Corneal AstigmatismNCT04393740
Contribution of Posterior Corneal Astigmatism to Total Corneal Astigmatism in a Sample of Egyptian Population
An observational study of Corneal Astigmatism, run by Cairo University at 1 site in Egypt.
Trial summary
The magnitude of posterior corneal astigmatism was considered negligible due to the smaller difference in the refractive index between the cornea and the aqueous . though ,neglecting the posterior corneal astigmatism lead to errors during calculation of the toric iols (over or under estimation ) . Read more about this study
- Who is it for?
- Ages 18 to 45 yearsHealthy volunteers can take part
- Conditions the study is for
- Corneal Astigmatism
- What is being tested?
- scheimpflug imaging using pentacam
- How many people
- 356 participants
- Where
- 1 siteEgypt
- Study dates
- 15 Apr 2020to 15 Aug 2020
- 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 18 to 45 years
- All sexes
- Healthy volunteers accepted
- Adult
Study population: candidates presenting for refractive surgery .
Who may be able to join
- Patients with corneal astigmatism(±0.5D up tp ±4 D )
- Age (18-45 years )
- Refractive error (myopia up to -8D)
- Hyperopia up to +4
- Patients who have clear cornea .
- Good quality Scheimpflug analyzer scans.
Who cannot join
- Patients who have any corneal opacity .
- Patients who underwent any Previous corneal surgery .
- Patients who have Co existing corneal pathology.
- Glaucomatus patients.
- Patients with any Concomitant ocular disease .
- Patients with History of previous ocular trauma .
Trial locations and contacts
1 site in 1 country.
Egypt1 site, 1 recruiting
- Recruiting
kasr El Aini medical school
Cairo
alaa MO badawy, Msc, 0100858267 ext. +20, alaabadawy93@gmail.com
sarah A Azzam, MD, 01227425601 ext. +20, Sarahazzam@ymail.com
About this study
Official title: The Contribution of Posterior Corneal Astigmatism to Total Corneal Astigmatism Using Scheimpflug Analyzer (Pentacam ) in a Sample of Egyptian Population
The magnitude of posterior corneal astigmatism was considered negligible due to the smaller difference in the refractive index between the cornea and the aqueous .
though ,neglecting the posterior corneal astigmatism lead to errors during calculation of the toric iols (over or under estimation ) .
so we aim to determine the percentage of contribution of posterior corneal astigmatism to total corneal astigmatism in a sample of Egyptian population using scheimpflug imaging (Pentacam ).
Read the detailed description
Astigmatism is a common vision condition that causes blurred vision. Astigmatism is an error of refraction in which incident parallel rays can't be focused to a single point .It could be corneal or lenticular astigmatism or both . Regarding Corneal astigmatism it is due to difference in the corneal curvature in the different meridian of both the anterior and posterior surface .
The are 2 methods of studing corneal curvature :
- Corneal topography which depend on placcido disc to study anterior corneal surface .
- Corneal tomography is more precise in detecting anterior and posterior corneal curvature depending on Scheimpflug principle which uses a rotating Scheimpflug camera .
Pentacam is a device which depend on Scheimpflug technique .
The importance of studing the posterior corneal curvature includes :
- The posterior corneal curvature is a more sensitive indicator of early keratoconus detection especially posterior corneal elevation.
Previously, The change in the posterior corneal surface plays a more subtle role than the anterior corneal surface in optical performance because of the smaller difference in refractive indices between the cornea and aqueous, and it has been thought that the magnitude of PCA in the normal population is clinically negligible.
Posterior corneal astigmatism (PCA) is important for better predictability of toric intraocular lens calculation to avoid under- or overestimation of toricity in intraocular lens (IOL) power calculations.
But recently it has been demonstrated how neglecting PCA will lead to overcorrection of astigmatism in eyes with with-the-rule astigmatism (WTR) and undercorrection in eyes with against-the-rule astigmatism (ATR).(3) In our study we aim to Determine the contribution of posterior corneal astigmatism to total corneal astigmatism and the error in estimating total corneal astigmatism from anterior corneal measurements only using Scheimpflug analyzer (Pentacam ).
Our patients will undergo Scheimpflug imaging using pentacam .
From the corneal parameters displayed in pentacam we can calculate :
- Anterior corneal astigmatism by substracting Ksteep -Kflat on the front surface
- Posterior corneal astigmatism by substracting Ksteep-Kflat on the back surface.
- Total corneal astigmatism is calculated by addition of anterior and posterior corneal astigmatism using vector analysis by using ASSORT vector calculator.*
- The percentage of contribution of posterior corneal astigmatism to magnitude of Total corneal astigmatism is then calculated .
ASSORT vector calculator:
Is a total planning and outcomes analysis software for astigmatism using Alpins method ,cheltman ,Victoria ,Australia .
- Conditions
- Corneal Astigmatism
- Being tested
- scheimpflug imaging using pentacam
- Medical subject headings
- Astigmatism
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
scheimpflug imaging using pentacamDiagnostic test
corneal tomography imaging using pentacam device (based on Scheimpflug principle )
What is being measured
The primary outcome is the main question the study is designed to answer.
contribution of posterior corneal astigmatism to magnitude of total corneal astigmatism
to detect the contribution of posterior corneal astigmatism to total corneal astigmatism to avoid errors during calculation of toric Intra ocular lenses
Measured: 3 months
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted19 May 2020
- Study start15 Apr 2020
- Primary completion15 Jul 2020 (estimated)
- Study completion15 Aug 2020 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (2)Papers the sponsor has linked to this study.
- Other trials for Corneal AstigmatismStudies of the same condition, open and under way.
- More trials run by Cairo UniversityThe 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
- Cohort
- Time perspective
- Cross-sectional
- Enrolment
- 356 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Cairo University
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Alaa Mohamed Badawy, Cairo University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04393740
- Sponsor's protocol ID
- Ms-184-2019
- Status last verified
- May 2020
- First submitted
- 14 May 2020
- Last updated
- 19 May 2020
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- Yes
- Individual data sharing
- Yes: we would share our protocol and results through publishing our research
Publications
Ferreira TB, Ribeiro P, Ribeiro FJ, O'Neill JG. Comparison of Methodologies Using Estimated or Measured Values of Total Corneal Astigmatism for Toric Intraocular Lens Power Calculation. J Refract Surg. 2017 Dec 1;33(12):794-800. doi: 10.3928/1081597X-20171004-03.
PubMed 29227506Rydstrom E, Westin O, Koskela T, Behndig A. Posterior corneal astigmatism in refractive lens exchange surgery. Acta Ophthalmol. 2016 May;94(3):295-300. doi: 10.1111/aos.12965. Epub 2016 Jan 30.
PubMed 26825986
Study at a glance
From the registry record, last updated by the sponsor on 19 May 2020. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The Contribution of Posterior Corneal Astigmatism to Total Corneal Astigmatism Using Scheimpflug Analyzer (Pentacam ) in a Sample of Egyptian Population
- ClinicalTrials.gov ID
- NCT04393740
- Acronym / sponsor ID
- Ms-184-2019
- Conditions
- Corneal Astigmatism
- Study type
- Observational
- Recruitment status
- Unknown status
- Enrolment
- 356 participants (estimated)
- Lead sponsor
- Cairo UniversityUniversity, hospital or other
- Study start
- 15 Apr 2020 (actual)
- Primary completion
- 15 Jul 2020 (estimated)
- Study completion
- 15 Aug 2020 (estimated)
- First posted
- 19 May 2020 (actual)
- 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.
The magnitude of posterior corneal astigmatism was considered negligible due to the smaller difference in the refractive index between the cornea and the aqueous .
though ,neglecting the posterior corneal astigmatism lead to errors during calculation of the toric iols (over or under estimation ) .
so we aim to determine the percentage of contribution of posterior corneal astigmatism to total corneal astigmatism in a sample of Egyptian population using scheimpflug imaging (Pentacam ).
Detailed description
Astigmatism is a common vision condition that causes blurred vision. Astigmatism is an error of refraction in which incident parallel rays can't be focused to a single point .It could be corneal or lenticular astigmatism or both . Regarding Corneal astigmatism it is due to difference in the corneal curvature in the different meridian of both the anterior and posterior surface .
The are 2 methods of studing corneal curvature :
- Corneal topography which depend on placcido disc to study anterior corneal surface .
- Corneal tomography is more precise in detecting anterior and posterior corneal curvature depending on Scheimpflug principle which uses a rotating Scheimpflug camera .
Pentacam is a device which depend on Scheimpflug technique .
The importance of studing the posterior corneal curvature includes :
- The posterior corneal curvature is a more sensitive indicator of early keratoconus detection especially posterior corneal elevation.
Previously, The change in the posterior corneal surface plays a more subtle role than the anterior corneal surface in optical performance because of the smaller difference in refractive indices between the cornea and aqueous, and it has been thought that the magnitude of PCA in the normal population is clinically negligible.
Posterior corneal astigmatism (PCA) is important for better predictability of toric intraocular lens calculation to avoid under- or overestimation of toricity in intraocular lens (IOL) power calculations.
But recently it has been demonstrated how neglecting PCA will lead to overcorrection of astigmatism in eyes with with-the-rule astigmatism (WTR) and undercorrection in eyes with against-the-rule astigmatism (ATR).(3) In our study we aim to Determine the contribution of posterior corneal astigmatism to total corneal astigmatism and the error in estimating total corneal astigmatism from anterior corneal measurements only using Scheimpflug analyzer (Pentacam ).
Our patients will undergo Scheimpflug imaging using pentacam .
From the corneal parameters displayed in pentacam we can calculate :
- Anterior corneal astigmatism by substracting Ksteep -Kflat on the front surface
- Posterior corneal astigmatism by substracting Ksteep-Kflat on the back surface.
- Total corneal astigmatism is calculated by addition of anterior and posterior corneal astigmatism using vector analysis by using ASSORT vector calculator.*
- The percentage of contribution of posterior corneal astigmatism to magnitude of Total corneal astigmatism is then calculated .
ASSORT vector calculator:
Is a total planning and outcomes analysis software for astigmatism using Alpins method ,cheltman ,Victoria ,Australia .
Study design
- Observational model
- Cohort
- Time perspective
- Cross-sectional
Who may qualify
- Ages
- 18 to 45 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
- Study population
- candidates presenting for refractive surgery .
Key inclusion criteria (6 listed)
- Patients with corneal astigmatism(±0.5D up tp ±4 D )
- Age (18-45 years )
- Refractive error (myopia up to -8D)
- Hyperopia up to +4
- Patients who have clear cornea .
Key exclusion criteria (6 listed)
- Patients who have any corneal opacity .
- Patients who underwent any Previous corneal surgery .
- Patients who have Co existing corneal pathology.
- Glaucomatus patients.
- Patients with any Concomitant ocular 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 |
|---|---|---|
| scheimpflug imaging using pentacamcorneal tomography imaging using pentacam device (based on Scheimpflug principle ) | Diagnostic test | – |
Primary outcome
contribution of posterior corneal astigmatism to magnitude of total corneal astigmatism
Time frame: 3 months
to detect the contribution of posterior corneal astigmatism to total corneal astigmatism to avoid errors during calculation of toric Intra ocular lenses
Results and safety
Results are not available in the source record.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 19 May 2020.
- Background: PubMed 29227506Ferreira TB, Ribeiro P, Ribeiro FJ, O'Neill JG. Comparison of Methodologies Using Estimated or Measured Values of Total Corneal Astigmatism for Toric Intraocular Lens Power Calculation. J Refract Surg. 2017 Dec 1;33(12):794-800. doi: 10.3928/1081597X-20171004-03.
- Background: PubMed 26825986Rydstrom E, Westin O, Koskela T, Behndig A. Posterior corneal astigmatism in refractive lens exchange surgery. Acta Ophthalmol. 2016 May;94(3):295-300. doi: 10.1111/aos.12965. Epub 2016 Jan 30.
- Individual participant dataSharing planned: Yes. we would share our protocol and results through publishing our research
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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.
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 Corneal Astigmatism, run by Cairo University at 1 site in Egypt.
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 6 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 19 May 2020. 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 Egypt. 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 alaa mo badawy, Msc (01008858267 ext. +20, alaabadawy93@gmail.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
contribution of posterior corneal astigmatism to magnitude of total corneal astigmatism (time frame: 3 months). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT04393740, which also lists 2 linked publications.
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 19 May 2020.