers the front part of the eye; the coloured iris; the lens; and the front chamber, which lies between the cornea and the lens. The slit lamp produces a long, narrow beam of brilliant light that is focused onto the eye. Althought the examination is painless, eye drops used to dilate the pupil may make your vision blurry for a few hours afterward.