Near visual acuity chart is used to test near visual acuity in verbal and literate children and adults. This chart tests patients ability to identify small objects.

The non-contact tonometer uses a jet of air to press against the cornea. Photoreceptors in the unit detect when the cornea is flattened a predetermined amount. The amount of time that it takes for applanation to occur is converted by the unit into millimeters of mercury. The longer it takes to applanate the eye, the higher the IOP. It also prevents the spread of contagious eye diseases. It is quite accurate within the normal range.

Nerve stimulators supply electrons to depolarise a nerve. The number of electrons supplied per stimulus equals the current. It is important to keep winding up the stimulating current to make sure that the nerve is completely depolarized, until the muscular response does not increase any more. This is called the supra-maximal stimulus. There are many types of nerve stimulators that are available such as changing resistance, constant voltage, and constant current nerve stimulators.

Nitrile Gloves are made of a synthetic polymer formed by combining the monomers acrylonitrile, butadiene and carboxylic acid. Nitrile gloves are used to avoid direct contact with the skin. These gloves are ideal for clinicians who are allergic or sensitive to latex and who perform tasks or procedures involving prolonged exposure to blood, body fluids, chemotherapeutic agents and cleaning solutions. Nitrile gloves are made from a synthetic polymer exhibiting rubber-like characteristics when vulcanized.

Nephroscopes are instruments that are inserted percutaneously through a nephrostomy tract. They are used to access calculi in calyces that is not reached by the rigid instruments and frequently deflected into most of the intrarenal collecting system.

Nebulizer is a device used to administer medication to people in forms of a liquid mist to the airways. It is used in treating cystic fibrosis, asthma and other respiratory diseases. Nebulizers are used to deliver bronchodilator medicines such as albuterol or ipratropium bromide. Nebulizers use a compressor to aerosolize liquid medication, which is delivered with a facemask or mouthpiece.

Nuclear medicine is a branch of medicine and medical imaging that uses the nuclear properties of matter in diagnosis and therapy. More specifically, nuclear medicine is a part of molecular imaging because it produces images that reflect biological processes that take place at the cellular and subcellular level. Nuclear medicine procedures use pharmaceuticals that have been labeled with radionuclides (radiopharmaceuticals). In diagnosis, radioactive substances are administered to patients and the radiation emitted is detected. The diagnostic tests involve the formation of an image using a gamma camera or positron emission tomography. Imaging may also be referred to as radionuclide imaging or nuclear scintigraphy. Other diagnostic tests use probes to acquire measurements from parts of the body, or counters for the measurement of samples taken from the patient. Nuclear medicine differs from most other imaging modalities in that the tests primarily show the physiological function of the system being investigated as opposed to traditional anatomical imaging such as CT or MRI. In some centers, the nuclear medicine images can be superimposed, using software or hybrid cameras, on images from modalities such as CT or MRI to highlight which part of the body the radiopharmaceutical is concentrated in. The diagnostic tests are usually provided by a dedicated department within a hospital and may include facilities for the preparation of radiopharmaceuticals.

Neonatal Device is a medical device for draining fluid which includes a shell made of a flexible, resilient material. The shell has an aerofoil-like shape with opposed ends and an anterior cavity and a posterior cavity separated by a partition wall. An inlet tube has a first end in communication with the fluid and a second end in communication with anterior cavity and an outlet tube has a first end in communication the posterior cavity and a second end from which the fluid is drained. A one-way directional flow valve is housed within the posterior cavity and it has an inlet end connected to the partition wall which is in communication with the anterior cavity and an outlet end in communication with the posterior cavity.

A Vitamin is an organic compound required as a nutrient in tiny amounts by an organism. A compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on the circumstances and the particular organism.Vitamins are classified by their biological activity, not their structure. Thus, each 'vitamin' actually refers to a number of vitamer compounds, which form a set of distinct chemical compounds that show the biological activity of a particular vitamin. Vitamers are often inter-convertible in the body. The term vitamin does not include other essential nutrients such as dietary minerals, essential fatty acids, or essential amino acids, nor does it encompass the large number of other nutrients that promote health but are otherwise required less often. Vitamins have diverse biochemical functions, including function as hormones (e.g. vitamin D), antioxidants (e.g. vitamin E), and mediators of cell signaling and regulators of cell and tissue growth and differentiation (e.g. vitamin A). The largest number of vitamins (e.g. B complex vitamins) function as precursors for enzyme cofactor bio-molecules (coenzymes), that help act as catalysts and substrates in metabolism. When acting as part of a catalyst, vitamins are bound to enzymes and are called prosthetic groups. Biotin is part of enzymes involved in making fatty acids. Vitamins also act as coenzymes to carry chemical groups between enzymes. Folic acid carries various forms of carbon group - methyl, formyl and methylene - in the cell.