A new sign in the armamentarium helps to confirm correct dissection of the anterior and posterior planes in SMILE surgery.

Small incision lenticule extraction represents a significant advancement in refractive surgery, combining minimal invasiveness with consistently favorable visual outcomes.

Although SMILE offers several advantages, accurate identification of tissue planes remains a technical hurdle, especially for novice surgeons. Intraoperative misinterpretation of either the anterior (cap) or posterior lenticule interface can result in incorrect plane dissection, contributing to complications such as false passage creation, lenticule remnants and cap tears. These intraoperative challenges can hinder surgical fluency and potentially compromise visual outcomes. Precise recognition of the correct dissection plane is therefore essential to enhance the safety and success of the procedure. In a study published in Clinical Ophthalmology, we proposed a novel intraoperative sign aimed at improving plane identification during lenticule dissection.

We present the "Ridge sign" as a reliable and easily appreciable intraoperative indicator that confirms the accurate identification of both anterior and posterior lenticular dissection planes before completing the anterior dissection.

After femtosecond laser application, the cap side incision is gently opened using the hooked end of a dissector (Figure 1). The same instrument is then used to define the anterior dissection plane -- positioned above the lenticule -- by creating a small anterior pocket on one side of the side cut (Figure 2). Thereafter, the posterior dissection plane delineation on the contralateral side beneath the lenticule helps establish the corresponding posterior pocket (Figure 3).

At this stage, the Ridge sign helps to confirm the creation of the anterior and posterior pockets. The sign is observed as an oblique ridge-like structure, bridging the cap on one side and the stromal bed on the other, at the interface between the dissected and undissected segments of both planes (Figure 4).

The Ridge sign can be reconfirmed by introducing and carefully positioning the arm of the blunt dissector into the anterior dissection plane at the interface between dissected and undissected regions of both lenticular planes. Gentle anterior displacement of the instrument at this junction accentuates the Ridge sign, characterized by a sloping, ridge-like structure extending between the cap and stromal bed, thereby facilitating clear intraoperative visualization (Figure 5).

The Ridge sign is a confirmatory sign of accurate entry into the anterior plane. Thereafter, the surgeon proceeds to complete anterior plane separation. Simultaneously, the posterior lenticular plane is accessed via the posterior pocket. Once both planes have been dissected, the lenticule is extracted using micro-forceps.

Inaccurate dissection into the anterior or posterior lenticular plane is characterized by the absence of the Ridge sign, which otherwise serves as a reliable intraoperative landmark. Its absence denotes improper entry, evidenced by persistent attachment of the lenticule to the cap in cases of posterior plane misdissection (Figure 6) or to the stromal bed in anterior plane misdissection. This misdissection is typically detected during the initial formation of dissection pockets using a sharp hooked dissector. By acknowledging the missing Ridge sign at this stage, surgeons can avoid committing to the wrong dissection plane with the blunt dissector, thereby minimizing the risk for subsequent complications.

This technique offers the surgeon a secondary opportunity to access the correct dissection plane by approaching the untouched, contralateral side of the side cut. Once the Ridge sign is reestablished at the newly formed junction between dissected and undissected regions of both planes on the opposite side, anterior dissection is initiated. Concurrently, the posterior plane is accessed through the posterior pocket. With both planes appropriately delineated, the lenticule is successfully separated and extracted without complication.

In conclusion, the Ridge sign offers a reliable intraoperative guide to assess the accuracy of anterior and posterior plane dissection before final lenticule and cap separation, thereby ensuring precise dissection and enhancing the safety of lenticule extraction.