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Dr. Sheetal Brar, Dr. Sri Ganesh

ABSTRACT

Purpose:

To describe the therapeutic  use of Circle software for the management ofretained lenticule tissue  after complicated Small Incision Lenticule Extraction (SMILE) procedure.

Methods:

Two patients were referred for consultation and management due to intraoperative complications during SMILE. In case 1, there was a black patch during laser delivery due to which the lenticule was torn irregularly from the undersurface during extraction and a sliver of it was retained in the pocket.  Case 2 presented with false plane dissection with a completely retained lenticule on ASOCT. Both cases were managed using the Circle software by converting the cap into a flap, thus making access to the interface possible.

Results:

In case 1, after lifting the flap, a small sliver of tissue was found in the interface, which was dissected , followed by which a 20 µ Phototherapeutic keratectomy(PTK) was done to smoothen out the interface. In case 2, after lifting the flap, the edge of the retained lenticule was identified by using an endoilluminatorand the lenticule was separated and subsequently removed.Both cases  showed significant improvement in uncorrected distance visual acuity(UDVA) ,corrected distance visual acuity(CDVA)and objective scatter index(OSI)on day 1 post repair surgery.

Conclusion:

Circle software may be successfully used for managing retained lenticule tissue apart from performing enhancement after SMILE.

Keywords:Circle software, retained lenticule, SMILE

Introduction

Despite the potential advantages of SMILE over femtosecond laser assisted in situ keratomileusis (FS-LASIK) and photorefractive keratectomy (PRK), the procedure is characterized by a steeper learning curve, during which intraoperative complications may occur.1.2,3,4,5 Black spots leading to difficult dissection, inadvertent dissection of posterior plane, improper technique of dissection, false plane creation, andexcessive tissue handling may causeretention of the whole lenticule or part of it, resulting in irregular astigmatism and an unacceptable outcome.2

In the present case series, we report  two complicated SMILE cases who presented to us with  irregular astigmatism due to retained lenticule tissues, and describe their management using Circle software present in the VisuMaxfemtosecond laser used to perform SMILE,in order to restore visual acuity. It must be emphasized here that the described use is a “therapeutic” indication of this software, the recommended clinical  indication being enhancement following SMILE.2,6

CASE 1

A 33 year old female presented with history of undergoing SMILE procedure in both eyes, 4 months ago for myopic astigmatism of -1.00 D Sph/-3.75 Dcyl @15 in the right eye and -2.50 D Sph/-4.25 Dcyl @170 in the left eye.The surgery was uneventful in the right eye, however the left eye surgical course was complicated leading to a suboptimal outcome.

On presentation, her uncorrected distance visual acuity(UDVA ) in RE was 20/20,  whereas in the  LE  it was 20/60 , which was correctable with  -1.00 D Sph/ -1.00 Dcyl @ 125  to  20/40p. Upon reviewing the surgical video(supplementary file 1), it was found that there was an occurrence of a large black patch during the lenticule cut creation, which approximately extended from the centre  of the cornea towards the access incision superiorly. Consequently, the surgeon had difficulty in separating the lenticule tissue corresponding to this area. However, he was successful in extracting the lenticule by performing manual dissection, and the lenticule appeared to be intact on inspection.

Since the lenticule was extracted completely, possibility of having a retained lenticule tissue was deemed to be remote. However, post-op topography (Oculus,Pentacam HR) showed  irregular astigmatism and central steepening( K1 44.2D,K2 46.3,Sim K 45.2 D)(Fig 1 A1), which was also noticeable in dilated clinical photograph taken in retroillumination (Fig 2A). The anterior segment optical coherence tomography (ASOCT)(Optovue, Fremont), showed an area of hyper-reflectivity and irregularity, however, it did not reveal any retained tissue(Fig 3,A1). Visual quality as assessed with the HD Analyzer(OQAS,Visiometrics, Spain) showed poor quality of vision with a  Objective Scatter Index( OSI) score of 9.2 suggesting high optical scatter in the interface( Fig4, A1). These findings led us to the conclusion that there was interface irregularity and scarring due to excessive tissue manipulation, which was causing the irregular astigmatism and a drop in CDVA.

Management: Circle Software was programmed to create a 7.9 mm flapusing the C or  junction up  pattern, at 120 microns which was the same depth  at which the cap of the primary SMILE procedure was made(Fig 5A). A nasal hinge was used. The plan was to gain access to the interface and correct the interface irregularity by performing a PTK treatment of 50 microns on the stromal bed. However, to our surprise, after the flap was separated, an oval sliver of tissue, approximately 2.5×3.5 mm, extending from the centre to the edge of the superior incision was found adherent to the underlying stromal bed (supplementary file 2).

The treatment plan was modified on table and we decided to attempt the separation of this remnant tissue. The  tissue was gently separated using a Seibel’s spatula, followed by which a minimal PTK of 20 micron was performed using MEL 90 excimer laser (Carl Zeiss Meditec,Jena,Germany) to  smoothen out the interface due to old scarring. The interface was washed with balanced salt solution( BSS) following which the flap was reposited.

While repositing the flap, a ridge of raised epithelium was noted in the center for which epithelial debridement was performed, followed by placement of a bandage contact lens on the eye. One week post-operatively, the UDVA improved to 20/20p in the LE and CDVA improved to 20/16 with +0.25 D Sph /-0.5 Dcyl@40º. Topography showed regularization of the corneal contour ( K1 40.3D,K2 41.5D,Sim K 40.9D)( Fig1 A2).Both the ASOCT and dilated clinical photography showed a more regular and clear interface ( Fig2 A2 & Fig 3 A2).The Objective Scatter Index(OSI) also improved from 9.2  to2.5, suggesting a significant  improvement in the quality of vision in the left eye (Fig4 A2).

CASE 2

A 31 years old female patient presented with history of undergoing SMILE procedure for a myopic refractive error of  -5.00D Sph   in the right eye and  -5.25 DSph in the left eye, 2 days ago. Her right eye procedure was uneventful, however the left eye had intraoperative difficulty due to which the surgeon was unable to extract the lenticule and had to abandon the procedure.On presentation,  her UDVA in the RE was 20/16 , and in the LE was 20/60 , which was correctable to 20/20 p with a subjective refraction of -4.00 / -2.00 @10º.

The surgery video was reviewed andit was found that the femtosecond laser  pattern delivered to the cornea was normal and did not show any black spots , opaque bubble layer or suction loss during the laser delivery stage(supplementary file 3).The surgeon first identified both the superficial and deep lenticule planes and then dissected the superficial plane.However, while dissecting the deeper plane, he created a false plane deeper to the posterior lenticuleand continued to perform a lamellar dissection in this plane until the edge of the side cut all around.

However, he was unable to extract the lenticule with the microforceps, since there was no side cut created at the depth of the false plane due to which he abandoned the case and referred the patient for further management. The topography of the eye showed  irregularity, increased pachymetry and diffuse elevation in the central and superior part of the cornea( K1 46.7D,K2 47.8D,Sim K 47.2 D)( Fig1 B1). The ASOCT (Fig 3 B1) showed the lenticule in situ, with presence of a lamellar plane at approximately 300 microns depth in the mid periphery, deeper to the posterior lenticule cut. Optical quality was poor with an OSI value of 9.(Fig 4 B1)

Management:The pupil was dilated prior to the surgical intervention. Similar to the first case,the Circle software was used to programme a 7.6 mm flapat 120 microns and a nasal hingeusing the C or junction uppattern( Fig 5B ).The flap was separated to expose the interface. A fibre optic illuminator was used for the identification of the edge of the lenticule after switching off the microscope light which was then gently dissected using a Siebel’s spatula and separated from the stromalbed(supplementary file 4).

The interface waswashed and the flap reposited. Post-operatively at 1 month, bothUDVA  and CDVA  improved to  20/20 and  20/16 respectively, with a subjective acceptance of  a minimum cylinder of -0.25  Dcyl @ 80º. The topography became regular(K1 40.6D,41.1D,Sim K 40.9 D)(Fig 1 B2), and the ASOCT showed clear interface, with the persistence of the false deeper plane(Fig 3 B2).Correspondingly, the OSI values also improved from 9 to 3 post repair surgery( Fig 4 B2)There was minimum stromal scarring as evident from clinical photographtaken with sclerotic scatter, however, it did not involve the visual axis (Fig2B ).

DISCUSSION

We recently published the management and outcomes of retained lenticules or their fragments in different scenarios following complicated SMILE surgery, in which we emphasized the importance of detailed clinical evaluation including ASOCT, to assist in the extraction of retained tissues and restoration of uncorrected and best corrected visual acuity.7 We reported the management of three such cases, which required exploration through the original SMILE surgery incision. However, the present paper discusses the use of Circle software in these complicated situations , which is an “off-label” indication of this software.

Briefly, the Circle software is a dedicated software in the VisuMaxfemtolaser system,which enables the conversion of   SMILE cap into a flap, in order to allow the surgeon to perform excimer laser assisted enhancement for any refractive inaccuracies.8 However, its use for therapeutic indications arising out of complicated SMILE  scenarios has not been explored much.Chensue et al, published their safety and efficacy data  on   SMILE enhancement with Circle software in 27 eyes and retained lenticule tissue extraction in one eye. However, the authors did not provide the pre and post repair surgery data of this particular case in their publication.9

As discussed in the previous publication, the ideal management of retained lenticules or fragments is surgical exploration of the pocket through the original SMILE incision.Before contemplating exploration, however, the size and location of the retained tissue should ideally be confirmed by ASOCT, topography and dilated clinical photography.7However in the present two case scenarios discussed, we preferred to use Circle software and conversion into flap, rather than entering into the original SMILE incision for surgical exploration. This is because both cases presented with unique complications. In the first case,

A retained lenticule tissue was not suspected, as the extraction of the lenticule was complete.Moreover, the ASOCT of the eye was not conclusive and did not reveal obvious presence of a retained tissue. Conversion to flap was contemplated with the aim of smoothening the irregular interface with PTK, which was thought to have occurred due to forceful and excessive stromal tissue manipulation. It was only once the flap was separated, that a thin sliver of tissue (which had split from the under surface of the lenticule while separating the deeper plane), adherent to the stromal bed was recognized and hence the treatment plan was modified on table. In the second case, the surgical video and ASOCT had revealed

The formation of a false plane due to lamellar dissection, deeper to the lenticule cut with complete retention of the lenticule. In this scenario also, it would have been challenging to remove the retained lenticule through the original SMILE incision, as there were multiple planes of entry seen on AS-OCT. Also, once a false plane is created, the chances of the dissector going repeatedly into the same (false) plane may be high due to distortion of the corneal lamellae making the identification of  the original plane, even more challenging.Hence, in such situations it may be better to perform “open exploration” by converting the cap into flap,

which would provide better access and visibility of the interface, compared to pocket exploration through the original interface, where access to the interface is limited. Finally, this method may also be employed to rescue retained lenticule tissue following complicated SMILE, if surgical exploration through original incision fails or as a primary treatment of choice if the surgeon does not feel confident about entering the old incision.

With regard to the method of flap creation, at present only Circle software can enable interface access without creating a femtolaser pass through the interface using 4 different patterns of junctional cut, lamellar ring and side cut .8,9 It is not recommended to use the “Flap module” and  cut a new flap at the same depth as the original cap thickness, as this would create another laser pass through the interface, which may cause further irregularity and  is not desirable. One option for accessing the interface may be by creation of a new side cut, programmed at the edge of the original lenticule plane,similar to the technique of mini flap creation for LASIK enhancement described byGarcia-Gonzalezet al.10,11 However, this provision is not available with the current model of the femtolaser used to perform SMILE.

In their experimental study on rabbit eyes, Riau et al, compared  four different Circle patterns for flap creation after small incision lenticule extraction (SMILE) . They concluded that the Circle  pattern ‘D’, ie,  a lamellar ring adjacent to the cap cut, was the most optimal to be used for flap creation in cases of SMILE re-treatment.8They found that the flaps produced by pattern ‘C’ i.e, lamellar ring anterior to the cap, were also easy to lift, with minor intrastromal resistance experienced during the lifting process,and the transition between the lamellar ring and cap cut being  hardly discernible in pattern C-treated corneas. In our experience also, pattern ‘C’, which was for both the described cases, was safeand easy to use for flap creation,  without any additional difficulty.

The second case also describes a unique way of identifying the edge of the retained lenticule which is adherent to the stromal bed, after flap lift.  The oblique illumination with an endo-illuminator may be superior to the co-axial light of the surgical microscope of VisuMax FS laser for better visualization of the lenticule edge. Once identified, the separation of adherant lenticule may be carried out easily, without causing further damage to the interface.

Hence, in conclusion, the above described therapeutic use of Circle software for managing retained lenticule tissues may be justified in certain situations arising out of complicated SMILE, such as when the cause of  interface irregularity is not evident on clinical examination and ASOCT, lenticule stuck on stromal bed due to false plane  dissection  or failed surgical exploration of the pocket through the original SMILE incision. To our knowledge,

This is the first detailed report describing the successful use of CIRCLE software for managing interface irregularity due to retained lenticule tissue, other than its indication for enhancement after SMILE. Of course, the obvious downside of this option is creation of a flap, which defeats the primary purpose of SMILE (flapless correction).12-16However, in our experience, it may be a safer option in the above described complicated scenarios in SMILE, due to the potential advantages of better visualization of the interface and less tissue manipulation, resulting in favourable visual outcomes.

References:

  1. Ivarsen A, Asp S, Hjortdal J. Safety and complications of more than 1500 small-incision lenticule extraction procedures. Ophthalmology. 2014.121:822-8.
  2. Shah R. Complications After SMILE and Its Management Including Re-treatment Techniques. In: Sekundo W. ed. Small Incision Lenticule Extraction (SMILE): Principles, Techniques, Complication Management, and Future Concepts. Springer International Publishing Switzerland 2015:97-105.
  3. Qiu P-J, Yang Y-B. Analysis and management of intraoperative complications during small-incision lenticule extraction. International Journal of Ophthalmology. 2016.9(11):1697-1700.
  4. Hamed AM, Abdelwahab SM, Soliman TT. Intraoperative complications of refractive small incision lenticule extraction in the early learning curve. Clinical Ophthalmology (Auckland, NZ). 2018.12:665-668..
  5. Wang, Yan et al.Incidence and management of intraoperative complications during small-incision lenticule extraction in 3004 cases.Journal of Cataract & Refractive Surgery .Volume 43 , Issue 6 , 796 – 802
  6. Riau AK, Liu Y-C, Lim CHL, Lwin NC, Teo EP, Yam GH, et al. Retreatment strategies following Small Incision Lenticule Extraction (SMILE): In vivo tissue responses. PLoS ONE.2017.12(7): e0180941.
  7. Sri Ganesh, MS, DNB; Sheetal Brar, MS; Apostolos Lazaridis, MD.Management and Outcomes of Retained Lenticules and Lenticule Fragments Removal After Failed Primary SMILE: A Case Series ,Journal of Refractive Surgery. 2017.33(12):848-853
  8. Riau, Andri&Ang, Marcus & C Lwin, Nyein&Chaurasia, Shyam& T Tan, Donald & Mehta, Jodhbir. (2013). Comparison of Four Different VisuMax Circle Patterns for Flap Creation After Small Incision Lenticule Extraction. Journal of refractive surgery (Thorofare, N.J. : 1995). 29. 236-44. 10.3928/1081597X-20130318-02.
  9. Chansue E, Tanehsakdi M, Swasdibutra S, McAlinden C. Safety and efficacy of VisuMax® circle patterns for flap creation and enhancement following small incision lenticule extraction. Eye and Vision. 2015;2:21.
  10. Garcia-Gonzalez, Montserrat & Teus, Miguel.Creation of a New Femtosecond Laser-Assisted Mini-Flap to Enhance Late Regression After LASIK. Journal of refractive surgery (Thorofare, N.J. : 1995).2013. 29. 1-6. 10.3928/1081597X-20130611-01.
  11. Perry Binder, MS, MD, moderator Chris Blanton, MD Sumit “Sam” Garg, MD Miguel Teus, MD, PhD George Waring IV, MD,Understanding technology advances in refractive femtosecond laser platforms,A CME activity provided by Evolve Medical Education LLC and distributed with Cataract & Refractive Surgery Today and Cataract & Refractive Surgery Today Europe.March 2018
  12. Lazaridis A, Droutsas K, Sekundo W. Topographic analysis of the centration of the treatment zone after SMILE for myopia and comparison to FS-LASIK: subjective versus objective alignment. J Refract Surg. 2014;30:680-6.
  13. Mohamed-Noriega K, Riau AK, Lwin NC, Chaurasia SS, Tan DT, Mehta JS. Early corneal nerve damage and recovery following small incision lenticule extraction (SMILE) and laser in situ keratomileusis (LASIK). Invest Ophthalmol Vis Sci. 2014;55:1823-34.
  14. Wang D, Liu M, Chen Y, et al. Differences in the corneal biomechanical changes after SMILE and LASIK. J Refract Surg. 2014;30:702-7.
  15. Dong Z, Zhou X, Wu J, et al. Small incision lenticule extraction (SMILE) and femtosecond laser LASIK: comparison of corneal wound healing and inflammation. Br J Ophthalmol. 2014;98:263-9.
  16. Farjo AA, Sugar A, Schallhorn SC, et al. Femtosecond lasers for LASIK flap creation: a report by the American Academy of Ophthalmology. Ophthalmology. 2013;120:e5-e20.

Legends:

Fig 1. Pentacam axial curvature map of case 1 ( A1- Pre & A 2- post repair surgery) and case 2( B1- Pre & B2- post repair surgery)

Fig 2. Fig 2. Clinical photographs of Case 1( A1) pre repair surgery (A2) Post repair surgery , (B)-Case 2 post repair surgery

Fig 3. AS-OCT of case 1 ( A1- Pre & A 2- post repair surgery) and case 2( B1- Pre & B2- post repair surgery)

Fig 4 . HD Analyzer of case 1 ( A1- Pre & A 2- post repair surgery) and case 2( B1- Pre & B2- post repair surgery)

Fig 5 . Repair treatment planning with Circle software for case 1 ( A), and case 2( B)

Supplementary file 1: Surgical video of the primary surgery of case 1

Supplementary file 2: Surgical video of the repair surgery of case 1

Supplementary file 3: Surgical video of the primary surgery of case 2

Supplementary file 4: Surgical video of the repair surgery of case 2

 

 

 

 

 

 

 

 

 

 

 

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