Patient complaints usually treated with artificial tears, therapeutic
medications and pain relievers may be resolved with the proper eye wear.
Headache, dry eye and eye strain are common complaints among eye care
patients. One clinician has achieved a high degree of success by treating these
patients with base-in prism.
“Our proprioceptive system, known as our ‘sixth sense,’
provides subconscious feedback to our visual system regarding where an object
(e.g., words in a book or images on a computer screen) is in space,”
Jeffrey P. Krall, OD, co-owner of Krall Eye Clinic in Mitchell, S.D., told
Primary Care Optometry News in an interview. “However, our
eyes do not mediate conscious eye position. When our eyes have misjudged the
distance of an object from us, cortical supervision is required to adjust this
retinal disparity. Without correction, many people will develop headaches and
Conventional wisdom says that symptomatic convergence insufficiency is
caused largely by decreased near point of convergence associated with increased
exophoric deviation between the two eyes. For example, a person with 10 D of
exophoria at near should have more pronounced symptoms of headache, dry eye
sensation or eye strain than a person with 5 D of exophoria.
Jeffrey P. Krall
But Dr. Krall believes that the amount of deviation has little
meaningful correlation to symptoms.
“If you take a patient that is 1 D exophoric at near, and take
another patient that is 10 D exophoric at near, either patient could be
symptomatic,” Dr. Krall said. “It has very little to do with the
magnitude of the deviation, because that is not the mechanism causing the
problem. The ocular muscles are more than capable of converging.”
Extensive research by Dr. Krall revealed that patients who were
monocular were basically asymptomatic.
“It is truly a binocular problem, not a monocular problem,” he
said. “The eyes are focused in one location but converged to another. By
altering this correctly, though, there is a high likelihood that symptoms will
Patients with proprioceptive symptoms will describe headaches that start
at the front of their head and often migrate to the occipital region, but they
do not occur upon waking, Dr. Krall said. Two other symptoms are photophobia
and sleepiness after reading for a short period.
The best way to diagnose a patient with proprioception disparity is
based on symptoms, according to Dr. Krall. “If patients are asymptomatic,
they do not have a problem,” he said.
Devices such as the Titmus Optical Vision Screener (Honeywell, Morris
Twp., N.J.) and the Optec Vision Tester (Stereo Optical Co., Chicago) provide
“the gross phoria between the two eyes, but that is not the problem,”
Dr. Krall said. “However, generally, the greater the exophoria, the more
likely the patient will be symptomatic.”
Opt-Align (Stereo Optical Co.) is a new diagnostic instrument that can
effectively measure proprioceptive disparity. “Opt-Align addresses the
relationship between peripheral and central vision and the disparity between
where the eyes are perceived to be converged and where the object is located.
It does this by permitting peripheral binocularity while our central vision is
monocular,” Dr. Krall said. “Ultimately, you need to test patients
both centrally and peripherally to measure proprioceptive disparity, which
Opt-Align has some similarity with the Turville infinity binocular
balance test, Dr. Krall said.
“Under the right conditions in a 20-foot room, you can probably get
similar results with the Turville,” he said.
Treatment for proprioceptive symptoms
Therapy for proprioceptive disparity consists of changing eye alignment
with prism. For a patient who is nonpresbyopic, “single-vision lenses will
resolve the problem,” Dr. Krall said. “However, you have to place the
correct amount of prism in their lenses in order to align their convergence
point to where they are focused. This is the key.”
By measuring and correcting proprioceptive disparity in tandem with the
patient’s nearsightedness or farsightedness, “symptoms
disappear,” Dr. Krall said.
Several new progressive lenses are available. Signet Armorlite (San
Marcos, Calif.) offers Kodak lenses with Anti-Fatigue Progressive
“Shamir Insight [San Diego, Calif.] took their Autograph II and
added base-in prism to the reading area and called it Autograph II
Relieve,” Dr. Krall said. “They did the same with the Relax lens and
called it Relax with Relieve. Relieve is exclusively distributed through Walman
Dr. Krall has been treating symptomatic patients for 15 years and
estimates a nearly 85% success rate.
“There are so many people with this problem. It is amazing,”
he said. “We are changing the visual system so the eyes converge to the
same location where they are focused.”
Dr. Krall is co-author of a study that appeared in Optometry &
Vision Science in 2009 that assessed the effectiveness of base-in prism
for adult presbyopes with convergence insufficiency.
All 29 subjects filled out the Convergence Insufficiency Symptom Survey
V-15 (CISS) and scored at least 16 points. They were then given two pairs of
Kodak progressive-addition glasses in a randomized sequence: one with a base-in
prism, the other placebo (the same lens prescription but no prism). Each pair
of glasses was worn for 3 weeks consecutively, and at the end of both 3-week
cycles the subjects again completed the CISS.
The mean (standard deviation) CISS score decreased from 30.21 at
baseline to 13.38 for the base-in prism glasses, compared to a reduction to
only 23.62 with the placebo glasses.
Another practitioner’s experience
“Some patients we’ve treated with therapeutics and artificial
tears see no resolution to their symptoms,” Paul M. Karpecki, OD, FAAO,
director of corneal services and research at Koffler Vision Group in Lexington,
Ky., and a PCON Editorial Board member, said in an interview.
Paul M. Karpecki
Eye alignment “has an incredible place, both from what we
understand and know in optometry, as well as being a differential diagnosis for
patients who have been suffering for years, without anyone quite finding the
reason for it,” he said.
Dr. Karpecki employs Opt-Align to diagnose these problems.
“Instead of taking 5 to 10 minutes to measure eye alignment and
phorias on a phoropter, Opt-Align takes only about 60 seconds and gives you the
exact numbers for correcting with prism and spectacles,” he said.
Since acquiring Opt-Align last summer, Dr. Karpecki used the device on
more than 100 patients in 2011.
“It is amazing how many patients suffer from headaches caused by
eye strain but they have been told they are migraines or neurological,”
Dr. Karpecki said. “But these symptoms completely resolve with the
appropriate correction and diagnosis of the proprioceptive disparity.”
Within days of eyeglass wear, “most patients notice a decrease in
frequency, if not complete resolution, of their symptoms,” he said.
Glasses are worn indefinitely.
Vance M. Thompson, MD, FACS, director of refractive surgery at Vance
Thompson Vision in Sioux Falls, S.D., said some of his patients complain of dry
eye and eye strain after refractive or cataract surgery.
Vance M. Thompson
“It was frustrating doing maximum dry eye therapy with plugs,
lubricants and eyelid treatment without patients improving,” Dr. Thompson
After being fitted with the proper glasses, his patients with
proprioceptive disparity have greatly improved.
“It just blew me away how the small amount of prism in the glasses
brought patients such relief,” Dr. Thompson said. He has been referring
patients with this condition to optometrists, including Dr. Krall, for the past
“We’ve worked really hard on improving the clarity of vision.
But there has been this missing component of the comfort of vision,” Dr.
Krall said. “The future of eye care will address both issues.”–
by Bob Kronemyer
- Teitelbaum B, Pang Y, Krall J. Effectiveness of base-in prism for
presbyopes with convergence insufficiency. Optom Vis Sci.
- Paul M. Karpecki, OD, FAAO, can be reached at Koffler Vision Group,
Eagle Creek Medical Plaza, 120 N. Eagle Creek Dr., Suite 431, Lexington, KY
40509; (859) 263-4631; email@example.com.
- Jeffrey P. Krall, OD, can be reached at Krall Eye Clinic, 1415 N.
Sanborn Blvd., Mitchell, SD 57301; (605) 996-2020;
- Vance M. Thompson, MD, FACS, can be reached at Vance Thompson
Vision, The Talley Building, 1310 W. 22nd St., Sioux Falls, SD 57105; (605)
- Disclosures: Dr. Karpecki has no relevant financial disclosures.
Dr. Krall is a paid consultant to Signet Amorlite Inc., Stereo Optical Company,
Dakota Laboratories LLC, Shamir Optical Industry Ltd. and Bausch + Lomb. Dr.
Thompson has no relevant financial disclosures.