Evaluating the application of argon laser on pterygium surgery: Report of 30 patients

Abstract

BACKGROUND:

The recurrence rate plays a key role in using various treatments of pterygium. This study assessed the effectiveness of argon laser therapy before the excision of pterygium on the recurrence rate.

MATERIALS AND METHODS:

The eyes (n = 60) of patients (n = 30) were divided into two groups based on the treatment. All eyes had undergone pterygium excision with the bare sclera technique. Three weeks before surgery, an argon laser was applied to 30 eyes. Patients have been followed up for 1 year, and the progression of pterygium has been evaluated at days 1, 7, 14, and 30, and then, every 2 months until month 6 and then every 3 months until month 12. Recurrence was defined as more than 1 mm growth of pterygium from the limbus.

RESULTS:

In the group with adjuvant argon laser therapy, the mean size of pterygium was 3.7 ± 0.47 mm before surgery and 2.3 ± 0.98 after 12 months (P = 0.001). These were 3.8 ± 0.43 mm and 2.4 ± 1 mm in the other group (P = 0.001). The recurrence of the pterygium was 76% (23/30) in the group treated with an argon laser and 90% (27/30) in another group (P = 0.16). There was no correlation between pterygium sizes before surgery and the pterygium recurrence rate in both eyes (P = 0.272 [right] and 0.916 [left]).

CONCLUSION:

Argon laser therapy on pterygium before surgery cannot decrease its recurrence rate, but its application gives a good vision and clarifies the surgery's target area.

Introduction

Pterygium refers to a wedge-shaped growth of the fibrovascular conjunctiva, originating from the limbus to the surface of the cornea.[1] Pterygium is closely correlated with ultraviolet radiation, hence more frequently observed in warmer climates. Xerophthalmia, long-standing inflammation, and constant contact with debris and other irritants also contribute to the developing pterygium.[1,2,3]

Surgical intervention is the mainstay of treatment, and recurring growth of the lesion is the most challenging aspect of treating pterygium.[2,3] Throughout the years, various surgical techniques for treating pterygium have been developed. The most common methods of surgical intervention include bare sclera, amniotic membrane transplant, and conjunctival autograft surgeries.[4,5,6] One of the most significant concerns in any surgical approach is the risk of recurrence, which may result from neovascular regrowth. Among the various surgical technique, the bare sclera has a high recurrence rate (38%–88%).[6] To minimize such risk, pharmacological interventions (e.g., mitomycin, 5-fluorouracil, and anti-vascular endothelial growth factor), beta radiation, cryotherapy, or lasers have been found to be beneficial.[5,7]

Due to the role of vascular tissue on the recurrence of pterygium, preoperative ligation of the rich pterygium vascular network may also prevent recurrence through reduced hemorrhage and limiting the spread of vascular growth factors, while also decreasing the chance of anterior segment ischemia resulting from an interrupted blood flow to the anterior segment during surgeries.

Lasers have a photocoagulation effect on blood vessels. The use of lasers in pterygium removal has been tumultuous. Excimer lasers are often used as microsurgical knives and were found to increase the risk of recurrence 1 year after surgery.[8] Argon lasers utilize green-blue coherent light with a wavelength between 488 and 515 nm and are used in thermoablation methods. With the use of argon lasers, specifically low-energy argon lasers, the risk of recurrence is significantly reduced, rendering it a safe and effective tool for treating pterygium. Some studies have reported that using argon laser alone and as an adjuvant after surgery has a good outcome and decreases the recurrence rate and length of the lesion.[9,10,11,12]

As mentioned above, various surgical techniques and application methods before and after surgery, such as pharmacotherapy and radiotherapy, have been used to get the best outcome and prevent a recurrence. The high cost of some of these methods and lack of access or unavailability affects their use in the treatment, especially in low-and middle-income countries.[13] Argon laser is a safe and inexpensive method that may be effective in the treatment of pterygium. This study was designed to evaluate the impact of argon laser photocoagulation and thermal ablation effect before surgery on recurrence in patients with pterygium.

Materials and Methods

Enrollment

In this study, patients who visited to hospital between February 2012 and January 2015 with primary bilateral fleshy type of pterygium with extension toward the corneal surface were eligible for study entry. Patients between 20 and 55 years of age, with a pterygium size between 3 and 5 mm located in the nasal region, were included in the study. Those with a history of recurrent pterygium, any past surgical intervention performed on the anterior segment of the eye, the vitreous and retina, or correctional refractive surgery in the past 3 years, blepharoplasty, symblepharon phenotype, and history of chronic infectious or noninfectious diseases were excluded from the study. This study was approved by the Ethics Committee of the University. All patients were informed of the study objectives, risks, and benefits and were required to provide written informed consent upon enrollment. Participants were allowed to withdraw from the study at any phase and for any reason.

Surgical technique

In all patients, the right eye was treated with argon laser 3 weeks before pterygium removal by bare sclera technique. The feeding arteries of the pterygium were hit with a distance of 2 mm from the limbus in the form of two parallel columns, 1–2 mm apart. To achieve the ablation of vessels (made visible using a slit lamp), a power setting of 300–500 with a duration of 0.1 s and a spot size of 50 µ was used by the VALON multispot laser (Valon STA, Finland). The process was repeated 2–3 times, and patients were given dicloptin (0.1%, ophthalmic drop) and clobiotic for 6 weeks (every 6 h, 3 weeks before, and 3 weeks after surgery). The pterygium of the left eye in the patients was treated in the same surgical manner except for argon laser therapy. Both ophthalmic drops (dicloptin and clobiotic) were given in these patients for 3 weeks after surgery. The same surgeon operated on both eyes and was postoperatively blinded to the patient's group.

Follow-up

Slit-lamp biomicroscopy was used to determine the size of the pterygium before and after surgery at months 3, 6, and 12; the total area was calculated by averaging the horizontal length over the radius of the nasal cornea. Recurrence was defined as more than 1 mm growth of pterygium from the limbus.

Data gathering and analysis

Demographic and clinical data were gathered using a researcher-designed checklist. To perform statistical analysis, the SPSS software (Package for Windows version.16, SPSS Inc., Chicago, IL, USA) was used. Quantitative data have been presented as means ± standard deviation and qualitative data as frequencies and percentages. The Student's t-test was compared to quantitative data.

Results

Thirty patients (60 eyes) completed the study. The mean age of the participants was 45.7 ± 8.8 years, and the majority (n = 16; 53.3%) were female.

The mean number of lasered spots was 146 ± 23 (range: 110–200), and a mean power of 400 ± 56.8 (range: 300–500) was used. The mean size of the pterygiums of the right and left eyes was 3.7 ± 0.47 mm and 3.8 ± 0.43, respectively.

In the eyes which were preoperatively treated with argon laser therapy, the mean size of the pterygium at baseline and 12 months after surgery was 3.71 ± 0.47 mm and 2.30 ± 0.98 mm, respectively (P = 0.001). In eyes with no prior treatment, the size of the pterygium before and 12 months after surgery was 3.8 ± 0.43 mm and 2.41 ± 1 mm (P = 0.001). One month after surgery, the mean pterygium sizes of the right and left eyes were 0.16 ± 0.13 mm and 0.19 ± 0.13 mm, respectively, and were not significantly different (P = 0.054).

After 12 months of follow-up, recurrence was observed in 23 (76%) and 27 (90%) of the right and left eyes, respectively. After follow-up, the length of pterygium in the recurrent group was 2.74 ± 0.62 mm and 2.87 ± 0.72 mm in the right and left eyes, respectively. No significant relationship was observed between the preoperative lesion size with recurrence chance (P = 0.272 [right] and 0.916 [left]).

Discussion

However, various methods for treating pterygium have been improved and used in recent years, recurrence of this condition is a significant concern for ophthalmic surgeons. Corneal damage, followed by releasing growth factors, causes cell proliferation, angiogenesis, and fibroblastic migration, leading to recurrence.[2,14,15] Due to limitations such as lack of access and the high cost of new methods in treating pterygium, the bare sclera technique with an adjuvant still is used in our center. We commonly used mitomycin C intraoperatively as the adjuvant with the bare sclera technique. Considering the controversy of safety and long-term side effects of mitomycin, we were looking for an alternative. This study was designed to compare the efficacy of preoperative argon laser therapy in preventing pterygium recurrence 3 weeks before surgery. In elderly patients, the recurrence rate of pterygium decreases due to reducing the number of fibrovascular blood vessels,[13] so we excluded patients older than 55 years from the study. Our preliminary study showed that using the argon laser as an adjuvant with the bare sclera technique did not improve the recurrence rate of pterygium.

The application of lasers in the preoperative treatment of pterygium has been of interest in the last 3 decades. Seiler et al. reported that an excimer laser was found to improve postoperative vision after bare sclera pterygium removal, although it was associated with some complications.[16] Krag and Ehlers also reported that the recurrence rate was significantly high (91%) in patients who had undergone excimer laser ablation, which may also have been a complication of bare sclera pterygium removal.[8] Saifuddin and Baum followed a cohort of 42 eyes who had received postoperative argon laser treatment for 9–12 months.[12] They reported complete remission in 92.8% of the patients with first-time recurring pterygium and 64.7% with pterygia recurring more than once. They concluded that argon therapy was effective in preventing recurrence. Apaydin et al. found that treatment with argon laser therapy alone was effective in limiting lesion size, and in the patient who had undergone argon laser therapy alone, the size of the fibrovascular lesion did not exceed 1 mm after the 24-month follow-up period.[10] Na et al. recommend argon laser treatment in patients older than 50 years since recurrence rates are lower and the pterygium in these patients often retains less vasculature.[11] Abd-Elkhalak et al. also reported that using argon laser therapy before and after surgery has benefits in preventing pterygium regrowth, rendering it a safe and effective technique for improving surgical outcomes.[9]

Most of the previous studies used argon laser after surgery. In this study, we used argon laser 3 weeks before surgery to have a complete thermal ablation effect on the fibrovascular tissue of pterygium and decrease its blood supply. No adverse effects were associated with using argon laser in the treatment, and it seems safe. In our study, the recurrence rates were 76% (23/30) in the group with an adjuvant argon laser and 90% (27/30) in another group (P = 0.16). We found that using argon laser before surgery cannot prevent the recurrence of pterygium, but it gives a good surgical view and less hemorrhage for the excision of tissue and facilitates the surgery.

Conclusion

Laser argon is a safe and inexpensive method to treat various ophthalmologic conditions. Still, using it before, the removal of pterygium cannot decrease the recurrence rate of this condition.

Study limitations

It would have been better if the effect of laser ablation on vessel morphology was evaluated using anterior segment optical coherence tomography angiography or fluorescein/indocyanine green angiography, which was one of the limitations of our study.

Ethics

All patients were informed of the study objectives, risks, and benefits. Participants were allowed to withdraw from the study at any phase and for any reason. The study was in accordance with the Ethical Standards of the Committee responsible for human experimentation (Institutional and National), and with the Helsinki Declaration of 1975, as revised in 2013. Written informed consent was obtained from the patients for their anonymized information to be published in this article.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.