The role of ultraviolet radiation in the pathogenesis of pterygia (Review)

A Phase IIa Multicenter, Randomized, Vehicle-Controlled, Dose Escalating Study to Evaluate the Safety, Efficacy, and Pharmacokinetics of CBT-001 Ophthalmic Solution in Patients With Primary or Recurrent Pterygium

Purpose

To evaluate the safety and efficacy of CBT-001, a multitarget tyrosine kinase inhibitor eyedrop, for pterygia.

Design

Phase II clinical trial. Stage 1 was a single center, open-labeled, vehicle-controlled study. Stage 2 was a multicenter, randomized, double-masked, vehicle-controlled trial.

Participants

Patients with primary or recurrent pterygia.

Main Outcome Measures

The primary efficacy end point was lesion vascularity based on masked grading of photographs by an independent reading center. Other end points included dimensions of pterygia and safety.

Methods

In stage 1, 24 eyes of 24 patients received 1 drop of CBT-001 in a dose escalation fashion (0.02%, 0.05%, and 0.2%) to determine the maximally tolerated dose based on adverse events (AEs) and blood drug levels. In stage 2, subjects were randomly assigned to receive the maximally tolerated dose of CBT-001 or vehicle dosed 3 times a day for 4 weeks with a 20-week follow-up.

Results

In stage 1, the plasma maximum concentration values for all doses of CBT-001 were at or below the limit of detection (0.01 ng/ml). The most commonly reported AEs were mild foreign body sensation and irritation. CBT-001 0.2% was evaluated in stage 2. Baseline demographic characteristics were similar between patients receiving CBT-001 (n = 25) and vehicle (n = 23). After 4 weeks of dosing, the mean change from baseline in pterygium vascularity scores was -0.8 ± 0.7 (mean ± standard deviation) in subjects receiving CBT-001 0.2% and 0.0 ± 0.5 in subjects receiving vehicle (P < 0.001; 95% confidence interval: -1.12, -0.40). Pterygium vascularity scores remained significantly decreased, after the 4-week dosing period, at weeks 8 and 16, but not at week 24. The mean changes from baseline in the length of the pterygia were also significantly lower in subjects receiving CBT-001 compared with vehicle at weeks 2, 4, and 8 (P ≤ 0.014). The most commonly reported AEs were ocular, mild in severity, resolved after therapy, and did not result in discontinuation.

Conclusions

CBT-001 0.2% decreased pterygia vascularity and lesion length after 4 weeks of dosing with a prolonged effect after dosing. The drug was well tolerated with minimal detected systemic drug levels.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Risk factors for pterygium: Latest research progress on major pathogenesis

A pterygium is a wedge-shaped fibrovascular growth of the conjunctiva membrane that extends onto the cornea, which is the outer layer of the eye. It is also known as surfer's eye. Growth of a pterygium can also occur on the either side of the eye, attaching firmly to the sclera. Pterygia are one of the world's most common ocular diseases. However, the pathogenesis remains unsolved to date. As the pathogenesis of pterygium is closely related to finding the ideal treatment, a clear understanding of the pathogenesis will lead to better treatment and lower the recurrence rate, which is notably high and more difficult to treat than a primary pterygium. Massive studies have recently been conducted to determine the exact causes and mechanism of pterygia. We evaluated the pathogenetic factors ultraviolet radiation, viral infection, tumor suppressor genes p53, growth factors, oxidative stress, apoptosis and neuropeptides in the progression of the disease. The heightened expression of TRPV1 suggests its potential contribution in the occurrence of pterygium, promoting its inflammation and modulating sensory responses in ocular tissues. Subsequently, the developmental mechanism of pterygium, along with its correlation with dry eye disease is proposed to facilitate the identification of pathogenetic factors for pterygia, contributing to the advancement of understanding in this area and may lead to improved surgical outcomes.

Study of biomarkers p53, Ki-67, Bcl-2, and VEGF in pterygium

PURPOSE

To study the biomarkers present in primary pterygium samples of patients of Indian ethnicity and compare it with the samples obtained from the unaffected conjunctiva of the same eye.

METHODS

A prospective case-control study of 17 eyes in patients above 10 years of age with primary pterygium who underwent pterygium excision using limbal conjunctival autograft technique. The pterygium samples (cases) and conjunctival samples (controls) were sent for immunohistochemical (IHC) staining for the following biomarkers: p53, Bcl-2, Ki-67, and vascular endothelial growth factor (VEGF).

RESULT

The immunohistochemistry of the samples and the controls revealed p53 positivity in 47.05% of pterygium samples and 29.4% of controls ( P < 0.587). Nine cases each in pterygium and control samples were positive for Ki-67 expression. Differences in the staining pattern between the two groups were not statistically significant ( P < 1.000). Bcl-2 positivity was seen in 10 pterygium samples (58.8%) and 12 controls (70.5%), with no statistical difference between the two groups ( P < 0.455). VEGF expression was seen in both epithelial and endothelial cells of the samples and controls, with no statistical difference between the two groups, with P = 1.000 for the epithelial staining and P = 0.637 for endothelial staining.

CONCLUSION

The expression of biomarkers was comparable in both groups. We conclude that pterygium, against common belief, might not be a localized disease process but a global ocular phenomenon where the apparently healthy tissue also has some ongoing disease process at a molecular level.

Current insights and future perspectives of ultraviolet radiation (UV) exposure: Friends and foes to the skin and beyond the skin

Ultraviolet (UV) radiation is ubiquitous in the environment, which has been classified as an established human carcinogen. As the largest and outermost organ of the body, direct exposure of skin to sunlight or UV radiation can result in sunburn, inflammation, photo-immunosuppression, photoaging and even skin cancers. To date, there are tactics to protect the skin by preventing UV radiation and reducing the amount of UV radiation to the skin. Nevertheless, deciphering the essential regulatory mechanisms may pave the way for therapeutic interventions against UV-induced skin disorders. Additionally, UV light is considered beneficial for specific skin-related conditions in medical UV therapy. Recent evidence indicates that the biological effects of UV exposure extend beyond the skin and include the treatment of inflammatory diseases, solid tumors and certain abnormal behaviors. This review mainly focuses on the effects of UV on the skin. Moreover, novel findings of the biological effects of UV in other organs and systems are also summarized. Nevertheless, the mechanisms through which UV affects the human organism remain to be fully elucidated to achieve a more comprehensive understanding of its biological effects.

TFOS Lifestyle Report: Impact of environmental conditions on the ocular surface

Environmental risk factors that have an impact on the ocular surface were reviewed and associations with age and sex, race/ethnicity, geographical area, seasonality, prevalence and possible interactions between risk factors are reviewed. Environmental factors can be (a) climate-related: temperature, humidity, wind speed, altitude, dew point, ultraviolet light, and allergen or (b) outdoor and indoor pollution: gases, particulate matter, and other sources of airborne pollutants. Temperature affects ocular surface homeostasis directly and indirectly, precipitating ocular surface diseases and/or symptoms, including trachoma. Humidity is negatively associated with dry eye disease. There is little data on wind speed and dewpoint. High altitude and ultraviolet light exposure are associated with pterygium, ocular surface degenerations and neoplastic disease. Pollution is associated with dry eye disease and conjunctivitis. Primary Sjögren syndrome is associated with exposure to chemical solvents. Living within a potential zone of active volcanic eruption is associated with eye irritation. Indoor pollution, "sick" building or house can also be associated with eye irritation. Most ocular surface conditions are multifactorial, and several environmental factors may contribute to specific diseases. A systematic review was conducted to answer the following research question: "What are the associations between outdoor environment pollution and signs or symptoms of dry eye disease in humans?" Dry eye disease is associated with air pollution (from NO2) and soil pollution (from chromium), but not from air pollution from CO or PM10. Future research should adequately account for confounders, follow up over time, and report results separately for ocular surface findings, including signs and symptoms.

Toxic External Exposure Leading to Ocular Surface Injury

The surface of the eye is directly exposed to the external environment, protected only by a thin tear film, and may therefore be damaged by contact with ambient particulate matter, liquids, aerosols, or vapors. In the workplace or home, the eye is subject to accidental or incidental exposure to cleaning products and pesticides. Organic matter may enter the eye and cause infection. Ocular surface damage can trigger a range of symptoms such as itch, discharge, hyperemia, photophobia, blurred vision, and foreign body sensation. Toxin exposure can be assessed clinically in multiple ways, including via measurement of tear production, slit-lamp examination, corneal staining, and conjunctival staining. At the cellular level, environmental toxins can cause oxidative damage, apoptosis of corneal and conjunctival cells, cell senescence, and impaired motility. Outcomes range from transient and reversible with complete healing to severe and sight-compromising structural changes. Classically, evaluation of tolerance and safety was carried out using live animal testing; however, new in vitro and computer-based, in silico modes are superseding the gold standard Draize test. This review examines how environmental features such as pollutants, temperature, and seasonality affect the ocular surface. Chemical burns to the eye are considered, and approaches to protect the ocular surface are detailed.

Prevalence and associated factors for pterygium in a Chinese rural population with type 2 diabetes in a cross-sectional study: Jiangsu Diabetic Eye Disease Study (JDEDS)

PURPOSE

To investigate the pterygium prevalence and evaluate risk factors of pterygium in rural type 2 diabetic (D2M) patients aged 50 years and above in Funing Country, Jiangsu Province, China.

METHODS

A cross-sectional ophthalmic survey was conducted in type 2 diabetes mellitus (D2M) patients aged ≥ 50 years in Funing County, Jiangsu Province, China, which was named Jiangsu Diabetic Eye Disease Study (JDEDS). All participants underwent a comprehensive questionnaire and ocular examination. Pterygium was diagnosed by slit lamp examination. The risk factors associated with pterygium were evaluated with logistic regression models.

RESULTS

The prevalence of pterygium was 22.37% (n = 427) and 95% confidence interval (CI) (20.50-24.24%) in D2M patients aged 50 years and above in JDEDS. The prevalence of pterygium was 18.32% (95% CI 15.33-21.32%) in men and 24.43% (95% CI 22.06-26.80%) in women. Women had a higher prevalence than men (p = 0.001). Multivariate analysis showed, for male participants with D2M, pterygium was independently associated with increasing age [70-79 years: OR and 95% CI 2.49(1.20-5.18), p = 0.014; ≥ 80 years: 4.84(2.04-11.47), p < 0.001], while cigarette smoking was the protective factors, especially in current smoker [OR and 95% CI 0.79(0.67-0.92); p = 0.003]. For female participants with D2M, age [60-69 years OR and 95% CI 1.68(1.07-2.62), p = 0.023; 70-79 years: 2.62(1.69-4.06), p < 0.001; ≥ 80 years:3.24(1.70-5.90), p < 0.001], hypertension [OR and 95% CI 1.40(1.05-1.87), p = 0.024], BMI 24-27.9 [OR and 95% CI 1.20(1.00-1.44), p = 0.047], higher HbA1c [(5.6-7.9) % OR and 95% CI 1.42(1.10-1.82), p = 0.006; (8.0-9.9) %: 1.32(1.10-1.58), p = 0.003] were risk factors.

CONCLUSIONS

D2M patients aged over 50 years has a high prevalence of pterygium in JDEDS. The pterygium prevalence is higher in female D2M participants. Diabetes and related factors may be risk factors of pterygium in female D2M patients. Further studies are needed to explore the gender difference in the pathogenesis of pterygium in D2M subjects.

Symblepharon in kittens: a retrospective study of 40 kittens and 54 eyes (2002-2022)

OBJECTIVES

The aim of this study was to retrospectively evaluate the signalment, treatment, surgical technique and outcomes for feline symblepharon.

METHODS

A retrospective medical record review and standardized grading of clinical descriptions and photographs was undertaken.

RESULTS

Forty kittens (54 eyes) aged 3-46 weeks had symblepharon of five types in various combinations: eyelid deformation (24 kittens; 32 eyes); ankyloblepharon (four kittens; four eyes); conjunctiva-to-conjunctiva (11 kittens; 12 eyes); third eyelid-to-conjunctiva (24 kittens; 29 eyes); and corneoconjunctival adhesions (14 kittens; 16 eyes). At initial presentation, 23 (43%) eyes were affected by one type of symblepharon, 25 (46%) eyes by two types and six (11%) eyes by three types; 11 (20%) corneas were ulcerated. Twenty-four (44%) eyes of 18 (45%) kittens were managed medically. Surgery was performed under general anesthesia/sedation (30 occasions) or topical anesthesia (21 occasions) on 30 (56%) eyes of 22 kittens; 12 eyes (40%) underwent multiple surgeries. Four techniques were commonly employed: separation of conjunctival-to-conjunctival adhesions ± eyelid margins (14 eyes); resection of third eyelid adhesions ± temporary tacking of the third eyelid (modified Arlt's pterygium technique; 18 eyes); en bloc resection of the third eyelid (two eyes); and separation of corneoconjunctival adhesions (14 eyes). Median duration of follow-up was 55 days (range 1-1051). Median symblepharon grade in kittens treated surgically improved for all types except corneoconjunctival symblepharon. Median symblepharon grade in kittens receiving medical management remained the same or improved. Corneoconjunctival symblepharon opacity decreased for eyes treated surgically but increased for eyes treated medically. Three eyes were enucleated due to complications of corneoconjunctival symblepharon. At final presentation, symblepharon persisted in 46 (85%) eyes; however, menace response was evident in 13/16 eyes and dazzle reflex in 23/23 eyes.

CONCLUSIONS AND RELEVANCE

Symblepharon is a heterogeneous group of conditions with diverse anatomic involvement, clinical appearance and impact, optimal treatment and prognosis for vision.

Pharmacological treatment strategies of pterygium: Drugs, biologics, and novel natural products

Pterygium is a fibrovascular tissue growth invading the cornea. Adjunctive treatment post-surgery includes conventional immunosuppressants as well as antiviral drugs. The use of large- and small-molecule antivascular endothelial growth factor (VEGF) agents remains an integral part of pterygium treatment as well as other neovascular conditions of the eye. Naturally occurring polyphenolic compounds have favorable characteristics for treating neovascular and inflammatory eye conditions, including good efficacy, stability, cost-effectiveness, and the versatility of their chemical synthesis. In this review, we discuss pharmacological treatments of pterygium. Natural products, such curcumin, ellagic acid, and chalcones, are reviewed, with emphasis on their potential as future pterygium treatments.

Safety Evaluation of Far-UV-C Irradiation to Epithelial Basal Cells in the Corneal Limbus

Basal cells in the corneal limbus play an important role in the turnover cycle because they are the source of all cells that constitute the corneal epithelium. We examined the penetration depth of ultraviolet (UV) light in the corneal limbus and assessed the safety of Far-UV-C on stem cells in the basal area of the corneal limbus. Rats were irradiated with UV at peaks of 207, 222, 235, 254 and 311 nm while under anesthesia. The UV penetration depth in the rat corneal limbal epithelium was wavelength dependent: 311 nm UV-B and 254 nm UV-C reached the basal cells of the epithelium, and 235 nm radiation reached the middle area; however, 207 and 222 nm UV-C reached only the superficial layer of the epithelium. Porcine cornea, which is similar to the human eye in size and structure, were irradiated with 222 and 254 nm UV-C. As in rats, 222 nm UV-C reached only the superficial layer of the porcine corneal limbal epithelium. These results indicate that Far-UV-C, such as radiation of wavelengths of 207 and 222 nm, could not reach corneal epithelial stem cells, i.e. the cells remained intact. It is unlikely that the turnover of the corneal epithelium is obstructed or disrupted by exposure to Far-UV-C.

Pterygium Screening and Lesion Area Segmentation Based on Deep Learning

A two-category model and a segmentation model of pterygium were proposed to assist ophthalmologists in establishing the diagnosis of ophthalmic diseases. A total of 367 normal anterior segment images and 367 pterygium anterior segment images were collected at the Affiliated Eye Hospital of Nanjing Medical University. AlexNet, VGG16, ResNet18, and ResNet50 models were used to train the two-category pterygium models. A total of 150 normal and 150 pterygium anterior segment images were used to test the models, and the results were compared. The main evaluation indicators, including sensitivity, specificity, area under the curve, kappa value, and receiver operator characteristic curves of the four models, were compared. Simultaneously, 367 pterygium anterior segment images were used to train two improved pterygium segmentation models based on PSPNet. A total of 150 pterygium images were used to test the models, and the results were compared with those of the other four segmentation models. The main evaluation indicators included mean intersection over union (MIOU), IOU, mean average precision (MPA), and PA. Among the two-category models of pterygium, the best diagnostic result was obtained using the VGG16 model. The diagnostic accuracy, kappa value, diagnostic sensitivity of pterygium, diagnostic specificity of pterygium, and F1-score were 99%, 98%, 98.67%, 99.33%, and 99%, respectively. Among the pterygium segmentation models, the double phase-fusion PSPNet model had the best results, with MIOU, IOU, MPA, and PA of 86.57%, 78.1%, 92.3%, and 86.96%, respectively. This study designed a pterygium two-category model and a pterygium segmentation model for the images of the normal anterior and pterygium anterior segments, which could help patients self-screen easily and assist ophthalmologists in establishing the diagnosis of ophthalmic diseases and marking the actual scope of surgery.

Evaluation of the Effects of Pterygium and Aging on Limbal Structure Using Optical Coherence Tomography

Previous studies suggest that regions of corneal limbus may possess structural differences. We aimed to investigate the limbal changes associated with pterygium and aging via optical coherence tomography (OCT). Palisades of Vogt epithelial thickness (POV-ET) and Bowman’s membrane epithelial thickness (BM-ET) were measured at the nasal, temporal, superior, and inferior quadrants of patients with pterygium and healthy subjects of different ages. Values were expressed as a ratio that functioned as an index used to evaluate the change of limbus. Ratio values determined for quadrants of the corneal limbus were correlated highly in young healthy subjects. Further, parameter values were significantly greater than those of elder healthy subjects. In young subjects, the temporal and superior quadrants of patients with pterygium were significantly lower than those of healthy subjects. Temporal and superior quadrants of elder pterygium patients affected by both pterygium and age were significantly lower than those of healthy subjects; however, the inferior quadrant of elderly pterygium patients was significantly higher than that of age-matched healthy subjects. Our findings revealed that the thickness of limbal epithelium was negatively correlated with age, while pterygium led to the thinning of the temporal and superior limbal epithelium and inferior limbal epithelial thickening.

The role of cyclophilin A and VEGF in the pathogenesis and recurrence of pterygium

PURPOSE

Pterygium is defined as overgrowth of abnormal conjunctival tissue on the cornea. Many proinflammatory cytokines and various growth factors have been implicated in the pathogenesis of pterygium. Cyclophilin A (CyPA) is a protein that is used by cyclosporin A (CsA) as the intracellular receptor and is secreted in response to inflammatory stimuli. Vascular endothelial growth factor (VEGF) is the most important angiogenic factor. This study aimed to assessment CyPA and VEGF immunoreactivity in pterygium specimens.

MATERIAL AND METHODS

In this cross-sectional study, 32 primary pterygium samples, 25 recurrent pterygium samples and 25 normal bulbar conjunctiva samples were included. The histopathological features, CyPA and VEGF immunoreactivity of surgically excised pterygium specimens were compared with control conjunctiva specimens obtained from normal bulbar conjunctiva.

RESULTS

CyPA immunoreactivity in vascular endothelial cells, epithelial cells, and stromal cells was remarkably higher in pterygium specimens than control conjunctiva specimens (p = 0.004, p = 0.012, p = 0.001, respectively). Morever, VEGF immunoreactivity in endothelial cells was remarkably higher in pterygium specimens than control conjunctiva specimens (p < 0.001). When recurrent and primary pterygium specimens were compared, CyPA and VEGF immunoreactivity was remarkably higher in recurrent pterygium (p = 0.001, p = 0.001, respectively). Pearson correlation showed that CyPA immunoreactivity correlated with stromal vascularity, stromal inflammation, and mast cell count in pterygium specimens.

CONCLUSION

This study aimed to assess CyPA and VEGF may have a important function in the pathogenesis and recurrence of pterygium.

One-Year Ocular Safety Observation of Workers and Estimations of Microorganism Inactivation Efficacy in the Room Irradiated with 222-Nm far Ultraviolet-C Lamps

Two krypton-chloride germicidal excimer lamp units (Care222 TRT-104C11-UI-U3, USHIO Inc.) were installed in the examination room of an ophthalmology department. The irradiation dose was set not to exceed the former (i.e., before 2022) threshold limit value (TLV) (22 mJ/cm² /8 hours) recommended by the ACGIH. Section 1: The eyes and lids of the 6 ophthalmologists (5 wore glasses for myopic correction) who worked in the room for a mean stay of 6.7 hours/week were prospectively observed for 12 months. Slitlamp examinations revealed neither acute adverse events such as corneal erosion, conjunctival hyperemia, lid skin erythema nor chronic adverse events such as pterygium, cataract, or lid tumor. The visual acuity, refractive error, corneal endothelial cell density remained unchanged during the study. Section 2: The irradiation of samples placed on the table or floor using the same fixtures in the room (5-7.5 mJ/cm² ) was associated with >99% inhibition of φX174 phage and >90% inhibition of S. aureus. In conclusion, no acute or chronic health effects in human participants was observed in a clinical setting of full-room ultraviolet germicidal irradiation by 222-nm lamp units and high efficacy in deactivation of microorganisms was determined in the same setting.

Dendrobium nobile protects retinal cells from UV-induced oxidative stress damage via Nrf2/HO-1 and MAPK pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Excessive UV irradiation and ROS exposure are the main contributors of ocular pathologies. Pseudobulb of Dendrobium nobile Lindl. is one of the sources of Shihu and has long been used in traditional Chinese medicine as a tonic to nourish stomach, replenish body fluid, antipyretic and anti-inflammation.

AIM OF STUDY

This study aimed to investigate whether D. nobile could protect ocular cells against oxidative stress damage.

MATERIALS AND METHODS

Retinal-related cell lines, ARPE-19 and RGC-5 cells, were pretreated with D. nobile extracts before H₂O₂- and UV-treatment. Cell viability and the oxidative stress were monitored by sulforhodamine B (SRB) and SOD1 and CAT assay kits, respectively. The oxidative stress related proteins were measured by Western blotting.

RESULTS

Under activity-guided fractionation, a sesquiterpene-enriched fraction (DN-2) and a major component (1) could ameliorate H₂O₂- and UV-induced cytotoxicity and SOD1 and CAT activity, but not dendrobine, the chemical marker of D. nobile. Western blotting showed both DN-2 and compound 1 protected ARPE-19 cells against UV-induced oxidative stress damage by regulating MAPK and Nrf2/HO-1 signaling.

CONCLUSION

Our results suggest D. nobile extract protects retinal pigment epithelia cells from UV- and oxidative stress-damage, which may have a beneficial effect on eye diseases.

Expression profiling suggests the involvement of hormone-related, metabolic, and Wnt signaling pathways in pterygium progression

BACKGROUND

Pterygium is an ocular surface disease that can cause visual impairment if it progressively invades the cornea. Although many pieces of research showed ultraviolet radiation is a trigger of pterygium pathological progress, the underlying mechanism in pterygium remains indistinct.

METHODS

In this study, we used microarray to evaluate the changes of transcripts between primary pterygium and adjacent normal conjunctiva samples in China. Then, we performed Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analyses. Moreover, we constructed protein-protein interaction (PPI) and miRNA-mRNA regulatory networks to predict possible regulatory relationships. We next performed gene set enrichment analysis (GSEA) to explore the similarities and differences of transcripts between Asian studies from the Gene Expression Omnibus database. Furthermore, we took the intersection of differentially expressed genes (DEGs) with other data and identified hub genes of the development of pterygium. Finally, we utilized real-time quantitative PCR to verify the expression levels of candidate genes.

RESULTS

A total of 49 DEGs were identified. The enrichment analyses of DEGs showed that pathways such as the Wnt-signaling pathway and metabolism-related pathways were upregulated, while pathways such as hormone-related and transcription factor-associated pathways were downregulated. The PPI and miRNA-mRNA regulatory networks provide ideas for future research directions. The GSEA of selecting Asian data revealed that epithelial-mesenchymal transition and myogenesis existed in the pathology of pterygium in the Asian group. Furthermore, five gene sets (interferon-gamma response, Wnt beta-catenin signaling, oxidative phosphorylation, DNA repair, and MYC targets v2) were found only in our Chinese datasets. After taking an intersection between selecting datasets, we identified two upregulated (SPP1 and MYH11) and five downregulated (ATF3, FOS, EGR1, FOSB, and NR4A2) hub genes. We finally chose night genes to verify their expression levels, including the other two genes (SFRP2 and SFRP4) involved in Wnt signaling; Their expression levels were significantly different between pterygium and conjunctiva.

CONCLUSIONS

We consider hormone-related, metabolic, and Wnt signaling pathways may be important in the pathology of pterygium development. Nine candidate genes we identified deserve further study and can be potential therapeutic targets.

SPARC knockdown attenuated TGF-β1-induced fibrotic effects through Smad2/3 pathways in human pterygium fibroblasts

PURPOSE

Secreted protein acidic and rich in cysteine (SPARC), a matricellular glycoprotein, has been found to regulate processes involved in fibrotic diseases. The aim of this study was to investigate the anti-fibrotic effects of SPARC in primary human pterygium fibroblasts (HPFs) and elucidate the underlying mechanisms.

METHODS

The expression of SPARC in HPFs was knocked down by RNA interference-based approach. Subsequently, we examined the expression of profibrotic markers induced by transforming growth factor-β1 (TGF-β1), including type 1 collagen (COL1), α-smooth muscle actin (α-SMA), and fibronectin (FN). The changes in signaling pathways and matrix metalloproteinases (MMPs) were also detected by western blotting. The cellular migration ability, proliferation ability, apoptosis, and contractile phenotype were detected using the wound healing assay, Cell Counting Kit-8 assay, flow cytometry, and collagen gel contraction assay, respectively. The interaction between SPARC and TGF-β RII was detected by Co-IP RESULTS: Silencing of SPARC inhibited the basal and TGF-β1-induced expression of COL1, α-SMA, and FN in HPFs, and suppressed the expression of p-Smad2, p-Smad3, Smad4 and MMP2, MMP9. The downregulation of SPARC also attenuated the cell migration and contractile phenotype of HPFs. SPARC could bind to TGF-βRII under TGF-β1 treatment. However, knockdown of SPARC did not affect the proliferation and apoptosis of HPFs.

CONCLUSION

SPARC knockdown attenuated the fibrotic effect induced by TGF-β1 at least in part by inactivating the Smad2/3 pathways in HPFs. Therefore, SPARC may be a promising therapeutic target for the treatment of pterygium.

Transcriptome Analysis of Pterygium and Pinguecula Reveals Evidence of Genomic Instability Associated with Chronic Inflammation

Solar damage due to ultraviolet radiation (UVR) is implicated in the development of two proliferative lesions of the ocular surface: pterygium and pinguecula. Pterygium and pinguecula specimens were collected, along with adjacent healthy conjunctiva specimens. RNA was extracted and sequenced. Pairwise comparisons were made of differentially expressed genes (DEGs). Computational methods were used for analysis. Transcripts from 18,630 genes were identified. Comparison of two subgroups of pterygium specimens uncovered evidence of genomic instability associated with inflammation and the immune response; these changes were also observed in pinguecula, but to a lesser extent. Among the top DEGs were four genes encoding tumor suppressors that were downregulated in pterygium: C10orf90, RARRES1, DMBT1 and SCGB3A1; C10orf90 and RARRES1 were also downregulated in pinguecula. Ingenuity Pathway Analysis overwhelmingly linked DEGs to cancer for both lesions; however, both lesions are clearly still benign, as evidenced by the expression of other genes indicating their well-differentiated and non-invasive character. Pathways for epithelial cell proliferation were identified that distinguish the two lesions, as well as genes encoding specific pathway components. Upregulated DEGs common to both lesions, including KRT9 and TRPV3, provide a further insight into pathophysiology. Our findings suggest that pterygium and pinguecula, while benign lesions, are both on the pathological pathway towards neoplastic transformation.

Association between HPV detection in swab samples and tissue specimens and ophthalmic pterygium recurrence

PURPOSE

To investigate the presence of HPV on the ocular surface after surgical excision of HPV infected pterygia and the possible correlation of HPV with pterygium postoperative recurrence.

MATERIALS AND METHODS

Both exfoliative pterygium swab samples and respective tissue specimens were received and analyzed with real-time PCR for the detection of HPV-infected pterygia. In addition, swab samples from patients that had HPV-infected pterygia with no recurrence after 1 year of follow-up, as well as swab samples from patients with healthy conjunctiva, were analyzed.

RESULTS

Forty eyes with pterygium of 40 patients and 40 eyes with normal conjunctiva were included in the study. HPV virus was detected in the tissue specimens of 11 patients (27.5%) and in the swabs of 9 patients (22.5%). The HPV subtypes detected were 33, 39, 45, 56, 59, 66, and 68. The swab test had sensitivity of 81.82% and 100% specificity. In 15 (43%) patients, a bare sclera technique was used for pterygium removal and eleven of these patients showed recurrence of the disease. Surgical excision with use of autologous conjunctival graft was performed in twenty patients and five of them had recurrence. Patients with recurrent disease were 12.41 times more likely to have an HPV-infected pterygium (p = 0.031). Furthermore, from the 11 HPV positive patients, six had no recurrence, 1 year after surgery. In five of them, a swab sample was taken from the site of the surgical excision 1 year after surgery and real-time PCR was negative for HPV presence.

CONCLUSION

Persistence of HPV infection seems to be correlated with postoperative pterygium recurrence. Further investigation with the use of the minimally invasive proposed swab technique may contribute in the understanding of pterygium pathogenesis and in the development of a more efficient treatment planning.

Conjunctival Expression of Toll-Like Receptor 3 Plays a Pathogenic Role in the Formation of Ultraviolet Light-Induced Pterygium

Purpose

Toll-like receptor 3 (TLR3), as a damage-associated molecular pattern sensor, can detect self-RNA released from necrotic cells induced by ultraviolet B (UVB) radiation exposure. Pterygium formation is believed to be a tumorigenesis-like process induced by UVB exposure. In this study, we aimed to investigate the expression pattern of TLR3 in pterygium specimens and cultured pterygial epithelial cells (PECs).

Methods

Human pterygium and ipsilateral pterygium-free conjunctiva from the same patients were used in this study. The expression of TLR3 and nuclear factor-kappa B (NF-κB) was investigated in these specimens. PECs were exposed to UVB radiation to determine the effect of UVB on the expression of TLR3 and the activation of NF-κB.

Results

The immunofluorescence study showed stronger TLR3 expression in superficial epithelial cells in the pterygial epithelium in comparison with the normal conjunctival epithelium. The expression of TLR3 decreased in intensity from the superficial epithelium toward the basal cell layer, implying a correlation between UVB exposure and TLR3 expression. Differential TLR3 expression patterns in pterygial and conjunctival tissues were also found in quantitative PCR analyses. PECs after UVB irradiation had higher protein levels of TLR3 and phospho-NF-κB than those of the PECs without irradiation. Immunofluorescence studies showed that UVB irradiation induced the nuclear translocation of NF-κB in the PECs. In PECs with the targeted TLR3 gene silencing, the expression of phospho-NF-κB was not induced by UVB irradiation.

Conclusions

Our results indicate that UVB exposure, TLR3 expression, and NF-κB activation may be a critical sequence that leads to the formation of pterygium.

Comparison between the triamcinolone and bevacizumab subconjunctivals and changes in Interleukin-1 mRNA expression in pterygium

Objectives

Pterygium is a fibrovascular external ocular mass that grows from the conjunctiva into the cornea. The effect of subconjunctival injection of triamcinolone and bevacizumab has been inadequately investigated worldwide. This study aims to analyse the expression of IL-1 after the injection of triamcinolone and bevacizumab subconjunctiva.

Methods

All patients are randomized into three groups: the triamcinolone, bevacizumab group, and placebo groups, with 5 patients in each in group. All subjects are injected subconjunctivally one week before surgery, and then surgery is performed with the autograft technique. The main outcome measures include changes in the IL-1 mRNA expression between the triamcinolone, bevacizumab, and placebo groups.

Results

All samples are completed after one month of follow-up. The changes in blood levels of mRNA IL-1 expression are as follows: 4.81 ± 0.52 in the bevacizumab group, 3.40 ± 2.63 in the triamcinolone group, and 1.08 ± 1.48 in the placebo group (p = 0.04). In the comparison between groups, there is a significant effect between the bevacizumab and placebo groups, 3.73 ± 1.12 (p = 0.00), with no significant effect in the triamcinolone group, 1.40 ± 1.12 (p = 0.06).

Conclusion

The subconjunctival injection of bevacizumab and triamcinolone before surgery is effective in suppressing inflammation in pterygium.

Pterygium-The Good, the Bad, and the Ugly

Pterygium is a multifaceted pathology that displays apparent conflicting characteristics: benign (e.g., self-limiting and superficial), bad (e.g., proliferative and potentially recurrent) and ugly (e.g., signs of preneoplastic transformation). The natural successive question is: why are we lacking reports showing that pterygium lesions become life-threatening through metastasis, especially since pterygium has considerable similarities with UV-related malignancies on the molecular level? In this review, we consider how our pathophysiological understanding of the benign pterygium pathology overlaps with ocular surface squamous neoplasia and skin cancer. The three UV-related disorders share the same initial insult (i.e., UV radiation) and responsive repair mechanisms to the ensuing (in)direct DNA damage. Their downstream apoptotic regulators and other cellular adaptations are remarkably alike. However, a complicating factor in understanding the fine line between the self-limiting nature of pterygium and the malignant transformation in other UV-related diseases is the prominent ambiguity in the pathological evaluation of pterygium biopsies. Features of preneoplastic transformation (i.e., dysplasia) are used to define normal cellular reactions (i.e., atypia and metaplasia) and vice versa. A uniform grading system could help in unraveling the true nature of this ancient disease and potentially help in identifying the earliest intervention point possible regarding the cellular switch that drives a cell’s fate towards cancer.

Group and Shuffle Convolutional Neural Networks with Pyramid Pooling Module for Automated Pterygium Segmentation

Pterygium is an eye condition that is prevalent among workers that are frequently exposed to sunlight radiation. However, most of them are not aware of this condition, which motivates many volunteers to set up health awareness booths to give them free health screening. As a result, a screening tool that can be operated on various platforms is needed to support the automated pterygium assessment. One of the crucial functions of this assessment is to extract the infected regions, which directly correlates with the severity levels. Hence, Group-PPM-Net is proposed by integrating a spatial pyramid pooling module (PPM) and group convolution to the deep learning segmentation network. The system uses a standard mobile phone camera input, which is then fed to a modified encoder-decoder convolutional neural network, inspired by a Fully Convolutional Dense Network that consists of a total of 11 dense blocks. A PPM is integrated into the network because of its multi-scale capability, which is useful for multi-scale tissue extraction. The shape of the tissues remains relatively constant, but the size will differ according to the severity levels. Moreover, group and shuffle convolution modules are also integrated at the decoder side of Group-PPM-Net by placing them at the starting layer of each dense block. The addition of these modules allows better correlation among the filters in each group, while the shuffle process increases channel variation that the filters can learn from. The results show that the proposed method obtains mean accuracy, mean intersection over union, Hausdorff distance, and Jaccard index performances of 0.9330, 0.8640, 11.5474, and 0.7966, respectively.

Association among pterygium, cataracts, and cumulative ocular ultraviolet exposure: A cross-sectional study in Han people in China and Taiwan

Purpose

Pterygium is an ocular surface disorder mainly caused by ultraviolet (UV) light exposure. This study explored the relationships between six cataract types with pterygium and UV exposure.

Methods

We have previously studied cataracts in residents of three regions in China and Taiwan with different UV intensities. From that study, we identified 1,547 subjects with information on the presence or absence of pterygium. Pterygium severity was graded by corneal progress rate. Cataracts were graded by classification systems as three main types (cortical, nuclear, posterior subcapsular) and three subtypes (retrodots, waterclefts, fiber folds) with high prevalence in middle-aged and elderly people. We calculated the cumulative ocular UV exposure (COUV) based on subject data and National Aeronautics and Space Administration data on UV intensities and used logistic regression to calculate odds ratios for the associations of COUV, cataract, and pterygium.

Results

We found an overall pterygium prevalence of 23.3%, with significant variation among the three regions. Four cataract types (cortical, nuclear, posterior subcapsular, and retrodots) were significantly associated with the presence of pterygium.

Conclusions

There was a significant association between COUV and pterygium, indicating that COUV is associated with the risk of pterygium development and that pterygium is useful as an index of UV exposure. Furthermore, the type of cataract in eyes with pterygium may indicate the level of UV exposure.

Pterygium: an update on pathophysiology, clinical features, and management

Pterygium is a relatively common ocular surface disease. The clinical aspects and the treatment options have been studied since many years ago, but many uncertainties still exist. The core pathologic pathway and the role of heredity in the development of pterygium are still attractive fields for the researchers. The role of pterygium in corneal irregularities, in addition to the refractive properties of pterygium removal, has been increasingly recognized through numerous studies. The association between pterygium and ocular surface neoplasia is challenging the traditional beliefs regarding the safe profile of the disease. The need for a comprehensive clinical classification system has encouraged homogenization of trials and prediction of the recurrence rate of the pterygium following surgical removal. Evolving surgical methods have been associated with some complications, whose diagnosis and management are necessary for ophthalmic surgeons. According to the review, the main risk factor of pterygium progression remains to be the ultraviolet exposure. A major part of the clinical evaluation should consist of differentiating between typical and atypical pterygia, where the latter may be associated with the risk of ocular surface neoplasia. The effect of pterygium on astigmatism and the aberrations of the cornea may evoke the need for an early removal with a purpose of reducing secondary refractive error. Among the surgical methods, conjunctival or conjunctival-limbal autografting seems to be the first choice for ophthalmic surgeons because the recurrence rate following the procedure has been reported to be lower, compared with other procedures. The use of adjuvant options is supported in the literature, where intraoperative and postoperative mitomycin C has been the adjuvant treatment of choice. The efficacy and safety of anti–vascular endothelial growth factor agents and cyclosporine have been postulated; however, their exact role in the treatment of the pterygium requires further studies.

Expression and role of specificity protein 1 and collagen I in recurrent pterygial tissues

AIM

To investigate the expression profiles of the transcription factor specificity protein 1 (Sp1) and collagen I in recurrent pterygial tissues. What is more, to compare the changes of Sp1 and collagen I among primary pterygial tissue, recurrent pterygial tissue and conjunctival tissue.

METHODS

In the prospective study, we collected the pterygial tissues of 40 patients who underwent resection of primary pterygial tissue and recurrent pterygial tissue, and the conjunctival tissues of 10 patients with enucleation due to trauma. The relative expression levels of Sp1 and collagen I were analyzed by reverse transcription quantitative-polymerase chain reaction and Western blot. Paired t-test was performed to compare the Sp1 and collagen I of recurrent pterygial tissues, as well as the primary pterygial tissues and conjunctival tissues. In further, Pearson's hypothesis testing of correlation coefficients was used to compare the correlations of Sp1 and Collagen I.

RESULTS

The content of Sp1 and collagen I mRNA and protein was significantly greater in recurrent pterygial tissue than that was in primary and conjunctival tissue (P<0.05). There was a positive correlation between the mRNA and protein levels of Sp1 and collagen I in recurrent pterygial tissues (protein: r=0.913, P<0.05; mRNA: r=0.945, P<0.05).

CONCLUSION

Sp1 and collagen I are expressed in normal conjunctival, primary, and recurrent pterygial tissues, but expression is significantly greater in the latter. Sp1 and collagen I may be involved in the regulation of the development of recurrent pterygium.

Relative gene expression analysis of human pterygium tissues and UV radiation-evoked gene expression patterns in corneal and conjunctival cells

A sight threatening, pterygium is a common ocular surface disorders identified by fibrovascular growth of the cornea and induced by variety of stress factors, like ultraviolet (UV) exposure. However, the genes involved in the etiopathogenesis of this disease is not well studied. Herein, we identified the gene expression pattern of pterygium and examined the expression of pterygium-related genes in UV-B-induced human primary cultured corneal epithelial cells (HCEpCs), telomerase immortalized human corneal epithelial (hTCEpi), primary conjunctival fibroblast (HConFs) and primary pterygium fibroblast cells (HPFCs). A careful analysis revealed that the expression of 10 genes was significantly modulated (by > 10-fold). Keratin 24 (KRT24) and matrix metalloproteinase 9 (MMP-9) were dramatically upregulated by 49.446- and 24.214-fold, respectively. Intriguingly, UV-B exposure (50 J/m²) induced the upregulation of the expressions of MMP-9 in corneal epithelial cells such as HCEpCs and hTCEpi. Furthermore, UV-B exposure (100 and/or 200 J/m²) induced the upregulation of the expressions of MMP-9 in fibroblast such as HConFs and HPFCs. The exposure of HCEpCs to 100 and 200 J/m² UV-B induced significant expressions of KRT24 mRNA. Nevertheless, no expression of KRT24 mRNA was detected in HConFs and HPFCs. The findings provide evidence that the progression of pterygium may involve the modulation of extracellular matrix-related genes and vasculature development and the up-regulation of KRT24 and MMP-9 by UV stress. UV radiation may promote the modulation of these pterygium-related genes and induce the initiation and progression of human pterygium.

Fifteen-year incidence rate and risk factors of pterygium in the Southern Indian state of Andhra Pradesh

PURPOSE

To report 15-year incidence rate and associated risk factors of pterygium among people aged 30 years and above at baseline in the rural clusters of longitudinal Andhra Pradesh Eye Disease Study (APEDS III).

METHODS

The baseline APEDS I included 7771 participants of which 6447 (83%) were traced and 5395 (83.7%) were re-examined in APEDS III. To estimate the incidence of pterygium, we selected participants who were 30 years and above at baseline (4188), of which 2976 were traced and 2627 (88.3%) were examined, and based on inclusion criteria, 2290 participants were included in the study. The incidence rate of pterygium was defined as the proportion of people free of pterygium at baseline who had developed the condition at 15-year follow-up (range 13-17 years). Univariate and multivariable analyses for risk factors were undertaken.

RESULTS

The sex-adjusted incidence rate of pterygium was 25.2 per 100 person-years (95% CI 24.8 to 25.7) which was significantly higher for men than women (26.3 per 100 person-years (95% CI 25.6 to 27.0) and 24.7 (95% CI 24.1 to 25.3) respectively). At the multivariable analysis, male gender (RR: 1.35, 95% CI 1.0 to 1.83), no formal education (RR: 2.46, 95% CI 1.22 to 4.93), outdoor occupation (RR: 1.47, 95% CI 1.14 to 1.9) and lower body mass index (BMI) (<18.5) (RR: 1.25, 95% CI 1.02 to 1.55) were associated with increased risk of pterygium.

CONCLUSIONS

The overall incidence rate of pterygium was high in this rural population, especially in men and those engaged in outdoor activities, lack of formal education and with lower BMI. It is likely that greater exposure to ultraviolet light is a major contributing factor, thus warranting preventive strategies.

Long-term changes and effect of pterygium size on corneal topographic irregularity after recurrent pterygium surgery

This retrospective observational study compared long-term topographic changes after recurrent- and primary-pterygium surgery depending on pterygium size. Patients who underwent recurrent-pterygium excision between 2002–2013 and age, sex, and pterygium size-matched controls who underwent primary-pterygium surgery were included (33 eyes of 33 patients in each group). Pterygium size was graded per advancing edge position: <1/3 of corneal diameter (grade 1), outside the pupil (grade 2), and within the pupillary area (grade 3). Surface asymmetry index (SAI), surface regularity index (SRI) in corneal topography, and uncorrected and best-spectacle-corrected visual acuity were compared before and 1, 3, 6, and 12 months postoperatively. Three, 17, and 13 eyes had grades 1, 2, and 3, respectively. In grade 2, the SAI and SRI were respectively significantly larger at all observation points (p = 0.01, 0.03, 0.02, 0.02, and 0.004) and before and 6 and 12 months postoperatively (p = 0.02, 0.04, and 0.03) in recurrent pterygium. In grade 3, the SAI was significantly larger before and 1, 3, and 12 months postoperatively (p = 0.04, 0.01, 0.01, and 0.02) and the SRI was significantly larger before and 12 months postoperatively (p < 0.001, 0.02) in recurrent pterygium. Corneal irregularity persisted 12 months after recurrent-pterygium surgery compared with that in same-size primary pterygium.

Transcriptional profiling to identify the key genes and pathways of pterygium

Purpose

Pterygium results from a variety of biological pathways that are involved in the formation of ocular surface diseases. However, the exact pathogenesis of pterygium is still unclear. Our study focused on gene expression profiles to better understand the potential mechanisms of pterygium.

Methods

RNA sequencing experiments were performed on clinical pterygium tissues and normal conjunctival tissues. To identify the hub genes for the development of pterygium, we further conducted weighted gene co-expression network analysis (WGCNA). qRT-PCR was utilized to validate the dysregulation of the most significant differentially expressed genes (DEGs) and key hub genes in the independent subjects.

Results

A total of 339 DEGs (P-adjusted < 0.05 and log2 fold change [log2FC] ≥ 1.0) were obtained that reached statistical significance with p-values < 0.05. Among them, 200 DEGs were upregulated; these genes were mainly associated with the extracellular matrix and with cell adhesion or migration. In contrast, the 139 downregulated genes were enriched for endocrine and inflammation pathways. With regard to WGCNA, five modules were assigned based on the DEG profiles, and the biological functions of each module were verified with previously published GO terms. The functions included ECM-receptor interactions, the PI3K-Akt signalling pathway and an endoplasmic reticulum (ER)-related pathway. The five hub genes with the highest connectivity in each module and the five most significant DEGs showed dysregulated expression in the independent cohort samples.

Conclusions

RNA sequencing and WGCNA provided novel insights into the potential regulatory mechanisms of pterygium. The identified DEGs and hub genes, which were classified into two groups according to different functions or signalings, may provide important references for further research on the molecular biology of pterygium.

Optical Analysis and Reappraisal of the Peripheral Light Focusing Theory of Nasal Pterygia Formation

Purpose

Pterygia are much more common nasally than temporally. Ultraviolet (UV) radiation is a major risk factor. Coroneo proposed that the nasal preference is caused by the “peripheral light focusing effect,” (PLF), in which UV at an oblique angle passes through temporal cornea and is concentrated on and damages nasal limbal stem cells. This study evaluates whether the PLF is sufficient to explain the nasal preference.

Methods

Whereas Coroneo and colleagues derived the maximum PLF intensity gain (UV concentration factor) as a function of incident angle (i.e., different nasal limbal positions were used for different incident angles) the current analysis derived intensity gain at a fixed position such at the nasal corneo-limbal junction (CLJ). This provided a measure of the total PLF irradiation at this position, which was compared to total direct irradiation of nasal and temporal limbus at the corresponding positions (e.g., CLJs). In Part 1, analysis was performed like that of Coroneo, using horizontally incident UV; in Part 2, the analysis was extended to include incident rays above and below the horizontal.

Results

In both part 1 and part 2 of the study, the limbal UV irradiation of the nasal limbus from the PLF was not sufficient to explain the strong nasal location preference of pterygia.

Conclusions

The analysis calls into question the PLF explanation of nasal location preference. Other explanations of the nasal preference, and of pterygium pathogenesis, should be considered, such as temporal to nasal tear flow carrying substances such as cytokines to the nasal limbus.

A novel role for Livin in the response to ultraviolet B radiation and pterygium development

A pterygium is an inflammatory, invasive and proliferative lesion on the ocular surface, which can decrease visual acuity, damage the ocular surface and affect the appearance of the eye. However, the underlying molecular mechanisms of the pathogenesis remain unclear. In the present study, the role of apoptosis-associated protein Livin in the occurrence and development of pterygium was investigated. Primary samples from quiescent or advanced clinical stages of pterygium and normal human conjunctival tissues were used to assess mRNA and protein expression levels of Livin using reverse transcription-quantitative PCR and immunohistochemistry, respectively. Livin was knocked down in pterygium epithelial cells (PECs) using small interfering RNA (siRNA), to investigate the role of Livin in PEC viability, migration, invasion ability and apoptosis. The cell viability, invasion ability and apoptosis of PECs following ultraviolet B (UVB) radiation alone or in combination with Livin silencing were also analyzed. Expression levels of Livin increased in the pterygium tissues compared with those in the normal conjunctiva at both the mRNA and protein levels. Livin expression levels in advanced pterygium were significantly higher compared with those in quiescent pterygium samples. Knockdown of Livin expression levels significantly reduced cell migration, invasion ability and cell viability, and induced apoptosis of PECs. Inhibition of Livin expression in PECs increased the expression levels of caspase-7, caspase-3 and E-cadherin, whereas expression levels of Snail were downregulated. Cell viability and invasion ability in PECs was enhanced following UVB radiation and Livin expression upregulated. UVB irradiation induced cell invasion ability of PECs and this was attenuated by Livin-silencing. Transfection with Livin siRNA also partially recovered the apoptosis rate of PECs, which was reduced by UVB irradiation. In conclusion, Livin was upregulated in pterygium, and UVB radiation functions in the development of pterygium by inducing Livin expression.

Recurrence of Pterygium after Pterygium Excision with Stem Cell Graft and Amniotic Membrane Graft: A Comparison

Study objective

The objective of this study was to compare pterygium excision with amniotic membrane graft and that with stem cell graft in terms of pterygium recurrence, using a quasi-experimental study design. This study was conducted at the department of ophthalmology at Nishtar Hospital, Multan, Pakistan from January to September 2019.

Methodology and results

A total of 214 patients who presented to the outpatient section at the department of ophthalmology were included in this study. A lottery method was used to divide the patients into two equal groups: A and B. Patients in group A underwent pterygium excision with amniotic membrane graft, and patients in group B underwent pterygium excision with stem cell grafts. Follow-ups were planned for the third day, the second week, the first month, the third month, and the sixth month postoperatively. Frequency and percentage were calculated for qualitative variables and for quantitative data. Mean and standard deviation were calculated, and a p-value of <0.05 was considered significant. Postoperative complications (i.e., graft edema, hemorrhage, and recurrence) in group A were observed as n = 0 (0%), n = 11 (10.3%), and n = 15 (14%), respectively. Postoperative complications (i.e., graft edema, hemorrhage, and recurrence) in group B were observed as 15%, 3.7%, and 12.1%, respectively. Statistically, the difference for graft edema was significant (p = 0.000).

Conclusion

Stem cell grafting after pterygium excision was not associated with any major complications postoperatively. Stem cell grafting is better in terms of cosmetic appearance and has less recurrence rate as compared to amniotic membrane transplantation. 

Pterygium Pathology: A Prospective Case-Control Study on Tear Film Cytokine Levels

Pterygium is a common eye disease, linked to an increased exposure to UV radiation and dry environments. The associated pathology culminates in visual impairment and, in some rare cases, blindness. However, there remains a lot of uncertainty concerning the pathogenesis of this fibrovascular lesion. As the composition of the tear film provides a reflection into the pathological changes at the ocular surface, tear analysis represents an ideal approach to gain insight in the progression of disease following pterygiectomy. This study enrolled 19 patients and age/gender-matched healthy controls. Tear film levels of interleukin- (IL-) 6, IL-8, and vascular endothelial growth factor (VEGF) were investigated over time, and preoperative concentrations were linked to corneal neovascularization and pterygium size. Diminished tear film levels were found in unilateral patients who show no clinical signs of pterygium recurrence over a period of one year. Hence, our results highlight the potential of using the course of IL-6, IL-8, and VEGF levels in tears as biomarkers for recovery. In addition, when focusing on the affected eyes (i.e., primary and recurrent pterygium), we detected fold changes in preoperative cytokine concentrations to correspond with disease severity. As our proposed biomarkers did not reveal a linear relationship with corneal neovascularization nor the invasive behaviour of pterygium, no exact role in the pterygium pathology could be established. Hence, our data point to these factors being contributors rather than decisive players in the pathological processes.

Overexpression of fractalkine and its histopathological characteristics in primary pterygium

PURPOSE

This study aimed to evaluate the differences in the expressions of fractalkine in normal bulbar conjunctiva and primary pterygium tissues.

METHODS

The study included 48 patients who had been operated on for primary pterygium. Histopathologically, the presence of epithelial atypia, epithelial hyperplasia, goblet cell hyperplasia, epithelial lymphocytic exocytosis, stromal inflammation, mast cell count, and stromal vascularity were evaluated in the primary pterygium tissues. An immunohistochemical fractalkine stain was applied to the primary pterygium tissue samples and normal bulbar conjunctival tissue samples.

RESULTS

Primary pterygium and normal bulbar conjunctival tissue samples were histopathologically analyzed. Epithelial atypia, epithelial hyperplasia, epithelial lymphocytic exocytosis, stromal inflammation, stromal vascularity, and mast cell count were found to be significantly higher in the primary pterygium (p = 0.001, p = 0.002, p = 0.024, p = 0.007, p = 0.024, and p = 0.013, respectively). When evaluated in terms of fractalkine expression, the epithelial, vascular endothelial, and inflammatory cells were significantly higher in the primary pterygium (p ≤ 0.001, p = 0.002, p = 0.001, respectively). Moreover, compared to the normal bulbar conjunctiva, Ki-67 expression was significantly higher in the primary pterygium tissue samples.

CONCLUSION

Fractalkine might play a key role in the etiopathogenesis of pterygium. Fractalkine may be important in developing new treatment approaches.

Clinical Aspects of Pterygium in the Presence of Cataract

Two of the most common UV-induced eye affections are pterygium and cataract. They are both defined as progressive diseases that impair patients’ vision and share some common elements in their evolution process. The purpose of this study was to determine whether the presence of cataract influences the clinical signs and symptoms of patients with pterygium. Therefore, we have analyzed 84 patients with pterygium, among which 23 also presented cataract, as an overall study lot, as well as divided by age decades. We have determined that almost all patients with both pterygium and cataract declared extensive UV exposure in antecedents and have also reported a blurred vision. We found no correlation between the presence of cataract and the size of pterygium lesions, or symptoms like foreign body sensation, tearing or symblepharon.

Activation of the Sphingosine 1 Phosphate-Rho Pathway in Pterygium and in Ultraviolet-Irradiated Normal Conjunctiva

Sphingosine 1 phosphate (S1P) is a bioactive lipid that regulates cellular activity, including proliferation, cytoskeletal organization, migration, and fibrosis. In this study, the potential relevance of S1P–Rho signaling in pterygium formation and the effects of ultraviolet (UV) irradiation on activation of the S1P/S1P receptor axis and fibrotic responses were investigated in vitro. Expressions of the S1P2, S1P4, and S1P5 receptors were significantly higher in pterygium tissue than in normal conjunctiva, and the concentration of S1P was significantly elevated in the lysate of normal conjunctival fibroblast cell (NCFC) irradiated with UV (UV-NCFCs). RhoA activity was significantly upregulated in pterygium fibroblast cells (PFCs) and UV-NCFCs, and myosin phosphatase–Rho interacting protein (MRIP) was upregulated, and myosin phosphatase target subunit 1 (MYPT1) was downregulated in PFCs. Fibrogenic changes were significantly upregulated in both PFCs and UV-NCFCs compared to NCFCs. We found that the activation of the S1P receptor–Rho cascade was observed in pterygium tissue. Additionally, in vitro examination showed S1P–rho activation and fibrogenic changes in PFCs and UV-NCFCs. S1P elevation and the resulting upregulation of the downstream Rho signaling pathway may be important in pterygium formation; this pathway offers a potential therapeutic target for suppressing pterygium generation.

Pterygium in adults from the Brazilian Amazon Region: prevalence, visual status and refractive errors

AIMS

To determine prevalence of pterygium, its role as main cause of unilateral and bilateral visual impairment and blindness and its impact on refractive errors from adults living in a high ultraviolet exposure area in the Brazilian Amazon Region.

METHODS

Cluster sampling was used in randomly selecting subjects ≥45 years of age from urban and rural areas of Parintins city. Eligible subjects were enumerated through a door-to-door household survey and invited for an eye exam including refraction. Pterygium was assessed considering location (nasal, temporal or both) and size (<3 mm or ≥3 mm reaching or not pupillary margin).

RESULTS

A total of 2384 persons were enumerated and 2041 (85.6%) were examined. Prevalence of pterygium was 58.8% (95% CI 53.8% to 63.7%) and associated with male gender (OR=1.63; 95% CI 1.37 to 1.94; p=0.001), while higher education was a protective factor (OR=0.63; 95% CI 0.44 to 0.92; p=0.018). Older age and rural residence were associated with pterygium ≥3 mm reaching or not pupillary margin, while higher education was a protective factor for pterygium ≥3 mm reaching pupillary margin. Prevalence of pterygium as cause of visual impairment and blindness was 14.3% and 3.9%, respectively. Significantly higher hyperopic refractive errors were found in eyes with pterygium ≥3 mm reaching or not pupillary margin.

CONCLUSIONS

Pterygium was highly prevalent and the second cause of visual impairment and blindness after provision of refractive correction. Risk factors for pterygium were male gender, advanced age, lower education and rural residency. Strategies to provide pterygium early detection and proper management should be considered by healthcare authorities in this population.

Induction of Apoptosis in Pterygium Cells by Antagonists of Growth Hormone-Releasing Hormone Receptors

Purpose

The aim of the study was to investigate the signaling of growth hormone-releasing hormone receptor (GHRH-R) in the pathogenesis of pterygium and determine the apoptotic effect of GHRH-R antagonist on pterygium epithelial cells (PECs).

Methods

Fourteen samples of primary pterygium of grade T3 with size of corneal invasion ≥ 4 mm were obtained for investigation by histology, immunofluorescence, electron microscopy, explant culture, and flow cytometry.

Results

We found that PECs were localized in the basal layer of the epithelium in advancing regions of the head of pterygium. These cells harbored clusters of rough endoplasmic reticulum, ribosomes, and mitochondria, which were consistent with their aggressive proliferation. Immunofluorescence studies and Western blots showed that GHRH-R and the downstream growth hormone receptor (GH-R) were intensively expressed in PECs. Their respective ligands, GHRH and GH, were also elevated in the pterygium tissues as compared to conjunctival cells. Explanted PECs were strongly immunoreactive to GHRH-R and exhibited differentiation and proliferation that led to lump formation. Treatment with GHRH-R antagonist MIA-602 induced apoptosis of PECs in a dose-dependent manner, which was accompanied by a downregulation of ERK1 and upregulation of Caspase 3 expression.

Conclusions

Our results revealed that GHRH-R signaling is involved in survival and proliferation of PECs and suggest a potential therapeutic approach for GHRH-R antagonist in the treatment of pterygium.

Human papillomavirus infection and ocular surface disease (Review)

Human papillomavirus (HPV) infection has been implicated as a primary cause of lesions in the anogenital region, skin, oropharynx and respiratory tract. Additionally, the role of HPV in the pathogenesis of ocular surface disease has also been extensively studied. Conjunctival papilloma development has been strongly associated with the HPV infection of certain subtypes. On the other hand, the role of HPV in conjunctival pterygium, conjunctival intraepithelial neoplasia (CIN) and ocular surface squamous neoplasia (OSSN) remains controversial. Genetic predisposition and environmental factor is important in HPV hosts as regards the pathogenesis of ocular surface disease. Several studies have indicate a synergic role of HPV with ultraviolet radiation in pterygium establishment. A higher recurrence risk rate and more aggressive disease of ophthalmic pterygium is observed in cases of HPV infection. The purpose of this review was to provide a systematic review of the literature and to assist in a better understanding of the role of HPV in ocular surface disease.

Outcomes of Vertical Split Conjunctival Autograft Using Fibrin Glue in Treatment of Primary Double-Headed Pterygia

Purpose

To evaluate the efficiency of pterygium excision with the vertical split conjunctival technique using fibrin glue in treatment of primary double-headed pterygia.

Patients and Methods

15 eyes of 15 patients with primary double-headed pterygia that underwent vertical split conjunctival autograft pterygium surgery were retrospectively reviewed. Recurrence was defined as fibrovascular proliferation over the limbus onto the cornea.

Results

The patients' mean age was 36.92 ± 10.8 years. At 12-month follow-up, recurrence was not seen in any cases. Regarding postoperative cosmetic grading, grade 1 (the appearance of the operated site is not different from the normal appearance) was found in 12 eyes (80%) and grade 2 (some fine episcleral vessels in the excised area extending up to but not beyond the limbus and without fibrous tissue) was found in 3 eyes (20%). None of the cases showed conjunctival scarring or fibrosis at the conjunctival donor area. Preoperative Sim K astigmatism at the central 3 mm and BCVA were 3.05 ± 1.5 diopters (D) and 0.64 ± 0.26 logMAR, which improved significantly to 1.15 ± 0.84 D and 0.26 ± 0.18 logMAR at 12-month follow-up postoperatively, respectively.

Conclusion

Vertical split conjunctival autograft using fibrin glue is an effective technique with good cosmetic results and low to no recurrence for primary double-headed pterygia treatment. This trial is registered with NCT03507283.

Ologen Implantation versus Conjunctival Autograft Transplantation for Treatment of Pterygium

Purpose

To evaluate the effectiveness and safety of Ologen implantation versus conjunctival autograft transplantation for primary pterygium.

Methods

A retrospective case-series analysis. Thirty-one eyes of 29 patients were included in the Ologen group and 42 eyes of 35 patients in the autograft group. The patients were followed up for 1 year and evaluated for slit-lamp biomicroscopy, intraocular pressure, and adverse events. Recurrence rate, complications, and final appearance of the cases were evaluated prospectively.

Result

At 1 year after operation, 2 eyes recurred (6.5%) in the Ologen group and 4 eyes recurred (9.52%) in the autograft group. There was no statistically significant difference between both groups (P=0.157, χ² = 3.781). There was no occurrence of serious complications. Two eyes among the 31 eyes of the Ologen group were conjunctivitis; the incidence of complications was 6.45% (2 eyes). There was conjunctivitis in 3 eyes of the autograft group, 1 eye complicated with symblepharon, and 1 eye with conjunctival granuloma; the incidence of complications was 11.90% (5 eyes), and there was no statistically significant difference between both groups (P=0.094). The conjuntiva was less vascular and inflamed at 1 month postoperatively in the Ologen group than in the autograft group.

Conclusions

Ologen transplantation was technically easier, provided short operative time compared with conjunctival autograft transplantation, and preserved healthy conjunctiva with less complication and less recurrence; it may be a new, safe, and effective alternative for improving the short-term success rate of primary surgery.

UV light-blocking contact lenses protect against short-term UVB-induced limbal stem cell niche damage and inflammation

UVB irradiation has been linked to pathogenesis of pterygium, a conjunctival tumor growing onto transparent cornea, the windscreen of the eye. Due to corneal anatomy, ambient UVB irradiation is amplified at the stem cell-containing nasal limbus. The aim of this study was to analyse the effect of a UV-blocking contact lens (UVBCL, senofilcon A, Class 1 UV blocker) on limbal epithelial cells and fibroblasts under UVB irradiation compared to a non-UVB-blocking contact lens. UVBCL prevented UVB-induced DNA damage (as assessed by cyclobutane pyrimidine dimer immunostaining) as well as a decrease in proliferation and scratch wound closure rate of both limbal epithelial and fibroblast cells. Similarly, UVBCL protected limbal epithelial cells from UVB-induced loss of their phenotype in terms of colony forming efficiency and stem cell marker expression (ABCB5, P63α, integrin β1) compared to controls. Moreover, with UVBCL pro-inflammatory cytokines such as TNFα and MCP1 remained unchanged. These data demonstrate the significance of UV-protection in preserving the limbal niche in response to at least short-term UVB. Our data support the use of UVBCL in protecting limbal niche cells, especially after limbal stem cell transplantation and in patients after pterygium surgery, to help prevent recurrences.

YKL-40 expression in pterygium: a potential role in the pathogenesis

PURPOSE

The aim of the study was to evaluate whether YKL-40 (chitinase 3-like 1 protein) plays a role in pterygium pathogenesis.

METHODS

We included 42 primary pterygium patients and 24 control subjects with normal bulbar conjunctiva in the study. The pterygium patients were classified into the atrophic, fleshy, and intermediate groups according to the Tan classification. We then surgically removed the primary nasal pterygium and normal bulbar conjunctiva from the patients and immunohistochemically investigated YKL-40 expression.

RESULTS

YKL-40 expression was statistically significantly higher in the epithelial, endothelial, and stromal cells of the pterygium tissues than in the control tissues (P = 0.009, P = 0.003, P = 0.002, respectively). There was no significant correlation between the pterygium subgroups and YKL-40 expression (P > 0.05).

CONCLUSIONS

We believe YKL-40 may play a significant role in pterygium pathogenesis.

Association between Serum Immnunoglobulin E and Pterygium: A Population-Based Study from South Korea

PURPOSE

Several studies have shown that pterygium is associated with inflammation, angiogenesis, and fibrosis. However, it should be acknowledged that not enough is known about the association between immunoglobulin E (IgE) and pterygium. The present study was conducted to test the hypothesis that elevated serum IgE is associated with a greater prevalence of pterygium.

MATERIAL AND METHODS

A cross-sectional study was performed using data of 1,548 participants aged 30 years or older who were enrolled in the Korea National Health and Nutrition Examination Survey conducted in 2010. Multivariable logistic regression analysis was used to examine the relationship between pterygium and allergic conditions, including total serum IgE and allergen-specific serum IgE levels, after adjusting for potential confounding factors.

RESULTS

Participants with pterygium were more likely have increased IgE level (p = 0.009). After adjusting for potential confounders, the odds ratio (OR) for pterygium was greater in participants with higher total serum IgE levels (OR = 1.63; p = 0.047). Multivariable-adjusted ORs of pterygium across the tertile of increasing IgE were 1.00 (reference), 1.18, and 1.45, (P for linear trend = 0.038). Although the ORs for the upper two tertiles of cockroach and dog allergen-specific IgE were higher than those for the lowest tertile, allergen-specific serum IgE showed no clear association with pterygium.

CONCLUSIONS

Increased total serum IgE concentration is independently related to pterygium after adjusting for confounding factors. To the best of our knowledge, this study is the first research that reveals an association between serum IgE and pterygium.

Clinical outcome of combined conjunctival autograft transplantation and amniotic membrane transplantation in pterygium surgery

AIM

To compare long-term outcome of primary and recurrent pterygium surgery with three different techniques: combined conjunctival autograft and overlay amniotic membrane transplantation (CAT with AMT), conjunctival autograft transplantation (CAT) alone and amniotic membrane transplantation (AMT) alone.

METHODS

In this retrospective study, 142 eyes of 142 pterygium patients (104 primary, 38 recurrent) who underwent CAT (group A), AMT (group B) or CAT with AMT (group C) respectively following surgical excision were reviewed and compared based on the recurrences and post-operative complications.

RESULTS

The number of recurrence post-surgery were 17 (9 from primary, 8 from recurrent; the same description below), 18 (10, 8) and 2 (1, 1) in groups A, B, and C respectively; dry eyes were 22 (16, 6), 27 (18, 9) and 7 (3, 4); conjunctival inflammations were 30 (17, 13), 27 (16, 11) and 11 (6, 5). Patients in group C (either primary or recurrent or both) mainly showed significantly better results than those in group A or B (P<0.05) regarding above-mentioned clinical effects.

CONCLUSION

Combined CAT and overly AMT have significantly lower rates of recurrence and postoperative complications for primary and recurrent pterygium surgery than CAT or AMT alone.

Autophagy mediates cell cycle response by regulating nucleocytoplasmic transport of PAX6 in limbal stem cells under ultraviolet-A stress

Limbal stem cells (LSC) account for homeostasis and regeneration of corneal epithelium. Solar ultraviolet A (UVA) is the major source causing oxidative damage in the ocular surface. Autophagy, a lysosomal degradation mechanism, is essential for physiologic function and stress defense of stem cells. PAX6, a master transcription factor governing corneal homeostasis by regulating cell cycle and cell fate of LSC, responds to oxidative stress by nucleocytoplasmic shuttling. Impaired autophagy and deregulated PAX6 have been reported in oxidative stress-related ocular surface disorders. We hypothesize a functional role for autophagy and PAX6 in LSC’s stress response to UVA. Therefore, human LSC colonies were irradiated with a sub-lethal dose of UVA and autophagic activity and intracellular reactive oxygen species (ROS) were measured by CYTO-ID assay and CM-H₂DCFDA live staining, respectively. Following UVA irradiation, the percentage of autophagic cells significantly increased in LSC colonies while intracellular ROS levels remained unaffected. siRNA-mediated knockdown (KD) of ATG7 abolished UVA-induced autophagy and led to an excessive accumulation of ROS. Upon UVA exposure, LSCs displayed nuclear-to-cytoplasmic translocation of PAX6, while ATG7KD or antioxidant pretreatment largely attenuated the intracellular trafficking event. Immunofluorescence showing downregulation of proliferative marker PCNA and induction of cell cycle regulator p21 indicates cell cycle arrest in UVA-irradiated LSC. Abolishing autophagy, adenoviral-assisted restoration of nuclear PAX6 or antioxidant pretreatment abrogated the UVA-induced cell cycle arrest. Adenoviral expression of an ectopic PAX gene, PAX7, did not affect UVA cell cycle response. Furthermore, knocking down PAX6 attenuated the cell cycle progression of irradiated ATG7KD LSC by de-repressing p21 expression. Collectively, our data suggest a crosstalk between autophagy and PAX6 in regulating cell cycle response of ocular progenitors under UVA stress. Autophagy deficiency leads to impaired intracellular trafficking of PAX6, perturbed redox balance and uncurbed cell cycle progression in UVA-stressed LSCs. The coupling of autophagic machinery and PAX6 in cell cycle regulation represents an attractive therapeutic target for hyperproliferative ocular surface disorders associated with solar radiation.