Current Technique and Instrumentation for SMILE



Fig. 5.1
Femtosecond laser ReLEx(R) cuts, (a) frontal, and (b) cross-section views



This is the most critical part of the procedure refractively because it is where the femtosecond laser defines the anterior and posterior plane between which the lenticule will be created. The dimension and shape of the lenticule determine the amount of spherical and cylindrical correction and the effective optical zone of treatment. The smoothness of the cuts affects the smoothness of the corneal surface once the lenticule has been extracted. The smoothness of the surface is further affected by the postoperative epithelial remodeling (see Chap. 13), but the initial smoothness immediately after the procedure has significant effects on the early visual quality and recovery.

In bilateral cases, while the first eye is receiving the laser treatment, the second eye should be held shut with an adhesive strip, to prevent uneven dehydration of the epithelium that may lead to temporary roughness of the surface, in turn affecting the smoothness of the laser cuts and the visual recovery time (Fig. 5.2).

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Fig. 5.2
The second eye is taped shut before the laser application to the first eye



5.2 Lenticule Extraction


Immediately after the femtosecond laser cuts are completed, the lenticule is still not freely extractable, as there are still micro-bridges between the interfaces. The surgeon breaks those micro-bridges by bluntly dissecting in the plane between the lenticule and the stromal cap and that between the lenticule and the stromal bed, to free the lenticule from its surroundings. The lenticule is then retrieved and removed from the pocket.


Instrumentation

The Lenticule Extraction part of ReLEx® SMILE requires minimal instrumentation. This includes:



  • Basic instruments: Eyelid speculum, absorbent surgical spears, sterile balanced salt solution (15 cc bottle), blunt irrigating cannula, and Kelman-McPherson-type forceps.


  • An eyelid speculum: A solid-bladed, self-retaining speculum. I prefer the pediatric size, as the shorter blades create more vertical space resulting in a roughly hexagonal, rather than rectangular, exposure. This is especially useful in the eyes with shorter palpebral fissures (Fig. 5.6). In the eyes with better exposed globes, a standard LASIK aspirating speculum in the aspirating mode (connected to the pump) during the laser cut will help to prevent tear pooling and reduce the incidence of suction loss. Wire speculum should be avoided.


  • Specific instruments: Lenticule dissector for freeing the lenticule and microforceps for retrieving the freed lenticule.


The Chansue ReLEx® Dissector

When I started performing ReLEx® in 2010, the standard instrument recommended by the laser manufacturer for dissecting the lenticule was the Seibel flap lifter (Fig. 5.3) or a simple phako spatula and the Blum modified McPherson forceps. As the name implies, Seibel flap lifter was designed to be used for flap lifting in FemtoLASIK. It worked quite well as a dissector for ReLEx® FLEX, as the flap and the lenticule were lifted in the same manner as the flap in FemtoLASIK. However, the instrument lends itself poorly to lenticule dissection when a small incision is intended, as it is too straight and too long. Consequently, I designed a new instrument specifically for ReLEx® lenticule dissection later that year. It has a curved tapering circular shaft which ends in a conical semi-blunt dissecting tip. The other end of the dissector bears a Sinskey-style hook in the same fashion as does the Seibel Flap Lifter but is slightly longer to facilitate the delineation of both planes. The instrument is called the Chansue ReLEx® Dissector (CRD). The CRD was designed to conform with average corneal curvature, to minimize distortion and stress to the anterior stromal cap (Fig. 5.4a).

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Fig. 5.3
The Seibel LASIK flap lifter


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Fig. 5.4
(a) The Chansue ReLEx(R) Dissector (CRD). (b) Kostin spatulas (Medin-Ural/Russia) are slightly slender compared to the original Chansue dissector and is produced in two different lengths. (c) The original Blum spoon (Geuder GmbH/Germany) designed at the early stage of ReLEx®development features a semi-sharp ending similar to a hockey knife. (d) Due to a better laser cut quality of the 500 kHZ VisuMax®, Bloom spoon was replaced by several similar instruments featuring a blunt, rounded, and polished head as shown in this advanced Chansue dissector

Meanwhile some further modification of different instruments were made by other surgeons in cooperation with other ophthalmic instruments manufacturers, but they are generally speaking either:

1.

Spatulas resembling the CRD, but with different lengths and diameter (e.g., Kostin spatula/Medin-Ural/Russia, Fig. 5.4b) or

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May 26, 2017 | Posted by in OPHTHALMOLOGY | Comments Off on Current Technique and Instrumentation for SMILE
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