RADIATION DAMAGE AFTER PTERYGIUM TREATMENT*

Transcription

1 Australian Journal of Ophthalmology. (1981). 9. pp RADIATION DAMAGE AFTER PTERYGIUM TREATMENT* K. H. TARR, FRACS I. J. CONSTABLE, FRACO Abstract In 57 patlents with ocular comphcatms following pterygium treatment and beta /rradiation, scleral and corneal ulcerat/on cataract and pseudomonas endophthalmitis were the most important Prevention and management of these complmtions are discussed INTRODUCTION Beta irradiation after pterygium excision is necessary to reduce the recurrence rate, especially in climates where pterygia are common and the recurrence rate high. Radiation induced pathology of the sclera, cornea and lens after pteygium excision and beta irradiation has been reported, but there has been little emphasis on the long term outlook or visual consequences of these complications. Pterygium excision is a common operation and therefore these complications, although not frequent, are a significant ophthalmic problem and require consideration in the approach to pterygium management. Scleral and corneal ulceration, pseudomonas endophthalmitis and cataract were the major complications in a review of 57 patients with complications of pterygium treatment.* There were 32 males and 25 females, and the age at treatment ranged from 27 to 69 years with the time of assessment 3-20 years later. All but one had fractionated beta irradiation following pterygium excision with a bare sclera technique. Beta irradiation was applied with a strontumgo plaque already described. Sclerrrl und Corned Ulcerrrtion Scleral ulceration after pterygium excision and beta irradiation has been previously reported and occurred in 5% of patients following treatment with 2000 rads of beta irradiation as a single dose. In our patiepts there were 52 scleral ulcers in 46 patients. The dosage is outlined in Table 1. Both the clinical features and the fine structure of the scleral ulceration would indicate beta irradiation as the primary causative agent. In our survey scleral ulceration was surrounded by an area of dense white sclera with absence of conjunctival cover. The adjacent conjunctiva was atrophic with avascular patches and telangiectasia. The similarity in appearance, size, and position of the ulcers (Figure 1) would suggest a common pathogenesis. Ulceration displaced inferiorly in 7% may reflect the point of contact with a strontumgo plaque if a Bell s phenomenon occurred during the application. * Presented iit the combined RACO-OSNZ Conference in Christchurch October, Reprir7r rrqws/s: K. H. Tarr. Sydney Eye Hospital. Sir John Young Crescent. Woolloomooloo, N.S.W., K4I)IATIOh IlA.M4(il- At-TtK PTtKY<:IUM TKtATMtNT 97

2 Figirre I: A typical scleral ulcer. Note the area of exposed white sclera and the avascular conjunctiva with telangiectasia. Figirre 2: Electronmicro raph of the peripherarcytoplasm of a scleral fibroblast. Note the ban& of fine filaments and focal densities (arrows) which suggest an abnormality in formation. (X 21,000). 98 AUSTRALIAN JOURNAL OF OPHTHALMOLOGY

3 Figure 3: Electronmicrograph of human scleral ulceration. Fibrous long spaced collagen is prominent (arrows) and there is a disarray in collagen fibre arrangement. Collagen fibres are re laced by granular electron dense material suggesting degradation. &is electron dense material with vague evidence of periodicity is seen in the inset (X 56,000). Figure 4: Pseudomonas endophthalmitis and scleral ulceration three years after terygium excision and 2400 rads of beta irradiation. (Reproducef with permission from The British Journal of Oph thalmology). RADIATION DAMAGE AFTER PTERYGIUM TREATMENT 99

4 2400 ~ Total Dose. (r ids) ~ TABLE 1 Relationship of Betairradiation Dosase to Scleral Ulceration No of Ulcers I Electron microscopy of 5 scleral ulcers were studied. The scleral fibroblasts were large and stellate and the nuclei large with much euchromatin and prominent nucleoli. The cytoplasm contained peripheral bands of fine filaments with focal densities (Figure 2) suggesting abnormal collagen formation. There was a variation in the diameter and a disarray in the arrangement of the collagen fibres. Fibrous long spaced collagen was prominent and at some sites the fibres were replaced by coarsely granular electron dense material suggesting collagen degradation (Figure 3). Mononuclear phagocytes were present with aggregates of small electron dense material within membrane bound structures. These fine structural changes suggest that collagen production was abnormal in structure and arrangement and susceptible to phagocytosis. Such an appearance is consistent with radiation damage, although morphological features associated with radiation are not unique and may occur following other forms of trauma or ischaemia. Sclera is generally considered very resistent to irradiation. Very high doses, up to 100,OOO rads of beta irradiation to posterior sclera rarely cause necrosis either experimentally or clinically.6 The 11 ulcers that occurred in our series after currently recommended doses of beta irradiation to the anterior segment suggests that an additional factor potentiating necrosis may be present. Surgical damage, an abnormality in the tears or an environmental influence from exposed sclera when there is an absence of conjunctival cover may be additional factors. Faulty surgical technique, particularly cautery, has been implicated. In our survey this could not be substantiated as an important factor, nor were 100 we able to demonstrate deficiency of tears or an abnormal tear film. Our studies would suggest that exposure of the sclera may play a role in the subsequent ulceration. In this respect a striking clinical feature was the absence of tissue cover over the affected sclera and severe changes in the adjacent conjunctiva. Persistent bare sclera with failure of conjunctival regrowth after pterygium excision and beta irradiation has previously been noted and may occur without symptoms in many In 4 of our patients, bare sclera persisted following pterygium treatment for 1 to 7 years before scleral ulceration developed. These findings suggest that failure of the conjunctiva to regrow leaving the sclera exposed, may be the additional factor that potentiates ulceration. When conjunctival regrowth does occur, necrosis of this tissue may be the first event leading to scleral exposure and ultimately ulceration. Therefore bare sclera that remains after pterygium treatment should be observed until conjunctival regrowth has occurred. Persistent bare sclera may be an indication for surgical intervention to prevent subsequent ulceration, if not to restore ocular comfort. The importance of scleral ulceration is that there is a significant risk of infective endophthalmitis. In our survey 2 cases of corneal ulceration was seen nine and ten years after pterygium excision and strontumgo beta irradiation with 3600 and 5000 rads respectively. Both were indolent deep corneal ulcers with necrotic margins and occurred at the site of the previous pterygium head. Tear production and the tear film were clinically normal. Psei idomonas Endoph thnlmit is Infection in eyes with scleral disease is not well reported. No mention is made of infective endophthalmitis in surveys of patients with necrotizing sclerik8 Pseudomonas endophthalmitis in association with scleral ulceration has been reported only once. Four patients had this complication in our survey. In all four, deep scleral ulceration was present and occurred 3-10 years after pterygium excision and a single course of rads of beta irradiation. One patient of particular interest had bilateral scleral ulceration. A scleral graft was applied to one eye only and AUSTRALIAN JOURNAL OF OPHTHALMOLOGY

5 subsequently the fellow eye with persistent ulceration developed pseudomonas endophthalmitis which required evisceration (Figure 4). A second patient also required evisceration. Prompt and energetic treatment that continued for 6 weeks salvased two of the four eyes: one with a visual acuity of 616 and the other with a secondary cataract. The occurrence of endophthalmitis emphasises the importance of surgical repair of radiation induced scleral ulceration. particularly if the ulceration is deep. Crrtrrrutc'r Beta irradiation induced cataract is well documented but is rarely seen with an external dosage of less than 3000 rads9 Usually the cataract is a sectorial posterior cortical opacity with retention of normal visual acuity. This type of lens opacity was seen in 254 of treated eyes in our survey. The total dose of beta irradiation ranged from 2900 to 5200 rads. Compared to patients without cataract. there was no significant difference in age or length of followup but a strong correlation was found with respect to the total dose of radiation. Our survey would therefore confirm that such opacities are unlikely with doses less than 3000 rads. Reduced vision from beta irradiation induced cataract is uncommon and none have been reported after Strontumgo beta irradiation to prevent pterygium recurrences. While nine of our patients had severe visual loss from cataracts or required lens extraction, in only three was beta irradiation clearly implicated. In two a second coiirse of beta irradiation had raised the total dose to 5900 and 7200 rads while the third case had had 4500 rads of fractionated strontum beta irradiation. Cataract as a consequence of treating 'a benign lesion is a serious price to pay and seriously raises the question as to whether a second course of radiotherapy is justified. Col?c.lllsion Our study of late complications of pterygium treatment suggests that a cautious attitude is required in the management of pterygia and to the use of beta irradiation. The complications of treatment especially scleral necrosis and cataract may lead to visual loss. Although beta irradiation is essential for the development of scleral ulceration, it would appear that additional factors are involved and that there may be no beneficial safe dose of irradiaton at which scleral ulceration will not occur in at least some patients. Persistent bare sclera following pterygium treatment may require surgical intervention to prevent subsequent scleral ulceration, and the risk of infection. Deep scleral ulcerations should certainly be grafted to prevent the serious complication of pseudomonas endophthalmitis that may occur. A rknowledgenients We thank Professor F. A. Billson for advice in preparation of this paper for publication and presentation at the Combined RACO and OSNZ conference. References I. Cameron, M E: Pterygium Throughout the World. Springfield, Jlllinois: Thomas Tarr. K H. Constable, J J: Late complications of pterygium Treatment. Brit J Ophthalmol. 64: Cameron, M E: The treatment of beta irradiation necrosis of the sclera. Aust J Ophthalmol. 6: Talbot, A N: Complications of beta ray treatment of pterygia. Trans Ophthalmol Soc NZ Lommatzoch. P K: Morphologische und funktionelle Veranderungen des Kaninchenauges nach Einwirkung von Betastrahlen auf den dorsalen Bulbusabschnitt. Albrecht von Graefes. Arch Klin Exp Ophthalmol , Lommatzoch. P K: Experiences in the treatment of malignant melanoma of the choroid with lohru/ "'Rh beta ray applicators. Trans Ophthalmol Soc UK. 93: , Cameron. M E: Preventable complications of pterygium excision with beta irradiation. Br J Ophthalmol. 56: Watson. D G. Hayreh, S S: (1976) Scleritis and Episcleritis. Br J Ophthalmol. 60: , Hilgers. J,H C: Strontium'" B irradiation cataractogenicity and recurrence. Arch Ophthalmol. 76:329-33,!%i?ium 10. Merriam, G R: The effects of beta radiation on the eye. Radiology. 66: 240-4, KAl>IhTION DAMAGL AI'WR PTtKYGIUM TREATMENT 10 1