Letters

Figure 2 Minimal fluorescein staining of theright eye at 1 week, indicating rapid cornealre-epithelialisation (note the underlying cornea iswhite).

Figure 1 Appearance of the corneas onadmission showing severe corneal burn to theright eye (A); note the lacuna of healthy corneawithin the corneal scar. The left eye demonstrateddiscrete corneal scarring (B); the visual acuitywas countingfingers in both eyes.

alkali injuries with the expected poor progno-sis. The patient was therefore started on

intensive ascorbate, citrate, dexamethasone,with regular antibiotics and mydriatics.On re-examination 24 hours later the

corneal opacities had enlarged slightly butsubsequently remained unchanged. The cor-

nea re-epithelialised over the following week(Fig 2), and 1 month later, when the eye was

stable he underwent a successful left penetrat-ing keratoplasty (Fig 3). Histology demon-strated a deep stromal scar consistent with an

exothermic reaction (Fig 4).

COMMENTVajpayee et al' looked at 59 patients presentingwith thermal corneal burns and found that90% of these injuries occurred at home andinvolved boiling fluids, matches, or fireworks.In 89% the burn was limited to the epitheliallayer and only two needed penetrating kerato-plasty. During prolonged exposure to heat4(for example, during molten metal injuries'),full thickness burns are produced.

In our case fragments of Betonamit pen-etrated into the corneal stroma leading to fullthickness scarring. The patient was lookingdown to examine the drill hole, in this way theupper and central cornea in each eye weremost affected by the explosion.The discrete pattern of corneal damage

suggested that thermal damage was the maincause of corneal damage. Particulate matterpenetrated the cornea and remained incontact during the exothermic reaction. Alkaliinjuries tend to produce a diffuse cornealreaction with delays in corneal epithelialisa-tion as a result of permanent metabolicchanges in the limbal epithelium.' Althoughthe alkalinity of the powder may have contrib-uted to the corneal damage, it was interestingto note that where there was little fluid (suchas on the eyelids) there was little tissuedamage.This case illustrates the hazards of using

these novel cracking agents, but also the rela-tively benign course that combined thermaland alkali corneal injuries follow.

Figure 3 The lft cornea 3 months after cornealgrafting.

Figure 4 Histology of the scarred corneashowing loss of cell nuclei and disorganisedcollagen fibrils.

R S B NEWSOMS LESNICK OBERSTEIN

M G FALCONDepartment of Ophthalmology,St Thomas's Hospital, London

Correspondence to: MrMG Falcon, Department ofOphthalmology, South Wing, St Thomas's Hospital,Lambeth Palace Road, London SEI 7EH.Accepted for publication 1 August 1996

1 Vajpayee RB, Gupta NK, Angra SK, ChhabraVK, Sandramouli S, Kishore K Contact ther-mal burns of the cornea. Can Ophdtalmol1991;26:215-8.

2 Mannis MJ, Miller RB, Krachmer JH. Contactthermal burns of the cornea from electriccurling irons. Am Ophtalmol 1984;98:336-9.

3 Roper-Hall MJ. Thermal and chemical burns.Trans Ophthalmol Soc UK 1965;85:631-53.

4 Shahan WE, Lamb DH. Histologic effect on theeye. Am Ophthalol 1916;33:225.

5 Thoft RA, Friend J. Biochemical transformationof regenerating ocular surface epithelium. Oph-thalmol Vis Sci 1977;16:14.

Balloon cell naevus ofthe caruncle

EDrroR,-Melanocytic naevi composed pre-

dominantly of balloon cells, are quite uncom-mon in the slin and even more rare in theconjunctiva. Histologically, balloon cells differfrom ordinary naevus cells in that they arelarger (20-40 pm in diameter), possess a cen-tral nucleus with abundant clear or finely

granular cytoplasm, and lack obvious cyto-plasmic melanin. Ultrastructurally, the clearcell cytoplasm is due to vacuolar degenerationand subsequent coalescence of abortivemelanosomes that do not contain melaninpigment.We present the first case ofballoon cell nae-

vus of the caruncle and discuss the differentialdiagnoses.

CASE REPORTA 16-year-old girl presented with a 0.4 x 0.2mm, brownish, and apparently cystic lesion inthe left lacrimal caruncle. No other similarlesion was noted in the eyelids or elsewhere.The serum lipid level was normal. The lesionwas excised, formalin fixed, and processed toparaffin embedding.

Special histochemical stains includedperiodic acid-Schiff (PAS), colloidal iron, andAlcian blue. No stains for lipids were per-formed owing to lack of a wet tissue specimen.Immunohistochemical studies were per-

formed with monoclonal antibodies againstHMB-45 and human macrophage CD68(Dakopatts), HAM56 (Enzo Diagnostics) andpolyclonal sera against alpha-l-antichymotrypsin, S-100 protein, lysozyme(Dakopatts). Antibody attachment was identi-fied using a standard avidin-biotin-peroxidasetechnique, with the enzyme label being visual-ised as the red final reaction product ofaminoethylcarbazole.

Microscopically, haematoxylin and eosinstained sections showed tissue lined bynon-keratinising epithelium with goblet cells,consistent with conjunctiva. The substantiapropria contained a population of polyhedralclear cells with a centrally placed, blandnucleus; occasional cells appeared to be binuc-leated (Fig 1). Further sections cut at a deeperlevel revealed a thin rim of characteristic nae-vus cells, with the formation of few nests,overlying the clear cell component. The clearcells stained weakly positive with PAS andAlcian blue reaction and strongly positive withcolloidal iron for acid mucopolysaccharides.Immunohistochemical stain for S-100 pro-

tein was positive in both the naevus and clearcells, while a polyclonal antibody to alpha-l-antichymotrypsin stained the balloon cellsonly. No positivity to histiocyte markers(HAM-56, CD68, lysozyme) and activatedmelanocytes (HMB-45) was observed in thelesion.

COMMENTBalloon cells do not appear to be as rare in theeye as they are in the skin, having beenobserved in approximately 4% of a large seriesof naevocellular naevi of the choroid,' and in10% of the uveal melanomas.' Nevertheless,only two cases of conjunctival naevi with bal-loon cells have previously been reported in theliterature,3 4 neither involving the caruncle. Of48 caruncular naevi diagnosed at the EyePathology Laboratory of the Wilmer Institutein Baltimore during a 52 year period, nonepossessed a clear cell component.'

Although the presence of balloon cells doesnot appear to have any intrinsic clinical signifi-cance, their occurrence in benign or malignantlesions is interesting because it increases thepotential for histological misdiagnoses, particu-larly when the site of occurrence is uncommon.In the absence of an obvious melanocytic cellpopulation, planar xanthomata and balloon cellnaevi can be differentiated since only the formercontain fat. Balloon cells, as opposed toxanthoma cells, stain positively with histochemi-

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Letters

cal methods for acid mucopolysaccharides, suchas colloidal iron and Alcian blue. Masson-Fontana stain for melanin pigment may alsooccasionally prove positive in a few balloon cells.Other differential diagnoses should include, inthe ocular context, sebaceous adenoma, granu-lar cell tumour, clear cell hydradenoma, andmalignant clear cell neoplasms. In granular celltumour, the cytoplasm can also look clearalthough at high power it is usually finely granu-lar. Features more in keeping with a diagnosis ofballoon cell naevus in this case are the absence ofimmunoreactivity to panmacrophage markers(granular cell tumour are often positive) and thepresence of characteristic naevus cells adjacentto the main lesion. Adnexal tumours could beruled in or out of the diagnosis on the basis ofcytokeratin staining.

IRENE PECORELLAANTONIO CIARDI

Dipartimento di Medicina Sperimentale e Patologia,Universita degli Studi di Roma 'La Sapienza',

Rome, Italy

SANTI MARIA RECUPEROII Cinica Oculistica, Universita degli Studi di Roma

'La Sapienza', Rome, Italy

Figure 1 Caruncular compound naevus, predominandy composed oflarge, clear cells. Towards thesurface, small melanocytes with theformation offew nests can be recognised. Haematoxylin andeosin, x 250.

Correspondence to: Dr Irene Pecorella, Diparti-mento di Medicina Sperimentale e Patologia,Policlinico Universitario 'Umberto I', Universitidegli Studi 'La Sapienza', V le Regina Elena,324-00161 Rome, Italy.

Accepted for publication 13 September 1996

1 Naumann G, Yanoff M, Zimmerman LE.Histogenesis of malignant melanomas of theuvea: I Histopathologic characteristics of nevi ofthe choroid and ciliary body. Arch Ophthalmol1966;76:784-96.

2 Riley FC. Balloon cell melanoma of the choroid.Arch Ophthalmol 1974;92:131-3.

3 Folberg R, Jakobiec FA, Bernardino VB,Iwamoto T. Benign conjunctival melanocyticlesions. Clinicopathological features. Ophthal-mology 1989;96:436-61.

4 Pfaffenbach DD, Green WR, Maumenee AE.Balloon cell nevus of the conjunctiva. Arch Oph-thalmol 1972;87:192-5.

Bone formation in rejected corneal graft

EDrrOR,-Intraocular bone formation is a wellknown phenomenon that occurs mainly inlong standing phthisical eyeballs.' Presence ofbone was reported also in cases of epibulbarosseous choristoma' as well as in scleras of apatient with chronic renal failure.3 We present,to our knowledge for the first time, boneformation in the cornea.

CASE REPORTA 47-year-old woman, known to suffer fromcongenital glaucoma, had bilateral completelyopaque large corneas. She had been treated inanother hospital at the age of 15 years, under-going corneal graft in her left eye, but the graftopacified soon after surgery.

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In her first visit in our eye clinic her visualacuity was no light perception in the right eyeand light perception in the left eye. Both cor-neas were completely opaque and vascularised(Fig 1), and the retrocorneal parts of the eyescould not be examined. Ultrasound examin-ation of the left eye revealed an axial length of31 mm and dislocated lens in the vitreous.Because of the potential for vision in the lefteye, perforating keratoplasty was performedunder local anaesthesia; the recipient cornealbutton was sent for histopathological evalua-tion. Four months after surgery the correctedvisual acuity of the operated eye was fingercounting from 1 metre. The cornea was clear,enabling visualisation of the fundus thatshowed almost total cupping of the opticnerve head. The patient has been treated byantiglaucomatous drugs and topical andsystemic corticosteroids.The specimen that was submitted to our

ophthalmic pathology laboratory consisted ofa completely opaque and thickened cornealbutton measuring 7 mm in diameter. In

cutting the cornea with the microtome, it wasfound to be hard; therefore, we performeddecalcification. Microscopic examination re-vealed scarred, vascularised, and inflamedcorneal tissue with irregular epithelium andalmost no Bowman's layer. Areas of calcifica-tion were seen in the superficial corneal layers,some in the form of band keratopathy andothers as large calcified stromal areas. A largepiece of bone formation with fibrovascularbone marrow was located in the deeperstromal layers (Fig 2). Another small piece ofbone was seen more superficially. The De-scemet's membrane was broken and folded,and thick fibrous tissue was seen behind it.Some melanin pigmentations (Fontana stain-ing positive; PERLS staining negative) werefound in the posterior stromal layers.

COMMENTIn a large series' of 2486 enuculated eyes,4.8% had intraocular ossification. In 69% ofthem marrow was found within the hetero-

Figure 1 Clinical picture showing thecompletely opaque and vascularised right cornea,and the opaque corneal graft in the left eye.

Figure 2 Histological section of the cornea showing superficial vascularisation and calcifications,and two layers of bone tissue with bone marrow in the deep stromal layers (haematoxylin and eosin,x 40).

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