Anatomical and Immunological Changes of the Cornea in Patients with Pterygium

[Current possibilities for the diagnosis and treatment of pterygium]

Pterygium is a common inflammatory-proliferative disease characterized by the invasion of degeneratively altered fibrovascular tissue into the cornea. This literature review analyzes the etiological factors and pathogenetic concepts of its development, describes modern methods of diagnostics and surgical treatment of pterygium, and pays particular attention to the assessment of structural and functional changes in the cornea occurring during the growth of pterygium and after its excision.

Density and distribution of dendritiform cells in the peripheral cornea of healthy subjects using in vivo confocal microscopy

PURPOSE

To establish dendritiform cell (DC) density and morphological parameters in the central and peripheral cornea in a large healthy cohort, using in vivo confocal microscopy (IVCM).

METHODS

A prospective, cross-sectional, observational study was conducted in 85 healthy volunteers (n = 85 eyes). IVCM images of corneal center and four peripheral zones were analyzed for DC density and morphology to compare means and assess correlations (p < 0.05 being statistically significant).

RESULTS

Central cornea had lower DC density (40.83 ± 5.14 cells/mm²; mean ± SEM) as compared to peripheral cornea (75.42 ± 2.67 cells/mm², p < 0.0001). Inferior and superior zones demonstrated higher DC density (105.01 ± 7.12 and 90.62 ± 4.62 cells/mm²) compared to the nasal and temporal zones (59.93 ± 3.42 and 51.77 ± 2.98 cells/mm², p < 0.0001). Similarly, lower DC size, field and number of dendrites were observed in the central as compared to the average peripheral cornea (p < 0.0001), with highest values in the inferior zone (p < 0.001 for all, except p < 0.05 for number of dendrites in superior zone). DC parameters did not correlate with age or gender. Inter-observer reliability was 0.987 for DC density and 0.771-0.922 for morphology.

CONCLUSION

In healthy individuals, the peripheral cornea demonstrates higher DC density and larger morphology compared to the center, with highest values in the inferior zone. We provide the largest normative cohort for sub-stratified DC density and morphology, which can be used in future clinical trials to compare differential changes in diseased states. Furthermore, as DC parameters in the peripheral zones are dissimilar, random sampling of peripheral cornea may be inaccurate.

Evaluation of pterygium severity with en face anterior segment optical coherence tomography and correlations with in vivo confocal microscopy

PURPOSE

To describe en face anterior segment optical coherence tomography (EF-OCT) characteristics of pterygia and their correlation with in vivo confocal microscopy (IVCM).

PATIENTS AND METHODS

In this observational case series, we prospectively included 21 eyes of 17 subjects with pterygium. All subjects underwent detailed ophthalmic examination, anterior segment photography, an ocular surface disease index (OSDI) questionnaire, IVCM, and EF-OCT. Eyes were divided into two groups according to pterygium severity (Modified Pterygium Classification System) and OSDI score. EF-OCT images for both groups were analyzed for surface area of Fuchs Patches (FP). The IVCM activity score was based on the number of inflammatory cells, blood vessels, activated keratocytes and the appearance of the cornea/pterygium at the head of the pterygium. The correlations between EF-OCT and IVCM images were then analyzed and compared in both groups.

RESULTS

EF-OCT permits clear visualization and evaluation of FPs and the border between the pterygium and the adjacent cornea. The severe pterygium group was characterized by irregular borders and larger FPs (0.13±0.06 mm² versus 0.06±0.02 mm² respectively) (P=0.003). The mean IVCM activity score was 2.36±0.81 in the severe pterygium group and 1.2±0.42 in the mild pterygium group (P=0.0013). There was a positive correlation between FP surface area and IVCM activity score. A larger FP surface area was associated with a higher activity score on IVCM.

CONCLUSION

EF-OCT allows good evaluation of pterygium extension, borders and FP surface area. EF-OCT analysis of pterygium could represent a simple, non-invasive and reproducible method to evaluate pterygium severity and activity.

MiR-15a Participated in the Pathogenesis of Pterygium via Targeting BCL-2：An Experimental Research

Purpose: To compare the expression levels of miR-15a between pterygium and normal conjunctiva, and further investigate the potential role of miR-15a in the progression of pterygium.Methods: 21 cases of primary pterygium were enrolled in our study. The length of the pterygium invaded into the cornea and the total thickness of the pterygium were measured with anterior segment optical coherence tomography (AS-OCT). The pterygial and adjacent normal conjunctival samples of the 21 patients were collected. Expressions of miR-15a, BCL-2, Bax in both pterygium and normal conjunctiva were measured, and correlations between miR-15a and BCL-2, miR-15a and Bax, miR-15a and clinical parameters were made. Pterygium epithelial cells (PECs) were isolated, cultured and transfected with miR-15a mimic or miR-15a inhibitor to interfere the miR-15a expression levels. The regulation of BCL-2 expression by miR-15a was examined with Real-Time PCR (RT-PCR), Western blot and immunofluorescence. The regulation of Bax expression by miR-15a was also examined with Real-Time PCR (RT-PCR) and Western blot. The cell viability of the transfected PECs was measured with the CCK-8 assay and the apoptosis in these cells was detected using the TUNEL assay.Results: The expression of miR-15a, Bax were significantly decreased while the BCL-2 was significantly increased in pterygium (p < .05). There was a negative correlation in expression between miR-15a and BCL-2 in pterygium tissues (r = -0.516, p < .05). We also found that relative miR-15a level was positively correlated with the length of pterygium invaded into the cornea (r = -0.570, p < .05). In cultured PECs, miR-15a could downregulate the expression of BCL-2 and upregulate the expression of Bax. Promotion of miR-15a could suppress cell proliferation and promote cell apoptosis in cultured PECs.Conclusions: Our study demonstrated that decreased expression of miR-15a in pterygium might be associated with the apoptosis and proliferation of abnormal cell via regulating BCL-2, which could subsequently contribute to the development of pterygium. Downregulation of miR-15a might also contribute to the pathogenesis of pterygium by other mechanisms including abnormal proliferation and neovascularization, which remain to be investigated.

In Vivo Confocal Microscopy Observation of Cell and Nerve Density in Different Corneal Regions with Monocular Pterygium

Purpose

To investigate the effects of pterygium on corneal cell and nerve density in patients with unilateral pterygium using in vivo laser scanning confocal microscopy (LSCM).

Methods

In this cross-sectional study, 24 patients with unilateral pterygium who were treated in the Department of Ophthalmology of the Second People's Hospital of Wuxi City from April 2018 to July 2018 were analyzed. Each eye with pterygium and its fellow eye were imaged by LSCM. The density of basal corneal epithelial cells, anterior stromal cells, posterior stromal cells, dendritic cells, and endothelial cells in pterygium and adjacent clear cornea was measured. In the fellow eyes, the central cornea, nasal cornea, nasal mid-peripheral cornea, and temporal cornea were imaged. The difference in the density of cells and subepithelial nerve fibers in different corneal regions of eyes with pterygium was analyzed. The cell and nerve density of the fellow cornea were also measured to exclude the influencing factors.

Results

The density of corneal basal epithelial cells in the central corneas of eyes with pterygium was 6497 ± 1776 cells/mm², which was higher than that in the area near the head of pterygium (5580 ± 1294 cells/mm², P < 0.001), the region above pterygium (6097 ± 1281 cells/mm², P=0.049), and the region below pterygium (5463 ± 1007 cells/mm², P=0.001). The density of anterior stromal cells in the central cornea was 742 ± 243 cells/mm², which was higher than that in the area near the head of pterygium (587 ± 189 cells/mm², P=0.005), the region below pterygium (492 ± 159 cells/mm², P=0.005), and the temporal cornea (574 ± 164 cells/mm², P=0.003). The density of endothelial cells in the central cornea was 2398 ± 260 cells/mm², which was higher than that in the area near the head of pterygium (2296 ± 231 cells/mm², P=0.011) and the region below pterygium (2272 ± 400 cells/mm², P=0.020). The density of dendritic cells in the central cornea was 53 ± 48 cells/mm², which was lower than that in the area near the head of pterygium (250 ± 224 cells/mm², P=0.001), the upper region (103 ± 47 cells/mm², P=0.006), and the lower region (90 ± 48 cells/mm², P=0.023). The corneal nerve fiber length (CNFL) in the center was higher than that in the area near the head of pterygium, the upper region, and the lower region. Compared with fellow eyes, eyes with pterygium had a significantly higher mean corneal power (KM) (P < 0.001). There was a significant positive linear relationship between the corneal area invaded by pterygium of pterygia and KM (r = 0.609, P=0.009).

Conclusion

Basal epithelial cells, stromal cells, endothelial cells, dendritic cells, and subepithelial nerve fibers in the central cornea of eyes with pterygium were different from those of pterygium and adjacent clear cornea. LSCM is effective for observing the morphology and quantity of corneal cells in pterygium.

Antigen-presenting cells in ocular surface diseases

PURPOSE

To review the role of antigen-presenting cells (APC) in the pathogenesis of ocular surface diseases (OSD).

METHODS

A thorough literature search was performed in PubMed database. An additional search was made in Google Scholar to complete the collected items.

RESULTS

APCs have the ability to initiate and direct immune responses and are found in most lymphoid and non-lymphoid tissues. APCs continuously sample their environment, present antigens to T cells and co-ordinate immune tolerance and responses. Many different types of APCs have been described and there is growing evidence that these cells are involved in the pathogenesis of OSD. OSD is a complex term for a myriad of disorders that are often characterized by ocular surface inflammation, tear film instability and impairment of vision.

CONCLUSIONS

This review summarizes the current knowledge concerning the immunotopographical distribution of APCs in the normal ocular surface. APCs appear to play a critical role in the pathology of a number of conditions associated with OSD including infectious keratitis, ocular allergy, dry eye disease and pterygium.

Corneal Reinnervation and Sensitivity Recovery after Pterygium Excision

Purpose

To evaluate changes in corneal sensitivity and subbasal nerve density after pterygium excision.

Methods

This prospective trial included 22 eyes with nasal primary pterygium and 18 controls. Corneal sensitivity was evaluated using a Cochet–Bonnet esthesiometer in the nasal, superior, temporal, inferior, and center quadrants of the cornea before surgery and 10 days, 1 month, and 3months after surgery. The central cornea was analyzed using in vivo confocal microscopy (IVCM) before surgery and 1 and 3 months after surgery. Subbasal nerve density and other nerve parameters were analyzed using NeuronJ. Nerve tortuosity was evaluated and graded in individual IVCM scans. The tear film break-up time (TBUT) test and Schirmer's test were performed before surgery, as well as 1 and 3 months after surgery. All the same tests were performed in the controls.

Results

All affected eyes showed a significant increase in corneal sensitivity in the nasal corneal quadrant after surgery when compared with preoperative data (F = 37.3; P < 0.01). Compared with controls, pterygium patients demonstrated decreased corneal subbasal nerve density (P < 0.01). Compared with controls, pterygium patients demonstrated decreased corneal subbasal nerve density (P < 0.01). Compared with controls, pterygium patients demonstrated decreased corneal subbasal nerve density (P < 0.01). Compared with controls, pterygium patients demonstrated decreased corneal subbasal nerve density (F = 37.3; P < 0.01). Compared with controls, pterygium patients demonstrated decreased corneal subbasal nerve density (P < 0.01). Compared with controls, pterygium patients demonstrated decreased corneal subbasal nerve density (F = 37.3; P < 0.01). Compared with controls, pterygium patients demonstrated decreased corneal subbasal nerve density (

Conclusion

Pterygium patients demonstrated deteriorated corneal subbasal nerve fibers when compared with healthy controls in terms of nerve length, nerve trunks, and nerve branches. Therefore, pterygium excision improves corneal sensitivity and increases corneal subbasal nerve density.

Corneal epithelial dendritic cell density in the healthy human cornea: A meta-analysis of in-vivo confocal microscopy data

PURPOSE

Numerous studies have reported a wide range of corneal epithelial dendritic cells (CEDC) density using in-vivo confocal microscopy in healthy participants. It is necessary to establish normal CEDC values for healthy corneas to enable differentiation from pathological corneas. This meta-analysis aimed to establish CEDC density and distribution and examine their relationship with age and sex.

METHODS

A systematic review of the literature of studies using the Heidelberg Retinal Tomograph with Rostock Corneal Module and reporting CEDC density in healthy subjects up to December 2018 was conducted via Medline, Google Scholar, Scopus, PubMed, Embase and Cochrane library. A random effect modeling approach was used to obtain the results of meta-analysis and meta-regression was conducted to estimate the effect of age and sex.

RESULTS

38 studies reported central and 9 reported peripheral inferior CEDC density of 1203 participants (mean age 46.0 ± 12.2, range 18-81 years). CEDC density in the central and peripheral inferior cornea was 26.4 ± 13.6 cells/mm² (95% CI:22.5-26.8) and 74.9 ± 22.7 cells/mm² (95%CI:59.8-90.0), respectively. No effect of age was found on central CEDC density (p = 0.63); whereas peripheral CEDC density decreased with increasing age (p = 0.02). CEDC density was not influenced by sex at either location (p > 0.48).

CONCLUSION

This study established that the density at the peripheral inferior cornea is three-fold higher than at the central cornea. Peripheral but not central CEDC density decreased with increasing age. There are limited studies in youth (<18 years), precluding a more detailed analysis. Sex does not appear to be a significant factor in CEDC density.

The Role of Limbal Epithelial Stem Cells in Regulating Corneal (Lymph)angiogenic Privilege and the Micromilieu of the Limbal Niche following UV Exposure

The cornea is a clear structure, void of blood, and lymphatic vessels, functioning as our window to the world. Limbal epithelial stem cells, occupying the area between avascular cornea and vascularized conjunctiva, have been implicated in tissue border maintenance, preventing conjunctivalisation and propagation of blood and lymphatic vessels into the cornea. Defects in limbal epithelial stem cells are linked to corneal neovascularisation, including lymphangiogenesis, chronic inflammation, conjunctivalisation, epithelial abnormalities including the presence of goblet cells, breaks in Bowman's membrane, persistent epithelial defects and ulceration, ocular surface squamous neoplasia, lipid keratopathy, pain, discomfort, and compromised vision. It has been postulated that pterygium is an example of focal limbal deficiency. Previous reports showing changes occurring in limbal epithelium during pterygium pathogenesis suggest that there is a link to stem cell damage. In this light, pterygium can serve as a model disease of UV-induced stem cell damage also characterised by corneal blood and lymphangiogenesis. This review focuses on the role of corneal and limbal epithelial cells and the stem cell niche in maintaining corneal avascularity and corneal immune privilege and how this may be deregulated following UV exposure. We present an overview of the PUBMED literature in the field as well as recent work from our laboratories.

A comparative study of different concentrations of topical bevacizumab on the recurrence rate of excised primary pterygium: a short-term follow-up study

The present study was undertaken to compare the pterygium recurrence rates after treatment with two different concentrations of topical bevacizumab in those who had undergone a primary pterygium excision. The 90 patients who underwent pterygium excision were enrolled in this prospective, placebo-controlled double-blinded interventional case series. The participants were randomly categorized into 3 groups each consisting of 30 subjects. 24 h after surgery, Group II and Group III received a total of 5 and 10 mg/mL dose of topical bevacizumab, respectively; whereas patients in Group I were administered only a placebo starting a day after surgery. Participants were instructed to instill their topical medicines 4 times a day for 1 week. The patients were examined for pterygium recurrence and complications at postoperative 1, 7, and 14 days as well as each month during the following year. Pterygia recurred in 14 patients (46.7 %) in Group I and in 4 patients (13.3 %) in Group II. No recurrence was observed in Group III during the follow-up period. The Kaplan-Meier survival analysis disclosed a significantly better outcome for those who had been treated with 10 mg/mL concentrations of bevacizumab (Mantel-Cox log rank analysis, P < 0.001). The mean recurrence time was not significantly different between Group I and Group II. No ocular or systemic complication developed till the end of follow-up. Thus, 10 mg/mL concentration of topical bevacizumab was more efficacious than 5 mg/mL dose in preventing pterygium recurrence.

Auto-avulsion and resolution of corneal pterygium

PURPOSE

Corneal pterygium is a frequently encountered ocular condition in clinical practice. The lesion presents as a fibrous, winged-like growth that typically manifests on the nasal aspect of the conjunctiva and cornea. Pterygia can be surgically removed by excision when they cause significant discomfort, visual impairment, or poor cosmesis. However, the recurrence rate after excision remains high without adjunctive therapy. We present an exceedingly rare case of resolution of a pterygium by auto-avulsion followed by subsequent recurrence of the lesion.

CASE REPORT

A 63-year-old Asian man presented to the clinic with pain and foreign body sensation. Anterior segment evaluation revealed a large corneal epithelial defect with an adjacent area of loose conjunctival tissue. Ocular history included a pterygium in the same area of the defect. Subsequent follow-up revealed a regrowth of the pterygium at the exact location.

CONCLUSIONS

Strong tension imposed on the cornea by a pterygium could result in auto-avulsion of the lesion. The resulting corneal defect can then be treated accordingly. Recurrent pterygium is possible without adjunctive therapy, such as those seen with bare sclera excision.

Expression of SFRP Family Proteins in Human Keratoconus Corneas

We investigated the expression of the secreted frizzled-related proteins (SFRPs) in keratoconus (KC) and control corneas. KC buttons (∼8 mm diameter) (n = 15) and whole control corneas (n = 7) were fixed in 10% formalin or 2% paraformaldehyde and subsequently paraffin embedded and sectioned. Sections for histopathology were stained with hematoxylin and eosin, or Periodic Acid Schiff's reagent. A series of sections was also immunolabelled with SFRP 1 to 5 antibodies, visualised using immunofluorescence, and examined with a Zeiss LSM700 scanning laser confocal microscope. Semi-quantitative grading was used to compare SFRP immunostaining in KC and control corneas. Overall, KC corneas showed increased immunostaining for SFRP1 to 5, compared to controls. Corneal epithelium in all KC corneas displayed heterogeneous moderate to strong immunoreactivity for SFRP1 to 4, particularly in the basal epithelium adjacent to cone area. SFRP3 and 5 were localised to epithelial cell membranes in KC and control corneas, with increased SFRP3 cytoplasmic expression observed in KC. Strong stromal expression of SFRP5, including extracellular matrix, was seen in both KC and control corneas. In control corneas we observed differential expression of SFRP family proteins in the limbus compared to more central cornea. Taken together, our results support a role for SFRPs in maintaining a healthy cornea and in the pathogenesis of epithelial and anterior stromal disruption observed in KC.

Oral doxycycline reduces pterygium lesions; results from a double blind, randomized, placebo controlled clinical trial

PURPOSE

To determine whether oral doxycycline treatment reduces pterygium lesions.

DESIGN

Double blind, randomized, placebo controlled clinical trial.

PARTICIPANTS

98 adult patients with primary pterygium.

METHODS

Patients were randomly assigned to receive 100 mg oral doxycycline twice a day (49 subjects), or placebo (49 subjects), for 30 days. Photographs of the lesion were taken at the time of recruitment and at the end of the treatment. Follow-up sessions were performed 6 and 12 months post-treatment. Statistical analyses for both continuous and categorical variables were applied. p values of less than 0.05 were considered to indicate statistical significance.

MAIN OUTCOME MEASURES

The primary endpoint was the change in lesion size after 30 days of treatment.

RESULTS

The primary endpoint was not met for the whole population but subgroup analysis showed that doxycycline was effective in patients of Caucasian origin while other ethnicities, mostly Hispanic, did not respond to the treatment. Moreover, there was a correlation between age and better response (p = 0.003). Adverse events were uncommon, mild, and in agreement with previous reports on short doxycycline treatments.

CONCLUSIONS

Oral doxycycline was superior to placebo for the treatment of primary pterygia in older Caucasian patients. These findings support the use of doxycycline for pterygium treatment in particular populations.

TRIAL REGISTRATION

European Union Clinical Trials Register EudraCT 2008-007178-39.

In vivo confocal microscopic evaluation of morphologic changes and dendritic cell distribution in pterygium

PURPOSE

To observe morphologic changes and the distribution of dendritic cells in pterygium using in vivo laser scanning confocal microscopy (LSCM).

DESIGN

Prospective comparative study.

METHODS

Twenty-six eyes of 26 patients with pterygium and 17 eyes of 17 healthy subjects were recruited. Using LSCM, in vivo images of the pterygium and adjacent clear cornea were captured. The density of basal corneal epithelial cells and keratocytes in the anterior and posterior stroma and the density of dendritic cells in the pterygium and adjacent clear cornea were determined. In the controls, the central cornea and nasal bulbar conjunctiva were imaged. The density of basal corneal epithelial cells, keratocytes, and dendritic cells was evaluated.

RESULTS

Morphologic alterations of the sub-basal nerve plexus were observed in pterygium. The density of basal corneal epithelial cells and anterior keratocytes in pterygium was 5359.0 ± 543.1 cells/mm² and 407.4 ± 188.7 cells/mm² respectively, which was significantly lower than that in the controls (P < .001). The density of dendritic cells in the clear corneas of pterygia was 60.3 ± 25.5 cells/mm², which was significantly higher than the 23.6 ± 11.1 cells/mm² in the central corneas of controls (P < .001). The dendritic cell density in the pterygium was significantly higher than the density in the nasal bulbar conjunctiva of controls (P < .001).

CONCLUSIONS

Histopathologic alterations and increased dendritic cells were evident in pterygium and the adjacent clear cornea by in vivo LSCM. In vivo LSCM was found to be an effective method of observing the morphologic alterations of pterygium.