Retrospective Observational Study of Posterior Keratometry Measured

Study Overview
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Brief Summary
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Keratoconus is a progressive bilateral disease leading to an apical stromal thinning and an irregular astigmatism by a steepening of the cornea, causing visual impairment. The causes are not yet well known, but it seems to be linked to several comorbidities. Keratoconus is a rare and for a long-time asymptomatic condition and its diagnosis needs meticulous screening for the early stages. Detecting it as soon as possible is a goal as it could lead to earlier avoiding of contributing factors such as eye rubbing and earlier treatment if needed. The gold standard for keratoconus screening and staging is computerized videotography. It gives information about anterior and posterior corneal bulging, steepening, and thinning. It can be completed by anterior segment optical coherence tomography, which can show corneal scarring. Since recently, some biometry devices can give some information about the posterior corneal keratometry trough swept source optical coherence tomography measures. The measurement of the total corneal power instead of an extrapolation lead to better precision in refractive results after cataract surgery in some cases. It also helped to increase our knowledge about posterior corneal astigmatism. In normal eyes, average posterior corneal astigmatism is 0.37 diopters and against the rule in 91 percent of eyes. There is a correlation between the magnitude of anterior and posterior astigmatism. In keratoconus eyes, several studies have shown that there is an alignment between axes of the anterior and posterior corneal astigmatism. These studies have been performed on computerized videotopography devices. The goal of this study was to confirm or deny previous observations about posterior astigmatism in keratoconus eyes, and to assess if the rotation of axis between anterior and posterior astigmatism measured by IOL Master 700® can be a good sign for detection of early stages and fruste keratoconus.

Official Title
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Retrospective Observational Study of Posterior Keratometry Measured by IOLMaster 700 in Patients With Keratoconus

Conditions
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Keratoconus

Participation Criteria
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Eligibility Criteria
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Inclusion criteria: - Keratoconus diagnosed on videotopography Exclusion criteria: - loss of sight due to another condition than keratoconus, corneal scarring leading to lack or mistaken data, corneal graft, non-keratoconus related corneal ectasia such as post Laser in Situ Keratomileusis (LASIK) ectasia or keratoglobus

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Keratoconus patient<br>Patient with keratoconus disease diagnosed on videotopography | |
| Healthy patient<br>Patient consulting for keratoconus screening with no keratoconus on videotopography | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Posterior keratometry | Posterior cylinder and axis measured on biometry | 1 day | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Total keratometry | Total corneal power (cylinder and axis) measured on biometrycompleted by the patient | 1 day | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Ophthalmology, Keratoconus