Comparison of Next Generation Laser Techniques of Myopia Correction: iDesign vs. SMILE

Comparison of Next Generation Laser Techniques of Myopia Correction: iDesign vs. SMILE

The proposed study seeks to compare visual acuity, tomographic outcomes, biomechanical changes and inflammatory profile of normal eyes (matched for age, refraction and corneal thickness) undergoing iDesign and SMILE procedure. The hypothesis is that iDesign may deliver equivalent or better clinical outcomes than SMILE, by removing less tissue and correcting for higher order aberrations.

iDesign is a promising new technique to treat myopia with astigmatism using ocular aberrations measured with a high resolution wavefront sensor.[1,2] Early studies with iDesign platform has established its safety and efficacy in correction of myopia with fewer patients reporting night vision problems.[1,2] In keratoconus, iDesign has also provided excellent outcomes following collagen crosslinking.3 SMILE is a recent technique that eliminates creation of flap and appears to achieve similar refractive outcomes as conventional LASIK but with less dryness, less inflammation and faster wound healing.[4,5] SMILE corrects lower order aberrations only.[4,5] Thus, a comparative assessment of iDesign and SMILE is necessary since iDesign can potentially give better visual outcomes with lower volume of tissue removal. If lower volume of tissue is removed, it is also hypothesized that the corneal would be more stable biomechanically.[5] Further, SMILE does not provide any correction of higher order aberrations. With the inclusion of higher order aberrations in the iDesign treatment plan, it is hypothesized that both short and long term outcomes will be better with iDesign than with SMILE.

Inclusion Criteria:

1. Patients should be between 18 to 50 years of age.
2. Patient must have stable myopia for a minimum period of one year (a change of 0.25D or less) as documented by prior clinical records or current spectacle correction.
3. Patient must have a corrected distance visual acuity (CDVA) of 20/25 or better,
4. Patient must have a spherical equivalent refraction less than -10D
5. Patient must have refractive astigmatism less than 3D.

Exclusion Criteria:

1. Patient must not have a central corneal thickness (CCT) less than 480 micrometer
2. Patient must not have a calculated residual stromal bed thickness of less than 250 micrometer after the surgery
3. Patient must not have symptoms or signs of keratoconus, diabetes, collagen vascular disease, pregnancy, breastfeeding and any prior ocular surgery.
4. Patient must not have an inter-ocular difference of more than 1.00 diopter (D) of spherical or 0.50 D of cylindrical refractive error.
5. Patient must not be on chronic systemic steroids or other medication that can affect wound healing.
6. Patient must not be allergic to primary or alternative medications.
7. Patient must not be using rigid contact lenses for the last three weeks or soft contact lenses for at least 1 week before the preoperative evaluation.