Optometry (2012) 83, 19-26 Remote treatment of intermittent central suppression improves quality-of-life measures Eric S. Hussey, O.D. Private Practice, Spokane, Washington. KEYWORDS Abstract Dyslexia; BACKGROUND: Intermittent central suppression (ICS) is a repetitive intermittent (‘‘on-and-off’’) loss Electronic rapid alternate of central visual sensation without strabismus or amblyopia. These repetitive seconds-long suppres- occlusion; sions have been suggested to create visual confusion and instability that would cause vision symptoms, Intermittent central contribute to reading complaints, and even impair reading. suppression; METHODS: Teacher-identified Job Corps students were diagnosed with ICS and then treated with 5-Hz Quality of life; electronic liquid crystal shutter alternate occlusion. Suppression; RESULTS: Twenty-six young adult students (19.7 6 1.6 y) had their ICS treated over 5.9 6 3.7 months. Tests of Adult Basic Suppression periods decreased in length (P , 0.0001) and ‘‘binocular’’ nonsuppressed periods increased Education in length (P , 0.0001). Overall, College of Optometrists in Vision Development (COVD) quality-of-life (QOL) scores improved (P , 0.0001), 16 reading behavior COVD QOL questions improved (P , 0.0001), and individual QOL questions improved. Posttherapy reading scores (N 5 18) improved 3.7 (6 2.6) years (P , 0.0001). CONCLUSIONS: Treating ICS with electronic alternate occlusion reduced suppression periods, in- creased binocular periods, and improved symptoms as measured in the COVD QOL questionnaire. Pos- itive changes also occurred in reading scores. These data suggest ICS should be considered a probable cause for symptoms of reading problems. Optometry 2012;83:19-26 Treatment of the visual sensory defect of suppression has suppression in the 1950s.1,2 Most of the early thought on sup- been part of optometric vision therapy since its beginning. pression diagnosis, treatment, and neuropathology, however, Louis Jaques called for the treatment of nonstrabismic comes from study of strabismus and amblyopia. For exam- ple, Bielschowsky used the term diplopiaphobia referring Disclaimer: The data and graphs in this paper were discussed in a brief to a sort of ‘‘phobic’’ cortical response to diplopia that then presentation at the Sixth International Congress of Behavioral Optometry produces suppression in strabismus.3 In their seminal work, (ICBO), Ontario, California, April 11, 2010; and at the Joint Conference 4-7 on Theoretical and Clinical Optometry (JCTCO), June 3–7, 2010, and Hubel and Wiesel discovered changes in visual neurology the Northwest Congress of Optometry, February 26–27, 2011, both at in kittens when their eyelids were sutured shut, providing Pacific University, Forest Grove, Oregon. insight into the deprivation and constant suppression of stra- Dr. Hussey is the primary inventor of the electronic rapid alternate bismus and amblyopia. However, the explanations and occlusion goggles. No commercial version is yet available. Clinical studies descriptions of strabismic/amblyopic suppression did not continue. There are no other potential commercial conflicts of interest. * Corresponding author: Eric S. Hussey, O.D., 25 W. Nora, Suite 101, fully explain nonstrabismic, nonamblyopic, intermittent cen- Spokane, WA 99205. tral suppression (ICS). Both types of suppression are visual E-mail: [email protected] sensory defects that suspend, at least for a short time, central 1529-1839/$ - see front matter Ó 2012 American Optometric Association. All rights reserved. doi:10.1016/j.optm.2011.05.009 20 Optometry, Vol 83, No 1, January 2012 visual sensation. Therefore, both represent a loss of intact Allen15 advocated alternating flicker for strabismus sup- central visual sensation. Beyond that, the 2 suppression con- pression treatment using flashing lights alternating in a ditions show almost as many dissimilarities as similarities.8 square-wave pattern at 9 Hz. The 9-Hz alternation rate Strabismic/amblyopic (constant) suppression is viewed was thought to make use of the 9-Hz Bartley phenomenon often as a constant cortically based inhibitory loss of central, brightness enhancement, theorized to represent improved and possibly paracentral, visual sensation.9 In unilateral transmission of the visual signal to the cortex.15 Similarly, constant (strabismic/amblyopic) suppression, occlusion of electronically controlled liquid crystal shutter lenses the sighting eye will override the inhibition of the visual neu- (see Figure 1) can serve as the visual flicker-producing rology and ‘‘force’’ the strabismic/amblyopic eye to see, at tool, producing a rapid alternate occlusion rather than least while the normally sighting eye is covered. Some alter- bright flashing. The strongest, most efficient antisuppres- nation occurs in alternating strabismus, but usually with a sion alternate occlusion frequency, as determined empiri- degree of patient volition. cally during a stereoscope drawing task, is approximately ICS, on the other hand, is a repetitive, intermittent (‘‘on- 5 Hz. Further, that 5-Hz alternation pace fulfills the 2 re- and-off’’) loss of central visual sensation. Although vari- quirements for an antisuppression therapy: bilateral sight able, a typical ICS ‘‘cycle’’ might consist of repetitive 2- to and motion. On-off flicker is motion in stimulus 3-second suppressions spaced by similar periods of bilat- form.16,17 Direct square-wave alternation between the eral sight. Eighty percent to 90% of ICS patients alter- eyes at that 5-Hz pace is fast enough that the central vision nate.10,11 While a strabismic patient might control an reads the signal as continuous, that is, as bilateral and with alternation, a typical ICS patient will very much act as an little central flicker. Paradoxically, then, electronic rapid al- observer in a diagnostic examination, reporting the changes ternate occlusion (or Allen’s flashing lights) delivers a in visual sensation, including alternation, but not control- strong bilateral motion stimulusdstrong enough for anti- ling them. suppression therapy. Other vision conditions that commonly accompany stra- The treatment goal of decreasing suppression in, for bismic versus ICS illustrate additional differences between example, intermittent exotropia is understandable, but what the 2 types of suppression. Strabismus and amblyopia, and is the interest in nonstrabismic, nonamblyopic ICS? Some the co-occurring suppression, often are associated with suggest a link to reading problems, possibly dyslexia. significant refractive errors.8,9 ICS patients fit very normal Strauss and Immerman,18 Annapole,19 Safra,20 Miller refractive error distributions.10 Amblyopia by definition is et al.,21 and Hussey10,11 have suggested a diagnostic link reduced acuity in 1 eye. ICS patients show very normal to reading problems. In contrast, 1 study found little inci- and equal acuities. Both strabismus and amblyopia reduce dence of ICS as described above in a university student stereopsis scores, whereas ICS patients can show normal population with good reading skills.22 Miller et al.21 and stereopsis scores.10,11 Hussey23,24 have also treated ICS and found improvements Although cortical inhibition can explain the constant in reading, quality-of-life (QOL) measures, or other visual suppression of strabismus and amblyopia, it fails to explain tasks, such as marksmanship. This current study updates a the intermittency and alternation of ICS. What cortical previous pilot study for treating ICS with electronic liquid mechanism can explain a loss of sensation that switches crystal rapid alternate occlusion in isolation at a location re- eyes, is intermittently inhibitory (that is, actively inhibitory, mote from in-office treatment availability.23 then not actively inhibitory, then actively inhibitory on the opposite side), and all of that repetitively? Further, the Subjects genesis of ICS associated with whiplash cervical trauma 12 has been documented, but without visual field defect. All subjects came from a Job Corps site in north central What strictly cortical inhibitory mechanism is there that Washington state. According to the Job Corps Web site, ‘‘Job is triggered by trauma? What traumatic cortical damage Corps is a free education and training program that helps has been documented that apparently is sufficient to inter- young people learn a career, earn a high school diploma or mittently interrupt visual sensation by traumatically pro- GED, and find and keep a good job. For eligible youth at ducing inhibition but is insufficient to produce a field defect? The putative cortical explanation of suppression fails to explain ICS.13 Active therapies for suppression, and ICS in particular, almost always involve 2 components: a bilateral (bioptic) visual environment (e.g., a stereoscope) and visual motion.14 Common techniques include cheiroscopic tracings, in which the bilateral stereoscope visual environment incorporates a moving pencil, a Brock string, in which plucking the string brings visual sensation back in a suppressed eye, and disso- ciated eye movements using a rotating visual target while Figure 1 The alternate occlusion goggles show 1 liquid crystal lens looking through dissociating prisms. occluded. Hussey Clinical Research 21 least 16 years of age, Job Corps provides the all-around skills fill out. The COVD QOL checklist has repeatedly proven a needed to succeed in a career and in life.’’25 The treatment valid and reliable symptom survey for pre- and posttherapy group of students was, at the time of original