Ocular surface deficits contributing to persistent epithelial defect after penetrating keratoplasty

Laminar Biomaterial Composite of PVA Cryogel with Amnion as Potential Wound Dressing

Gel dressings, composed of polymers both natural and synthetic, are successfully used in the treatment of burn wounds. They protect the burn wound site against adverse external factors, ensure an adequate level of tissue hydration, have soothing and pain-relieving properties, and also support the healing process and reduce the risk of pathological scars. Another promising material that can be used in the wound-healing process is an amnion membrane. Due to its valuable properties such as protecting the body against bacterial infections and permeability to nutrition, it has found usage in different brands of medicine. In this work, we have combined the beneficial properties of hydrogels and amnion in order to make the laminar dressing that may serve for wound healing. For that purpose, the physically crosslinked cryogel of poly(vinyl alcohol) (PVA) was covered with an amnion membrane. Subsequently, gamma irradiation was performed, leading to the simultaneous internal crosslinking of the hydrogel, its permanent bonding with the amnion, and dressing sterilization. The physicochemical properties of the dressing including gel fraction, swelling, and hardness were studied. Biological tests such as the MTT assay, antimicrobial activity, and histopathological examination confirmed that the obtained material constituted a promising candidate for further, more in-depth studies aiming at wound dressing application.

Preservation of donor corneal epithelium in McCarey-Kaufman medium

Purpose:

To evaluate the role of McCarey-Kaufman (MK) medium in maintaining the integrity of donor corneal epithelium.

Methods:

Nineteen corneal buttons were harvested and stored in MK media at 2°C–8°C for four days. Serial photographs were done every day till the 3^rd day, and images were then analyzed with ImageJ software (LOCI, University of Wisconsin, USA). The area of exposure and epithelial defect (ED) was calculated every day for each corneal button.

Results:

The average age of the donors was 56.5 ± 22.7 years and mean time from death to preservation of the corneal buttons was 7.7 ± 3.1 hours. The average corneal area was 145.6 ± 18.8 mm². The total mean area of exposure was 3.6 ± 4.8, 7.2 ± 9.2, and 9.0 ± 11.9 mm², and ED was 1.7 ± 4.6, 2.8 ± 5.3, and 3.3 ± 5.9 mm² on days 1, 2, and 3, respectively. The percentage of increase in the area of exposure and ED in MK media was 3.71% and 1.1% from day 1 to day 3, respectively. Six out of 19 corneal buttons (31.57%) were utilized for keratoplasties, of which two were utilized in house and four were distributed outside. Of the two utilized corneas, none had epithelial defect on postoperative day 1. Rest 13 corneas were either used for training and research purposes, stored in glycerol media, or discarded.

Conclusion:

Since the percentage change in area of exposure/ED is not much at the end of day 3, corneas stored in MK media can be safely used even after three days of storage. Hence, MK medium serves as an excellent medium in maintaining the integrity of donor corneal epithelium.

[Penetrating keratoplasty]

Penetrating keratoplasty is a tissue transplant commonly performed around the world. For over a century, penetrating keratoplasty has been the standard method of treatment for many corneal diseases causing visual impairment. Recently, lamellar anterior keratoplasty (LAK) or lamellar endothelial (LEK) have become preferable options, resulting in fewer complications and faster functional rehabilitation. While penetrating keratoplasty is less frequently indicated, in favor of these lamellar grafts, it has not necessarily become obsolete, and its use remains appropriate for its chosen indications. Functional results are good if the indication for surgery is properly assessed, therapeutic precautions are taken in view of complications, and follow-up aims to improve initial refractive results as needed.

DMEK after penetrating keratoplasty: cohort with DMEK grafts and descemetorhexis larger than full-thickness graft

PURPOSE

The study aims to evaluate visual outcome, central corneal thickness, and rebubbling rate in a cohort with oversized DMEK grafts after failed penetrating keratoplasty (PK). The unique feature of the study is a descemetorhexis diameter larger than the full-thickness graft, i.e., peripheral to the PK interface.

METHODS

A monocentric, retrospective evaluation of all patients with endothelial graft failure after PK treated with an oversized DMEK graft and descemetorhexis outside of the PK interface (i.e., in host tissue) between January 2015 and July 2019 at the Department of Ophthalmology at the University of Düsseldorf (Germany) was performed.

RESULTS

Eleven eyes of 10 patients were identified. Mean age was 69 years. On average (arithmetic mean ± standard deviation), 1.7 ± 1.0 previous PKs have been performed per eye in this cohort. The mean time between last PK and DMEK was 10.1 ± 7.3 years (range 2 to 23 years). In all cases, the graft diameter exceeded the diameter of the previous PK and descemetorhexis was performed in host tissue, that is, peripheral to the graft-host interface. Rebubbling was performed in 18.2% of the patients (n = 2 eyes) because of central graft detachment. Mean central corneal thickness showed a statistically significant improvement at 5.3 ± 3.5 months after surgery from 688.23 ± 151.01 to 527.75 ± 88 µm (p = 0.002). Visual acuity increased significantly by 5 lines from 1.24 ± 0.5 logMAR (range from 0.5 to 2) to 0.73 ± 0.76 logMAR (range from 0.1 to 2) within 3 months (p = 0.006). Excluding patients without visual potential and transplant failure, visual acuity improved significantly by 8 lines (p < 0.001), and stayed stable until the last follow-up at 15.1 ± 11.4 months (range 6 to 39 months, p < 0.001, n = 8) after surgery.

CONCLUSION

DMEK can be successfully used to treat endothelial cell failure after PK, and can provide good postoperative results with regards to visual acuity. This study shows that stripping of Descemet's membrane (DM) peripheral to the PK interface is surgically feasible. Overlapping, larger DMEK grafts with more endothelial cells can be used without increasing rebubbling rates and may potentially improve long-term graft survival.

The platelet-rich plasma lysate use in the treatment of persistent epithelial defects after keratoplasty

AIM:to evaluate the effectiveness of the platelet-rich plasma lysate (PRP lysate) use in the treatment of persistent epithelial defects (PED) after keratoplasty. MATERIALS AND METHODS:In the study, 60 patients with PED after keratoplasty were included. The 1st group (24 cases)included patients after keratoplasty with low risk of rejection, and the 2nd group 36 cases after keratoplasty with highrisk of rejection. Each group was divided into two subgroupscontrol subgroups 1a (cases 10) and 2a (cases 16), where patients received only standard postoperative therapy, and the main subgroups 1b (cases 14) and 2b (cases 20), in which PRP lysate was prescribed against the background of standard therapy, starting from the Day 15 post-op. As the criterion for effective treatment, complete persistent epithelialization after keratoplasty was considered. RESULTS:The effectiveness of the use of PRP lysate in the subgroup 1b was 85.7%, while complete epithelialization in the control subgroup 1a was recorded in 70%; in the subgroup 2b, complete epithelialization was observed in 55%, in the control subgroup 2ain 43.75%. CONCLUSION:The use of PRP lysate in the treatment of PED after corneal transplantation as an adjuvant therapy is effective and safe in both high and low risk keratoplasty. In the examined category of patients, treatment with blood derivatives increases the frequency and rate of complete epithelialization.

CLEAR - Medical use of contact lenses

The medical use of contact lenses is a solution for many complex ocular conditions, including high refractive error, irregular astigmatism, primary and secondary corneal ectasia, disfiguring disease, and ocular surface disease. The development of highly oxygen permeable soft and rigid materials has extended the suitability of contact lenses for such applications. There is consistent evidence that bandage soft contact lenses, particularly silicone hydrogel lenses, improve epithelial healing and reduce pain in persistent epithelial defects, after trauma or surgery, and in corneal dystrophies. Drug delivery applications of contact lens hold promise for improving topical therapy. Modern scleral lens practice has achieved great success for both visual rehabilitation and therapeutic applications, including those requiring retention of a tear reservoir or protection from an adverse environment. This report offers a practical and relevant summary of the current evidence for the medical use of contact lenses for all eye care professionals including optometrists, ophthalmologists, opticians, and orthoptists. Topics covered include indications for use in both acute and chronic conditions, lens selection, patient selection, wear and care regimens, and recommended aftercare schedules. Prevention, presentation, and management of complications of medical use are reviewed.

[Anterior stromal micropuncture for the treatment of persistent corneal epithelial graft defects after penetrating keratoplasty]

Persistent corneal graft erosion or persistent epithelial corneal defect is a frequent complication of penetrating keratoplasty. Its development can be contributed by the dry eye syndrome, rare blinking, lagophthalmos, symblepharon, viral infection, autoimmune aggression, and the use of epithelial-toxic eye drops. The article presents three clinical observations of patients who developed persistent corneal graft erosion after penetrating keratoplasty. Due to the ineffectiveness of local conservative therapy for more than 3 weeks, anterior stromal corneal micropuncture was performed. After the procedure, there was a gradual epithelial proliferation, complete healing of the corneal surface was observed 10-16 days after the manipulation, the follow-up period was at least 1 year. The mechanism of action of stromal micropuncture is associated with the creation of a porous surface with better adhesion properties, as well as with the activation of the production of extracellular matrix glycoproteins such as fibronectin, type IV collagen and laminin, which are necessary for stable adhesion of the epithelium. The use of stromal micropuncture of the donor flap in the treatment of post-keratoplasty persistent corneal epithelial defect was proposed for the first time.

Changes in ocular surface and Meibomian gland after penetrating Keratoplasty

Background

To acquire desirable outcomes of penetrating keratoplasty (PKP), various factors affecting graft survival, visual function, and subjective symptom should be considered. As ocular surface and meibomian gland function are associated with these factors, this study aims to investigate changes of ocular surface and meibomian gland parameters after PKP.

Methods

This retrospective case series study included 24 eyes of 24 patients who underwent penetrating keratoplasty. Examinations on lipid layer thickness (LLT), meiboscore, tear meniscus area (TMA), tear breakup time (TBUT), corneal fluorescein staining (CFS), Schirmer I test (SIT), Ocular Surface Disease Index (OSDI), and meibomian gland functions were performed before and at 1 week, 1 month, 6 months, and 12 months after surgery.

Results

Compared to baseline (2.9 ± 0.6 s), TBUTs were longer at 1 week (4.4 ± 0.5 s, P = 0.027) and 6 months (4.4 ± 0.5, P = 0.048) after surgery. CFS values improved from baseline (6.5 ± 1.1) to 6 months (3.5 ± 0.6, P = 0.023) and 12 months (3.3 ± 0.7, P = 0.001) after surgery. Meibum quality value worsened at 1 week and 12 months after surgery and meibomian gland expressibility value worsened at 1 week and 6 months after surgery compared to baseline. OSDI scores improved at 6 and 12 months after surgery. Meiboscore showed no change throughout the follow up period. The patients with high preoperative meiboscore had worse meibomian gland expressibility at 6 and 12 months and meibum quality at 6 months postoperatively compared to their baseline and to those of patients with low preoperative meiboscore.

Conclusions

After penetrating keratoplasty, ocular surface parameters including corneal staining, TBUT, and OSDI significantly improved whereas meibomian gland parameters showed deteriorations, which was marked in patients with high preoperative meiboscore. Thus, perioperative management of MGD is recommended for patients who undergo penetrating keratoplasty, especially in patients with advanced MGD.

[Modern biotechnological treatment methods of persistent corneal epithelial defects]

The article reviews modern methods of treatment of persistent corneal epithelial defects and considers the factors involved in the development of this pathology, including the limbal stem cell deficiency, which is likely to play the main role. The most promising treatment methods are described, particularly the use of blood derivatives and cell therapy.

Amnion membrane hydrogel and amnion membrane powder accelerate wound healing in a full thickness porcine skin wound model

There is a need for effective wound treatments that retain the bioactivity of a cellular treatment, but without the high costs and complexities associated with manufacturing, storing, and applying living biological products. Previously, we developed an amnion membrane‐derived hydrogel and evaluated its wound healing properties using a mouse wound model. In this study, we used a full thickness porcine skin wound model to evaluate the wound‐healing efficacy of the amnion hydrogel and a less‐processed amnion product comprising a lyophilized amnion membrane powder. These products were compared with commercially available amnion and nonamnion wound healing products. We found that the amnion hydrogel and amnion powder treatments demonstrated significant and rapid wound healing, driven primarily by new epithelialization versus closure by contraction. Histological analysis demonstrated that these treatments promote the formation of a mature epidermis and dermis with similar composition to healthy skin. The positive skin regenerative outcomes using amnion hydrogel and amnion powder treatments in a large animal model further demonstrate their potential translational value for human wound treatments.

"Therapeutic Penetrating Keratoplasty: A Retrospective Review"

PURPOSE

To report the indications, outcomes, and complications of therapeutic penetrating keratoplasty (Th PK) in patients with corneal perforation and/or nonhealing corneal ulceration.

METHODS

A retrospective review was conducted of 51 eyes of 51 patients undergoing Th PK between January 1, 2006 and April 15, 2016. Data collected included patient demographics, visual acuity (VA), size of the corneal infiltrate and epithelial defect, degree of corneal thinning/perforation, microbiological results, surgical details, and postoperative complications.

RESULTS

The average age at presentation was 56.0 years (range 6-92 years), and most of the patients were females (n=31, 60.8%). Th PK was performed for corneal perforation in 28 eyes (54.9% of cases), nonhealing corneal ulcer in 16 eyes (31.4% of cases), and imminent risk of corneal perforation in 7 eyes (13.7% of cases). Infection was the most common reason for performing a Th PK and was present in 92.3% (47/51) of all cases. Of the infectious cases, the most common etiologies were bacterial (44.7%, 21/47) and fungal (31.9%, 15/47). The most common identifiable risk factor for undergoing a Th PK was a history of contact lens wear, which was seen in 32.7% of patients. Initial anatomic success was achieved in all patients after performing Th PK. Most patients (33/51; 64.7%) had clear grafts at their last follow-up examination. There was an improvement in VA in 70.2% (33/47, where data were available) of the patients at the final postoperative visit compared with the preoperative visit. Average best postoperative VA (1.14±0.88 logarithm of the minimum angle of resolution [LogMAR]; 20/276) was significantly better than the presenting (1.98±0.68 LogMAR; 20/1910) and preoperative (2.18±0.55 LogMAR; 20/3,027) visual acuities (P<0.0001). The most common complication after Th PK was cataract, which was present in 81.8% (27/33) of phakic eyes in which lens status could be assessed, followed by graft failure (47.1%; 24/51), and secondary glaucoma (45.1%; 23/51). Five eyes developed infection in the therapeutic graft, four eyes had persistent corneal epithelial defect at their last follow-up visit, and two eyes underwent evisceration.

CONCLUSIONS

Therapeutic penetrating keratoplasty achieves anatomic success and it is a useful procedure for restoring a stable cornea in cases in which infection fails to heal or when the cornea perforates. Furthermore, Th PK achieves corneal clarity and improves vision in most patients.

Epithelial defects after penetrating keratoplasty in infectious keratitis: An analysis of characteristics and risk factors

To investigate the clinical characteristics, treatment, risk factors of occurrence and graft transparency of corneal epithelial defects after penetrating keratoplasty in patients with infectious keratitis. 594 patients (594 eyes) with infectious keratitis treated by penetrating keratoplasty at Shandong Eye Institute were reviewed retrospectively between January 2008 and January 2018. We investigated the demographic data, diameter and sources of graft, onset time, location, scope, time of healing and treatment of epithelial defects, as well as other postoperative complications and graft clarity. 114 of the 594 grafts (19.2%) that developed epithelial defects were included in the epithelial defects group, while the other 480 patients were classified in the non-defect group. The mean age of patients with epithelial defects was statistically greater than that of patients without epithelial defects (P = 0.006). The epithelial defects group accounted for a larger proportion of male patients (P<0.001). The proportion of patients with a graft diameter >9mm in the epithelial defect group (29.8%) was more than that in the non-defects group (16.3%) (P = 0.001). The incidence of epithelial defects significantly differed among the pathogenic causes of infectious keratitis (P = 0.002). The incidence of graft infection (21.1%, 9.2%, respectively, P<0.001) and graft dysfunction (7.9%, 2.5%, respectively, P = 0.012) in the epithelial defect group was higher than in the non-defects group. Multivariate logistic regression revealed that male sex (P = 0.001), age ≥ 60 years (P = 0.024), graft diameter >9mm (P = 0.001), bacterial (P = 0.039) and herpes simplex keratitis (P = 0.008), rheumatism (P = 0.031) and cancer treated with chemo- or radiotherapy (P = 0.032) were independent risk factors for epithelial defects. Graft clarity after epithelial defects were significantly differed between fungal and viral infections (P<0.001). We found that being an elderly male patient, a graft diameter >9 mm, bacterial and viral keratitis and systemic diseases (including rheumatism and cancer treated with chemo- or radiotherapy) were independent risk factors for postoperative epithelial defects.

Nerve Growth Factor Changes and Corneal Nerve Repair after Keratoplasty

SIGNIFICANCE

Measured tear concentration of nerve growth factor is correlated with postoperative corneal reinnervation among patients who undergo keratoplasty. This may be a future therapeutic target for post-keratoplasty corneal nerve regeneration.

PURPOSE

To determine the relationship between changes in the content of nerve growth factor (NGF) in tear fluid and corneal subepithelial nerve regeneration in patients after keratoplasty.

METHODS

In this retrospective study, 30 eyes of 28 patients (15 males, 13 females; mean age 42.8 [range 16–73] years) who underwent primary keratoplasty for the first time were recruited through the clinics of the Department of Ophthalmology, Jilin University affiliated First Hospital, between May and December 2015. All patients underwent a complete ophthalmic examination preoperatively. Tear fluid samples were collected to detect the content of NFG at different time points in the follow-up period (day 1 preoperatively and days 1, 7, 30, and 90 postoperatively) and analyzed correlations between NFG content and age, infective factors, and variables of the surgical procedure as well as with subepithelial nerve repair at 30 and 90 days postoperatively.

RESULTS

The NFG content in tear fluid on day 1 postoperatively was lower than that on the day preceding surgery; however, it was higher than the preoperative value on postoperative days 7, 30, and 90 (F = 5.046, P < 0.05). Further, the NFG content of tear fluid at 30 days postoperatively correlated with the surgical procedure (coefficient = −2.775, P = 0.010); however, no significant correlation was found on postoperative day 1 (coefficient = −1.315, P> 0.05). At all study time points, the NFG content of tear fluid had no correlation with infective factors or age (P> 0.05). Postoperatively, at day 30, small nerve buds were observed in the periphery of the corneal graft in 13 eyes (43.3% of cases) but not in 17 eyes (56.7% of cases), which showed a significant correlation with the NFG content of tear fluid (coefficient = −3.370, P = 0.010). By postoperative day 90, small nerve buds were observed in the periphery of the corneal graft in 24 eyes (80.0% of cases) and showed a significant correlation with the NFG content of tear fluid (coefficient = −2.750, P = 0.006).

CONCLUSIONS

The NFG content in tear fluid increases with the increasing ratio of small nerve buds indicating corneal nerve regeneration. NFG promotes subepithelial nerve regeneration in patients after keratoplasty.

"Wet" transepithelial phototherapeutic keratectomy in the management of persistent epithelial defects in the graft

Purpose

This study aimed to evaluate the efficacy of “wet” transepithelial phototherapeutic keratectomy (TE-PTK) for treating persistent epithelial defects (PEDs) in the corneal graft following penetrating keratoplasty (PKP).

Methods

This study describes a noncomparative, prospective interventional case series. Patients with post-PKP graft epithelial defects lasting >3 months despite previous treatments with extensive wear soft contact lenses, amniotic membrane transplantation, and tarsorrhaphy were treated with wet TE-PTK. A wet TE-PTK procedure including a “wet ablation” step was performed using the EC-5000 excimer laser. Follow-up visits were at post-PTK days 3, 5, 10, and 30, and at each month thereafter.

Results

Eight patients (8 eyes; 5 men and 3 women; mean age, 51.3±14.3 years; mean follow-up period, 9.1±3.0 months) were included in this study. The mean best-corrected visual acuity was 1.76±0.28 log minimum angle of resolution (logMAR) at baseline and improved to 1.1±0.22 logMAR at 10 days postoperatively (p=0.0156; the improvement was significant). This effect remained stable throughout the remainder of the follow-up period. The mean time from wet TE-PTK to complete reepithelization was 4.3±1.3 days.

Conclusion

Wet TE-PTK appears to be effective for patients with post-PKP PEDs in the corneal graft who have failed conservative measures or previous surgical interventions.

Hepatocyte Growth Factor Suppresses Inflammation and Promotes Epithelium Repair in Corneal Injury

Corneal injuries are among the major causes of ocular morbidity and vision impairment. Optimal epithelial wound healing is critical for the integrity and transparency of the cornea after injury. Hepatocyte growth factor (HGF) is a mitogen and motility factor that primarily regulates epithelial cell function. Herein, we investigate the effect of HGF on proliferation of corneal epithelial cells (CECs) in inflamed conditions both in vitro and in vivo. We demonstrate that HGF not only promotes CEC proliferation in homeostatic conditions but also reverses the anti-proliferative effect of the inflammatory environment on these cells. Furthermore, using a mouse model of ocular injury, we show that HGF treatment suppresses ocular inflammation and actively augments CEC proliferation, leading to improved and accelerated corneal epithelial repair. These findings have potential translational implications and could provide a framework for the development of novel HGF-based therapies for corneal epithelial defects.

Diffusion of Antimicrobials Across Silicone Hydrogel Contact Lenses

OBJECTIVES

To measure the diffusion of topical preparations of moxifloxacin, amphotericin B (AmB), and polyhexamethylene biguanide (PHMB) through silicone hydrogel (SH) contact lenses (CLs) in vitro.

METHODS

Using an in vitro model, the diffusion of three antimicrobials through SH CLs was measured. Diffused compounds were measured using a spectrophotometer at set time points over a period of 4 hr. The amount of each diffused antimicrobial was determined by comparing the experimental value with a standard curve. A biological assay was performed to validate the CL diffusion assay by testing antimicrobial activity of diffused material against lawns of susceptible bacteria (Staphylococcus epidermidis) and yeast (Saccharomyces cerevisiae). Experiments were repeated at least two times with a total of at least four independent replicates.

RESULTS

Our data show detectable moxifloxacin and PHMB diffusion through SH CLs at 30 min, whereas AmB diffusion remained below the limit of detection within the 4-hr experimental period. In the biological assay, diffused moxifloxacin demonstrated microbial killing starting at 20 min on bacterial lawns, whereas PHMB and AmB failed to demonstrate killing on microbial lawns over the course of the 60-min experiment.

CONCLUSIONS

In vitro diffusion assays demonstrate limited penetration of certain anti-infective agents through SH CLs. Further studies regarding the clinical benefit of using these agents along with bandage CL for corneal pathologic condition are warranted.

Preservation of the Corneal Epithelium in Different Corneal Storage Media

PURPOSE

With increasing time, epithelial defects (EDs) develop in virtually all corneas stored in corneal storage media. Optisol GS and Life 4°C are commonly available intermediate storage media used for corneal storage before keratoplasty. Epithelial preservation capabilities of Life 4°C and Optisol GS are compared in this study.

METHODS

Nine pairs of human corneas were harvested, and 1 cornea of each pair was stored in Optisol GS and the other was stored in Life 4°C. The size and frequency of EDs of corneas stored in Optisol GS and Life 4°C were measured over time within the chambers using a backlit approach for 14 to 17 days of storage.

RESULTS

At poststorage days 4, 8, and 12, there were no statistical differences in the percent change in the area of the ED between both groups. Of corneas without initial EDs, 6 of 7 (85.7%) stored in Optisol GS and 5 of 8 (62.5%) stored in Life 4°C developed an ED by the end of the assessment period. At the end of the observation period, there was no significant difference in the change in the percent area of the ED between corneas stored in Optisol GS and Life 4°C [4.3% ± 6.6% and 2.1% ± 2.6%, respectively (P = 0.38)].

CONCLUSIONS

Optisol GS and Life 4°C storage media did not significantly differ in their abilities to preserve the corneal epithelium of the donor tissue for up to 17 days. Most corneas stored in both cold-storage media developed EDs within the 14-day observation period.

Plasma Rich in Growth Factors for the Treatment of Ocular Surface Diseases

PURPOSE

The purpose of this work is to describe and review the technology of plasma rich in growth factors (PRGF), a novel blood derivative product, in the treatment of ocular surface disorders.

METHODS

To demonstrate the importance of this technology in the treatment of ocular pathologies, a thorough review of the preclinical and clinical literature results obtained following use of the different therapeutic formulations of PRGF was carried out. A literature search for applications of PGRF plasma in the ophthalmology field was carried out using the PubMed database.

RESULTS

PRGF involves the use of patient's own biologically active proteins, growth factors, and biomaterial scaffolds for therapeutic purposes. This procedural technology is gaining interest in regenerative medicine due to its potential to stimulate and accelerate the tissue healing processes. The versatility and biocompatibility of this technology opens the door to a personalized medicine on ocular tissue regeneration. This review discusses the state of the art of the new treatments and technologies developed to promote ocular surface tissue regeneration. The standardized protocol that has been developed to source eye drops from PRGF technology is also described. The preclinical research, together with the most relevant clinical applications are summarized and discussed.

CONCLUSIONS

The preliminary results suggest that the use of PRGF to enhance ocular tissue regeneration is safe and efficient.

Dexamethasone diffusion across contact lenses is inhibited by Staphylococcus epidermidis biofilms in vitro

PURPOSE

This study was designed to measure the impact of bacterial biofilms on diffusion of an ocular therapeutic through silicone hydrogel bandage lenses in vitro.

METHODS

An assay was designed to study the passage of a commonly used steroid, dexamethasone, through silicone hydrogel soft contact lenses. Diffused dexamethasone was measured using a spectrophotometer over a period of 18 hours and quantified using a standard curve. This assay was performed with control and Staphylococcus epidermidis biofilm-coated contact lenses comprised of lotrafilcon A and methafilcon. Biofilms were formed in brain heart infusion broth supplemented with D-glucose.

RESULTS

The presented data validate a simple in vitro model that can be used to measure the penetration of a topical therapeutic through silicone hydrogel soft contact lenses. Using this model, we measured a reduction in dexamethasone diffusion up to 88% through S. epidermidis biofilm-coated silicone hydrogel lenses compared with control lenses.

CONCLUSIONS

The results of this in vitro study demonstrate that bacterial biofilms impede dexamethasone diffusion through silicone hydrogel contact lenses and warrant future studies regarding the clinical benefit of using ocular therapeutics in the setting of bandage contact lens use for corneal epithelial defects.

All-trans retinoid acid promotes allogeneic corneal graft survival in mice by regulating Treg-Th17 balance in the presence of TGF-β

BACKGROUND

All-trans retinoid acid (ATRA) has been proven to skew Regulatory T cell-T helper 17 cell (Treg-Th17) balance toward Treg in vitro, favoring graft acceptance. However, its in vivo effect after solid organ transplantation is under investigation.

RESULTS

BALB/c mice were given orthotopic corneal grafts from C57BL/6 donors, and recipient mice were administered with ATRA, TGF-β, and the combination of both agents for 8 weeks after surgery. We found that a mixed treatment of ATRA and TGF-β significantly promoted graft survival. Moreover, with the presence of TGF-β, ATRA upregulated CD4(+)CD25(+)Foxp3(+)Treg cells and suppressed Th17 cells in the blood, spleen and draining lymph nodes of recipient mice, as well as enhanced the Foxp3 expression and inhibited the RORγt expression in grafts and peripheral blood mononuclear cells (PBMCs). Simultaneously, increased number of Foxp3+ cells and decreased number of IL-17+ cells in conjunctiva were found in recipients with mixed treatment, along with reduced IL-17 level in serum and aqueous humor and increased IL-10 level in aqueous humor. Tregs isolated from recipient mice treated with ATRA + TGF-β presented the strongest suppressive activity in vitro.

CONCLUSIONS

Combined application of ATRA and TGF-β may shift the Th17-Treg balance toward Tregs, hence facilitating the induction of immunological tolerance after allogenic corneal transplantation and representing a potential therapeutic approach in the treatment of posttransplant rejection.

Corneal nerves in health and disease

Corneal nerves are responsible for the sensations of touch, pain, and temperature and play an important role in the blink reflex, wound healing, and tear production and secretion. Corneal nerve dysfunction is a frequent feature of diseases that cause opacities and result in corneal blindness. Corneal opacities rank as the second most frequent cause of blindness. Technological advances in in vivo corneal nerve imaging, such as optical coherence tomography and confocal scanning, have generated new knowledge regarding the phenomenological events that occur during reinnervation of the cornea following disease, injury, or surgery. The recent availability of transgenic neurofluorescent murine models has stimulated the search for molecular modulators of corneal nerve regeneration. New evidence suggests that neuroregenerative and inflammatory pathways in the cornea are intertwined. Evidence-based treatment of neurotrophic corneal diseases includes using neuroregenerative (blood component-based and neurotrophic factors), neuroprotective, and ensconcing (bandage contact lens and amniotic membrane) strategies and avoiding anti-inflammatory therapies, such as cyclosporine and corticosteroids.