Making blurry vision clear

The determination of required magnification seems well defined; however, sometimes magnification devices that should be perfect don’t work for the patient. Why is that? Let’s talk about some considerations that may explain why patients’ goals aren’t met—when in theory, they should.

Visual priorities and expectations

In a clinical setting, sometimes we focus on the standard 16-inch workings distance. Our patients may have many different near demands, not only electronic vs. non-electronic, but within these categories as well. These different near demands may all have unique working distances and viewing positions; more than a patient may even realize. Understanding patients’ desired working distance, viewing position and the extent both are variable is essential. Especially when patients prioritize a specific viewing distance, I typically select initial trial devices, which allow a viewing distance as close to the preferred as possible. As you know, each device and magnification power have advantages and disadvantages; however, patients don’t always understand this. Trial devices help to Illustrate that prioritizing viewing distance may limit, for example, field of view or magnification power. Understanding this trade-off might cause the patient to modify their visual priorities or expectations. Sometimes understanding device limitations also helps to illustrate the need for multiple devices or a focusable device to meet specific visual needs.

Patients will often state they want to read a book or mail. The actual size of the desired print can be different than it is assumed to be. I suggest patients bring desired reading materials with them so print size is understood. It also is important to consider the length of time the patient wants to spend viewing the near work. Both factors are essential to determine goal near acuity. For long-term reading, I usually set a goal near acuity approximately three lines smaller than desired print size to allow for reading reserve. To describe reading reserve, think of print three lines larger than what you can just discern. The print is easy to read, like the small weight that’s easy to lift. You can lift it for a long time without an issue. That’s the size print desired for long-term reading. Choosing the appropriate goal print size will aid your patient in meeting their reading goals.

Devices

Some patients present specifically requesting a handheld device for a long-term task. They might not realize how stable the device would need to be held or stamina required to hold the device. I try to match the device not only to the patients’ goals but also to their physical status and what is practical. Having a patient read independently with the device for a period can help to guide if this device will give the patient the best prognosis to meet their goals, as well as reinforce to the patient why other options might need to be considered.

Magnification

Sometimes patients have preconceived notions about the magnification strength they require or text size to which their electronic device should be set. This can be challenging for a few reasons. The magnification power (X) that is used on devices is not always standardized. So, when a patient reports they use or want a specific magnification power, I am unclear about the specific level of magnification they are describing. I recommend patients bring in any device they are currently using so that I can assess it and determine if a change in level of magnification is recommended. Also, as we know, there is an inverse relationship between magnification and field of view. Increasing magnification/decreasing field of view may limit functionality or reading speed with the device. Similarly, I see patients who have their electronic devices set to the maximum font size. While this is appropriate for some, magnifying letters larger than needed can negatively affect usability of the device. A vision rehabilitation assessment will determine specific magnification requirements for the best outcomes.

Contrast

Patients sometimes focus on magnification to enhance vision; however, vision issues may be more related to contrast sensitivity impairment. Remember, contrast loss can significantly affect reading and be the primary cause of vision complaints. To understand contrast, I include current lighting and contrast of goal materials in the case history and assess contrast sensitivity. Task lighting, filters, high-contrast materials and lighted magnification devices may prove more effective than magnification alone in enhancing near vision.

I hope the considerations highlighted aid you in caring for your patients. The AOA has educational offerings to further address these topics. I hope you take advantage of these opportunities.

Enhance your vision rehab care, earn CE

The AOA’s member-exclusive centralized education portal, EyeLearn Professional Development Hub, offers an expanding online catalog of educational modules, webinars and resources. Check out these courses on low vision.

Para Speaker Series: Bringing Low Vision to Your Office
1 CPC credit

Bringing Low Vision to Your Practice
1 AOA CE hour

Low Vision Care 2.0
Not for credit

Written by Janis Winters, O.D., chair of the AOA’s Vision Rehabilitation Committee and associate professor of optometry, Illinois College of Optometry.

Disclaimer: The information contained in this article represents the opinion of the author and not the AOA. These are not clinical practice guidelines, nor has the evidence been peer-reviewed. There are additional aspects to this topic that may not be presented, or considered, based on the specifics of the case