Intraocular Lens Power Calculation After Laser Refractive Surgery Based on Optical Coherence Tomography (OCT IOL)

This study is currently recruiting participants.
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:
NCT00532051
First received: September 18, 2007
Last updated: April 7, 2014
Last verified: April 2014
  Purpose

The long-term goal of this project is to utilize newly available very high-speed optical coherence tomography (OCT) technology to guide surgical treatments of corneal diseases. OCT is well known for its exquisite resolution, but until recently it has not had sufficient speed to capture the shape of the cornea because of eye motion during OCT scanning. The development of Fourier-domain (FD) OCT technology has made the requisite speed possible.

The objective of this project is to develop methods for imaging the cornea with an FD-OCT system that will precisely measure corneal shape and use this information to guide surgery. Cataract surgery in patients with previous laser vision correction often leads to significant near- or far-sightedness, a problem that could be resolved by using a more accurate intraocular lens power selection formula based on the measurement of corneal refractive power with OCT.


Condition Intervention
Cataract
Device: OCT measurements

Study Type: Observational
Study Design: Observational Model: Case-Only
Time Perspective: Prospective
Official Title: Guiding the Treatment of Anterior Eye Diseases With Optical Coherence Tomography

Resource links provided by NLM:


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

Primary Outcome Measures:
  • IOL power prediction error [ Time Frame: Pre-surgery and post-operatively at 1 month ] [ Designated as safety issue: No ]
    Subjects will be assessed both preoperatively and at one month post cataract surgery


Estimated Enrollment: 40
Study Start Date: April 2011
Estimated Study Completion Date: July 2016
Estimated Primary Completion Date: July 2016 (Final data collection date for primary outcome measure)
Intervention Details:
    Device: OCT measurements
    This study is about a new imaging method to study the front part of the eye. This imaging method is called Optical Coherence Tomography (OCT) which provides detailed cross-sectional (layered) views of structures in the eye. The OCT system scans a beam of light across the eye to take a picture. OCT provides a more detailed image than other imaging methods of the eye such as ultrasound, CT scan (computed tomography), and MRI (magnetic resonance imaging). In addition, OCT imaging does not touch the eye. OCT is routinely used in imaging structures in the back of the eye (retina) and cornea. This study uses high-speed FDA approved OCT systemsThe measurements from the OCT systems are used in selecting IOL power.
    Other Names:
    • Manufacturer/Name OCT Technology 510(K)
    • Optovue/RTVue-CAM Fourier-domain K071250
    • Bioptigen/Bioptigen Fourier-domain K063343
    • Zeiss/Visante Time-domain K051789
Detailed Description:

This study is about a new imaging method to study the front part of the eye. This imaging method is called Optical Coherence Tomography (OCT) which provides detailed cross-sectional (layered) views of structures in the eye. The OCT system scans a beam of light across the eye to take a picture. OCT provides a more detailed image than other imaging methods of the eye such as ultrasound, CT scan (computed tomography) and MRI (magnetic resonance imaging). In addition, OCT imaging does not touch the eye. OCT is routinely used in imaging structures in the back of the eye (retina) and cornea. This study uses high-speed FDA approved OCT systems. The proposed research plan is a combination of clinical studies and software development to be performed synergistically. Clinical studies will provide OCT images for image processing software development and testing. The image processing software will provide automated measurement of anatomic parameters essential for clinical use.

Cataract extraction and IOL implantation is the most common eye surgery. The power of the IOL implant is calculated from 2 measurements: the axial eye length (AL) and keratometric power (K). The Holladay II formula also uses the external corneal diameter ("white-to-white" or WTW) and anterior chamber depth (ACD). These formulae work well (±0.5D) in normal eyes. However, these formulae can leads to biased and unpredictable refractive results in eyes that had refractive surgery procedures such as LASIK, PRK, and RK. With a large number of patients undergoing refractive surgery every year, the problem is becoming more severe.

The conventional IOL formulae fail because several inherent assumptions are no longer true in the eye that had refractive surgery. These assumptions are: 1) The corneal refractive power is uniform. 2) The anterior and posterior corneal power has a fixed relationship such that the overall corneal refractive power can be calculated from the anterior keratometry (or topography) using the keratometric index. 3) The position of IOL can be predicted by K with or without additional information such as WTW and ACD.

Relative to the posterior curvature, the anterior curvature becomes flatter after myopic correction and steeper after hyperopic correction with LASIK or PRK. To adapt the conventional IOL formulae to this situation, most surgeons use rigid contact lens over-refraction to calculate an "effective K." However, the accuracy of refraction in cataract patients is poor due to poor vision. Alternatively, one could use a historical method to calculate the effective K from pre-refractive surgery values. However, those measurements are often no longer available. If many years have lapsed, the historical value may no longer accurately reflect the current shape of the cornea.

The axial position of the IOL is determined by the positions of lens zonules and capsule which is in turn related to the corneal curvature (K) in the normal eye. A flatter cornea (lower K) is usually associated with a larger anterior segment, where the lens apparatus is located further back. A more complex model that also uses a separately measured white-to-white corneal diameter may be even more accurate. In post-refractive surgery eyes, however, K is altered and no longer has the normal relationship with the size of the eye. One way to get around this is to enter the pre-refractive surgery K. However, this historical information is not always available. We believe that a better solution would be use an entirely different approach that does not depend on the 3 above assumptions at all. Since OCT can separately measure the corneal anterior and posterior surfaces and AC and lens dimensions, we believe it has the potential of being the basis of a much better IOL calculation formula.

  Eligibility

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

patients seeking cataract surgery with implantation of monofocal IOLs (including toric IOLs) but not multifocal or accommodative IOLs.

Criteria

Inclusion Criteria:

  • The subjects will be patients seeking cataract surgery with implantation of monofocal IOLs (including toric IOLs) but not multifocal or accommodative IOLs.
  • Subjects will have had post-laser vision correction (LVC) such as previous LASIK, PRK, laser sub-epithelial keratectomy (LASEK), epi-LASIK (surface laser ablation under a microkeratome-created epithelial flap) or RK. The post-LVC group will be subdivided into those who have previous hyperopic LVC and those who have previous myopic LVC.

Exclusion Criteria:

  • Inability to give informed consent.
  • Inability to maintain stable fixation for OCT imaging.
  • Inability to commit to required visits to complete the study.
  • Eyes with concurrent cataract, retinal diseases, glaucoma, or other eye conditions that may limit the visual outcome after surgery.
  Contacts and Locations
Please refer to this study by its ClinicalTrials.gov identifier: NCT00532051

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

Locations
United States, Oregon
Casey Eye Institute, Oregon Health & Science University Recruiting
Portland, Oregon, United States, 97229
Contact: Janice Ladwig    503-494-8024    ladwig@ohsu.edu   
Contact: Denny Romfh    503-494-4651    romfhd@ohsu.edu   
Sponsors and Collaborators
Oregon Health and Science University
Investigators
Principal Investigator: David Huang, MD, PhD Casey Eye Institute, Oregon Health & Science University
  More Information

No publications provided

Responsible Party: David Huang, Rick Fraunfelder, MD, Director of Cornea and Refractive Surgery, Associate Professor of Ophthalmology, Oregon Health and Science University
ClinicalTrials.gov Identifier: NCT00532051     History of Changes
Other Study ID Numbers: OHSU IRB #00006612-IOL, 7R01EY018184-04
Study First Received: September 18, 2007
Last Updated: April 7, 2014
Health Authority: United States: Institutional Review Board

Keywords provided by Oregon Health and Science University:
cataract, lasik, laser refractive surgery

Additional relevant MeSH terms:
Cataract
Lens Diseases
Eye Diseases

ClinicalTrials.gov processed this record on April 15, 2014