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Intrastromal corneal rings were approved in 2004 by the Food and Drug Administration for people with keratoconus who cannot adequately correct their vision with glasses or contact lenses, and for whom corneal transplant is the only other option. [5]
Kayser–Fleischer rings (KF rings) are dark rings that appear to encircle the cornea of the eye. They are due to copper deposition in the Descemet's membrane as a result of particular liver diseases. [1] They are named after German ophthalmologists Bernhard Kayser and Bruno Fleischer who first described them in 1902 and 1903.
Fleischer rings are pigmented rings in the peripheral cornea, resulting from iron deposition [2] in basal epithelial cells, in the form of hemosiderin. [3] They are usually yellowish to dark-brown, and may be complete or broken. [4] The rings are best seen using the slit lamp under cobalt blue filter. [4] They are named for Bruno Fleischer. [5]
Small variable-frequency drive Chassis of above VFD (cover removed). A variable-frequency drive (VFD, or adjustable-frequency drive, adjustable-speed drive, variable-speed drive, AC drive, micro drive, inverter drive, variable voltage variable frequency drive, or drive) is a type of AC motor drive (system incorporating a motor) that controls speed and torque by varying the frequency of the ...
With a variable-speed drive on the pump or fan, the supply can be adjusted to match demand and no extra loss is introduced. For example, when a fan is driven directly by a fixed-speed motor, the airflow is designed for the maximum demand of the system, and so will usually be higher than it needs to be.
The Landolt C, also known as a Landolt ring, Landolt broken ring, or Japanese vision test, is an optotype: a standardized symbol used for testing vision. It was developed by the Swiss-born ophthalmologist Edmund Landolt. The Landolt C consists of a ring that has a gap, thus looking similar to the letter C.
The sneezing, coughing and runny nose are enough to drive anyone crazy. But having a blocked nose, whether it's from an illness or just plain ol' seasonal allergies is perhaps the worst symptom of ...
The chart contains rows of the letter "E" in various kinds of rotation. The patient is asked to state (usually by pointing) where the limbs of the E are pointing, "up, down, left or right." Depending on how far the patient can "read", his or her visual acuity is quantified. It works on the same principle as Snellen's distant vision chart.