Patients With Myopic Spherical Equivalent up to -12 Diopters
Conditions
Keywords
Femtosecond LASIK, Q value, Wave-front Optimized (WFO)
Brief summary
Corneal asphericity is expressed numerically as the Q-value. A minus value means that corneal curvature flattens towards the periphery and the cornea is prolate in shape, but when the curvature steepens towards the periphery, the cornea is oblate in shape and has a positive Q-value. The current study evaluates the effect of LASIK eye surgery on corneal asphericity by comparing 2 software treatment platforms; the Q value customized ablation versus the conventional Wave-front optimized ablation in a fellow eye study pattern.
Detailed description
The standard excimer laser correction of myopia is associated with decreased visual quality in the form of a decrease in contrast sensitivity and night vision. This degradation of the visual quality is attributed to changes in the corneal asphericity that increase the high order aberrations (HOAs), such as spherical aberrations because it leads to shifting of the corneal asphericity towards the oblate shape. The wavefront-optimized (WFO) profile avoids the creation of new HOAs, but it is not able to treat those which are already present pre-operatively. The Q-adjusted treatments correct the sphero-cylindrical refractive errors and try to maintain the corneal asphericity at the same time, but like the WFO ablation profiles, it is limited to correcting the spherical aberrations and not the non-rotational symmetric HOAs. Some studies compared Lasers of two different platforms on contralateral eyes of the same patient in order to minimize inter-patient differences such as corneal wound healing and corneal biomechanics. By exclusion of these inter-patient differences, a more accurate judgment on the outcomes can be achieved.
Interventions
PROCEDUREFemtosecond laser assisted LASIK eye surgery
FS-LASIK eye surgery includes corneal flap creation with femtosecond laser using the Femtosecond laser WaveLight FS200 followed by excimer laser vision correction of the patient's refractive error using excimer laser WaveLight EX500.
Sponsors
Assiut University
Study design
Allocation
NON_RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
SINGLE (Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
Candidates for Laser vision correction (LVC) with 1. Myopic Spherical Equivalent up to -12 diopters. 2. Myopic astigmatism up to -6 diopters. 3. Corneal thinnest location ≥ 500 um 4- Residual stromal bed ≥ 300 um.
Exclusion criteria
1. Patients not candidates for LVC. 2. Hyperopic patients or mixed astigmatism. 3. Systemic disease that contraindicates LVC. 4. Intra- or post-operative complications. 5- Previous corneal surgery
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Postoperative Q value | 6 months | Pentacam evaluation of post-LASIK Q value |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Postoperative corneal thickness at the pupillary center | 6 months | Pentacam evaluation of post-LASIK pachymetry at the pupil center |
Countries
Egypt
Outcome results
None listed