Trial record 20 of 26 for:    Open Studies | "Astigmatism"

Corneal Power, Astigmatism, and Aberration Changes After LASIK

This study is currently recruiting participants. (see Contacts and Locations)
Verified April 2014 by Oregon Health and Science University
Sponsor:
Collaborator:
Information provided by (Responsible Party):
David Huang, Oregon Health and Science University
ClinicalTrials.gov Identifier:
NCT01893671
First received: July 2, 2013
Last updated: April 7, 2014
Last verified: April 2014
  Purpose

The primary goal of the study is to determine if Optical Coherence Tomography (OCT) measurement of corneal power and astigmatism is more accurate than conventional Placido-ring corneal topography. A second goal is to evaluate OCT-based epithelial thickness mapping. The postoperative epithelial thickness variation will be used to calculate refractive effects and calibrate the smoothing parameter in the mathematical model relating corneal mean curvature and epithelial thickness. A third goal is to assess the repeatability of OCT measurements. A fourth goal is to develop a method of estimating the focusing power, astigmatism, and HOA of the crystalline lens based on measurements of the lens' anterior and posterior capsular topographies and positions with the ultrahigh-speed MIT OCT prototype.


Condition
Measurements of Patients Using OCT Before and After LASIK

Study Type: Observational
Study Design: Observational Model: Case-Only
Time Perspective: Prospective
Official Title: Observational Study of Corneal Power, Astigmatism, and Aberration Changes After LASIK

Further study details as provided by Oregon Health and Science University:

Primary Outcome Measures:
  • OCT measurement of corneal power and astigmatism vs Placido-ring [ Time Frame: 5 year ] [ Designated as safety issue: No ]
    primary goal of the study is to determine if OCT measurement of corneal power and astigmatism is more accurate than conventional Placido-ring corneal topography


Secondary Outcome Measures:
  • An evaluation of OCT-based epithelial thickness mapping [ Time Frame: 5 year ] [ Designated as safety issue: No ]
    The postoperative epithelial thickness variation will be used to calculate refractive effects and calibrate the smoothing parameter in the mathematical model relating corneal mean curvature and epithelial thickness.

  • OCT measurements repeatability [ Time Frame: 5 year ] [ Designated as safety issue: No ]
    An assessment of the repeatability of OCT measurements

  • The Development of a method of estimating the focusing power, astigmatism, and HOA of the crystalline lens [ Time Frame: 5 year ] [ Designated as safety issue: No ]
    The Development of a method of estimating the focusing power, astigmatism, and HOA of the crystalline lens based on measurements of the lens' anterior and posterior capsular topographies and positions with the ultrahigh-speed MIT OCT prototype.


Estimated Enrollment: 50
Study Start Date: January 2011
Estimated Study Completion Date: June 2016
Estimated Primary Completion Date: June 2016 (Final data collection date for primary outcome measure)
Groups/Cohorts
LASIK
Subjects undergoing routine LASIK for the correction of myopia or hyperopia.

Detailed Description:

A prospective observational study on refraction and HOA changes after LASIK will be conducted at OHSU and Baylor. We will enroll 50 subjects undergoing routine LASIK for the correction of myopia or hyperopia. The Optovue anterior segment OCT prototype will be used to measure corneal power, astigmatism, HOA, and epithelial thickness map. The ultrahigh-speed MIT OCT prototypes will also be used when they become available. A comprehensive eye examination will be performed preoperatively. OCT scan, manifest refraction, visual acuity, Placido-ring corneal topography, slit scanning/Scheimpflug camera, and wavefront measurements will be acquired preoperatively and 3-6 months after the surgery. The LASIK-induced refraction and wavefront HOA changes will be used as the reference standard to evaluate the accuracy of OCT-measured corneal power, astigmatism, and HOA changes. The primary goal of the study is to determine if OCT measurement of corneal power and astigmatism is more accurate than conventional Placido-ring corneal topography. A second goal is to evaluate OCT-based epithelial thickness mapping. The postoperative epithelial thickness variation will be used to calculate refractive effects and calibrate the smoothing parameter in the mathematical model relating corneal mean curvature and epithelial thickness. A third goal is to assess the repeatability of OCT measurements. A fourth goal is to develop a method of estimating the focusing power, astigmatism, and HOA of the crystalline lens based on measurements of the lens' anterior and posterior capsular topographies and positions with the ultrahigh-speed MIT OCT prototype. The reference standard for lens focusing power and astigmatism will be based on a Gaussian optics model that takes as inputs manifest refraction, crystalline lens position, axial eye length, and OCT corneal power and astigmatism measurements. The reference standard for lens HOA will be the difference between wavefront HOA and corneal HOA. For each eye, the best-fit effective index of the lens will be found so that OCT measurements will match the reference data. Although the lens index is likely to be higher centrally than peripherally, this secondary perturbation will be accounted for by a posterior shift of the posterior lens capsule in OCT images, due to the fact that apparent distances in OCT images is a product of physical distance and optical group index. Thus HOA due to index variation in the lens would translate to unevenness in the posterior capsule surface that could be measured with OCT.

  Eligibility

Ages Eligible for Study:   18 Years and older
Genders Eligible for Study:   Both
Accepts Healthy Volunteers:   No
Sampling Method:   Non-Probability Sample
Study Population

Subjects undergoing routine LASIK for the correction of myopia or hyperopia with or without astigmatism

Criteria

Inclusion Criteria:

1. Patients who qualify for primary LASIK for either myopia or hyperopia, with or without astigmatism.

Exclusion Criteria:

  1. Inability to give informed consent.
  2. Inability to maintain stable fixation for OCT imaging.
  3. Inability to commit to required visits to complete the study.
  4. Eyes with concurrent cataract, retinal diseases, glaucoma, or other eye conditions that may limit the visual outcome after surgery
  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: NCT01893671

Contacts
Contact: Janice Ladwig, COT 503-494-8024 ladwig@ohsu.edu
Contact: Denny Romfh 503-494-4351 romfhd@ohsu.edu

Locations
United States, Oregon
Oregon Health & Science University Recruiting
Portland, Oregon, United States, 97239
Contact: Janice Ladwig    503-494-8024    ladwig@ohsu.edu   
Sub-Investigator: David Huang, MD, PhD         
Sub-Investigator: Winston Chamberlain, MD, PhD         
Sub-Investigator: Rebecca Armour, MD         
Sub-Investigator: Lorinna Lombardi, MD         
Sponsors and Collaborators
Oregon Health and Science University
Investigators
Principal Investigator: Frederick Fraunfelder, M.D. Oregon Health & Science Universtiy
  More Information

No publications provided

Responsible Party: David Huang, Frederick Fraunfelder, MD, Professor of Ophthalmology, Oregon Health and Science University
ClinicalTrials.gov Identifier: NCT01893671     History of Changes
Other Study ID Numbers: OHSU IRB#6612, R01EY018184
Study First Received: July 2, 2013
Last Updated: April 7, 2014
Health Authority: United States: Institutional Review Board

Keywords provided by Oregon Health and Science University:
LASIK
corneal power
astigmatism
HOA
Optical Coherence Tomography

Additional relevant MeSH terms:
Astigmatism
Refractive Errors
Eye Diseases

ClinicalTrials.gov processed this record on July 22, 2014