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

University of Sao Paulo

Status: Completed

Conditions: Keratoconus

Treatments: Other: Analysis of anterior and posterior corneal surfaces

Study type: Observational

Funder types: Other

Identifiers

NCT02698709

Clínica Oftalmológica HCFM/USP

Details and patient eligibility

About

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

Full 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.

Enrollment: 698 patients

Sex: All

Volunteers: No Healthy Volunteers

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.

Trial design

698 participants in 3 patient groups

Healthy corneas (C)

Description:

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.

Treatment:

Other: Analysis of anterior and posterior corneal surfaces

Overt keratoconus (Kc)

Description:

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.

Treatment:

Other: Analysis of anterior and posterior corneal surfaces

Forme fruste keratoconus (FFKc)

Description:

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.

Treatment:

Other: Analysis of anterior and posterior corneal surfaces