MyopiaNCT00172913
Aberration-Free Refraction Correction
An observational study of Myopia, run by National Taiwan University Hospital at 1 site in Taiwan.
Trial summary
In the interest of improving visual quality after LASIK we have designed a multifaceted study to test the theoretical, physical, biomechanical and functional effects of commercial and independently designed aspherical ablation profiles. Read more about this study
- Who is it for?
- Ages 0 years and olderHealthy volunteers can take part
- Conditions the study is for
- Myopia
- How many people
- 60 participants
- Where
- 1 siteTaiwan
- Study dates
- Jun 2005to Jul 2008
- Phase
- Observational
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 0 years and older
- All sexes
- Healthy volunteers accepted
- Child, Adult, Older adult
Who may be able to join
- This will be a prospective study including at least 60 patients. The initial study group will include 6-10 patients. Both eyes of enrolled patients should be included in the study unless exclusion criteria prevent it. The primary efficacy variables for this study are wavefront error, visual acuity, autorefraction and contrast sensitivity. Subjects will be followed over a 3 month period. A proposed examination schedule is listed in Table 1.
- Eyes will also be divided into groups by refractive error: Low myopia 0-3D, moderate myopia 3-6D, and high myopia 6-9 D and very high myopia > 9D MSRE. The size of the Optical Zone and Transitional Zone is measured, and results are compared for patients of similar refractive error (+/- 0.5 S +/- 0.5 C). Analysis is carried out using a matrix analysis of the total refractive error, comparison of Visual Acuity, Contrast Sensitivity and Responses on a Questionnaire to assess the patient's quality of vision.
- Equal numbers of eyes from each of the four refractive error groups and from each of the three treatment groups (OATZ profile 5, OATZ profile 6, conventional) will be measured.
- We will consider patients operated on by the same doctor (Dr. Lin). We will also compare treatments of patients and wavefront maps of patients who have similar spherical and cylindrical refractive errors.
- Table 1. Examination Schedule (Definitions) Visit Time Preoperative Within 30 days of surgery Operative Day Day of surgery
- 1 Month postop 3-5 weeks following surgery 3 Months postop 10-14 weeks following surgery
Who cannot join
- Patients will be excluded if they have a history of ocular pathology, previous ocular surgery, thin corneas (preoperatively calculated minimal residual bed < 250um) or fit into the group of the usual exclusionary criteria (e.g. irregular astigmatism, asymmetric astigmatism, unstable refraction).
- Possible additional exclusion criteria include no previous refractive surgery, no hyperopia, preop BSCVA 20/25 or better, ages from 21-60 years old, astigmatism above 2D, difficult cases and equal numbers of men and women
Trial locations and contacts
1 site in 1 country.
Taiwan1 site, 1 recruiting
- Recruiting
National Taiwan University Hospital
Taipei
I-Jong Wang, MD, PHD, 886-2-23123456 ext. 5729, ijong@ha.mc.ntu.edu.tw
About this study
Official title: National Taiwan University Hospital
In the interest of improving visual quality after LASIK we have designed a multifaceted study to test the theoretical, physical, biomechanical and functional effects of commercial and independently designed aspherical ablation profiles.
Read the detailed description
The quality of an image on the retina is determined by the optical system of the eyeball, which is dominated by the refractive contribution of the optically powerful cornea. The large difference in refractive index between air and the cornea is the basis for anterior corneal refractive surgery such as Laser in situ Keratomileusis (LASIK) which reshapes the naturally aspherical cornea to correct a patient's vision. In addition to correcting refractive errors, current spherical LASIK treatments have been shown to increase ocular wavefront aberrations which can reduce visual quality postoperatively. Modifications of the corneal-ablation algorithm have been suggested to correct this issue.
Until recently, most ablation algorithms have relied on the Munnerlyn formula, which assumes the anterior corneal surface to be spherical before and after refractive surgery. One concept for customized ablation is to apply an ablation during the surgical procedure which has been adapted to the patient's own aberration pattern. Since custom ablation algorithms are proprietary and we do not know how they consider the role of asphericity.
Precisely altering the corneal asphericity after refraction surgery is a complex phenomenon which includes biomechanical effects. Thus, knowledge of the cornea's response to the different aspherical ablation profiles is vital for understanding corneal properties and prediction of surgical outcomes.
This study will involve computer simulation of ablation profiles for the respective lasers, interferometric analysis of actual ablation profiles on PMMA plates, optimization for visual correction, functional studies of the short and long term effects of the profiles on in vivo human corneas, and quantitative subjective (questionnaire and visual tests) and objective analysis (calculation of retinal image quality metrics) and comparison of the effects aspherical ablation profiles on visual quality. The completion of the project will lead to objective evaluation of current ablation profiles as well as the development and evaluation of new optimized laser refractive surgery procedures with improved outcomes.
- Conditions
- Myopia
- Keywords
- Wavefront Aberration, LASIK, Contrast Sensitivity, Visual Performance, Ablation Profile
- Medical subject headings
- Myopia
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted15 Sep 2005 (estimated)
- Study startJun 2005
- Study completionJul 2008
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for MyopiaStudies of the same condition, open and under way.
- More trials run by National Taiwan University HospitalThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Defined population
- Time perspective
- Other
- Enrolment
- 60 participants
Sponsor and investigators
- Lead sponsor
- National Taiwan University Hospital
- Sponsor type
- University, hospital or other
- Investigators
- I-Jong Wang, MD,PHD, Principal investigator, National Taiwan University Hospiyal
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT00172913
- Sponsor's protocol ID
- 9461700324
- Status last verified
- Jun 2005
- First submitted
- 12 Sep 2005
- Last updated
- 15 Sep 2005
- Results posted
- No
Study at a glance
From the registry record, last updated by the sponsor on 15 Sep 2005. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- National Taiwan University Hospital
- ClinicalTrials.gov ID
- NCT00172913
- Acronym / sponsor ID
- 9461700324
- Conditions
- Myopia
- Keywords
- Wavefront Aberration, LASIK, Contrast Sensitivity, Visual Performance, Ablation Profile
- Study type
- Observational
- Recruitment status
- Unknown status
- Enrolment
- 60 participants
- Lead sponsor
- National Taiwan University HospitalUniversity, hospital or other
- Study start
- Jun 2005
- Study completion
- Jul 2008
- First posted
- 15 Sep 2005 (estimated)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
In the interest of improving visual quality after LASIK we have designed a multifaceted study to test the theoretical, physical, biomechanical and functional effects of commercial and independently designed aspherical ablation profiles.
Detailed description
The quality of an image on the retina is determined by the optical system of the eyeball, which is dominated by the refractive contribution of the optically powerful cornea. The large difference in refractive index between air and the cornea is the basis for anterior corneal refractive surgery such as Laser in situ Keratomileusis (LASIK) which reshapes the naturally aspherical cornea to correct a patient's vision. In addition to correcting refractive errors, current spherical LASIK treatments have been shown to increase ocular wavefront aberrations which can reduce visual quality postoperatively. Modifications of the corneal-ablation algorithm have been suggested to correct this issue.
Until recently, most ablation algorithms have relied on the Munnerlyn formula, which assumes the anterior corneal surface to be spherical before and after refractive surgery. One concept for customized ablation is to apply an ablation during the surgical procedure which has been adapted to the patient's own aberration pattern. Since custom ablation algorithms are proprietary and we do not know how they consider the role of asphericity.
Precisely altering the corneal asphericity after refraction surgery is a complex phenomenon which includes biomechanical effects. Thus, knowledge of the cornea's response to the different aspherical ablation profiles is vital for understanding corneal properties and prediction of surgical outcomes.
This study will involve computer simulation of ablation profiles for the respective lasers, interferometric analysis of actual ablation profiles on PMMA plates, optimization for visual correction, functional studies of the short and long term effects of the profiles on in vivo human corneas, and quantitative subjective (questionnaire and visual tests) and objective analysis (calculation of retinal image quality metrics) and comparison of the effects aspherical ablation profiles on visual quality. The completion of the project will lead to objective evaluation of current ablation profiles as well as the development and evaluation of new optimized laser refractive surgery procedures with improved outcomes.
Study design
- Observational model
- Defined population
- Time perspective
- Other
Who may qualify
- Ages
- 0 years and older
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Child, Adult, Older adult
Key inclusion criteria (6 listed)
- This will be a prospective study including at least 60 patients. The initial study group will include 6-10 patients. Both eyes of enrolled patients should be included in the study unless exclusion criteria prevent it. The primary efficacy variables for this study are wavefront error, visual acuity, autorefraction and contrast sensitivity. Subjects will be followed over a 3 month period. A proposed examination schedule is listed in Table 1.
- Eyes will also be divided into groups by refractive error: Low myopia 0-3D, moderate myopia 3-6D, and high myopia 6-9 D and very high myopia > 9D MSRE. The size of the Optical Zone and Transitional Zone is measured, and results are compared for patients of similar refractive error (+/- 0.5 S +/- 0.5 C). Analysis is carried out using a matrix analysis of the total refractive error, comparison of Visual Acuity, Contrast Sensitivity and Responses on a Questionnaire to assess the patient's quality of vision.
- Equal numbers of eyes from each of the four refractive error groups and from each of the three treatment groups (OATZ profile 5, OATZ profile 6, conventional) will be measured.
- We will consider patients operated on by the same doctor (Dr. Lin). We will also compare treatments of patients and wavefront maps of patients who have similar spherical and cylindrical refractive errors.
- Table 1. Examination Schedule (Definitions) Visit Time Preoperative Within 30 days of surgery Operative Day Day of surgery
Key exclusion criteria (2 listed)
- Patients will be excluded if they have a history of ocular pathology, previous ocular surgery, thin corneas (preoperatively calculated minimal residual bed < 250um) or fit into the group of the usual exclusionary criteria (e.g. irregular astigmatism, asymmetric astigmatism, unstable refraction).
- Possible additional exclusion criteria include no previous refractive surgery, no hyperopia, preop BSCVA 20/25 or better, ages from 21-60 years old, astigmatism above 2D, difficult cases and equal numbers of men and women
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Primary outcome
Not reported in the source record.
Results and safety
Results are not available in the source record.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 15 Sep 2005.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
I-Jong Wang, MD,PHD principal investigator
National Taiwan University Hospiyal
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Myopia, run by National Taiwan University Hospital at 1 site in Taiwan.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 6 inclusion and 2 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: status not confirmed, as of the sponsor's last update on 15 Sep 2005. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Taiwan. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
Results are not available in the source record.
How can a doctor refer a patient or contact the research team?
Contact I-Jong Wang, MD, PHD (886-2-23123456 ext. 5729, ijong@ha.mc.ntu.edu.tw), or a site near the patient. AzTrials does not enrol participants or take referrals.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 15 Sep 2005; AzTrials last refreshed its copy on 28 Oct 2026.