Legally Blind

“Pt is legally blind”

What does it mean when a patient is legally blind? Technically, to be legally blind, ones visual acuity in best correction is less than 20/200. Here is a great simulator to help one imagine what that would look like. But functionally, how does does being “legally blind” affect the patient?

We need more information

A patient can be legally blind for several reasons. Cataracts, macular degeneration, and diabetic retinopathy all leave a patient with reduced visual acuity but leave the patient with very different residual vision and different functional problems as a result of this condition.

A patient with macular degeneration will have reduced vision in the central field affecting reading and the ability to see faces like the below picture.

can-macular800

Glaucoma will result in reduced peripheral vision that could affect balance and peripheral awareness.

Vision-With-Glaucoma-2

With retinopathy, the areas of reduced vision may be more random and will have different affects depending on just where these damaged areas are.

retinopathy

How bad is it?

Is the patients vision truly 20/200 or is it worse. Visual acuities can be 20/400/ or even 20/1000. A patient that was 20/400 and now is improved to 20/200, will find their vision to be much improved and very happy about that. A patient may have an acuity described as “nlp” or no light perception. In this case, the patient would see nothing but blackness.

Is the described acuity with glasses in place? A specialized low vision refraction from a low vision optometrist could get the patient improved visual acuity optimizing their residual vision.

Ask the Right Questions

Why does this patient have low vision? How bad is there acuity? Are they wearing the best possible glasses for their diagnosis? With this information, we will be better able to assess the functional implications of this patients reduced vision and come up with the most effective strategies to keep them independent and safe.

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From Vision Rehab to Pediatric therapist doing VR

Vision Rehab comes to Pediatric Clinic(*)

The optometry practice I had worked at was sold and the new owner did not wish to continue the OT program. I was quickly welcomed by the program manger and lead OT at the Pearl Nelson Child Development Center. I had previously treated both of these wonderful ladies’ children and they recognized the potential of adding vision rehabilitation to the impressive list of services offered by PNC. Thanks to Drs. Carl and Katie Spear who have generously allowed me to continue to use the Visual Performance Center equipment so I can continue to provide this much needed service to a bigger population.

“Why do you assume they can see?”

Dr. Mark Obenchain asked me this not long after we began to work together. We assume a child with PT, OT, SLP, pediatrician, neurologist, and behavior specialist has surely had an appropriate pediatric eye exam. As therapist’s, we ask about the most recent vision exam but get a variety of answers.

  • “He passed the school screening”
  • “We had him checked a few years ago”
  • “The doctor said he didn’t need glasses”
  • “He had glasses but broke them six months ago and we haven’t got new ones yet”

I do a brief binocular vision screening as part of seeing any patient for the first while I ask about the most recent eye exam. When I am done, I ask if the doctor did any other things they watched me do. Most often they did not.

American Optometry Association Eye exam recommendations

The eyes of our special children need special care. The first eye exam should be at six months. This exam can be covered by the InfantSee program which offers this important first exam at no cost.

The AOA then recommends for “at risk” children  a second exam at 3 years of age, then annual exams from 6 to 18 years old. (1) These exams should include a binocular vision assessment and cycloplegic refraction/retinoscopy as recommended by the AOA clinical practice guideline.

Many of our special needs kids will not find this process enjoyable but it is a very important part of ensuring we are doing everything to help our special children.

Parents do your research

As parent begin to look for the right eye doctor for their special needs child, asking the right questions can help find the right doc

  • Ask other parents who they take their child to for eye exam. Parents of special needs children know the professionals that are best at working with their children.
  • When you call the optometry office, inform them of your child needs and ask if they have experience with special needs children.
  • Ask specifically  if they do binocular vision exams. The only acceptable answer is yes.

“Step one…Can they see??”

Our special needs kids have problems with fine motor skills, balance, visual motor integration, and gait. All of these skills require the best vision possible for therapy interventions to be most effective.

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*I know the first person blog post is considered a no-no, but given the big changes I felt I could bend the rules.

 

 

 

 

 

Dyslexia and Vision Rehabilitation

Dyslexia and Vision Therapy

Dyslexia is word frequently tossed about when children have problems reading or learning. Commons complaints that lead to the use of the word include letter reversals, poor reading comprehension and decreased reading fluency. These symptoms are also recognized as possible vision related problems cause by poor eye movement accuracy.

Is dyslexia a vision problem or a language problem?

Attempting to define dyslexia can be confusing. The origin of the word is vague: “dys” meaning difficulty with and “lexia”  meaning reading lends itself to broad interpretation.  The best definition for dyslexia, from the International Dyslexia Association says:

“Dyslexia is a specific learning disability that is neurobiological in origin. It is characterized by difficulties with accurate and/or fluent word recognition and by poor spelling and decoding abilities. These difficulties typically result from a deficit in the phonological component of language that is often unexpected in relation to other cognitive abilities and the provision of effective classroom instruction. Secondary consequences may include problems in reading comprehension and reduced reading experience that can impede growth of vocabulary and background knowledge.”

The research shows that the root cause of dyslexia is phonological processing, or how the brain processes sounds in language. Additionally, the prevalence of dyslexia is estimated to be between 5-20% of the population, according to the National Institute of Health: http://www.ninds.nih.gov/disorders/dyslexia/dyslexia.htm. *

Reading is a complex process involving language, speech, memory and other processes, but all of these processes assume that the collection of the information to be processed is accurate, ie that the eyes work correctly and move accurately. We do know that poor eye movements lead to poor processing skills because the data to be processed was not collected accurately.

Does vision therapy treat dyslexia?

This is also a very interesting question. In our vision rehab practice, we frequently get children referred to us that have common symptoms of dyslexia and visual processing difficulties like reversals and poor reading skills. Following the interventions, the children have reduced symptoms and most have improved reading fluency.

Some of patients do continue to have problems in reading although they show improved eye movements. At this point, we may further assess the patient using a dyslexia screening tool that can identify specific errors related to the processing parts of reading such as the decoding and encoding of words. When results indicate, we refer those children to specialists like our friends at Read-Write Learning Center at  that specialize in the treatment of dyslexia.

 

Does vision therapy treat dyslexia????

NO. Vision therapy cannot treat dyslexia. But it does improve the accuracy of eye movements eliminating many of the symptoms generally associated with dyslexia. With these eye movement problems gone, an accurate assessment of the visual processing skills and reading fluency is now possible, allowing for an accurate diagnosis of a visual processing or other reading and learning problems.

Here is a video case study describing the process.


*Special thanks to Hunter Oswalt, Director of the Read-Write Learning Center for her input on editing this post.

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Assessing visual fields

Assessing visual field in the OD office

Heres is how visual fields are assessed in the optometry office.

humphery

This is Humphery visual field tester. The test is generally done monocularly first. The patient places their face on the chin rest and clicks a switch when they see a light in the field. The device monitors fixation during the test and lets the tester know if the patient “cheated” by moving their eyes. Binocular testing may be done separately if needed. During this, the patient is allowed to move their eyes.

The results are very precise with even small peripheral reductions in field picked up. But there are some limitations. The patient must be able to respond in a timely manner by clicking a button, so motor response time and even posture can affect the ability to perform testing on this device.

Confrontation Field Testing

Visual field testing by confrontation is a way to perform visual field testing in clinic without the computerized tester.

In the test, the therapist sits in front of the patient presenting fingers in each field with patient reporting the number of fingers up. This is done for each eye.

It is important to present stimulus in all four quadrants of the visual field. Results of this can be correlated with other visual cancellation tests.

There is also campimetry which uses a specialized disk with different fixation points.

photo (15)

With the campimetry device shown above, the patient fixates on numbers on the disk and reports if they can see the middle spot.

There is also a web-based Damato Multifixation Campimeter test for visual fields that is  free.

Types of visual field cuts

Homonymous hemianopia is the most common visual field loss following a neurological event. This is lose of half of the visual field in each eye . These can affect right or left visual field (generally contralateral to the affected side of the brain, left brain right field cut). These tend to be associated with tempro-parieital lobe or occipital lobe damage. Left side field cuts tend to have a neglect aspect associated with them. The patient may not even be aware of the left sided vision loss making treatment of the field cut more difficult. Right sided field cuts tend to be more occipital lobe related with the patient showing improved awareness of the loss and improved recovery. Here is what it would like using a Goldman 30-2 test. This test looks at each eye separately and requires fixation.  The similar patterns in each eye tells us this a visual pathway problem, not and orbit problems.

visualfields-page-003 visualfields-page-002

 

Here is what it looks like on the Easterman Binocular Test. This test uses both eyes, allows for eye movements and is a more functional look at patient useful visual field.

visualfields-page-001

Quadrantanopia is loss of vision in a quadrant of the visual filed (upper right, lower right, upper left, lower left). It can also be homonymous (in both eyes) and may be described a superior right homonymous quadrantanopia.

quad

This is what that might look like.  They might also be bitemporal ( in the lateral fields of both eyes) or binasal (in the medial fields of both eyes)

A central scotoma is is loss of the central visual field and is associated with age-related macular degeneration.

visualfields-page-005 visualfields-page-004

 

 

Visual field treatment

Their are two common strategies behind improving functional status for patients with a field cut. We tend to use a combination of both at the optometry office.

The most common technique is to improve scanning strategies by having the patient perform scanning tasks into the area of the field cut. This can be done with any number of devices such as a Dynavision or a Sanet Vision Integrator. Both of these devices, and others, present random targets in a field with the patients ability to find these targets being timed. With either of these, patient practice scanning strategies which improves their awareness of the field and improves their time locating targets in the missing field.

In optometry, we have other tools available. We can use field expansion systems such as the Peli-lens or Gottlieb Field awareness system. Both of these involve the application of small pieces of prism to the lens of the patients glasses. These small strips move visual stimuli into the patient’s existing field “reminding” them to look to the affect side.  They cue the patient to scan into the missing field, something like a warning system.

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Balance and Vision

 

Two Visual Pathways

The focal, central or Parvocelluar visual system is called the “What” vision system. It is responsible for object identification. It allows us to focus on a specific object in the visual field. This information is interpreted in the occipital lobe.

The ambient/peripheral or Magnocellular visual system is the “Where” system responsible for spatial information, balance, coordination and peripheral awareness. This information is shared with the occipital lobe, in addition to links to the cerebellum and balance areas of the brain. Functional MRI shows this information actually reaching 99% of the cortex. Using ambient vision, we can automatically change our posture and gait to walk uphill or protect ourselves from falling over as someone bumps into us.

Functionally, these two systems allow use to look at the road ahead of us (focal vision) and be aware of the car to our left(ambient). It also allows us look at the TV but be aware of where the door in the room is. It allows us to be focused on a word in reading, but still make accurate saccades to the next word.

Notice what happens to the people attempting to walk through the tunnel.

Notice how the people in the tunnel are leaning to one side. The tunnel walls have confused their ambient vision system and affected the gait and balance.

A tool for rehabilitation…

Frequently this system can become faulty following a neurological event. In a condition called Post Trauma Vision Syndrome”, patients become over-centrally focused. This is seen clinically as decreased balance, decreased reading accuracy and poor spatial awareness a midline shift or toe/heel walking.  The patients also report becoming “over-stimulated” by visual information.   A visual field done a patient with this condition might look like this

peripheral loss

This is one eye, but the other may look the same. Notice the reduced periphery that might not show up in typical in-clinic screening of visual fields.  This visual field test is called a Goldman 30-2 and is done on each eye.  It  should be a standard part of the assessment of all of the post-TBI/CVA patients.

Improving Ambient Visual Function

To improve function of the ambient system, binasal occlusion may be added to a patients glasses with or without mild base in prisms.  How does this help?

A person that is over-centrally focused has a difficult time seeing the entire word. They tend to see letters rather than the whole word which greatly reduces reading fluency and comprehension. Saccades also become less accurate due to the decreased awareness of the line of text  making the person lose their place frequently.

This can also improve posture and gait. As the brain becomes more aware of the ambient visual system, it is better able to correctly adjust gait and posture. Remember the tunnel?

Optometrists that offer this type of service are involved in neuro-optometry. The organization is called the Neuro-Optometric Rehabilitation Association. This is a multi-disciplinary organization that was started by ODs who wanted to understand brain injury better and exchange information with other providers of care in the  TBI community like OTs and PTs. There is a provider list on their website to help you find a NORA optometrist in your area.

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How do we see up close?

The Near Vision System

“I can’t see the board” is a common reason children come for their first eye exam. But problems seeing close are more closely related to academic success then distance vision problems. With more computer use, and frequent changes from looking at the board to a notebook, school can be a workout for the near vision focusing system.

Watering eyes, rubbing eyes, and headaches are early signs of discomfort with near vision. These soon lead to difficulty reading and falling grades. The child may also show avoidance behaviors when trying to do school work as it is physically painful to see up close. But worst of all, the child may not say anything at all, as they do not know that their vision is not working right. Typical school vision screenings may miss the problem also.

The near vision system is a balance of several processes…

So what are the mechanisms involved in near vision focusing??

There are 3 processes involved in near vision focusing. Optometrists call it the near vision triad.

1) Pupil constriction- as an object moves closer, the pupils constrict to improve focusing of incoming light to the fovea. The fovea is an area on the retina with the highest density of light receptors. This area gives us our most acute vision.

2) Accommodative Convergence– as an object moves closer, the eyes move nasally to keep the object on the fovea. Both eyes should smoothly convergence together as the target moves closer.

3) Accommodation– lens of the eye focuses- In humans under 40 years old, the lens of the eye changes focus as objects move closer. This is much like a camera lens. As children, the lens is very flexible allowing for a large focusing range. After 40, the lens tends to become less flexible, so we end up wearing bifocals.

Here is a great example of it all working together:

As something moves toward us, the brain adjusts with the right amount of accommodation and convergence, in addition to the pupil constriction. The amount of both convergence and accommodation can be calculated by the the optometrist to come up with the AC/A ratio. This number gives the optometrist clues to the efficiency of the system.

What does it look like when it does not work right??

 

In some children, both of the lenses tend to over focus making them work very hard to maintain focus of near vision objects. The optometrist can assess this and improve it with glasses also. The child with accommodation problems will be rubbing his eyes during close work. He might complain of headaches when reading. He may show poor comprehension and poor reading skills. Or he may not show any of these signs. He may have a short reading span, or have a difficult time hold still, perhaps mis-identified as ADD.

Without enough convergence, the muscles that focus the lens tire as they work to keep near things in focus. They cause similar problems as poor accommodation and frequently a child will has both. This multi-process system is very flexible in children. Therefore, some children have problems coordinating the system. The condition is called convergence insufficiency and is a common vision problem in children. There will be a separate discussion of CI later.

This is easy to screen using the Near Point Convergence test .  

Only the optometrist can identify these problems, but as therapists, teachers and parents, we need to be aware of the signs of near focusing problems. The Convergence Insufficiency Symptom Survey  is a well researched tool that is very effective in identifying patients with possible CI.

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Learn more about this subject in a live course presented by Robert.  Its now available as a webinar too!! Hosted by PESI Education

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