Microkeratome chronicles: Management of a free flap

BACKGROUND: In LASIK (laser in situ keratomileusis), a hinged corneal flap is made, which enables the flap to be lifted and the excimer laser to be applied to the stromal bed. If the hinge of the corneal flap detaches from the cornea, the flap is called a free cap. A free cap is a rare intra-operative complication of LASIK most commonly associated with the use of a microkeratome on corneas with flat keratometry, which predisposes to a small flap diameter. Free caps are preventable and treatable. Rarely does the complication lead to a severe or permanent decrease in visual acuity. PURPOSE: As free caps are avoidable, prevention is critical. Our video gives some tips and tricks on how to avoid a free flap and also focuses on how to manage a cut through a free flap. SYNOPSIS: If a free cap is created, the surgeon must decide whether to continue with excimer laser ablation or to abort the procedure. When to abort: If the stromal bed is irregular, the flap is replaced without applying laser ablation. Without ablation, generally, there is no change in refractive error or significant loss of visual acuity. When to continue: If the stromal bed is regular and the cap is of normal thickness, the surgeon may proceed with ablation. To prevent desiccation, the free cap should be handled with caution and should be placed on a drop of balanced salt solution. The free cap should be placed epithelial facing up, along with a bandage contact lens. The endothelial cell pump mechanism typically allows the cap to re-adhere tightly. HIGHLIGHTS: Risk factors for a free cap are generally anatomic or mechanical. Especially in flat corneas, an appropriate ring and stop size should be chosen looking at the nomogram on the basis of the keratometry values. Deep orbits and deep-seated eyes should be looked for as PRK is a better option in such cases. Inadequate suction should be dealt with a lot of care, and once this is done, the vacuum should be stopped. Re-docking of the microkeratome with suction can be done again. Prior testing of the microkeratome and a good verbal anesthesia are a few more such important points to be pondered upon. This video gives us such tips and is a comprehensive video for a novice surgeon performing microkeratome LASIK. VIDEO LINK: https://youtu.be/piU9nK6rbm4