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The purpose of this study is to determine whether cross-cylinder approach is more effective than routine method in laser correction of astigmatism.
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.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| 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 |
|
| 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. |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| photorefractive keratectomy (PRK) | Procedure | comparison of PRK by cross-cylinder approach in one eye and conventional (single) method in the other eye for laser correction of astigmatism |
| Measure | Description | Time Frame |
|---|---|---|
| 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. | six months after surgery |
| Measure | Description | Time Frame |
|---|---|---|
| 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 . |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Affiliation | Role |
|---|---|---|
| Mohammad R Sedghipoor, MD | Ophthalmology Department, Tabriz University of medical Sciences | Study Director |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Nikookari eye hospital | Tabriz | East Azerbaijan Province | 5154645395 | Iran |
All enrolled patients having inclusion criteria accepted both available techniques for correction of astigmatism.
Both eyes of Fifty patients with medium-high compound myopic astigmatism(1.5- 5 D) were enrolled in a prospective randomized study between sep 2007 and sep 2008 at Nikookari eye hospital and Mehr eye center
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| ID | Title | Description |
|---|---|---|
| FG000 | Photorefractivekeratectomy(PRK) | Right or left eye of 50 patients was randomly enrolled(data provided in this module refer to 100 eyes of 50 participants)to undergo PRK by cross-cylinder or conventional(single) approach using Excimer laser.In cross-cylinder method , half of the cylinder is treated along the steepest meridian and the other half is ablated along the flattest meridian .in single method,the steepest meridian is treated by elliptical ablation to match the flattest meridian. |
| Title | Milestones | Reasons Not Completed | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Overall Study |
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| ID | Title | Description |
|---|---|---|
| BG000 | Photorefractive Keratectomy( PRK) | Right or left eye of 50 patients was randomly enrolled(data provided in this module refer to100 eyes of 50 participants)to undergo PRK by cross-cylinder or conventional(single) approach using Excimer laser.In cross-cylinder method , half of the cylinder is treated along the steepest meridian and the other half is ablated along the flattest meridian .In single method the steepest meridian is treated by elliptical ablation to match the flattest meridian. |
| Units | Counts |
|---|---|
| Participants |
|
| Title | Description | Population Description | Parameter Type | Dispersion Type | Unit of Measure | Calculate Percentage | Denominator Units Selected | Denominators | Classes |
|---|---|---|---|---|---|---|---|---|---|
| Age, Categorical | Count of Participants |
| Type | Title | Description | Population Description | Reporting Status | Anticipated Posting Date | Parameter Type | Dispersion Type | Unit of Measure | Calculate Percentage | Time Frame | Units Analyzed | Denominator Units Selected | Arm/Group Information | Denominators | Classes | Analyses | |||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Primary | 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. | The sample size was determined by the one proportion formula where power = 0.8, d=0.02 , p= 0.5(primary outcome) and type I error probability associated with this test of null hypothesis is 0.05. The analysis was per protocol | Posted | Nov 2008 | Mean | Standard Deviation | diopter | six months after surgery | eyes | Participants |
|
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| ID | Title | Description | Deaths (Affected) | Deaths (At Risk) | Serious Events (Affected) | Serious Events (At Risk) | Other Events (Affected) | Other Events (At Risk) |
|---|---|---|---|---|---|---|---|---|
| EG000 | Cross-cylinder PRK | Right or left eye of 50 patients was randomly enrolled(data provided in this module refer to 50 eyes of 50 participants)to undergo PRK by cross-cylinder approach using Excimer laser.In this method , half of the cylinder is treated along the steepest meridian and the other half is ablated along the flattest meridian . |
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| Title | Organization | Phone | Extension | |
|---|---|---|---|---|
| Mohammad R sedghipour,MD | Tabriz University of Medical Sciences | +98 411 3306619 | sedghipm@yahoo.com |
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| ID | Term |
|---|---|
| D001251 | Astigmatism |
| ID | Term |
|---|---|
| D012030 | Refractive Errors |
| D005128 | Eye Diseases |
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| ID | Term |
|---|---|
| D018903 | Photorefractive Keratectomy |
| ID | Term |
|---|---|
| D048988 | Corneal Surgery, Laser |
| D053685 | Laser Therapy |
| D013812 | Therapeutics |
| D055011 | Ablation Techniques |
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|
| 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. | 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. | 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 | six months after surgery |
| Participants |
|
| Age Continuous | Mean | Standard Deviation | years |
|
| Sex: Female, Male | one eye of 39 females and 11 males underwent PRK by cross-cylinder approach and the other eye underwent PRK by single method | Count of Participants | Participants |
|
| Region of Enrollment | Number | participants |
|
| Target induced astigmatism(TIA) | It is vector of astigmatic change intended to be 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. | Mean | Standard Deviation | Diopter |
|
| 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.Participant population was the same as baseline population. It was 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. | Mean | Standard Deviation | diopter |
|
| corrected distance visual acuity | Corrected VA 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.LogMAR(logarithmic minimum angle of resolution)notation has gained widespread use in statistical calculations. | Mean | Standard Deviation | logMAR |
|
| high order aberration | Although lower- order aberrations decrease after laser vision correction,higher -order aberrations may increase after conventional PRK or lasik.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 for aberrometry which is one of the methods of wavefront analysis.Participant population was the same as baseline population. | Mean | Standard Deviation | micron |
|
| Spherical equivalent | Average of the maximum and minimum powers,which equals the sphere power plus half the cylinder power.Participant population was the same as baseline population. It was 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. | Mean | Standard Deviation | Diopter |
|
| uncorrected distance visual acuity | Uncorrected VA is attained before 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. | Mean | Standard Deviation | log MAR |
|
| OG001 | Single PRK | Right or left eye of 50 patients was randomly enrolled(data provided in this module refer to 50 eyes of 50 participants)to undergo PRK by single approach using Excimer laser.In this method ,the steepest meridian is treated by elliptical ablation to match the flattest meridian. |
|
|
|
| Secondary | 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 . | the analysis was per protocol. | Posted | Nov 2008 | Mean | Standard Deviation | micron | six months postoperative | eyes | Participants |
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|
| Secondary | 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. | the analysis was per protocol | Posted | Nov 2008 | Mean | Standard Deviation | LogMAR | six months | eyes | Participants |
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| Secondary | 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. | the analysis was per protocol | Posted | Nov 2008 | Mean | Standard Deviation | LogMAR | six months | eyes | Participants |
|
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| Secondary | 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 | Posted | Nov 2008 | Mean | Standard Deviation | Diopter | six months after surgery |
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| 0 |
| 48 |
| 0 |
| 48 |
| EG001 | Single PRK | Right or left eye of 50 patients was randomly enrolled(data provided in this module refer to 50 eyes of 50 participants)to undergo PRK by single approach using Excimer laser.In this method ,the steepest meridian is treated by elliptical ablation to match the flattest meridian. | 0 | 48 | 0 | 48 |
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| D013514 |
| Surgical Procedures, Operative |
| D000074431 | Keratectomy |
| D054140 | Refractive Surgical Procedures |
| D013508 | Ophthalmologic Surgical Procedures |