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Tips for performing manual refractions.
Q: Should I start the refraction with the previous glasses or the autorefraction?
A: Start by asking a few questions: Is this the patient’s first refraction or has a previous refraction been performed in-office? If it’s the latter, use the most recent results as your starting point. You should expect the patient’s visual acuity at the starting point to be pretty close to the smallest line seen at the last refraction. Any changes in refraction should be relatively small in order to bring the patient back to the best corrected acuity. Keep in mind that the rule of thumb is 0.25D per line, or its spherical equivalent, on the eyechart. So if the patient already reads 20/25 at the refraction starting point, the change to improve the acuity back to 20/20 should approximate 0.25D. Also remember that bringing the patient back to 20/20 acuity may be achieved by adding plus lenses, not just minus lenses. You should offer plus power before offering minus power.
If the patient has never had a refraction at your office, you can either start with the autorefraction or the patient’s current spectacle correction. I usually choose the current spectacle correction if the patient read the eyechart well upon initial visual acuity assessment with their current spectacles. If the patient read poorly, then I usually opt for starting with the autorefraction readings.
TIP: If you are going to start with an autorefraction reading, it is extremely important to encourage the patient to relax their eyes when looking at the focal target in the phoropter. You can do this by asking your patient to pretend that they are looking through the house, not at it.
Q: Lens 1, lens 2, or are they the same?
A: This question asked during the refraction is the most important question in order to quantify the amount of correction required to improve the patient’s acuity. But it is more than just switching back and forth between two lenses. It is just as important and relevant which lens you present to the patient first or second.
Relax accommodation while the patient is observing the lens choices. The plus lens should be presented first for about one second in order to do so. Then the minus lens should be presented, but the lens should not be held in front of the eye for more than one second. Doing so can cause the patient to start to accommodate.
The patient should be offered plus power before minus power. A third option should be offered only if the patient could not differentiate the clarity between the first two lenses. The correct endpoint for this line of questioning is when the most plus or least minus lens is obtained to get the best visual acuity.
What if the patient pauses when shown the two lens choices? A pause is usually an indication that the patient is uncertain which lens is clearer. Once you note that pause, you should show the patient the lens choices again and inquire if the lens choices are the same.
TIP: If the patient will not accept more plus power then offer minus power. If there is a change in lens preferred, the visual acuity should also be rechecked, having the patient read the smallest line discernable to you.
Q: The patient says the minus lens makes the letters darker and smaller. What should I do?
A: More minus lenses can be offered as long as there is an improvement in acuity. To ensure that you are not overminusing your patient, you should also ask if the lens change actually makes the letters clearer or just smaller and darker. If the patient reports that the letters just look smaller and darker, but not clearer, you should give the patient the more plus lens because the patient is accommodating. Also keep in mind when offering minus power that the more minus option should not be kept for more than one second in front of the eye. Holding the minus lens over the eye for longer can induce accommodation especially if the patient
TIP: Ask your patient to blink before attempting to read the smaller lines. As the patient stares at the eyechart, the tear film can start to break up and affect the quality of vision. If the patient states that the letters appear blurred, he or she should be asked to blink a few times then attempt the line again.
Q: When should I push plus for the add?
A: When refracting a patient for near, the paraoptometric or technician should first determine the visual needs of the patient. Does the patient want glasses for reading only? Where does the patient usually hold reading material? Up close? Far away? Does the patient want to be able to see distance, near and see the computer with a single pair of spectacles?
Most patients hold their reading material between 14 and 16 inches from their face, but you should never assume that this will always be the case. Some patients like to hold their reading material close, while others like to hold it on their lap. The patient’s reading habits should be noted when taking their history and assessing their visual acuity. The reading prescription is based on the distance measurement obtained. It is known as the additional power needed to correct the acuity at near or the “add.”
TIP: The distance at which the patient holds their reading material is directly correlated to the power needed to bring the letters into the focus. The further the patient holds the reading material, the weaker the add, and the closer the patient holds the material, the stronger the reading add. When asking the patient which lens makes the letters clearer, if the patient states that both lenses look the same, the more minus lens should be given.
Q: Do I need to do a binocular balance test?
A: The goal of this test is to balance the eyes against accommodation and should only be checked if there is equal vision in both eyes. When refracting each eye separately, the patient may have one eye that “˜eats’ up minus power. That eye will accommodate more than the other. By performing the binocular balance, the eye that is accommodating will be forced to relax. This is done by introducing plus power lenses to fog the vision. The patient is asked to observe the visual acuity quality in each eye by alternately covering each eye. The patient is then asked if the vision in one eye is better than the other or if both eyes are equally blurred. The fog should blur the patient and reduce accommodation.
TIP: If the patient states that the vision in one eye is clear, that eye is accommodating and +0.25D sphere should be added until the vision in both eyes is equally blurry. Once equal blurriness is achieved, the original plus power fog is removed.
Janet Hunter, COMT, president of Eye Source, LLC, specializes in ophthalmic technician training.