Troubleshooting optical complaints

December 11, 2013

There is no doubt that optical errors adversely affect patient satisfaction and practice success. Sometimes it can be confusing whether a visual problem is due to an optical error or if a patient needs to see the doctor for a refraction re-check. The reality is, while we often send a patient back to the doctor, the error is usually optically related. Even worse, doctors may feel pressure to tweak the prescription to please the patient, when they actually had the best prescription to begin with.

The best way for technicians and opticians to differentiate whether the patient actually needs to see the doctor for a re-check is to go through an optical checklist.

Related: The case of the blurred disc margins

An optical checklist

For starters, does the work order match the doctor’s prescription? We are used to retaining the patient’s prescription and attaching it to the back of our job ticket or work order. Then, when the job comes back from the lab for verification/dispensing, it is all too easy to look at the written Rx on our job ticket for verification of accuracy.

We don’t retain the patients’ Rx to keep them in our office and to keep them from going somewhere else-we keep it so that we can check the accuracy based on the doctor’s written instructions. When we verify the accuracy of the prescription based on our job ticket, we will not know if there was an error in transcription, and the job could slip through to the patient.

When troubleshooting an optical problem, consider whether the prescription was modified for vortex distance or slab-off prism; whether it should have been modified for vertex or slab off; and whether the glasses were made correctly.

When troubleshooting, examine:

• Sphere, cylinder, and axis

• Add power

• Prism

• OC placement (both vertically and horizontally)

• Base curves

• Tints, coatings, and filters

• Waves or warpage

• Vertical imbalance

• Unwanted prism

• Power at 90 degrees (to check for vertical imbalance problems)

• Power at 180 degrees (to check for unwanted prism induced due to a decentration error)

• High tech lens material (different Abbe value?)

• Asphericity (requiring a flatter base curve?)

• Buyer’s remorse?

If the patient states that he or she has blurred distance vision, blurred near vision, or blurred peripheral vision, what should you do?

Related: How to recognize and manage digital eye strain

Handling blurry vision

One of our major challenges is discerning the optical cause of a problem, when our patients say that they “can’t see.” It is up to us to know the difference between a genuine optical problem and a problem of adaptation. For example, when a patient says that she can’t see, we need to ask more questions and dig a little deeper.

One way to do this is to ask the patient, “Do you mean it is blurry as in ‘blurry’, or blurry, as in ‘clear, but wavy, distorted, the floor feels like an ocean, etc.?” Asking for clarification helps you to better discern the cause of the problem.

If a patient responds that it is definitely blurry, the next thing I would do is a configuration test. The way the lenses are configured (positioned) in front of the eyes can make all of the difference in the world.

Ask the patient to move the eyewear up and down, in and out, and with more/less tilt. Years ago, this is how we dispensed cataract glasses years ago-the patient would move the eyewear around in front of his eyes until the vision improved, and we would adjust the glasses exactly as the patient had them positioned. 

When in doubt, there are three magic adjustments that will help alleviate peripheral distortion:

• Decrease vertex distance

• Increase pantoscopic tilt

• Increase face form/wrap

Related: Scleral lens aids in visual rehabilitation 

Imagine that the distortion (aberration) is like the right and left sides of a window sill. By bringing the distortion/aberration closer (decreased vertex distance), tilting it downward (increased panto), and wrapping it (increased face wrap), the blurred area will be placed outside the patient’s field of view.

The distortion/aberration still exists (like in a PAL, for example), but it disappears in the patient’s perspective. It is my opinion that most people are walking around with eyewear that needs more tilt and wrap. This simple adjustment technique will solve many optical complaints.

Another example: Let’s say that a progressive lens wearer comes in complaining that, while her vision is good at the intermediate and distance, she has to hold reading material to the extreme left. It is clear she is not looking through the nearpoint reading area. What should you do?

Do not send the patient back for a refraction recheck. The fact that the patient said she can see clearly in the distance and intermediate is proof that the prescription is accurate. The problem is at near.

Try this tip to see exactly what is going on with a problem with near vision:

1. Take a flat mirror (about 8 inches square) and, using a Sharpie marker, make a dot in the middle of the mirror.

2. Place the mirror on the dispensing table, between you and the patient, at the patient’s near working distance.

3. Place all of the markings back on the PAL lenses, and put them back on the patient, verifying a proper adjustment.

4. Ask the patient to look at the dot in the center of the mirror, keeping her head straight, as if she were reading a book through her progressive addition lenses.

5. Stand up, look into the mirror and look at your patient looking at the dot in the mirror.

6. Determine if your patient is actually looking through the near-point circle markings (chances are, she is not).

7. Now, proceeding with caution (to avoid inking your patient’s face by mistake), carefully mark the lenses where the patient is actually looking. This will give you the subjective measurement for her nearpoint PD requirements.

8. Order the lenses from the lab with the markings on, and ask the lab to make the lenses with the near PD at the markings, and to outset the distance PD from the specified reference point. This will work with the majority of prescriptions, with the exceptions of very strong prescriptions (over ± 7.00 D), and unbalanced prescriptions (optical difference of 1.50 D or more, as in anisometriopia and antimetripia).

Related: View patients as missed opportunity, not lost cause

While this example is not mainstream, it does occur. Not everyone converges downward and inward at near the same amount. Sometimes a patient has a specific turning of the eye, like cyclodextro phoria, a condition in which the eyes do not converge downward and inward at a range within normal limits. In this case, the lenses need to be fabricated specifically for the patient’s unique reading levels.

With all of the challenges of keeping up to date with new innovations in lens and frame technologies, it is easy to forget important optical concepts that we don’t see every day. In addition to knowing how to compensate for and calculate slab-off prism, we need to know how to compensate for vertex distance in higher-powered lenses and correct base curve selection.

These optical concepts are even more important with high refractive errors/strong prescriptions that are more common than we think. Taking the extra steps to uncover and correct these optical challenges will help out a lot of patients we may have otherwise missed. It is worth the extra effort.