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Ultrasonography: It is the use of sonic waves in ophthalmologic tests. High frequency sound waves are used to probe and view the inner eye when other instruments prove ineffective. The sonic waves are directed to the eye, and the echoing sounds are translated into a picture. Ultrasonography is used to examine the tissues of the eye for the presence of tumors, retinal detachments, or fractures. It may also be performed after glaucoma surgery to review results. It is also used to take measurements of the eye or to determine the health of the underlying retina in presurgical tests for cataract surgery. The A-scan applies ultrasonography to measure the length of the eye to determine the correct strength of intraocular lens needed for cataract surgery. The B-scan uses the sound waves to view a retina obscured by a dense cataract.
Uvea, or uveal tract: It is a heavily vascularized layer that supplies blood to the eye. It includes the melanin-pigmented portions of the eye: the iris and ciliary body in the front of the eye, and the choroid to the back of the eye. Disorders of the uvea may include inflammations (uveitis), injuries, or infections. Uveitis is a common disorder, causing inflammation of the uveal tract. Anterior uveitis (or iridocyclitis) occurs when the inflammation involves the iris and the ciliary body. Symptoms include redness, light sensitivity, blurred vision, and extreme pain, especially when focusing on near objects. Posterior uveitis (or choroiditis) involves the choroid, the layer of blood vessels between the retina and sclera. Posterior uveitis is not usually as painful as anterior uveitis; but there is still redness, blurred or lost vision, light sensitivity, and the appearance of floaters in the line of vision. If the uveitis remains in the area of peripheral vision, the symptoms may not be noticed.