eye disorders
Evaluation of the Ophthalmologic Patient
Testing
 0.5%). Another handheld tonometer, the iCare tonometer, measures rebound time of a small lightweight probe and can be used without topical anesthesia. It is useful in children and is widely used in emergency departments by nonophthalmologists. Office-based screening with noncontact air-puff tonometry also can be used; it requires less training because it makes no direct corneal contact. Goldmann applanation tonometry is the most accurate method but requires more training and typically is used only by ophthalmologists. Measurement of intraocular pressure alone is not adequate screening for Overview of Glaucoma ; the optic nerve also should be examined. Fluoresceinangiographyis used to investigate perfusion, leakage from blood vessels, and neovascularization in conditions such as diabetes, age-related macular degeneration, retinal vascular occlusion, and ocular inflammation. It is also useful in preoperative assessment for retinal laser procedures. After IV injection offluoresceinsolution, the retinal, choroidal, optic disk, or iris vasculature is photographed in rapid sequence. angiography. It is used to image exudative or wet Age-Related Macular Degeneration (AMD or ARMD) . Optical coherence tomography (OCT) provides high-resolution images of posterior eye structures, such as the retina (including retinal pigment epithelium), choroid, posterior vitreous, and optic nerve. Retinal edema can be identified. OCT works in a manner similar to that of ultrasonography but uses light instead of sound; it does not involve contrast use or ionizing radiation and is noninvasive. OCT is useful in imaging retinal disorders that cause macular edema or fibrous proliferation over or underneath the macula, including age-related macular degeneration, Diabetic Retinopathy , macular holes, and Electrodes are placed on each cornea and on the surrounding skin, and electrical activity in the retina is recorded. This technique evaluates retinal function in patients with retinal degeneration. It does not evaluate vision. B-mode ultrasonography provides 2-dimensional structural information even in the presence of opacities of the cornea and lens that can interfere with direct examination (eg, with ophthalmoscopy). Examples of ophthalmologic applications include assessment of Cancers Affecting the Retina , A-mode ultrasonography is 1-dimensional ultrasonography used to determine the axial length of the eye, a measurement needed to calculate the power of an intraocular lens for implantation as a part of Cataract extraction and lens implant procedures . Ultrasonic pachymetry is use of ultrasonography to measure the thickness of the cornea before Refractive Surgery (eg, laser in situ keratomileusis [LASIK]) and in patients with corneal dystrophies. These imaging techniques most often are used for evaluation of ocular trauma, particularly if an intraocular foreign body is suspected, and in the evaluation of orbital tumors, optic neuritis, and optic nerve tumors. MRI should not be done when there is suspicion of a metallic intraocular foreign body. 