Chemical, Physical, and Biological Corneal Decellularization Methods: A Review of Literature

The cornea is one of the most commonly transplanted tissues worldwide. It is used to restore vision when severe visual impairment or blindness occurs in patients with corneal diseases or after trauma. Due to the global shortage of healthy donor corneas, decellularized corneal tissue has significant potential as an alternative to corneal transplantation. It preserves the native and biological ultrastructure of the cornea and, therefore, represents the most promising scaffold. This article discusses different methods of corneal decellularization based on the current literature. We searched PubMed.gov for articles from January 2009 to December 2023 using the following keywords: corneal decellularization, decellularization methods, and corneal transplantation. Although several methods of decellularization of corneal tissue have been reported, a universal standardised protocol of corneal decellularization has not yet been introduced. In general, a combination of decellularization methods has been used for efficient decellularization while preserving the optimal properties of the corneal tissue.

Scleral Grafts in Ophthalmic Surgery. A Review

AIM

To summarize the history and current trends in the use of scleral grafts in ophthalmology.

MATERIALS AND METHODS

We conducted a review of the literature through the MEDLINE and Cochrane Library databases. The search terms were "sclera", "graft", and "surgery". The search resulted in 1596 articles, of which we evaluated 192 as relevant. The relevant articles were sorted chronologically and according to the method of using scleral grafts, which enabled the development of a review article.

RESULTS

The sclera has been routinely used in ophthalmology since the 1950s in many different indications. Some of these indications have become practically obsolete over time (for example, use in the surgical management of retinal detachment), but a large number still find application today (especially use in glaucoma or oculoplastic surgery, or as a patch for a defect in the sclera or cornea).

CONCLUSION

Even though allogeneic sclera is currently used less frequently in ophthalmology compared to other tissue banking products and the range of its indications has partially narrowed, it remains a useful material due to its availability and properties.

P37-A124 Smile bank - corneal stromal lenticules from relex smile - the new eye bank product

PURPOSE

The aim of our presentation is to introduce future eye bank product - corneal stromal lenticule from living donors, which can be used for allotransplantation.

METHODS

ReLEx (refractive lenticule extraction) SMILE (small incision lenticule extraction) is a common approach in laser eye surgery. It is minimally invasive and flap-free procedure. During this procedure part of corneal stroma (lenticule) is created by femtosecond laser and consequently removed through small incision. The lenticule is basically waste material of the ReLEx SMILE procedure. In the International Eye Bank of Prague, we decided to establish new protocol for lenticule withdrawal, storage and release for transplantation.

RESULTS

All donors signed an informed consent, and their serum was tested for the presence of infectious diseases. After ReLEx SMILE procedure the lenticule was stored in container with cryopreservation solution and frozen in the eye bank using the same protocol for frozen amniotic membrane. After 6 months in -80°C tissues were defrosted and examined histologically, using conventional light histology staining and electron microscopy.

CONCLUSION

We believe, that lenticule from living donor is a safe and effective tissue, that can be used for many indications and in particular situations represents good alternative to whole donor cornea and amniotic membrane.

Refractive Outcome After Corneal Lenticule Implantation Ex Vivo Non-Human Study

PURPOSE

To evaluate changes in corneal refractive parameters after implantation of a stromal lenticule of different thickness. We assume that the refractive outcome depends on the optical power of the used lenticule.

METHODS

We conducted an ex-vivo non-human study on 33 normotonic porcine eyeballs divided into two groups, for 4D and 8D human lenticule implantation. Corneal stromal lenticules were obtained as a by-product from a laser procedure ReLEx SMILE. We evaluated corneal refractive parameters measured on Oculus Pentacam© device before and immediately after the intrastromal lenticule implantation.

RESULTS

There was no statistically significant difference in corneal refractive parameters between the eyeball groups before lenticule implantation. In both groups, the intrastromal implantation in the depth of 300um led to a significant increase of central corneal pachymetry and corneal anterior steepening. In the 4D group the average central corneal pachymetry increased from 903 ± 124.59 to 1230 ± 148.99 (p = 0.0022) and in 8D group from 733.35 ± 69.60 to 1109 ± 161.64 (p = 0.0008). Induced changes in other studied parameters were not statistically significant, Kmax changed from 45.57 ± 2.78 to 72.07 ± 16.83 (p = 0.0094) and Km front from 40.72 ± 1.60 to 48.87 ± 5.83 (p = 0.0037) in 4D group and in the 8D group average Kmax increased from 42.22 ± 1.54 to 62.95 ± 12.67 (p = 0.0001) and K2 front 40.46 ± 1.64 to 51.51 ± 9.63 (p = 0.0037). There were no significant differences in refractive changes between the 4D and 8D groups after lenticule implantation.

CONCLUSION

Intrastromal corneal lenticule implantation induces changes in corneal refractive parameters. In both groups, the implantation induced a significant increase of an anterior corneal steepening without any significant influence on posterior corneal flattening. Corneal lenticule implantation did not lead to any significant change of corneal astigmatism. However, in order to have more precise data for future clinical applications we need to continue with the experiments and verify the results on human corneas.

[Clinical trial of Pilogel HS made by Alcon]

The authors give an account on the results of clinical tests of the anti-glaucomatous preparation PILOGEL HS of ALCON Co. The drug replaced in all groups of patients reliably 1-3% Pilocarpine administered three times a day, as regards its effect on intraocular tension. Its great practical advantage is that the effect is achieved after a single administration per 24 hours (at night). In particular patients in their productive age appreciate this advantage. The preparation was included in the import plan.