- Email: [email protected]
Female Predominance in Intermittent Exotropia
The incidence of abscess formation as a result of pit viper envenomation is 9%, and prophylactic antibiotics are recommended.6 The infection rate of venomous snakebite in northern Taiwan is 6.2%.7 Although there is no specific data for D acutus snakebite in the literature, prophylactic systemic antibiotics were prescribed for our patient, and his condition was not complicated by local infection. In summary, maintaining stable life signs and prevention of infection remain the chief strategies of treatment after venomous snakebite to the eye. In addition to antivenom, early evisceration was our treatment of choice for this patient’s blind eye.
prematurity, age at diagnosis and surgery, refractive error, and initial angle of deviation. CONCLUSIONS: Intermittent exotropia was nearly twice as common in girls compared with boys in this defined population. There were, however, no significant historical or clinical differences between the genders. (Am J Ophthalmol 2005;140:546 –547. © 2005 by Elsevier Inc. All rights reserved.)
I
of exodeviation and occurs more frequently than esotropia in some populations.1 Although common, populationbased data on the epidemiology of this disorder are nearly nonexistent. The primary objective of this study was to determine whether there are differences between genders in a population-based cohort of pediatric patients with intermittent exotropia. The medical records of all patients less than 19 years of age who were residing in Olmsted County, Minnesota and diagnosed by an ophthalmologist with intermittent exotropia from January 1, 1975, through December 31, 1994, were retrospectively reviewed. Institutional Review Board approval was obtained for this study and only patients who provided research authorization were included. Intermittent exotropia was defined in this study as an acquired, intermittent exodeviation of 10 or more prism diopters unassociated with other ocular, paralytic, or neurologic defects. Potential cases of intermittent exotropia were identified by means of the resources of the Rochester Epidemiology Project, a medical records linkage system designed to capture data on any patient-physician encounter in Olmsted County, Minnesota.2,3 Exotropic patients not residing in Olmsted County at the time of their diagnosis were excluded. One hundred eighty-four new cases of childhood intermittent exotropia were diagnosed in Olmsted County, Minnesota during the 20-year study period. Sixty-four percent of the 184 patients were female during a period in which the population of Olmsted County patients less than 19 years were nearly equally divided between the genders (Table). The age-adjusted incidence rate for intermittent exotropia in Olmsted County, Minnesota was 38.3 per 100,000 for girls, which is significantly greater than the 20.8 per 100,000 for boys (P ⬍ .0001). There were, however, no significant
REFERENCES
1. Gupta M, Sharma P, Jain A, Solanky J, Sharma KK, Basu S. Unusual site of snake bite. Trop Doct 1995;25:134 –135. 2. Kleinman DM, Dunne EF, Taravella MJ. Boa constrictor bite to the eye. Arch Ophthalmol 1998;116:949 –950. 3. Sheard RM, Smith GT. Penetrating eye injury following a snake attack. Eye 2003;17:279 –280. 4. Brandao EO, de Bastos HC, Nishioka Sde A, Silveira PV. Lance-headed viper (Bothrops moojeni) bite wounding the eye. Rev Inst Med Trop Sao Paulo 1993;35:381–383. 5. Warrel DA. Injuries, envenoming, poisoning, and allergic reactions caused by animals. In: Weatherall DA, Cox TM, Firth JD, Benz EJ Jr, editors. Oxford textbook of medicine, 4th ed. Oxford: Oxford University Press, 2003:923–946. 6. Kerrigan KR. Bacteriology of snakebite abscess. Trop Doct 1992;22:158 –160. 7. Chen JC, Liaw SJ, Bullard MJ, Chiu TF. Treatment of poisonous snakebites in northern Taiwan. J Formos Med Assoc 2000;99:135–139.
Female Predominance in Intermittent Exotropia Kevin J. Nusz, MD, Brian G. Mohney, MD, and Nancy N. Diehl, BS
To evaluate gender differences among children diagnosed with intermittent exotropia. DESIGN: Retrospective, population-based cohort study. METHODS: The medical records of all Olmsted County, Minnesota residents younger than 19 years diagnosed with intermittent exotropia from January 1, 1975, through December 31, 1994, were reviewed. RESULTS: One hundred eighteen (64.1%) of the 184 study patients were girls with an age-adjusted incidence rate of 38.3 (95% CI: 31.4 – 45.2) per 100,000 compared to 20.8 (95% CI: 15.7–25.8) per 100,000 for boys (P < .0001). There were no significant differences between girls and boys in their family history of strabismus, birth weight, prevalence of PURPOSE:
546
AMERICAN JOURNAL
NTERMITTENT EXOTROPIA IS THE MOST COMMON FORM
Accepted for publication Mar 2, 2005. From the Department of Ophthalmology (K.J.N., B.G.M.) and Division of Biostatistics (N.N.D.), Mayo Clinic and Mayo Foundation, Rochester, Minnesota. Supported in part by an unrestricted grant from Research to Prevent Blindness, Inc, New York, New York. Inquiries to Brian G. Mohney, MD, Mayo Clinic, Department of Ophthalmology, 200 First Street Southwest, Rochester, MN, 55905; fax: (507) 284-4612; e-mail: [email protected] OF
OPHTHALMOLOGY
SEPTEMBER 2005
TABLE. Historical and Initial Clinical Characteristics of 184 Patients With Intermittent Exotropia Less Than 19 Years From Olmsted County, Minnesota Characteristic
Females
Males
P Value
Incident cases (%) Age-adjusted incidence per 100,000 (95% confidence interval) 1990 Population of Olmsted County, MN, ages birth to 19 years (%) Number with positive family history of strabismus (%) Number born at ⬍37 weeks gestational age (%) Median birth weight in grams (range) Mean age at diagnosis in years (range) Number with amblyopia at first examination (%) Median angle of distance deviation in prism diopters (range) Median angle of near deviation in prism diopters (range) Median initial refractive error (range) Number who underwent at least one surgery (%) Mean age of first surgery in years (range)
118 (64.1%) 38.3 (31.4–45.2)
66 (35.9%) 20.8 (15.8–25.8)
⬍.0001 ⬍.0001
296, 201 (49%)
309, 316 (51%)
41 (34.8) 6 (5.1%) 3374 (953–4620) 6.2 (0.9–18.5) 2 (1.70%) 20 (10–40) 12 (0–45) ⫹0.50 (⫺3.25–⫹2.63) 41 (34.8%) 7.2 (3.3–22.1)
20 (30.3%) 4 (6.1%) 3382 (1640–4545) 6.5 (0.7–18.6) 2 (3.0%) 20 (10–40) 10 (0–45) ⫹0.25 (⫺8.00–⫹3.13) 18 (27.3%) 8.5 (3.6–22.8)
historical or clinical differences between the genders (Table). No prior reports on strabismus have demonstrated a predominance of girls among children with intermittent exotropia.1,3– 6 Former studies of prevalence either failed to distinguish between the intermittent variety and other forms or exotropia,4 or reported no appreciable difference between the genders.1,3,5,6 A recent study from Olmsted County, surveying a period of 10 years, a duration shorter than the current study, found that girls tended to be more likely than boys to develop exotropia during the first decade, whereas boys were more commonly exotropic during the teenage years (P ⫽ .10).3 However, they did not indicate gender for each of the individual forms of exotropia. Why intermittent exotropia may be more common among females is unclear. The gender distribution in this study suggests an X-linked dominant inheritance that would affect females nearly twice as often as males. However, an X-linked affected male would be expected to transfer the trait to all his daughters and none of his sons. This seems unlikely, although Lyonization, incomplete penetrance, and environmental factors could explain some of the discrepancies. Additionally, we cannot discount the possibility that parents of exotropic girls were more likely to seek medical attention for their child than were the parents of boys with the same condition.
VOL. 140, NO. 3
.83 .72 .76 .92 .62 .86 .73 .11 .33 .42
This population-based study found that intermittent exotropia is significantly more common among girls than boys. Two of every three children diagnosed with intermittent exotropia in this 20-year study were female. In contrast, there were no historical or clinical differences between the genders. Further studies are needed to validate the gender differences of this common form of childhood strabismus.
REFERENCES
1. Yu CB, Fan DS, Wong VW, et al. Changing patterns of strabismus: a decade of experience in Hong Kong. Br J Ophthalmol 2002;86:854 – 856. 2. Kurland LT, Molgaard CA. The patient record in epidemiology. Sci Am 1981;245:54 – 63. 3. Govindan M, Mohney BG, Diehl NN, Burke JP. Incidence and types of childhood exotropia: a population-based study. Ophthalmology 2005;112:104 –108. 4. Chew E, Remaley NA, Tamboli A, et al. Risk factors for esotropia and exotropia. Arch Ophthalmol 1994;112:1349 – 1355. 5. Graham PA. Epidemiology of strabismus. Br J Ophthalmol 1974;58:224 –231. 6. Friedman Z, Neumann E, Hyams SW, Peleg B. Ophthalmic screening of 38,000 children, age 1 to 2 and one half years, in child welfare clinics. J Pediatr Ophthalmol Strabismus 1980; 17:261–267.
BRIEF REPORTS
547
prematurity, age at diagnosis and surgery, refractive error, and initial angle of deviation. CONCLUSIONS: Intermittent exotropia was nearly twice as common in girls compared with boys in this defined population. There were, however, no significant historical or clinical differences between the genders. (Am J Ophthalmol 2005;140:546 –547. © 2005 by Elsevier Inc. All rights reserved.)
I
of exodeviation and occurs more frequently than esotropia in some populations.1 Although common, populationbased data on the epidemiology of this disorder are nearly nonexistent. The primary objective of this study was to determine whether there are differences between genders in a population-based cohort of pediatric patients with intermittent exotropia. The medical records of all patients less than 19 years of age who were residing in Olmsted County, Minnesota and diagnosed by an ophthalmologist with intermittent exotropia from January 1, 1975, through December 31, 1994, were retrospectively reviewed. Institutional Review Board approval was obtained for this study and only patients who provided research authorization were included. Intermittent exotropia was defined in this study as an acquired, intermittent exodeviation of 10 or more prism diopters unassociated with other ocular, paralytic, or neurologic defects. Potential cases of intermittent exotropia were identified by means of the resources of the Rochester Epidemiology Project, a medical records linkage system designed to capture data on any patient-physician encounter in Olmsted County, Minnesota.2,3 Exotropic patients not residing in Olmsted County at the time of their diagnosis were excluded. One hundred eighty-four new cases of childhood intermittent exotropia were diagnosed in Olmsted County, Minnesota during the 20-year study period. Sixty-four percent of the 184 patients were female during a period in which the population of Olmsted County patients less than 19 years were nearly equally divided between the genders (Table). The age-adjusted incidence rate for intermittent exotropia in Olmsted County, Minnesota was 38.3 per 100,000 for girls, which is significantly greater than the 20.8 per 100,000 for boys (P ⬍ .0001). There were, however, no significant
REFERENCES
1. Gupta M, Sharma P, Jain A, Solanky J, Sharma KK, Basu S. Unusual site of snake bite. Trop Doct 1995;25:134 –135. 2. Kleinman DM, Dunne EF, Taravella MJ. Boa constrictor bite to the eye. Arch Ophthalmol 1998;116:949 –950. 3. Sheard RM, Smith GT. Penetrating eye injury following a snake attack. Eye 2003;17:279 –280. 4. Brandao EO, de Bastos HC, Nishioka Sde A, Silveira PV. Lance-headed viper (Bothrops moojeni) bite wounding the eye. Rev Inst Med Trop Sao Paulo 1993;35:381–383. 5. Warrel DA. Injuries, envenoming, poisoning, and allergic reactions caused by animals. In: Weatherall DA, Cox TM, Firth JD, Benz EJ Jr, editors. Oxford textbook of medicine, 4th ed. Oxford: Oxford University Press, 2003:923–946. 6. Kerrigan KR. Bacteriology of snakebite abscess. Trop Doct 1992;22:158 –160. 7. Chen JC, Liaw SJ, Bullard MJ, Chiu TF. Treatment of poisonous snakebites in northern Taiwan. J Formos Med Assoc 2000;99:135–139.
Female Predominance in Intermittent Exotropia Kevin J. Nusz, MD, Brian G. Mohney, MD, and Nancy N. Diehl, BS
To evaluate gender differences among children diagnosed with intermittent exotropia. DESIGN: Retrospective, population-based cohort study. METHODS: The medical records of all Olmsted County, Minnesota residents younger than 19 years diagnosed with intermittent exotropia from January 1, 1975, through December 31, 1994, were reviewed. RESULTS: One hundred eighteen (64.1%) of the 184 study patients were girls with an age-adjusted incidence rate of 38.3 (95% CI: 31.4 – 45.2) per 100,000 compared to 20.8 (95% CI: 15.7–25.8) per 100,000 for boys (P < .0001). There were no significant differences between girls and boys in their family history of strabismus, birth weight, prevalence of PURPOSE:
546
AMERICAN JOURNAL
NTERMITTENT EXOTROPIA IS THE MOST COMMON FORM
Accepted for publication Mar 2, 2005. From the Department of Ophthalmology (K.J.N., B.G.M.) and Division of Biostatistics (N.N.D.), Mayo Clinic and Mayo Foundation, Rochester, Minnesota. Supported in part by an unrestricted grant from Research to Prevent Blindness, Inc, New York, New York. Inquiries to Brian G. Mohney, MD, Mayo Clinic, Department of Ophthalmology, 200 First Street Southwest, Rochester, MN, 55905; fax: (507) 284-4612; e-mail: [email protected] OF
OPHTHALMOLOGY
SEPTEMBER 2005
TABLE. Historical and Initial Clinical Characteristics of 184 Patients With Intermittent Exotropia Less Than 19 Years From Olmsted County, Minnesota Characteristic
Females
Males
P Value
Incident cases (%) Age-adjusted incidence per 100,000 (95% confidence interval) 1990 Population of Olmsted County, MN, ages birth to 19 years (%) Number with positive family history of strabismus (%) Number born at ⬍37 weeks gestational age (%) Median birth weight in grams (range) Mean age at diagnosis in years (range) Number with amblyopia at first examination (%) Median angle of distance deviation in prism diopters (range) Median angle of near deviation in prism diopters (range) Median initial refractive error (range) Number who underwent at least one surgery (%) Mean age of first surgery in years (range)
118 (64.1%) 38.3 (31.4–45.2)
66 (35.9%) 20.8 (15.8–25.8)
⬍.0001 ⬍.0001
296, 201 (49%)
309, 316 (51%)
41 (34.8) 6 (5.1%) 3374 (953–4620) 6.2 (0.9–18.5) 2 (1.70%) 20 (10–40) 12 (0–45) ⫹0.50 (⫺3.25–⫹2.63) 41 (34.8%) 7.2 (3.3–22.1)
20 (30.3%) 4 (6.1%) 3382 (1640–4545) 6.5 (0.7–18.6) 2 (3.0%) 20 (10–40) 10 (0–45) ⫹0.25 (⫺8.00–⫹3.13) 18 (27.3%) 8.5 (3.6–22.8)
historical or clinical differences between the genders (Table). No prior reports on strabismus have demonstrated a predominance of girls among children with intermittent exotropia.1,3– 6 Former studies of prevalence either failed to distinguish between the intermittent variety and other forms or exotropia,4 or reported no appreciable difference between the genders.1,3,5,6 A recent study from Olmsted County, surveying a period of 10 years, a duration shorter than the current study, found that girls tended to be more likely than boys to develop exotropia during the first decade, whereas boys were more commonly exotropic during the teenage years (P ⫽ .10).3 However, they did not indicate gender for each of the individual forms of exotropia. Why intermittent exotropia may be more common among females is unclear. The gender distribution in this study suggests an X-linked dominant inheritance that would affect females nearly twice as often as males. However, an X-linked affected male would be expected to transfer the trait to all his daughters and none of his sons. This seems unlikely, although Lyonization, incomplete penetrance, and environmental factors could explain some of the discrepancies. Additionally, we cannot discount the possibility that parents of exotropic girls were more likely to seek medical attention for their child than were the parents of boys with the same condition.
VOL. 140, NO. 3
.83 .72 .76 .92 .62 .86 .73 .11 .33 .42
This population-based study found that intermittent exotropia is significantly more common among girls than boys. Two of every three children diagnosed with intermittent exotropia in this 20-year study were female. In contrast, there were no historical or clinical differences between the genders. Further studies are needed to validate the gender differences of this common form of childhood strabismus.
REFERENCES
1. Yu CB, Fan DS, Wong VW, et al. Changing patterns of strabismus: a decade of experience in Hong Kong. Br J Ophthalmol 2002;86:854 – 856. 2. Kurland LT, Molgaard CA. The patient record in epidemiology. Sci Am 1981;245:54 – 63. 3. Govindan M, Mohney BG, Diehl NN, Burke JP. Incidence and types of childhood exotropia: a population-based study. Ophthalmology 2005;112:104 –108. 4. Chew E, Remaley NA, Tamboli A, et al. Risk factors for esotropia and exotropia. Arch Ophthalmol 1994;112:1349 – 1355. 5. Graham PA. Epidemiology of strabismus. Br J Ophthalmol 1974;58:224 –231. 6. Friedman Z, Neumann E, Hyams SW, Peleg B. Ophthalmic screening of 38,000 children, age 1 to 2 and one half years, in child welfare clinics. J Pediatr Ophthalmol Strabismus 1980; 17:261–267.
BRIEF REPORTS
547