Strabismus surgery at the Puerto Rico Medical Center: a brief report.
Abstract: Objective: We undertook a retrospective study to evaluate strabismus surgeries done at the University Hospital and at the University Pediatric Hospital of the Puerto Rico Medical Center.

Methods: The surgery schedules ranging from January 2003 to December 2007 were reviewed. Three types of strabismus were evaluated, including esotropia, exotropia, and hypertopia. Differences in the distribution of strabismus type according to age group and gender were assessed using the extension of the Fisher's exact test.

Results: A total of 120 patients were included (56 males and 64 females); the patients ranged in age from 4 months to 70 years (average: 15.1 years. Analysis of the distribution of strabismus type showed that 63 (52.5%) had esotropia; 49 (40.8%) had exotropia; 4 (3.3%) had hypertropia; 3 (2.5%) had both hypertropia and exotropia; and 1 (0.9%) had both hypertropia and esotropia. Both esotropia and exotropia were significantly (p<0.0001) more common in children than they were in adults; however, hypertropia and combined strabismus types were more common in adults than they were in children. There was no statistical (p>0.05) significance found upon analyzing strabismus distribution according to gender.

Conclusion: Among patients with this eye disorder at the Puerto Rico Medical Center, the most common type of surgically treated strabismus was esotropia. Further studies will elucidate the prevalence of strabismus in Puerto Rico. [P R Health Sci J 2011;30:203-205]

Key words: Strabismus, Esotropia, Exotropia

Objetivo: Se realizo un estudio retrospectivo evaluando los itinerarios de cirugias de estrabismo del Hospital Universitario y del Hospital Universitario Pediatrico del Centro Medico de PR, desde enero de 2003 a diciembre de 2007. Metodos: Se evaluaron tres tipos de estrabismo: esotropia, exotropia e hipertropia. Las diferencias en la distribucion del tipo de estrabismo segun la edad y el genero se evaluaron mediante la extension de la prueba exacta de Fisher. Resultados: Un total de 120 pacientes (56 hombres y 64 mujeres) desde las edades de 4 meses a 70 anos (promedio: 15.1 anos) se incluyeron en el estudio. La distribucion del tipo de estrabismo reflejo lo siguiente: 63 (52.5%) tenian esotropia; 49 (40.8%) tenian exotropia; 4 (3.3%) tenian hipertropia; 3 (2.5%) presentaron exotropia e hipertropia; y 1 (0.9%) presento esotropia e hipertropia. Esotropia y exotropia fueron significativamente (p<0.0001) mas comunes en ninos que en adultos; sin embargo, la hipertropia y los tipos combinados fueron mas comunes en adultos que en ninos. No hubo diferencia significativa (p>0.05) en la distribucion de esotropia, exotropia o hipertropia entre hombres y mujeres. Conclusion: En pacientes con estos desordenes oculares atendidos en el Centro Medico de Puerto Rico, la esotropia fue el tipo mas comun de estrabismo tratado quirurgicamente. Estudios futuros evaluaran la prevalencia de estrabismo en la isla.
Article Type: Perspectiva general de la enfermedad/trastorno
Authors: Horta-Santini, Juan M.
Vergara, Claudia
Colon-Casasnovas, Jaime E.
Izquierdo, Natalio J.
Pub Date: 12/01/2011
Publication: Name: Puerto Rico Health Sciences Journal Publisher: Universidad de Puerto Rico, Recinto de Ciencias Medicas Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2011 Universidad de Puerto Rico, Recinto de Ciencias Medicas ISSN: 0738-0658
Issue: Date: Dec, 2011 Source Volume: 30 Source Issue: 4
Geographic: Geographic Scope: Puerto Rico
Accession Number: 274228544
Full Text: Strabismus is defined as any ocular misalignment (1). It has been associated both with abnormalities of the neuromuscular control of eye movements and with extraocular muscle pathology (1). Strabismus is a common disorder that affects up to 4 percent of preschool children in the United States (2).

The various types of strabismus are named according to the direction ofthe ocular misalignment. Esotropia, exotropia, and hypertropia (2) are described by an inward, outward, or vertical (upward) ocular manifest deviation, respectively. Patients with strabismus have poor fusion control (3).

Strabismus is associated with amblyopia. Patients with esotropia are more likely to develop amblyopia (4). This likelihood may be due to a disruption in the development of binocular vision, causing reduced stereopsis (5). In children, the latter may lead to poor visual-motor skills (5). Amblyopia is the most common cause of monocular visual impairment in both children and young and middle-aged adults (6). In the United States, amblyopia has an estimated prevalence of less than 2% percent in both White and African American pediatric patients (7-8).

Even though the prevalence of strabismus has been studied in various populations, it remains unknown in Puerto Rico. We report on the three major types of strabismus treated surgically at the Puerto Rico Medical Center.

Methods

A retrospective study was done by evaluating surgical schedules (which schedules included dates ranging from January 2003 to December 2007) at the University Hospital and at the University Pediatric Hospital of the Puerto Rico Medical Center.

Specifically, strabismus surgeries were evaluated. Data were analyzed in terms of age and gender. For the purpose of the study, children were labeled as patients younger than 18 years old and adults as those who were 18 years old or older. Summary statistics were computed to describe the strabismus type, age and gender ofpatients. Differences in the distribution of strabismus type according to age group and gender were assessed using the extension of the Fisher's exact test.

Results

One hundred and twenty patients underwent strabismus surgery. Patients' ages ranged from 4 months to 70 years (mean = 15.1 years). There were 56 (46.7%) male and 64 (53.3%) female patients.

Patients were grouped according to strabismus type: 63 (52.5%) had esotropia; 49 (40.8%) had exotropia; 4 (3.3%) had hypertropia; 3 (2.5%) had both hypertropia and exotropia; and 1 (0.9%) had both hypertropia and esotropia.

There was a significant (p<0.0001) difference found when an analysis of the age distribution of strabismus was performed (Table 1). Both esotropia and exotropia were more common in children than they were in adults. However, hypertropia and combined strabismus types were more common in adults than they were in children. There was no statistical (p>0.05) significance found upon analyzing strabismus distribution according to gender.

Discussion

Previous studies have reported that the most common types of strabismus that lead to surgery are esotropia and exotropia (9-10). In our study, esotropia was the most frequent type of strabismus (45.8%) leading to surgery. Exotropia was the second-most type (33.3%) leading to strabismus surgery. These findings are compatible with those of previous reports. However, they differ from those of reports from Chile, (11) where exotropia is the leading diagnosis associated with strabismus surgery.

A multi-ethnic study from the United States reports that strabismus increases with age in the Latino population (12). In this study, exotropia and esotropia were more common in children than they were in adults. This finding differs from previous studies of Latino populations done in the continental United States.

Ferreira and co-workers (13) explain that there are as yet no statistically significant reports exploring the role of gender in the etiology of strabismus. In our study, no statistical significance was found in the distribution of strabismus according to gender, either. This finding is consistent with previous reports.

Several factors may contribute to a higher frequency of strabismus in Puerto Rico. The island's geographic isolation may increase the possibility of hereditary factors leading to strabismus. Further, previous reports show an elevated number of premature infants born in the island, (14) and strabismus is associated with such premature birth (15).

Limitations of the study include the retrospective nature of the analysis. Further, because the study focused on operating room schedules (thus, not including non-surgically treated strabismus patients), the sample size may have been restricted.

The potential public health implications of this study are important. Further studies are needed to accurately quantify the prevalence of strabismus in Puerto Rico.

References

(1.) American Association for Pediatric Ophthalmology and Strabismus. Strabismus. American Association for Pediatric Ophthalmology and Strabismus. Available at: URL: http://www.aapos.org/terms/conditions/100. Accessed March 10, 2010.

(2.) Mohney BG, Greenberg AE, Diehl NN. Age at strabismus diagnosis in an incidence cohort of children. Am J Ophthalmol 2007;144:467-469.

(3.) Lorenz B, Brodsky M. Pediatric Ophthalmology, Neuro-Ophthalmology, Genetics: Strabismus--New Concepts in Pathophysiology, Diagnosis, and Treatment (Essentials in Ophthalmology). 1st ed. Berlin, Germany; Springer; 2010: 1-9.

(4.) Webber AL, Wood J. Amblyopia: prevalence, natural history, functional effects and treatment. Clin Exp Optom 2005;88:365-375.

(5.) Joy S, Davis H, Buckley D. Is stereopsis linked to hand-eye coordination? Br Orthopt J 2001;58:38-41.

(6.) Simons K. Preschool vision screening: rationale, methodology and outcome. Surv Ophthalmol 1996;41:3-30.

(7.) Friedman DS, Repka MX, Katz J, et al. Prevalence of amblyopia and strabismus in white and African American children aged 6 through 71 months the Baltimore Pediatric Eye Disease Study. Ophthalmology 2009;116:2128-2134.

(8.) National Eye Institute. Office of Biometry and Epidemiology. Report on the National Eye Institute's Visual Acuity Impairment Survey Pilot Study. Department of Health and Human Services. Washington, DC; 1984.

(9.) Kac MJ, Freitas Junior MB, Kac SI, et al. Frequency of ocular deviations at the strabismus sector of the Hospital do Servidor Publico Estadual de Sao Paulo [in Portuguese]. Arq Bras Oftalmol 2007;70:939-942.

(10.) Murthy GV, Gupta SK, Ellwein LB, et al. Refractive Error in Children in an Urban Population in New Delhi. Invest Ophthalmol Vis Sci 2002;43: 623-631.

(11.) Maul E, Barroso S, Munoz SR, et al. Refractive Error Study in Children: results from La Florida, Chile. Am J Ophthalmol 2000;129:445-454.

(12.) Multi-ethnic Pediatric Eye Disease Study Group. Prevalence of amblyopia and strabismus in African American and Hispanic children ages 6 to 72 months the multi-ethnic pediatric eye disease study. Ophthalmology 2008;115:1229-1236.

(13.) Ferreira RC, Oelrich F, Bateman B. Genetic aspects of strabismus. Arq Bras Oftalmol 2002;65:171-175

(14.) Centers for Disease Control and Prevention (CDC). Infant health among Puerto Ricans--Puerto Rico and U.S. mainland, 1989-2000. MMWR Morb Mortal Wkly Rep 2003;52:1012-1016.

(15.) Robaei D, Rose KA, Kifley A, et al. Factors associated with childhood strabismus: findings from a population-based study. Ophthalmology 2006;113:1146-1153.

Juan M. Horta-Santini, MD *; Claudia Vergara, MD ([dagger]); Jaime E. Colon-Casasnovas, MD ([double dagger]); Natalio J. Izquierdo, MD *

* Department of Ophthalmology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico; ([dagger]) School of Medicine, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico; ([double dagger]) Ponce School of Medicine and Health Sciences, Ponce, Puerto Rico

The authors have no conflicts of interest to disclose.

Address correspondence to: Natalio J. Izquierdo, MD, Department of Ophthalmology, University of Puerto Rico Medical Sciences Campus, PO Box 365067, San Juan, Puerto Rico 00936-5067. Email: njuan@msn.com
Table 1. Distribution of strabismus type by age and gender among
120 patients treated surgically at the Puerto Rico Medical Center,
2003-2007.

                                Esotropia     Exotropia     Hypertropia
                                (n=63)        (n=49)        (n=4)

Age
<18                             57 (90.5)     38 (77.6)     1 (25.0)
[greater than or equal to] 18   6 (9.5)       11 (22.4)     3 (75.0)

Gender
Male                            30 (47.6)     22 (44.9)     1 (25.0)
Female                          33 (52.4)     27 (55.1)     3 (75.0)

                                Combined      p value
                                types *       ([dagger])
                                (n=4)
Age
<18                             1 (25.0)      <0.0001
[greater than or equal to] 18   3 (75.0)

Gender
Male                            3 (75.0)      >0.05
Female                          1 (25.0)

* Combined types include esotropia and hypertropia (1) and exotropia
and hypertropia (3). ([dagger]) P value calculated using the
extension of the Fisher's exact test.
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