Refractive Errors
Conditions
Brief summary
Wavefront scans are a common form of diagnostic test applied in preparing patients for laser eye surgery. An optical map of the eye is created by wavefront scanning, and information from these maps is used to program lasers used to correct focusing errors in the eye. Here the investigators are comparing how repeatable measurements are with a new wavefront scanner and one that is already in widespread use.
Detailed description
Aberrometers are used to measure each element of defocus (aberration) in an optical system. In LASIK, information derived from aberrometry (scans performed using aberrometers) is used to program the pattern of laser pulses delivered by an excimer laser in therapeutic reshaping of the cornea to correct defocus. To do this accurately, aberrometry findings need to be repeatable and correspond closely to manifest refraction. Here the investigators compare repeatability of measurements for a new aberrometer (Peramis) versus the aberrometer most widely used in contemporary wavefront guided laser vision correction (iDesign). The test aberrometer will be: Peramis (Schwind Eye-tech Solutions, Kleinostheim, Germany). Control aberrometer will be: iDesign (AMO, Santa Clara, CA)
Interventions
DEVICEPeramis aberrometry
A non-invasive photographic scan sequence acquired in under 10 seconds
DEVICEiDesign aberrometry
A non-invasive photographic scan sequence acquired in under 10 seconds
Sponsors
Moorfields Eye Hospital NHS Foundation Trust
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
DIAGNOSTIC
Masking
SINGLE (Investigator)
Eligibility
Sex/Gender
ALL
Age
21 Years to 60 Years
Healthy volunteers
No
Inclusion criteria
* Myopic LASIK candidates (manifest refraction spherical equivalent range 0 to -10 diopters with up to 6 diopters cylinder) or patients attending corneal service with stage II-III keratoconus or post-keratoplasty
Exclusion criteria
* Visually significant co-pathology (CDVA\<6/6) other than irregular astigmatism; * Patients unable to complete a sequence of 2 good scans (acquisition diameter \>5mm) in one eye within 4 attempts
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| 2nd to 4th order aberrations (5mm pupil). | <10 seconds | M, J0, J45, Coma, Trefoil, Spherical Aberration. Different types of defocus or aberration can be defined and measured by wavefront scanning. Aberrations are classified and quantified by a mathematical treatment called Zernike analysis in which harmonic elements of the waveform of the light detected by the wavefront sensor (aberrometer) are quantified in sequence, starting with simple (lower order) waveforms such as sphere and cylinder (M, J0, J45) corrected in a normal spectacle prescription, and progressing through more complex (higher order) waveforms including, coma, trefoil and spherical aberration which may influence quality of vision. The amount of each aberration varies as a function of pupil size. So pupil size is standardised at 5mm diameter for quantification. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| % of patients with qualifying scan sequence | <5 minutes | % of patients in whom two 5mm diameter aberrometry scans can be acquired within 4 attempts |
Contacts
Primary ContactAngelique Thomas
Backup ContactBarbara Stacey
Outcome results
None listed