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Strabismus surgery (also: extraocular muscle surgery, eye muscle surgery, or eye alignment surgery) is surgery on the extraocular muscles to correct strabismus, the misalignment of the eyes. [1] Strabismus surgery is a one-day procedure that is usually performed under general anesthesia most commonly by either a neuro- or pediatric ...
In this case, the pinhole occluder compensates for the inability to contract the iris assisting the eye in obtaining a retinal projection similar to that of a non-cycloplegic eye. Squinting and looking through a tiny hole made with a finger works similarly to a pinhole occluder, by blocking light through the outer parts of the eye's lens. [4]
Using a phoropter to determine a prescription for eyeglasses. An eyeglass prescription is an order written by an eyewear prescriber, such as an optometrist, that specifies the value of all parameters the prescriber has deemed necessary to construct and/or dispense corrective lenses appropriate for a patient.
As the eye shifts its gaze from looking through the optical center of the corrective lens, the lens-induced astigmatism value increases. In a spherical lens, especially one with a strong correction whose base curve is not in the best spherical form, such increases can significantly impact the clarity of vision in the periphery.
An example of the Landolt C eye chart (also known as the Japanese eye chart.). Numerous types of eye charts exist and are used in various situations. For example, the Snellen chart is designed for use at 6 meters or 20 feet, and is thus appropriate for testing distance vision, while the ETDRS chart is designed for use at 4 meters. [16]
Many colour correction filters are identified by a code of the form CC aa b, for example, CC50Y: [6]: 38–39, 49 CC = type (for colour correction) aa = strength or density of the filter (50 = 50%) b = color (in this case, Y for yellow) While the same information may be present, the specific sequence of colour and density may vary by manufacturer.
A lens used with an adapter for close-up focusing, for example, may not be able to focus to infinity. Failure of the human eye to achieve infinity focus is diagnosed as myopia. All optics are subject to manufacturing tolerances; even with perfect manufacture, optical trains experience thermal expansion. Focus mechanisms must accommodate part ...
Typical Snellen chart to estimate visual acuity. Herman Snellen (Dutch pronunciation: [ˈɦɛr.mɑn ˈsnɛ.lə(n)], February 19, 1834 – January 18, 1908) was a Dutch ophthalmologist who introduced the Snellen chart to study visual acuity (1862).