Ординатура / Офтальмология / Английские материалы / Quick Reference Dictionary of Eyecare Terminology 4th edition_Ledford, Hoffman_2005

348 Appendix 14

A P P E N D I X 15

Normal Values of

Common Blood Tests

1.Complete blood count (CBC)—Checks the number of red blood cells, white blood cells, and platelets present in a blood sample. Normal values are:

White blood cell count: 4300 to 10,800/cu mm Platelet count: 150,000 to 350,000/cu mm Red cell count:

Male: 4.6 to 6.2 million/cu mm Female: 4.2 to 5.4 million/cu mm

Hemoglobin:

Male: 14 to 17 g/dL Female: 12 to 15 g/dL

Hematocrit:

Male: 41% to 50% Female: 36% to 44%

2.Prothrombin time—Evaluates the ability of the blood to clot. A normal value is between 9 and 18 seconds.

3.Blood glucose level—Used to detect the presence of diabetes and to monitor its treatment. Normal fasting blood glucose level is 60 to 100 mg/dL.

4.Rheumatoid factor—A test for rheumatoid arthritis. If the patient does not have rheumatoid arthritis, the test will usually be negative.

5.Erythrocyte sedimentation rate—Indicates the presence and intensity of an inflammatory process such as arthritis or cancer. It is not specific for any one disease. Normal values (Westergren) are:

350 Appendix 15

Male: 0 to 13 mm/hour

Female: 0 to 20 mm/hour

6.Creatinine and blood urea nitrogen (BUN)—Both creatinine and BUN are tests of kidney function. Normal values are:

Creatinine: 0.8 to 1.2 mg/dL BUN: 8 to 25 mg/dL

7.Potassium—3.3 to 4.9 mmol/L

8.Sodium—135 to 145 mmol/L

9.Calcium—8.9 to 10.3 mg/dL

Note: Some normals vary slightly according to the patient’s age, the laboratory, and the test manufacturer.

Reprinted with permission from Bittinger M. General Medical Knowledge for Eyecare Paraprofessionals. Thorofare, NJ: SLACK Incorporated; 1999.

A P P E N D I X 16

The Metric System

The metric system is a system for measuring length, weight, and volume. It is used in most English-speaking countries, although its acceptance in the United States has been slow.

The beauty of the metric system lies in the fact that it is based on multiples of 10. In addition, the same prefixes indicating fractions of units can be applied to all three types of measurements.

The base metric unit for length is the meter. The gram is the base for weight, and the liter for volume. Metric Fraction Prefixes (p. 352) shows the prefixes that are most useful in the eyecare field. These prefixes can be combined to any of the base units. For example, the terms kilometer, kilogram, and kiloliter all refer to 103 of their respective units (ie, 1000 m, gm, or l).

The metric system is widely used in the scientific community, including the eyecare field. Because of this, most of the formulas used in optics are written to use metric units. If your measurements are taken in nonmetric units (eg, inches, pounds, or fluid ounces), you will need to be able to convert them to metric units in order to work the formula. Common conversions are shown in Appendix 17.

It is also important to note that while measurements may be given in the metric system, the formula may call for a different fraction unit. For example, the formula for focal length is D = 1 ÷ F where D is the power of the lens in diopters and F is the focal length in meters. However, you may be given the focal length in centimeters. It is important to know the formula and to read the question

352 Appendix 16

carefully in order to be sure that you are working with the correct units. If not, it is easy to go from one unit to the other by moving the decimal point accordingly.

At times, it may also be necessary to be able to convert visual acuity measurements from those based on 20 feet to those based on the metric system (6 m is standard). Visual Acuity Equivalents (p. 353) gives these conversions.

METRIC FRACTION PREFIXES

Base units: meter (length), liter (liquid measurement), square meters (square measurement), gram (weight), and cubic meters (cubic measure).

Reprinted with permission from Lens A. Optics, Retinoscopy, and Refractometry. Thorofare, NJ: SLACK Incorporated; 1999: 72-73.