Visual Acuity Visual acuity is tested by asking the patient to read letters of different sizes. Visual acuity is broken into two pieces a numerator, the top number, and the denominator, the bottom number. The numerator represents the test distance. The denominator is the number that represents what the patient can see. For example: 20⁄20 Means that at 20 feet the patient can see what a normal eye can see at 20 feet.

First I highly recommend that you go through this tutorial. This is the best resource I have found on refraction. After you have gone through the plus and minus cylinder refraction tutorials read the rest of this post. Refractive Errors General Eye Shapes Emmetropia: This is a normal eye “well-proportioned” Myopia: This is nearsightedness. This is an eye that can see near objects well, but can’t see distant objects well.

Keratometry is the measure of the curvature of the cornea. Corneal Curvature The cornea has the most refractive power. Even for then the lens. The average thickness of the cornea is 0.5 mm(100 um). Corneal curvature is measured in millimeters/diopter. With the rule vs against the rule. With-the-rule astigmatism means that the strongest axis is the vertical axis (90 degrees) in plus cylinder which is the same as 180 degrees minus cylinder.

Before reading this section please brush up on spectacle skills to make sure that you know how to transpose. Automated Lensometry The automated lensometer is a lensometer that does all of the work for you. Just line of the lens then the machines beeps and spits out the reading. As long as you have selected the correct cylinder type you can’t really go wrong. Advantages to using the automated lensometer

Goldmann Applanation Tonometer The word applanate means to flatten. The purpose of applanation tonometry is to find ocular pressure. This follows the formaula Pressure = Force/Area. The applanation tonometer flattens a known area (3.06mm) with a given force to give pressure. Clean The Goldmann Applanation Tonometer may be cleaned by wiping with soap and water. While cleaning don’t bend the arm of the tonometer and make sure that the readings on the tonometer head are set to zero and level when finished.

Office Antisepsis Know the difference between these three words: Disinfection – inhibition of microorganisms Sterilization – destruction of microorganisms Sanitation – clean enough to be healthy Disinfection involves the destruction and inhibition of microorganisms on any surface. Germicides disinfect non-living surfaces, such as the counter tops in the clinic. Antiseptics disinfect living surfaces, such as you hands. I had a hard time trying to remember the difference between germicides and antiseptics.

Measure This section of the test is going to test your knowledge of pupil size. Two terms to know here are miotic and mydriatic. Miotic pupils are smaller than 2mm. Mydriatic is a pupil size larger than 6mm. Memorization Trick: Miotic is small like a tick. Mydriatic is big and dramatic. Compare Anisocoria is when the pupils are unequal sizes. This may happen after a traumatic incident. Know the difference between direct pupillary response and consensual pupillary response.

Introduction to muscles and muscle movements There are six muscles of the eye. Four of them are rectus muscles, meaning that they yank the eye straight back toward the origin of the muscle. These four muscles are either medial, near the nose, lateral, near the temple, superior, above the eye, inferior, below the eye. The other two muscles are oblique muscles which means that they pull the eye at an angle causing a slight toric motion.

This was a difficult section for me to study. I feel like the best way to get through this sections is to do some hard core memorization. I have included some tables. I know that a lot of times when I see a table in a book I just skip is, but treat this table like a check list of things to know. Make sure you can identified the instruments you are required to identify and know how to clean those instruments.

Pre Test Day When you pass your JCAT you will get an email which will lead you to a website to set up a time to take your test at a Person View Testing Center. Look up the directions to the testing center and get an estimate of how much time it will take you to get to the testing center. Also take into account traffic of you are traveling during rush hour.