Trial frames are indispensable devices and at least one spare should be available. A very light-weight, simple type can be useful for children. Any frame is constant use needs to be robust and have several useful adjustments, such as angling and depression for near vision, with space for at least three lenses for each eye.

Trial lens is a series of cylindrical and spherical lens's used in testing vision. Spectacles are prescribed for a patient after vision has been tested using trial lenses placed in a special empty spectacle frame worn by the patient. It is available in extensive sets so that in combination any power from -20 D to +20 D in steps of 0.25 D or less can be obtained.

Triangle needle holder is designed to stay at the end of thick knitting needles. The triangle form of the stopper prevents the needle from rolling over. It helps to keep stitches from slipping off the needle.

Tricyclic antidepressants are a type of antidepressant that can relieve the symptoms of depression, such as sadness and irritability. It inhibits the reabsorption (reuptake) of serotonin and norepinephrine. To a lesser extent, TCAs also inhibit reabsorption of dopamine. These antidepressants also block certain cell receptors, which accounts for many of their side effects. These are called tricyclic because of their chemical structure.

Triglyceride is a type of fat. Human body makes some triglyceride. Triglyceride also comes from the food. A blood test can be done to measure the amount of triglyceride in the blood. This is called a triglyceride level. This test is often done to determine patient's risk of developing heart disease. A high triglyceride level may lead to atherosclerosis, which increases patient's risk of heart attack and stroke.

Triple arthrodesis consists of the surgical fusion of the talocalcaneal, talonavicular, and calcaneocuboid joints in the foot. The primary goals of a triple arthrodesis are to relieve pain from arthritic, deformed, or unstable joints. Other important objectives are the correction of deformity and creation of a stable, balanced plantigrade foot.

Triple lumen catheter is a flexible polyurethane catheter. It is suitable for use in treatment of humans by inserting the catheter into a blood vessel over a Seldinger guidewire, and using the catheter to extract blood at a selected location in the blood vessel and to return treated blood downstream of the location after treatment. The catheter includes an elongate body and a tip at the distal end of the body. The body has an outer wall and an integral internal septum combining with the outer wall to define a pair of similar C-shaped lumens extending longitudinally in the body.