ClinicalTrials.gov
ClinicalTrials.gov Menu

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

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details.
ClinicalTrials.gov Identifier: NCT02698709
Recruitment Status : Completed
First Posted : March 4, 2016
Last Update Posted : March 4, 2016
Sponsor:
Information provided by (Responsible Party):
Giuliano de Oliveira Freitas, MD., University of Sao Paulo

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

Condition or disease Intervention/treatment
Keratoconus Other: Analysis of anterior and posterior corneal surfaces

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
Actual Enrollment : 698 participants
Observational Model: Case Control
Time Perspective: Retrospective
Official Title: Astigmatic Vector Analysis of Posterior Corneal Surface - a Comparison Among Healthy, Forme Fruste and Overt Keratoconus Corneas
Study Start Date : May 2015
Actual Primary Completion Date : August 2015
Actual Study Completion Date : September 2015

Resource links provided by the National Library of Medicine


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 Name: 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 Name: 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 Name: Thibos' vectorial astigmatism analysis




Primary Outcome Measures :
  1. 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



Information from the National Library of Medicine

Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the contacts provided below. For general information, Learn About Clinical Studies.


Ages Eligible for Study:   Child, Adult, Older Adult
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No
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.
Criteria

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.

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT02698709


Locations
Brazil
Clínica Oftalmológica do Hospital de Clínicas - FMUSP
São Paulo, Brazil, 05.403-001
Sponsors and Collaborators
University of Sao Paulo
Investigators
Study Director: Milton R Alves, MD, PhD Clínica Oftalmológica HCFM/USP

Publications of Results:

Responsible Party: Giuliano de Oliveira Freitas, MD., MD, University of Sao Paulo
ClinicalTrials.gov Identifier: NCT02698709     History of Changes
Other Study ID Numbers: Clínica Oftalmológica HCFM/USP
First Posted: March 4, 2016    Key Record Dates
Last Update Posted: March 4, 2016
Last Verified: February 2016
Individual Participant Data (IPD) Sharing Statement:
Plan to Share IPD: No

Keywords provided by Giuliano de Oliveira Freitas, MD., University of Sao Paulo:
Keratoconus
Corneal Topography
Diagnosis
Keratomileusis, Laser In Situ

Additional relevant MeSH terms:
Keratoconus
Corneal Diseases
Eye Diseases