skip navigation

S M L Text size
Home » Resources » Clinical Studies » Congenital Esotropia Observational Study (CEOS)

NEI Clinical Studies

Archived Page

The information on this page is archived and provided for reference purposes only. It was current when it was produced, but may now be out-of-date. Persons having difficulty accessing this information may contact for assistance. For reliable, current information on this and other topics, we recommend that you visit the National Eye Institute website index.

Congenital Esotropia Observational Study (CEOS)

Purpose | Background | Description | Patient Eligibility | Recruitment Status | Current Status | Results | Publications | Resource Centers | NEI Representative


To observe the early course of congenital esotropia, a form of childhood strabismus. This will determine the probability of spontaneous resolution. Researchers then will try to correlate this finding with various aspects of the esotropia such as the (1) size of the esotropia, (2) variability, and (3) presence of hyperopia. This information will be used to determine the feasibility of conducting a clinical trial to assess the benefit of early surgery for congenital esotropia and, if feasible, to refine eligibility criteria for the trial.


Congenital esotropia is the most common form of childhood strabismus. Despite its common occurrence, limited information is available about its early clinical course. Such data are needed to determine the earliest age at which surgery can be safely performed without concern that the esotropia is likely to resolve spontaneously. Although the term congenital esotropia implies that the esotropia is present at birth, in many cases the esotropia actually develops sometime during the first few months of life. It is well recognized that congenital esotropia persisting through 6 months of age rarely if ever resolves spontaneously and therefore requires surgical correction. However, it is not clear how often congenital esotropia occurs and then resolves (at an earlier age such that surgery is not necessary) before surgery is required.

Current clinical practice is to defer surgery for congenital esotropia until 6 to 12 months of age. Assuming that characteristics of congenital esotropia at 2 to 4 months of age can be identified to predict which cases will require surgery, then a trial will be warranted to determine whether performing earlier surgery enhances the development of binocular vision. The potential benefit to very early surgery is supported by neurophysiologic research, which has shown that (1) congenital esotropes may be born with the innate ability to develop binocular vision, (2) there is a critical period for development of normal binocular function within the first few months of life that is dependent on alignment of the visual axes of the two eyes, and (3) ocular misalignment alone, regardless of its mechanism, without a coexisting primary cortical fusion deficit, can account for abnormal development of binocular vision. Clinical reports have demonstrated that surgical correction of the esotropia between 6 and 12 months of age provides for enhanced development of stereoacuity compared with later surgery. However, there are limited data on the outcomes in infants who had surgical correction before age 6 months.


The protocol for the study is identical to usual clinical practice. Following informed consent, two followup visits are conducted: one 2 to 4 weeks after the first examination and the other when the child is between 28 and 32 weeks of age. The examinations will be identical to the pediatric ophthalmologist's usual routine, and no additional procedures are being performed specifically for the study. Management of refractive error and amblyopia is left to the ophthalmologist's discretion. A sample size of 150 has been projected for the study.

Patient Eligibility

Neurologically and developmentally normal infants with congenital esotropia who are between 4 and 20 weeks of age are eligible for CEOS.

Patient Recruitment Status

Completed. Recruitment began in December 1997 and closed in July 2000 after 188 patients were enrolled.

Current Status of Study

Completed. Follow up of patients ended in December 2000.


Esotropia with onset in early infancy frequently resolves in patients first examined at less than 20 weeks of age when the deviation is <40 pd in size and is intermittent or variable. cases with a constant deviation > 40 pd presenting after 10 weeks of age have a low likelihood of spontaneous resolution. Our results can be used to define a clinical profile for which persistence of the esotropia is sufficiently likely that surgical correction at three to four months of age could reasonable be considered.


Spontaneous resolution of early-onset esotropia: Experience oft he Congenital Esotropia Observational Study. Am J Ophthalmol, In press.

The clinical spectrum of early-onset esotropia: Experience of the Congenital Esotropia Observational Study. Am J Ophthalmol, In press.

Resource Centers

Chairman's Office
Kenneth W. Wright, M.D.
Cedars-Sinai Medical Center
8631 West Third Street
Suite 304 East
Los Angeles, CA 90048
Telephone: (310) 652-6420
Fax: (310) 652-6463

Coordinating Center
Roy W. Beck, M.D., Ph.D.
Pamela S. Moke, M.S.P.H.
Jaeb Center for Health Research
3010 East 138th Avenue
Suite 9
Tampa, FL 33613
Telephone: (813) 975-8690
Fax: (813) 975-8761

NEI Representative

Donald F. Everett, M.A.
Clinical Trials Branch
National Eye Institute
6120 Executive Boulevard, MSC 7164
EPS 350
Bethesda, MD 20892-7164
Telephone: (301) 496-5983
Fax: (301) 402-0528

Last Updated: 10/22/01

Department of Health and Human Services NIH, the National Institutes of Health