Factors Affecting Corneal Hysteresis in Taiwanese

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT01235780
Recruitment Status : Completed
First Posted : November 8, 2010
Last Update Posted : November 8, 2010
Information provided by:
Far Eastern Memorial Hospital

Brief Summary:
The purpose of the study is to investigate the factors affecting corneal hysteresis (CH) in Taiwanese.

Condition or disease
Corneal Hysteresis

Detailed Description:

The ocular response analyzer (ORA, Reichert Ophthalmic Instruments, Buffalo, NY, USA) measures the biomechanical properties of the cornea in vivo. It provides several measurements including CH, corneal resistance factor (CRF), corneal-compensated intraocular pressure (IOPcc), and Goldmann-correlated intraocular pressure (IOPg). Corneal hysteresis is described as the viscous damping due to the viscoelastic resistance of the cornea to a deformation pulse by an air jet of the tonometer. Whereas CH may reflect corneal viscosity, the CRF may relate to the elastic properties of the cornea. Both parameters are measured by the ORA using a dynamic bidirectional process.

CH can be affected by various ocular disorders and operation. In previous studies, CH was found to be significantly lower in keratoconus, Fuchs' dystrophy, and glaucoma. After laser in situ keratomileusis (LASIK) and phacoemulsification, CH permanently or temporally decreased. Among normal population, CH was also variable and associated with several factors: age, gender, intraocular pressure, central corneal thickness, and corneal curvature. High myopic patients with long axial length were found to have lower CH than in normal subjects. CH can also affected by races, and CH was largely discussed in Caucasian population. Herein we studied normal population of CH and associated factors and in Taiwan.

We are planned to conduct a retrospective study from January to July, 2009 at Department of Ophthalmology, Far Eastern Memorial Hospital, Taipei, Taiwan by chart review. We will enroll the patients with bilateral cataract, or unilateral cataract and healthy fellow eye, who not having other ocular pathology, prior ocular surgery, or previous trauma. Several ocular parameters and demographics of both un-operated eyes in these patients are measured. CRF, IOPcc, IOPg, and CH are measured by ORA. Central corneal thickness is measured using the ORA's integrated handheld ultrasonic pachymeter. The IOLMaster (Carl Zeiss, Jena, German) is used to obtain the ocular biometry including axial length, anterior chamber depth, and keratometry. Linear regression models were used to test the correlation of CH and quantitative factors. The chi-square test was used to find the significance of correlation in categorical values.

One or two eyes of the patients undergoes uneventful phacoemulsification and in-the-bag implantation of posterior chamber intraocular lens (one-piece AcrySof, Alcon lab, Texas, USA) by one surgeon (Wang JK). The sutureless corneal wound was 2.75 mm long. CRF, IOPcc, IOPg, and CH are measured by ORA preoperatively and 1 day, 1 week, 2 weeks, 3 weeks, 1 month, 2 months, and 3 months postoperatively. Paired t test was used to compare the changes of these parameters following the operation.

We expect that some factors will correlate with CH, such as axial length, IOP, age, and central corneal thickness. Temporary reduction in CH is possibly shortly after phacoemulsification, and returning to the baseline following a period of time.

Study Type : Observational
Actual Enrollment : 83 participants
Observational Model: Case Control
Time Perspective: Retrospective
Official Title: Factors Affecting Corneal Hysteresis in Taiwanese
Study Start Date : December 2009
Actual Study Completion Date : July 2010

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Ages Eligible for Study:   33 Years to 86 Years   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No
Sampling Method:   Probability Sample
Study Population
Normal population and patients receiving phacoemulsification

Inclusion Criteria:

  • normal population

Exclusion Criteria:

  • no other ocular diseases except cataract, no prior ocular operation, no prior ocular trauma

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT01235780

Sponsors and Collaborators
Far Eastern Memorial Hospital
Study Chair: Jia-Kang Wang, M.D. Ophthalmologic Department, Far Eastern Memorial Hospital

Responsible Party: Shih-Hong Huang MD,PhD, Research Ethics Review Committee of Far Eastern Memorial Hospital Identifier: NCT01235780     History of Changes
Other Study ID Numbers: 098060-3
First Posted: November 8, 2010    Key Record Dates
Last Update Posted: November 8, 2010
Last Verified: December 2009

Keywords provided by Far Eastern Memorial Hospital:
corneal hysteresis, ocular response analyzer