Common Errors in the Refractive Process

The good news: They are easily avoided.

BY SUSAN K. CORWIN, C.O., C.O.M.T.

Common mistakes and lack of communication during the refractive process can lead to unhappy patients, dissatisfied physicians and disgruntled opticians.

When first confronted with the manual phoropter as a student many years ago, I was rather intimidated by all the dials on the instrument. Many pitfalls exist for the inexperienced technician performing refractometry and initially I fell into every one of these traps.

The good news is that these mistakes, most often made by inexperienced technicians, can easily be avoided. In this article, I will point out what I consider the most commonly made mistakes and provide ways to avoid them. I hope that by reading this article your technicians can learn from my mistakes and avoid stumbling when learning how to perform refractometry for patients. These points are applicable to both manual and computerized phoropters.

Getting Started

Error 1: Using an incorrect starting point or set-up

How to avoid:
► use the autorefractor Rx (or retinoscopy)
► use the old glasses prescription
► if you see a difference of 1 D, use the least minus and least cylinder readings: these readings may be from the glasses or the autorefractor
► dial in the correct papillary distance (PD)
► make sure that the phoropter is in the distance setting
► check the bubble on the phoropter level
► occlude (or fog) the non-refracted eye.

I like to start with either the autorefractor readings, or if the patient is seeing well with glasses, the glasses prescription. This is dialed into the phoropter, PD is set, bubble leveled and the left eye occluded. One of my fellow techs put a cute "happy face" sticker on her phoropter and covered up the carpenter's bubble. She just wanted to remind herself to smile for her patients. I wonder how accurate the axis was on her previous patients before I noticed this.

I once forgot to occlude one eye of a patient and wondered why my patient kept saying that the lenses didn't look any different, even when I changed the sphere power by a diopter. Another time, when teaching, I went into a lane and found the converging levers placed in the distance position for one eye and the near position for the other eye. Little details, but they all add up.

Error 2: Not communicating with the patient

How to avoid:
► tell the patient that you will be changing lenses
► label the lenses 1 and 2, not "this" or "that"
► silence is deadly in refraction. If the patient does not respond to any question, ask it again, more slowly and deliberately, and be sure to time the change in lens with your voice instructions
► if the patient seems to have difficulty in deciding, give the choice of "about the same" after switching the lenses a few times
► tell the patient that you will blur their vision when you drop in the Jackson cross cylinder (JCC) lens
► switch the JCC lens crisply and decisively.

Even if you think you have explained the process as clearly as possible, patients will sometimes always choose "number one" because they like that number.

You may have to change your question to the patient. If I find that the patient is not "getting" the idea of the "better one or better two," I try this method: I tell them that I am going to change the lens and all they have to do is tell me if the print on the chart gets better or worse. I use 0.5 D changes.

Error 3: Not refining in the correct sequence

How to avoid:
► "SACS" is the traditional sequence of refining a prescription: sphere, cylinder axis, cylinder power and double-check sphere.
► it is critical to perform spherical refinement first, in order to put the spherical equivalent (circle of least confusion) focus on the retina.
► it is necessary to find the correct axis before placing the amount of cylinder at that axis.
► it is necessary to have enough cylinder power to find the axis — do not try to find the axis of 0.25 D cylinder power. Increase the power and then find the axis.

I have found that there are many different ways of refining a prescription, but eight out of 10 doctors use a generic sequence. When I was first learning, I wrote down little reminders to myself on 3" by 5" cards and put them on the desk. As I did my refinement, I would flip over the card to remind myself what dial to use next. It was dark in the lane, so the patient could not see my "cheat-sheet."

Error 4: Overminusing

How to avoid:
► always try to first give a patient plus to relax the accommodation, then if the patient does not need plus, try minus to improve the acuity
► if a patient is 20/40 and you have added minus and they like the change, verify that they see more clearly before adding a lot more minus. This will help with endpoints and helps avoid over-minusing patients.

Error 5: Refining in too small an increment

How to avoid:
► always change the sphere in 0.50 D steps to begin with, to "wake up" the patient no matter what the acuity is
► if the patient is 20/20, they can see the difference in a 0.25 D sphere change. However, a patient with cataracts and acuities of 20/50 needs a 0.50 D sphere change.
► refine in 0.25 D steps if the patient has good visual acuity (20/25 or 20/20) or good mental acuity
► Do not overminus. It is the "cardinal sin" of refraction.

The patient's eye gets tired of accommodating through excess minus. Our goal is to have the patient put the glasses on, be comfortable and see clearly.

Error 6: Using the incorrect target for cylinder axis and cylinder power refinement

How to avoid:
► use a line of letters two lines larger than the best acuity found with the sphere refinement
► direct the patient's attention to a round letter when checking cylinder power. It is easier to see when the letter gets "out of round" with too much cylinder. If a patient looks at an "E" or "T," they may interpret the elongated letter as clearer because it is larger

If a patient is 20/40, I use an isolated 20/60 line of letters for the patient to look at.

The smallest line I use is a 20/40 line, even if the patient is 20/20 or better. Some automated refraction systems have a target of "dots" for the patient to look at. This is handy, because the patient does not try to read the dots.

Error 7: Using the JCC lens incorrectly or not at all.

How to avoid:
► use the JCC lens
► use the correct detent setting: the red and white dots should "straddle" the axis setting for axis refinement
► the red and white dots with the "P" should line up with the axis for the power setting
► if in plus cylinder, the operator should "follow the white dots" and if in minus cylinder, the operator should "follow the red dots."

I find that beginning technicians do not understand the JCC and therefore do not use it. What they do instead is dial cylinder in and out and ask the patient which is better, one or two, similarly to what they do with the sphere. The value of the JCC is that it keeps the focus on the patient's retina as you change both power and axis. A traditional +0.25 D JCC actually gives a whole diopter difference between the two choices, whereas technicians who dial cylinder in and out are only showing a quarter to a half of a diopter difference. Each time they do this they take the focus off the retina.

Error 8: Changing the axis too much

How to avoid:
► the axis on a low cylinder power should not be changed much
► a good rule of thumb for beginners is to change it by 15 degrees, and then try to see if the patient will go back closer to the original setting
► the axis on a high cylinder power should be changed even less.

I have seen technicians who do not use the JCC turn the axis dial completely around and ask the patient to tell them when the print on the chart comes in the clearest. Other technicians never check the axis and just keep it at the glasses setting.

Error 9: Changing the cylinder power too much

How to avoid:
► a patient may not tolerate an increased amount of cylinder but may tolerate less cylinder
► "Less is better." If the patient is indecisive, give the lesser of the two powers.

Error 10: Forgetting to keep spherical equivalent when refining cylinder power

How to avoid:
► for every 0.50 D change in cylinder power, you must change the sphere 0.25 D in the opposite direction (for example, if you are in plus cylinder convention, and you remove +0.50 D cylinder power, you must add +0.25 D sphere or, if you are in minus cylinder convention, and you remove -0.50 D cylinder power, you must add -0.25 D sphere).

Automated refraction systems are useful in that they do keep spherical equivalent as the cylinder power is changed. I find that even many experienced technicians do not know that this is the proper way to refine. In many offices, one technician trains another technician, who then teaches another technician (like the game of "telephone"). By the time the instruction gets to the third tech, the concept of spherical equivalent has been lost along the way.

If a patient wants more and more cylinder power, I am very suspicious. It does not make sense for them to like more cylinder. When the JCC is removed and they see worse than before the cylinder power was changed, I place it back to the original setting.

Error 11: Not double-checking sphere power

How to avoid:
► the duochrome (red/green chart) is a great second opinion
► you may need to add a "fog" to the test (+0.50 D sphere works well) to relax the patient's accommodation
► add minus if the patient sees letters better in the red and plus if the letters in the green are sharper
► forgetting whether to add minus or plus when using the red/green chart is a common problem.

The red/green chart works well in a dimly lit lane and I teach the technicians to think of green as a "GO" Green = go to plus, and red as a "STOP" like a stop sign, to stop and think before giving minus. Also, some techs do not know that a red/green overlay can be placed over any size letters. I have the patient look at larger letters so that they do not accommodate.

Error 12: Not verifying the new prescription vs. the old prescription for both distance and near

How to avoid:
► you need to show the patient the difference in what they are wearing compared to the new refraction
► offer the new prescription in glasses that are comfortable to the patient.

Error 13: Not taking into account the "total ADD" power

How to avoid:
► you need to adjust the ADD power if the patient's distance has changed and they like the original ADD power
► for example, if the distance prescription was +2.00 sphere, and the ADD was a +2.25, the total ADD would be +4.25 (2.00 + 2.25 = 4.25)
► if the patient has a cataract, the distance refraction may change to +1.50 sphere. If the +2.25 ADD is kept, the patient will only be looking through +3.75 total ADD. (1.50 +2.25 = 3.75) The ADD would need to be changed to a +2.75 in order to keep the same +4.25 magnification to which the patient is accustomed (1.50 + 2.75 = 4.25).

A simple way to show the difference is to have patients wear their glasses and then take the glasses off and look through the phoropter. I call the phoropter a "giant pair of glasses" and ask patients which they prefer.

On the automated refraction systems, I like the ability to show the difference of the new and habitual prescriptions at the touch of a button. It allows me to show patients the two choices without them knowing which one is the new one, so that they do not have any preconceived idea of which is which, and can give me a more honest answer.

Simplifying Refraction

We have been discussing the most common errors in the refractive process. Many other errors exist, such as mistakes in balancing and prism refinement, but those tasks are not routinely preformed by a beginning refractionist. I tell technicians who attend the Marco refraction class that if they can remember the following three "Objects of the game" they will be able to refract more accurately:

Object 1: Give patients as much plus as they will accept. This addresses the cardinal sin of over-minusing.

Object 2: Keep the axis close to the old glasses. This helps eliminate wide swings in axis for the newbie examiner.

Object 3: Less is best when giving cylinder power, whether in plus or minus cylinder convention. The student is taught to give the lesser of the two cylinder powers if the patient is indecisive.

One final note: We as technicians perform refractometry, the data-gathering portion of the exam. The doctor does refraction: the decision-making process by which the patient is given the best-corrected comfortable binocular vision possible.

With the advent of computerized refraction systems, automated retinoscopy (autorefractor) and preprogrammed exam sequences, doctors are able to more comfortably delegate refractometry, confident that the technician is remembering to perform all the steps in the doctor's preferred refraction sequence.

Following the relatively simple procedures outlined above will lead to satisfied patients, happier physicians, less-frazzled dispensing opticians and a healthier practice. OM

Susan K. Corwin, C.O, C.O.M.T., is director of Training and Education for Marco, based in Jacksonville, Fla. Corwin received her certificate in orthoptics and ophthalmic medical technology from Shands Teaching Hospital, Gainesville, Fla., and her B.S. in mathematics from Bucknell University.