Pterygium is a common disease of the eye and has been described in medical and surgical texts since as long back as 1000 BC. 1 The word “pterygium” stems from the Greek word “pterygos,” which means “wing” (plural: pterygia), and is an accurate description of its appearance. The pterygium has been defined as a triangular, wing-shaped, degenerative, fibrovascular, hyperplastic proliferative tissue actively growing from the conjunctival limbal area onto the cornea. 2 It is an external, superficial, elevated ocular mass that forms over the perilimbal conjunctiva and extends onto the corneal surface. It continues to grow to cover the center of the cornea, usually from the nasal side, but may come from the temporal side or rarely from both.
The incidence of pterygium has been directly linked to proximity to the equator. The latitudes between 37 degree north and south of the equator were referred to as the “pterygium belt” by Cameron. 3 Increasing age, ultraviolet (UV) radiation, chronic irritation, and genetic predisposition are the other risk factors.
The exact cause or mechanism of pterygium formation is still unknown. They are thought to be a degenerative process caused by sun exposure and show altered collagen fibers with elastic stains, classically described as “elastotic degeneration.” 4 Newer studies hint toward pterygium being a localized, interpalpebral, limbal stem cell deficiency due to exposure to UV radiation. 5
The first description of pterygium and the surgical procedure to treat it was given by Sushruta, probably the world’s first surgeon ophthalmologist, who lived in India around 1000 BC. Since then, there have been many descriptions by Celsus (29 AD), Vagblat and Paul (600 AD), Rhazes (932 AD), Avicenna (1037 AD), and Chakradatta (1060 AD). 6
Since the beginning, the preferred mode of treatment was surgical, although many medical treatments have also been tried.
The ancient Egyptians used “collyria” of pastes of honey, excrement of lizard or pelican, incense, or antimony to treat many eye diseases including pterygia. 7 Hippocrates (V–IV centuries BC) mentioned collyria of zinc, copper, iron, bile, urine, and mother’s milk. 8 Centuries later, Bartisch 9 and Sennert 10 recommended a mixture of sugar, bloodstone (hematite powder), alum, white vitriol, camphor, and wine tartar. A classical treatment was Divine Stone (lapis divinus, also called lapis ophthalmicus), which was a mixture of potassium nitrate, alum, blue vitriol, and camphor dissolved in water. 11
The oldest preserved surgical description, that of Sushruta, describes the surgery as follows (▶ Fig. 1.1):
“The patient must lie on a table. The pterygium is sprinkled with salt. The patient looks laterally, and the most superficial part of the pterygium is clasped with a hook. Then, the pterygium is detached from the ocular surface with a knife with a round end but sharp cutting edge. The remnants adhered to the eye must be eliminated, and an unguent applied, in order to avoid the recurrence.” 12
Celsus used a thread under the pterygium instead of a hook and cut the detached pterygium with a scalpel. He then placed a cloth soaked in honey on the surface. 13 The centuries that followed saw many of the surgeons using their own modifications of this technique.
Fig. 1.1 Depiction of Sushruta during his surgeries. (Reproduced with permission from Dr. Babu Thushar.)
Modern approach to treatment includes using ocular lubricants to treat dry eye during the early stages of the disease. Surgical treatment is conventionally indicated when the lesion is large, threatens vision, causes significant discomfort, or is cosmetically unacceptable. Surgical methods include a wide range of procedures from the simple bare sclera technique to the more complex lamellar keratoplasty and amniotic membrane transplantation. All these techniques aim to minimize recurrence, which is the biggest problem encountered in treating pterygia.
The current surgical approaches can broadly be divided into the following 14:
Bare sclera excision.
Excision with conjunctival closure.
Excision with antimitotic adjunctive therapies.
Ocular surface transplantation techniques.
The bare sclera technique, which was first described by D’Ombrain in 1948, 15 is now out of favor due to the high incidence of recurrence. 16 Excision with a simple conjunctival closure is popularly performed in developing countries. It includes a range of techniques like simple approximation of the conjunctival edges to superior rotational flap transposition. This reduces the recurrence. 17 There is widespread acceptance of conjunctival autografting, since it was introduced by Thoft (1977) and was applied to pterygium surgery by Vastine et al and Kenyon et al. 18 Most techniques advocate using an adequately sized thin graft devoid of Tenon’s fascia to cover the bare sclera. Closure can be achieved by either sutures or adhesives. Fibrin glue is the most common adhesive currently used. It is biodegradable and induces very little inflammatory reaction.
Many adjunctive therapies have been used to reduce the rate of recurrence, none without their own complications. These include the following:
Corticosteroids: After pterygium excision, topical corticosteroids diminish the tissue reaction and inflammation and, consequently, the danger of recurrences. They are now accepted as the normal protocol after pterygium surgery. 19
Thiotepa (triethylene thiophosphoramide): It is a radiomimetic agent that obliterates neovessels by inhibiting mitosis of the endothelium of the capillaries. Diluted thiotepa (1:2,000) is used topically. Complications include vasodilatation of the conjunctival vessels, allergy to thiotepa, and depigmentation of the lid skin. 20
Cyclosporin A: It inhibits calcineurin, which is a serine/threonine phosphatase that dephosphorylates the nuclear factors of activated T cells. It has an antiproliferative action on the fibroblasts of the pterygium. 21
Mitomycin C (MMC): It is an antibiotic and antitumoral agent that inhibits ribonucleic acid (RNA) and deoxyribonucleic acid (DNA), the synthesis of proteins, and cellular proliferation. At 0.02% dilution, MMC has been applied with a soaked sponge to the denuded corneosclera for 2 minutes. MMC has also been used twice a day postoperatively for 5 days. Possible complications of MMC include epithelial keratopathy punctata, limbal avascularity, scleral and corneal dystrophy, corneal decompensation, calcification plaques, and, rarely, keratomalacia (corneal melting), glaucoma, and cataract. 22 It is currently commonly used by surgeons worldwide.
5-Fluorouracil (5-FU): It is a chemotherapeutic agent that inhibits thymidylate synthetase, an important enzyme for the synthesis of DNA. When a pterygium is recurring, the injection of 5-FU reduces its neovascularization, maybe because it inhibits the fibroblasts and, therefore, the consumption of oxygen and the stimulation of neovessels. 23
Vascular endothelial growth factor (VEGF) inhibitors: Pterygia show high levels of proangiogenic factors, such as tumor necrosis factor (TNF)-α, VEGF, fibroblast growth factor (FGF)-2, heparin-binding epidermal growth factor (HB-EGF), interleukin (IL)-6, IL-8, and matrix metalloproteinases (MMPs). This causes the typical neovascularization of pterygium. This forms the basis of use of anti-VEGF agents, such as bevacizumab. 24
Interferons (IFNs): They are cytokines secreted by cells stressed by infection, cancer, and other conditions. IFN type I (IFN-α and IFN-β) are secreted in all somatic cells, and IFN type II (IFN-γ) are secreted in the cells of the immune system. IFN-α2b has been used in recurrent pterygia. 25
Beta irradiation: It inhibits division of rapidly dividing cells and has thus been tried to reduce recurrence. The complications include scleral necrosis and melting, iris atrophy and cataract formation.
Last, amniotic membrane transplantation after pterygium excision is a common procedure nowadays, especially in cases of recurrent pterygia. Amniotic membrane has little antigenicity and, therefore, does not provoke immune rejection. It has leukotrienes, prostaglandins, interleukins, enzymes, epithelial growth factors, and vitamins that help normalize the ocular surface. It also has anti-VEGF, which inhibits neovascularization. It prevents fibroblastic proliferation and excessive scarring. 26 The latest advances in techniques which involve No stitches and No cutting 27 have made it possible to carry out the surgery (Gulani SPARKLE technique: Sutureless Pterygium with Amniotic Reconstruction and Lamellar Keratectomy Excision) inducing only minimal change in refraction. This is especially important in today’s times, where many patients wanting to undergo pterygium surgery have had refractive surgeries in the past (▶ Fig. 1.2, ▶ Fig. 1.3, ▶ Fig. 1.4).
Fig. 1.2 This active couple underwent SPARKLE Pterygium surgery to a cosmetic outcome which also simultaneously restored their corneal irregularity to a smooth measurable refraction to confidently then undergo Premium Cataract surgery with Multifocal Lens implants to 20/20 vision and actively pursuing life’s many sporty endeavors.