AstigmatismPhase 3PRKNCT00663923
Comparison of Cross-cylinder and Conventional Photorefractive Keratectomy(PRK) in Correcting Medium-high Astigmatism
A Phase 3 study testing photorefractive keratectomy (PRK) in people with Astigmatism, run by Tabriz University at 1 site in Iran.
Trial summary
The purpose of this study is to determine whether cross-cylinder approach is more effective than routine method in laser correction of astigmatism. Read more about this study
- Who is it for?
- Ages 20 years and olderHealthy volunteers can take part
- Conditions the study is for
- Astigmatism
- What is being tested?
- photorefractive keratectomy (PRK)
- Type of treatment
- Surgery or procedure
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 50 participants
- Where
- 1 siteIran
- Study dates
- Nov 2007to Dec 2009
- Phase
- Phase 3
- Are there results?
- Yes, posted in the registrySummary in the doctors' view
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 20 years and older
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- >20 years of age
- refractive stability for at least one year
- regular and symmetric astigmatism of >1.5 diopters
Who cannot join
- corneal thickness<470 microns
- keratoconus or suspected keratoconus
- active ocular disease and systemic collagen disease
Trial locations and contacts
1 site in 1 country.
About this study
Official title: Comparison of Cross-cylinder and Conventional PRK for Laser Correction of Astigmatism: A Randomized Clinical Trial.
The purpose of this study is to determine whether cross-cylinder approach is more effective than routine method in laser correction of astigmatism.
Read the detailed description
Both eyes of 50 patients(100 eyes) with medium-high compound myopic astigmatism and inclusion criteria,will be treated by photorefractive keratectomy (PRK) using excimer laser.It breaks chemical bonds within corneal stroma.It's wavelength is 193 nm that is in the ultraviolets range with high energy and very low tissue penetrance. The right or left eye of every patient would be allocated randomly to one of the study groups using RandList 1.1. In spite of recent advances in excimer laser machines and surgical techniques,correction of astigmatism is not more successful compared to myopia. In this study we will compare two methods of laser correction of astigmatism regarding to visual acuity,residual error and aberrations.
- Conditions
- Astigmatism
- Being tested
- photorefractive keratectomy (PRK)
- Keywords
- Excimer Laser, photorefractive keratectomy, astigmatism
- Medical subject headings
- Astigmatism
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
photorefractive keratectomy (PRK)Procedure or surgery
Also called photoastigmatic keratectomy
comparison of PRK by cross-cylinder approach in one eye and conventional (single) method in the other eye for laser correction of astigmatism
| Study group | Role | What they receive |
|---|---|---|
| cross-cylinder | Experimental | In this technique the laser is programmed with the axis and amount of cylinder,so that the steepest meridian is flattened with central cylindrical ablation and the flattest meridian steepens with paracentral ablation Receives: Procedure: photorefractive keratectomy (PRK) |
| single | Active comparator | In this technique ,cylinder is treated only on one meridian by performing an elliptical ablation to to flatten the steeper meridian to match the flatter meridian. Receives: Procedure: photorefractive keratectomy (PRK) |
What is being measured
The primary outcome is the main question the study is designed to answer.
Correction of Astigmatism
It shows the result of correction of astigmatism .In compound myopic astigmatism the meridians of maximum and minimum power are both too strong.So both line images fall short of the retina.It is measured by refraction(using autorefractor).Diopter is a unit of measurement of the optical power of any refracting surface ,which is reciprocal of the focal length measured in meters.
Measured: six months after surgery
Secondary outcomes (4)
Higher Order Aberrations
Although lower- order aberrations decrease after laser vision correction,higher -order aberrations may increase after conventional PRK or LASIK(Laser in situ keratomileusis).Higher-order aberration is Composed of delicate irregularities within the cornea not correctable by spectacles.It is measured using aberrometer.In this study OPD scan was used that is one of the methods of wavefront analysis .
Measured: six months postoperative
Corrected Distance Visual Acuity(CDVA)
CDVA is attained after correction of refractive errors using lenses of varying powers .the data are the LogMAR values calculated from the snellen chart using the visual acuity conversion chart(the units would be LogMAR).Any patient with better vision can see the smallest letters at 20 feet(20/20=0.00 LogMAR).Higher LogMAR values represent worse outcome.Log MAR(logarithmic minimum angle of resolution)notation ,has gained widespread use in statistical calculations.
Measured: six months
Uncorrected Distance Visual Acuity (UCDVA)
UCDVA is attained without correction of refractive errors .the data are the LogMAR values calculated from the snellen chart using the visual acuity conversion chart( the units would be LogMAR).Any patient with better vision can see the smallest letters at 20 feet(20/20=0.00 LogMAR).Higher LogMAR values represent worse outcome.Log MAR(logarithmic minimum angle of resolution)notation ,has gained widespread use in statistical calculations.
Measured: six months
Surgically Induced Astigmatism
It is the vector of the astigmatic change actually induced by the surgery.Participant population was the same as baseline participants.
It was measured by refraction(using autorefractor) and vector analysis(using special software).Diopter is a unit of measurement of the optical power of any refracting surface ,which is reciprocal of the focal length measured in meters
Measured: six months after surgery
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted22 Apr 2008 (estimated)
- Study startNov 2007
- Primary completionJun 2009
- Study completionDec 2009
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
- Other trials for AstigmatismStudies of the same condition, open and under way.
- 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
- Interventional
- Phase
- Phase 3
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Single blind
- Who is masked
- Participant
- Enrolment
- 50 participants (actual)
Sponsor and investigators
- Lead sponsor
- Tabriz University
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Mohammad R Sedghipoor, MD, Study director, Ophthalmology Department, Tabriz University of medical Sciences
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT00663923
- Sponsor's protocol ID
- 86-43
- Acronym
- PRK
- Status last verified
- Mar 2012
- First submitted
- 18 Apr 2008
- Last updated
- 13 Mar 2012
- Results posted
- Yes, on ClinicalTrials.gov
- Data monitoring committee
- Yes
Study at a glance
From the registry record, last updated by the sponsor on 13 Mar 2012. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Comparison of Cross-cylinder and Conventional PRK for Laser Correction of Astigmatism: A Randomized Clinical Trial.
- ClinicalTrials.gov ID
- NCT00663923
- Acronym / sponsor ID
- PRK / 86-43
- Conditions
- Astigmatism
- Keywords
- Excimer Laser, photorefractive keratectomy, astigmatism
- Phase
- Phase 3
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 50 participants (actual)
- Lead sponsor
- Tabriz UniversityUniversity, hospital or other
- Study start
- Nov 2007
- Primary completion
- Jun 2009 (actual)
- Study completion
- Dec 2009 (actual)
- First posted
- 22 Apr 2008 (estimated)
- Results
- Posted 30 Dec 2011
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The purpose of this study is to determine whether cross-cylinder approach is more effective than routine method in laser correction of astigmatism.
Detailed description
Both eyes of 50 patients(100 eyes) with medium-high compound myopic astigmatism and inclusion criteria,will be treated by photorefractive keratectomy (PRK) using excimer laser.It breaks chemical bonds within corneal stroma.It's wavelength is 193 nm that is in the ultraviolets range with high energy and very low tissue penetrance. The right or left eye of every patient would be allocated randomly to one of the study groups using RandList 1.1. In spite of recent advances in excimer laser machines and surgical techniques,correction of astigmatism is not more successful compared to myopia. In this study we will compare two methods of laser correction of astigmatism regarding to visual acuity,residual error and aberrations.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Single blind (participant)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| cross-cylinder | Experimental | Procedure: photorefractive keratectomy (PRK)In this technique the laser is programmed with the axis and amount of cylinder,so that the steepest meridian is flattened with central cylindrical ablation and the flattest meridian steepens with paracentral ablation |
| single | Active comparator | Procedure: photorefractive keratectomy (PRK)In this technique ,cylinder is treated only on one meridian by performing an elliptical ablation to to flatten the steeper meridian to match the flatter meridian. |
Who may qualify
- Ages
- 20 years and older
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (3 listed)
- >20 years of age
- refractive stability for at least one year
- regular and symmetric astigmatism of >1.5 diopters
Key exclusion criteria (3 listed)
- corneal thickness<470 microns
- keratoconus or suspected keratoconus
- active ocular disease and systemic collagen disease
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| photorefractive keratectomy (PRK)Also: photoastigmatic keratectomycomparison of PRK by cross-cylinder approach in one eye and conventional (single) method in the other eye for laser correction of astigmatism | Procedure or surgery | cross-cylinder, single |
Primary outcome
Correction of Astigmatism
Time frame: six months after surgery
It shows the result of correction of astigmatism .In compound myopic astigmatism the meridians of maximum and minimum power are both too strong.So both line images fall short of the retina.It is measured by refraction(using autorefractor).Diopter is a unit of measurement of the optical power of any refracting surface ,which is reciprocal of the focal length measured in meters.
4 secondary outcomes
Higher Order Aberrations
Time frame: six months postoperative
Corrected Distance Visual Acuity(CDVA)
Time frame: six months
Uncorrected Distance Visual Acuity (UCDVA)
Time frame: six months
Surgically Induced Astigmatism
Time frame: six months after surgery
Results and safety
Loading the posted results from ClinicalTrials.gov…
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 13 Mar 2012.
- Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
Related trials for Astigmatism
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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.
Mohammad R Sedghipoor, MD study director
Ophthalmology Department, Tabriz University of medical Sciences
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 3 study testing photorefractive keratectomy (PRK) in people with Astigmatism, run by Tabriz University at 1 site in Iran.
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 3 inclusion and 3 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: finished, as of the sponsor's last update on 13 Mar 2012. 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 Iran. 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.
What does this phase mean?
Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
Yes. Results are posted in the registry (first posted 30 Dec 2011). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Correction of Astigmatism (time frame: six months after surgery). It is what the study was designed to measure, not a finding.
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 13 Mar 2012.