Keratoconus, Alteration of Visual Acuity
Conditions
Keywords
Keratoconus, Corneal Topography, Eyeglasses, Ocular Refraction, Jackson Cross Cylinder, Astigmatic Dial Technique, Stenopeic slit
Brief summary
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
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.
Interventions
BEHAVIORALCylinder
Patients who receive the Jackson Cross Cylinder Method
BEHAVIORALDial
Patients who receive the Astigmatic Dial Technique Method.
BEHAVIORALSlit
Patients who receive the Stenopeic slit Method.
Sponsors
University Hospital, Clermont-Ferrand
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
TREATMENT
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
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.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Measure of the Belin/Ambrósio Enhanced Ectasia Display (BAD-D) | day 1 | Measure of the Belin/Ambrósio Enhanced Ectasia Display (BAD-D) |
| Measure of the maximum keratometry | day 1 | value of the point corresponding to the maximum keratometry (called Kmax), |
| Measure d_Kmax | day 1 | Measure of the distance between the center and the point of Kmax, (called d\_Kmax) |
| Measure of keratometry (Km) | day 1 | average value of the keratometry of the 3 central mm called Km |
| Measure of index of surface varaiance | day 1 | measure of the corneal surface variance index called ISV |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Subsequent modification of the eyeglasses by the optician | day 30 | The need (yes / no) for the optician to modify the prescribed spectacle lens (due to poor tolerance) |
| possible method | day 1 | The impossibility (yes / no) of carrying out each of the 3 refraction methods. |
| ametropia value | day 1 | The values of the final corrective spheres (myopia or hyperopia). |
| astigmatism axis | day 1 | Collection of the astigmatism axis given by each method, by the autorefractometer and by the corneal topography |
Countries
France
Outcome results
None listed