Cell cycle kinetics in pterygium at three latitudes

Genomic instability and eye diseases

Background

Genetic information is stored in the bases of double-stranded DNA. However, the integrity of DNA molecules is constantly threatened by various mutagenic agents, including pollutants, ultraviolet light (UV), and medications. To counteract these environmental damages, cells have established multiple mechanisms, such as producing molecules to identify and eliminate damaged DNA, as well as reconstruct the original DNA structures. Failure or insufficiency of these mechanisms can cause genetic instability. However, the role of genome stability in eye diseases is still under-researched, despite extensive study in cancer biology.

Main text

As the eye is directly exposed to the external environment, the genetic materials of ocular cells are constantly under threat. Some of the proteins essential for DNA damage repair, such as pRb, p53, and RAD21, are also key during the ocular disease development. In this review, we discuss five ocular diseases that are associated with genomic instability. Retinoblastoma and pterygium are linked to abnormal cell cycles. Fuchs' corneal endothelial dystrophy and age-related macular degeneration are related to the accumulation of DNA damage caused by oxidative damage and UV. The mutation of the subunit of the cohesin complex during eye development is linked to sclerocornea.

Conclusions

Failure of DNA damage detection or repair leads to increased genomic instability. Deciphering the role of genomic instability in ocular diseases can lead to the development of new treatments and strategies, such as protecting vulnerable cells from risk factors or intensifying damage to unwanted cells.

Vascular Endothelial Growth Factor expression patterns in non- Human Papillomavirus - related pterygia: an experimental study on cell spot arrays digital analysis

PURPOSE

The role of angiogenic factors -such as vascular endothelial growth factor (VEGF) - in development and progression of pterygia lesions remains under investigation. In the current study, we analyzed VEGF protein expression in a series of pterygia and normal conjunctiva epithelia.

METHODS

Using a liquid based cytology assay, thirty (n = 30) cell specimens were obtained by applying a smooth scraping on conjunctiva epithelia and fixed accordingly. None of them had a history of Human Papillomavirus (HPV) infection. Similarly, the same process was applied also in normal conjunctiva epithelia (n = 10; control group). We constructed five (n = 5) slides each containing eight (n = 8) cell spots. An immunocytochemistry (ICC) assay was implemented. Digital image analysis was also performed for evaluating objectively the corresponding immunostaining intensity levels.

RESULTS

All the examined pterygia cell samples over expressed the marker. High staining intensity levels were detected in 15/30 (50%), whereas the rest 15/30 (50%) demonstrated moderate expression. Overall VEGF expression was statistically significantly higher in pterygia compared to normal conjunctiva epithelia (p=.0001). Concerning the other parameters, VEGF protein expression did not associate with the gender of the patients (p = 0.518), the presence of recurrent lesion (p = 0.311), the anatomical location (p = 0.191) or with their morphology (p = 0.316). Interestingly, the recurrent lesions demonstrated the highest levels of VEGF expression.

CONCLUSIONS

VEGF over expression is a frequent event in pterygia playing a potentially central molecular role in the progression of the lesion. Cell spot array analysis -based on liquid cytology- seems to be an innovative, easy to use technique for analyzing a broad variety of molecules in multiple specimens on the same slide by applying different ICC assays.

Tear Fluid and Serum Vitamin D Concentrations in Unilateral Pterygium

SIGNIFICANCE

Vitamin D has antiangiogenic, anti-inflammatory, and antifibrotic properties, which may play an inhibitory role on pterygium formation. Vitamin D concentration was measured in few studies, and contradictory results have been reported. There is no study investigating tear fluid concentration of vitamin D in pterygium patients.

PURPOSE

This study evaluated tear fluid and serum vitamin D concentrations of pterygium patients in comparison with healthy controls.

METHODS

Thirty-five (21 male, 14 female) patients with unilateral pterygium and 25 (18 male, 7 female) healthy controls were included in this case-control study. After full ophthalmic examination, blood samples were taken, and basal tear fluid was collected using glass microcapillary tubes. Tear fluid and serum vitamin D concentrations were analyzed using enzyme-linked immunosorbent assay and analyzed statistically.

RESULTS

The mean ± standard deviation age of patients was 51.7 ± 16.7 years in the study group and 50.6 ± 18.7 years in the control group, respectively (P = .82). The mean tear fluid vitamin D concentration was statistically significantly higher than the mean serum concentration in the study groups (P < .0001). The mean tear fluid (P = .76) and serum vitamin D concentrations (P = .53) did not reveal statistically significant difference between patients and controls. There was no statistically significant difference for tear fluid vitamin D concentration between pterygium eyes and fellow eyes (P = .93). The difference in concentrations was compared within the pterygium subgroups, and it was found that the mean serum vitamin D concentration trended toward lower values as the stage of pterygium increased, and the mean tear fluid vitamin D concentration trended toward higher values as the stage of pterygium increased, although these differences were not statistically significant (all, P > .05).

CONCLUSIONS

Tear fluid and serum vitamin D concentrations do not seem to have a role in pterygium pathogenesis.

Bcl-2, p53, and Ki-67 expression in pterygium and normal conjunctiva and their relationship with pterygium recurrence

PURPOSE

Pterygium is a common lesion of the ocular surface, and its etiology and pathogenesis are still uncertain. This study aimed to investigate the role of apoptosis and proliferation in pterygium formation and recurrence.

MATERIALS AND METHODS

In this study, p53, Bcl-2, and Ki-67 expression levels were evaluated in primary pterygium (n = 35) and recurrent pterygium (n = 32) tissue samples and compared with normal conjunctiva (n = 30) tissue samples. In addition, recurrent pterygiums were divided into three groups based on recurrence time, and their p53, Bcl-2, and Ki-67 expression levels were compared.

RESULTS

The results show that p53, Bcl-2, and Ki-67 expression levels were significantly higher in the pterygium tissue samples as compared to the control group (p < 0.001, p < 0.001, and p < 0.001, respectively). When primary and recurrent pterygium tissues were compared, bcl-2 expression was higher in recurrent pterygium tissue samples (p = 0.003). However, when Ki-67 and p53 expression levels were evaluated, no significant difference was found between primary and recurrent pterygium (p = 0.215, p = 0.321, respectively). Also, p53 and Ki-67 expression were correlated in pterygium tissue samples, and Bcl-2 expression was significantly higher in pterygium that recurrence in the first 6 months after surgery. There was no difference between groups 1, 2, and 3 in terms of p53 and Ki-67 expression.

CONCLUSION

Antiapoptotic mechanisms and proliferation play an important role in the etiopathogenesis of pterygium. Furthermore, Bcl-2 expression may be important in pterygium recurrence.

Expression and Localization of Glycosaminoglycans/Proteoglycan in Pterygium: An Immunohistochemical Study

Pterygium is a triangle-shaped fibrovascular hyperplasia of the bulbar conjunctiva on the cornea. The purpose of this study was to analyze Proteoglycans (PGs) by Immunohistochemistry (IHC) in pterygium tissues and to compare the results with normal conjunctiva. Twenty-four patients (14 males) undergoing primary pterygium excision and 17 healthy individuals (10 males), undergoing extracapsular cataract surgery, were included. Pterygium tissues and normal conjunctiva tissues were surgically removed. The tissue sections were fixed in 2% paraformaldehyde and incubated with monoclonal antibodies against PGs anti-mouse IgG. Immunohistochemical study showed stronger expression of keratan sulfate in the stroma of the pterygium compared to normal conjunctiva. An increased expression of heparan sulfate was observed in the epithelial layer and around the pterygium vessels. On the other hand, dermatan sulfate showed an increased expression and localization not only in the sub-epithelial area of the pterygium and normal conjunctiva, yet throughout the stroma of the pterygium. The differences in the expression and localization of the studied extracellular matrix proteoglycans in the pterygium tissue compared to normal conjunctiva may explain the tissue hyperplasia, structure, and the functional properties in pterygium.

K-ras oncogene mutation in pterygium

PurposePterygium is claimed to be a benign proliferation triggered by prolonged exposure to ultraviolet radiation. The frequency of K-ras oncogene mutation, which is among the initial mutations in tumorigenesis, is evaluated in this study.Patients and methodsIn this prospective randomized clinical, trial pterygium tissues and normal conjunctiva tissue specimens are obtained from the superotemporal quadrant of patients who underwent primary pterygium excision with autograft transplantation. DNA extraction from tissues was performed using the QIAamp DNA FFPE tissue kit. A PCR reaction was performed to amplify sequences containing codons 12, 13, and 61 of the K-ras gene in DNA. These PCR products then underwent the 'pyrosequencing' procedure for mutations at these codons.ResultsPterygium and normal conjunctival tissue samples of 25 patients (10 females, 15 males) were evaluated in the study. The mean age of the patients was 54.54±13.13 years. Genetic analysis revealed no K-ras mutations in normal conjunctival tissues, whereas pterygium tissues of the same cases demonstrated mutation at codon 12 in one case and mutations at codon 61 in seven cases, which was statistically significant (P<0.05). The point missense mutations at codon 61 were glutamine to arginine (Glu61Arg CAA>CGA) in four cases and glutamine to leucine (Glu61Leu CAA>CTA) in three cases.ConclusionThe significantly higher frequency of codon 61 mutation of the ras oncogene in primary and bilateral pterygium specimens compared with normal conjunctiva supports the tumoral origin of pterygium, and thus set the stage for research into a targeted therapy for pterygium with better outcomes than surgical excision.

Risk of skin cancer in patients with pterygium: a nationwide population-based cohort study in Taiwan

This study investigated the association between pterygium and skin cancer linking to ultraviolet (UV) radiation using claims data from 1997-2010, obtained from the Taiwan National Health Insurance Research Database. The study included 19,701 patients with pterygium and 78,804 sex- and age-frequency-matched comparison subjects. Multivariate Cox regression analyses were performed to assess the relationship between pterygium and risk of skin cancer by the end of 2010. The incidence rates of malignant melanoma (MM) and nonmelanoma skin cancer (NMSC) in two cohorts and adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) of the diseases were measured. Results showed that the incidences of MM and NMSC were both higher in the pterygium cohort than in the comparison cohort (5.5 vs 3.2 and 32.3 vs 15.0 per 100,000 person years, respectively). After adjusting for age, sex, UV index, occupation, and the other comorbidities, pterygium remained a significant predictor of NMSC (hazard ratio [HR], 1.64; 95% confidence interval [CI], 1.11-2.42), but not MM (HR, 1.46; 95% CI, 0.59-3.65). These results suggest that pterygium patients are associated with an increased risk of NMSC, but not significant for MM.

Immunohistochemical Profile and VEGF, TGF-β and PGE2 in Human Pterygium and Normal Conjunctiva: Experimental Study and Review of the Literature

Human pterygium is made up of chronic proliferative fibro-vascular tissue growing on the ocular surface. This disease exhibits both degenerative and hyperplastic properties. Some fibroangiogenic factors have recently been shown to play a potential role in fibrovascular diseases via the angiogenesis process. The aim of this study is to evaluate VEGF, TGF-β and PGE2 expression in the epithelial, endothelial and stromal cells of human pterygium and normal conjunctiva in order to determine whether these factors participate in the development of pterygium. Ten specimens from patients with pterygium and two normal conjunctivas (cadavers) were analyzed by immunohistochemistry using specific antibodies against these growth factors. The technique used was ABC/HRP (Avidin complexed with biotinylated peroxidase). Immunoreactivity of VEGF was significantly increased in the epithelium, vascular endothelium and stromal cells in primary pterygium as compared with normal conjunctiva. A moderate expression of TGF-β in the pterygium was observed in the epithelial and stromal layers. On the contrary, immunolabeling of this growth factor in the human normal conjunctiva was weak. PGE2 was strongly expressed in the epithelium of patients with pterygium, as in control conjunctival tissues, and the immunolabeling was moderate in the stroma from the same patients. Our results suggest that these growth factors may contribute to the progression of primary pterygium by increasing angiogenesis, thus leading to the formation of new blood vessels from the pre-existing vasculature. We conclude that VEGF, TGF-β and PGE2 may be potential therapeutic targets in the treatment of this disease although proof of this evidence requires further studies.

Expression of cell proliferation and apoptosis biomarkers in pterygia and normal conjunctiva

PURPOSE

To analyze the expression of apoptosis and cell proliferation molecules in pterygium tissues of Chinese patients.

METHODS

Thirty-three pterygia were surgically removed using the bare sclera procedure, and 23 normal bulbar conjunctivas were also obtained. Formalin-fixed, paraffin-wax-embedded tissues were analyzed by immunohistochemistry with anti- proliferating cell nuclear antigen (PCNA), K(i)-67 (a proliferating cell marker), mutant p53 (mP53), Bcl-2 associated X-protein (BAX), B-cell lymphoma gene 2 (Bcl-2), and caspase-3 antibodies. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay (TUNEL) analysis was used to analyze the apoptotic cells.

RESULTS

Our study revealed that the positive rate of PCNA and K(i)-67 significantly increased in the pterygium samples compared to the normal conjunctiva samples. In the molecules involved in apoptosis, the results showed that the positive rate of Bcl-2 and mP53 significantly increased in the pterygium samples. However, no difference was found between the pterygium and normal conjunctiva samples in the expression of Bax and caspase-3. Through TUNEL analysis, apoptotic cells were seen in the entire width of the epithelial layer in normal conjunctivas but were found mainly confined to the outer layer of the epithelial cells in pterygia.

CONCLUSIONS

The finding of high levels of cellular proliferation and low levels of cellular apoptosis in pterygia confirmed that both cell apoptosis and proliferation are known to play an important role in human pterygium pathogenesis.

Characterization and short-term culture of cells recovered from human conjunctival epithelium by minimally invasive means

PURPOSE

To characterize conjunctival cells obtained by brush cytology (BC) and establish short-term cultures.

METHODS

Human tarsal and bulbar conjunctival cells were obtained by BC and transported in 3 different media: serum-free medium (DK-SFM) with low [Ca(2+)], 10% fetal bovine serum (FBS) supplemented medium (FBSm10), and 20% FBS-supplemented medium (FBSm20). Recovered cells were counted and initial viability assessed. Flow cytometry established epithelial or immune lineage, viability, apoptosis, and cell cycle stage. To establish short-term cultures, tarsal conjunctival cells were seeded onto Permanox or denuded amniotic membrane (dAM) and cultured in the 3 media. Living adherent cells were assessed on Days 1, 2, and 5 by fluorescence microscopy.

RESULTS

Initial cell recovery was significantly lower with DK-SFM than in the other two culture media. Flow cytometry showed that 3.8+/-0.4% of recovered tarsal cells were CD45+ leukocytes and 67.9+/-1.6% were CK7+ secretory epithelial cells. S-phase cells composed 3.5+/-0.3% of the recovered tarsal cells and 2.1+/-0.2% of the bulbar cells (p=0.0006). The percentage of viable, apoptotic, and dead cells was similar for tarsal and bulbar cells. Two different cell populations were observed in both locations. About 24% consisted of smaller, less complex cells with high viability, and the remainder was composed of larger, more complex cells with poor viability. Significantly more living cells were supported by FBSm10 on the dAM substratum (p=0.011) than by the other media on either dAM or Permanox.

CONCLUSIONS

Conjunctival BC recovers proliferating cells that can be maintained on dAM in FBSm10 for up to 5 days.

Corneal and conjunctival findings after mitomycin C application in pterygium surgery: an in-vivo confocal microscopy study

PURPOSE

To perform a qualitative assessment of the topical side-effects of mitomycin C on cornea after pterygium surgery.

METHODS

In-vivo confocal microscopy (Heidelberg Retina Tomograph II in combination with the Rostock Cornea Module) was performed in 10 patients with unilateral primary pterygium. Mitomycin C 0.02% was applied topically to seven eyes for 5 min intraoperatively and twice daily for 5 days postoperatively. Three eyes underwent surgery without application of cytostatic agent. Patient follow-up was 1 month.

RESULTS

After application of mitomycin C, complete epithelialization of the operated zone was found 2 weeks after surgery. In-vivo confocal microscopy revealed signs of superficial punctate keratitis for 2 weeks in the central cornea only after application of mitomycin C. The presence of epithelial and stromal oedema in this group was noted for up to 2 weeks in the central cornea and for up to 4 weeks in the operated zone. In the control group, complete epithelialization was found after 1 week; there were no signs of oedema after 1 week in the central cornea or after 2 weeks in the operated zone. Leucocyte infiltration and increased Langerhans cell density were noted in both groups in the operated and central zones. Analysis of the conjunctiva revealed a decrease in goblet cell density following cytostatic application.

CONCLUSION

Local application of mitomycin C delays corneal epithelialization, and prolongs postoperative epithelial and stromal oedema in both the centre and periphery. Moreover, signs of punctate keratitis were noted 2 weeks after surgery in central intact cornea. Nevertheless, in-vivo confocal microscopy shows that these changes are reversible 4 weeks after application of mitomycin C 0.02%.

Angiogenesis in pterygium: study of microvessel density, vascular endothelial growth factor, and thrombospondin-1

PURPOSE

This retrospective study aims to elucidate the role of angiogenesis in the pathogenesis of pterygium. We evaluated microvessel density (MVD), and expression of vascular endothelial growth factor (VEGF) and thrombospondin-1 (TSP-1).

METHODS

Fifty-two surgically excised pterygia and seven normal conjunctivae were immunohistochemically studied applying the streptavidin-biotin method in paraffin-embedded tissue sections. Monoclonal antibodies were targeted against CD31, VEGF, and TSP-1 proteins.

RESULTS

Pterygium presented with statistically significant higher average count of microvessels compared to normal conjunctivae (17.97+/-8.5 vs5.72+/-5 per high power field, P=0.001). In 24/52 (46.2%) cases of pterygium, high expression levels for VEGF were demonstrated, whereas the mean percentage of VEGF-positive epithelial cells was 58.03%. Furthermore, normal conjunctival presented statistically significant higher expression levels for VEGF in epithelial cells (83.14+/-36.08 vs58.03+/-31.23%, P=0.007). On the contrary, the presence of VEGF immunoreactivity in vascular endothelial and stromal cells was significantly higher in pterygium tissues (P<0.0001). Stromal staining for TSP-1 was detected in only 29/52 (55.8%) of the cases and no correlation with normal conjunctivae was found. Finally, statistically significant positive correlation between MVD values and stromal VEGF expression was found (P=0.049).

CONCLUSION

The angiogenesis-related factors that were studied proved to be highly expressed in pterygium tissue. On the contrary, TSP expression level was low, allowing inducers of angiogenesis to act uninhibited. This phenomenon could provide the pathogenic basis of pterygium formation.

A randomised trial comparing 0.02% mitomycin C and limbal conjunctival autograft after excision of primary pterygium

BACKGROUND

Mitomycin C (MMC) and limbal conjunctival autograft (LCAU) are two known useful adjuvants in the prevention of pterygial recurrence. This study was conducted to compare the outcome of these two treatments.

METHODS

Prospective study on consecutive cases of primary pterygium (February 2001 to March 2002) randomised into two adjuvant groups: (1) intraoperative 0.02% MMC for 5 minutes or (2) LCAU. Patients were followed for recurrence (defined as fibrovascular tissue invading the cornea >1.5mm) and complications for a period of one year.

RESULTS

115 eyes in 114 patients who completed the study were randomised to receive MMC (n = 63) and LCAU (n = 52). There were 10 recurrences (15.9%) in the MMC group and only one recurrence (1.9%) in the LCAU group. There was a statistically significant difference in the recurrence rate between the two groups (p = 0.04). There were a total of three conjunctival cysts, three symblephara, one granuloma, and one dellen. No other visually significant complications were encountered in either group.

CONCLUSION

Although LCAU resulted in better one year success rates, it is technically more difficult and inapplicable in cases with previous limbal disturbance. Simple excision followed by MMC or LCAU are both safe and acceptable adjuvants for pterygium excision. Choice of adjuvant should be carefully made based on assessment of recurrence risk, local practices, and surgeon's expertise.

Pathogenesis of pterygia: role of cytokines, growth factors, and matrix metalloproteinases

Pterygium is a common ocular surface disease apparently only observed in humans. Chronic UV exposure is a widely accepted aetiological factor in the pathogenesis of this disease and this concept is supported by epidemiological data, ray tracing models and histopathological changes that share common features with UV damaged skin. The mechanism(s) of pterygium formation is incompletely understood. Recent data have provided evidence implicating a genetic component, anti-apoptotic mechanisms, cytokines, growth factors, extracellular matrix remodelling (through the actions of matrix metalloproteinases), immunological mechanisms and viral infections in the pathogenesis of this disease. In this review, the current knowledge on pterygium pathogenesis is summarised, highlighting recent developments. In addition, we provide novel data further demonstrating the complexity of this intriguing disease.

Primary pterygium in a 7-year-old boy: a report of a rare case and dilemma of its management

Primary pterygium in children is uncommon but is associated with severe visual problems. Astigmatism is the main visual problem caused by pterygium. Significant amounts of astigmatism occur long before a pterygium encroaches the visual axis. Early surgical intervention is safe and effective. It is associated with significant visual improvement in outcome. This is a case report on seven-year-old Malay boy who presented with a growth over nasal aspect of the right eye of 1 year duration. His right eye visual acuity is affected up to 6/12. The dilemma pased to early surgical interview is the high rate of recurrancean the young age group. This problem is highlighted in this case report.

Proliferative activity and p53 expression in primary and recurrent pterygia

PURPOSE

To assess p53 expression and proliferative activity in primary and recurrent pterygia from the same eyes.

DESIGN

Retrospective comparative human tissue study.

PARTICIPANTS

Tissue from excised primary pterygia that did not recur (group A, n = 10) was compared with tissue from primary pterygia that recurred (group B, n = 10) and to the recurrent pterygia tissue that was excised from subjects in group B (group C, n = 10). Ten normal conjunctivas served as controls (group D).

METHODS

Sections from each pterygium were immunostained with the MIB-1 and bp53. 12 monoclonal antibodies that react with Ki-67 and p53 antigens, respectively.

MAIN OUTCOME MEASURES

Proliferative activity was calculated as the mean of the MIB-1 positive cell count per eyepiece grid in high magnification (x40) (positive cell count/grid). Percentage of positive cells of all cells in the grid area was evaluated in the p53-stained sections.

RESULTS

Proliferative activity was found in the epithelium overlying the pterygia and normal conjunctiva. The mean MIB-1 positive cell count/grid +/- standard error was 2.84 +/- 1.07, 1.74 +/- 0.82, 3.83 +/- 1.35, and 0.86 +/- 0.33 in groups A, B, C, and D, respectively (P = 0.17, Kruskal-Wallis). P53 staining was found in 50% of pterygia in groups A, B, and C; none of the normal conjunctival tissues showed p53 immunoreactivity. Four of five p53-positive tissues in group B were p53-negative in group C. In the p53-positive pterygia, less than 10% of cells were p53 positive. However, p53-positive pterygia had higher mean MIB-1 positive cell count/grid +/- standard error as compared with the p53-negative lesions, 4.56 +/- 0.94 vs 1.39 +/- 0.59 (P = 0.021, Mann-Whitney).

CONCLUSIONS

p53 immunoreactivity and high proliferative activity in the epithelium overlying the pterygium are not associated with recurrence of pterygium.

Impression cytology of pterygium

The purpose of this study was to study the morphology and cytokeratin expression in the epithelia of pterygia. Impression cytology and immunohistochemical staining with antikeratin antibodies were performed in 32 eyes of 16 patients with pterygia. TUNEL stain and electron microscopy were also performed in surgical specimens ofpterygium. Squamous metaplasia-like epithelial cells were found in all specimens of impression cytology, especially in the head part. These specimens had positive immunostaining by antipancytokeratin antibodies, but not by anti-K12 AK2 mAb. Goblet cells were found around the area of these abnormal epithelial cells. TUNEL-positive cells were found in the epithelia of the pterygial head, but not in the body of pterygia and normal conjunctiva. The expressional patterns of keratin by these epithelial cells ofpterygia are consistent with the notion that they are derived from conjunctival epithelium and mimic the process of squamous metaplasia.

Epidemiology of pterygium in Victoria, Australia

AIM

To describe the prevalence of and risk factors for pterygium in a population based sample of residents of the Australian state of Victoria who were aged 40 years and older.

METHODS

The strata comprised nine randomly selected clusters from the Melbourne statistical division, 14 nursing homes randomly selected from the nursing homes within a 5 kilometre radius of the nine Melbourne clusters, and four randomly selected clusters from rural Victoria. Pterygium was measured in millimetres from the tip to the middle of the base. During an interview, people were queried about previous ocular surgery, including surgical removal of pterygium, and their lifetime exposure to sunlight.

RESULTS

5147 people participated. They ranged in age from 40 to 101 years and 2850 (55.4%) were female. Only one person in the Melbourne cohort reported previous pterygium surgery, and seven rural residents reported previous surgery; this information was unavailable for the nursing home residents. Pterygium was present upon clinical examination in 39 (1.2%) of the 3229 Melbourne residents who had the clinical examination, six (1. 7%) of the nursing home residents, and 96 (6.7%) of the rural residents. The overall weighted population rate in the population was 2.83% (95% CL 2.35, 3.31). The independent risk factors for pterygium were found to be age (OR=1.23, 95% CL=1.06, 1.44), male sex (OR=2.02, 95% CL=1.35, 3.03), rural residence (OR=5.28, 95% CL=3. 56, 7.84), and lifetime ocular sun exposure (OR=1.63, 95% CL=1.18, 2. 25). The attributable risk of sunlight and pterygium was 43.6% (95% CL=42.7, 44.6). The result was the same when ocular UV-B exposure was substituted in the model for broad band sun exposure.

CONCLUSION

Pterygium is a significant public health problem in rural areas, primarily as a result of ocular sun exposure.

Apoptosis and apoptosis related gene expression in normal conjunctiva and pterygium

BACKGROUND

Pterygium is a relatively common eye disease in the tropics whose aetiology and pathogenesis remain uncertain. As such, interest has focused on understanding the underlying mechanism of pterygia development.

METHODS

15 specimens of pterygia from 15 eyes were examined, together with normal conjunctival tissue from the same eyes for the pattern of gene expression of genes associated with the induction or repression of apoptosis (p53, bcl-2, and bax). In addition, the samples directly for apoptotic cells were examined by the terminal deoxynucleotide transferase (TdT) mediated nick end labelling (TUNEL) methodology.

RESULTS

In pterygia specimens apoptotic cells were found mainly confined to the basal layer of cells of the epithelial layer, situated immediately adjacent to the fibrovascular support layer. These cells were shown to express significant levels of p53 and bax, as well as the apoptosis inhibiting protein bcl-2. In contrast, normal conjunctival specimens displayed no bcl-2 expression and apoptotic cells were seen throughout the entire width of the epithelial layer, coupled with high levels of bax expression.

CONCLUSION

These results support a model whereby pterygia development is a result of disruption of the normal process of apoptosis occurring in the conjunctiva.

Capillaries in the epithelium of pterygium

AIM

To present new morphological observations of intraepithelial capillaries in pterygium and to provide some explanations for this phenomenon.

METHODS

The ultrastructural features of pterygia from 26 patients were examined. Surgically excised tissue was processed for conventional light and transmission electron microscopy.

RESULTS

Individual capillaries within the epithelium of the anterior half towards the head of pterygia were identified in 11 specimens out of 26 pterygia examined (42.3%). The perivascular connective tissue of the intraepithelial capillaries contained fibroblasts, collagen fibrils, and elastin-like material. Epithelial cells surrounding these capillaries showed defects in the basal lamina in contrast with the continuous basal lamina of the endothelium. In the intercellular space of the epithelium an amorphous substance, occasional fibroblast processes, and collagen fibrils were frequently observed.

CONCLUSION

Capillaries in the epithelium of pterygia are rare, but not exceptional. The ingrowth of these vessels from the stroma into the epithelium can be interpreted as a reaction to hypoxia or deficiency of any other substance transported via the bloodstream. Apparently, the perivascular connective tissue can be used by ingrowing fibroblasts as a migration pathway. The migrating fibroblasts appear to use the defects of the epithelial basal lamina (whether partially or complete) in order to reach the intercellular space. It is possible that collagen fibrils in the epithelial intercellular space have been laid down by fibroblasts which contribute to the pathological dedifferentiation of the conjunctival epithelium.