Trial Outcomes & Findings for Comparison of Cross-cylinder and Conventional Photorefractive Keratectomy(PRK) in Correcting Medium-high Astigmatism (NCT NCT00663923)

Last Updated: 2012-03-13

Results Overview

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.

Recruitment status

COMPLETED

Study phase

PHASE3

Target enrollment

50 participants

Primary outcome timeframe

six months after surgery

Results posted on

2012-03-13

Participant Flow

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

All enrolled patients having inclusion criteria accepted both available techniques for correction of astigmatism.

Participant milestones

Participant milestones
Measure	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.
Overall Study STARTED	50
Overall Study COMPLETED	48
Overall Study NOT COMPLETED	2

Reasons for withdrawal

Reasons for withdrawal
Measure	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.
Overall Study Lost to Follow-up	2

Baseline Characteristics

Comparison of Cross-cylinder and Conventional Photorefractive Keratectomy(PRK) in Correcting Medium-high Astigmatism

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	Photorefractive Keratectomy( PRK) n=50 Participants 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.
Age, Categorical <=18 years	0 Participants n=5 Participants
Age, Categorical Between 18 and 65 years	50 Participants n=5 Participants
Age, Categorical >=65 years	0 Participants n=5 Participants
Age Continuous	28.46 years STANDARD_DEVIATION 7.05 • n=5 Participants
Sex: Female, Male Female	39 Participants n=5 Participants
Sex: Female, Male Male	11 Participants n=5 Participants
Region of Enrollment Iran, Islamic Republic of	50 participants n=5 Participants
Target induced astigmatism(TIA)	1.86 Diopter STANDARD_DEVIATION 0.60 • n=5 Participants
astigmatism	-2.49 diopter STANDARD_DEVIATION 0.83 • n=5 Participants
corrected distance visual acuity	0.06 logMAR STANDARD_DEVIATION 0.11 • n=5 Participants
high order aberration	0.36 micron STANDARD_DEVIATION 0.10 • n=5 Participants
Spherical equivalent	-5.19 Diopter STANDARD_DEVIATION 2.47 • n=5 Participants
uncorrected distance visual acuity	1.11 log MAR STANDARD_DEVIATION 0.36 • n=5 Participants

PRIMARY outcome

Timeframe: six months after surgery

Population: 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

Outcome measures

Outcome measures
Measure	Cross-cylinder PRK n=48 eyes 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 .	Single PRK n=48 eyes 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.
Correction of Astigmatism	-0.54 diopter Standard Deviation 0.43	-0.59 diopter Standard Deviation 0.33

SECONDARY outcome

Timeframe: six months postoperative

Population: the analysis was per protocol.

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 .

Outcome measures

Outcome measures
Measure	Cross-cylinder PRK n=42 eyes 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 .	Single PRK n=42 eyes 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.
Higher Order Aberrations	0.51 micron Standard Deviation 0.21	0.51 micron Standard Deviation 0.20

SECONDARY outcome

Timeframe: six months

Population: the analysis was per protocol

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.

Outcome measures

Outcome measures
Measure	Cross-cylinder PRK n=48 eyes 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 .	Single PRK n=48 eyes 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.
Corrected Distance Visual Acuity(CDVA)	0.02 LogMAR Standard Deviation 0.02	0.03 LogMAR Standard Deviation 0.03

SECONDARY outcome

Timeframe: six months

Population: the analysis was per protocol

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.

Outcome measures

Outcome measures
Measure	Cross-cylinder PRK n=48 eyes 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 .	Single PRK n=48 eyes 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.
Uncorrected Distance Visual Acuity (UCDVA)	0.08 LogMAR Standard Deviation 0.15	0.10 LogMAR Standard Deviation 0.16

SECONDARY outcome

Timeframe: six months after surgery

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

Outcome measures

Outcome measures
Measure	Cross-cylinder PRK n=48 Participants 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 .	Single PRK n=48 Participants 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.
Surgically Induced Astigmatism	1.98 Diopter Standard Deviation 0.57	1.51 Diopter Standard Deviation 0.43

Adverse Events

Cross-cylinder PRK

Serious events: 0 serious events

Other events: 0 other events

Deaths: 0 deaths

Single PRK

Serious events: 0 serious events

Other events: 0 other events

Deaths: 0 deaths

Serious adverse events

Adverse event data not reported

Other adverse events

Adverse event data not reported

Additional Information

Mohammad R sedghipour,MD

Tabriz University of Medical Sciences

Phone: +98 411 3306619

Email: [email protected]

Results disclosure agreements

Principal investigator is a sponsor employee
Publication restrictions are in place