CHOICE OF SUBJECTIVE OCULAR REFRACTION TECHNIQUE AND CORNEAL TOPOGRAPHY OF KERATOCONUS

Study Overview
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Brief Summary
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Keratoconus is a rare evolving corneal ectasia that alters visual acuity. To improve spectacle-corrected visual acuity, various subjective refraction techniques can be used. The subjective refraction techniques of keratoconus-carrying patients have never been studied. The main hypothesis is that the most suitable subjective ocular refraction method varies with the corneal topography of the keratoconus. The main objective is to define the most appropriate refractive technique(s) based on corneal topographies in order to provide keratoconus-affected patients with the best spectacle-corrected visual acuity.

Detailed Description
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Keratoconus is a rare evolving corneal ectasia that alters visual acuity. To improve spectacle-corrected visual acuity, various subjective refraction techniques can be used. The Jackson Cylinder Cross Method, the Astigmatic Dial Technique and the Stenopeic Slit are three validated subjective refraction techniques for measuring astigmatism. The subjective refraction techniques of keratoconus-carrying patients have never been studied. The main hypothesis is that the most suitable subjective ocular refraction method varies with the corneal topography of the keratoconus. The investigators collect several characteristics of corneal topography of the keratoconus : the average value of the keratometry of the 3 central mm called Km ; the value of the point corresponding to the maximum keratometry (called Kmax), the distance between the center and the point of Kmax, (called d_Kmax) ; the corneal surface variance index called ISV ; the Belin/Ambrósio Enhanced Ectasia Display (called BAD-D). The main objective is to define the most appropriate refractive technique(s) based on corneal topographies in order to provide keratoconus-affected patients with the best spectacle-corrected visual acuity.

Official Title
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CHOICE OF SUBJECTIVE OCULAR REFRACTION TECHNIQUE AND CORNEAL TOPOGRAPHY OF KERATOCONUS

Conditions
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Keratoconus, Alteration of Visual Acuity

Intervention / Treatment
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* Behavioral: Cylinder
* Behavioral: Dial
* Behavioral: Slit


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: adult persons patients with keratoconus patients with alteration of visual acuity ability to give informed consent to participate in the study affiliation to a social security scheme Exclusion Criteria: Keratoconus grafted with cornea or with intracorneal rings. Central corneal opacities. Presence of other eye diseases affecting visual acuity. Patients under guardianship, curatorship or justice protection. Pregnant or breastfeeding women. Refusal to participate in the study.

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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Design Details

Primary Purpose: Treatment
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Cohort 1<br>70 patients are involved and will perform the three conditions. | Behavioral: Cylinder<br>* Patients who receive the Jackson Cross Cylinder Method<br>Behavioral: Dial<br>* Patients who receive the Astigmatic Dial Technique Method.<br>Behavioral: Slit<br>* Patients who receive the Stenopeic slit Method.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Measure of keratometry (Km) | average value of the keratometry of the 3 central mm called Km | day 1 | 
| Measure of the maximum keratometry | value of the point corresponding to the maximum keratometry (called Kmax), | day 1 | 
| Measure d_Kmax | Measure of the distance between the center and the point of Kmax, (called d_Kmax) | day 1 | 
| Measure of index of surface varaiance | measure of the corneal surface variance index called ISV | day 1 | 
| Measure of the Belin/Ambrósio Enhanced Ectasia Display (BAD-D) | Measure of the Belin/Ambrósio Enhanced Ectasia Display (BAD-D) | day 1 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| astigmatism axis | Collection of the astigmatism axis given by each method, by the autorefractometer and by the corneal topography | day 1 | 
| Subsequent modification of the eyeglasses by the optician | The need (yes / no) for the optician to modify the prescribed spectacle lens (due to poor tolerance) | day 30 | 
| possible method | The impossibility (yes / no) of carrying out each of the 3 refraction methods. | day 1 | 
| ametropia value | The values of the final corrective spheres (myopia or hyperopia). | day 1 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Keratoconus, Corneal Topography, Eyeglasses, Ocular Refraction, Jackson Cross Cylinder, Astigmatic Dial Technique, Stenopeic slit