Effects of collagen crosslinking on porcine and human tarsal plate

Biopolymeric Innovations in Ophthalmic Surgery: Enhancing Devices and Drug Delivery Systems

The interface between material science and ophthalmic medicine is witnessing significant advances with the introduction of biopolymers in medical device fabrication. This review discusses the impact of biopolymers on the development of ophthalmic devices, such as intraocular lenses, stents, and various prosthetics. Biopolymers are emerging as superior alternatives due to their biocompatibility, mechanical robustness, and biodegradability, presenting an advance over traditional materials with respect to patient comfort and environmental considerations. We explore the spectrum of biopolymers used in ophthalmic devices and evaluate their physical properties, compatibility with biological tissues, and clinical performances. Specific applications in oculoplastic and orbital surgeries, hydrogel applications in ocular therapeutics, and polymeric drug delivery systems for a range of ophthalmic conditions were reviewed. We also anticipate future directions and identify challenges in the field, advocating for a collaborative approach between material science and ophthalmic practice to foster innovative, patient-focused treatments. This synthesis aims to reinforce the potential of biopolymers to improve ophthalmic device technology and enhance clinical outcomes.

Polymers and Biomaterials for Posterior Lamella of the Eyelid and the Lacrimal System

The application of biopolymers in the reconstruction of the posterior lamella of the eyelid and the lacrimal system marks a significant fusion of biomaterial science with clinical advancements. This review assimilates research spanning 2015 to 2023 to provide a detailed examination of the role of biopolymers in reconstructing the posterior lamella of the eyelid and the lacrimal system. It covers the anatomy and pathophysiology of eyelid structures, the challenges of reconstruction, and the nuances of surgical intervention. This article progresses to evaluate the current gold standards, alternative options, and the desirable properties of biopolymers used in these intricate procedures. It underscores the advancements in the field, from decellularized grafts and acellular matrices to innovative natural and synthetic polymers, and explores their applications in lacrimal gland tissue engineering, including the promise of 3D bioprinting technologies. This review highlights the importance of multidisciplinary collaboration between material scientists and clinicians in enhancing surgical outcomes and patient quality of life, emphasizing that such cooperation is pivotal for translating benchtop research into bedside applications. This collaborative effort is vital for restoring aesthetics and functionality for patients afflicted with disfiguring eyelid diseases, ultimately aiming to bridge the gap between innovative materials and their clinical translation.

Culture of primary human meibomian gland cells from surgically excised eyelid tissue

Meibomian gland dysfunction is one of the most common ocular diseases, with therapeutic treatment being primarily palliative due to our incomplete understanding of meibomian gland (MG) pathophysiology. To progress in vitro studies of human MG, this study describes a comprehensive protocol, with detailed troubleshooting, for the successful isolation, cultivation and cryopreservation of primary MG cells using biopsy-size segments of human eyelid tissue that would otherwise be discarded during surgery. MG acini were isolated and used to establish and propagate lipid-producing primary human MG cells. The primary cell viability during culture procedure was maintained through the application of Rho-associated coiled-coil containing protein kinase inhibitor (Y-27632, 10 μM) and collagen I from rat tails. Transcriptomic analysis of differentiated primary human MG cells confirmed cell origin and revealed high-level expression of many lipogenesis-related genes such as stearoyl-CoA desaturase (SCD), ELOVL Fatty Acid Elongase 1 (ELOVL1) and fatty acid synthase (FASN). Primary tarsal plate fibroblasts were also successfully isolated, cultured and cryopreserved. Established primary human MG cells and tarsal plate fibroblasts presented in this study have potential for applications in 3D models and bioengineered tissue that facilitate research in understanding of MG biology and pathophysiology.

Assessment of Laser Parameters to Improve Lid Tension-A Proof of Concept towards Lasercanthoplasty

BACKGROUND

Preliminary clinical work indicates that increasing eyelid tension improves the function of the meibomian glands. The aim of this study was to optimize laser parameters for a minimally invasive laser treatment to increase eyelid tension by coagulation of the lateral tarsal plate and canthus.

METHODS

Experiments were performed on a total of 24 porcine lower lids post mortem, with six lids in each group. Three groups were irradiated with an infrared B radiation laser. Laser-induced lower eyelid shortening was measured and the increase in eyelid tension was assessed with a force sensor. A histology was performed to evaluate coagulation size and laser-induced tissue damage.

RESULTS

In all three groups, a significant shortening of the eyelids after irradiation was noticed (p < 0.0001). The strongest effect was seen with 1940 nm/1 W/5 s, showing -15.1 ± 3.7% and -2.5 ± 0.6 mm lid shortening. The largest significant increase in eyelid tension was seen after placing the third coagulation.

CONCLUSION

Laser coagulation leads to lower eyelid shortening and an increase in lower eyelid tension. The strongest effect with the least tissue damage was shown for laser parameters of 1470 nm/2.5 W/2 s. In vivo studies of this effect have to confirm the efficacy of this concept prior to clinical application.

The Importance of Identifying Meibomian Gland Inversion in Patients With Floppy Eyelid Syndrome

BACKGROUND

Floppy eyelid syndrome (FES) is a common and underdiagnosed condition characterized by eyelid hyperlaxity with reactive palpebral conjunctivitis that can cause ocular irritation. It may be associated with meibomian gland dysfunction (MGD) and secondary tarsal curling, resulting in upper eyelid meibomian gland inversion (MGI) in the absence of obvious marginal entropion.

PURPOSE

To highlight the possible significance of MGI in patients with FES and report findings and outcomes in patients with concomitant MGI and FES undergoing correction of MGI with or without upper eyelid horizontal tightening.

METHODS

Retrospective, 5-year, noncomparative, single-center study of patients with FES and MGI, treated with MGI correction, with or without upper eyelid horizontal tightening, under the supervision of a single surgeon. Preoperative symptoms, surgical outcomes, complication rates, and postoperative symptoms were recorded.

RESULTS

A total of 13 eyes of 9 patients were treated with MGI surgery over the study period. Seven were male. Mean age at the surgery was 63 (range 42-81) years. Two OSs, 3 ODs, and 4 OUs were treated. All patients were "cotton-tip test" positive, and 77% (10/13) had MGI-related superior corneal fluorescein staining. Three patients (33%) had previous standard tightening procedures with recurrence of symptoms within 5 to 24 (mean 16) months. Repeat horizontal tightening had been considered in all these cases before referral to our unit. Mean follow-up was 20 months. Eight patients (88.9%) had improvement of symptoms (n = 3, full resolution; n = 5, partial resolution). All patients demonstrated restoration of the normal anatomical position of the meibomian glands. Superior punctate staining resolved in all eyes.

CONCLUSION

This study provides a proof of concept that upper eyelid MGI can be present and symptomatic in patients with FES. It may help explain cases where symptoms persist or recur early following standard upper eyelid horizontal tightening. Where superior corneal punctate staining and a positive cotton-tip test exist, surgical correction of MGI, alongside horizontal tightening, may provide better, and longer-lasting symptomatic relief. This study provides evidence for the need for a prospective study to evaluate the contribution of MGI in patients with FES.

The histopathological findings in excised upper eyelids of patients with dermatochalasis following collagen cross-linking treatment

PURPOSE

To evaluate the histopathological effects of collagen cross-linking (CCL) on excised skin samples of patients undergoing upper eyelid blepharoplasty due to dermatochalasis.

METHODS

This study examined 74 excised eyelid skin samples from 37 dermatochalasis patients. Following an upper eyelid blepharoplasty, CCL with hypotonic riboflavin (0.1%) was applied. Both treated (right eyelid, CCL group) and untreated eyelid specimen (left eyelid, non-CCL group) sections were stained with hematoxylin-eosin and Masson's trichrome. The sections were evaluated for the following parameters: the collagen status (parallel, oblique, and perpendicular), the distance between collagen fibers, the diameter of collagen fibers, and the length of collagen fibers.

RESULTS

There were no statistically significant differences in the collagen status, the distance between collagen fibers, the diameter of collagen fibers, and the length of collagen fibers between the CCL and non-CCL groups (p > 0.05 for all). Although the lack of statistically significant differences, the structure of the treated eyelid collagen fibers was more parallel in 48% of the participants than in the untreated ones. For male patients, a statistically significant shorter distance between collagen fibers was observed in the CCL group (8.05 ± 2.04 µm) compared to the non-CCL group (9.97 ± 2.33 µm) (p = 0.042).

CONCLUSION

In this study, more parallel collagen structures and tightly packed collagen fibers were detected in eyelid samples following CCL treatment. The authors note that the results of this study may be promising for further research, so the effect of CCL therapy on the eyelid may be an interesting subject for the treatment of non-severe or surgically inadequately corrected dermatochalasis.

Collagen Structural Changes in Rat Tarsus After Crosslinking

Purpose

Surgery is the standard treatment for floppy eyelid syndrome, but crosslinking (CXL) tarsus has recently been proposed as an alternative. To the best of our knowledge, this study is the first to use second-harmonic generation (SHG) microscopy to examine tarsal collagen ex vivo before and after photo-activated crosslinking. To quantify crosslinking, this study examined fluorescence recovery after photobleaching (FRAP), which indirectly measures tissue stiffness.

Methods

Upper eyelid tarsal plates were dissected from 21 Sprague-Dawley rats (total of 42 tarsal plates). Six normal plates were sent for histopathology and SHG imaging; the remaining 36 were crosslinked with phosphate-buffered saline (PBS) alone or riboflavin in PBS (concentrations of 0.1%, 0.3%, and 0.5%). Tissues were irradiated with 365-nm ultraviolet A light (power, 0.45 mW/cm2) for 30 minutes and immediately underwent SHG microscopy. Stiffness was indirectly measured with FRAP using fluorescein isothiocyanate (FITC)-dextran.

Results

SHG imaging of normal tarsus showed that the organization of collagen bundles is complex and varies greatly depending on location. After crosslinking with high-concentration riboflavin (0.5%), collagen fibers showed clear structural changes, becoming more densely packed and wavier compared to control. FRAP half-time to fluorescence recovery was significantly increased (P < 0.05), indirectly indicating increased tissue stiffness. No structural changes were observed after crosslinking with lower riboflavin concentrations of 0.1% and 0.3%.

Conclusions

This is the first report of SHG microscopy used to image tarsus collagen before and after crosslinking. These results highlight collagen structural changes, with effects on tissue stiffness indirectly confirmed by FRAP.

Translational Relevance

Collagen fibers in the tarsus may be a therapeutic target for crosslinking in order to treat symptomatic floppy eyelid syndrome.

Successful Regression in Patients with Progressive Keratoconus by Corneal Crosslinking

BACKGROUND

Since 2019, corneal collagen crosslinking (CXL) is included in the catalog of procedures covered by statutory health insurance in Germany. CXL is an established ophthalmological procedure for the last 20 years. The aim of this investigation was the measurement of progression before and after CXL.

MATERIAL UND METHODS

65 consecutive eyes with progressive keratoconus from 53 patients were included in the retrospective study, which were observed at the University Eye Hospital Tübingen at least two years before and at least two years after CXL. The time of observation took place from October 2009 until March 2018. Parameters of interest had been the best corrected visual acuity (BCVA) and the keratometric values from the elevation maps measured by a Scheimpflug camera.

RESULTS

65 eyes of 53 patients had been documented. The study population included 46 (86.8%) male and 7 (13.2%) female subjects. The mean age was 24 ± 8 years. The averaged observation time between the primary consultation and CXL showed 25 ± 15 months. Preoperatively the mean BCVA pointed out in a significant increase (0.13 ± 0.17 [first visit] vs. 0.23 ± 0.22 [preOP], p < 0.0001) while the mean Kmax resulted in a statistically significant increase (46.34 ± 3.33 dpt [first visit] vs. 48.78 ± 4.17 dpt [preOP], p < 0.0001). The mean thinnest point of the cornea showed a significant decrease (490.48 ± 34.23 µm [first visit] vs. 468.62 ± 29.84 µm [preop], p < 0.0001). Postoperatively the mean BCVA resulted in a significant improvement at the 12th postoperative month in comparison to the preoperative measurement (0.23 ± 0.22 [preOP] vs. 0.16 ± 0.14 [12 months], p = 0.04 respectively 0.17 ± 0.17 [24 months], p = 0.0006). The mean Kmax demonstrated in the 12th postoperative month a significant reduction (48.78 ± 4.17 dpt [preOP] vs. 47.91 ± 3.41 dpt [12 months], p = 0.0009 respectively 48 ± 4.56 dpt [24 months], p = 0.0051). The mean thinnest point of the cornea indicated a decrease at the 12th postoperative month (468.62 ± 29.84 µm [preOP] vs. 459.82 ± 35.88 µm [12 months], p = 0.0078 respectively 453.47 ± 43.39 µm [24 months], p = 0.0227).

CONCLUSION

CXL is a successful procedure for the therapy of progressive keratoconus.

Photochemical Collagen Cross-Linking Reverses Elastase-Induced Mechanical Degradation of Upper Eyelid Tarsus

INTRODUCTION

The floppy eyelid syndrome describes an eyelid disorder characterized by floppy tarsal plates that may be caused by a loss of elastin. The authors attempted to create floppy eyelids by digesting elastin from cadaveric tarsus and then treated them with cross-linking using ultraviolet A and riboflavin.

METHODS

Nine right and 9 left upper eyelids were excised from cadavers. Four vertical strips of central tarsus were removed from each eyelid. One strip of tarsus from each eyelid was treated with 10 units/ml of elastase for 2 hours. Another tarsal strip from each eyelid was immersed in normal saline for 2 hours (control). A third strip from the same eyelid was cross-linked using ultraviolet A at 6 mW/cm for 18 minutes. Finally, a fourth strip of tarsus was cross-linked in the same manner following treatment with elastase for 2 hours. A microtensile load cell was used to measure the Young modulus (stiffness) of each tissue.

RESULTS

Mean (standard deviation) Young modulus for controls (18.9 ± 3.6 MPa) was significantly higher than samples treated with elastase alone (6.6 ± 3.8 MPa, p <0.01). Samples that were treated with cross-linking after elastase had a mean (standard deviation) Young modulus of 26 ± 2.3 MPa, while those treated with cross-linking alone had a mean (standard deviation) Young modulus of 34 ± 0.15 MPa. The differences in stiffness between all groups were significant (p <0.01).

DISCUSSION

Treatment with elastase significantly reduces the stiffness of tarsal plates. This effect is reversed by cross-linking, raising the possibility of using this modality for the treatment of FES.