Autologous serum for the treatment of corneal epithelial abrasions in diabetic patients undergoing vitrectomy

Protective effect of pituitary adenylate cyclase activating polypeptide in diabetic keratopathy

Diabetic keratopathy (DK) is the major complication of the cornea characterizing diabetes-affected patients. This ocular pathology is correlated with the hyperglycemic state leading to delayed corneal wound healing and recurrent corneal ulcers. Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide with widespread distribution throughout the body, and exerting cytoprotective effects in the neural and non-neuronal parts of the eye, including the cornea. The purpose of the present study was to investigate whether changes in PACAP expression can concur for delayed epithelial wound healing in diabetic cornea and whether the protective effect of the peptide could be mediated through the activation of the EGFR signaling pathway, which has been reported to be impaired in DK. Expression and distribution of PACAP, PAC1R, and EGFR were investigated through immunohistochemistry analysis in the cornea of normal and diabetic rats. The role of the peptide on wound healing during DK was evaluated in an in vitro model represented by rabbit corneal epithelial cells grown in high glucose conditions. Western blotting and immunofluorescence analysis were used to examine the ability of PACAP to induce the activation of the EGFR/ERK1/2 signaling pathway. Our results showed that in diabetic cornea the expression of PACAP, PAC1R, and EGFR is drastically reduced. The treatment with PACAP via PAC1R activation enhanced cell viability and corneal epithelium wound healing in cells grown under high glucose conditions. Furthermore, both EGFR and ERK1/2 signaling was induced upon the peptide treatment. Overall, our results showed the trophic efficiency of PACAP for enhancing the corneal epithelium re-epithelialization suggesting that the peptide could be beneficially valuable as a treatment for DK.

Oxidative stress in the eye and its role in the pathophysiology of ocular diseases

Oxidative stress occurs through an imbalance between the generation of reactive oxygen species (ROS) and the antioxidant defense mechanisms of cells. The eye is particularly exposed to oxidative stress because of its permanent exposure to light and due to several structures having high metabolic activities. The anterior part of the eye is highly exposed to ultraviolet (UV) radiation and possesses a complex antioxidant defense system to protect the retina from UV radiation. The posterior part of the eye exhibits high metabolic rates and oxygen consumption leading subsequently to a high production rate of ROS. Furthermore, inflammation, aging, genetic factors, and environmental pollution, are all elements promoting ROS generation and impairing antioxidant defense mechanisms and thereby representing risk factors leading to oxidative stress. An abnormal redox status was shown to be involved in the pathophysiology of various ocular diseases in the anterior and posterior segment of the eye. In this review, we aim to summarize the mechanisms of oxidative stress in ocular diseases to provide an updated understanding on the pathogenesis of common diseases affecting the ocular surface, the lens, the retina, and the optic nerve. Moreover, we discuss potential therapeutic approaches aimed at reducing oxidative stress in this context.

A Low-Fat/Sucrose Diet Rich in Complex Carbohydrates Reverses High-Fat/Sucrose Diet-Induced Corneal Dysregulation

High-fat/sucrose diet feeding in mice causes loss of corneal nerve function and impairs corneal wound healing. While changing to a diet with a low fat/sugar composition and enrichments in complex carbohydrates mitigates the reduction in nerve function, it remains to be determined if it has an effect on corneal wound healing. In this study, 6-week-old C57BL/6 male mice were fed either a normal diet or a high-fat/sucrose diet for 20 weeks. A third group (diet reversal) was placed on a high-fat/sucrose diet for 10 weeks followed by a normal diet for an additional 10 weeks. A central corneal epithelial abrasion wound was created, and wound closure was monitored. Neutrophil and platelet recruitment was assessed by immunofluorescence microscopy. Mice fed the high-fat/sucrose diet-only had greater adiposity (p < 0.005) than normal diet-only fed mice; diet reversal markedly reduced adiposity. Following corneal abrasion, wound closure was delayed by ~6 h (p ≤ 0.01) and, at 30 h post-wounding, fewer neutrophils reached the wound center and fewer extravascular platelets were present at the limbus (p < 0.05). Diet restored normal wound closure and neutrophil and platelet influx in the injured cornea. These data suggest compositional changes to the diet may be an effective diet-based therapeutic strategy for maintaining or restoring corneal health.

[Corneal regeneration: is there a place for tissues of perinatal origin?]

The article reviews the main properties of the cornea and the mechanisms of its physiological regeneration and repair in response to damage and describes the most promising methods of treatment aimed at stimulating limbal stem cells and based on the use of native tissues of perinatal origin, umbilical cord mesenchymal stromal cells, and cell-free therapeutic products.

Pycnogenol a promising remedy for diabetic keratopathy in experimentally induced corneal alkali burns in diabetic rats

AIM

This study aimed to investigate the efficiency of topically applied pycnogenol (PYC) in healing the standardized alkaline corneal ulcer in diabetic and normal rats.

MATERIALS AND METHODS

The corneal alkali-burn injury (CA-I) model was unilaterally developed in Wistar rats by filter paper saturated with 0.01 M of NaOH and touching the eyes for 45 s. Rats were divided into four groups: Normal control (NC), normal PYC (NPYC), diabetic control (DC), and diabetic PYC (DPYC). Both NPYC and DPYC groups were daily treated with PY eye drops three times, whereas NC and DC ones were treated with ordinary saline for six successive days.

RESULTS

The wound healing of corneal epithelial was improved in the NPYC group compared to the NC group. Meanwhile, it was significantly improved (P < 0.05) in the DPYC group than in the DC group. Histological examination revealed that corneal re-epithelialization was more accomplished in the DPYC group than in the DC group. In addition, the inflammatory cells were augmented in the DC group more than those in the DPYC one.

CONCLUSION

The findings obtained revealed the efficiency of PYC for enhancing the corneal re-epithelialization and reducing the inflammatory reaction post alkali burn in rats, and thus it could be beneficially valuable as a treatment for the diabetic keratopathy.

Corneal epithelial defects following vitreoretinal surgery: incidence and outcomes from the DISCOVER study

AIM

To investigate the incidence, risk factors, clinical course, and outcomes of corneal epithelial defects (CED) following vitreoretinal surgery in a prospective study setting.

METHODS

This was a post-hoc analysis of all participants in DISCOVER intraoperative optical coherence tomography study. Subjects with CED 1d after surgery without intraoperative corneal debridement was defined as the postoperative CED group. Subjects who underwent intraoperative debridement were defined as intraoperative debridement group. Eyes were matched 2:1 with controls (eyes without postoperative CED) for comparative assessment. The primary outcomes were the incidence of CED on postoperative day one and the incidence of required intraoperative debridement. Secondary outcomes included time to defect closure, delayed healing (>2wk), visual acuity (VA) and presence of scarring at one year and cornea consult.

RESULTS

This study included 856 eyes that underwent vitreoretinal surgery. Intraoperative corneal debridement was performed to 61 (7.1%) subjects and postoperative CED developed spontaneously in 94 (11.0%) subjects. Significant factors associated with postoperative CED included prolonged surgical duration (P=0.003), diabetes mellitus (P=0.04), postoperative ocular hypotension (P<0.001). Prolonged surgical duration was associated with intraoperative debridement. Delayed defect closure time (>2wk) was associated with corneal scar formation at the end of the 1y in all epithelial defect subjects (P<0.001). The overall rate of corneal scarring for all eyes undergoing vitrectomy was 1.8%.

CONCLUSION

Prolonged duration of surgery is the strongest factor associated with both intraoperative debridement and spontaneous postoperative CED. Delayed defect closure is associated with a greater risk of corneal scarring at one year. The overall rate of corneal scarring following vitrectomy is low at <2%.

Bioluminescence Imaging of Matrix Metalloproteinases-2 and -9 Activities in Ethanol-injured Cornea of Mice

BACKGROUND/AIM

This study aimed to investigate the usefulness of in vivo bioluminescence imaging (BLI) to examine the role of matrix metalloproteinases (MMP)-2 and MMP-9 activation in the development and healing of ethanol-induced damage in the cornea of mice.

MATERIALS AND METHODS

Mouse corneal injury was induced by topical treatment with 20% ethanol. BLI was obtained from the ocular region of mice intravenously injected with an active-MMP-2/9 probe. In vivo results were validated in primary corneal epithelial cells.

RESULTS

BLI indicated that treatment of the eye with 20% ethanol elevated MMP-2/9 activity, which was inhibited by the application of eye drops (hyaluronic acid and serum). Treatment of corneal epithelial cells with 20% ethanol-increased the activities of MMP-2 and MMP-9, which were also inhibited by eye drops.

CONCLUSION

BLI can be applied in vivo in mice with corneal injury to examine the activity of MMPs and clarify the efficacy of eye drops.

The Use of Autologous Serum Eye Drops after Epithelium-off Corneal Collagen Crosslinking

SIGNIFICANCE

After epithelium-off crosslinking (CXL), epithelial closure time and post-operative pain are an important issue in terms of possible complications and patient comfort. We report a prospective randomized study about the use of autologous serum eye drops after CXL.

PURPOSE

This study aims to evaluate the effect of autologous serum eye drops on epithelial healing and post-operative pain after CXL.

METHODS

Sixty patients diagnosed as having progressive keratoconus and treated with accelerated CXL (9 mW/cm for 10 minutes) randomly received 20% autologous serum eye drops (autologous serum group, n = 30) or artificial tears (control group, n = 30). Patients were evaluated every day after the surgery, and the day of epithelial closure was recorded. All patients were asked to report the maximum pain level using the Wong-Baker FACES Pain Rating Scale at the end of each day until the epithelial closure was completed. The change in topographic parameters and haze were recorded at 6 months.

RESULTS

The mean epithelial closure time was significantly lower in the autologous serum group than in the control group (2.37 ± 0.49 and 2.67 ± 0.47 days, respectively; P = .02). There was a statistically significant difference between the pain scores in the first and second days of surgery between the two groups (first-day autologous serum autologous serum group: 2.80 ± 0.66 and control group: 3.50 ± 0.82, P = .01; second-day autologous serum group: 1.73 ± 0.69 and control group: 2.20 ± 0.76, P = .02). Pre-operative and post-operative topographic parameters and haze at 6 months were similar between the two groups (P > .05 for all).

CONCLUSIONS

Use of autologous serum eye drops after CXL accelerates epithelial healing and reduces post-operative pain. Shortening the duration of epithelial closure would be beneficial in reducing possible complications and increasing patient comfort.

Systemic diseases and the cornea

There is a number of systemic diseases affecting the cornea. These include endocrine disorders (diabetes, Graves' disease, Addison's disease, hyperparathyroidism), infections with viruses (SARS-CoV-2, herpes simplex, varicella zoster, HTLV-1, Epstein-Barr virus) and bacteria (tuberculosis, syphilis and Pseudomonas aeruginosa), autoimmune and inflammatory diseases (rheumatoid arthritis, Sjögren's syndrome, lupus erythematosus, gout, atopic and vernal keratoconjunctivitis, multiple sclerosis, granulomatosis with polyangiitis, sarcoidosis, Cogan's syndrome, immunobullous diseases), corneal deposit disorders (Wilson's disease, cystinosis, Fabry disease, Meretoja's syndrome, mucopolysaccharidosis, hyperlipoproteinemia), and genetic disorders (aniridia, Ehlers-Danlos syndromes, Marfan syndrome). Corneal manifestations often provide an insight to underlying systemic diseases and can act as the first indicator of an undiagnosed systemic condition. Routine eye exams can bring attention to potentially life-threatening illnesses. In this review, we provide a fairly detailed overview of the pathologic changes in the cornea described in various systemic diseases and also discuss underlying molecular mechanisms, as well as current and emerging treatments.

Serum eye drops for the treatment of ocular surface diseases: a systematic review and meta-analysis

BACKGROUND

The use of blood-derived eye drops for topical treatment of ocular surface diseases has progressively increased in recent years.

MATERIALS AND METHODS

To evaluate the use of serum eye drops in ocular surface disorders, we performed a systematic search of the literature.

RESULTS

In this systematic review, we included 19 randomised controlled trials (RCTs) investigating the use of serum eye drops in 729 patients compared to controls. For the quantitative synthesis, we included only 10 RCTs conducted in patients with dry eye syndrome comparing autologous serum to artificial tears. At 2-6 weeks, no clear between-group differences in Schirmer test (MD 1.05; 95% CI: -0.17-2.26) and in fluorescein staining (MD -0.61; 95% CI: -1.50-0.28) were found (very low-quality evidence, down-graded for inconsistency, serious risk of biases, and serious imprecision). Slightly higher increase in tear film break-up time (TBUT) scores in autologous serum compared to control (MD 2.68; 95% CI: 1.33-4.03), and greater decrease in ocular surface disease index (OSDI) in autologous serum compared to control (MD -11.17; 95% CI: -16.58 - -5.77) were found (low quality evidence, down-graded for serious risk of bias, and for inconsistency). For the Schirmer test, fluorescein staining and TBUT, data were also available at additional follow-up timing (2-12 months): no clear between-group differences were found, and the quality of the evidence was graded as low/very-low.

CONCLUSIONS

In patients with dry eye syndrome, it is unclear whether or not the use of autologous serum compared to artificial tears increases Schirmer test and fluorescein staining scores at short-term and medium-/long-term follow up. Some benefit at short-term follow up for the outcome of TBUT and OSDI was observed, but the quality of the evidence was low.

Blood-Based Treatments for Severe Dry Eye Disease: The Need of a Consensus

The use of blood-based eye drops as therapy for various diseases of the ocular surface has become increasingly popular in ophthalmic practice during recent years. The rationale for their use is based on the promotion of cellular proliferation and migration thanks to the supply of metabolically active substances, in particular growth factors. Blood-derived eye drops have been used for the treatment of several ocular surface disorders, such as dry eye disease, corneal ulcer, persistent epithelial defect, neurotrophic keratitis, ocular surface burn, recurrent corneal erosion, and limbal stem-cell deficiency. Both autologous (from patients themselves) and heterologous (from adult donors or from cord blood sampled at birth)-derived products exist, and each source has specific pros and cons. Despite an extensive literature, several issues are still under debate and the aim of this manuscript is to review the indications, preparation methods and storage, characterization of content, rationale for clinical outcomes, patient stratification, length of treatment, and rationale for repeated treatments at disease relapse. A rationale based on a "5 Ws and 2 Hs" protocol is proposed as a way of thinking, with the attempt to clarify Who, Why, When, Where, What, and How to use these treatment options.

Diabetes inhibits corneal epithelial cell migration and tight junction formation in mice and human via increasing ROS and impairing Akt signaling

Corneal wounds usually heal quickly; but diabetic patients have more fragile corneas and experience delayed and painful healing. In the present study, we compared the healing capacity of corneal epithelial cells (CECs) between normal and diabetic conditions and the potential mechanisms. Primary murine CEC derived from wild-type and diabetic (db/db) mice, as well as primary human CEC were prepared. Human CEC were exposed to high glucose (30 mM) to mimic diabetic conditions. Cell migration and proliferation were assessed using Scratch test and MTT assays, respectively. Reactive oxygen species (ROS) production in the cells was measured using dichlorofluorescein reagent. Western blot was used to evaluate the expression levels of Akt. Transepithelial electrical resistance (TEER) and zonula occludens-1 (ZO-1) expression were used to determine tight junction integrity. We found that the diabetic CEC displayed significantly slower cell proliferation and migration compared with the normal CEC from both mice and humans. Furthermore, ROS production was markedly increased in CEC grown under diabetic conditions. Treatment with an antioxidant N-acetyl cysteine (NAC, 100 μM) significantly decreased ROS production and increased wound healing in diabetic CEC. Barrier function was significantly reduced in both diabetic mouse and human CEC, while NAC treatment mitigated these effects. We further showed that Akt signaling was impaired in diabetic CEC, which was partially improved by NAC treatment. These results show that diabetic conditions lead to delayed wound-healing capacity of CEC and impaired tight junction formation in both mice and human. Increased ROS production and inhibited Akt signaling may contribute to this outcome, implicating these as potential targets for treating corneal wounds in diabetic patients.

Recurrent corneal erosion syndrome

Recurrent corneal erosion syndrome (RCES) is a disorder characterised by a dysfunctional epithelial ecosystem. It often begins after trauma, or in the setting of epithelial basement membrane degeneration or dystrophy. Historically, RCES has been understood as a structural derangement of the anterior corneal architecture. More recently, studies have demonstrated the important role of neuropeptides in corneal homoeostasis. Thus, RCES may also be understood as a disorder of corneal epithelial cell biology. Management of RCES can be challenging, but newer therapies have demonstrated improved efficacy for this condition. This review examines the aetiology and pathogenesis of RCES, and provides an update on current and emerging treatment modalities for the management of this disorder.

Experimental modeling of cornea wound healing in diabetes: clinical applications and beyond

Diabetes mellitus is the most common cause of blindness in working age populations worldwide. While much of the focus for public health has been on secondary prevention in sight-threatening diabetic retinopathy, the cornea, including its epithelium and nerves, represents a major site of damage by chronic hyperglycemia. On injury, the diabetic cornea exhibits a delayed wound-healing response, as well as an altered ocular surface immune response. This suggests a potential association between the dysfunctional wound healing response and altered inflammation on the ocular surface. However, the presence of potential confounders makes this association difficult to investigate in human epidemiological studies. Thus, we turn to animal diabetic models for a better understanding. In this review, 20 original studies, published between 2008 and 2018, describe in vivo and in vitro models of diabetic cornea disease. We compared different models of diabetic cornea wound healing and discussed the relative strengths and drawbacks of each model. A number of molecular and cellular components involved in the corneal wound healing response that are altered in the presence of diabetes have been identified in the reviewed studies. Particularly, altered corneal epithelial protein concentrations of lumician and occludin were detected in diabetic eyes compared with controls. Additionally, the importance of IL-1β in modulating the inflammatory response after corneal injury in patients with diabetes and controls was further elucidated. Meanwhile, abnormal P2×7 receptor localization and decreased corneal sub-basal nerve density in diabetic eyes were shown to contribute to altered corneal nerve signaling after injury and thus affecting the wound healing response. Finally, the discovery of the therapeutic effects of topically administered aloe vera, Serpine 1, Resolvin D1 (RvD1), pigment epithelium-derived factor (PEDF) and Pro-His-Ser-Arg-Asn in diabetic animal models of cornea epithelial and nerve injury provide encouraging evidence for the future availability of effective treatment for diabetic keratopathy.

Influence of diabetes mellitus on anterior segment of the eye

Diabetes mellitus (DM) has been emerging as one of the most serious health problems worldwide. Ocular complications of DM are currently one of the major causes of blindness in developed countries, among which diabetic retinopathy is relatively well studied and understood. However, although ocular surface complications of DM are common, diabetic complications of anterior segment of the eye, such as, cornea, conjunctiva, and lacrimal glands, are often overlooked. DM is associated with progressive damage to corneal nerves and epithelial cells, which increases the risk of anterior segment disorders including dry eye disease, corneal erosion, persistent epithelial defects, and even sight-threatening corneal ulcer. In this review, the authors will discuss the association of DM with disorders of anterior segment of the eye. Studies indicating the value of corneal nerve assessment as a sensitive, noninvasive, and repeatable biomarker for diabetic neuropathy will also be introduced. In addition, treatment modalities of anterior segment disorders associated with DM is discussed. The studies introduced in this review suggest that early and periodic screening of the anterior segment of the eye, as well as the retina, is important for the optimal treatment of DM.

Application of autologous serum eye drops after pterygium surgery: a prospective study

PURPOSE

The study aims to determine the effect of 50% autologous serum drops (ASD) on corneal healing and patient comfort following pterygium surgery.

METHODS

Fifty eyes of 50 patients who underwent pterygium excision combined with autologous conjunctival graft were included in this prospective randomized study: in 25 eyes, 50% ASD. In the remaining 25 eyes, conventional artificial tears (CAT) were applied postoperatively until corneal epithelium had completely epithelialized. Corneal epithelium healing speed, visual analog scale (VAS) for postoperative pain assessment, conjunctival inflammation, and recurrences were evaluated. Patients were followed up for 6 months.

RESULTS

Mean corneal epithelium closure time was 3.16 ± 0.37 days (range 3 and 4 days) in ASD group and 4.96 ± 0.84 days in CAT group (range 4 and 6 days), and the difference was statistically significant (p < 0.001). VAS scores were significantly lower in ASD group than CAT group in the first 5 days after surgery. In 9 of 50 eyes, moderate conjunctival inflammation continued 1 month: 4 (16%) in ASD group and 5 (20%) in CAT group (p = 0.713). In total, pterygium recurrence was seen in 5 (10%) eyes: 2 eyes (8%) in ASD group and 3 eyes (12%) in CAT group (p = 0.637).

CONCLUSION

ASD accelerated corneal epithelial healing following pterygium surgery. ASD group had lesser pain that was seem to be related with accelerated corneal epithelial healing.

Remodeling of the Corneal Epithelial Scaffold for Treatment of Persistent Epithelial Defects in Diabetic Keratopathy

<b><i>Background:</i></b> To develop a strategy based on surgical removal of a degenerated corneal epithelial scaffold for treatment of persistent epithelial defects (PEDs) in diabetic keratopathy. <b><i>Case Presentation:</i></b> Three diabetic patients with PEDs were initially treated with eyedrops containing the fibronectin-based peptide PHSRN (Pro-His-Ser-Arg-Asn) or both the substance P-derived peptide FGLM-NH₂ and the insulin-like growth factor-1-derived peptide SSSR. A degenerated Bowman’s layer or calcified lesion thought to be responsible for incomplete healing was surgically removed after confirmation of reactivity to the peptide eyedrops. All three patients achieved complete epithelial wound closure after surgery. Two cases treated by phototherapeutic keratectomy or lamellar keratoplasty did not show PED recurrence during 6 or 36 months of follow-up, respectively. One case treated by mechanical removal of a degenerated Bowman’s layer manifested recurrence after 1 month, but resurfacing of the defect was again achieved after repeat surgery. <b><i>Conclusion:</i></b> We propose a new strategy for treatment of diabetic PEDs based on surgical remodeling of the corneal epithelial scaffold for patients who respond to peptide eyedrops but fail to achieve wound closure.

Promotion of Corneal Epithelial Wound Healing in Diabetic Rats by the Fibronectin-Derived Peptide PHSRN

PURPOSE

Topical application of the fibronectin-derived peptide PHSRN facilitates corneal epithelial wound healing in healthy animals and in patients with nonhealing epithelial defects. We have now examined the effect of PHSRN eye drops on the healing of corneal epithelial wounds in diabetic rats.

METHODS

Wistar rats were injected intraperitoneally with streptozotocin to induce diabetes or with a vehicle as a control. Four weeks after confirmation of the corresponding presence or absence of glycosuria, a 3-mm-diameter portion of the corneal epithelium of the right eye was excised and eye drops containing PHSRN (200 μM) or phosphate-buffered saline (PBS) vehicle were administered to the injured eye every 6 hours.

RESULTS

The area of the epithelial defect did not differ significantly among the 4 experimental groups (diabetic or nondiabetic rats treated with PHSRN or vehicle) at 12 hours after wounding. At 18 hours, however, the area of the defect in diabetic rats treated with PHSRN (0.50 ± 0.34 mm) was significantly (P < 0.05) smaller than that in diabetic rats treated with PBS (1.06 ± 0.42 mm) and was similar to that in nondiabetic rats treated with PBS (0.60 ± 0.23 mm). The decrease in the size of the epithelial defect in diabetic rats treated with PHSRN was also found to be dependent on the dose of the peptide.

CONCLUSIONS

Administration of PHSRN significantly facilitated healing of corneal epithelial wounds in diabetic rats, which suggests that PHSRN eye drops warrant further investigation as a treatment option for patients with diabetic keratopathy.

Diabetic complications in the cornea

Diabetic corneal alterations, such as delayed epithelial wound healing, edema, recurrent erosions, neuropathy/loss of sensitivity, and tear film changes are frequent but underdiagnosed complications of both type 1 (insulin-dependent) and type 2 (non-insulin-dependent) diabetes mellitus. The disease affects corneal epithelium, corneal nerves, tear film, and to a lesser extent, endothelium, and also conjunctiva. These abnormalities may appear or become exacerbated following trauma, as well as various surgeries including retinal, cataract or refractive. The focus of the review is on mechanisms of diabetic corneal abnormalities, available animal, tissue and organ culture models, and emerging treatments. Changes of basement membrane structure and wound healing rates, the role of various proteinases, advanced glycation end products (AGEs), abnormal growth and motility factors (including opioid, epidermal, and hepatocyte growth factors) are analyzed. Experimental therapeutics under development, including topical naltrexone, insulin, inhibitors of aldose reductase, and AGEs, as well as emerging gene and cell therapies are discussed in detail.

Factors associated with corneal epithelial defects after pars plana vitrectomy

PURPOSE

To investigate the risk factors associated with corneal epithelial defects (CED) and delayed healing (exceeding 1 week) following pars plana vitrectomy (PPV).

METHODS

This retrospective study enrolled patients who underwent PPV at a single center in Taiwan between 2011 and 2012. Medical records were reviewed, including demographic, underlying disease, surgical indication, operation parameters, and existence of CED. These data were statistically analyzed. All patients were evaluated during follow-ups at day 1 and week 1 after PPV. Patients with persistent CED 1 week after PPV were diagnosed with delayed healing.

RESULTS

A total of 255 patients were included in the study, consisting of 139 men and 116 women, with a mean age of 56.9 years. PPV was performed under the indications of rhegmatogenous retinal detachment (RRD), diabetic retinopathy, or vitreoretinal interface disease. Out of 255 eyes, 59 developed CED 1 day after surgery (23.1%), and CED was associated with younger age, diabetes mellitus (DM), RRD, longer duration of surgery, and silicon oil use during surgery. Among them, seven patients (11.9%) demonstrated delayed healing, which was associated with a higher rate of DM (p = 0.085), compared to patients who healed within 1 week.

CONCLUSION

Patients with RRD, longer duration of surgery, and DM may be at risk of developing CED after PPV. In addition, patients with DM demonstrated a higher incidence of delayed corneal healing.

Autologous serum eye drops for the treatment of ocular surface disease

OBJECTIVE

To examine the evidence for the role of autologous serum eye drops (ASD) in disease of the ocular surface.

METHODS

A search of the literature published through May 2014 using PubMed, the ISI Web of Knowledge database, and the Cochrane Library was performed. Qualified articles were selected after review of titles, abstracts, and references.

RESULTS

There was a significant improvement in either symptoms or some of the clinical examination findings, including tear breakup time, corneal staining, Schirmer values, and impression cytology in eyes with persistent corneal epithelial defect, graft-versus-host disease, Sjögren- and non-Sjögren-related dry eye disease, limbal stem-cell deficiency, recurrent corneal erosion, superior limbic keratoconjunctivitis, and postrefractive surgery. However, most of the studies were nonrandomized in nature.

CONCLUSIONS

Despite the paucity of strong supporting evidence from randomized double-masked clinical studies, there seems to be a trend toward superiority of ASD in alleviating some of the clinical signs and symptoms associated with corneal pathology in a variety of conditions that affect the ocular surface compared with conventional lubricating drops/ointments.

Aloe vera gel facilitates re-epithelialization of corneal alkali burn in normal and diabetic rats

Purpose

To investigate the efficacy of topical applied aloe vera (AV) and to facilitate the repair of the standardized alkaline corneal ulcer in normal and diabetic rats.

Materials and methods

The corneal alkali-burn injury model was established unilaterally in Wistar rats by filter paper saturated with 0.01 M NaOH contacting the eyes for 45 seconds. Rats were divided into four groups: normal control (NC), normal AV (NAV), diabetic control (DC), and diabetic AV (DAV). NAV and DAV groups were treated with AV gel eye drops four times daily, and NC and DC groups were treated with normal saline for 3 days. Corneal epithelial wound closure and degree of edema were recorded using slit lamp and optical coherence tomography at 0, 24, 48, and 72 hours postwounding. Histological examination was conducted to evaluate the degree of inflammation and the healing effect.

Results

Corneal epithelial wound healing was better in the NAV group than in the NC group, and it was significantly higher in the DAV group than in the DC group (P<0.05). In comparison to the DC group, DAV treated with AV demonstrated a marked reduction in edema at 48 and 72 hours. Histologically, corneal re-epithelialization was complete and higher in DAV group than that in DC group; moreover, the inflammatory cells were increased in DC group than DAV group (P<0.05).

Conclusion

This study demonstrated the efficacy of AV for enhanced corneal re-epithelialization, as well as reduced inflammatory response after alkali burn in rats; therefore, it could be useful as a therapy for diabetic keratopathy.

Human Serum Eye Drops in Eye Alterations: An Insight and a Critical Analysis

Human serum contains a physiological plethora of bioactive elements naturally released by activated platelets which might have a significant effect on the regeneration of corneal layers by stimulating the cell growth. This mechanism supported the use of human serum eye drops in some ocular diseases associated with dystrophic changes and alterations of the tear film, such as persistent corneal epithelial defects and dry eye syndrome. We focused our effort on potential benefits and limitations of the use of human serum eye drops when conventional therapies failed. We reviewed the recent literature by reporting published studies from 2010 to 2014. Despite the limited evaluated study populations, most of the clinical studies have confirmed that serum eye drop therapy is effective in corneal healing by reducing ocular symptom, particularly during the short-term follow-up. In addition, three recent published studies have shown the efficacy of the serum eye drop therapy in comparison to traditional ones in intractable patients. Besides, reported ongoing clinical studies confirmed the open debate regarding the use of biologic tools for cornea regeneration. Results from these studies might open novel challenges and perspectives in the therapy of such refractory patients.

Targeting growth factor supply in keratopathy treatment: comparison between maternal peripheral blood and cord blood as sources for the preparation of topical eye drops

BACKGROUND

Epitheliotrophic growth factors (GF) can be supplied topically to patients with severe keratopathy through a variety of blood-derived products. We compared GF content in adult peripheral blood serum (PB-S) and cord blood serum (CB-S) as potential sources of GF. To limit inter-individual variability the assessment was performed in maternal-child pairs at the time of delivery.

MATERIAL AND METHODS

The amounts of epidermal GF (EGF), insulin-like GF (IGF), transforming GF-beta (TGF-β), vascular endothelial GF (VEGF) in CB units collected from the umbilical vein and PB from mothers (each group n=30) were estimated by enzyme-linked immunosorbent assays. Obstetric characteristics and haematological data were recorded from the archives of the Emilia Romagna Cord Blood Bank. Statistical evaluations were performed by Wilcoxon's test and correlations between variables were determined using Spearman's (ρ) coefficient; p-values <0.05 were considered statistically significant.

RESULTS

EGF, TGF-β and VEGF levels were significantly higher in CB-S than in PB-S (median 1,254.4 vs 646.0 pg/mL, 51.3 vs 38.4 μg/mL and 686.8 vs 30 pg/mL, respectively; all p<0.0001) whereas IGF content was significantly higher in PB-S than in CB-S (159.9 vs 53.5 pg/mL, respectively; p<0.0001). In CB-S, the CD34(+) cell concentration appeared to be related to EGF, IGF and TGF-β levels whereas white blood cell count appeared to be related to EGF and TGF-β levels. VEGF levels showed no relation to the haematological parameters considered. Platelet counts were not related to GF level in either CB or PB.

DISCUSSION

The GF content in the two blood sources was different, with CB containing larger amounts. Each GF selectively regulates cellular processes involved in corneal healing, so the use of PB or CB should be targeted to supply specific GF on the basis of the type and severity of the keratopathy.

Sensory nerve regeneration after epithelium wounding in normal and diabetic cornea

The cornea is the most densely innervated mammalian tissue. The sensory nerves are responsible for sensations of dryness, temperature, touch, and pain, and play important roles in the blink reflex, wound healing, and tear production. Many ocular and systemic diseases can adversely affect corneal sensory nerve and consequently impair their function. One of such systemic diseases is diabetes mellitus (DM) which causes sensory degeneration, neurotrophic keratopathy (DNK), and delayed wound healing. In this review, we summarize recent discoveries revealing mechanisms underlying the pathogenesis of DNK and the impairment of sensory nerve regeneration in post wound diabetic corneas in using animal model of human diabetes. Because it is generally believed that common mechanisms are operative in the pathogenesis of diabetic peripheral neuropathy in different tissues, the findings in the corneas have implications in in other tissues such as the skin, which often leads to foot ulceration and amputation in diabetic patients.

Sodium hyaluronate eye drops treatment for superficial corneal abrasion caused by mechanical damage: a randomized clinical trial in the People's Republic of China

PURPOSE

To evaluate the effectiveness and safety of 0.3% sodium hyaluronate (HA) compared to recombinant bovine basic fibroblast growth factor (rb-bFGF) for the treatment of corneal epithelial abrasion caused by mechanical damage in Chinese patients.

METHODS

Thirty patients were randomly assigned to the HA or rb-bFGF treatment group. The HA group was treated with 0.3% HA and 0.5% levofloxacin, and the rb-bFGF group was treated with topical rb-bFGF and 0.5% levofloxacin. The primary endpoint was the clinical effectiveness rates at day 3. Secondary endpoints were the dimensions of the wound area and the percentage of wound closure.

RESULTS

After 3 days of treatment, the clinical effectiveness rates of the HA group and the rb-bFGF group were 86.67% (13/15) and 93.33% (14/15), respectively. The dimensions of the wound area were reduced from 9.83±8.50 to 0.02±0.06 mm(2) for the HA group at day 7, and from 10.58±9.94 to 0.02±0.07 mm(2) for the rb-bFGF group. At day 3, the wound closure was almost complete in both groups; 94.73% in the HA group compared to 95.77% in the rb-bFGF group (P>0.05).

CONCLUSION

Topical 0.3% HA provided a promising treatment for superficial corneal abrasion caused by mechanical damage in a manner similar to rb-bFGF.

[Treating severe keratoconjunctivitis sicca]

Keratoconjunctivitis sicca is a widespread disease with a complex multifactorial pathogenesis. Current understanding of its pathogenesis and existing treatments are summarized in this literature review.

Use of umbilical cord serum in ophthalmology

Among blood preparations, serum has been topically used in the management of various ocular diseases in ophthalmology. Like peripheral blood serum, umbilical cord blood serum contains a high concentration of essential tear components, growth factors, neurotrophic factors, vitamin A, fibronectin, prealbumin, and oil. Umbilical cord serum can provide basic nutrients for epithelial renewal and can facilitate the proliferation, migration, and differentiation of the ocular surface epithelium. Eye drops made from umbilical cord serum have been applied to treat various ocular surface diseases, including severe dry eye with or without Sjögren's syndrome, ocular complications in graft-versus-host disease, persistent epithelial defects, neurotrophic keratopathy, recurrent corneal erosions, ocular chemical burn, and surface problems after corneal refractive surgery. Because mesenchymal stem cells from umbilical cord blood can be used to regenerate corneal tissue and retinal nerve cells, umbilical cord serum might be applied for tissue engineering and regenerative medicine in the future.

Topical 100% serum eye drops for treating corneal epithelial defect after ocular surgery

The purpose of this study was to investigate the efficacy and safety of topical 100% serum eye drops for corneal epithelial defect after ocular surgery. A total of 181 patients who received topical 100% serum therapy for the treatment of corneal epithelial defect following several different types of ocular surgery were recruited into this study. Each patient already failed conventional medical therapy before being prescribed 100% serum eye drops. Slit-lamp biomicroscopic examination with fluorescein staining was performed at baseline and all follow-up visits. The main outcome measures were the rate of complete healing of the corneal epithelial defect and incidence of adverse events. One hundred and seventy-eight eyes (98.34%) received autologous serum eye drops, and 3 (1.66%) received allogeneic serum eye drops. The overall success rate of treating persistent postoperative epithelial defect using 100% serum eye drops was 93.92% (95% CI 0.88-0.98). The median time to complete corneal epithelialization was 4 days (95% CI 4-5). Adverse reactions were observed in 3 patients (1.66%), including sticky sensation with minimal eye discomfort and asymptomatic trace corneal subepithelial infiltration. No serious complications were reported. In conclusion, 100% serum eye drops are effective, safe, and tolerable for treating postoperative corneal epithelial defect following ocular surgeries.

Advanced glycation end products induce human corneal epithelial cells apoptosis through generation of reactive oxygen species and activation of JNK and p38 MAPK pathways

Advanced Glycation End Products (AGEs) has been implicated in the progression of diabetic keratopathy. However, details regarding their function are not well understood. In the present study, we investigated the effects of intracellular reactive oxygen species (ROS) and JNK, p38 MAPK on AGE-modified bovine serum albumin (BSA) induced Human telomerase-immortalized corneal epithelial cells (HUCLs) apoptosis. We found that AGE-BSA induced HUCLs apoptosis and increased Bax protein expression, decreased Bcl-2 protein expression. AGE-BSA also induced the expression of receptor for advanced glycation end product (RAGE). AGE-BSA-RAGE interaction induced intracellular ROS generation through activated NADPH oxidase and increased the phosphorylation of p47phox. AGE-BSA induced HUCLs apoptosis was inhibited by pretreatment with NADPH oxidase inhibitors, ROS quencher N-acetylcysteine (NAC) or neutralizing anti-RAGE antibodies. We also found that AGE-BSA induced JNK and p38 MAPK phosphorylation. JNK and p38 MAPK inhibitor effectively blocked AGE-BSA-induced HUCLs apoptosis. In addition, NAC completely blocked phosphorylation of JNK and p38 MAPK induced by AGE-BSA. Our results indicate that AGE-BSA induced HUCLs apoptosis through generation of intracellular ROS and activation of JNK and p38 MAPK pathways.

Clinical Transplantation of Individualized Recipient Serum-Adapted Cornea Reduces the Risk of Graft Rejection after Keratoplasty

Corneal diseases cause severe visual impairment that necessitates corneal transplantation and frequently repetitive procedures due to graft rejection. We tested the hypothesis that exposure of donor corneas to recipient serum-derived factors during eye banking triggers a preoperative adaptation that is beneficial for postoperative tolerance. Donor corneas were incubated in a medium containing human serum (HS) obtained in each case from the prospective graft recipient in order to individually expose the donor cornea to the recipient's serum. All recipient serum-adapted corneas (RSACs) fulfilled the clinical criteria required by the national law and were transplanted successfully. The postoperative ophthalmological examination extended up to 8 years. All RSACs were tolerated by their recipients and did not cause postoperative complications and no rejection. Proteomic analysis of corneas cultivated in culture medium containing either fetal calf serum (FCS) that is routinely used for cornea banking or HS revealed different patterns of proteins. HS-cultured corneas showed a greater proteomic similarity with native human corneas than did the FCS-cultured corneas, indicating a differential nutrification of the cultured corneal tissue by HS-derived factors. The clinical results show for the first time that postoperative complications such as tissue intolerance and graft rejection might be managed if the corneal tissue is individually adapted to the recipient's serum trophic factors. This new donor tissue treatment procedure offers incontrovertible advantages and could be adapted for low-risk eyes as well as other transplantable tissues.

Corneal complications in streptozocin-induced type I diabetic rats

PURPOSE. This study seeks to characterize corneal functions and complications in a streptozocin (STZ)-induced rat model of type I diabetes mellitus (DM) and to understand the pathogenesis of diabetic keratopathy. METHODS. DM was induced via STZ injection in Sprague-Dawley rats. Body weight, length, and corneal size were measured and compared with the age-matched normal controls. Corneal morphology and histology were evaluated with slit lamp, digital confocal microscopy and hematoxylin and eosin staining. Tear secretion was measured with cotton threads, and corneal sensitivity was determined with an esthesiometer. Protein expression and distribution were assessed with Western blotting and immunohistochemistry. Wound healing was determined using an in vivo corneal epithelial debridement model. RESULTS. Compared with the normal control rats, STZ rats had reduced body weight, and body length, but minimally affected corneal size. No significant changes in ocular surface regularity, corneal thickness, and morphology were noted in diabetic corneas. STZ rats showed stronger Rose Bengal staining, decreased tear secretion, slightly attenuated sensitivity, less innervation, delayed epithelial wound healing, and impaired epidermal growth factor receptor signaling in their corneas. While the expression of adherens junction protein β-catenin, and tight junction proteins occludin and ZO-1 was unchanged, the formation of these junctions after wound closure was delayed. CONCLUSIONS. Pathogenesis of diabetic keratopathy involves multiple tissues and/or cell types and several events including reduced tear secretion, impaired innervation, weakened cell junction, and altered wound responses. These insights may prove useful for the clinical translation of evolving strategies for the management and treatment of diabetic corneal complications.

Low-cost protocol for the production of autologous serum eye drops by blood collection and processing centres for the treatment of ocular surface diseases

OBJECTIVES

To create a low-cost protocol for the production of autologous serum eye drops (ASEs) by blood collection and processing centres using standard equipment and staff already available. The protocol must observe local and federal regulatory authorities' requirements for good manufacturing practice.

AIM

The final aim is to improve accessibility to ASEs for patients who need them and to implement similar production parameters at all institutions producing ASEs.

BACKGROUND

Despite evidence of the beneficial effects of ASEs in the treatment of severe ocular surface diseases, ASEs are not approved by most federal regulatory bodies in the United States or Europe. In some countries, such as the United States, access to ASEs is extremely limited and cost-prohibitive. Blood processing centres are in optimal position to help in increasing accessibility and lowering the cost of these products.

MATERIALS/METHODS

Standard blood processing equipment, staff and materials were chosen for the protocol. The protocol was designed to minimise the risk of contamination as much as possible.

RESULTS

A low-cost, open system protocol for production of ASEs was generated that can be implemented by most blood collection and processing centres in the United States and Europe.

CONCLUSION

Efforts should be made to propagate a similar protocol for the production of ASEs in blood centres capable of collecting and processing blood products, making this service affordable and uniformly accessible to patients.

Impaired epithelial wound healing and EGFR signaling pathways in the corneas of diabetic rats

PURPOSE. The purpose of the study was to investigate the effects of hyperglycemia on EGFR (epidermal growth factor receptor)-mediated wound response and signal transduction in the corneal epithelium of rats with type I diabetes mellitus (DM). METHODS. Corneal epithelia were removed from streptozotocin (STZ)- and weight-matched normal rats. Wound healing was monitored by fluorescein staining at 24 or 48 hours after epithelial debridement. Phosphorylation of EGFR, AKT, ERK, and BAD was determined by Western blot analysis. The distribution of phospho-AKT and proliferating cell nuclear antigen (PCNA) in rat corneas was examined by immunohistochemistry. Cell death was evaluated by TUNEL staining. RESULTS. A significant delay in corneal epithelial wound healing was observed 48 hours after wounding in the diabetic rats compared with the weight-matched control rats. In the DM rat corneas, epithelial cells demonstrated diminished responses to wounding, as assessed by the phosphorylation of EGFR and its downstream signaling molecules, AKT and ERK. Furthermore, although the distribution pattern of phospho-AKT suggested a role for AKT in epithelial migration and proliferation in the normoglycemic rat corneas, it was abrogated in the healing epithelia of the DM rats. Consistent with impaired AKT activity, the number of PCNA-stained cells was also greatly reduced in the healing corneas of the diabetic rats. Finally, decreases in pBAD (Ser(136) and Ser(112)) and increases in TUNEL-positive cells were observed in both the uninjured and healing corneal epithelia of the DM rats, but not of the control rats. CONCLUSIONS. In the corneas of SZT rats, EGFR-PI3K-AKT and ERK, as well as their downstream BAD signaling pathways in migratory epithelium, were altered, resulting in increased apoptosis, decreased cell proliferation, and delayed wound closure.

New therapeutic approaches in the treatment of diabetic keratopathy: a review

The cornea is densely innervated, and the integrity of these nerve fibres is critical in maintaining the refractive and protective functions of the cornea. Many ocular and systemic diseases can adversely affect corneal sensory nerves and consequently impair their function, with vision loss being the inevitable consequence of severe corneal neurotrophic ulceration. However, current standard treatments regimens are often ineffective. Over the past three decades, the role of growth factors in maintaining the normal structure and function of the cornea, and in corneal epithelial healing, has become increasingly evident. Many preclinical and clinical trials have shown that growth factors and cytokines can significantly enhance epithelialization (epithelial proliferation and migration) and consequently accelerate wound healing. More recently, local/topical administration of insulin, naltrexone (opioid antagonist) and nicergoline (ergoline derivatives) were found to improve, and significantly increase, the corneal wound healing rate. This report reviews the major attributes of these growth factors and therapeutic agents that may be used in ameliorating impaired corneal wound healing, and presents a perspective on the potential clinical use of these agents as a new generation of ophthalmic pharmaceuticals for the treatment of diabetic keratopathy.

The effect of topical autologous serum on graft re-epithelialization after penetrating keratoplasty

PURPOSE

To analyze factors influencing corneal graft re-epithelialization after penetrating keratoplasty (PK) and evaluate the effect of topical autologous serum in promoting graft re-epithelialization.

DESIGN

Prospective interventional study.

METHODS

We analyzed 165 eyes of 165 patients who underwent PK between January 1, 2005 and December 31, 2007. Patients were divided into 2 groups according to routine use or non-use of postoperative 20% topical autologous serum. Postoperative slit-lamp examination after fluorescein staining was performed, and graft re-epithelialization time was recorded. Recipient/donor characteristics, surgical variables, and topical use of autologous serum were analyzed for their effects on post-PK graft re-epithelialization. Statistical analysis was performed by univariate and multivariate regression analysis using the ordinal logistic fit model to assess the potential risk factors influencing graft re-epithelialization after PK.

RESULTS

In univariate analysis, diabetes mellitus (DM), longer death-to-storage time and death-to-surgery time of the donor, and larger recipient size significantly delayed graft re-epithelialization (P < .05). Use of autologous serum significantly expedited graft re-epithelialization (P = .004). In multiple regression analysis, only DM in the recipient (odds ratio [OR] = 5.10, P < .001), postoperative use of autologous serum (OR = 0.54, P = .046), and larger graft size (OR = 4.44, P < .001) influenced graft re-epithelialization. The beneficial and healing effect of autologous serum is particularly significant in diabetic recipients and larger grafts.

CONCLUSIONS

Several factors may influence graft re-epithelialization after PK. Graft re-epithelialization time was longer in diabetic recipients and larger grafts. Use of autologous serum may be a beneficial strategy in these patients with potentially delayed epithelial healing.