Ординатура / Офтальмология / Английские материалы / Oculoplasty and Reconstructive Surgery Made Easy_Garg,Touky, Nasralla_2009
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Pterygium Excision 219
PTERYGIUM SURGERY
Microsurgical excision of a pterygium aims to achieve a normal, topographically smooth ocular surface
Multiple different procedures have been advocated in the treatment of pterygia (Figure 2A). These procedures range from simple excision to sliding flaps of conjunctiva with and without adjunctive external beta radiation therapy and/or use of topical chemotherapeutic agents, such as mitomycin C.
Surgery for excision of pterygia is usually performed in an outpatient setting under local or topical anesthesia with sedation, if necessary.
Bare Sclera
One of the most popular methods for the removal of primary pterygium is excision of all remnants of the pterygium, leaving the underlying bare sclera exposed. Sharp dissection from the corneal side and from the uninvolved perimeter of normal conjunctiva is necessary. The cornea is left as smooth as possible, and all of Tenon’s capsule from beneath the pterygium is excised.
After excision, light thermal cautery is usually applied to the sclera for hemostasis. No sutures or fine, absorbable sutures are used to appose the conjunctiva to the superficial sclera in front of the rectus tendon insertion, leaving an area of exposed sclera. This procedure has a relatively high recurrence rate, with variable techniques, of 5 to 68% with primary pterygium and 35-82% with recurrent pterygium
(Figure 2B).
Simple Closure
The free edges of the conjunctiva are secured together. This technique is effective only when the conjunctival defect is very
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small. It may also be used for pingueculae removal. There are few complications with this method. The most frequent complication is dellen (thinning of the cornea) that occurs from dehydration. Reported recurrence rates range from 45 to 69%
(Figure 2C).
Sliding Flap
An L-shaped incision is made adjacent to the wound to allow a conjunctival flap to slide into place. Reported recurrence rates range from 0.75 to 5.6%. The most frequent complications are flap retraction and cyst formation (Figure 2D).
Rotational Flap
Rotation of a flap of superior conjunctiva is thought to prevent recurrence and provide a smooth surface at the limbus to encourage proper tear film distribution. A U-shaped incision is made adjacent to the wound to form a tongue of conjunctiva that is rotated into place. Reported recurrence rates range from 4 to 6% (Figure 2E).
Conjunctival Graft
The most common indication for conjunctival graft is the management of advanced primary and recurrent pterygium (Figure 3). This technique reduces the risk of pterygium recurrence to approximately 2 to 5% and ameliorates the restriction of extraocular muscle function frequently encountered after pterygium excision. Because the superior bulbar conjunctiva is usually normal and undamaged, conjunctival autograft tissue can be obtained from this area in the same eye. The free graft is excised to correspond to the size of the wound and is then moved and sutured into place
(Figure 2F).
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Figures 2A to F: Surgical wound closures following pterygium excision.
(A) Pterygium; (B) Bare sclera; (C) Simple closure with fine, absorbable sutures; (D) Sliding flap that is closed with interrupted and/or running suture; (E) Rotational flap from the superior bulbar conjunctiva; (F)
Conjunctival autograft that is secured with interrupted and/or running suture
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Figure 3: Recurrent pterygium
For moderate-to-severe pterygia, some corneal surgeons use amniotic membrane transplants. Both the conjunctival autografts and the amniotic membrane transplants may be sutured onto adjacent conjunctiva and subjacent cornea. Some corneal surgeons seal the graft tissue onto the underlying sclera with the aid of fibrin tissue glue rather than with sutures.
ADJUNCTIVE THERAPY
A number of adjunctive therapies have been described to decrease the risk of recurrence after the surgical removal of a pterygium. Each has its attractive features, but none is without drawbacks.
Corticosteroids
New vessels often herald the recurrence of a pterygium. Postoperative use of topical corticosteroids inhibits the
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inflammatory reaction and may reduce revascularization of the operative site. However, long-term corticosteroid treatment may cause relevant side effects: ocular hypertension, glaucoma, and cataract. Moreover, controlled clinical trials have not demonstrated any significant role of topical corticosteroids in pterygium recurrence prevention.
Thiotepa
Thiotepa (triethylene-thiophosphoramide) is a nitrogen mustard alkylating agent with antimitotic properties. It is a radiomimetic agent that presumably obliterates proliferating vascular endothelial cells. The most common dose is 1:2000 thiotepa given up to every 3 hours for approximately 6 weeks. It is usually used with the bare sclera method. The most frequent complication is scleral thinning (Recurrence rate: 1016%).
Interferon Alpha-2b
Interferons are glycoproteins that have been shown to have antiproliferative and antiviral effects. Although the exact mechanism of action of interferons is unknown, the recombinant form of interferon alpha-2b (IFN-α-2b) has been used with good results in conjunctival intraepithelial neoplasia, conjunctival papilloma and as a lone therapy for early pterygium recurrence.
However, further studies are needed to delineate the ideal dosing and tapering schedule for topical Interferon alpha-2b administration in the treatment of early recurrent pterygium.
Mitomycin C
Mitomycin C (MMC), isolated from Streptomyces caespitosus, is an antibiotic with antineoplastic properties that blocks DNA
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synthesis. Although the recurrence rate was reduced by use of MMC, reports of side effects associated with its use (e.g. pyogenic granuloma, dellen of the sclera, perforation of the eye, glaucoma, cataract, corneal edema) have remained obstacles to its usefulness. MMC is used with bare sclera or single conjunctival closure, especially for recurrent cases. Most common concentration is 0.02%. Reported recurrence rates range from: 3-25% for intra-operative application (depending on the time of exposure) and 5-54% for postoperative application.
5-fluorouracil
The antiproliferative effect of 5-FU arises from its metabolites acting as metabolic blockers that inhibit thymidylate synthetase, which converts ribonucleotides to deoxyribonucleotides, thus inhibiting DNA synthesis. It acts selectively on the growth phases corresponding to DNA and RNA synthesis, respectively, in the cell cycle. Therefore, only those cells in the synthesis phase are affected, thus allowing the remaining cells to continue to proliferate after exposure to 5-FU. The topical use of 5-FU can cause epitheliopathy, ocular surface inflammation, pain and dry eye symptoms. Few studies, with limited number of patients, poor follow-up, and variable recurrence rates limit its application.
Beta Radiation
Inhibition of proliferating cells in the wound bed can also be accomplished by beta radiation, which presumably reduces mitosis in rapidly dividing vascular endothelial cell. However, the use of Beta radiation has been associated with late scleral melting in 13% of cases, cataract formation and conjunctival telangiectasia. Most common dosage is 15 Gy in single or
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divided doses. Reported recurrence rates range from: 4.3% to 35%, with bare sclera or single conjunctival closure. The most serious complications are scleral necrosis and endophthalmitis.
Amniotic Membrane
The use of amniotic membrane is useful for very large, conjunctival defects as in primary double-headed pterygium or to preserve superior conjunctiva for future glaucoma surgeries. It is associated with a recurrence rate of 3.0 to 40.9%, as well as the increased cost, stress and trauma of an additional surgical procedure.
SURGERY COMPLICATIONS
•Limitation of duction of the globe by subconjunctival scarring with resultant diplopia after primary resection of the pterygium.
•Inadvertent disinsertion of the medial rectus muscle or scleral perforation during pterygium excision.
•Corneal irregularity in the visual axis secondary to deep stromal excision of the pterygium.
CLINICAL PEARLS
•Pterygia are common ocular lesions, usually cured by primary excision.
•The surgeon should remain aware that relatively simple pterygium cases, if allowed to progress, can impair vision. This means that the pterygium need not cover the visual axis to inflict significant visual compromise. Surgery must be performed before vision is affected.
•Follow up on mediumto large-sized pterygia at least once or twice yearly, and include a manifest refraction, corneal
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topography, slit-lamp evaluation with measurement of the pterygium, and photodocumentation if possible.
•When a pterygium recurs, more sophisticated surgery is necessary. Excellent microsurgical technique for the initial and secondary treatment of pterygium should keep these deleterious consequences to a minimum.
•Use of beta radiation and antimetabolites can be used with appropriate caution.
BIBLIOGRAPHY
1.Anduze AL. Pterygium surgery with mitomycin-C: ten-year results. Ophthalmic Surg Lasers 2001;32(4):341-5.
2.Bahar I, Weinberger D, Gaton DD, Avisar R. Fibrin glue versus vicryl sutures for primary conjunctival closure in pterygium surgery: longterm results. Curr Eye Res 2007;32(5):399-405.
3.Cogan DG, Kuwabara T, Howard J. The nonelastic nature of pingueculas. Arch Ophthalmol 1959;61:388.
4.Cohen RA, McDonald MB. Fixation of conjunctival autografts with an organic tissue adhesive. Arch Ophthalmol 1993;111(9):1167-68.
5.Coroneo MT, Di Girolamo N, Wakefield D. The pathogenesis of pterygia. Curr Opin Ophthalmol 1999;10(4):282-8.
6.Dougherty PJ, Hardten DR, Lindstrom RL. Corneoscleral melt after pterygium surgery using a single intraoperative application of mitomycin-C. Cornea 1996;15:537-40.
7.Elliot R. The aetiology of pterygium. Trans Ophthalmol Soc NZ 1961;13:22.
8.Esquenazi S. Treatment of early pterygium recurrence with topical administration of interferon alpha-2b. Can J Ophthalmol 2005;40:185- 7.
9.Fernandes M, Sangwan VS, Bansal AK, Gangopadhyay N, Sridhar MS, Garg P, et al. Outcome of pterygium surgery: analysis over 14 years. Eye 2005;19(11):1182-90.
10.Jain AK, Bansal R, Sukhija J. Human amniotic membrane transplantation with fibrin glue in management of primary pterygia: a new tuck-in technique. Cornea 2008;27(1):94-9.
11.Kamel S. The Pterygium: its etiology and treatment. Am J Ophthalmol 1954;38:682.
Pterygium Excision 227
12.Kheirkhah A, Casas V, Sheha H, Raju VK, Tseng SC. Role of conjunctival inflammation in surgical outcome after amniotic membrane transplantation with or without fibrin glue for pterygium Cornea 2008;27(1):56-63.
13.Lee JS, Oum BS, Lee SH. Mitomycin c influence on inhibition of cellular proliferation and subsequent synthesis of type I collagen and laminin in primary and recurrent pterygia. Ophthalmic Res 2001;33(3):140-6.
14.McDonald JE, Wilson FM. Ocular therapy with beta particles. Trans Am Acad Ophthalmol Otolaryngol 1959;63:468.
15.Miyai T, Hara R, Nejima R, Miyata K, Yonemura T, Amano S. Limbal allograft, amniotic membrane transplantation, and intraoperative mitomycin C for recurrent pterygium. Ophthalmology 2005;112(7):1263-7.
16.Oguz H. Amniotic membrane grafting versus conjunctival autografting in pterygium surgery. Clin Experiment Ophthalmol 2005;33(4):447-8.
17.Raiskup F, Solomon A, Landau D, Ilsar M, Frucht-Pery J. Mitomycin C for pterygium: long term evaluation. Br J Ophthalmol 2004;88(11):1425-8.
18.Rubinfeld RS, Pfister RR, Stein RM, Foster CS, Martin NF, Stoleru S, et al. Serious complications of topical mitomycin-C after pterygium surgery. Ophthalmology 1992;99(11):1647-54.
19.Saw SM, Tan D. Pterygium: prevalence, demography and risk factors. Ophthalmic Epidemiol 1999;6(3):219-28.
20.Singh G, Wilson MR, Foster CS. Long-term follow-up study of mitomycin eye drops as adjunctive treatment of pterygia and its comparison with conjunctival autograft transplantation. Cornea 1990;9(4):331-4.
21.Srinivasan S, Slomovic AR. Eye rubbing causing conjunctival graft dehiscence following pterygium surgery with fibrin glue. Eye 2007;21(6):865-7.
22.Starck T, Kenyon KR, Serrano F. Conjunctival autograft for primary and recurrent pterygia: surgical technique and problem management. Córnea 1991;10(3):196-202.
23.Tan D. Conjunctival grafting for ocular surface disease. Curr Opin Ophthalmol 1999;10(4):277-81.
24.Threlfall TJ, English DR. Sun exposure and pterygium of the eye: a dose-response curve. Am J Ophthalmol 1999;128(3):280-7.
25.Ti SE, Chee SP, Dear KB, Tan DT. Analysis of variation in success rates in conjunctival autografting for primary and recurrent pterygium. Br J Ophthalmol 2000;84(4):385-9.
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26.Tsai YY, Lin JM, Shy JD. Acute scleral thinning after pterygium excision with intraoperative mitomycin C. Cornea 2002;21:227-9.
27.Uy HS, Reyes JM, Flores JD, Lim-Bon-Siong R. Comparison of fibrin glue and sutures for attaching conjunctival autografts after pterygium excision. Ophthalmology 2005;112(4):667-71.
28.Yao YF, Qiu WY, Zhang YM, Tseng SC. Mitomycin C, amniotic membrane transplantation and limbal conjunctival autograft for treating multirecurrent pterygia with symblepharon and motility restriction. Graefes Arch Clin Exp Ophthalmol 2006;244(2):232-6.