Corneal Ectasia Risk And Percentage Tissue Altered In Myopic Patients Presenting For Refractive Surgery

Area of Science:

• Ophthalmology
• Corneal Surgery
• Refractive Surgery

Background:

• A Percentage Tissue Altered (PTA) score of ≥40% is a known risk factor for post-operative ectasia after Laser-Assisted In-Situ Keratomileusis (LASIK).
• The safety thresholds for newer refractive procedures like Small Incision Lenticule Extraction (SMILE) and Laser-Assisted Sub-Epithelial Keratectomy (LASEK) regarding PTA are not well-defined.

Purpose of the Study:

• To investigate whether refractive procedures such as LASEK and SMILE alter the acceptable Percentage Tissue Altered (PTA) range for safe corneal refractive surgery.
• To evaluate the potential risk of corneal ectasia in patients undergoing LASEK or SMILE based on estimated PTA scores.

Main Methods:

• A retrospective observational study reviewed 114 eyes (66 patients) that underwent LASEK or SMILE.
• Percentage Tissue Altered (PTA) was calculated for each patient as if they had undergone LASIK.
• The Randleman Ectasia Risk Score System (ERSS) was used to assess pre-operative ectasia risk.

Main Results:

• A significant proportion of eyes undergoing SMILE (up to 31.9%) and LASEK (up to 60.0%) had calculated PTA scores ≥40%.
• Maximum calculated PTA reached up to 47.9% in the SMILE group and 51.5% in the LASEK group.
• While 12.8-80.0% of eyes were at moderate-to-high risk based on ERSS, no post-surgical ectasia was observed within 3 years.

Conclusions:

• SMILE and LASEK procedures appear to modify the PTA range within which refractive surgery can be safely performed.
• New, procedure-specific PTA thresholds must be established for LASEK and SMILE to ensure patient safety and prevent post-operative ectasia.
• Clinical practice recommendations require further determination of safe PTA limits for these alternative refractive surgeries.