Astigmatic Vector Analysis of Posterior Cornea - a Comparison Among Healthy, Forme Fruste and Overt Keratoconus Corneas

February 29, 2016 updated by: Giuliano de Oliveira Freitas, MD., University of Sao Paulo

Astigmatic Vector Analysis of Posterior Corneal Surface - a Comparison Among Healthy, Forme Fruste and Overt Keratoconus Corneas

The main purpose of this study is to determine new diagnostic criteria for an eye disease called keratoconus.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

Eyes of patients who distinctly present signs of keratoconus, for both eyes, at corneal tomography (an exam commonly used in such cases), and those who present such signs in only one eye were compared to eyes of unaffected patients. Several characteristics of anterior and posterior corneal astigmatism (special emphasis was given to the latter) were collectively assessed among all patients by a method referred to as vectorial analysis. Statistical tests were then performed, in an attempt to highlight differences among those three groups of patients and, eventually, define new diagnostic criteria.

Study Type

Observational

Enrollment (Actual)

698

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Brazil
      • São Paulo, Brazil, 05.403-001
        • Clínica Oftalmológica do Hospital de Clínicas - FMUSP

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Child
  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Sampling Method

Probability Sample

Study Population

Two databases of patients were examined at the Instituto de Olhos Renato Ambrósio (Rio de Janeiro, Brazil), between July 2004 and October 2013. One of the databases contained information of normal candidates to refractive surgery who did not develop any sign of corneal ectasia after laser in situ keratomileusis during a two year follow-up period (C). The second database included information concerning corneas with keratoconus (Kc), categorized as overt Kc, if both eyes manifested classic Kc-suggestive topographic features, such as corneal steepness higher than 47.20 diopters (D), superior-inferior asymmetry higher than 1.40 D and thinnest pachymetric reading lower than 500 micrometers; or forme fruste (FFKc), if only one eye exhibited such features.

Description

Inclusion Criteria:

  • Good-quality Scheimpflug scans (approved by the device in the ''Examination Quality Specification'').

Exclusion Criteria:

  • Previous eye surgery or trauma, and any sort of corneal scarring that might interfere with keratometric data acquisition.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Observational Models: Case-Control
  • Time Perspectives: Retrospective

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Healthy corneas (C)
Corneas of normal candidates to refractive surgery who did not develop any sign of corneal ectasia after laser in situ keratomileusis during a two year follow-up period were analyzed by an Scheimpflug-based tomographer. Vector astigmatism analysis of anterior and posterior corneal surfaces were studied in accordance to method proposed by Thibos.
Other: Analysis of anterior and posterior corneal surfaces
Corneal data obtained from a Scheimpflug-based topographer were converted to astigmatic vectors in accordance to the method proposed by Thibos
Other Names:
  • Thibos' vectorial astigmatism analysis
Overt keratoconus (Kc)
Whether both eyes manifested classic Kc-suggestive topographic features, such as corneal steepness higher than 47.20 diopters (D), superior-inferior asymmetry higher than 1.40 D and thinnest pachymetric reading lower than 500 micrometers. Such eyes were analyzed by an Scheimpflug-based tomographer. Vector astigmatism analysis of anterior and posterior corneal surfaces were studied in accordance to method proposed by Thibos.
Other: Analysis of anterior and posterior corneal surfaces
Corneal data obtained from a Scheimpflug-based topographer were converted to astigmatic vectors in accordance to the method proposed by Thibos
Other Names:
  • Thibos' vectorial astigmatism analysis
Forme fruste keratoconus (FFKc)
Whether only one eye manifested classic Kc-suggestive topographic features, such as corneal steepness higher than 47.20 diopters (D), superior-inferior asymmetry higher than 1.40 D and thinnest pachymetric reading lower than 500 micrometers, and the fellow eye seemed unaffected. Such unaffected eyes were analyzed by an Scheimpflug-based tomographer. Vector astigmatism analysis of anterior and posterior corneal surfaces were studied in accordance to method proposed by Thibos.
Other: Analysis of anterior and posterior corneal surfaces
Corneal data obtained from a Scheimpflug-based topographer were converted to astigmatic vectors in accordance to the method proposed by Thibos
Other Names:
  • Thibos' vectorial astigmatism analysis

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Astigmatism corneal vectors (based on keratometric readings at the three millimeter optical zones for both corneal surfaces).
Time Frame: Through study completion, an average of 6 months.
Corneal tomography at an Scheimpflug-based tomographer
Through study completion, an average of 6 months.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Sao Paulo

Investigators

  • Study Director: Milton R Alves, MD, PhD, Clínica Oftalmológica HCFM/USP

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start

May 1, 2015

Primary Completion (Actual)

August 1, 2015

Study Completion (Actual)

September 1, 2015

Study Registration Dates

First Submitted

February 24, 2016

First Submitted That Met QC Criteria

February 29, 2016

First Posted (Estimate)

March 4, 2016

Study Record Updates

Last Update Posted (Estimate)

March 4, 2016

Last Update Submitted That Met QC Criteria

February 29, 2016

Last Verified

February 1, 2016

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • Clínica Oftalmológica HCFM/USP

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

Clinical Trials on Keratoconus

Clinical Trials on Analysis of anterior and posterior corneal surfaces

Search Similar Trials

Sponsors and Collaborators

Medical Conditions

Drug Interventions

CROs by country

CROs in Equatorial Guinea

Conditions

Rare Diseases

Drug Interventions

Dietary Supplements

Sponsor/Collaborators

Locations

Subscribe