Published Online First: 12 July 2006. doi:10.1136/bjo.2006.095018
British Journal of Ophthalmology 2006;90:1476-1480
? 2006 by BMJ Publishing Group Ltd

EXTENDED REPORT

Randomised controlled study of conjunctival autograft versus amniotic membrane graft in pterygium excision

P Luanratanakorn1, T Ratanapakorn1, O Suwan-apichon1 and R S Chuck2

1 Department of Ophthalmology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
2 Wilmer Ophthalmological Institute, Johns Hopkins University, Baltimore, Maryland, USA

Correspondence to:
R S Chuck
Wilmer Ophthalmological Institute, Johns Hopkins University, 255 Woods Building, 600 North Wolfe Street, Baltimore, MD 21287-9278, USA;rchuck1@jhmi.edu

Accepted for publication 2 June 2006
*    ABSTRACT
 
Aim: To determine whether amniotic membrane can be used as an alternative to conjunctival autograft after pterygium excision.

Methods: 287 eyes with either primary or recurrent pterygium were included in this study. All eyes were randomised to undergo conjunctival autograft or amniotic membrane transplantation after pterygium excision by a single surgeon. 106 eyes in primary pterygium and 14 eyes in the recurrent group were treated with conjunctival autograft, and 148 eyes in primary pterygium and 19 eyes in the recurrent group were treated with amniotic membrane transplantation. Patients were followed up at 6 weeks and 6 months after operation. The main outcome measurement was recurrence rate after surgery.

Results: In the conjunctival group, the recurrence rate was 12.3%, 21.4% and 13.1% for primary, recurrent and all pterygia, respectively. In the amniotic membrane group, the recurrence rate was 25.0%, 52.6% and 28.1% for primary, recurrent and all pterygia, respectively. The recurrence rate for all pterygia in the amniotic membrane group was significantly higher than that in the conjunctival group (p = 0.003).

Conclusions: Amniotic membrane graft had a higher recurrence rate than conjunctival autograft. However, it is an alternative choice, especially for advanced cases with bilateral heads or patients who might need glaucoma surgery later.

Pterygium, a wing-shaped encroachment of the cornea by the conjunctiva, which may be atrophic, stationary or progressive, is a common eye problem, especially in tropical areas such as Thailand. Numerous surgical approaches have been attempted.1?5 All procedures can be classified according to the method of excision and the method of dealing with the defect created.

After excision, the resulting defect can be left exposed (bare sclera excision),6,7 or covered by surrounding conjunctiva (primary closure)4,6,8,9 or a pedicle flap,6,10 or by transposition of the pterygium head.11 The defect can also be covered by a conjunctival autograft without the limbus,8,11?17 or with the limbus,4,18?21 or using other tissue sources such as buccal mucous membrane grafts, lamellar keratoplasty,22,23 penetrating keratoplasty4 or sclerokeratoplasty.24 The other techniques include yttrium?aluminium?garnet (YAG) laser treatment25 and a polishing technique as advocated by Barraquer.26

Recently, Koranyi et al27 published a cut-and-paste technique in primary pterygium with fibrin glue, which showed markedly less postoperative pain and shortened surgery time. The recurrence rate was only 5.3%.

Without covering the defect, adjunctive treatment such as ?radiation,8,28,29 thiotepa,4 mitomycin C,15,30?35 5-fluorouracil,36 ciclosporin A37 or daunorubicin38 is used to reduce the recurrence rate. These adjunctive treatments are associated with complications, including poor epithelial healing,32 superficial punctate keratitis,33 late-onset scleral ulceration, microbial infection, glaucoma and endophthalmitis.39,40 Owing to these potential complications, conjunctival autografting has been widely adopted in the management of pterygium. Although this method has reduced the recurrence rate,12,16,41,42 questions have been raised whether conjunctival autografts should be reserved solely for recurrent pterygia because of the risk of compromising the outcome of glaucoma-filtering surgery if it should be required at some future date in the donor eye.12 Moreover, for those with advanced pterygia with wide conjunctival involvement or multiple heads, conjunctival autografts might be limited by the lack of remaining healthy tissue in the same or fellow eye. For these reasons, an alternative tissue source has been sought. Many authors have reported that amniotic membrane grafts are a viable alternative to conjunctival autografts in reducing recurrences after pterygium excision.43?49 The possible mechanisms of preventing pterygium recurrence include promotion of conjunctival epithelium, inhibition of inflammation by inhibiting chemokine expression by fibroblasts50,51 and interleukin-1 expression by epithelial cells, and inhibition of neovascularisation by inhibiting vascular endothelial cell growth.52 As there has been no randomised study comparing the recurrence rate between conjunctival autografts and amniotic membrane grafts in both primary and recurrent pterygium, especially in tropical areas, we conducted a randomised controlled study to examine this question.


*    MATERIALS AND METHODS
 
Patients
We carried out excision of pterygia at Srinagarind Hospital (Khon Kaen, Thailand) from 2000 to 2001 under protocol #I 44034 approved by the Medical Science Subcommittee for the protection of Human Subjects in Research of Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand. The inclusion and exclusion criteria were proposed as follows.

The inclusion criteria

  1. Patients who were diagnosed with pterygium (both primary and recurrent pterygia) at Srinagarind Hospital and met the indication for surgical treatment.
  2. Patients with pterygium who signed the informed consent to enrol into the study.

The exclusion criteria

  1. Patients who had glaucoma in the study eye.
  2. Patients who had an intraocular pressure >21 mm Hg in the study eye.
  3. Patients who had a history of allergy to steroid eye drops.
  4. Patients enrolled in another study, that might affect this study.
  5. Patients who had not cooperated during pterygium excision surgery.

This study was designed as a single-blind randomised control trial. The patients were randomised into two groups by a simple randomisation technique. The sample size in this study was calculated based on the recurrence rate in the study of Prabhasawat et al.43

Sample size = [(Z{alpha}+Z?/SUB>)22P(1?P)]/D2

where P = (P1+P2)/2; D = P1?P2; Z{alpha} = type-I error (5%); Z?/SUB> = type-II error (20%); P1 = recurrence rate in the amniotic membrane group = 0.143 (14.3%); P2 = Recurrence rate in the conjunctival autograft group = 0.049 (4.9%)

The results with respect to age, sex, size of pterygium and recurrence rates were compared between those of 120 patients (120 eyes) receiving excision of pterygia followed by conjunctival autograft and those of 167 patients (167 eyes) receiving excision of pterygia followed by amniotic membrane graft. These two procedures were carried out by the same surgeon to ensure that similar amounts of pterygial and surrounding fibrovascular tissue were removed. The results at 6 weeks and 6 months were examined by the same investigator in a blind assessment to grade the final appearance based on the criteria given by Prabhasawat et al.43 Grade 1 indicates that the appearance of the operated site was not different from the normal appearance; grade 2 indicates that there were some fine episcleral vessels in the excised area extending up to, but not beyond, the limbus and without any fibrous tissue; grade 3 indicates that there were additional fibrous tissues in the excised area that did not invade the cornea; grade 4 represents a true recurrence, with fibrovascular tissue invading the cornea.

Preparation of preserved human amniotic membrane
Human amniotic membrane was prepared and preserved using the method of Kim and Tseng,53 with minor modification. Human placenta was obtained shortly after elective caesarean section and exclusion of human immunodeficiency virus, hepatitis B and C viruses, and syphilis by serological testing. In a sterile operating room, the placenta was cleaned of blood clots with 0.9% normal saline and Earl?s balanced salt solution (Gibthai, Bangkok, Thailand) containing 50 mg/ml penicillin, 50 mg/ml streptomycin, 100 mg/ml neomycin and 2.5 mg/ml amphotericin B. The amnion was separated from the rest of the chorion by blunt dissection to open the intervening potential space. The isolated amniotic membrane was then flattened on to a nitrocellulose paper with a pore size of 0.45 ?m (Gibthai) with the epithelium or basement membrane surface facing up. The sheet, combined with the amniotic membrane and the filter, was then cut into 3x4-cm2 disks, and stored at ?80?C in a sterile vial containing Dulbecco modified Eagle?s medium (Gibthai) and glycerol (Gibthai) at a ratio of 1:1 (vol/vol) before transplantation.

Surgical technique for pterygium excision
All patients received topical anaesthesia of 0.4% oxybuprocaine hydrochloride (Novesin; Novartis, Thailand). The eye undergoing surgery was prepared and draped in the usual sterile fashion. After insertion of a lid speculum, the pterygium tissue was measured from the limbus to the head of the pterygium. The pterygium was then injected with 0.5 ml of 2% xylocaine with epinephrine 1:80 000. The pterygium was cut near the limbus using Wescott?s scissors. The head of the pterygium was removed from the surface of the cornea. Subconjunctival fibrous tissue was then completely removed in an area much greater than the pterygium body itself. The completeness of episcleral tissue removal was judged by exposing all the tortuous episcleral blood vessels extending from the nasal rectus muscle insertion for nasal pterygium. Any abnormal scars on the cornea surface were removed with a no 15 blade.

For conjunctival autografts, a free graft of size similar to the defect area was obtained from the superotemporal bulbar conjunctiva.54,55 For amniotic membrane grafts, the preserved amniotic membrane was removed from the storage medium after thawing and cut into the same size as the defect. Both types of graft were secured, flattened and approximated to the recipient episcleral tissue edge by 10 interrupted 10-0 nylon sutures.

After surgery, all patients received dexamethasone phosphate 0.1% (Sang Thai Medical, Bangkok, Thailand) eye drops four times per day, and tapered off within 1 month. Sutures were removed 2 weeks after surgery.

Statistical analysis
All demographic data including age, sex, occupation and diagnosis were compared between conjunctival autografts and amniotic membrane grafts using the {chi}2 test. The recurrence rates between the two groups at 6 weeks and 6 months were also analysed using the {chi}2 test.


*    RESULTS
 
A total of 346 eyes of 346 patients were included in the study. Although some of the patients had bilateral pterygium in our series, patients allowed us to carry out surgery only monocularly. All patients were Asian (Thai). In total, 59 patients were lost to follow-up (one patient died from a car accident and the remainder did not show up in the clinic owing to unknown reasons). Of 59 patients lost to follow-up, there were 45 patients (76.27%) in the primary pterygium group and 15 patients (23.73%) in the recurrent group. The total number of eyes in the conjunctival group was 120, including 106 eyes in the primary group and 14 eyes in the recurrent group. The total number of eyes in the amniotic membrane group was 167, including 148 eyes in the primary group and 19 eyes in the recurrent group. The number of recurrences was one time in both conjunctival autograft and amniotic membrane groups before enrolment into this study. The ratio of the right and left eyes, male and female, and the age range and size of pterygia were similar in both groups (table 1Go).


Complications included increase in the intraocular pressure in 14 patients, of which 13 patients returned to normal level (eight patients from the conjunctival autograft group and five patients from the amniotic membrane group) and 1 patient (from the conjunctival autograft group) received trabeculectomy. Pyogenic granuloma occurred in seven patients (four patients from the conjunctival autograft group and three patients from amniotic membrane group). No symblepharon was found in any of the patients.

The recurrence rate in the conjunctival group at 6 weeks was 6.6% for primary pterygia and 7.1% for recurrent pterygia, and the corresponding rates for the amniotic membrane group were 5.4% and 10.5%. We found no significant differences in the recurrence rate between the two groups (p = 0.815; table 2Go).


The total recurrence rate in the conjunctival group at 6 months was 13.3% (primary pterygia 12.3%, recurrent pterygia 21.4%), and that in the amniotic membrane group was 28.1% (primary pterygia 25.0%, recurrent pterygia 52.6%). Thus, at 6 months, amniotic membrane graft had significantly higher recurrence rate than conjunctival autograft (p = 0.003; table 3Go).



*    DISCUSSION
 
A pterygium is characterised by excessive fibrovascular proliferation on the exposed ocular surface, and is thought to be caused by increased ultraviolet light exposure from climatic factors and aggravated by microtrauma and chronic inflammation from environmental factors.2?4,56,57 Despite the multifactorial pathogenesis, surgery is the mainstay of treatment. The primary concern in pterygium surgery is recurrence defined by regrowth of the fibrovascular tissue across the limbus and on to the cornea.58

The reported recurrence rates vary greatly not only among different surgical procedures but also between different groups carrying out the same procedure. To eliminate such variability, the same technique was carried out by the same surgeon throughout the study. With this variable controlled, and similar demographic data (table 1Go) and sufficient follow-up, we can compare the role of conjunctival autografts and amniotic membrane grafts in covering the pterygium excision defects to reduce the recurrence rate. Our result, which is similar to the result of the study by Prabhasawat et al,43 confirms that conjunctival autografts achieve the best result, with a recurrence rate of 13.3% at 6 months in a total of 120 eyes, which consisted of 106 primary and 14 recurrent pterygia (p = 0.003; table 3Go). The recurrence rates in our study were higher in both groups than those previously reported,43 possibly due to the race of our patients, amount of subconjunctival tissue removal, type of suture used and drug given after surgery. The recurrence rates in our study were similar to those found in a previous study in Thailand,58 4.76% and 40.9% in conjunctival autograft and amniotic membrane graft groups, respectively.

The recurrence rate in the amniotic membrane graft group was 28.1% at 6 months in a total of 167 eyes, which consisted of 148 primary and 19 recurrent pterygia. At 6 weeks, when we excluded patients with recurrent pterygia, who might have received different surgery or treatments before the study, and only looked at those with primary pterygia, the recurrence rate with conjunctival autografts was 6.6%, which was slightly more than the 5.4% with amniotic membrane grafts (p = 0.690). With the longer follow-up, the recurrence rate of amniotic membrane grafts at 6 months was 25.0%, which was significantly more than the 12.3% of the conjunctival grafts (p = 0.012).

The two procedures produce differences in final appearance not only with respect to the rate of frank recurrence (defined as grade 4 in this study) but also in the percentage of grade 1 (ie, normal appearance). As listed in tables 4Go and 5Go, the percentage of grade 1 was higher in conjunctival autografts than in amniotic membrane grafts. Even when we examined those patients with final grades of 2 and 3 (ie, intermediate between normal appearance and frank recurrence), a similar trend emerged. The percentage of grades 2 and 3 for conjunctival autografts was less than that for amniotic membrane grafts. This result suggests that covering the defect area with normal conjunctival tissue also has a higher likelihood of promoting the restoration of a normal appearance.


The amniotic membrane is known to contain a thick basement membrane and a vascular streamed matrix,50,60 and we theorise that these features are crucial to the observed success. The basement membrane facilitates migration of epithelial cells, reinforces adhesion of basal epithelial cells,61 reinforces adhesion of basal epithelial cells,64,65 promotes epithelial differentiation66?69 and prevents epithelial apoptosis.68,69 Collectively, these actions explain why the amniotic membrane permits rapid epithelialisation.

Although this study shows that amniotic membrane grafts are less proficient than conjunctival autografts in reducing recurrences after pterygium excision, it indicates that this technique could be considered as an alternative in the surgical management of pterygia, especially when the bare sclera technique alone has an unacceptably high recurrence,70 and complications related to mitomicin-C as an adjunctive treatment are a concern.71 Conjunctival autograft should be considered as the first choice for pterygium excision even if there is a recurrence. The amniotic membrane graft can also be considered to be the first choice for those with advanced and diffuse conjunctival involvement (bi-head) or those who might like to preserve the donor bulbar conjunctiva for a prospective glaucoma-filtering procedure. With these limitations, careful use of adjunctive treatment such as mitomycin C may be useful and needs further study.

 
*    FOOTNOTES
 
Published Online First 12 July 2006

Funding: This study was supported by an invitation grant from the Faculty of Medicine, Khon Kaen University.

Competing interests: None declared.


*    REFERENCES
 

  1. Rosenthal JW. Chronology of pterygium therapy. Am J Ophthalmol 1953;36:1601?16.
  2. Duke-Elder SS. ed. Degenerative and pigmentary changes. In: System of ophthalmology. 3rd edn. London: Henry Kimpton, 1977:569?85.
  3. Jaros PA, DeLuise VP. Pingueculae and pterygia. Surv Ophthalmol 1988;33:41?9.
  4. Adamis AP, Starck T, Kenyon KR. The management of pterygium. Ophthalmol Clin North Am 1990;3:611?23.
  5. Lani AH, Lani LA. Conjunctival autograft transplantation in primary pterygium. Arq Bras Oftalmol 2005;68:99?102.
  6. King JJH. The pterygium. Brief review and evaluation of certain methods of treatment. Arch Ophthalmol 1950;44:854?69.
  7. Dowlut MS, Laflamme MY. Les pterygions recidivants: frequence et correction par autogreffe conjonctivale. Can J Ophthalmol 1981;16:119?20.
  8. Anduze AL. Merest sclera technique for primary pterygium surgery. Ophthalmic Surg 1989;20:892?3.
  9. Riordan-Eva P, Kielhorn I, Ficker LA, et al. Conjunctival autografting in the surgical management of pterygium. Eye 1993;7:634?8.
  10. McCoombes JA, Hirst LW, Isbell GP. Sliding conjunctival flap for the treatment of primary pterygium. Ophthalmology 1994;101:169?73.
  11. Said A, Fouad ARA, Mostafa MSE, et al. Surgical management of recurrent pterygium by an operation of transposition. Bull Ophthalmol Soc Egypt 1975;68:81?4.
  12. Kenyon KR, Wagoner MD, Hettinger ME. Conjunctival autograft transplantation for advanced and recurrent pterygium. Ophthalmology 1985;92:1461?70.
  13. Lewallen S. A randomized trial of conjunctival autografting for pterygium in the tropics. Ophthalmology 1989;96:1612?14.
  14. Singh G, Wilson MR, Foster CS. Long-term follow-up study of mitomycin eye drops as adjunctive treatment for pterygia and its comparison with conjunctival autograft transplantation. Cornea 1990;9:331?4.
  15. Starck T, Kenyon KR, Serrano F. Conjunctival autograft for primary and recurrent pterygia: surgical technique and problem management. Cornea 1991;10:196?202.
  16. Allan BD, Short P, Crawford GJ, et al. Pterygium excision with conjunctival autografting: an effective and safe technique. Br J Ophthalmol 1993;77:698?701.
  17. Chen PP, Ariyasu RG, Kaza V, et al. A randomized trial comparing mitomycin C and conjunctival autograft after excision of primary pterygium. Am J Ophthalmol 1995;120:151?60.
  18. Hara T, Shoji E, Hara T, et al. Pterygium surgery using the principle of contact inhibition and a limbal transplanted pedicle conjunctival strip. Ophthalmic Surg 1994;25:958.
  19. Guler M, Sobaci G, Ilker S, et al. Limbal-conjunctival autograft transplantation in cases with recurrent pterygium. Acta Ophthalmol 1994;72:721?6.
  20. Figueiredo RS, Cohen EJ, Gomes JA, et al. Conjunctival autograft for pterygium surgery: how well does it prevent recurrence? Ophthalmic Surg Lasers 1997;28:99?104.
  21. Rao SK, Lekha T, Mukesh BN, et al. Conjunctival autograft for primary and recurrent pterygia: technique and results. Indian J Ophthalmol 1998;46:203?9.
  22. Laughrea PA, Arentsen JJ. Lamellar keratoplasty in the management of recurrent pterygium. Ophthalmic Surg 1986;17:106?8.
  23. Busin M, Halliday BL, Arffa RC, et al. Precarved lyophilized tissue for lamellar keratoplasty in recurrent pterygium. Am J Ophthalmol 1986;102:222?7.
  24. Suveges I. Sclerokeratoplasty in recurrent pterygium. Ger J Ophthalmol 1992;1:114?16.
  25. Nakamura K, Bissen-Miyajima H, Shimmura S, et al. Clinical application of Er:YAG laser for the treatment of pterygium. Ophthalmic Surg Lasers 2000;31:8?12.
  26. Barraquer MJ. Localized discontinuity of the precorneal lacrimal film. Etiology of Fuchs? marginal corneal ulcers, of progression of pterygium and of certain corneal necroses in the neighborhood of keratoprostheses and keratoplasties. Ophthalmologica 1965;150:111?22.
  27. Koranyi G, Seregard S, Kopp, eds. Cut and paste: a no suture, small incision approach to pterygium surgery. Br J Ophthalmol 2004;88:911?14.
  28. Keizer RJW. Pterygium excision with or without postoperative irradiation, a double-blind study. Doc Ophthalmol 1982;52:309?15.
  29. Mackenzie FD, Hirst LW. Kynaston B, et al. Recurrence rate and complications after beta irradiation for pterygia. Ophthalmology 1991;98:1776?81.
  30. Singh G, Wilson MR, Foster CS. Mitomycin eye drops as treatment for pterygium. Ophthalmology 1988;95:813?21.
  31. Hayasaka S, Noda S, Yamamoto Y, et al. Postoperative instillation of low-dose mitomycin C in the treatment of primary pterygium. Am J Ophthalmol 1988;106:715?18.
  32. Frucht-Pery J, Ilsar M, Hemo I. Single dosage of mitomycin C for prevention of recurrent pterygium: preliminary report. Cornea 1994;13:411?13.
  33. Rachmiel R, Leiba H, Levartovsky S. Results of treatment with topical mitomycin C 0.02% following excision of primary pterygium. Br J Ophthalmol 1995;79:233?6.
  34. Cano-Parra J, Diaz-Llopis M, Maldonado MJ, et al. Prospective trial of intraoperative mitomycin C in the treatment of primary pterygium. Br J Ophthalmol 1995;79:439?41.
  35. Mahar PS. Conjunctival autograft versus topical mitomycin C in treatment of pterygium. Eye 1997;11:790?2.
  36. Akarsu C, Taner P, Ergin A. 5-Fluorouracil as chemoadjuvant for primary pterygium surgery: preliminary report. Cornea 2003;22:522?6.
  37. Wu H, Chen G. Cyclosporine A and thiotepa in prevention of postoperative recurrence of pterygium. Yan Ke Xue Bao 1999;15:91?2.
  38. Dadeya S, Kamlesh. Intraoperative daunorubicin to prevent the recurrence of pterygium after excision. Cornea 2001;20:172?74.
  39. Tarr KH, Constable IJ. Late complications of pterygium treatment. Br J Ophthalmol 1980;64:496?505.
  40. Dougherty PJ, Hardten DR, Lindstrom RL. Corneoscleral melt after pterygium surgery using a single intraoperative application of mitomycin C. Cornea 1996;15:537?40.
  41. Alaniz-Camino F. The use of postoperative beta radiation in the treatment of pterygia. Ophthalmic Surg 1982;13:1022?5.
  42. Tan DT, Chee SP, Dear KB, et al. Effect of pterygium morphology on pterygium recurrence in a controlled trial comparing conjunctival autografting with bare sclera excision. Arch Ophthalmol 1997;115:1235?40.
  43. Prabhasawat P, Barton K, Burkett G, et al. Comparison of conjunctival autografts, amniotic membrane grafts, and primary closure for pterygium excision. Ophthalmology 1997;104:974?85.
  44. Shimazaki J, Shinozaki N, Tsubota K. Transplantation of amniotic membrane and limbal autograft for patients with recurrent pterygium associated with symblepharon. Br J Ophthalmol 1998;82:235?40.
  45. Ma DHK, See LC, Liau SB, et al. Amniotic membrane graft for primary pterygium: comparison with conjunctival autograft and topical mitomycin C treatment. Br J Ophthalmol 2000;84:973?8.
  46. Shimazaki J, Kosaka K, Shimmura S, et al. Amniotic membrane transplantation with conjunctival autograft for recurrent pterygium. Ophthalmology 2003;110:119?24.
  47. Xi XH, Jiang DY, Tang LS. Transplantation of amniotic membrane and amniotic membrane combined with limbal autograft for patients with complicated pterygium. Hunan Yi Ke Da Xue Xue Bao 2003;28:149?51.
  48. Kawasaki S, Uno T, Shimamura I, et al. Outcome of surgery for recurrent pterygium using intraoperative application of mitomycin C and amniotic membrane transplantation. Nippon Ganka Gakkai Zasshi 2003;107:316?21.
  49. Chandra A, Maurya OP, Reddy B, et al. Amniotic membrane transplantation in ocular surface disorders. J Indian Med Assoc 2005;103:364?6.
  50. Bultmann S, You L, Spandau U, et al. Amniotic membrane down-regulates chemokine expression in human keratocytes. Invest Ophthalmol Vis Sci 1999;40:S578.
  51. Tseng SCG, Li DG, Ma X. Suppression of transforming growth factor-beta isoforms, TGF-B receptor type II, and myofibroblast differentiation in cultured human corneal and limbal fibroblast by amniotic membrane matrix. J Cell Physiol 1999;179:325?35.
  52. Kobayashi A, Inana G, Meller D, et al. Differential gene expression by human cultured umbilical vein endothelial cells on amniotic membrane. Presented at the 4th Ocular Surface and Tear Conference; 14 May 1999, Miami, FL, USA.
  53. Kim JC, Tseng SC. Transplantation of preserved human amniotic membrane for surface reconstruction in severely damaged rabbit corneas. Cornea 1995;14:473?84.
  54. Vastine DW, Stewart WB, Schwab IR. Reconstruction of the periocular mucous membrane by autologous conjunctival transplantation. Ophthalmology 1982;89:1072?81.
  55. Camara JG, dela Cruz-Rosas B, Nguyen LT. The use of a radiofrequency unit for harvesting conjunctival autografts in pterygium surgery. Am J Ophthalmol 2004;138:165?7.
  56. Hilgers JHC. Pterygium: incidence, heredity and etiology. Am J Ophthalmol 1960;50:635?44.
  57. Mackenzie FD, Hirst LW, Battistutta D, et al. Risk analysis in the development of pterygia. Ophthalmology 1992;99:1056?61.
  58. Tananuvat N, Martin T. The results of amniotic membrane transplantation for primary pterygium compared with conjunctival autograft. Cornea 2004;23:458?63.
  59. Liotta LA, Lee CW, Morakis DJ. New method for preparing large surfaces of intact human basement membrane for tumor invasion studies. Cancer Lett 1980;11:141?52.
  60. Campbell S, Allen TD, Moser BB, et al. The translaminal fibrils of the human amnion basement membrane. J Cell Sci 1989;94:307?18.
  61. Terranova VP, Lyall RM. Chemotaxis of human gingival epithelial cells to laminin. A mechanism for epithelial cell apical migration. J Periodontol 1986;57:311?17.
  62. Khodadoust AA, Silverstein AM, Kenyon KR, et al. Adhesion of regenerating corneal epithelium. The role of basement membrane. Am J Ophthalmol 1968;65:339?48.
  63. Sonnenberg A, Calafat J, Janssen H, et al. Integrin a6/b4 complex is located in hemidesmosomes, suggesting a major role in epidermal cell-basement membrane adhesion. J Cell Biol 1991;113:907?17.
  64. Barcellos-Hoff MH, Aggeler J, Ram TG, et al. Functional differentiation and alveolar morphogenesis of primary mammary cultures on reconstituted basement membrane. Development 1989;105:223?35.
  65. Guo M, Grinnell F. Basement membrane and human epidermal differentiation in vitro. J Invest Dermatol 1989;93:372?8.
  66. Streuli CH, Bailey N, Bissell MJ. Control of mammary epithelial differentiation: basement membrane induces tissue-specific gene expression in the absence of cell-cell interaction and morphological polarity. J Cell Biol 1991;115:1383?95.
  67. Kurpakus MA, Stock EL, Jones JCR. The role of the basement in differential expression of keratin proteins in epithelial cells. Dev Biol 1992;150:243?55.
  68. Boudreau N, Sympson CJ, Werb Z, et al. Suppression of ICE and apoptosis in mammary epithelial cells by extracellular matrix. Science 1995;267:891?3.
  69. Boudreau N, Werb Z, Bissell MJ. Suppression of apoptosis by basement membrane requires three-dimensional tissue organization and withdrawal from the cell cycle. Proc Natl Acad Sci USA 1996;93:3500?13.
  70. Fernandes M, Sangwan VS, Bansal AK, et al. Outcome of pterygium surgery: analysis over 14 years. Eye 2005;19:1182?90.
  71. Raiskup F, Solomon A, Landau D, et al. Mitomycin C for pterygium: long term evaluation. Br J Ophthalmol 2004;88:1425?8.