Paste yTREATMENT OPTIONS FOR CONVERGENCE INSUFFICIENCY
In the evaluation of challenges faced during reading and their causes, Convergence Insufficiency (CI) should be among the significant diagnoses. This condition occurs when an individual is unable to smoothly and efficiently converge their eyes as an object is moved nearer to their area of vision. It is also characterized by an individual’s inability to maintain clear view when the object of visual interest is in proximity. In this case, the patient’s eyes lack proper binocular alignment resulting in intermittent exotropia or exophoria where the patient experiences binocular diplopia. This ineffective and involuntary muscular action causes muscular discomfort and depending on the severity of the distress, the extent of its symptoms ranges from mild to severe. These symptoms include headaches after short reading periods, difficulty in reading or concentrating, movement of letters while studying, diplopia, a sensation of eyes pulling together, and blurred vision. The symptoms can be worsened by other factors such as by the patient’s stress, insomnia or other illnesses. Some patients will however not experience any of these symptoms due to either their high tolerance for discomfort, avoidance of carrying out tasks that are near visual, suppression or blocking of one eye during reading.
Convergence Insufficiency exists in about 3 to 5% of the population. Higher cases are reported in children of ages 6 to 18 years with a prevalence of 5.3%. Children aged between 8 and 12 years have a prevalence of about 6% while 7.7% is reported in university students. Presbyopic adults may have even higher incidence due to poor accommodative convergence. Their cases, however, might better be treated with base-in prism reading glasses. (Phillips, 2017).
There have been several convergence insufficiency treatments brought forward which consist of two categories; passive treatment which includes reading glasses with base-in prism and active treatment which entails vision therapies. These medications have been controversial in optometric and ophthalmic fields. There is yet to be an agreed-upon treatment method that is effective and beneficial especially in vision therapy. This lack of consensus might be mainly due to the limited scientific research that was done to compare these treatments. However, in the recent past, several scientific studies have been carried out, and treatments for symptomatic convergence insufficiency such as office-based placebo therapy (OBPT, office-based vergence/accommodative therapy (OBVAT) and home-based pencil push-ups (HBPP), have been compared.
Base-in prism reading glasses as a method of treatment have been found to have little scientific evidence proving their efficiency in improving convergence insufficiency symptoms in children of ages nine to seventeen years. However, a Convergence Insufficiency Treatment Trial Study Group (CITT) found prism reading glasses method to work better than placebo reading glasses although both treatment methods were found to have no significant effect on positive fusional convergence at near or near the point of convergence. The limitation of this study, however, was the follow-up period was only for six weeks. However, the base-in prism glasses proved to be operative in adults of forty-five to sixty-eight years as they decreased the signs of convergence insufficiency. The drawback of the study is that the prism used is not commercially available. It is unclear since it does not have a control group; whether the prism induced subjects adapted to the prism or some asthenopia at a distance. Base-in prism glasses though readily available and cost-effective are found to work better for adults than children in that they reduce symptoms of the condition in this group. The glasses have little or no benefit to children of ages 9 to 17 years.
Many studies in both ophthalmic and optometric fields have shown that vision therapy improves positive fusional vergence (PFV) at near therefore developing better control of binocular deviation. The two main vision therapies are HBPP and OBVAT that sometimes includes home reinforcement. Vision therapies have been found successful as they improve convergence function in both children and adults and remove asthenopia. HBPP therapy is one of the most popular treatments for convergence insufficiency and has been in use for the longest time. In this treatment, the patient is asked to look at the tip of a pencil and maintain visual contact as the tip is moved from distance to the subject’s nose. However, it is argued that targets with fine detail such pictures and letters should be used instead to accommodate fusional convergence. Due to this belief, most pencil push-up tests use the letters on the pencil to ensure the visual contact is with a fixed position. In January 2009, data were collected from sixteen patients diagnosed with convergence insufficiency. Their duration of symptoms, the near and distant deviation angles, refractive error and near the point of convergence was measured before the HBPP therapy and after 12 weeks of therapy. The results found that the treatment was effective in that the mean deviation angles significantly decreased both at distant and near and the near point of convergence significantly reduced from 36.3 centimeters to 14.4 centimeters. This home-based therapy has been considered an initial training method that has satisfactory results. It is found to be simple and cost-effective and recommended by both ophthalmologists and optometrists. The therapy is however successful if the patient does it correctly. Most patients tire quickly from the exercise, get bored or suppress an eye hence pencil push-ups may sometimes not work well. However, the treatment is far better than base-in prisms. (Kim & Chun, 2011)
Office-based placebo therapy is a simulation of the office-based vergence/accommodative therapy that is carried out without stimulating vergence or accommodation beyond the levels that are experienced in daily visual activities. In a pilot program, the CITT Group recently came up with a placebo therapy program appearing as OBVAT. The pilot project was used in a clinical trial of subjects aged between 9 and 30 years randomized in the office-based treatment programs. The placebo program was found to maintain masking in 61 patients effectively. After the program, 83% of the subjects were confident they were in the group receiving real therapy. This showed that qualified therapists that are well trained could deliver positive reinforcement and encouragement in therapy whether placebo or real and that patients’ perception on whether the treatment was real or not does significantly affect the level of confidence in the treatment, placebo or real. Hence office-based placebo therapy is effective at masking patients and can, therefore, be used in clinical trials with vergence/accommodative therapy. (Kulp et al., 2009)
Office-based vergence/accommodative therapy entail a specific course of visual therapy that is undertaken by a vision therapist and his or her patient in 12 weeks with fifteen minutes of home therapy and sixty minutes of in-office therapy. Home-based therapies often accompany these therapies. The office sessions of the therapy are divided into 3 phases with each phase of therapy taking approximately four weeks. Each phase is categorized into classes such as vergence, accommodation and gross convergence. The therapy processes are organized from the easiest to the most difficult in each phase. At the end of every phase, some endpoints act as guidelines to what the subject is estimated to achieve at the end of each phase before progressing to the next. OBVAT has proved to be more beneficial and effective especially in children than HBPP and OBPT. This treatment, coupled with home reinforcement, was found to have successful outcomes in 73% of its subjects after 12 weeks of therapy in a CITT Study that included 221children of ages between 9 and 17 years. The study was published in the Archives of Ophthalmology in the October 2008 issue and led by Mitchell S. Scheiman. The study proposed that practitioners change their treatments from prism lenses and pencil push-up therapy to office-based vision therapy as its outcomes were far more significant than any other treatment. (Kulp et al., 2009)
In 2015, a study was carried out at Zehedan University of Medical Sciences with the aim of comparing the effectiveness of the two major practical vision therapies, HBPP and OBVAT. Sixty students with convergence insufficiency were selected for the study and their refractive error, positive fusional vergence at near and the near point of convergence measurements taken. The students were divided into two groups with one receiving HBPP three times per day with each session being five minutes long while the other group received OBVAT for two times every week with every session lasting sixty minutes. The office-based therapy was not supplemented with any home-based therapies. After eight weeks of treatment, both types of therapies were found to have positive outcomes from the subjects. Office-based therapy was however found to have a more efficient nature. The limitations of the OBVAT treatment, however, was that it was too expensive and most likely not practical or locally available for patients. The home-based alternative was found to be more cost-effective and easily available (Momeni-Moghaddam, Kundart, Azimi, & Hassanyani, 2015)
In conclusion, it is evident from research and studies was done that there are several ways of treating convergence insufficiency. Past and ongoing research has enabled comparison of these treatment methods and clarified their different levels of efficacy. Current research also promises discovery of potentially better interventions like home-based computer programs. With the available options as of now, office-based therapy has come more recommended than any other method due to its efficacy in improving convergence insufficiency parameters and reducing its symptoms. Despite these incredible aspects of the treatment, most eye care practitioners have opted for pencil push-ups as their popular treatment method. Why is this? The likely explanation is that the pencil push-up treatment is affordable, easily accessible and very simple to administer. Office-based therapy on the other hand requires commitment in terms of time and financial resources that drives most patients to choose home-based pencil push-ups.
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