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Trouble With Reading?

Understanding the Traditional Art of Reading Books

By David Lineaweaver, ABOC

Release Date: October 1, 2016

Expiration Date: June 13, 2021

Learning Objectives:

Upon completion of this program, the participant should be able to:

  1. Determine what the customer means when they say, "I can't read with these glasses."
  2. Determine environmental and ergonomic factors that affect "book" reading and optimize them.
  3. Understand the relationship between add power (magnification) and focal length.

Faculty/Editorial Board:

David Lineaweaver David Lineaweaver, ABOC, CLVT, currently works as an ophthalmology health aid and technician at the Fort Harrison MT., Veterans Administration Eye Clinic. Lineaweaver's approach to optics is practical, and that serves the low vision community especially well as a Certified Low Vision Therapist.

Credit Statement:

This course is approved for one (1) hour of CE credit by the American Board of Opticianry (ABO). General Knowledge. Course SJHI162

img1What is the trouble with reading? Most of us in the eyecare field have heard the complaint, "I can't read with these glasses." This may seem like a straightforward complaint, but it often requires some probing, open-ended questions to really determine the customer's complaint. The complaint may actually be a distance, intermediate or near complaint.

The primary focus of this course will be reading hard copy books, which usually have a viewing range of 14 to 16 inches. Many people still enjoy the experience of reading a hard copy book: In 2015, it is estimated that there were 571 million books purchased in the U.S.

There are some things that apply to hard copy book reading that don't apply to reading on electronic devices. A reader can't change font size, brightness, contrast or print and background color on a book at will, like they can on an electronic device. The option of a large print hard copy book is only sometimes available.


Before getting into any in-depth trouble-shooting, it is important to verify that:

  • 1. Rx, PD and fitting height are correct. A correct Rx is the basis and assumption that all other adjustments and recom-mendations are referenced from.
        Are the PD and fitting heights as you ordered them?
  • 2. Ensure proper fit and frame adjustment, especially for progressive lenses and higher powered prescriptions. Selecting PAL design for maximizing the
  •     reading area is the domain of another CE module (see progressive lens courses at

img2It is also very helpful if the patient's records are available for review. This is, of course, the case when the doctor's office and the optical department are connected. This helps the optician know the patient's best-corrected acuity and therefore, best manage customer expectations. For example, this can prevent an optician from trying to maximize frame adjustment and conditions to achieve 20/20 (near equivalent) vision when the best correct near vision was never better than 20/60.

Assuming that the Rx is correct and that the glasses are fitted and adjusted properly, you are ready to ask some questions:

What are you having trouble reading and at what distance?
The answers to this question will give clues to what the true complaint is. Difficulty reading road signs or seeing print on TV is a classic indication of a distance vision complaint. Difficulty viewing a computer screen or seeing gauges on a dashboard indicate that the complaint is intermediate vision. Difficulty reading print on a med-icine bottle is a "small print" complaint, which is outside the range of "book reading" complaints.

In what environment or situation are you viewing? (Well-lighted indoors setting, bright outdoor sunlight, dim room?)
Carefully listen to this description and offer recommendations as seen appropriate. For example, you may recommend specific lighting and avoiding the glare of outdoor light coming in through the window.

How often does this occur?
An answer of "all the time" likely indicates that the problem is something beyond frame adjustment, provided the viewing distance and other circumstances are correct. This may be a problem of incorrect Rx, dry eyes or something else. This probably requires a follow-up with the examining optometrist or ophthalmologist.

img3How long do you read before you have trouble reading?
If the response is a reading duration of more than 15 minutes, the near correction is most likely correct. The issue is probably changes in viewing distance due to fatigue, dry eyes or a combination of these two issues. The eyes work best when there is an ample, even tear film covering the cornea and conjunctiva, but sometimes this tear film is impaired. Oddly enough, excessive watering can be a sign of dry eyes. Dry eyes can be resolved with the use of OTC artificial tears (usually non-preserved, single vial artificial tears are recommended). Inability to consistently maintain proper viewing distance can be resolved by ergonomically maximizing physical comfort and support for reading, which will be discussed shortly.

Are you wearing single vision reading glasses or multifocals when you try to read?
This may seem obvious, but many people voice uncorrected reading complaints that would be resolved if they simply wore their reading or multifocal glasses. Along those same lines, if the customer is wearing a multifocal, ask, "What part of the lens are you looking through?" If they mention that distance seems clearer through the bifocal or trifocal segment, this is a clear indication that the Rx is incorrect, and a new refraction is needed. Sometimes, segment heights are fit very low, at the patient's request, to avoid the add interfering with distance vision or walking down stairs. This strategy works for ensuring a comfortable distance "window."

However, this puts the seg so low that it is very difficult to read. A quick check can be done if this is suspected. Have the customer manually raise the frame of their glasses and see if this makes for more comfortable reading. Often, the answer requires separate single-vision distance and single-vision near glasses, so the patient doesn't have to walk the "seg height tight rope." However, that's only if it is already established that a standard seg height creates distance viewing problems.

Do you ever feel that your upper lids ever "dim" or cut off some of your upper vision, when you read?
This is more of a clinical issue but can be briefly addressed. Upper lids move in a downward direction (down gaze) in the typical reading posture. This sometimes results in the upper lids covering a portion of the pupils, reducing the "window" of vision and causing images to be dimmer. Give the customer a reading card, while wearing near correction, and have him read through it. Note where the customer holds the card and also if upper lids droop over the pupils at all.

If drooping upper lids are "shadowing" or "dimming" near vision, ask the customer to exert extra effort to raise their brows and open their eyes wider. See if that improves vision. If so, drooping lids may be the culprit. The patient may want to consider altered posture and raised brows to compensate for this as an immediate solution. Suggest that discussing upper lid surgery, to resolve drooping, with an ophthalmologist or plastic surgeon may offer a more perma-nent solution.

Determine environmental and ergonomic factors that affect reading:
img4Maintaining proper viewing distance (focal length) is of the utmost importance for reading. To determine the optimum viewing distance, have the patient find the sharpest viewing distance and take note of it. This should also be physically comfortable. If not, the work station (desk height, chair height, and height and arm supports) should be altered ergonomically to be more comfortable. If the sharpest image cannot be maintained in a physically comfortable manner, the customer should be referred back to their doctor to discuss an add power that will provide the sharpest near acuity, at the posture that is physically comfortable to the patient. Book holders are a great hands-free aid to maintain proper viewing distance without movement. This is especially important for extended reading periods and patients with weakness or tremors (i.e., Parkinson's disease).

Print contrast in books is not typically something that can be controlled. Good "black on white" print will be much easier to see than lower contrast "black on gray" print… like the newspaper. The stock market page will give you a dose of poor contrast and small print! Glossy print magazines or print can also create glare. In addition to maintaining proper focal length, the customer will need to adjust lighting and angle that help reduce or eliminate print glare. Anti-reflective coated lenses will help with this.

It's all about lighting.
Lighting is also critical to effective reading. The field of lighting is vast and can be an exhaustive study in and of itself. We will hit some highlights that are of importance to reading.

Sometimes general room lighting is sufficient for effective reading and if so, prob-lem solved. However, sometimes more is needed. Task lighting can be very effective, as it is much closer to the task (as the name implies). Task lighting can be purchased in regular retail stores; it doesn't have to be a specialty item. This can make a dramatic improvement, especially for viewing small or poor contrast print. Task lighting is often in the form of a gooseneck lamp, which has many options for adjustment. It is best to position the lamp behind (over the shoulder) or to the side of the reader, with the light directly on the page. The Inverse Law of Illumination states that brightness quadruples as the distance from light source (to reading material) is reduced by half (the inverse of the square of the distance).

Consider moving the lamp a little closer before opting for a higher wattage bulb. Also be sure not to install a bulb that exceeds the recommended watt-age for that lamp. Positioning the lamp in front of the reader often leads to glare; this is similar to the glare that can result from facing a window with light coming through it. Never use a bare bulb for lighting, as it is a burn hazard and usually makes reading more difficult due to the increased glare it causes. Forty to 60 watt incandescent bulbs have a long history of working well for reading, with soft white being better than clear. LED lighting is bright and energy efficient. However, LEDs often cast a blue hue on print, and there are health concerns regarding blue light radiation. There are many other types of lighting, should one want to explore these options.

img5Maintaining your "place" while reading can be challenging for some people, despite good acuity and maximizing the other variables. Tracking is the action of the eyes, in unison, smoothly moving across text. Children often learn to read using their index finger to help them track. Sometimes returning to this basic technique is enough to enable a patient to not lose their place while reading. Other times a ruler or a guide/reading tracker that frames the text to be read and blocks out the other surrounding text that isn't being read is needed will do the trick by reducing visual confusion.

Understand the relationship between add power (magnification) and focal length.

Focal length (viewing distance) has an inverse relationship with add power: It gets shorter as add power is increased. Focal length is the distance at which light rays, refracted through a lens, converge at a single point. It can be expressed in the formula F (m) = 1/D. I prefer the variation of this that uses centimeters since it works better for me to visualize results.

F (cm) = 100/D
F = focal length (cm) = 100/add power in Diopters
D = diopters of add power
For example, the focal length of a +8.00 diopter lens is, F = 100/8 or F = 12.5cm.

Quick reference: A +2.50 D add has a focal length of 40 cm (approximately 16 inches) and a +2.00 D add has a focal length of 50 cm (almost 20 inches). You can see from those two common add powers that every additional +0.25D of add power (on top of the distance Rx) shortens the focal length by 5 cm. On the other hand, the focal length is increased 5 cm for every +0.25D increment that the add is reduced. For those who like to deal with focal length in inches, simply divide the focal length in cm by 2.54 to get the focal length in inches.


img6For people who have some accommodative ability left, they can usually read com-fortably for a sustained period, using no more than half of their accommodative reserve. By the time most people are in their early 60s, they may have little to no accommodation left. This would require the "full add power" of +2.50 to read at 16 inches. Therefore, the ultimate goal is to get an add power that's strong enough to meet your reading needs, but not stronger. An add power that is stronger than needed results in a complaint from patients of an uncomfortably short viewing distance.

Sometimes increasing add power, which brings along with it a short focal length, isn't worth the discomfort of an unusually close viewing distance. A practical exam-ple is the complaint, "I can read my book, but I can't read the print on my medicine bottle." It is true that a higher add power (in the +3.00 to +4.00 range) could likely enable the patient to read the small print on a medicine bottle. However, that viewing distance would be considerably shorter than what would be comfortable for reading books.

In instances like this, the customer is better off having multifocals with an add that allows for a more comfortable near viewing distance and use a handheld magnifier, as needed. The customer can also slide their glasses down their nose to get a little more magnification (increasing vertex distance increases magnification). Don't forget the importance of extra light, properly placed, when it comes to small print.

Help customers understand the oppor-tunities and trade-offs of add power, magnification, lighting, environmental factors, posture and tasks, so that reading a book leaves only the book's world for your customers to live.