Griffin; pp 475-479
Scheiman; pp. 161-169, 194-195, Ch 12
Richman (Bernell Guide); pp. 8-14, Activity C-1 to C-13
I. Introduction: Cases which involve accommodative dysfunction are numerous. A child may present with a myriad of chief complaints ranging from difficulty seeing a chalkboard after reading to constant headaches and constant blurred vision. Accommodative dysfunction is usually divided into 4 categories.
A. Accommodative infacility: (a.k.a. inertia of accommodation) Hallmarks of this disorder stem from the inability to rapidly or efficiently shift accommodation to match demand. Symptoms include:
1. distance blur, particularly after near point tasks
2. working distances for near point tasks that tend to be too short
3. asthenopia and headaches after near point work
4. possible intermittent diplopia
B. Accommodative excess: Patients with this disorder perform much better when accommodating than when forced to relax it. The symptoms presented are very similar to those for accommodative infacility.
C. Accommodative insufficiency: Symptoms of this disorder usually fluctuates with the amount of near work attempted. They include:
1. blurred vision (distance and/or near) that is usually intermittent
2. asthenopia
3. excessive tearing on near point tasks
4. general fatigue
D. Ill-sustained accommodation: These patients usually present with very vague complaints. The common denominator is a decrease in visual performance as the time of near point stress increases. Symptoms are quite similar to accommodative insufficiency.
1. blurred vision after considerable near point work
2. tearing and burning sensation
-Case History: A diagnosis is made difficult based on symptoms alone (did you notice a slight overlap in symptoms,...or was it just me?), a detailed case history is rendered necessary. This case history should include:
a. time of onset of symptoms
b. progression of symptoms
c. "triggers" for symptoms
d. what the patient does to eliminate the symptoms
e. if a school-aged child, inquire about academic progress (i.e. does the child avoid reading)
f. if a school-aged child, ask how long they can read before symptoms arise
II. Visual Dysfunctions Encountered In Each Of the Four Binocular Vision Modalities: Analysis of a patient's skills in each of these areas should be completed before a VT program is planned.
-Modalities:
1. Oculomotility: the occurrence of functional oculomotor deficits is quite common. This is especially true for patients with multiple binocular vision problems. The possibility of oculomotor problems need to be ruled out before therapy gets too involved; it can hamper timely remediation of what is primarily an accommodative dysfunction.
2. Anti-suppression: for normal binocular accommodative pattern to be established or enhanced, suppression, even under significant binocular stress, should be held at a minimum. Suppression is a common part of any binocular dysfunction. It should be monitored throughout accommodative therapy.
3. Accommodation: naturally, the accommodative function is of primary importance in these cases. Detailed testing of accommodative function should be completed to better establish a proper "starting point" for therapy.
4. Vergence: vergence skills are almost always affected by and accommodative dysfunction. The question is, how much? Evaluation of vergence ability along with a fixation disparity curve determination will better guide you into a suitable therapy regimen for your patient
-Binocular Skill Level: Once the diagnosis is made, the next task is to plan a vision therapy program around the individual needs of a particular patient. Most accommodative therapy involves the use of near/far or lens accommodative facility techniques. Although many techniques have been developed, they all fall into the four skill levels discussed in class and lab.
A. At the MONOCULAR LEVEL:
1. Monocular accommodative rock is the first step in therapy. Modes of therapy are similar to the methods used to assess monocular accommodative facilities. The patient changes accommodative posture to a target presented monocularly as he/she changes viewing distance or has a spherical lens introduced. After a few minutes of work, the procedure is repeated for the other eye.
2. Alternate accommodative rock is usually the next step in accommodative therapy. The patient still is changing accommodative posture to changing working distance or lens power with one eye occluded. In this case, however , one eye receives the stimulus for accommodative relaxation (plus lens or distant target), while the other eye receives the stimulus for accommodative stimulation (minus lens or near target).
B. At the TRANSITIONAL LEVEL:
1. Monocular fixation in a binocular field is the third type of accommodative therapy. Here, both eyes are open and usually red/green or Polaroid glasses are worn. Under the proper conditions, some visual stimuli will be presented to both eyes (the border of the target and peripheral visual fields) while certain information is only seen monocularly (due to color cancellation or cross polarization). In this procedure, a different lens power is worn over each eye. Plus (or less minus) lenses are worn over one eye and minus (or less plus) lenses are worn over the other. One eye receives the stimulus for accommodative relaxation (plus or less minus lens) , while the other eye receives the stimulus for accommodative stimulation (minus or less plus lens).
2. Biocular accommodative rock uses vertical prism dissociation. Here, both eyes are open and all visual stimuli are seen by both eyes. The patient should have vertical diplopia. In this procedure, a different lens power is worn over each eye. Plus (or less minus) lenses are worn over one eye and minus (or less plus) lenses are worn over the other. One eye receives the stimulus for accommodative relaxation (plus or less minus lens) , while the other eye receives the stimulus for accommodative stimulation (minus or less plus lens). The pt. will attend to one image, clear it , before going to the other image.
C. At the BINOCULAR LEVEL: Binocular accommodative rock with suppression checks is the first technique described where the patient is not under dissociative conditions (i.e. . the patient is fused). For the first time, the vergence system is also included in the regimen. Here the SAME plus or minus lens (or near and far target) is presented binocularly. In this case, both eyes simultaneously receive the stimulus for accommodative stimulation or relaxation. As was discussed last week, suppression checks are necessary to insure binocular response to the lenses.
D. At the INTEGRATED LEVEL: At this level the patient is ready to incorporate all his/her binocular skills into one cohesive package. A combination of extreme vergence, accommodative and oculomotor demands are created for the patient. An example may be binocular accommodative rock (with suppression checks) in combination with 8 BO/BI prism facility flippers: WOW!
-Progression Of Therapy: Now that you are familiar with accommodative therapy regimens at four binocular vision skill levels, the next question on your lips is, .."wow, that's neat, but how do I know when my patient is ready to go from one skill level to the next?" Thankfully, Richman and Cron (Bernell Guide, pg. 8) describe this progression quite nicely.
1. Establish an "awareness of error" by showing the patient (kindly) where weaknesses lie. It is important to show the patient what they are unable to do. This is the beginning of their learning sequence.
2. Establish an "awareness of change" from clear to blur (after changing targets or lenses) and back to clear again as the patient learns to accommodate to the conditions created for him/her. This is called CBC, for short. At this stage, the patient must make a voluntary effort to perform these tasks. It is called the control level.
3. The range of performance should be improved.
4. Eventually, the skills will be "learned" at a higher cortical level. An awareness of error will no longer need to be acted on by a conscious effort, it will be an internalized skill; the patient has reached the automatic level.
5. These skills are improved farther by introducing distracting stimuli and increasing efficiency and speed. This is a very important step, because it more accurately represents what is happening in real environments. The patient will need to accommodate while performing other cognitive tasks (like reading this lab while a loud-mouthed instructor explains, in gory detail, the most simple concepts). This ensures that the patient does more than learn various splinter skills that cannot be applied to real situations. At this point, the patient is ready for the next level of binocular skill.
6. Don't forget about prescribing plus lenses when they are accepted by the patient!
1. What are the diagnostic findings expected on the following tests for the three types of accommodative dysfunctions listed below:
Acc. Insuff. Acc. Ex. Acc. Infac.
a. MEM
b. monoc. +/- facility
c. binoc. +/- facility
d. NRA
2. List the four binocular skill levels of accommodation. Give an example of a type of accommodative technique that fits in each level.
1. 3.
2. 4.
3. What are the expected values for accommodative facility? If you read about this stuff, as I'm sure you do, why do you think there is such a wide difference in results of the work of various authors?(See Griffin, pg. 41; Table 2-15)
4. It is always important to keep in mind ways to manipulate the therapy procedure you are conducting to make it more appropriate for the skills of your patient.
a. If an accommodative excess patient was having difficulty clearing a plus one lens during +/- 1.00 monocular lens rock, how would you make this task easier?
b. If an accommodative insufficiency patient could easily clear +/- 2.00 monocular lens rock, how would you advance this patient to the transitional level?
c. If an accommodative excess patient has difficulty clearing the distance Hart chart after 3 cycles, how would you make this task easier?