Running Head: TREATMENT OF UNILATERAL AMBLYOPIA 1

Transcription

1 Running Head: TREATMENT OF UNILATERAL AMBLYOPIA 1 An Analysis of Treatment of Unilateral Amblyopia: A Multi-method Approach Jacob Sales Department of Psychology University of Minnesota

2 TREATMENT OF UNILATERAL AMBLYOPIA 2 Abstract Amblyopia is an exceedingly common visual deficit marked by poor visual acuity and subpar performance of one or both eyes due to misshapen refractive surfaces of the cornea or weak muscles around the eye. Success rates of current treatment options are inadequate, leaving millions of people with untreated or unimproved amblyopia. Much of this failure is due to a high rate of noncompliance to regimens of traditional techniques such as refractive adaptation with corrective lenses and occlusion therapy, possibly due to a lack of patient knowledge about the seriousness of the disorder and the critical nature of treatment. Other techniques such as LASIK surgery, strabismus surgery, and especially virtual reality therapy offer potential for treatment of amblyopia as well. Accordingly, a new multi-method paradigm that maximizes strengths and mitigates weaknesses of each technique and results in a high rate of compliance must be established. I propose a five stage program involving diagnosis and debriefing, refractive adaptation with corrective lenses, rigorous treatment with virtual reality therapy, surgical options and repeated attempt of treatment, and long term maintenance. Research must be conducted to establish the success of virtual reality therapy, and the efficacy of the multi-method paradigm. An improved treatment path would improve quality of life of numerous amblyopes.

3 TREATMENT OF UNILATERAL AMBLYOPIA 3 An Analysis of Treatment of Unilateral Amblyopia: A Multi-method Approach Amblyopia is commonly defined as poor vision due to abnormal visual experience in early life (Webber & Wood, 2005). The effects of amblyopia range in severity from reduced visual acuity (roughly 20/40 acuity) to legal blindness (less than 20/200 acuity) (Flom & Neumaier, 1966). Many people call amblyopia lazy eye, but this phrase is a bit misleading. The problem begins with the malfunction of the eye, but amblyopia is also a neurological disorder. Amblyopia is not the cause of visual malfunction in itself; it is the result of another disorder, such as anisometropia or strabisumus (Attebo et al., 1998). Chia et al. (2010) divides the disorder into two types; bilateral amblyopia and unilateral amblyopia. In bilateral amblyopia, both eyes malfunction, causing visual deficits (Chia et al., 2010). In unilateral amblyopia, one eye performs differently than the other eye, which causes two different visual signals to be sent to the brain. After a long period of time with these conflicting signals, the brain might begin to ignore input from one eye in order to make sense of the contradicting input (Medline Plus, Refractive errors, 2012). While both unilateral and bilateral amblyopia are serious disorders, I will only address unilateral amblyopia in this paper. For conciseness, I will refer to unilateral amblyopia simply as amblyopia. Many options are available for the treatment of amblyopia, such as traditional methods of prescribing glasses for refractive adaptation (Kivlin & Flynn, 1981) and occlusion therapy (Lee & Isenberg, 1981). Recent studies have found that other treatment options such as LASIK surgery (Autrata & Rehurek, 2004), strabismus surgery (Flax, 1993), and virtual reality therapy (Cleary, Moody, Buchanan, Stewart, & Dutton, 2009; Jeon, Maurer, & Lewis, 2012) could also be effective for treating amblyopia.

4 TREATMENT OF UNILATERAL AMBLYOPIA 4 Without regard for etiology, Flom and Neumaier (1966) estimated that 1.8 percent of Americans suffer from amblyopia. Recent investigations by Webber and Wood (2005) and Attebo et al. (1998) have claimed that the current rate of amblyopia is now around 3 percent, which means an estimate of a staggering 200 million people around the world have some degree of amblyopia (U.S Department of Commerce, 2012). Wellesley (1959) states that most sufferers from amblyopia are unaware of it until the strong eye deteriorates, causing the amblyope to become aware of his lack of acuity in the weak eye. Many of the estimated 200 million might not even realize they have a serious visual disorder. Thankfully, Amblyopia can be treated, especially if treatment begins early in the patient s life and quickly after onset of the corresponding disorder (Waddingham, Cobb, Eastgate, & Gregson, 2006; Wellesly 1959). However, the rate of diagnosis and successful treatment leaves something to be desired. Estimates of efficacy range from 75 percent to only 50 percent (Hiscox, Strong, Thompson, Minshull, & Woodruff, 1992; Leiba, Shimshoni, Oliver, Gottesman, & Levartovsky, 2000). For example, Kivlin and Flynn (1981) treated 67 anisometropic amblyopes with refraction correcting glasses, and found that 70 percent experienced improvements with visual acuity. While these results give hope for amblyopes and their families, the 30 percent who did not experience improvement still must be addressed. Many similar results have been found using different techniques such as occlusion therapy, or patching, with an improvement rate of 72 percent (Leiba et al., 2000). In addition to the unreliable success rate of most treatment options, many therapies that seemed to be a success initially did not create lasting improvement in the patient. In fact, Leiba, et al. (2000) followed up on the initial assessment of success 54 patients, and found that after an average of 6.4 years after the initial treatment ended, only 66.7 percent retained the initial

5 TREATMENT OF UNILATERAL AMBLYOPIA 5 improvement. The overall results are quite disappointing. Of the original 54 participants in this study, only 26 experienced lasting improvement. A mere 48 percent benefited from lasting results. Similar results were found when Hiscox et al. (1992) followed up on 368 occlusion therapy patients after an average of 31 months post-therapy. They discovered that the majority of subjects did experience some success, but 23 percent did not improve. Even though the treatment of amblyopia does produce a fair amount of success using traditional methods such as prescribing glasses and occlusion therapy, the overwhelming majority of studies find that at least a quarter of patients do not improve. Using the figure of 200 million amblyopes mentioned earlier, this still leaves almost 50 million people with unsuccessfully treated amblyopia (assuming that all 200 million were diagnosed with and treated for amblyopia, which is highly unlikely in itself). Gregson (2002) argues that part of the reason that current treatments are not effective is non-compliance. Current treatment paradigms simply do not work as well as they are intended to if they regimen is not strictly adhered to. The solution might be a standard paradigm for treatment that considers the strengths and weaknesses of many treatment options, as well as their compliance rates. Many techniques can be utilized due to the fact that different types and severities of amblyopia will require different treatment. A standard procedure that uses many techniques to their full potential and maintains a high compliance rate must be established for optimal treatment of amblyopia. As previously mentioned, the best paradigm for treating amblyopia is one that utilizes the strengths of all of these techniques while attempting to mitigate their weaknesses. This literature review will first describe in more detail the two main causes of and three severities of amblyopia, along with a brief review of each condition s effect on optimal treatment option. Then I will acknowledge the pros and cons of each form of treatment, and analyze and compare all of the

6 TREATMENT OF UNILATERAL AMBLYOPIA 6 major treatment options. After I have thoroughly explored each treatment option, I will explicate a multi-method approach to treating unilateral amblyopia. Finally, further research will be suggested that will provide more evidence for the effectiveness of this approach, and the broad implications of this new paradigm will be discussed. Etiology of Amblyopia and its Relevance to Treatment Options Amblyopia is caused by 2 main disorders; anisometropia and strabismus (Attebo et al., 1998). While the resulting amblyopia is essentially the same, the two different forms of amblyopia require slightly different forms of treatment. This is because the malfunction with anisometropia is with the cornea, and the malfunction with strabismus is with the muscles surrounding the eye (Medline Plus, Refractive errors, 2012; Medline Plus, Strabismus, 2012). Accordingly, refractive adaptation with glasses and LASIK surgery are more effective at treating anisometropic amblyopia because these methods aim to improve the refractive ability of the cornea (Stewart, Moseley, Fielder, & Stephens, 2004). Likewise, interventions such as strabismus surgery are more effective for treating strabismic amblyopia due to the fact that these methods address the ineffective eye muscles (Flax, 1993). I will propose treatment methods for each variation of amblyopia in my proposal of the multi-method approach. It should also be noted that anisometropia and strabismus can and frequently do co-occur (Attebo et al., 1998). This phenomenon will also be addressed after presentation of each disorder and summary of the treatment options. Anisometropia Anisometropia, also known as refractive error, is the most common cause of amblyopia. Attebo et al. (1998) found that about 50 percent of amblyopia is due to anisometropia alone. These errors are caused by irregular shape of the cornea, and are known as myopia

7 TREATMENT OF UNILATERAL AMBLYOPIA 7 (nearsightedness), hyperopia (farsightedness), presbyopia (farsightedness due to age), and astigmatism (inability of the eye to focus) (Medline Plus, Refractive Errors, 2012). A diagnosis of one of these disorders usually results in an optometrist prescribing glasses for the patient, but if the disorder occurs during a critical stage of development, or if the anisometropia is severe enough, the eyes will develop with different refractive strengths, commonly leading to amblyopia (Sireteanu & Fronius, 1981). Strabismus Attebo et al. (1998) also discovered that strabismus is the next most common cause of amblyopia. In strabismus, the error is with the muscles that control the eye rather than the shape of the cornea (Medline Plus, Strabismus 2012). Because the muscles do not work together as well as they are supposed to, the eyes gaze in different directions. This crossed-eyed gaze is what most people think of when they hear lazy eye. Like anisometropia, untreated strabismus can result in amblyopia (Medline Plus, Strabismus, 2012). Mixed Mixed amblyopia is simply amblyopia caused by both anisometropia and strabismus. Attebo et al. (1998) found that about 27 percent of amblyopia can be considered mixed amblyopia. Fortunately, treatment of amblyopia is no more complicated that treating both anisometropic amblyopia and strabismic amblyopia separately, although overall success rates are slightly lower (Stewart, Fielder, Stephen, & Moseley, 2005). Severity of Amblyopia and its Relevance to Treatment Options While the deficits of amblyopia vary greatly from patient to patient, the severity can generally be classified as mild, moderate, or severe. A simple classification system is based on visual acuity. Flom and Neumaier (1966) used the benchmarks of 20/40 acuity for mild

8 TREATMENT OF UNILATERAL AMBLYOPIA 8 amblyopia, and 20/200 for severe amblyopia (legal blindness), with moderate amblyopia falling somewhere in between. Stewart, Fielder et al. (2005) concluded that treatment outcomes are influenced by the severity of the amblyopia. Refractive adaptation worked best for mild amblyopia, and worse for more severe amblyopia (Stewart, Fielder, et al.). Conversely, occlusion therapy was more effective for treating severe amblyopia and less effective with mild amblyopia than refractive adaptation was (Stewart, Fielder, et al.). Surgical options should only be used for severe cases due to the invasiveness of these options. Virtual Reality therapy seems to work best in moderate cases, but improvement is seen in all levels of severity (Hess, Mansouri, & Thompson, (2010). It is also important to note that as severity of amblyopia increased, the overall success rate of treatment declined to about a 65 percent improvement rate for severe amblyopes (Stewart, Fielder, et al.). I will argue that due to levels of invasiveness and effectiveness, some treatment options are better suited for certain severities of amblyopia. Mild Amblyopia Treatment seems to be most effective with mild amblyopia. The overall success rate of the treatment of mild amblyopia is about 80 percent, and refractive adaptation and occlusion frequently provide improvement (Stewart, Fielder, et al. 2005). Due to the fact that simple, noninvasive interventions seem to have a generally positive effect, refractive adaptation and occlusion therapy should be implemented in mild cases. Moderate Amblyopia Generally, moderate amblyopia follows the same outcome pattern as mild amblyopia. Both severities see success in about 80 percent of patients, but occlusion therapy has a slightly higher likelihood of success than occlusion therapy does for moderate amblyopia (Stewart, Fielder et al., 2005). Accordingly, refractive adaptation and occlusion therapy are recommended.

9 TREATMENT OF UNILATERAL AMBLYOPIA 9 If these interventions do not improve function, virtual reality therapy might be used. Cases of amblyopia that fall on the border of moderate and severe might need more rigorous treatment, but the exact borderline of maximum treatment efficacy has not yet been established. Severe Amblyopia In the most severe cases of amblyopia, many treatments become less effective, especially refractive adaptation (Stewart, Fielder, et al., 2005). Other more rigorous or invasive treatment options must be assessed for treating severe cases. The options I will discuss include virtual reality therapy, LASIK surgery, and strabismus surgery. Analysis of Treatment Options As I have established, some treatment options are better suited for certain types of amblyopia. Each treatment option in itself has inherent pros and cons. Before I present recommended treatment paradigms for each subtype of amblyopia, I will summarize the five main treatment options. Treatment Options Refractive adaptation with corrective lenses. Corrective lenses are usually used in the initial attempt to correct anisometropia and amblyopia. Lenses can be custom made to compensate for refractive error in the weak eye. Both glasses and contact lenses are frequently used for refractive adaptation. Strengths of refractive adaptation with corrective lenses. Overall, refractive adaptation does achieve a fairly high success rate, especially among younger children and mild cases of amblyopia. (Kivlin & Flynn, 1981). Of all treatment options, prescribing glasses is far and away the least invasive. Kivlin and Flynn also concluded that

10 TREATMENT OF UNILATERAL AMBLYOPIA 10 refractive adaptation is an excellent maintenance method. Continuing treatment with glasses seems to prevent improvement from fading (Kivlin & Flynn). Weaknesses of refractive adaptation with corrective lenses. However, corrective lens therapy does fall short in some areas. This therapy requires a median of 8 months to be effective (Kivlin & Flynn, 1981). Many patients and their families are simply not patient enough to wait that long for improvement. In addition, 30 percent of patients do not improve with this treatment (Kivlin & Flynn, 1981). This problem is especially prevalent in patients with strabismic amblyopia, who only experience 60 percent as much improvement as patients with anisometropic amblyopia (Stewart, Fielder et al., 2004). Also, refractive adaptation alone does not effectively treat more severe cases of amblyopia (Stewart, Fielder et al.). These shortcomings prompt many therapists and families to seek alternative options. Occlusion therapy. Occlusion therapy seems to be the current standard for treating amblyopia. This technique, also known as patching, involves covering the strong, non-amblyopic eye, which forces the weaker eye to be used (Bhandari, Sharma, & Shrestha, 2012). The idea behind this treatment is to make the amblyopic eye practice seeing again without being dominated by the strong eye. Duration of patching varies due to age of the patient and severity of the amblyopia. Eventually, both eyes are meant to become roughly the same strength. Strengths of occlusion therapy. Stewart, Fielder et al. (2005) found that many patients who undergo occlusion therapy attain better visual acuity, with about 52 percent seeing significant improvement. This effect is especially pronounced in patients with strabismic amblyopia (Stewart, Fielder et al.). Like

11 TREATMENT OF UNILATERAL AMBLYOPIA 11 refractive adaptation, many cases if mild to moderate amblyopia can be treated using occlusion therapy (Stewart, Fielder et al.). Occlusion therapy is also fairly noninvasive. Weaknesses of occlusion therapy. Despite its potential benefits, Stewart, Fielder et al. (2005) address three substantial deficiencies of occlusion therapy; an age bias, lack of effectiveness with anisometropic amblyopia, and a very high noncompliance rate. Occlusion therapy works better for children, and is almost completely ineffective for adults. Anisometropic amblyopia also seems to be resistant to this treatment option. Arguably, the most important weakness of patching is the high noncompliance rate. Newsham (2000) defines noncompliance as following treatment for less than 80 percent of the prescribed time. Multiple studies have found that the noncompliance rate hovers somewhere around and abysmal 50 percent (Stewart, Fielder et al. 2005; Al-Zuhaibi et al., 2009). Bhandari et al. (2012) claims that this rate is so poor because the noncompliant patients do not understand the critical period of visual development, and are unaware of the importance of treatment. Other studies have noted that occlusion therapy causes relatively impermananent improvement. Bhola et al. (2006) and Hiscox et al. (1992) both found that about a quarter of treatments that were initially declared successful required repeated treatment at a later time, with recurrence rates of 27 percent and 23 percent, respectively. Without question, repeated treatment using a preciously inadequate technique is a hassle. A final, but crucial weakness is the lack of cooperation between the eyes. While the weak eye may improve, Gregson (2002) claims that occlusion therapy will never allow the eyes to work as an integrated system.

12 TREATMENT OF UNILATERAL AMBLYOPIA 12 Virtual reality therapy. In the past few years, virtual reality therapy has become a subject of interest for amblyopia researchers. These novel techniques might replace occlusion therapy as the new standard in amblyopia treatment. Many variations on virtual reality therapy are currently being explored, but one of the most promising systems is the Interactive Binocular Treatment (I- BiT ) system. With assistance from the Directorate of Ophthalmology at Queen s Medical Centre, the Virtual Reality Applications Research Team of the University of Nottingham developed a treatment that includes both eyes in the treatment process. In the I-BiT system, the amblyopic patient wears a set of goggles that projects video to each eye separately. Details can be presented to the weak eye alone, with causes the weak eye to learn to see again (Eastgate et al., 2006). Even more importantly, each eye is able to receive different signals and integrate them into a functional visual image, which allows for improvement of binocular cooperation (Eastgate et al.). Subjects were able to play interactive visual based games with the goggles, with key elements only presented to the amblyopic eye. Thus, the game required the use of both eyes for success (Eastgate et al.). For a more detailed summary of the I-Bit system and methodology, please reference Eastgate et al. Strengths of virtual reality therapy. Unlike occlusion therapy, which only treats one eye and creates a risk diplopia (Gregson, 2002; Wessels, 2011), virtual reality techniques treat both eyes at the same time, which improves the visual system s ability to integrate signals from each eye (Eastgate et al., 2006; Hess et al., 2010). Cleary, Moody, Buchanan, Stewart, and Dutton (2009) emphasize the importance of the sustained improvement. After completion of the therapy program, an impressive 60 percent of patients maintained their highest acuity score from the end of the treatment (Cleary et al.).

13 TREATMENT OF UNILATERAL AMBLYOPIA 13 Eastgate et al (2006) also states the adaptability of the program and the short duration of the treatment as advantages of the I-BiT system over occlusion therapy. The system is fully adjustable to provide appropriate treatment for people of all ages, genders, severity of amblyopia, etc (Eastgate et al). Even severe visual deficits can be treated with satisfying results (Waddingham et al., 2006). Surprisingly, many older people with amblyopia experience improvement with this program as well. While the effects are usually not as pronounced in older amblyopes as they are in younger amblyopes, elderly patients still show visual improvement, which is a remarkable demonstration of adult visual neuroplasticity (Hess et al., 2010; Cleary et al., 2009; Jeon et al., 2010). A final strength that must be considered is the high compliance rates for virtual reality therapy. While occlusion therapy takes 120 to 200 hours to complete, virtual reality therapy has produced noticeable improvement in less than two hours of treatment time over a span of 8 weeks (Cleary et al., 2009). This immediate positive feedback gives hope to the patient that the treatment will work, which greatly increases compliance rates (Hess et al., 2010). In addition, the system is actually enjoyable for patients. Instead of losing sight in one eye for hours on end or wearing glasses, the subject plays a video game instead (Cleary et al., 2009). Amblyopic patients, especially children will be much more likely to adhere to this regimen (Cleary et al.). Strong compliance rates will aid overall success for this treatment option. Weaknesses of virtual reality therapy. Virtual reality therapy has very few weaknesses. The largest is that this treatment option is still in its infancy. Many of the studies are pilot studies or small samples. More research is needed before declaring virtual reality therapy the standard amblyopia treatment, but all research points in that direction.

14 TREATMENT OF UNILATERAL AMBLYOPIA 14 LASIK surgery. Laser assisted in situ keratomileusis, more commonly known as LASIK, is an increasingly common procedure to correct anisometropia in all of its forms. In this procedure, a laser is used to cut and shape the cornea to provide a better refractive surface (U.S. Department of Health & Human Services, 2011). Another related procedure is laser assisted sub epithelial keratectomy, or LASEK (Autrata & Rehurek, 2004). For all intents and purposes, these procedures are the same. Strengths of LASIK surgery. LASIK surgery is very effective at correcting anisometropia and in turn, amblyopia. Autrata and Rehurek (2004) found that patients gained more visual acuity and bincocular coordination with the surgery than with corrective lenses. It should be noted that the surgery in itself did not improve amblyopia. After surgery or refractive adaptation, the patient was treated with occlusion therapy (Autrata & Rehurek). Thus, LASIK is a technique used to facilitate other treatments such as refractive adaptation or patching (Yin, Wang, Yu, Ren, & Chen, 2007). LASIK surgery is the best option for treating severe amblyopia after other interventions have failed. Weaknesses of LASIK surgery. While many people believe LASIK surgery is a risky option, the technique has been refined to be quite safe. LASIK surgery does have risk factors such as under- or over-correction, loss of acuity, or retinal detachment, complications arise is less than 1 percent of all procedures (Federal Trade Commission, 2008; Arevalo et al., This surgery is invasive, so it should only be used in other cases where treatment has failed. The Federal Trade Commission (2008)

15 TREATMENT OF UNILATERAL AMBLYOPIA 15 also warns that most insurance plans do not cover this treatment, so cost might be a prohibitive factor. Strabismus surgery. Like LASIK surgery is to anisometropia, Strabismus surgery is to strabismus. During this operation, the muscle groups around the eye are strengthened or weakened in a manner that will make the eyes converge properly (Flax, 1993).. Strengths of strabismus surgery. Unfortunately, this surgery has a functional cure rate of about 15 percent of amblyopic patients (Flax, 1993). This rate is low, but it is still a possible option when other treatments have failed. It seems that the most important benefit from this procedure is the chance of cosmetic cure. Flax found that 43 percent of strabismic amblyopes experienced a corrected gaze. Even if this cosmetic improvement does not increase functionality, the patient will still have higher selfesteem due to the correction of the sometimes prominent lazy eye (Flax). Cosmetic improvement of strabismus may lead to easier social development. Weaknesses of strabismus surgery. As I previously stated only 15 percent of amblyopes improve functionality. Unless the patient is desperate or other factors are influencing the decision, surgery might not be the best option due to its costliness, invasiveness, and effectiveness. The anesthetics commonly used in the surgery also pose a problem. Up to 23 % have nausea and vomiting after the procedure, sometimes severe enough to require hospitalization (Flax, 1993). A Multi-Method Paradigm for Treating Amblyopia Considering all of the aforementioned types of amblyopia and treatments, it is clear that a proper method must be established. The best method will use treatment options that provide the

16 TREATMENT OF UNILATERAL AMBLYOPIA 16 highest rate of success and compliance for the patient, considering each specific case of amblyopia. If at all possible, weakness of each treatment and unnecessary procedures ought to be avoided. My multi-method paradigm consists of 5 stages; diagnosis and debriefing, initial treatment attempt with corrective lenses, rigorous treatment with virtual reality therapy, surgical options and repeated attempt of treatment, and long term maintenance. These steps will comprise what I believe is the most effective paradigm for treating unilateral amblyopia. Diagnosis and Debriefing The first step of the process is to diagnose the type and severity of amblyopia. Once these details are known, the treatment schedule can be adjusted to maximize the chances of improving visual acuity. Next, the patient (and his or her family if the patient is a minor) will be presented with each treatment option, and why it is important to adhere to the intervention. This stage is meant to give the patient (and the family) a thorough understanding of the critical period of visual development, and why strictly following the regimen is vital to the improvement of amblyopia. Hopefully, a better understanding of amblyopia and its treatment will create a higher compliance rate, which will lead to more successful outcomes (Bhandari et al., 2012; Stewart, Fielder et al., 2005). Initial Treatment Attempt with Corrective Lenses After the initial diagnosis and debriefing, all patients will start treatment with refractive adaptation. Due to the fact that refractive adaptation with glasses or contact lenses is usually effective for both anisometropic amblyopia and strabismic amblyopia (albeit less so), every patient will start with a brief or extended course of treatment (which depends on severity, age, and a number of other factors). Frequently, mild amblyopia will be greatly improved at this state, as long as the patient is compliant with the procedure (Stewart, Fielder, et al. 2005). Even if the

17 TREATMENT OF UNILATERAL AMBLYOPIA 17 mild amblyopia does not reach a satisfactory level of improvement or if the amblyopia is more severe, this stage is still beneficial if small improvements are made. This will facilitate the success of more rigorous treatment (in the same manner that improvements from LASIK surgery facilitate success of other treatments in Yin et al. (2007)). If sufficient improvement is reached, patients should skip ahead to the long term maintenance stage to ensure that the improvements hold over time. If more work needs to be done, the patient continues to the rigorous treatment with virtual reality stage. Rigorous Treatment with Virtual Reality Therapy This stage is most likely the most controversial. Based on all the previous studies, I must argue that occlusion therapy be stopped in favor of virtual reality therapy. However, occlusion therapy may still be used if all other treatment options fail. As concisely as I am able to express, virtual reality should be chosen over occlusion therapy because occlusion therapy has no advantage that virtual reality has, and virtual reality therapy is a binocular treatment with a much higher compliance rate than occlusion therapy (Cleary et al., 2009; Stewart, Fielder et al. 2005; Al-Zuhaibi et al., 2009). Treatment in this stage will become more aggressive. While individual virtual reality systems may vary, the I-BiT system of Eastgate et al. (2006) is a good place to start. The ability to tailor all aspects of the treatment presentation to each individual subject will provide the best likelihood of compliance and visual improvement. Mild to moderate cases should have good success, and severe cases should have decent success rates as well. In addition, anisometropic and strabismic amblyopia should both see improvement from this technique. Patients who had success at this stage will begin long term maintenance, while cases without improvement will begin discussing the surgical options stage.

18 TREATMENT OF UNILATERAL AMBLYOPIA 18 Surgical Options and Repeated Attempt of Treatment If all other options do not produce improvement, LASIK or strabismus surgery becomes an option. If both the patient (and family, if applicable) and therapist agree that surgery should be performed to correct vision, anisometropic and strabismic amblyopes will undergo their respective surgery. After the recovery from surgery, the patient will again be assessed for visual acuity. If the amblyopia has finally been ameliorated, long term maintenance can begin. If results are still unsatisfactory, the treatment regimen is repeated starting with the refractive adaptation phase until the condition is improved. Long Term Maintenance Once the amblyopia has successfully been treated, a preventative maintenance schedule will be established. This will likely be intermittent treatment with corrective lenses, or brief virtual reality sessions. Long term follow up is essential to ensure that improved vision is maintained. Future Research and Conclusions The effectiveness of virtual reality therapy must be researched more extensively. While the current data provides great hope for the future of amblyopia treatment, the data pool is relatively small. Much more extensive and controlled experimental research must be performed before we are able to conclude that virtual reality therapy is a plausible treatment option. Furthermore, the multi-method paradigm that I have presented must be evaluated in its entirety. The success and compliance rates of the overall program must be compared to the success and compliance rates of individual treatments alone using data from controlled

19 TREATMENT OF UNILATERAL AMBLYOPIA 19 experimental studies. This research will either confirm or deny the multi-method approach as an effective treatment paradigm. If the multi-method paradigm is more successful that current research options, practitioners ought to adopt it as the standard method for treating amblyopia. An improvement of success rate by only 1 percent could mean improvement for hundreds of thousands of people who would not have had success with current methods. Research must be done to discover if this paradigm is worthy of being the standard treatment method because the potential benefits of an improved system would improve the vision and quality of life of countless amblyopes.

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