Rapid growth of pterygium after photorefractive keratectomy

Biomarkers in the Occurrence and Development of Pterygium

Pterygium is a kind of common conjunctival degeneration. The pathogenesis of pterygium is complex, and various biomarkers provide new targets for treatment and prognosis. Currently, the most common treatment for pterygium is surgical excision, but it is invasive risk and has a high recurrence rate. Since the development of sequencing, gene chip technology, and proteomics technologies has been rapid, research on the internal mechanism of disease has been facilitated. This review focuses on recent advances in the discovery of biomarkers from the fields of genetics, proteomics, and epigenetics and their likely functional mechanisms and clinical applications in pterygium.

Role of oxidative stress and vascular endothelial growth factor expression in pterygium pathogenesis and prevention of pterygium recurrence after surgical excision

PURPOSE

To assess the roles of oxidative stress and vascular endothelial growth factor (VEGF) in pterygium pathogenesis and prevention of pterygium recurrence after surgical excision.

METHODS

Surgically removed pterygium tissue from 35 pterygium patients and normal conjunctival samples from 15 patients matched for age and sex (used as controls) constituted the study samples. The conjunctival samples were preserved at - 80 °C until analysis. Catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH) and total antioxidant (TAO) enzymatic activity and the levels of nitric oxide (NO), malondialdehyde (MDA) and VEGF were studied in both groups. To evaluate the recurrence rate after surgical excision, the pterygium patients were further subdivided into three groups according to the adjuvant therapy used to prevent recurrence. Group 1 consisted of 10 patients who were treated with 0.2 mg mitomycin-c (MMC) for 2 min. Group 2 consisted of 12 patients treated with subconjunctival bevacizumab injection after surgical removal of the pterygium. Group 3 consisted of 13 patients who underwent combined treatment with 0.2 mg of MMC for 2 min and subconjunctival bevacizumab injection. The follow-up of patients in the three groups ranged from 7 to 15 months.

RESULTS

The activities of CAT, SOD, GSH and TAO were significantly lower in pterygium samples than in normal conjunctival samples (p < 0.0001 each). The levels of MDA (p = 0.046), NO (p < 0.0001) and VEGF (p < 0.0001) were significantly higher in pterygium patients than in controls. The lowest recurrence rate after surgical excision was that of the third group.

CONCLUSIONS

Oxidative stress and VEGF could play a role in the pathogenesis of pterygium as indicated by decreased antioxidant enzymatic activity and increased levels of VEGF in the pterygium tissue and the role of MMC and anti-VEGF therapy in decreasing the recurrence rate after surgical excision.

The expression of vascular endothelial growth factor in pterygium tissue of atopic patients

The exact pathogenesis of pterygium has not been completely elucidated. Growth factors have been considered to play a role in pterygium formation. Vascular endothelial growth factor (VEGF) is one of the principal mediators of angiogenesis, fibroblast stimulation and tissue remodeling in allergic conditions. The aim of this study was to compare the association between pterygium and VEGF gene expression between atopic and non-atopic individuals. At first visit, all patients with pterygium underwent blood tests, serum immunoglobulin E (IgE), serum cytokines including interleukin-4 (IL-4) and interferon-γ (IFN-γ) and peripheral blood eosinophil count. After obtaining informed consents, questionnaires were used to obtain demographic and clinical data from patients who underwent pterygium excision surgery. Skin prick test was performed to confirm or rule out atopy in 30 patients with (case group) and 30 patients without (control group) atopy. Pterygium tissues were then removed by surgery. A semi-quantitative reverse transcriptase polymerase chain reaction was performed to determine VEGF gene expression in all patients. Our results illustrated that VEGF mRNA expression in atopic patients was significantly higher than in the non-atopic group (P = 0.01). Eosinophil count, serum IgE and IL-4 were also significantly higher in atopic patients than in the non-atopic group (P = 0.03, 0.001 and 0.001, respectively). However, no significant difference was noted in serum IFN-γ between the two groups (P = 0.06). The excessive expression of VEGF gene in pterygium tissue of patients with atopy suggests that growth factors may play a role in the pathogenesis of pterygium or accelerate its formation.

Pterygium after hyperopic laser-assisted sub-epithelial keratomileusis (LASEK)

A 61-year-old Caucasian woman with hyperopia presented for laser refractive surgery. She had healthy eyes with the exception of a less than 0.5 mm Salzmann's nodule at 5 o'clock near the limbus of the right eye. She underwent bilateral hyperopic laser-assisted sub-epithelial keratomileusis (LASEK) combined with removal of the Salzmann's nodule. At six months, she was emmetropic with unaided vision of 6/6; however, at 10 months, she noticed a reduction of acuity in her right eye and was found to have a pterygium at 5 o'clock, encroaching 3.5 mm onto the corneal surface. She underwent excision biopsy, local application of mitomycin-C (0.2 mg/ml for two minutes) and conjunctival auto-grafting. Following surgery for the pterygium, vision returned to 6/6 unaided but six months later, there was limited recurrence (1.5 mm) of the pterygium reducing unaided vision to 6/9, due to the induction of astigmatism of -1.25 dioptres. This has remained stable for 14 months. Pterygium growth may be associated with surface excimer laser surgery and the presence of peripheral Salzmann's nodules might be a risk factor.

Surface ablation techniques

The ongoing quest for a safe, simple, effective, minimally invasive, and stable refractive surgical procedure to correct refractive errors has stimulated the development of surface ablation techniques and laser in situ keratomileusis. In this review, we describe the history, patient assessment, techniques, outcomes, and complications of surface ablation (photorefractive keratectomy, laser-assisted sub-epithelial keratectomy, epithelial laser-assisted in situ keratomileusis) and compare the results of various surface techniques. Surface ablation procedures will continue to evolve, with potential improvements in outcomes accompanying future sophisticated ablation profiles and laser technology.

[Microkeratome-assisted anterior lamellar keratoplasty for the removal of corneal scar, caused by pterygium]

AIM

to present our experience with microkeratome-assisted anterior lamellar keratoplasty using a manual microkeratome.

MATERIALS AND METHODS

left eye of a 67 year old man was operated with microkeratome-assisted lamellar keratoplasty to remove a central corneal scar of the anterior stroma and to reduce secondary high-degree irregular astigmia caused by pterygium remnant. Videokeratography was performed to record the status of the cornea.

RESULTS

postoperative best-corrected visual acuity was superior to preoperative value which was 0.6 with +7.0 spherical and -2.0 cylindrical Diopters before the operation. Uncorrected visual acuity improved from 0.15 to 0.6. The topographical cylinder decreased from 7.98 D to 3.79 D, surface asymmetry index from 2.42 to 1.48, surface regularity index form 3.24 to 1.72. Minimum keratometry reading increased from 38.35 to 41.69.

CONCLUSION

microkeratome-assisted anterior lamellar keratoplasty seems to be safe and effective to remove corneal scars and reduce high degree irregular astigmia, moreover, to improve visual acuity.