Prevalence and risk factors of pterygium: a systematic review and meta-analysis

Pattern of corneal astigmatism induced by primary pterygium in patients with cataract in a secondary hospital in Southern China: a cross-sectional study

OBJECTIVES

To review the pattern of primary pterygium-induced corneal astigmatism in patients with cataract in a southern Chinese population.

DESIGN

Clinic-based cross-sectional retrospective study.

SETTING

A secondary hospital at southern China.

PARTICIPANTS

A group of 1689 eyes with primary pterygium (PT group) and the other group of 4062 eyes without pterygium (NPT group) were included.

MAIN OUTCOME MEASURES

Corneal power was measured by an autokeratorefractometer. Corneal astigmatism was calculated as the difference in corneal power between the steepest and flattest meridians. Distribution of corneal astigmatism was compared between eyes with pterygium and eyes without pterygium.

RESULTS

Distribution of corneal astigmatism was different between PT group (skewness=2.548, kurtosis=8.237) and NPT group (skewness=2.778, kurtosis=15.52). Mean corneal astigmatism was significantly higher in the PT group (1.62±1.49D) compared with the NPT group (1.17±0.89D, p<0.0001). The prevalence of corneal astigmatism >1D (PT 52.3%, NPT 40.9%, p<0.0001), >2D (PT 22.4%, NPT 10.6%, p<0.0001) or >3D (PT 10.5%, NPT 3.2%, p<0.0001) was significantly higher in the PT group compared with the NPT group. Eyes in the PT group had significantly higher corneal astigmatism than the NPT group in almost every age group (all p<0.05), with the exception of patients ≥90 years. Moreover, eyes in the PT group had significantly higher with-the-rule (PT 1.72±1.59D, NPT 1.19±0.88D, p<0.0001) and against-the-rule (PT 1.63±1.46D, NPT 1.18±0.88D, p<0.0001) but similar oblique astigmatism (PT 1.11±1.00D, NPT 0.99±0.89D, p=0.065) corneal astigmatism compared with the NPT group. Power vector analysis indicated that the axis of corneal astigmatism was not significantly different between the two groups (J₀, PT -0.01±0.74D, NPT 0.01±0.52D, p=0.48; J₄₅, PT -0.03±0.82D, NPT 0.00±0.52D, p=0.54).

CONCLUSIONS

Pattern of corneal astigmatism in eyes with cataract and coexisting primary pterygium was different from eyes without pterygium. Pterygium is associated with higher magnitude but not different axis of corneal astigmatism.

Prevalence and Associated Factors of Pterygium Among Adults Living in Kolla Diba Town, Northwest Ethiopia

Background

Pterygium is a disfiguring disease that can potentially lead to blindness. It is more common in warm, windy and dry climates of tropical and sub-tropical regions of Africa. Globally, the prevalence ranging from 0.07% to 53%. Studies conducted on the prevalence of pterygium in developing countries were limited with a wider discrepancy between them. In this study, we aimed to assess the prevalence of pterygium and its associated factors among adults in Kolla Diba town.

Methods

A community-based cross-sectional study was done in Kolla Diba town from May 30-June 16, 2019. A systematic random sampling technique was used to select 627 study participants. The basic ophthalmic examination was performed using portable slit lamp, 3x magnifying loop with torch light and a pretested structured questionnaire was completed. The data entered into EPI INFO version 7 and analyzed using SPSS version 20. Descriptive statistics and binary logistic regression analysis were employed. P-values of <0.05 were considered statistically significant.

Results

A total of 605 study participants were involved with a response rate of 96.5%. Among them, 317 (52.4%) participants were males. The mean age of the respondents was 38.18 ± 15.56 with a range of (18–95) in years. The overall prevalence of pterygium was 112 (18.5% (95% CI (15.6–21.7)). Being widowed (AOR = 7.32 (95% CI: 2.88, 18.57)), outdoor occupation (AOR = 2.50 (95% CI: 1.46, 4.29)), sun exposure (AOR = 2.38 (95% CI: 1.28, 4.43)), wind exposure (AOR = 1.97 (95% CI: 1.04, 3.72)), alcohol drinking (AOR = 2.26 (95% CI: 1.48, 4.63)), and severe blepharitis (AOR = 2.45 (95% CI: 1.48, 4.05)) had statistically significant positive association with pterygium.

Conclusion

The prevalence of pterygium was relatively higher. Being widowed, outdoor occupation, sun exposure, wind exposure, alcohol drinking, and severe blepharitis were significantly associated with the development of pterygium.

A surgical skills assessment rubric for pterygium surgery

PURPOSE

To introduce an assessment tool (rubric) for evaluating ophthalmology residents' competency in pterygium surgery.

METHODS

A panel of experienced international surgeons collaborated and developed the rubric. After describing various stages of the procedure, the Dreyfus scale of skill acquisition was used for scoring each stage. After finalizing the rubric, two surgeons independently evaluated 20 masked pterygium surgery videos of 10 residents and scored the videos according to the rubric. The agreement between the scores of them was examined with the intra-class correlation coefficient test.

RESULTS

This rubric divides pterygium surgery into 13 different stages and covers the two most common techniques of pterygium surgery; conjunctival autograft and amniotic membrane transplant. The rubric showed face and content validity. Overall, an intraclass correlation coefficient of 0.90 (95% confidence interval 0.76-0.96, P < 0.001) was achieved between the two surgeons. The residents scored significantly higher on surgeries performed later in their rotation compared to the earlier surgeries (4.32 ± 0.35 vs 3.96 ± 0.31, P = 0.006). Certain stages of pterygium surgery were more strongly correlated with the residents' past pterygium surgical experience.

CONCLUSION

This study introduces an international rubric for assessing competency in pterygium surgery. In addition to face and content validity, this rubric shows high inter-rater reliability. This may be a useful tool for teaching and measuring competency in pterygium surgery.

Clinical profile of pterygium in patients seeking eye care in India: electronic medical records-driven big data analytics report III

OBJECTIVE

To describe the clinical profile of pterygium in patients presenting to a multi-tier ophthalmology hospital network in India.

METHODS

This cross-sectional hospital-based study included 1,610,843 new patients presenting between 2010 and 2019. Patients with a clinical diagnosis of pterygium in at least one eye were included as cases. The data were collected using an electronic medical record system. Multiple logistic regression analysis with odds ratios (OR) was performed to identify the associated risk factors.

RESULTS

Overall, 168,807 (10.5%) new patients were diagnosed with pterygium, of which 43,692 (26%) patients complained about the lesion. The prevalence rates were 0.7% in children and 12.6% in adults. Majority of patients were female (54.5%) and had unilateral (57%) affliction. Among the 241,631 affected eyes, the pterygia were primary in 99.6%, nasally located in 94%, and were grade I-II in 84.8%. Four in 5 eyes did not have any cylindrical refractive error, and 44% had coexistent cataract. Pterygium surgery was indicated in 10.3% eyes. Female sex (OR 1.37), increasing age (OR 19.5), rural residence (OR 1.21), agriculture work (OR 2.19), manual labor (OR 2.05), low socioeconomic status (OR 2.14) and geographical location closer to the equator (OR 3.4) were identified as the risk factors for developing pterygium.

CONCLUSION

About one-tenth of individuals seeking eye care in India have pterygium in at least one eye. It rarely impacts vision, is commonly unilateral and nasal and usually does not require surgery. It is associated with increasing age, females, outdoor work, low income and geographical location closer to the equator.

Femtosecond Laser-assisted Preparation of Conjunctival Autograft for Pterygium Surgery

Femtosecond laser-assisted conjunctival autografts (CAG) preparation was recently proposed. This study reports the outcomes of the first clinical trial on the use of laser to prepare CAG in pterygium surgery, and to compare the outcomes with those of manual technique. Forty eyes undergoing primary pterygium excision with laser-assisted CAG transplantation were prospectively included (L group). Two historical matched cohorts whose CAGs were prepared manually were compared (n = 78 eyes by the same experienced surgeon, M group; n = 78 eyes by trainees; TM group). We found the laser-created CAGs had only 11 μm deviation from the targeted thickness. The best-corrected visual acuity improved, and the astigmatism significantly decreased after surgery, with comparable efficacy across 3 groups. The 1-year recurrence rate was 2.5%, 3.8% and 7.7% in the L, M and TM groups, respectively (P = 0.12). There was no significant difference between the L and M groups in the complication rate (5.0% and 1.3%, respectively), surgical time (19.4 ± 5.1 and 19.1 ± 6.2 minutes, respectively), and postoperative discomfort scores (0.1 ± 0.3 and 0.2 ± 0.3, respectively), but these outcomes were significantly less favorable in the TM group. The results of this first comparative clinical trial suggest that femtosecond laser-assisted CAG preparation can be considered as an alternative technique for CAGs preparation.

Prevalence and associated factors for pterygium in Han and Mongolian adults: a cross-sectional study in inner Mongolian, China

Background

To investigate the prevalence of pterygium and associated factors in Han and Mongolian adults at four survey sites in Inner Mongolia, China.

Methods

We conducted a population-based, cross-sectional study as part of the China National Health Survey (CNHS). By means of a stratified sampling method, we finally included 2651 participants of 30 years of age or older from a total of 3468 eligible residents. Factors associated with pterygium were analysed by a univariate analysis and logistic regression models.

Results

The study population included 1910 Han and 741 Mongolian adults. The mean age ± standard deviation of the study cohort was 48.93 ± 11.06 years. The overall prevalence of pterygium was 6.4% (n = 169); 1.4% (n = 38) of the cases were bilateral and 4.8% (n = 128) were unilateral. The most common grade of pterygium was Grade 2. Based on the results of the univariate analysis, eleven factors were included in a multivariate analysis. The results indicated that age (P < 0.001), outdoor occupation (P = 0.026), and time spent in rural areas (P < 0.001) were significantly associated with pterygium. Sex and ethnicity were not identified as risk factors.

Conclusions

Our results indicated that outdoor occupation, old age and more time spent in rural areas were risk factors for pterygium in Inner Mongolia. At the same time, town as a survey site (Hohhot and Tsining District) was a protective factor for pterygium. Ethnicity, gender, smoking, diabetes and high blood pressure are not associated with pterygium.

Clinical Role of Epigenetics and Network Analysis in Eye Diseases: A Translational Science Review

Network medicine is a molecular-bioinformatic approach analyzing gene-gene interactions that can perturb the human interactome. This review focuses on epigenetic changes involved in several ocular diseases, such as DNA methylation, histone and nonhistone post-translational modifications, and noncoding RNA regulators. Although changes in aberrant DNA methylation play a major role in the pathogenesis of most ocular diseases, histone modifications are seldom investigated. Hypermethylation in TGM-2 and hypomethylation in MMP-2/CD24 promoter genes may play a crucial role in pterygium development; hypermethylation in regulatory regions of GSTP1 and OGG1 genes appear to be diagnostic biomarkers of cataract; hypomethylation of TGF-β1 promoter may trigger glaucoma onset; hypermethylation of the LOXL1 gene might be associated with pseudoexfoliation syndrome. A large panel of upregulated micro-RNAs (miRNAs), including hsa-hsa-miR-494, hsa-let-7e, hsa-miR-513-1, hsa-miR-513-2, hsa-miR-518c, hsa-miR-129-1, hsa-miR-129-2, hsa-miR-198, hsa-miR-492, hsa-miR-498, hsa-miR-320, hsa-miR-503, and hsa-miR-373, ^∗ may have a putative role in the development of retinoblastoma. Hypermethylation of H3K4 and hypomethylation of H3K27 at the TGFBIp locus are putative pathogenic mechanisms involved in corneal dystrophies. Determining how, where, and when specific epigenetic changes trigger ocular diseases may provide useful clinical biomarkers for their prevention, diagnosis, and management, as well as innovative drug targets. PF-04523655, a 19-nucleotide methylated double-stranded siRNA targeting the RTP80 gene, showed a dose-related improvement in best-corrected visual acuity (BCVA) in patients affected by diabetic macular edema. The observed results support a clinical network-based research program aimed to clarify the role of epigenetic regulators in the development of ocular diseases and personalized therapy.

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.

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.

Impact of pterygium on the ocular surface and meibomian glands

PURPOSE

To analyze how ocular surface parameters correlate to presence of pterygium and investigate the possible impact of pterygia on tear film findings and meibomian glands findings.

METHODS

We investigated objective parameters of the ocular surface such as conjunctival hyperemia, tear film stability and volume, meibomian gland dysfunction, dry eye disease, corneal topography comparing healthy individuals and correlating with the pterygium clinical presentation.

RESULTS

A total of 83 patients were included. Corneal astigmatism induction was 2.65 ± 2.52 D (0.4-11.8). The impact of pterygium on the ocular surface parameters compared to matched controls was seen in: conjunctival hyperemia (control 1.55±0.39/pterygium 2.14±0.69; p = 0.0001), tear meniscus height (control 0.24±0.05 mm/pterygium 0.36±0.14mm; p 0.0002), meiboscore lower eyelid (control 0.29±0.64/pterygium 1.38±0.95; p 0.0001) and meiboscore upper eyelid (control 0.53±0.62/pterygium 0.98±0.75; p = 0.0083). We found a high number of pterygium patients (88%) presented meibomian gland alterations. Interestingly, meibomian gland loss was coincident to the localization of the pterygium in 54% of the upper and 77% lower lids.

CONCLUSION

Pterygium greatly impacts on ocular surface by inducing direct alterations in the pattern of meibomian glands besides corneal irregularities, conjunctival hyperemia and lacrimal film alterations, inducing significant symptoms and potential signs of dysfunction.

Targeting platelet-derived growth factor receptor β inhibits the proliferation and motility of human pterygial fibroblasts

Background: Pterygium, a common eye disease with high postoperative recurrence, lacks effective therapeutic strategies. Therefore, it's urgent to identify specific targets to develop rationally targeted molecular drugs for the pterygial therapy. Methods: The cell proliferation and motility were studied in both the primary human pterygial fibroblasts (hPFs) and an ex vivo pterygium model. hPFs transfected with the pCMV3-PDGFRB plasmid, PDGFRB siRNA and CRISPR/Cas9 system were used to determine the role of PDGFR-β in pterygial fibroblasts functions. Western blotting, immunohistochemistry and immunofluorescence were performed to evaluate the expression of the key proteins. Results: PDGFR-β expression in the pterygial stroma and primary hPFs was significantly higher than that in the conjunctiva and human conjunctival fibroblasts. PDGF-BB promoted the proliferation, migration and invasion of hPFs, which can be significantly suppressed by sunitinib via inhibition of the PDGFR-β/extracellular signal-regulated kinase (ERK) pathway. In the ex vivo model, the knockout of PDGFRB and sunitinib treatment blocked the proliferation and motility of fibroblasts in the pterygial stroma via the suppression of PDGFR-β/ERK pathway. Conclusion: This study demonstrates that PDGFR-β may be a potential therapeutic target for pterygium, and inhibition of PDGFR-β by sunitinib is a promising and effective approach for pterygium treatment.

Head inversion technique to restore physiological conjunctival structure for surgical treatment of primary pterygium

We describe a new surgical technique to treat primary pterygium, the head inversion technique, with its surgical outcomes. Seventy-five eyes of 75 consecutive patients with primary pterygium undergoing surgical treatment were included. The pterygium head and body were bluntly separated from the cornea and inverted onto the nasal conjunctival area. By injecting a balanced salt solution subconjunctivally, the conjunctiva was ballooned and smoothed. Two or three interrupted 8–0 virgin silk sutures were placed to secure the inverted conjunctiva in place. No adjunctive therapy was used during and after surgery. Postoperatively, one eye showed pterygium recurrence at 233 days, in which an unintended conjunctival hole was made during surgery. The Kaplan-Meier analysis showed that the recurrence rate at 1 year was 2.4%. In 43 eyes which were followed up for longer than 6 months, the vascular loop, which is characteristic of normal limbal structure, appeared on the nasal conjunctiva in 41 eyes (95.3%). The palisades of Vogt were found on the nasal limbus postoperatively in 13 eyes (30.2%). The pterygium head inversion technique was an effective treatment for primary pterygium. By separating the pterygium from the cornea and inverting the intact pterygium head onto the nasal conjunctival site, the conjunctiva restored near physiological status after surgery.

Evaluation of Autologous Blood in Pterygium Surgery With Conjunctival Autograft

PURPOSE

Autologous blood has been used exploratively with conjunctival autograft in pterygium surgery. However, it is controversial whether autologous blood performed better than other fixation methods, including fibrin glue and sutures. This meta-analysis was conducted to evaluate the effectiveness of using autologous blood in pterygium surgery with conjunctival autograft.

METHODS

The study was conducted according to the PRISMA guidelines. The MEDLINE, Cochrane library, and Embase databases were systematically searched from their establishment until April 1, 2018. Randomized controlled trials comparing autologous blood with fibrin glue/suture in pterygium surgery with conjunctival autograft were included. The methodological quality of the included studies was assessed using the Cochrane risk of bias tool. Outcome measurements were recurrence, graft displacement, graft retraction, and surgical duration. Review Manager 5.3 (Cochrane Community, Cochrane Collaboration, London, UK) was used to perform the statistical analysis. When I < 50%, statistical heterogeneity was considered acceptable, and a fixed-effects model was adopted; alternatively, the random-effects model was used.

RESULTS

Seven randomized controlled trials including 516 patients were finally included in the meta-analysis. Four studies with 379 patients compared autologous blood and fibrin glue. Autologous blood was inferior to fibrin glue with respect to surgical duration, graft retraction, and graft displacement. However, there was no statistical difference between the 2 groups in terms of the recurrence rate. Four studies with 152 patients compared autologous blood and traditional suturing. Autologous blood was superior to sutures in terms of surgical duration and inferior to sutures in terms of graft retraction. No difference was detected in terms of graft displacement and recurrence rate.

CONCLUSIONS

In conclusion, autologous blood is an appropriate method for graft fixation in pterygium surgery. Current research suggests that autologous blood derivatives may be a promising approach after pterygium excision. However, this requires further confirmation.

Ocular Exposure to Particulate Matter and Development of Pterygium: A Case-Control Study

Background:

Formation of pterygium has been mainly attributed to exposure to the ultraviolet (UV) radiation. Other factors such as dry weather, wind exposure and microtrauma with dust particles, have been linked to development of pterygium.

Objective:

To determine the association between ocular exposure to particulate matter and development of pterygium.

Methods:

This case-control study was conducted in a company dedicated to the production and marketing of toilets. We included a total of 90 cases identified in November 2013 and 184 controls. The diagnosis of pterygium was based on clinical examination. Variables studied included age and job tenure of the participants. Logistic regression analysis was used to assess the effect of exposure on developing pterygium.

Results:

All study participants were male. The mean age of the cases and controls was 39.9 (SD 9.5) and 37.8 (SD 7.3) years, respectively. 115 (42%) of the participants had a job tenure of 5–8 years. The percentages of cases and controls exposed to particulate matter were 31.1% (n=28) and 30.4% (n=56), respectively (OR 1.08, 95% CI 0.61 to 1.91).

Conclusion:

We could not observe any association between ocular exposure to particulate matter and development of pterygium.