Efficacy of Mitomycin C in Pterygium Management

Mohammad Droos, MD (Oph)

Correspondence:
AL-DROOS, MD.
Ophthalmology Department, Royal medical services,
Amman, Jordan;
droos75@hotmail.comE-mail
Tel: 00962-777265101

INTRODUCTION

A pterygium is an abnormal (non-cancerous) growth of the conjunctiva; a triangular fibrovascular sub-epithelial ingrowth of degenerative bulbar conjunctival tissue over the limbal onto the cornea⁽¹⁾. The conjunctiva is a thin membrane lining the inside of the eyelid and part of the eyeball (located between the sclera, or the "white of the eye") which surrounds the eyeball.

Excessive growth of the conjunctiva leads to a pterygium, which appears as a fleshy spot. Pterygia are nearly always preceded and accompanied by pingueculae⁽²⁾.
The exact cause of pterygium is unknown. The most common factors that contribute to pterygium include:

Excessive exposure to sunlight
Sex: Male
Increasing age
Working outdoors
Excessive exposure to harsh environmental conditions such as dust, dirt, heat, wind, dryness, and smoke
Excessive exposure to allergens such as industrial solvents and chemicals.

The symptoms of pterygia include the following: redness, irritation, tearing, foreign body sensation, dryness, sometime blurring of vision especially when it causes corneal astigmatism⁽¹¹⁾.

Management of pterygium can be divided into

Observation:

• Periodic eye examination, usually when the pterygium causes no or minimal symptoms
  
• If symptoms increase, additional treatments may include:
  - Medications: prescription antibiotics to prevent infection; corticosteroids to reduce inflammation; ocular lubricants
  - Radiation therapy to stop pterygium cells from reforming⁽⁷⁾.
  - Mitomycin C to aid in healing and prevent recurrence⁽⁸⁾.
  

Surgery
Indications for pterygium excision include⁽¹²⁾: persistent discomfort, vision distortion, and restricted ocular motility. Microsurgical excision of a pterygium aims to achieve a normal, topographically smooth ocular surface⁽³⁾.

Mitomycin (Mitomycin C; MMC) is an antibiotic isolated from Streptomyces caespitosus. The drug is a bioreductive alkylating agent that undergoes metabolic reductive activation, and has various oxygen tension-dependent cytotoxic effects on cells, including the cross-linking of DNA. It is widely used systemically for the treatment of malignancies, and has gained popularity as topical adjunctive therapy in ocular and adnexal surgery over the past 2 decades⁽⁶⁾. Its use has been described in the management of ocular surface neoplasias⁽⁴⁾, conjunctival malignant melanoma and primary acquired melanosis with atypia⁽⁵⁾, and in conjunctival intraepithelial neoplasia⁽¹⁰⁾.

Complications of topical Mitomycin C have been described in the litreture and include the following: scleral necrosis and thinning, perforation, endophthalmitis, endothelial decompensation, glaucoma, and iritis⁽⁹⁾.

MATERIALS AND METHODS

A retrospective study of 37 eyes (30 patients), with the mean age of 43 years (30 -55) years attending the ophthalmology clinic.

We divided the patients into two main groups; in the first group we use Mitomycin C, and in the second we only excised the pterygium.

17 eyes (17 patients) were treated by using Mitomycin C; 14 eyes had primary pterygia and 3 eyes with recurrent pterygia. 20 eyes (13 patients) were treated without the use of Mitomycin C; 15 eyes had primary pterygia and 5 eyes had recurrent pterygia. All eyes received the same medications postoperatively.

The examination included:

• Visual Acuity-a test to measure the patient's ability to see and read the smallest letters on an eye chart (by using Topcon chart projector (vision tester VT-SE; Topcon Co, Japan) with E letters at a distance of 6 meters.
  
• Slit Lamp Examination-a bright light with magnification used to view the eye.
  
• Photo Documentation-Photography to record the degree of growth of a pterygium.
  

The cornea and conjunctiva were examined by using binocular slit lamp microscope with magnification, and we chose the patient who had pterygium indicated for surgical excision (a condition that causes one of these; visual impairment, persistent discomfort, and restriction of ocular motility).

We excluded from this study; pingueculae, simple pterygia that cause no or minimal symptoms.

In this study we applied 0.4 mg/ml Mitomycin C intra-operatively for 3 minutes following pterygium excision.



RESULTS

Of the 37 eyes (30 patients); had Mitomycin C treated eyes (17 eyes). We noted that only 2 eyes (11.7% ) had recurrent pterygia, after 14 months follow-up (see Table 1), but the recurrence in the non-Mitomycin C group (20 eyes) was higher than that of the Mitomycin group 9 eyes (45%) after the same period of follow-up (see Table 2). Also we noted that the healing of conjunctiva was delayed when we use Mitomycin C in comparison to the other group; which is a known side effect of Mitomycin C; and it is not a significant complication because we use it in a minimal dose for a short period of time.

The postoperative recurrent pterygia in the Mitomycin C group were not from the primary pterygia, but only from the recurrent pterygia (preoperative). The recurrent pterygia in the non-Mitomycin C group were from both primary and recurrent pterygia.

Table 1. Recurrent rate in Mitomycin Group

Table 2. Recurrent rate in Nonmitomycin Group

DISCUSSION

Pterygium is a common disorder affecting conjunctiva and cornea especially in hot and dry environmental areas. It is insignificant when it is simple and not causing discomfort to the patient and does not need aggressive management except observation and some medications such as antibiotics to prevent the infections; corticosteroids to reduce inflammation; and ocular lubricants.

Pterygium is significant when it causes patients discomfort (persistent), visual impairment, and restriction of ocular motility. These are indications for excision of pterygium which can be either excision alone or excision along with adjunctive therapy such as Mitomycin C, 5 fluorouracil, etc.

The former has had a high recurrence rate which is annoying for the patient.

In this study we use Mitomycin C intra-operative with the excision , and we follow-up these patients, with good results. Recurrence of pterygia was decreased and there were minimal complications. From these results we recommend the use of Mitomycin C in pterygium management because it is a simple, safe, and successful procedure.

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