Compare Anterior Chamber Biometry in Healthy and Post-LASIK Patients

The recruitment status of this study is unknown because the information has not been verified recently.
Verified February 2009 by Far Eastern Memorial Hospital.
Recruitment status was  Recruiting
Sponsor:
Information provided by:
Far Eastern Memorial Hospital
ClinicalTrials.gov Identifier:
NCT00838734
First received: February 4, 2009
Last updated: February 5, 2009
Last verified: February 2009
  Purpose

In this study, the investigators employed Visante-OCT (Carl Zeiss, USA), an anterior chamber optical coherence tomography, to monitor the change of anterior chamber dimensions. These data were correlated to anterior and posterior curvature changes collected with the Oculus Pentacam (Oculus Inc., Germany), a corneal topographer based on rotating Scheimpflug principle. To minimize the effect of convergence and excyclotorsion during examination, topical cycloplegic medication was used. The investigators hypothesized that if there is a link between ciliary muscle contraction and cornea curvature, installation of cycloplegic should result in widening of anterior chamber angle to angle distance and flattening of the cornea curvature data.


Condition
Myopia
Astigmatism

Study Type: Observational
Study Design: Observational Model: Cohort
Time Perspective: Prospective
Official Title: Compare Anterior Chamber Biometry in Healthy and Post-LASIK Pati

Further study details as provided by Far Eastern Memorial Hospital:

Estimated Enrollment: 100
Study Start Date: June 2008
Estimated Study Completion Date: June 2009
Groups/Cohorts
1
Pre-LASIK
2
Post-LASIK

Detailed Description:

Accommodation is an action that enables projections of both distant and near objects to be brought into clear focus on the retina through changing of diopteric power of crystalline lens. Although the exact mechanism of accommodation remains inconclusive, most authors agree that contraction of ciliary muscle plays a pivotal role.1, 2 Recently, accumulating evidence shows that the effect of ciliary muscle contraction goes beyond merely changing the curvature of the crystalline lens.3 Ciliary muscle contraction might be responsible for a transient elongation in axial length during the accommodation response.3 Contraction of ciliary smooth muscle applied an inward pulling force on the choroid and sclera adjacent to the ciliary body and cause protrusion at posterior sclera.

If ciliary muscle contraction can elicit protrusion at posterior sclera, it is conceivable that some changes in corneal shape would also occur as the cornea is adjacent to ciliary muscle. The influence of accommodation on the cornea has therefore been the subject of several studies with conflicting results. Some authors reported no change4, 5, while others described significant change in corneal curvature during accommodation6-9. Yasuda and Yamaguchi9 found central corneal steepening of approximately 0.10 D, using pharmacologically induced ciliary muscle contraction and corneal topography analysis. Saitoh et al10 reported that instillation of a sympathomimetic agent to stimulate mydriasis induces significant flattening of both anterior and posterior cornea curvatures as detected by Orbscan . On the contrary, Buehren5 and Read4 argue that changes in corneal topography is a result of excyclotorsional eye movement during accommodation. When this excyclotorsional eye movement was accounted for in their data analysis, no significant change in corneal topography was found with accommodation. The effect of ciliary relaxation on the cornea curvature, however, was less well delineated.

In this study, we employed Visante-OCT (Carl ZeiIn this study, we employed Visante-OCT (Carl Zeiss, USA), an anterior chamber optical coherence tomography, to monitor the change of anterior chamber dimensions. These data were correlated to anterior and posterior curvature changes collected with the Oculus Pentacam (Oculus Inc., Germany), a corneal topographer based on rotating Scheimpflug principle. To minimize the effect of convergence and excyclotorsion during examination, topical cycloplegic medication was used. We hypothesized that if there is a link between ciliary muscle contraction and cornea curvature, installation of cycloplegic should result in widening of anterior chamber angle to angle distance and flattening of the cornea curvature data.

ss, USA), an anterior chamber optical coherence tomography, to monitor the change of anterior chamber dimensions. These data were correlated to anterior and posterior curvature changes collected with the Oculus Pentacam (Oculus Inc., Germany), a corneal topographer based on rotating Scheimpflug principle. To minimize the effect of convergence and excyclotorsion during examination, topical cycloplegic medication was used. We hypothesized that if there is a link between ciliary muscle contraction and cornea curvature, installation of cycloplegic should result in widening of anterior chamber angle to angle distance and flattening of the cornea curvature data.

In addition, we would also compare the accuracy in pupil diameter measurements between Pentacam and Visante OCT under under normal and mydratic conditions.

  Eligibility

Ages Eligible for Study:   18 Years to 35 Years
Genders Eligible for Study:   Both
Accepts Healthy Volunteers:   Yes
Sampling Method:   Non-Probability Sample
Study Population

Healthy volunteer

Criteria

Inclusion Criteria:

  • healthy young volunteer who has not received any ocular surgery
  • post-LASIK surgery young volunteers
  • all participants has to be less than 35 years old.

Exclusion Criteria:

  • any subject with contact lens history will be asked to stop contact lens wear for at least 4 weeks before participating in this study.
  • any subject with prior ocular disease
  • any subject with prior intra-ocular surgery
  • any subject who cannot cooperate with examination
  Contacts and Locations
Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below. For general information, see Learn About Clinical Studies.

Please refer to this study by its ClinicalTrials.gov identifier: NCT00838734

Contacts
Contact: Shu-Wen Chang, MD 866-2-8966-7000 ext 4271 swchang@mail.femh.org.tw

Locations
Taiwan
Far Eastern Memorial Hospital Recruiting
Pan-Chiao, Taipei, Taiwan, 220
Contact: Shu-Wen Chang, MD    886-2-8966-7000    swchang@mail.femh.org.tw   
Sponsors and Collaborators
Far Eastern Memorial Hospital
Investigators
Principal Investigator: Shu-Wen Chang, MD Far Eastern Memorial Hospital
  More Information

No publications provided

Responsible Party: Shu-Wen Chang, Far Eastern Memorial Hospital
ClinicalTrials.gov Identifier: NCT00838734     History of Changes
Other Study ID Numbers: FEMH97011
Study First Received: February 4, 2009
Last Updated: February 5, 2009
Health Authority: Taiwan: Institutional Review Board

Keywords provided by Far Eastern Memorial Hospital:
CORNEAL TOPOGRAPHY
KERATOPLASTY

Additional relevant MeSH terms:
Astigmatism
Myopia
Refractive Errors
Eye Diseases

ClinicalTrials.gov processed this record on July 24, 2014