Patient Care

Pachymetry

The pachymeter is an instrument that measures the thickness of the cornea.  It is useful in monitoring the progression of certain disorders that cause the cornea to become thickened (or filled with water), resulting in a loss of vision.  Pachymetry is also performed to determine whether the cornea is strong enough for procedures such as LASIK. 

This test is used to monitor the number, density, and quality of endothelial cells that line the back of the cornea.  A microscope magnifies the cells thousands of times and the image is captured with a camera or video camera.  The number of cells within one square millimeter are counted and recorded.  The endothelium of a young, ten-year-old, healthy cornea has approximately 3,500 cells in each square millimeter.  Normal aging causes the cells to gradually decrease over time.  By age 60, most people have approximately 2,500 cells per square millimeter.

Field of vision describes the side vision when one is looking straight ahead. The testing of the extent of the side vision is important in the diagnosis and follow up of several disease including glaucoma, and diseases relating the eye with the brain (neuroopththalmology). The test is usually done on computerized machines (Humphrey field analyzer). The machine is programmed to test several points, sometimes repeatedly with varying illumination. The test may take time depending upon the defect in a given patient. The computer has inbuilt software that enables comparison of the field charting on repeat testing of the same patient.