Ignite Creation Date:
2024-05-05 @ 5:28 PM
Last Modification Date:
2024-10-26 @ 9:32 AM
Study NCT ID:
NCT00466908
Status:
WITHDRAWN
Last Update Posted:
2018-06-06
First Post:
2007-04-25
Brief Title:
Accuracy of the Pentacam and IOL Master to Calculate the Effective Corneal Power After Corneal Refractive Surgery
Sponsor:
Medical University of South Carolina
Organization:
Medical University of South Carolina
Study Overview
Official Title:
Accuracy of the Pentacam and IOL Master to Calculate the Effective Corneal Power After Corneal Refractive Surgery
Status:
WITHDRAWN
Status Verified Date:
2010-10
Last Known Status:
None
Delayed Posting:
No
If Stopped, Why?:
Not Stopped
Has Expanded Access:
False
If Expanded Access, NCT#:
N/A
Has Expanded Access, NCT# Status:
N/A
Acronym:
None
Brief Summary:
The purpose of this study is to determine the accuracy of the Pentacam and IOL Master to calculate the effective corneal power keratometry corneal curvature in patients who have undergone both corneal refractive surgery and lens extraction with intraocular lens implantation
Detailed Description:
The accuracy of IOL calculation is important for the visual outcome of patients undergoing cataract extraction and IOL implantation Different formulas such as Holladay I HofferQ SRKT have been used with excellent results All formulas use the corneal power among other factors to calculate the IOL power Corneal refractive surgery ie radial keratotomy RK photorefractive keratectomy PRK and Laser in situ keratomileusis LASIK changes the corneal power therefore it is difficult to measure the true corneal power after surgery by any form of direct measurement such as keratometry or corneal topography Keratometry and topography assume a normal relationship between the anterior and posterior corneal curvatures and measure the anterior corneal radius RK for myopia flattens both the anterior corneal radius and the posterior corneal radius while PRK and LASIK for myopia flattens the anterior corneal radius but leaves the posterior corneal radius mostly unchanged
Standard keratometry measures an intermediate area and extrapolates the central power based on some very broad assumptions For this reason keratometry autokeratometry and simulated keratometry by topography will typically over-estimate central corneal power following keratorefractive surgery for myopia This inaccuracy leads to an inability to meet the patients rising expectations and with the increasing popularity of refractive surgery calculating intraocular lens IOL power after refractive surgery is becoming increasingly important
Different methods to calculate the effective corneal power keratometry after refractive surgery have been described historical data effective refractive power modified Maloney method etc however intraocular lens power calculations in eyes with previous refractive surgery remains difficult because of the inaccuracy of keratometry power measurements
The Pentacam Comprehensive Eye Scanner is a non-invasive diagnostic system created to take photographs of the anterior segment of the eye by a rotating Scheimpflug camera measurement This rotating process supplies pictures in three dimensions The center of the cornea is measured very precisely because of this rotational imaging process The measurement process lasts less than two seconds and minute eye movements are captured and corrected simultaneously By measuring 25000 true elevation points precise representation repeatability and analysis are guaranteed It provides a topographic analysis of the corneal front and back surfaces that is based on the true elevation measurement from limbus to limbus Both corneal surfaces can be selected for analysis in axial sagittal tangential or elevation representation modes
The Pentacam using tomography calculates a virtual model of the anterior segment of the eye It is possible to move zoom and rotate it to detect eg iris defects cornea incisions eg RK or size location and shape of opacifications in the crystalline lens The slicing function in the three dimensions offers a detailed view of the different layers of the eye It includes the Holladay report that was developed to improve the calculation of IOLs for patients which have undergone corneal refractive surgery
The IOL Master is a non-contact optical coherence biometry that makes possible the exact measurement of visual axis length Its accuracy is not affected by high ametropia pupil size or state of accommodation This non-contact technology makes it easy on the patient no local anesthesia water bath or contact probe For IOL power calculation after previous refractive corneal surgery one can derive the effective corneal power using either the clinical history method or the rigid contact lens over-refraction method It therefore permits selection of a suitable lens after myopic LASIKPRK without requiring refractive pre-LASIK data or additional contact lens over-refraction
The purpose of this study is to determine the accuracy of the Pentacam and IOL Master to calculate the effective corneal power keratometry corneal curvature in patients who have undergone both corneal refractive surgery and lens extraction with intraocular lens implantation
Standard keratometry measures an intermediate area and extrapolates the central power based on some very broad assumptions For this reason keratometry autokeratometry and simulated keratometry by topography will typically over-estimate central corneal power following keratorefractive surgery for myopia This inaccuracy leads to an inability to meet the patients rising expectations and with the increasing popularity of refractive surgery calculating intraocular lens IOL power after refractive surgery is becoming increasingly important
Different methods to calculate the effective corneal power keratometry after refractive surgery have been described historical data effective refractive power modified Maloney method etc however intraocular lens power calculations in eyes with previous refractive surgery remains difficult because of the inaccuracy of keratometry power measurements
The Pentacam Comprehensive Eye Scanner is a non-invasive diagnostic system created to take photographs of the anterior segment of the eye by a rotating Scheimpflug camera measurement This rotating process supplies pictures in three dimensions The center of the cornea is measured very precisely because of this rotational imaging process The measurement process lasts less than two seconds and minute eye movements are captured and corrected simultaneously By measuring 25000 true elevation points precise representation repeatability and analysis are guaranteed It provides a topographic analysis of the corneal front and back surfaces that is based on the true elevation measurement from limbus to limbus Both corneal surfaces can be selected for analysis in axial sagittal tangential or elevation representation modes
The Pentacam using tomography calculates a virtual model of the anterior segment of the eye It is possible to move zoom and rotate it to detect eg iris defects cornea incisions eg RK or size location and shape of opacifications in the crystalline lens The slicing function in the three dimensions offers a detailed view of the different layers of the eye It includes the Holladay report that was developed to improve the calculation of IOLs for patients which have undergone corneal refractive surgery
The IOL Master is a non-contact optical coherence biometry that makes possible the exact measurement of visual axis length Its accuracy is not affected by high ametropia pupil size or state of accommodation This non-contact technology makes it easy on the patient no local anesthesia water bath or contact probe For IOL power calculation after previous refractive corneal surgery one can derive the effective corneal power using either the clinical history method or the rigid contact lens over-refraction method It therefore permits selection of a suitable lens after myopic LASIKPRK without requiring refractive pre-LASIK data or additional contact lens over-refraction
The purpose of this study is to determine the accuracy of the Pentacam and IOL Master to calculate the effective corneal power keratometry corneal curvature in patients who have undergone both corneal refractive surgery and lens extraction with intraocular lens implantation
Study Oversight
Has Oversight DMC:
None
Is a FDA Regulated Drug?:
None
Is a FDA Regulated Device?:
None
Is an Unapproved Device?:
None
Is a PPSD?:
None
Is a US Export?:
None
Is an FDA AA801 Violation?:
None