Astigmatic Vector Analysis of Posterior Cornea - a Comparison Among Healthy, Forme Fruste and Overt Keratoconus Corneas
Study Details
Study Description
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 | Phase |
|---|---|---|
|
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 Design
Arms and Interventions
| Arm | 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:
|
| 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:
|
| 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:
|
Outcome Measures
Primary Outcome Measures
- Astigmatism corneal vectors (based on keratometric readings at the three millimeter optical zones for both corneal surfaces). [Through study completion, an average of 6 months.]
Corneal tomography at an Scheimpflug-based tomographer
Eligibility Criteria
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.
Contacts and Locations
Locations
| Site | City | State | Country | Postal Code | |
|---|---|---|---|---|---|
| 1 | 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
Study Documents (Full-Text)
None provided.More Information
Publications
None provided.- Clínica Oftalmológica HCFM/USP