Ophthalmic Optics can have some complicated equations.  We we see patients, there are times when a contact lens for astigmatism does not perform the way we predict.  We perform a measurement of the blur called an over-refraction and mathematically combine the result with the prescription to predict the next lens power that would work.  Before this utility was developed, we would have to do the math by hand or set up lenses together and use a machine called a lensometer to predict the next lens.  X-Cyl does the math for us so a doctor can just enter the variables and click on the answer.  It became wildly popular because it was faster, more accurate and free.  We wrote the software as a fun project and to help other doctors.

We wrote another program called ImageRx.  This calculator helps doctors design lenses that are equal in magnification.  Some prescriptions can generate headaches, eyestrain and double vision if the powers before each eye vary by too much.  To minimize the difference, we can vary the design of the lens such as the power, the fitting distance, the thickness and the curvature and refractive index to achieve an equal magnification.  This involved even more difficult calculations than what X-Cyl solves.  Before ImageRx, most doctors would would rely on nomograms.  ImageRx streamlines the design process and ensures mathematical accuracy to allow the eye care professional to try differing variables to solve their design challenge.

Both software have been updated to run on 32 or 64 bit operating systems.  They have been tested to run on Windows XP, Windows Vista and Windows 7.  Both are free and can be downloaded from our practice website.

Click on the icon to download.

X-Cyl Toric Crossed Cylinder Calculator
(version 1.20)

Updated for 32 or 64 bit Windows use, New tooltips and a clear button for faster, easier use.

ImageRx Anisekonic Lens Design Calculator
(version 1.20)

Updated for 32 or 64 bit Windows use, Calculate both lenses together now for easier use.

This type of strabismus is called a left intermittent hypertropia.  There is a deviation of the left eye upward.

Most images show Lincoln’s eyes pointing straight which suggest the problem was not constant.

The image above is probably amongst the most well known of Lincoln portraits and also one which shows the problem.  His left eye is deviating upward slightly revealing more of the white part of his eye (the sclera) than in his right eye which is looking into the camera.

Another image illustrates the problem – perhaps more so.

Most other portraits of Lincoln show a head tilt to the right which could be a compensation for the relative weakness of an extraocular muscle producing the deviation.

Finally, what if one applied colorizing technology to Lincoln’s portrait?  You may come up with this result.  Coloring of an image taken by Alexander Gardner on February 5, 1865 and colorized by James Nance for the Abraham Lincoln Art Gallery.

His head tilts to his right slightly.  What impact does this image bring to you by adding color?

Correction Options for Presbyopia
Eyeglasses have been the most popular and most efficient form of correction.  Contact lens options are also available to help compensate for the natural loss of focusing ability.  A careful evaluation of your vision needs is performed to see what type of challenges you have, what distances do you need to see clearly for, whether you work at a video display terminal for long periods of time and the general environmental conditions of your work such as  lighting and or even the humidity of the workplace.  Your hobbies and leisure activities may be evaluated as well.

Bifocal Contact Lenses
Have specialized optics to create a lens which has more than a single power.  The designs include simultaneous vision and alternating vision lenses.  Bifocal lenses are limited in the availability of parameters so not every patient may be a good candidate.

Simultaneous vision lenses provide a focus on the retina for objects at near and for objects at distance at the same time as illustrated below.  Contacts are available in soft and rigid gas permeable materials. Simultaneous vision lenses have areas of the lens with differing powers.  Designs have one power for near and a different power for distance.   This can occur in two distinct areas as shown on the left, alternating zones as in the center, or it may gradually change as shown on the right.

Simultaneous vision lenses have areas of the lens with differing powers. Designs have one power for near and a different power for distance. This can occur in two distinct areas as shown on the left, alternating zones as in the center, or it may gradually change as shown on the right.

Alternating vision lenses are more like traditional bifocals with the lower portion of the lens providing the near power.  Since we tend to look down as we view things at near, the contact lens must be able to move into proper position in order to work effectively.  Currently, lenses are available in rigid gas permeable materials only. When viewing objects in the distance, the line of sight passes through the top section of the contact.  When viewing near objects the line of sight passes through the bottom section of the lens.  Alternating vision lenses may not work well for people with loose eyelids or irregular corneas.

When viewing objects in the distance, the line of sight passes through the top section of the contact. When viewing near objects the line of sight passes through the bottom section of the lens. Alternating vision lenses may not work well for people with loose eyelids or irregular corneas.

Visual Phenomena Common to Presbyopic Correction with Contact Lenses…
You may notice an occasional fuzziness surrounding an otherwise clear object.  We call this effect ghosting or halos.  One of the most common side-effects is a perceived blur of a bright object such as a headlight against a dark background.  This glare at night can be eliminated by exchanging the near contact lens for a distance contact lens or through the use of special glasses designed to be worn for specific tasks such as driving.  Bifocal contact lenses may not be optimal for nighttime use and should be worn with caution while driving in the dark.  Monovision may require the use of a supplementary glasses for specific conditions.  Prolonged near activity (computers, needlepoint, form-work), night-time driving, or continued concentrated distance viewing (piloting, truck-driving) are examples.  Eyestrain or headaches which occur at near may indicate a need for a change in the power of the prescription or the need for special eyewear.  Call the doctor at our office to see if any fine-tuning to your specific needs is required.

Monovision

In monovision your doctor designs a contact lens prescription which allows one eye to remain clear for distance viewing while the other eye remains clear for near viewing.  This prescription is determined after a careful evaluation with you in which your visual needs are assessed for the best work, leisure and driving performance with the contact lenses.  Monovision allows the use of traditional contact lens designs. Monovision places your vision under new viewing conditions for combined near and distance viewing.  If you cover one eye you will notice that it will be more clear for the distance but not for near while the opposite will be true for your other eye.  With time, your brain should automatically select which eye is to be used.  This adaptation period lasts 2 to 3 weeks for most patients.  You should be especially careful in all your daily activities (i.e., driving, using curling irons, moving pots and pans on the stove) while you get used to your prescription. Monovision offers a compromise between the best vision possible with bifocal eyeglasses and the freedom from being dependent on some pair of reading prescription.  Some patients may require glasses to work over contacts for extended or critical near or distance tasks.

Modified Bifocal / Monovision
Is a fitting technique which utilizes both bifocal contacts and monovision.  Is a method which helps to fine tune a bifocal contact lens prescription to work better at distance or near.  The lens power is modified to enhance near or distance vision according to the needs of the patient. Sometimes only one bifocal on an eye with the other eye set for distance vision may be all the vision correction which is needed.

Contact Lens Tips
Wear your contacts when you go to see the doctor for progress checks.  It is important to see the lens after several hours of wear on the eye unless discomfort is severe. Because contact lenses are medical devices, yearly eye exams are required to check the health of the eye when wearing contact lenses.  New contact lenses can not be dispensed if you are past due for a check up.

• Comprehension reduces as reading continued: loses interest too quickly
• Mispronounces similar words as continues reading
• Blinks excessively at desk tasks and/or reading; not elsewhere
• Holds book too closely: face too close to desk surface
• Avoids all possible near-centered tasks
• Complains of discomfort in tasks that demand visual interpretation
• Closes or covers one eye when reading or doing desk work
• Makes errors in copying from chalkboard to paper on desk
• Makes errors in copying from reference book to notebook
• Squints to see chalkboard, or requests to move nearer
• Rubs eyes during or after short periods of visual activity
• Fatigues easily; blinks to make chalkboard clear up after desk task

Accommodative Insufficiency

Accommodative insufficiency occurs because of the eye can not maintain clear vision at near.

Ill-Sustained Accommodation

Ill-sustained accommodation is similar to accommodative insufficiency except print may initially appear clear and easy to read without effort.  With time, the task at near begins to require more effort to focus.  Blurred vision, eyestrain and headaches can occur with sustained effort.  A simple visual acuity test at near (as what is frequently done during a vision screening) will usually not detect this problem.

Normal Focusing

Our focusing system is usually quite fast at focusing.  Most people can focus at near in about 1/5 of a second as simulated above.

Accommodative Infacility

With accommodative infacility, there is a delay in the clearing of the print.  The simulation above shows how a student with this problem would be slowed.  Copying information from a chalkboard to your desk is a frequent activity in a classroom.  It takes the student longer to obtain and transfer the information.

For all of the above problems, lenses or vision therapy or a combination of both may be prescribed.  The success of treatment is quite high.  A few cases may require only short term use of lenses or vision therapy while others may have a need throughout their youth for this type of help.

Convergence Insufficiency can produce visual symptoms which also include blurred vision, double-vision, or jumbling and scrambled print as you try to read.

Causes

Convergence insufficiency occurs because of poor eye-teaming ability.  Initially when we view something up close the lines-of-sight from each eye should cross directly where we look at.  A tendency for the eyes to want to drift outward is present in individuals with this disorder.  In order to to keep the image clear and single, more effort is required in order to concentrate on the task.  This ever increasing effort is taxing and soon results in symptoms.  This disorder can run in some families.

Symptoms

Blurred vision at near, eyestrain while doing near work, headaches, sleepiness while reading, double-vision, frequent loss of place when reading,  inaccuracy while checking columns of figures or lists are common complaints.  Severe cases can result in an eye turn.

Diagnosis

A complete and thorough vision exam is required in order to detect this disorder.  During this exam tests must be performed at a near distance in order to measure the eyes tendency to drift and how much ability the eyes have to compensate for this effect.  If not performed this disorder can be missed by the doctor.

Treatment

1. Vision therapy is by and far the most successful treatment available for convergence insufficiency.  The goal of therapy is to build eye teaming ability to a level necessary to overcome the outward drift tendency.

2. Prism incorporated into an eyeglass prescription is a second option.  Success with this form of treatment is much limited than with vision therapy.  Very often adaptation to the new prescription occurs and the convergence insufficiency returns.

3. Alternatives include ocular muscle surgery however most experts do not support this mode of treatment today except in unusual cases.

Video on Convergence Insufficiency

This video reports on results from a study by the National Institutes of Health / National Eye Institute on the treatment of convergence insufficiency.

Cataract Surgery is Done with Lasers
Never – almost. Yes, experimental research but nothing practical yet developed. Nearly 100% of cataract surgeries are still performed with traditional microsurgical techniques. Lasers can be used after cataract surgery to clear up cloudy membranes. This is where the confusion may often lie.

All Red Eyes are Infections
It has been our experience in our office that most red eyes are due to allergies or dry eye.We see more viral than bacterial etiological causes. This is why your eye doctor can’t just call in some antibiotic. Antibiotics fight bacteria and do not kill viri or decrease allergies.

Refractive Surgery Forever Removes the Need for Eyeglasses
People may assume no more visits are required to the eye doctor after refractive surgery. In fact people need MORE FREQUENT eye care after eye surgery. Refractive surgery today has a better than ever chance of eliminating your refractive error. One condition it can not cure however is Presbyopia. Presbyopia is the natural loss of focusing ability which first shows symptoms past the age of 40. Increasing working distance, eyestrain, blurred near vision are its symptoms. Presbyopia is not treatable except for corrective lenses.

Contact Lenses can be Welded to the Eye if you Weld with Them In
Nope. Contact lenses actually have been found to protect the eye from severe injury. Less trauma has been observed following foreign bodies and chemical splash/burns to the eye. A contact lens has been found to act as a protective shield for the cornea often taking the brunt of damage.

Stronger Glasses can Fix Every Vision Problem
“All I need is a pair of glasses that will work.” is a complaint often heard by eye doctors from patients seeking second opinions due to eye and vision conditions which have deteriorated their ability to see. Neurological problems can interfere with vision. Post-concussion syndrome frequently complicates vision problems. Cataracts interfere with a person’s ability to see. Retinal diseases like macular degeneration often cause a desire for a patient to ask the doctor for stronger glasses. Sometimes they are prescribed, but often special low vision magnifiers, electronic magnification aids and other special aids are needed.

Poor Night Vision is Infrequent
This is actually our most common complaint that we hear of. Small refractive errors is #1 cause. At night the pupil dilates which causes the eye to become more sensitive to changes in an eyewear prescription. Cataracts, macular degeneration, optic nerve disease and contact lens overwear can decrease night vision as well. Nicotine has been shown to decrease the ability to dark adapt. Dirty car windshields can create a phenonema known as the Mandelbaum effect. The focusing system draws inward creating an artificial form of near-sightedness. Night myopia is a similar phenonema which can occur as well despite perfectly clear windshields. Rainy weather decreases your ability to see to drive at night. Wet roads decrease the amount of light reflected back to you from your headlights and increase the amount of light from oncoming cars. Often no detectable problems are found. Aging is a frequent cause of night vision problems. The retina takes longer to recharge its photoreceptor chemicals as we mature. Retintitis Pigmentosa, a traditional cause of night blindness is another retinal disorder which has classically been associated with poor night vision is actually very uncommon.

Eyeballs are Removed During Surgery
Rarely, surgeons usually work around them. The muscles and the optic nerve are of a fixed length. Removing the eye risks avulsing (tearing) of the optic nerve.

“I’m Legally Blind Without my Glasses”
By it’s definition legal blindness is 20/200 in the better eye with correction (glasses or contact lenses) or less than a 20 degree visual field in the better eye. To say you are legally blind without glasses is not in keeping with the true definition.

These Lenses are Scratch-Proof
No lens yet developed is truly scratch-proof. There is always some material which can scratch a lens. A diamond can be scratched by another diamond. Lenses instead should be termed scratch-resistant. A plastic lens with a scratch-resistant lens is more durable than a lens without the coating. Glass to this date remains the most scratch-resistant material – more durable than plastic with a scratch-resistant coating.

Most of the time, you can go to the eye doctor and get a pair of glasses without any trouble getting used to the them.  There are occasions when a patient can have trouble adapting to the changes in the prescription written by the doctor.  A prescription for glasses is similar to a prescription for medication.  Sometimes side effects can occur after a doctor writes a new prescription.  Yes, even lenses can have side effects.

Whenever a pair of glasses does not seem to work, we like to perform a failure analysis to determine the cause.  This process helps us to prevent from making the same mistake in the future as well as provide you with a clear explanation.  As you can see from the list of causes below, glasses design can be complex with many reasons for problems.

Below are reasons why new prescriptions don’t work for some people.

Getting new glasses during or after vision loss
Patients with vision loss from conditions such as a cataract, diabetes, glaucoma, macular degeneration or other conditions may not have had the real impact displayed to them until they get new glasses.

Despite counseling on part of a doctor or staff on the limitations to expect from new glasses, people may not process the information we try to tell.  It’s as if a psychological block, a type of denial exists, with a subconscious desire that new glasses fix all cases of blurred vision.  Their past experience with visual blur had always been improved with new glasses.  They remember the positive impact new glasses made.  This expectation is probably strong and seems to persist in some patients despite even careful counseling.

When they see for the first time that new glasses didn’t help, it can hit one like a brick wall.  This is the first real impact of their vision loss.  Despite the education, the emotional wall now breaks down.  Denial can turn into anger (see the 12 stages of healing) for the eye care professional who are trying to do their best.  Sometimes we as eye doctors may not have counseled our patients well enough for them to be prepared.

Stress in one’s life can influence our adaptability to new lenses.  Going through a major illness, family changes, grieving, compound our ability to get used to new eyewear.   See another post titled Can Emotions Affect Vision?

Large prescription change
A large change in prescription can challenge our ability to adapt to the new prescription.  Doctor’s will often have to cut the strength of the lens to aid in adaptation.  The prescription can be increased again later to further improve your vision.  We try to anticipate how much you can adapt and prescribe the amount which gives the greatest benefit.  Sometimes we find that this amount can be too much.

Astigmatism or prism not tolerated in the prescription
While a refraction may reveal the presense of astigmatism, it may not mean that a person should be prescribed the full amount or even any of it.  This and other conditions may produce a “pulling sensation” of one or both eyes while you attempt to wear the glasses.  Eye alignment problems such as convergence insufficiency can create similar trouble as well and may mean that vision therapy is required to correct the condition.

Awareness of optical material difference
A few people can notice an improvement in the clarity of glass compared to plastic or between plastic and some other material.  The advantages of a lighter weight lens may not be worth the change you notice.

Awareness of frame or edge of lens
Some individuals can become aware of the edges of the frame.  This effect is more noticeable if a dark color or a bold, plastic frame is chosen.  Some have described a sensation of being “closed in”.  This is often unpredictable and occurs more frequently in people who are getting glasses for the first time.  Selecting a rimless or a metal frame with a thin eyewire can improve this problem.  Contact lenses or refractive surgery are options also.

Monocular cataract (cataract in one eye)
A cataract in one eye can affect how we see with both eyes working together as a team.  Some people still have problems with their eyesight because the cataract still obscures their vision and interferes with their ability to see comfortably with both eyes.  Monocular cataracts can also result in prescription shifts which can cause other problems with adaptation which may be checked off elsewhere.

Binocular cataracts (cataracts in both eyes)
Cataracts in both eyes can deteriorate vision in mild to severe ways.  Eyeglass prescriptions change more frequently when cataracts are present.  An examination may reveal that glasses may help still even with the cataract.  When the glasses do not seem to help however and your problem still continues, cataract surgery becomes the best solution to eliminate the problem if all other eye health factors are normal.

Binocular interference
Glasses are usually designed to give each eye ideal vision by itself and under binocular (two-eyed) conditions.  When new glasses produce problems with eyestrain, headaches, double vision or dizzyness, the problem may be be due to the effect that the glasses are stimulating the brain to attempt to use information from both eyes whereas before only information from one eye was being processed at any given moment.  Unequal refractive error, eye turns, weak or unstable eye muscles and monocular cataracts all can create this type of problem.  Either the predisposing problem needs to be resolved to allow normal binocularity or the glasses will have to be remade to continue the “one-eye only” input style the brain is used to.

Eye alignment problem
A new pair of glasses can result in double-vision in some individuals.  This can happen while looking up or down the lens away from it’s optical center.  Symptoms can also occur while looking at near for a period of time.  Each individual has their own tolerance to how much deviation it can tolerate before giving headaches, eyestrain or double-vision.

Non-Optical problem
Some conditions can not be improved with a regular pair of glasses.  We do our best to try to confirm that glasses will help a person.  Conditions such as cataracts, macular degeneration, glaucoma, diabetic retinopathy can create decreased vision to the point which eyesight can not be improved with regular glasses.  “I just want a pair of glasses that will work,” is the most common comment mentioned to a problem which can not be fixed by glasses alone.  Special visual aids may be needed in these cases.  See the first section Getting new glasses during or after vision loss and Can Emotions Affect Vision?

Changes in vision due to a base curve change in the lens design
Most eyeglass prescriptions allow the manufacturing laboratory to decide on the base curve of the lens to give the best optical performance.  The base curve of a lens refers to the inherent curvature of the front surface.  Some prescription lenses while having the same power may have different curvatures because of the base curve selected by the lab.  Most people adapt to this new curve readily but some can not tolerate the change.  Remaking the same new prescription with the base curve of the old glasses solves this problem.

Image size difference between each eye
If prescription lenses of significant unequal powers are put into a pair of glasses, the image on the retina may not be the same size.  This creates a form of binocular interference as mentioned before.  This can occur by itself, with the development of cataracts or from eye surgery including cataract and retinal surgery.

Bifocal Power – Working Distance Problems
Bifocal strength is determined by several tests during your vision exam.  Each different power of a bifocal has a specific focal range – a zone of clear vision for that power.  The stronger a bifocal is, the closer in the material must be held.  A person’s natural reading distance may not equal the optimal bifocal strength determined in the exam.  Print held at your natural reading distance appears blurred until you hold it closer in.  Remaking the glasses with a weaker bifocal moves the zone of clear vision out to a person’s natural reading distance.  Computer screens often sit further out than a person’s natural reading distance and may require a trifocal, a progressive or a special pair of glasses designed for the computer’s distance.  Some people may notice that a blurred vision zone develops at distances beyond an arm’s distance which can be made clear with neither the top or the bottom of a bifocal lens.  When this happens, a trifocal with a third power segment or a progressive multifocal is needed to keep vision clear at this intermediate distance. There are some cases where vision may have deteriorated to the point where normal print needs to be larger to see it.  An easy way to magnify the print when this happens is to prescribe a strong bifocal.  This stronger bifocal requires a person to hold the material closer than they naturally would in order to help them see well enough to read.

Bifocal height problem
A bifocal can be set too high or too low.  The best height can vary from person to person.  Whenever possible we try to match the current relative height of the bifocal of your last pair of glasses if you are having no problems.

Bifocal line awareness
Some people can become perceptually aware of a bifocal line to the point of distraction.  This awareness normally goes away after the regular two week adaptation period.   If problems continue past this period, a prescription can often be remade in a pair of lineless bifocals or two pairs of glasses with one set for distance and one set for near.

Refractive shift since exam
Cataracts, diabetes, pregnancy and an unstable eye-focusing system are the most common causes for changes in prescriptions which occur in a short time.  Usually the underlying cause needs to be cured before a stable prescription can be determined.

For diabetes, one’s prescription can change as the blood sugar level varies.  Even after control, it takes 5 weeks or longer sometimes to get a reliable and repeatable refraction.

Cataracts can also cause prescription shifts in relatively short amount of time (weeks or months).

Medications can sometimes dramatically affect prescriptions.  We once observed a 7.00 D shift during the use of Topamax, a migraine treatment medication.

Specific Progressive Lens/”Lineless” Bifocal problems

Near area too narrow -  The usable width of most progressive lenses is not as wide as most conventional “lined” designs.  This can be a problem for people who tend to move their eyes only as they read and do not move their head.  If an acceptable wide near area progressive can not be found then a traditional bifocal or reading glasses may be needed.

Trouble adapting to lens periphery – The periphery of a progressive lens is blurry and can produce a swimming motion which may not be well tolerated by some.  This can produce motion-sickness like symptoms especially in people prone to this problem.  Traditional bifocals or single vision based glasses (one pair for distance and/or one pair for near) may be needed.

Lens Aberrations

Spherical aberration Some newer lens designs can get rid of distortions which make walls appearred bowed in or out.  Aspheric lenses can correct for this distortion but can in some create symptoms similar to base curve changes.  Traditional spherical designs can help correct this problem.

Chromatic aberration Colored fringes on lights may be noticed with high prescriptions in lens materials described as “lighter and thinner”  Chromatic aberration is caused by high index lenses that refract light differently for each wavelength which results in images splitting up and developing colored fringes.  This effect is more pronounced the further away from the optical center you view an object.

Waves Waves are defects in the surface of the lens.  The lens is not perfectly spherical in shape and distorts light in specific places creating a distortion in the image which can appear like waves.

How much change can humans adapt?
A study looked into the ability to adjust to new viewing conditions.  This experiment tested the absolute limits the human visual system could adapt.

The study paid college students to wear special glasses every waking moment of the day.  The students were told to put the glasses on from the first moment they awakened to when they went to bed.  They were to do everything with them on even shower and bathe with them on.

One half of the glasses were a simple lens with no prescription in it for a control.  The experimental half had glasses that turned the world upside down.  Up was Down and Left was Right.

The experimental group had a terrible time.  Imagine trying to navigate the world that’s upside down.  Walking was awkward and unsteady with poor balance.  Subjects developed headaches, eyestrain even nausea and vertigo.  Their handwriting was awful. They had trouble reading, eating, typing and moving around.  These symptoms lasted about 3 weeks.  Then remarkabily they all adapted.  In the second half of the experiment the glasses were taken away and the symptoms came back while adjusting back to the normal world.  Their recovery was much shorter – 3 days instead of 3 weeks.

This experiment showed that with extreme prescriptions, adaptation is possible.  It also showed that a motivated individual will work at keeping their glasses on to allow adaptation.  In the experiment, college age students were being paid to participate.  They had a motivation to succeed to earn the money.

In the real world

In the real world, we can’t expect people to change to this dramatic amount.  Fortunately no eyewear prescription is ever this disruptive.  We can ask that they try to give it 3 weeks of real committed effort.

Another factor involves age.  Subjects age 20 will adapt more easily than subjects age 30 and age 30 subjects will adapt more easily than age 40 and so on.  Neurological adaptation slows over the decades.

A 70 year old with real vision problems caused by a retina disease will be a real challenge.  There will never be an instant fix in acclimatizing with glasses. Their expectations are based on previous glasses instantly sharpening vision and feel disappointed when this is not achieved.  Or the glasses may swim and swirl around because somehow they are “too strong” or “too weak” or “not right.”

Even folks age 40 can have trouble adjusting to their first progressive lens.  The same observations have been reported in people getting used to a no line bifocal.  This effect is more common if a history of motion sickness or a condition like Meniere’s disease exists.

Hang in there.  Eye care professionals do the very best we can to help.

Getting a new pair of glasses
Patients with vision loss from conditions such as a cataract, diabetes, glaucoma, macular degeneration or other conditions may not have had the real impact displayed to them until they get new glasses.

Despite counseling on part of a doctor or staff on the limitations to expect from new glasses, people may not process the information we try to tell.  It’s as if a psychological block, a type of denial exists, with a subconscious desire that new glasses fix all cases of blurred vision.  Their past experience with visual blur had always been improved with new glasses.  They remember the positive impact new glasses made.  This expectation is probably strong and seems to persist in some patients despite even careful counseling.

When they see for the first time that new glasses didn’t help, it can hit one like a brick wall.  This is the first real impact of their vision loss.  Despite the education, the emotional wall now breaks down.  Denial can turn into anger (see the 12 stages of healing) for the eye care professional who are trying to do their best.  Sometimes we as eye doctors may not have counseled our patients well enough for them to be prepared.

Crime scene witness differences
Eyewitness testimony in the previous century was considered the best evidence possible.  Now it is considered nearly the worst.

Emotional factors influence the reliability and accuracy of witness descriptions.  The stress factors involve in a crime can influence the ability for a witness to recall events accurately.  Several studies have shown that different people will describe events differently and offer differing descriptions of the perpetrator.  Differences even occur when stress is eliminated and witnesses just watch a video of events.

Color Vision and Emotion
One study from Caltech suggests that color vision evolved and improved to help humans see emotion.  In addition to food identification, the neurobiologist theorized it was socially important for humans to interpret the emotions of others.

Post Traumatic Stress Disorder

PTSD has well documented effects on vision. The most common effect is blurred vision.  The study quoted notes several possible ways blurred vision can occur but the symptom itself can be vague and difficult to discover why.  From a clinical perspective, I have observed patients reject new eyewear with reports of blurred vision even though all tests were exactly on target with the prescription.  Stress can cause blurred vision.  Not just severe stress like PTSD but any greater than usual stress such as divorce, social changes, life changes, major illness of self or a loved one, and employment-related concerns.  The ability to adapt by a minor change in a prescription may be the straw that breaks the camel’s back if one is already coping at their maximum ability of other stressors.

How do we see?

When we look at an object, called the “object of regard,” each eye forms an image of the object on the retina, the light- sensitive membrane lining the inside of the back of the eye.  The image produced is termed the “image of regard.”  After being processed in the retina, it is converted into electrical impulses which are transmitted along the optic nerve to the visual centers of the brain.  Although the brain is presented with a pair of images of the same object, one from each eye, it fuses the two images into one.  The result of this process is what we think of as our vision.

A child’s eye-brain system is amazingly plastic or pliable and is not mature until the child reaches eight or ten years of age.  Even past this age, recent studies show evidence of remarkable plasticity well into adulthood.  But this does not imply that a younger child’s vision cannot be normal.  Indeed, the average child has 20/20 visual acuity by the age of nine months.  None-the-less, subtle development does occur in this system until the child is considerably older.

Each eye has brain cells associated with it that respond only to that eye. There are other cells in the brain that respond only to stimuli from both eyes.  These are termed binocular cells.  Because of the plasticity of these eye-brain connections in younger children, both types of cells need continuous input to ensure proper maturation of the visual system.  Any disruption in this maturation process may cause problems.  Amblyopia is the term for a major interference with this visual development.

In some ways each eye is designed to be competitive with its counterpart, i.e. there is a rivalry between the two eyes for the brain’s attention.  When something interferes with one eye’s imaging and processing functions, that eye can lose vision and become amblyopic.  The eye itself may function normally without any permanent damage, but the brain becomes less and less attentive to it and begins to rely more and more on stimuli from the other eye.  An actual loss of cells, including binocular cells, occurs in the brain area serving the amblyopic eye.

Causes

Any condition that interferes with normal retinal processing or clear vision can produce amblyopia.  There are three main ways that this interference can occur:

1.  Strabismus — A constantly crossed eye does not image the object of regard.  Therefore, a child with esotropia, or crossed eyes, who always looks at the world with his left eye while his right eye is crossed does not receive the same visual information in each eye.  The deviated right eye receives deprived information.  Because of the rivalry in the brain, the visual input from the constantly deviating eye is ignored or shut off and more and more the brain depends on visual information from the straight eye.  Ultimately, the constant deviation and poor visual processing in one eye leads to amblyopia in the brain cells serving that eye.

2.  Deprivation — Anything that prevents a clear picture from reaching the retina can produce amblyopia.  A classic example is a cataract in a child.  When an adult develops a cataract, surgical treatment usually corrects the vision to 20/20 whether the cataract had been present for one month, one year, or even ten years.  But in a child, even if a cataract has been present for a short time–even a matter of weeks–surgery to remove the cataract may not restore good vision.  The youngster’s visual brain cells, having not received clear images through the cataract, may already have become amblyopic.  Other disorders that can cause deprivation are corneal scars and opacities, and opacifications elsewhere in the system caused by a variety of eye diseases.

3.  Anisometropia — This is very common, and unfortunately, a very insidious type of amblyopia because it is without any sign or symptom in a child.  Anisometropia is by definition an imbalance between the refractive error of each eye.  That is, one eye has a need for a stronger spectacle correction than the other eye.  For instance, the right eye may have two units of farsightedness, whereas the left eye may have four units of farsightedness. Consequently, the left eye receives a more blurred image than the right.  That image is ignored and the brain cells serving that eye deteriorate while the brain concentrates on the clearer image from the right eye.  This process may also occur with astigmatism or nearsightedness.

Diagnosis

The diagnosis of amblyopia requires a complete optometric exam.  As noted above, a normal child does not reach 20/20 visual acuity until nine months of age; however, the vision can be checked as early as three to four months of age. The symmetry of vision rather than absolute acuity is assessed initially.  This comparison between the two eyes may detect a difference in their ability to see clearly.

Ideally, most children should receive an initial visual screening from their pediatrician or family physician at approximately six months of age.  If a problem is detected, or if there is a suspicion of an abnormality, a complete vision examination by an optometrist is recommended to assess the visual acuity of each eye, to look for the presence of any eye disease, such as strabismus or cataract, and to determine the refractive error or power of glasses that might be prescribed.

Another common source of amblyopia diagnosis is a screening program which may be carried out by certain organizations, clubs, or day care centers, etc.  If a child goes through a screening program and an abnormality is suspected, he should receive a referral to an optometrist.  Primary care physicians and group screening centers can only suspect the problem; it is the optometrist that must confirm the diagnosis and carry out the definitive treatment.

Treatment

Treatment for amblyopia is twofold: correction of the underlying problem and therapy of the amblyopia itself. Obviously the treatment for the underlying disease, whether that be a strabismus, an anisometropia, or a unilateral cataract, depends on the particular condition that is present.  The treatment for amblyopia is best done in a step-wise process.   The child may be placed in glasses and occlusion or patch therapy to cover the good eye.  Several non-prescription elliptical eye patches are commercially available.  Like BandAids, they stick directly to the skin with their own adhesive.  They cannot be stuck to the glasses, as the child will simply look over the top of the frames.  Occluding the good eye forces the brain to rely on the amblyopic eye, slowly reversing the brain cell deterioration.  Recovery usually takes several months, although it can occur in a shorter period of time in very young children.  Eye patches may be worn for anywhere from several hours per day to all the waking day.  Some optometrists prefer intermittent patching, i.e. two hours per day, eight hours per day, etc., while others advise full-time occlusion.  This type of treatment howe ver, does very little to restore the function of the binocular cells which require input from the eyes at the same time.  Visual acuity may improve but binocular vision may not be restored.  

Studies in recent years have also reinforced the effectiveness of using cycloplegic eyedrops as a patching alternative.  These are drops (the same as dilating drops) which “turn off” the focusing ability of the better seeing eye to help stimulate the amblyopic eye into better use.   This can have a similar effect as a patch but without the cosmetic appearance issues.  One study has even shown that weekend use of cycloplegic eyedrops can improve vision – allowing children to focus efficiently during the school week for studying.

The use of vision therapy continues to evolve and improve in the treatment of amblyopia.  New studies now show substantial improvements in vision in patients older than nine years, the age which used to be thought that little could be done for treatment.  The goal of vision therapy is to improve visual acuity by the use of activities to stimulate and develop vision in the weaker eye and to restore or improve binocular vision through the use of activities which strengthen a person’s eye-teaming abiltiy.

The most important concept in the treatment of amblyopia is the age of the child.  The earlier the amblyopia is detected, the better the potential for succes with treatment.  The above limitations relate to the plasticity of the brain that was mentioned earlier.  The eye-brain is flexible enough to reverse the cell deterioration in the first few years of life, but after that crucial time period, the amblyopic condition becomes more difficult to remediate.

There is one other form of amblyopia treatment that is much less commonly employed and  involves placing an eye drop in the good eye causing the vision to blur in that eye more than the other eye.  As with patching, the idea is to stimulate the brain’s attentiveness to the amblyopic eye.  Most doctors use this method sparingly.

Treatment options for amblyopia and success rates are better than ever thanks to newer techniques and recent reseach validating these methods.  If treatment has been limited to only one of the above techniques then the patient should seek further treatment.  Amblyopia treatment involves a commitment between the doctor, the patient and the parent to best treat the condition.

Amblyopia is a condition of underdeveloped vision.  Findings of underdeveloped vision can be considered a constellation (grouping) of findings that include lowered visual acuity, decreased accuracy and ability of ocular movements such as pursuits (slow eye movements) and saccades (fast eye movements), decreased focusing abilities and decreased visual processing skills.   Decreases in stereopsis (3D vision / depth perception) and restrictions in visual field (tunnel vision) can be measured clinically.   Most cases develop as a result of an eye turn (strabismus) or undercorrected refractive error.  Amblyopia can occur in 2.5% of the population, making it responsible for more loss of vision than all ocular diseases and trauma combined.

Streff syndrome is a different type of amblyopia labeled psychogenic.  This type is under-reported in the medical literature.  Psychogenic means the origin is in the mind or more accurately in the parts of the brain that process vision.  Psychogenic amblyopia can involve voluntary and involuntary types.  Voluntary psychogenic amblyopia is also known as malingering – a process of faking a condition for some type of gain.  Involuntary psychogenic amblyopia involves vision and vision processing problems that occur in a patient who is not malingering.  Their problem is real, measurable and not being faked for some type of gain or attention.  There is no organic base for the problem meaning that there are no observed structural or anatomic anomaly that can account for the problem.  Saying that a problem is not organic however does not account for possible genetic, biochemical, electrophysiological or other abnormalities that may be present but for which we do not have the technology or background to identify them.  The word functional means that the normal expected work or function that a process is supposed to offer (such as correct focusing) does not occur.

Streff syndrome is believed to develop as a result of stress.  Hans Selye classifies stress as eustress – stress affiliated with change for the better such as marriage, getting an A on a test, being accepted into college or distress – stress affiliated with change for the worse such as divorce, family problems, substance abuse, emotional abuse, health problems.  A reaction from too much stress can include behaviors that trigger a person’s alarm mode especially if there is to0 much stress leading to an overload.

A diagnostic pattern has been described for patients susceptible to Streff syndrome.

• Prepubescent or early pubescent ages 10 – 14
• Females more frequent than males
• Visual acuity worse than 20/20 to  20/200
• Visual skills problems in ocular movements, ocular focusing, visual information processing.

Symptoms noticed by patients, parents and teachers can include:  a sudden decrease in academic performance, lack of desire to pursue homework, increased errors on homework, blurred vision at distance and at near, blurred vision of varying amounts which can come and go but usually stay blurry and headaches.

Sometimes the eye care professional can elicit a recent history of family stress, social stress, recent relocation.

The main clinical treatment of this condition is the use of a low plus eyewear prescription.  This may be in the form of reading glasses or a multifocal.  The effect of this prescription reduces the visual stress by just enough to allow the visual system to re-engage, organize and process information efficiently.  Results are usually quickly obtained with improvements seen within a few weeks.    Some cases may require vision therapy to improve eye movements and focusing.   In cases unresponsive, eye care professionals should always rule out organic pathology both at the time of the initial diagnosis and later on.

In 1962, Dr John Streff first published a description of this condition.  Articles in the optometric literature are more numerous than ophthalmological literature.  This condition needs more research.  The condition is considered functional in nature.  Functional means no organic pathology exists but the software programming of the visual system is inefficient or not working as it should.

More Information:  Streff Syndrome.pdf
(an information pamphlet written by Paul Harris, OD on this condition)

Much of this information is adapted from: Press, Leonard. Applied Concepts in Vision Therapy, St. Louis:  Mosby 1997

Cook, Douglas T & Maples, WC. NSUOCO Vision Therapy Pocket Reference, Tahlequah:  SITE 1994