The monocular direct and the binocular indirect are both types of ophthalmoscopes. The monocular direct is hand-held and used to examine the back of the eye. The view through the monocular direct is slightly magnified. This tool is also used to "detect changes in the clarity or obstructions in the normally transparent ocular media," according to Eye Care Contacts. The binocular indirect is either worn by the optician or the patient and used in combination with a condensing lens, which is placed in front of the eye. Drops that dilate the pupils of the patient's eyes are used to allow the optician a 3-D view of the back of his eye. The view through the binocular indirect is smaller, yet wider, than through the monocular direct. This type of ophthalmoscope can detect elevated lesions that the monocular direct may miss.
Visual Fields Tester
Visual field loss may be a symptom of glaucoma, tears in the retina, artery and vein occlusions and optic nerve tumors. A visual field tester is used by an optician to test a patient's visual field for signs of loss. The visual field tester shows the patient an oscillating bar pattern or point of light in different locations on a screen. The patient then indicates that he can see the pattern by clicking a mouse button.
Tonometers are used by the opticians to measure pressure in the eye. Some tonometers require the use of dye and anesthetic. Eye pressure measurements are used to help the opticians diagnose glaucoma, although eye pressure measurements alone are not enough to diagnose glaucoma.
The retinoscope works by shooting light to the back of the eye as the optician "dials in the lens power required to focus that light source correctly on the retina," according to Bickford. This helps the optician to determine the proper lens prescription for patients.
Lenses and prisms are used in different combinations on a refractor to create almost all possible optical corrections. The optician starts with the information from the retinoscope and then uses the refractor to fine tune a patient's lens prescription. As the lenses are changed, the optician will ask the patient to tell her what combination she is able to see with. This tool can also be used to help the optician examine differences between the patient's eyes.