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 Table of Contents  
ORIGINAL ARTICLE
Year : 2018  |  Volume : 111  |  Issue : 2  |  Page : 76-81

A pilot randomized trial evaluating overminus spectacles versus part-time occlusion for control of intermittent exotropia among children 2–10 years of age


Ophthalmology department, Ain Shams university, Cairo, Egypt

Date of Submission30-Dec-2017
Date of Acceptance03-Feb-2018
Date of Web Publication30-Aug-2018

Correspondence Address:
Merna G Abdelfatah
10th Abu bakr el sediq street, heliopolis, Cairo, 11384
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ejos.ejos_8_18

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  Abstract 

Purpose The aim was to compare the short-term effectiveness of overminus spectacles versus part-time occlusion (PTO) in improving control of intermittent exotropia [X(T)].
Patients and methods A total of 60 children with X(T), from 2 to 10 years of age, were included in the study. Their distance office control score started from 2 or worse. This is a clinical, randomized, prospective, pilot study. Children were randomly assigned to overminus spectacles, PTO therapy, and observation for 4 months followed by 2 months without treatment.
Results The mean distance exotropia control score after 4 months of treatment improved significantly in the overminus spectacle and the PTO groups from 3.9 vs. 3.9 to 2.0 vs. 2.7, respectively. After stoppage of treatment for 2 months, the score deteriorated significantly to 3.3 and 3, respectively. The observation group’s score showed nonsignificant change all throughout the study period. There was a significant improvement in both mean near and distance angles only in the overminus spectacle group after 4 months of treatment and a significant deterioration after 2 months without treatment. Both near and distance angles showed nonsignificant change in both PTO and observation groups all throughout the study period. There was also a significant correlation between the poor compliance of the patients and their deterioration in the PTO group.
Conclusion Overminus spectacle therapy has proved to be more effective in control of X(T) than PTO therapy. Poor compliance in PTO therapy affects the treatment effectiveness. It is suggested to work on a protocol of treatment cessation in further studies.

Keywords: intermittent exotropia, overcorrecting minus spectacles, part-time occlusion


How to cite this article:
Abdelfatah MG, Mahmoud AT, Salman AG, Elsebaay ME. A pilot randomized trial evaluating overminus spectacles versus part-time occlusion for control of intermittent exotropia among children 2–10 years of age. J Egypt Ophthalmol Soc 2018;111:76-81

How to cite this URL:
Abdelfatah MG, Mahmoud AT, Salman AG, Elsebaay ME. A pilot randomized trial evaluating overminus spectacles versus part-time occlusion for control of intermittent exotropia among children 2–10 years of age. J Egypt Ophthalmol Soc [serial online] 2018 [cited 2018 Sep 21];111:76-81. Available from: http://www.jeos.eg.net/text.asp?2018/111/2/76/240128


  Introduction Top


Intermittent exotropia [X(T)] is the most common type of exodeviation in children [1],[2]. It is an exophoria (X) that intermittently breaks down to a constant exotropia (XT) of one or both eyes, mostly for distance at times of fatigue or inattention [3]. Approximately 80% of patients with X(T) will show progressive loss of fusional control and an increase in the X(T) over several months to years [4].

Although X(T) is a common condition, there is still a debate about the efficacy and timing of different treatment options whether surgical or nonsurgical, particularly for young children who are not cooperative for accurate measurements [5],[6]. Nonsurgical treatment options such as overminus spectacles or occlusion are used as a primary or a temporary treatment to delay progression of X(T) or to improve the sensory outcome after surgery [7].

Overminus spectacles are additional minus power over the cycloplegic refraction, prescribed full time with eventual weaning to a point at which the X(T) is well controlled in the regular refractive correction [6],[7],[8]. They work by stimulating the accommodative convergence and thus facilitating fusion [9],[10],[11].

It has been also reported that part-time occlusion (PTO) therapy has potential benefits in preservation of the binocularity and reduction in the frequency or magnitude of the exodeviation [12],[13].


  Patients and methods Top


The study was carried out in the Ophthalmology Department, Ain Shams University, according to the tenets of the Declaration of Helsinki. The protocol was approved by the Ophthalmology Department and Ethical Committee, Ain Shams University. Informed consents were also given by the parents.

The study included children from 2 to 10 years with best-corrected visual acuity not less than 20/100 and X(T) meeting the following criteria: (a) distance angle at least 20 prism diopters (PD) measured by prism alternate cover test for cooperative children or by Krimisky test for uncooperative children; (b) near deviation should not exceed the distance deviation by greater than 10 PD; (c) prior treatment for X(T) was not permitted preceding enrollment; and (d) normal neurological status. Patients with convergence insufficiency X(T), significant anisometropic amblyopia more than 4 D, and significant vertical deviations or patterns were excluded from our study.

At the enrollment visit, control of the exodeviation was assessed at distance (6 m) and near (1/3 m) using the office control score, which ranges from 0 (X, best control) to 5 (XT, worst control). After an initial control assessment, the magnitude of exodeviation was assessed at distance (6 m) whenever possible and near (1/3 m). Photographs were taken whenever possible after the consent of the parents. Monocular distance best-corrected visual acuity was measured using Snellen acuity chart for cooperative children, and for younger children, visual acuity(VA) was assessed by noticing the monocular fixation to objects. In addition to the clinical testing, the participant’s parents were consulted about the treatment regimen and were instructed to observe the home control of the X(T). All the clinical assessment and prism alternate cover test were performed by study-certified masked pediatric ophthalmologists.

Patients were randomly assigned using a permuted block design stratified by mean distance control score with equal probability to overminus spectacles, PTO, and observation groups. The test results were statistically analyzed to assess the effectiveness of the two treatment modalities versus observation on X(T).

The 20 participants who were assigned to the overminus spectacle group were all prescribed spectacles with fixed −3.00 D added to the sphere power of the cycloplegic refraction, which was for all the waking hours for the whole 4 months, and no other X(T) treatments were allowed during this time. The cylindrical values were prescribed without changing.

The power of the spectacles was fixed during the 4 months of treatment and then stopped for 2 months with prescription only of nonoverminus refraction correction if needed.

The treatment regimen for PTO was to cover the eyes alternately for 4 h daily whether continuous or separated for 4 months and guaranteed that the patches were completely closing the eyes so that the children could not see through them.

Participants who were assigned to the observation group received no treatment other than nonoverminus refractive correction if needed.

Patients were followed-up at the first month, third month, and fourth month, and then after stop of treatment at the sixth month. In each visit, we assessed the fusional control using the Office Control Score and the near and far angles of deviation with and without glasses. At each visit, the clinical assessment was performed by a masked examiner.

Compliance was assessed for participants in the PTO and overminus spectacle groups at each follow-up visit. It was judged to be excellent (>75%), good (51–75%), fair (26–50%), or poor (25%) based on discussions with the parent and by reviewing study calendars on which parents recorded the overall number of hours the child patched or wore the glasses.

For the PTO group, the child was supposed to cover the eye for 4 h daily, thus, around 480 h in the 4 months. Any of the parents was asked to the write down the hours of PTO each day, so we could calculate the percentage and thus judge the child compliance.


  Results Top


Between October 2016 and June 2017, 60 children with X(T) were included in our study. Overall, 55% (33/60) were females and 45% (27/60) were males, and 48.3% (29/60) were myopic and 51.7% (31/60) were hypermetropic. Moreover, 55% (33/60) of them were younger than 5 years. The demographic statistics are summarized in [Table 1]. Most patients (66.66%, 40/60) had basic type X(T) and the minority (33.33%, 20/60) had divergence excess X(T).
Table 1 Demographic data and mean values of the patients in the study

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Of the 60 participants, 91.6% (55/60) of all the participants completed until their fourth month follow-up visit. Among them were all the patients in the observation and overminus spectacle groups whereas 75% (15/20) of the patients in the PTO group.

The sixth-month follow-up after treatment stoppage was completed by 78.3% (47/60). Among them were 70% (14/20) of the patients in the observation group, 90% (18/20) of the patients in the overminus spectacle group, and 75% (15/20) of the patients in the PTO group.

Sixteen of the 20 (80%) patients in the overminus spectacle group were judged to have good compliance, whereas 27% (4/15) in the PTO therapy group were judged to have good compliance. The P value was significant in both groups (P=0.002) as shown in [Table 2] and [Figure 1].
Table 2 Compliance of patients in both treatment modalities (overminus spectacle vs. part-time occlusion groups)

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Figure 1 Comparison between compliance of patients with overminus spectacle therapy and part-time occlusion therapy.

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Improvement according to Office Control Score was defined as 1-point improvement in the distance control score, whereas significant improvement was defined as 2 or more points improvement. After 4 months of treatment, 90% (18/20) of the patients in the overminus spectacle group showed improvement in their control score; 30% (6/20) had one line of improvement, 60% (12/20) of them showed significant improvement, 5% (1/20) showed deterioration, and 5% (1/20) showed no change in their score. At the sixth-month follow-up after stoppage of the overminus spectacles, 88.8% (16/18) of the patients showed deterioration in their control score, whereas 11% (2/18) remained with the same score, but no one showed improvement in the control score after removal of the overminus spectacles.

At the fourth-month follow-up, 74% (11/15) in the PTO group showed improvement; among them, 33% (5/15) showed significant improvement, 20% (3/15) had the same score before and after treatment, and 6% (1/15) showed deterioration. After 2 months with no PTO therapy, 46.6% (7/15) of the patients showed deterioration in their control score. Among them, 28.5% (2/7) of them showed poor compliance, 28.5% (2/7) showed fair compliance, and 42.8% (3/7) showed good compliance to the PTO therapy. Moreover, 53.4% (8/15) of patients in the PTO group did not show any change in their control score at the sixth-month visit. Among them, 50% (4/8) showed bad compliance to the treatment and showed no improvement in the fourth month nor in the sixth month, 37.5% (3/8) showed fair compliance, and only one showed good compliance to the PTO therapy.

In the observation group, 20% (4/20) of the patients showed deterioration in their control score in the fourth month visit, 45% (9/20) of the patients did not show any deterioration, and 35% (7/20) of them showed improvement in their score. It was noticed that most of the children who improved in the observation group were prescribed minus glasses only for their refractive error. Moreover, 92.8% (13/14) showed the same control score at the sixth month follow-up, and only one patient showed deterioration in the control score at the sixth month.

The mean distance exotropia control score after 4 months of treatment improved significantly in the overminus spectacle and the PTO groups to 2.0 and 2.68, respectively, whereas at the sixth month visit after the treatment was stopped for 2 months, deteriorated significantly to 3.3 and 3, respectively. The observation group’s score showed nonsignificant change all throughout the study period as shown in [Figure 2] and [Table 3].
Figure 2 Comparison between office control score in the three groups before treatment, in the fourth month, and in the sixth month.

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Table 3 Comparison between Office Control Score in the three groups before treatment, in the fourth month, and in the sixth month

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There was a significant improvement in both mean near and distance angles only in the overminus spectacle group after 4 months of treatment from 22.7 to 9 PD for near and 39 to 25.1 PD for far. At the sixth month after 2 months without treatment, there was a significant deterioration to 19.4 PD for near and 37.7 PD for far in the overminus group. Both near and distance angles did not show a significant change in both PTO and observation group all throughout the study period as shown in [Figure 3] and [Figure 4].
Figure 3 Comparison between the mean near angle (pretreatment, at the fourth month, and at the sixth-month follow-up) among the three groups.

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Figure 4 Comparison between the mean distance angle (pretreatment, at the fourth month, and at the sixth-month follow-up) among the three groups.

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When we further studied the compliance of the patients who did not improve in the PTO group after 4 months of treatment, it showed a significant correlation between the poor compliance of the patients and their deterioration as shown in [Table 4].
Table 4 Correlation between compliance of the patients in overminus spectacle and part-time occlusion groups and their control score

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When we further studied the measured angle, which represented the quantitative improvement, and office control score, which represented the qualitative improvement, it showed a significant correlation between the angle and the score improvement.


  Discussion Top


Although nonsurgical treatment for X(T) is still debatable. It has been reported that approximately 4–16% of patients improve spontaneously with observation through the course of time [14],[15]. Other clinical investigators have reported a range of 23–75% increase in the angle of deviation through a 5-year period of follow-up [14],[16]. Lee et al. [17] reported that surgery for deterioration of angle of deviation to 20 PD or greater is the final destination of almost half of patients with small exodeviation. Rowe et al. [10] recommended overminus lens treatment as a primary treatment option for X(T). After a comprehensive and systemic review of the literature, we found no previous prospective randomized trials comparing overminus spectacles and PTO therapy with observation in children with X(T) in one study. There were also no previous studies that assessed the effect of withdrawal of overminus spectacles for 2 months after 4 months of treatment on the control of X(T). Mohney et al. [18] assessed the control of exodeviation at the sixth month after cessation of PTO therapy for 1 month following a 5-month treatment period with PTO.

The deterioration in the control score after 4 months of treatment in our study occurred in 6% of the participants in the PTO group whereas 46% deteriorated in the sixth month visit after 2 months with no treatment. In comparison with our study, the rate of deterioration according to Mohney et al. [18], 6 months after PTO therapy, was 2.2% in 90 patients from 12 to 35 months of age and in the study by Cotter et al. [6] was only 0.6% in 159 patients from 3 to 10 years of age. Most patients in the previously mentioned studies [6],[18] showed excellent or good compliance, which was inconsistent with our study.

The mean distance and near angles in the PTO therapy group did not show significant improvement at the fourth month nor deterioration at the sixth month. In comparison with our study, Alkhamous and AlSaleh [13] proved that PTO therapy can improve the deviation control but does not improve nor worsen the angle of deviation. However, the assessment methods were different. Mohney et al. [18] noticed also no improvement in the angle of deviation despite improvement in the control and thus proved that there was not sufficient evidence to prescribe PTO for X(T). In the overminus spectacle group, 5% of patients deteriorated in their score whereas 90% showed improvement at the fourth month of treatment. At the sixth month follow-up after stoppage the overminus spectacles, 88.8% of the patients deteriorated in their control score, whereas 11% remain with the same score, but no one showed improvement in the control score after removal the overminus spectacles. There was also a significant improvement in the angle for near and far in the overminus spectacle group at the fourth-month follow-up and a significant deterioration in the sixth-month visit after cessation of treatment. Previous studies of the overminus spectacle therapy showed variable results and different assessment criteria [10],[11],[19]. Rowe et al. [10] results were based on New Castle Control Score system (NCCS) and showed a 51% improvement rate in 21 patients after 5 years of follow-up which was longer than the treatment duration in our study and that may explain the lower percentage of improvement in his study than ours. Watts et al. [20] reported a 70.8% success rate in 24 patients from 2 to 17 years within 4 months of treatment, which was same as the treatment period in our study, with the use of NCCS to assess the control of X(T). Huseyin et al. [21] retrospective study showed 84% improvement in 19 patients with overminus spectacle therapy. However, with the use of NCCS and Jampolsky’s assessment criteria in a median of 18 months, the study by Chen et al. [19] showed improvement in the score more than 1 in 59% of participants, which is almost similar to our study, as among the 90% who improved were 60% who showed significant improvement. We both used the same control score to assess the patients, although the study duration was 8 weeks [19].

The small sample, the pilot design, and the study duration are the most important limitations in our study. On the contrary, it has a number of strength points. First, we assessed the success of treatment after 2 months of withdrawal. Second, we compared the two treatment modalities, overminus spectacles and PTO therapy, in one study. We suggest working on a protocol of treatment and treatment cessation in further studies with larger sample size and longer study duration.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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AlKhamous LS, AlSaleh AA. Does occlusion therapy improve control in intermitent exotropia? SJOPT 2016; 433:1–4.  Back to cited text no. 13
    
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Berg PH, Isenberg SJ. Treatment of unilateral exotropia by part-time occlusion. Am Orthopt J 1991; 41:72–76.  Back to cited text no. 14
    
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Berg PH, Lozano MJ, Isenberg SJ. Long-term results of parttime occlusion for intermittent exotropia. Am Orthopt J 1998; 48:85–89.  Back to cited text no. 15
    
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Lee BJ, Kim SJ, Yu YS. The clinical course of intermittent exotropia with small initial deviation. J Pediatr Ophthalmol Strabismus 2015; 52:206–212.  Back to cited text no. 17
    
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Pediatric Eye Disease Investigator, Mohney BG, Cotter SA, Chandler DL, Holmes JM et al. A randomized trial comparing part-time patching with observation for intermittent exotropia in children 12 to 35 months of age. Ophthalmology 2015; 122:1718–1725.  Back to cited text no. 18
    
19.
Pediatric Eye Disease Investigator, Chen AM, Holmes JM, Chandler DL, Patel RA, Gray ME et al. A randomized trial evaluating short-term effectiveness of overminus lenses in children 3 to 6 years of age with intermittent exotropia. Ophthalmology 2016; 123:2127–2136.  Back to cited text no. 19
    
20.
Watts P, Tippings E, Al-Madfai H. Intermittent exotropia, overcorrecting minus lenses, and the Newcastle scoring system. JAAPOS 2005; 9:460–464.  Back to cited text no. 20
    
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Huseyin B, Ayse GY, Unsal S, Remzi K. Overcorrecting minus lens therapy in patients with intermittent exotropia. Int Ophthalmol 2016; 36:1–6.  Back to cited text no. 21
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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