Lasers in Medical Science

, Volume 31, Issue 5, pp 1037–1039 | Cite as

Efficacy of Pattern Scan Laser photocoagulation for superficial conjunctival nevi ablation

Brief Report

Abstract

This study reports the efficacy and safety of Pattern Scan Laser (PASCAL) photocoagulation in the removal of superficial conjunctival nevi. Superficial conjunctival nevi were removed from 10 eyes of 10 patients using PASCAL. The laser spots were 200 μm in size, and the power delivered ranged from 250 to 300 mW. The duration of the laser pulse was kept at the minimum needed for adequate lesion removal. The duration of the laser pulse administered to the patients varied from 100 to 200 ms. Complete removal of the conjunctival nevus was observed in all the patients after PASCAL photocoagulation. Six months after treatment, complete re-epithelialization of the overlying conjunctiva was noted. No signs of recurrence or scarring were found in any of the patients during the follow-up period. Pure thermal denaturation is the main mechanism of PASCAL photocoagulation for removal of superficial conjunctival nevi. PASCAL can be considered as an alternative to conventional argon laser treatment or surgery.

Keywords

Conjunctival nevi Laser PASCAL Pattern Scan Laser Thermal denaturation 

Introduction

Benign conjunctival melanocytic lesions are usually classified into two categories: superficial nevi and deep vascularized thickened nevi [1, 2]. Acquired superficial conjunctival nevi generally become clinically apparent in the first or second decade of life and rarely develop into malignant melanomas. However, acquired conjunctival nevi with nodularity, a high degree of pigmentation, or vascularized formation can develop into malignant melanomas. Treatment options for superficial and deep conjunctival nevi include surgical excision or argon laser photocoagulation [2]. Especially in cases of superficial flat nevi, most patients undergo removal using laser treatment to correct cosmetic problems.

Due to the many advantages of Pattern Scan Laser (PASCAL; Topcon Medical Laser Systems, Santa Clara, CA, USA), including safety, effectiveness, and less pain due to shorter exposure times, this treatment is now being substituted for the conventional argon laser photocoagulation for macular photocoagulation and pan-retinal photocoagulation in many clinics [3, 4].

To date, there has been limited research on the use of PASCAL for ocular surface diseases. Our study assessed the efficacy and safety of PASCAL in the treatment of superficial conjunctival nevi.

Materials and methods

In this study, superficial conjunctival nevi were removed from 10 eyes of 10 patients using PASCAL. Laser photocoagulation was performed for superficial conjunctival nevi meeting the inclusion criteria suggested by Shin et al. [2]. Table 1 shows the patient characteristics and preoperative data. Participating patients had no other significant medical histories. The study adhered to the tenets of the Declaration of Helsinki, and written informed consent was obtained from all patients.
Table 1

Patient characteristics and preoperative data

Case no.

Sex

Age

Laterality

Conjunctival site

Size (mm)

Laser setting (spot size/power/duration) (μm/mW/ms)

1

M

19

Left

Bulbar

2 × 3

200/250/200

2

F

33

Left

Bulbar

5 × 6

200/250/100

3

F

23

Right

Bulbar

2 × 3

200/250/200

4

M

24

Right

Bulbar

3 × 2

200/250/100

5

F

23

Right

Bulbar

2 × 3

200/250/150

6

F

21

Right

Bulbar

2 × 2.5

200/250/100

7

F

21

Left

Bulbar

2 × 4

200/300/200

8

F

32

Left

Bulbar

3 × 3

200/250/200

9

F

32

Left

Bulbar

3 × 3

200/250/100

10

F

34

Left

Bulbar

1.5 × 3

200/300/100

We used PASCAL, a 532-nm frequency-doubled Nd:YAG laser for superficial conjunctival nevi removal. After administration of 0.5 % proparacaine hydrochloride, the laser was focused directly on an area of conjunctival nevi. The laser spots were 200 μm in size and we tried not to overlap them. The power delivered ranged from 250 to 300 mW. The duration of the laser pulse was kept as short as possible, compatible with efficient lesion removal, actually 100 to 200 ms. The patients were instructed to use prednisolone acetate 1 % (Pred Forte, Allergan, Irvine, CA, USA) and sodium hyaluronate 0.1 % (Kynex, Alcon, Seoul, Korea) four times a day for 1 week. They were followed-up at 1 week and at 6 months after treatment.

Results

During the laser procedure, the patients experienced bearable pain that was not severe enough to halt the procedure. As the laser spot size (200 μm) and the power (250 to 300 mW) were fixed, the only variable parameter was laser duration. A laser pulse duration less than 100 ms was not effective enough for lesion removal. To complete removal of superficial conjunctival nevi, all the patients received laser pulse treatment for durations over 100 ms (100 to 200 ms). After the PASCAL photocoagulation, complete removal of the conjunctival nevus was achieved in all the patients. Complete re-epithelialization of the overlying conjunctiva was noted at postoperative month 6 (Figs. 1 and 2). No sign of recurrence or scarring was found in any of the patients during the follow-up period.
Fig. 1

Outcome of Pattern Scan Laser ablation of a superficial conjunctival nevus (case 1). a Preoperative appearance of a superficial conjunctival nevus at the temporal bulbar conjunctiva (2 × 3 mm). b Slit lamp biomicroscopic image showing complete lesion removal at postoperative month 6 after the Pattern Scan Laser procedure

Fig. 2

Outcome of Pattern Scan Laser ablation of a superficial conjunctival nevus (case 2). a The preoperative appearance of a superficial conjunctival nevus at the temporal bulbar conjunctiva (5 × 6 mm). b Slit lamp biomicroscopic image showing complete lesion removal at postoperative month 6 after the Pattern Scan Laser procedure

Discussion

Serial observation is usually sufficient to monitor benign conjunctival melanocytic lesions [5]. However, some patients undergo lesion removal for cosmetic reasons.

Recently, laser treatment has replaced surgery for treating ocular surface diseases, including pinguecula or conjunctival nevus [2, 6]. The main reason for this change is that surgery is associated with potential complications such as infection, scarring, diplopia, and, rarely, loss of vision. Our study showed PASCAL is an effective and safe treatment for the removal of superficial conjunctival nevi, and can be used as an alternative for conventional argon laser treatment or surgery.

Reduced pulse duration is the main advantage of PASCAL treatment compared to conventional long pulse duration laser treatment. Reduction in pulse duration enhances the predictability of the lesion size and reduces collateral injury through reduced axial and lateral spread of heat. Reduced penetration of heat has the potential to decrease ocular pain during the procedure. Except for pulse duration, the laser settings we used were based on a previous study that used a conventional long pulse duration laser [2]. We tried to reduce the laser pulse duration to emphasize the advantage of PASCAL. However, as mentioned earlier, lesion removal was impossible with a laser pulse duration of less than 100 ms. Some of the early studies on laser treatment showed that with pulse durations longer than 10–50 ms, pure thermal denaturation of tissue, rather than thermo-mechanical cavitation, is the primary mechanism of action [7, 8]. As we used laser pulses of durations over 100 ms in this study, the primary mechanism of superficial conjunctival nevi removal with PASCAL is presumably pure thermal denaturation rather than thermo-mechanical cavitation.

Larger spot size, higher power, and longer duration of argon laser photocoagulation tend to cause more ocular complications such as ciliary body and choroidal detachment [9], subretinal neovascularization [10], and ocular inflammation [11]. Trying not to induce such ocular complications, we tried to avoid the high-energy laser settings of previously mentioned cases [9, 10, 11]. Under this safety standard, we tried to figure out the minimum duration of PASCAL. Although we obtained the good efficacy of PASCAL laser on conjunctival nevi removal, further studies should consider various combinations of laser settings.

However, PASCAL photocoagulation to treat superficial nevi has several limitations including lack of histopathological confirmation of tissue that may have malignant potential. Long-term clinical follow-up with histopathological confirmation after lesion removal may be necessary to verify the safety of PASCAL photocoagulation for superficial nevus treatment.

Conclusions

In conclusion, the main mechanism of PASCAL photocoagulation in the removal of superficial conjunctival nevi is pure thermal denaturation. PASCAL can be considered a safe and effective treatment option for superficial nevi, minimizing patient discomfort and maximizing cosmetic effect and patient satisfaction.

Notes

Acknowledgments

This work was supported by the year 2015 clinical research grant from Yangsan Pusan National University Hospital.

Compliance with ethical standards

The study adhered to the tenets of the Declaration of Helsinki, and written informed consent was obtained from all patients.

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Copyright information

© Springer-Verlag London 2016

Authors and Affiliations

  1. 1.Department of Ophthalmology, Pusan National University School of Medicine and Medical Research InstituteYangsan Pusan National University HospitalYangsanSouth Korea
  2. 2.Department of Ophthalmology, Gyeongsang National University School of MedicineGyeongsang National University Changwon HospitalChangwon-siSouth Korea
  3. 3.Department of Ophthalmology, School of Medicine, Pusan National University and Medical Research InstitutePusan National University HospitalPusanSouth Korea

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