A hypodermic needle is a hollow needle commonly used with a syringe to inject substances into the body. This may also be used to take liquid samples from the body, for example taking blood from a vein in venipuncture. It is normally made from a stainless steel tube drawn through progressively smaller dies to make the needle. The end is beveled to create a sharp pointed tip. This lets the needle easily penetrate the skin.

Hypodermic syringe is a syringe with a calibrated barrel, plunger, and tip. It used with a hypodermic needle for hypodermic injections and for aspiration. When the plunger handle is pulled back, fluids are drawn into the tube. The fluid is forced out through the needle when the handle is pushed down. There are many hypodermic syringe designs available. However, all of them have the same general features, including a barrel, plunger, needle, and cap. The barrel is the part of the hypodermic needle that contains the material that is injected or withdrawn. A movable plunger is contained within this tube. The width of the barrel is variable.

Hand-held magnifiers are convex (plus) lenses that increase the size of a retinal image and bring the image into focus. It provides maximum magnification when positioned at its focal distance with respect to the material to be recognized. The focal distance in centimeters is determined by dividing the dioptric power of the aid into 100. Most hand-held magnifiers are portable; therefore, these are convenient for shopper, students, and technicians who need an aid for spotting rather than for the continuous reading of textual matter.

Halloween lenses are soft contact lenses with a layer of color embedded in them. It is available in many different designs. Most Halloween lenses are completely opaque, to hide the real eye color, with a clear center.

Hard contact lens storage solution offers allergy free ease of patient compliance in the domain of cleaning, disinfecting, storage, wetting, rewetting, and in-the-eye lubrication for all rigid contact lenses of any polymeric structure.

Hematology analyzer is a device used to measure WBC, RBC, Hgb, Hct, MVC, Plt, L%, and L#. Usually it is based on the principle that different blood cells have different densities. Therefore, when blood is spun in a microhematocrit tube, the cells separate into three distinct layers: the red blood cells (which have the greatest density), the buffy coat and the plasma. A molded cylindrical float inserted into a precision-bore capillary tube expands the buffy coat. The specific gravity of the float is approximately midway between that of the plasma and the red cells, causing the buffy coat to expand along the length of the float. Expanded layers of packed white cells and platelets resolve between the float and the inner wall of the tube.

Hemoglobin testing system consists of a reflectance meter and proprietary hemoglobin test cards that measures hemoglobin on a single drop of blood in seconds. It is used to measure the level of hemoglobin in the blood. It is portable and easy to use and usually provides a test result in 30 seconds or less.

HDL cholesterol stands for high-density lipoprotein. It is a form of good cholesterol. Lipoproteins are proteins in the blood that move cholesterol, triglycerides, and other lipids to various tissues. HDL test is done to check the level of cholesterol in the blood and to see if patients are at high risk of a heart attack, stroke, or other cardiovascular problem. The main function of HDL is to help soak up excess cholesterol from the walls of blood vessels and carry it to the liver, where it breaks down and is removed from the body in the bile.

Hydroxyapatite is chemically similar to the mineral component of bones and hard tissues in mammals. It supports bone in growth and osseointegration when used in orthopaedic, dental and maxillofacial applications. It is a thermally unstable compound, decomposing at temperature from about 800-1200°C depending on its stoichiometry. It has the ability to integrate in bone structures and supports bone in growth, without breaking down or dissolving.

Hand-held keratoscopes are designed to project a bright circular ring on the cornea having a circular glass ring attached to a handle by a retainer ring with the circular glass ring. It provides qualitative topographic information.

Hydrolic keratome is a corneal cutting device intended for use in the LASIK procedure. It cuts tissue without deforming it that results no tearing or rough edges. It does not generate wound debris. Its smoother cuts promote quicker and more complete healing.