Downloaded from http://bjo.bmj.com/ on May 25, 2015 - Published by group.bmj.com
Clinical science
The impact of intermittent exotropia and surgery for intermittent exotropia on myopic progression among early school-aged children with myopia Kwang Hoon Shin, Sang Hun Hyun, Iris Naheah Kim, Hae Jung Paik Department of Ophthalmology, Gachon University Gil Hospital, Incheon, Republic of Korea Correspondence to Dr Hae Jung Paik, Department of Ophthalmology, Gachon University Gil Hospital, 1198, Guwol-dong, Namdong-gu, Incheon 405-760, Republic of Korea; [email protected] Received 12 December 2013 Revised 11 February 2014 Accepted 29 March 2014 Published Online First 29 April 2014
ABSTRACT Aim To investigate the relationship between myopic progression and intermittent exotropia, and the impact of surgery for exotropia on myopic progression in early school-aged children (from 7 years to 12 years of age). Methods Medical records of early school-aged patients with myopia were reviewed. Patients were divided into three groups; (A) Patients with intermittent exotropia and myopia at presentation and who underwent bilateral lateral rectus muscle recession for exotropia when 7–12 years old; (B) Patients with intermittent exotropia and myopia at presentation and who were merely observed for exotropia; and (C) Patients with myopia and straight ocular alignment. Main outcome measurements were the simple rate of myopic progression per year, the preoperative and postoperative rates of refractive growth with regards to the logarithmic age model in Group A, and the rate of high myopia development at the end of the early school period. Results The rates of myopic progression were −0.43 ±0.14 dioptre (D) per year in Group A, −0.49 ±0.17 D/year in Group B and −0.42±0.24 D/year in Group C. There was no significant difference in the rate of myopic progression among three groups. There was no significant intergroup difference in the preoperative and postoperative rates of refractive growth in Group A. There were no significant intergroup differences in the rates of high myopia development among three groups. Conclusions Whether patients with intermittent exotropia underwent surgical correction for intermittent exotropia did not influence the rate of myopic progression. There was no significant difference in the rate of myopic progression between patients with accompanying intermittent exotropia and myopia and those with myopia alone.
INTRODUCTION
To cite: Shin KH, Hyun SH, Kim IN, et al. Br J Ophthalmol 2014;98: 1250–1254. 1250
A presumption of the influence of intermittent exotropia on the development and progression of myopia has been continuously presented. Increased accommodative demand has been presented as a potential explanation for the association between intermittent exotropia and myopia in patients with intermittent exotropia.1 When describing the mechanism of myopia progression, increase in global axial length and associated myopic progression is assumed to be induced as an effort to decrease accommodation against excessive increase of accommodative demand.2 3 Horwood and Riddell4 suggested that the increased vergence necessary to control the exodeviation brings along overaccommodation in patients with intermittent distant exotropia. Theoretically, the effort to control ocular
alignment in intermittent exotropia can influence the progression of myopia through increase of accommodative demand. Ekdawi et al5 reported that intermittent exotropia was related with the development of myopia in their population-based study. The association between esotropia and hyperopia or anisometropia has been firmly established.6– 8 However, the association of intermittent exotropia with myopia has not been established as well, and not even has been studied rigorously. Myopia is the important public health issue nowadays. It was even referred to as one of the five immediate priorities for the Vision 2020 initiative of WHO.9–11 High prevalence of myopia has been demonstrated well, especially in East Asia.12–18 An awareness of the increasing prevalence of myopia has also been demonstrated in the USA.19 20 Myopia progression has been suggested to cease at 15–16 years of age.21 22 According to the growth function for myopia (Gompertz function) to estimate the age and the amount of myopia at stabilisation proposed recently by the Correction Of Myopia Evaluation Trial Group, myopia was estimated to be stabilised at 15.61 years of age.23 Also from the perspective of ocular biometric measurements, enlargement of globe size is usually completed by approximately 13 years of age.24 Since the natural refractive growth, which shows a tendency towards myopic shift, follows the logarithmic model with regards to the child’s age,25 the extent of refractive change decreases with advancing years. Even in childhood age, younger children show a greater change in refractive error status and axial length of globe when compared with older teenagers.26–28 Moreover, early onset of myopia is associated with high myopia in adults.29 The early school period is an important period in the development and progression of myopia. On the basis of the theoretical association between intermittent exotropia and myopia mentioned above, we hypothesise that intermittent exotropia might influence the myopic progression and that surgery for intermittent exotropia might reduce the rate of myopic progression when compared with those with intermittent exotropia who had no surgery. The aim of this study was to investigate the relationship between myopic progression and intermittent exotropia, and the impact of surgery for exotropia on myopic progression in early schoolaged children (from 7 years to 12 years of age).
SUBJECTS AND METHODS This retrospective study was approved by the Ethics Committee of Gachon University Gil Hospital of
Shin KH, et al. Br J Ophthalmol 2014;98:1250–1254. doi:10.1136/bjophthalmol-2013-304777
Downloaded from http://bjo.bmj.com/ on May 25, 2015 - Published by group.bmj.com
Clinical science Korea. We reviewed the records of consecutive patients aged 7 years who visited the paediatric eye clinic at Gachon University Gil Hospital between April 2002 and December 2008. Patients followed up through the entire early school period (from 7 years to 12 years of age) and diagnosed with mild myopia (spherical equivalent refraction (SER) between −0.5 and −3.0 dioptre (D)) in both eyes at presentation were enrolled. Reviewed patients were divided into three groups; (A) Patients with intermittent exotropia and myopia at presentation and who underwent bilateral lateral rectus muscle recession for exotropia between 7 years and 12 years of age; (B) Patients with intermittent exotropia and myopia at presentation and who were merely observed for exotropia; and (C) Patients with myopia and straight ocular alignment. Intermittent exotropia was defined as an intermittent exodeviation of at least 10 prism dioptres (PD) at a distance. Patients that underwent surgery for exotropia before 7 years of age and patients with myopia of more than moderate degree (SER ≥−3.0 D) at 7 years of age were excluded. Patients that had unilateral recession and resection surgery on one eye were excluded in order to avoid the possibility of interocular difference in refractive status which could be induced by the type of surgery or by surgery itself.30–32 In addition, those with a history of reoperation for recurrent exotropia/consecutive esotropia during or after the early school age period, those with strabismus associated with a neurological/genetic/ metabolic abnormality, those with other significant ocular diseases (congenital cataract, retinopathy of prematurity or a congenital anomaly), anisometropia of >1.5 D, astigmatism of >1.0 D or visual problems including amblyopia, were also excluded. The basic demographic data collected included gender, age at surgery for exotropia in Group A, refractive error status, and clinical data including angle of exodeviation in groups A and B (at 7 years and at 12 years of age). Angle of deviation was measured using loose prisms (Luneau Ophtalmologie, France). The alternate prism cover test was performed in all patients with exotropia under full correction of refractive errors. Refractions were measured in patients at initial presentation following the topical administration of 1% tropicamide (Mydriacyl, Alcon, Belgium) and 1% cyclopentolate hydrochloride (Cyclogyl, Alcon Laboratories, Texas, USA). Meanwhile, manifest refraction using retinoscopy (Welch Allyn, New York, USA) was performed during follow-up after the prescription of spectacles. Since the majority of patients wore spectacles already before 7 years of age, manifest refraction was used predominantly to evaluate refractive error status. Measurements of refraction
error were performed by static retinoscopy using a working distance of 0.6 m. SER values of the right and the left eyes were averaged to obtain a refractive value for each patient, based on the premise that patients with anisometropia were excluded. Main outcome measurements were the rate of myopic progression for the comparison among three groups, the rate of refractive growth (RRG) for the preoperative /postoperative comparison of the extent of myopic progression in Group A, and the rate of high myopia development (SER ≥−6 D) at the end of the early school period, as derived by Kaplan-Meier survival analysis. The rate of myopic progression was defined as the total myopic shift per year of observation over the 6 years observation period. The RRG which was proposed by McClatchey and Hofmeister,25 was introduced to reflect the logarithmic nature of refractive growth. The semilog plot (slope) of mean refraction versus log of age, where Age1 and Refraction1 are from the younger age, and Age2 and Refration2 are from the older age. Rate of refractive growth ¼ ðRefraction2 Refraction1 Þ= (log((Age2 þ 0:6yr)=(Age1 þ 0:6yr))) Statistical analyses were performed using SPSS for Windows, V.12.0 (SPSS, Chicago, Illinois, USA), and p values of
Clinical science
The impact of intermittent exotropia and surgery for intermittent exotropia on myopic progression among early school-aged children with myopia Kwang Hoon Shin, Sang Hun Hyun, Iris Naheah Kim, Hae Jung Paik Department of Ophthalmology, Gachon University Gil Hospital, Incheon, Republic of Korea Correspondence to Dr Hae Jung Paik, Department of Ophthalmology, Gachon University Gil Hospital, 1198, Guwol-dong, Namdong-gu, Incheon 405-760, Republic of Korea; [email protected] Received 12 December 2013 Revised 11 February 2014 Accepted 29 March 2014 Published Online First 29 April 2014
ABSTRACT Aim To investigate the relationship between myopic progression and intermittent exotropia, and the impact of surgery for exotropia on myopic progression in early school-aged children (from 7 years to 12 years of age). Methods Medical records of early school-aged patients with myopia were reviewed. Patients were divided into three groups; (A) Patients with intermittent exotropia and myopia at presentation and who underwent bilateral lateral rectus muscle recession for exotropia when 7–12 years old; (B) Patients with intermittent exotropia and myopia at presentation and who were merely observed for exotropia; and (C) Patients with myopia and straight ocular alignment. Main outcome measurements were the simple rate of myopic progression per year, the preoperative and postoperative rates of refractive growth with regards to the logarithmic age model in Group A, and the rate of high myopia development at the end of the early school period. Results The rates of myopic progression were −0.43 ±0.14 dioptre (D) per year in Group A, −0.49 ±0.17 D/year in Group B and −0.42±0.24 D/year in Group C. There was no significant difference in the rate of myopic progression among three groups. There was no significant intergroup difference in the preoperative and postoperative rates of refractive growth in Group A. There were no significant intergroup differences in the rates of high myopia development among three groups. Conclusions Whether patients with intermittent exotropia underwent surgical correction for intermittent exotropia did not influence the rate of myopic progression. There was no significant difference in the rate of myopic progression between patients with accompanying intermittent exotropia and myopia and those with myopia alone.
INTRODUCTION
To cite: Shin KH, Hyun SH, Kim IN, et al. Br J Ophthalmol 2014;98: 1250–1254. 1250
A presumption of the influence of intermittent exotropia on the development and progression of myopia has been continuously presented. Increased accommodative demand has been presented as a potential explanation for the association between intermittent exotropia and myopia in patients with intermittent exotropia.1 When describing the mechanism of myopia progression, increase in global axial length and associated myopic progression is assumed to be induced as an effort to decrease accommodation against excessive increase of accommodative demand.2 3 Horwood and Riddell4 suggested that the increased vergence necessary to control the exodeviation brings along overaccommodation in patients with intermittent distant exotropia. Theoretically, the effort to control ocular
alignment in intermittent exotropia can influence the progression of myopia through increase of accommodative demand. Ekdawi et al5 reported that intermittent exotropia was related with the development of myopia in their population-based study. The association between esotropia and hyperopia or anisometropia has been firmly established.6– 8 However, the association of intermittent exotropia with myopia has not been established as well, and not even has been studied rigorously. Myopia is the important public health issue nowadays. It was even referred to as one of the five immediate priorities for the Vision 2020 initiative of WHO.9–11 High prevalence of myopia has been demonstrated well, especially in East Asia.12–18 An awareness of the increasing prevalence of myopia has also been demonstrated in the USA.19 20 Myopia progression has been suggested to cease at 15–16 years of age.21 22 According to the growth function for myopia (Gompertz function) to estimate the age and the amount of myopia at stabilisation proposed recently by the Correction Of Myopia Evaluation Trial Group, myopia was estimated to be stabilised at 15.61 years of age.23 Also from the perspective of ocular biometric measurements, enlargement of globe size is usually completed by approximately 13 years of age.24 Since the natural refractive growth, which shows a tendency towards myopic shift, follows the logarithmic model with regards to the child’s age,25 the extent of refractive change decreases with advancing years. Even in childhood age, younger children show a greater change in refractive error status and axial length of globe when compared with older teenagers.26–28 Moreover, early onset of myopia is associated with high myopia in adults.29 The early school period is an important period in the development and progression of myopia. On the basis of the theoretical association between intermittent exotropia and myopia mentioned above, we hypothesise that intermittent exotropia might influence the myopic progression and that surgery for intermittent exotropia might reduce the rate of myopic progression when compared with those with intermittent exotropia who had no surgery. The aim of this study was to investigate the relationship between myopic progression and intermittent exotropia, and the impact of surgery for exotropia on myopic progression in early schoolaged children (from 7 years to 12 years of age).
SUBJECTS AND METHODS This retrospective study was approved by the Ethics Committee of Gachon University Gil Hospital of
Shin KH, et al. Br J Ophthalmol 2014;98:1250–1254. doi:10.1136/bjophthalmol-2013-304777
Downloaded from http://bjo.bmj.com/ on May 25, 2015 - Published by group.bmj.com
Clinical science Korea. We reviewed the records of consecutive patients aged 7 years who visited the paediatric eye clinic at Gachon University Gil Hospital between April 2002 and December 2008. Patients followed up through the entire early school period (from 7 years to 12 years of age) and diagnosed with mild myopia (spherical equivalent refraction (SER) between −0.5 and −3.0 dioptre (D)) in both eyes at presentation were enrolled. Reviewed patients were divided into three groups; (A) Patients with intermittent exotropia and myopia at presentation and who underwent bilateral lateral rectus muscle recession for exotropia between 7 years and 12 years of age; (B) Patients with intermittent exotropia and myopia at presentation and who were merely observed for exotropia; and (C) Patients with myopia and straight ocular alignment. Intermittent exotropia was defined as an intermittent exodeviation of at least 10 prism dioptres (PD) at a distance. Patients that underwent surgery for exotropia before 7 years of age and patients with myopia of more than moderate degree (SER ≥−3.0 D) at 7 years of age were excluded. Patients that had unilateral recession and resection surgery on one eye were excluded in order to avoid the possibility of interocular difference in refractive status which could be induced by the type of surgery or by surgery itself.30–32 In addition, those with a history of reoperation for recurrent exotropia/consecutive esotropia during or after the early school age period, those with strabismus associated with a neurological/genetic/ metabolic abnormality, those with other significant ocular diseases (congenital cataract, retinopathy of prematurity or a congenital anomaly), anisometropia of >1.5 D, astigmatism of >1.0 D or visual problems including amblyopia, were also excluded. The basic demographic data collected included gender, age at surgery for exotropia in Group A, refractive error status, and clinical data including angle of exodeviation in groups A and B (at 7 years and at 12 years of age). Angle of deviation was measured using loose prisms (Luneau Ophtalmologie, France). The alternate prism cover test was performed in all patients with exotropia under full correction of refractive errors. Refractions were measured in patients at initial presentation following the topical administration of 1% tropicamide (Mydriacyl, Alcon, Belgium) and 1% cyclopentolate hydrochloride (Cyclogyl, Alcon Laboratories, Texas, USA). Meanwhile, manifest refraction using retinoscopy (Welch Allyn, New York, USA) was performed during follow-up after the prescription of spectacles. Since the majority of patients wore spectacles already before 7 years of age, manifest refraction was used predominantly to evaluate refractive error status. Measurements of refraction
error were performed by static retinoscopy using a working distance of 0.6 m. SER values of the right and the left eyes were averaged to obtain a refractive value for each patient, based on the premise that patients with anisometropia were excluded. Main outcome measurements were the rate of myopic progression for the comparison among three groups, the rate of refractive growth (RRG) for the preoperative /postoperative comparison of the extent of myopic progression in Group A, and the rate of high myopia development (SER ≥−6 D) at the end of the early school period, as derived by Kaplan-Meier survival analysis. The rate of myopic progression was defined as the total myopic shift per year of observation over the 6 years observation period. The RRG which was proposed by McClatchey and Hofmeister,25 was introduced to reflect the logarithmic nature of refractive growth. The semilog plot (slope) of mean refraction versus log of age, where Age1 and Refraction1 are from the younger age, and Age2 and Refration2 are from the older age. Rate of refractive growth ¼ ðRefraction2 Refraction1 Þ= (log((Age2 þ 0:6yr)=(Age1 þ 0:6yr))) Statistical analyses were performed using SPSS for Windows, V.12.0 (SPSS, Chicago, Illinois, USA), and p values of
