Application of the SMILE-derived lenticule in therapeutic keratoplasty

Correction of High Astigmatism by Autologous Astigmatic Lenticule Reshaping and Rotation

PURPOSE

To explore the use of autologous astigmatic lenticule reshaping and rotation surgery to correct high astigmatism in conjunction with excimer laser technology to correct residual refractive error.

METHODS

Six patients with high astigmatism (8 eyes, all with astigmatism from -5.50 to -11.00 diopters [D]) seeking refractive error correction were enrolled. The following methods were used to correct refractive errors that could not be corrected by a single conventional surgery: (1) cutting of a customized lens using FLEx technology, (2) lifting of the corneal flap and reshaping the autologous astigmatic lenticule in situ using an excimer laser, and (3) rotation of the autologous astigmatic lenticule by 90°. Uncorrected distance visual acuity, subjective refraction, corneal topography, and anterior segment optical coherence tomography were performed preoperatively and postoperatively.

RESULTS

The efficacy and safety indices at 6 months postoperatively were 0.93 ± 0.18 and 1.06 ± 0.11, respectively, the spherical equivalent remained stable and close to emmetropia (-0.13 ± 0.70 D) from 1 to 6 months postoperatively, postoperative astigmatism was generally mildly undercorrected (-1.22 ± 0.43 D), and the difference in corneal curvatures at 2 mm from the apex of the cornea was significantly reduced compared to preoperatively (P < .05); however, the corresponding values at 1 and 3 mm showed no difference.

CONCLUSIONS

Correction of high astigmatism with autologous astigmatic lenticule reshaping and rotation surgery is tissue-sparing, predictable, and significantly improves postoperative visual acuity and quality. This method is feasible and safe, with predictability requiring further study. This novel surgical approach has potential for patients with high astigmatism that cannot be corrected by conventional refractive surgery. [J Refract Surg. 2024;40(8):e554-e561.].

Restoring the Ocular Integrity of Perforated Corneal Ulcer Using Living Surgical Donor Tissues Derived From Keratoplasty in the COVID-19 Pandemic

The coronavirus disease 2019 (COVID-19) caused an unprecedented crisis for corneal surgeons who were forced to strategize for an acute shortage of tissues. Here, we report the initial clinical outcomes of utilizing host corneal buttons derived from optical penetrating keratoplasties of pseudophakic bullous keratoplasty (PBK) patients. Two patients presented to our department with a perforated fungal corneal ulcer in one eye during the COVID-19 pandemic. One eye of each of the patients was operated on with non-vascularized host cut tissues preserved in glycerin. The tissues were secured using 10-0 nylon sutures. Good anatomical integrity was achieved in both eyes. An optical penetrating keratoplasty (PK) was done in both eyes after one year for visual rehabilitation, with a final visual acuity of 20/120 and 20/80, respectively, at six months. In conclusion, therapeutic PK using host tissues obtained from the recipients of optical PK is a safe and effective option to restore ocular integrity during a shortage of fresh or glycerol-preserved corneas. However, optical PK is required for the final visual rehabilitation.

Lamellar surgeries with SMILE-derived lenticules

PURPOSE

Lamellar surgeries with SMILE lenticules are an evolving field of refractive surgery. This chapter intends to discuss the reported clinical results of using SMILE derived lenticules in terms of feasibility, safety and predictability; or the potential management of hyperopia, keratoconus, SMILE ectasia and presbyopia.

MATERIALS AND METHODS

Donor SMILE lenticules were prepared under microscope tocreate doughnut shaped lenticules. For hyperopia, this tissue was then inserted into afemtosecond laser enabled pocket created using VisuMax FS Laser at a depth of 160µm. For ectasia induced by keratoconus and post refractive procedure (SMILE), 0.23% riboflavin dye was instilled into the interface and then lenticule was inserted followed by exposure to UV-A radiation with total energy of 6.3 J.

RESULTS

Spherical equivalent (S.E.) of within ± 0.5 D was observed in 50% (n=21) eyes and within 1 D was seen in 71% eyes treated for hyperopia. A significant increase in the K mean anterior, central corneal thickness, Q-value and corneal aberrations was seen 2 weeks post-op. Clinical improvement in terms of S.E. and uncorrected distance visual acuity in eyes treated for ectasia after keratoconus and post refractive procedure (SMILE) was seen.

CONCLUSION

With the ample availability of SMILE- derived lenticules, researchers are exploring the possibility of using this tissue for the treatment of various refractive and corneal conditions.

Recurrence of perforation and overall patient survival after penetrating keratoplasty versus amniotic membrane transplantation in corneal perforation

PURPOSE

The following is a comparative analysis on the treatment outcomes of corneal perforations using amniotic membrane transplantation (AMT) or penetrating keratoplasty (PK).

METHODS

This monocentric retrospective study was performed at the Department of Ophthalmology, University Hospital Ulm, Germany. A total of 78 eyes of 78 patients were included. Thirty-nine eyes received an AMT, and 39 patients were treated with a PK. Primary outcome was recurrence of perforation. Secondary outcomes were patient mortality and visual acuity.

RESULTS

No statistically significant difference was observed with regard to a recurrence of perforation between the two groups (26% in AMT vs 23% in PK, p > 0.99). The time of recurrences was within the first two years and did not differ statistically (p = 0.97). In addition, a proportional hazards model with cox regression regarding recurrent perforation showed no significant differences (p = 0.5). After AMT, 41% and after KP, 28% of the patients died during follow-up (p = 0.2), respectively. The Charlson Comorbidity Index (p < 0.0001) and the age at the time of surgery (p = 0.0002) were statistically significantly higher in those who were deceased. A mean follow-up of 485 ± 517 days was recorded.

CONCLUSION

Both surgical methods show good results and no statistically significant difference regarding recurrent perforation rate. About a third of the patients died during the follow-up period. The decision regarding the appropriate method should therefore be based on a combination of all factors.

[Complications of femto-LASIK and features of cavitation injuries]

Modern approach to refractive laser surgery features three main types of lamellar surgery. Two of them are types of open laser keratomileusis (LASIK and femtosecond laser-assisted LASIK), and the third - closed (SMILE). All of these techniques allow achieving good clinical outcomes but differ in possible complications. This article reviews the complications of femto-LASIK and specifically the post-operative cavitation injuries, describes the mechanism of their occurrence, variants of their course, and presents the prevention measures.

Effect of corneal stromal lenticule customization on neurite distribution and excitatory property

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Refractive SMILE-derived stromal lenticules are useful in various tissue-engineering approach for therapeutics, of which they are required to be customized before implantation.

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Excimer laser-mediated reshaping, riboflavin-UVA-induced collagen crosslinking and chemical decellularization significantly removed lenticule neurites, but the residual neurites retained excitatory response.

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Reinnervation occurred in the decellularized lenticules, indicating a potential of nerve regeneration.

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Stromal lenticules, as a unique collagen-rich biomaterial with high transparency, refractivity and mechanically robust, together with the ability of neurite regeneration, could hold a potential for various ophthalmic applications.

Introduction

Refractive stromal lenticules from Small Incision Lenticule Extraction (SMILE), though usually discarded, hold a potential for various ophthalmic applications, including refractive correction, stromal volume expansion, and biomechanical strengthening of the cornea.

Objectives

To investigate the effect of lenticule customization on lenticule neurite length profile and the excitatory response (calcium signaling) and the potential of reinnervation.

Methods

Human and porcine stromal lenticules were treated by (1) excimer laser reshaping, (2) ultraviolet A-riboflavin crosslinking (CXL), and (3) decellularization by sodium dodecyl sulfate (SDS), respectively. The overall neurite scaffold immuno-positive to TuJ1 (neuron-specific class III β-tubulin) expression and population of active neurite fragments with calcium response revealed by L-glutamate-induced Fluo-4-acetoxymethyl ester reaction were captured by wide-field laser-scanning confocal microscopy, followed by z-stack image construction. The NeuronJ plugin was used to measure neurite lengths for TuJ1 (NL-TuJ1) and calcium signal (NL-Ca). Reinnervation of lenticules was examined by the ex vivo grafting of chick dorsal root ganglia (DRG) to the decellularized human lenticules. Differences between groups and controls were analyzed with ANOVA and Mann-Whitney U test.

Results

The customization methods significantly eliminated neurites inside the lenticules. NL-TuJ1 was significantly reduced by 84% after excimer laser reshaping, 54% after CXL, and 96% after decellularization. The neurite remnants from reshaping and CXL exhibited calcium signaling, indicative of residual excitatory response. Re-innervation occurred in the decellularized lenticules upon stimulation of the grafted chick embryo DRG with nerve growth factor (NGF 2.5S).

Conclusion

All of the lenticule customization procedures reduced lenticule neurites, but the residual neurites still showed excitatory potential. Even though these neurite remnants seemed minimal, they could be advantageous to reinnervation with axon growth and guidance after lenticule reimplantation for refractive and volume restoration of the cornea.