Training 101-2 Checking Vision Tonometry
Checking Vision The classic example of an eye chart is the Snellen eye chart, in general they show 11 rows of capital letters. The top row contains one letter (usually the "big E," but other letters can be used). The other rows contain letters that are progressively smaller. Tumbling E" Eye Chart-The tumbling E chart has the same scale as a standard Snellen eye chart, but all characters on the chart are a capital letter "E," in different spatial orientations (rotated in increments of 90 degrees).
Checking Vision Near Visual Acuity: The Jaeger Eye Chart-The Jaeger chart consists of short blocks of text in various type sizes. While holding the chart approximately 14 inches away determined your near visual acuity. The type scale on a modern Jaeger eye chart usually ranges from J10 to J1+. The J1+ paragraph on a Jaeger card typically is considered the near vision equivalent of 20/20 visual acuity on a distance eye chart, J7 and J10 on a Jaeger eye chart, which are the equivalent of 20/70 and 20/100 on a distance eye chart.
Checking Vision Make sure room illumination is dim with an evenly and adequately illuminated chart. Measure with correction OD, OS, then OU (make sure eye not being tested is completely covered) Use the + (plus) or (minus) for letters gained or missed. The patient gets credit for a line as long as they read at least ½ the letters correctly. ie DAO6 is they get 2 of the 4 letters you would record 20/60-2
Checking Vision What if they cannot see the chart? Count Fingers-Notate how far the patient can count fingers in feet/inches ie. CF @2 ft Wave your hand in front of the patient and move it in closer until they are first able to detect motion ie. HM@face Check for light projection. Hold a light source (e.g. transilluminator) in various areas of the visual field to see if the patient can determine the direction of the light source. Check to see if they can determine if the light is on or off. If it is successful then it is Light Perception. If not, then record as No Light Perception. ie. LP vs NLP
Tonometry-is the procedure to determine the intraocular pressure (IOP), the fluid pressure inside the eye. Most tonometers are calibrated to measure pressure in millimeters of mercury (mmhg). Applanation tonometry- the intraocular pressure (IOP) is inferred from the force required to flatten a constant area of the cornea Indentation tonometry-refers to the depth of corneal indentation made by a small plunger carrying a known weight.
Applanation Goldman Tonometer
Indention Schiotz Indention
The Tono-Pen involves both applanation and indentation processes. As the tonometer makes contact with the eye, the plunger gets resistance from the cornea and IOP producing a rising record of force by a strain gauge. Multiple readings are averaged.
Ocular Hypertension Causes. Elevated intraocular pressure is a concern in people with ocular hypertension because it is one of the main risk factors for glaucoma. High pressure inside the eye is caused by an imbalance in the production and drainage of fluid in the eye (aqueous humor).
Aqueous humor flows from the ciliary body into the anterior chamber, out through a spongy tissue at the front of the eye called the trabecular meshwork and into a drainage canal (dark blue region next to the trabecular meshwork).
Excessive aqueous production. The aqueous (or aqueous humor) is a clear fluid that is produced in the eye by the ciliary body, a structure located behind the iris. The aqueous flows through the pupil and fills the anterior chamber of the eye, which is the space between the iris and the cornea. Inadequate aqueous drainage. If the aqueous drains too slowly from the eye, disrupting the normal balance of production and drainage of the eye's clear fluid, this too will cause high eye pressure. Certain medications can have the side effect of causing ocular hypertension in certain individuals. Steroid medicines used to treat asthma and other conditions have been shown to increase the risk for ocular hypertension. Eye trauma. An injury to the eye can affect the balance of aqueous production and drainage from the eye, possibly leading to ocular hypertension. Other eye conditions.ocular hypertension has been associated with a number of other eye conditions, including pseudoexfoliation syndrome, pigment dispersion syndrome and corneal arcus. Also, race, age and family history play a role in your risk for ocular hypertension and glaucoma. Though anyone can develop high eye pressure, African-Americans, people over age 40, and people with a family history of ocular hypertension or glaucoma are at greater risk. People with thinner-than-normal central corneal thickness measurements also may be at greater risk of ocular hypertension and glaucoma, according to researchers.
Great Job!!! Questions?