IAN ROBERTSOK, smaller grafts with closer sutures. He found D.O., F.R.A.C.S., least astigmatism in grafts of 6 mni. diameter The Royal Victorian Eye and E’ar Hospital, using direct sutures a t 1 .5 mm. intervals. Melbourne. No grafts in his series were performed with

continuous sutures. Trontman and Meltzer SUMMARY (1972) reported that least astiamatism

occurred when grafts were performed with unpredictably in many cases after kerato- plasty. ‘a high cylindrical lenses Astigmatism may exist prc-operatively, or hard contact lenses to be to particularly in keratoconiis, itlid mill be create good visual acuity. detected if keratometry is performed routinely.

The contour of the donor C’OrIleit may also be

to reduce astigmatism during corneal surgery. in the graft. A large proportion of ;&stigma-

AsTIGMnTrsnl Occurs and double continuous monofibment sutures.

A new device is described which is designed

It is likely that this procedure may reduce the final astigmatism which results

significant in the prodllctioll ()f &igmatism

tism still oc(>ups during surgery ;~lld is due to poorly placyd or spa(teC1 s11tnrcs or unevenly distributed tension in the continuous mono-

The factors prodiicing operative corneal filament sutllrc,s. AstigmihtjsI,l also occur after corneltl ilavc. ~ ~ c . c . l l rc.moved.

after corneal sutures have been removed.

astigmatism are reviewed and methods used to reduce this post-operatively are discussed. Various methods of snlintirle ill,(i monlfing

INTRODUCTION Clear grafts can be expected in a high

percentage of penetrating keratoplasties per - formed today. Post-operative astigmatism, however, frequently occurs despite efforts to reduce it. Accurately placed 10-0 mono- filament sutures using precise microsurgical techniques still produce high degrees of astigmatism, as no optical control is used at the time of inserting and pulling up of sutures. Troutmaii (1973) states that eight per cent of clear corneal grafts in his series have visually debilitating astigmatism. He recommends routine lieratometry before, during and after grafting. He has performed sector wedge resection of the edge of the graft to correct severc. astigmatism (4 .0 dioptres or more) after the sutures have been removed. Most of his patients in this series had keratoconus. Lesser degree8 of both regular and irregular astigmatism are more common after keratoplasty and these patients must wear cylindrical spectacle lenses or hard contact lenses to have good visual acuity.

Ruben (1969) found that astigmatism varied from 2 . 5 to 7 .5 dioptres after penetrat- ing keratoplasty and was reduced by doing

the cornea have been i;sed, s&li ;IS the fusi fitting shells of Ridley i\vntl Ainslie (Ruben,

Fiy. 1.

1969). It is doubtful wlietlicr these methods have a permanent efY(1c.t on moulding :I graft to a perfect optical shape.

It seems obvious that more rtfort should be made to reduce astigmatism in the graft at the time of the operation using optical control. The difficulty in using it keratomcter during keratoplasty is that the instrument must be

coiistaritly interchanged with the operating microscope as the final adjustments of the corneal sutures are made. This manauvre is time consuming and cumbersome and there- for a simple coaxial device has been made which can be rapidly attached to the objective of the microscope.

A Placido disc, consisting of the usual :tltornating concentric rings of black and white, was made to fit over the end of any Zeiss operating microscope objective. The appar- i1t11~ can be sterilized and is easily attached to the microscope by elastic loops when the continuous sutures have been inserted in the Cornea. The diameter of the disc was 1 7 cm., as smallcr sizes produced tiny corneal images anti 1;trgw discs obscured the operative field. illiimination of the disc was provided by an

Fix. 2.

inwrtrtl iitlj ust;tble lamp, placed close to the micmscopc stand, in order to produce a clear image of the disc in the patient's cornea. A self -ilhiniinating disc has been made using a rnig of reti light-emitting diodes, but the microscope light was too bright to allow a sufficiently clear image of the disc to appear in thc cornea. A more intense light source,

such as circular fluorescent lights mounted on the Placido disc, would be better. On the other hand, individual lights placed around the disc a t regular intervals may act as a guide for inserting continuous or interrupted sutures a t regular intervals.

The instrument can be used as a photo- keratoscope before, during and after corneal surgery as i t can be slipped over a camera lens and adequate lighting may be provided by a second electronic flash gun triggered by a " slave " unit pointed towards the disc and held to one side of the patient's head. Figure 2 shows a photograph taken of a normal cornea using this method.

CONCLUSIOXS At the present time, no optical control is

available during keratoplasty. A simple device is described which can be easily attached to the operating microscope and should assist in the reduction of the astigmat- ism during keiatoplasty. It is ;tnticip:it,ed that better visual results will ensue.

ACKKOWLEDGEMEXTS I wish to thank Mrs. G. van deli Brenk,

Senior Medical Photographer and Miss J . Quilter, Librarian of The Royal Victorian Eye and Ear Hospital for their assi8tanc.e.

REFERENCES RUBEN, M. (1969), In Corneo-I'lastzc Surgery,

Proceedings of thc Second International Corneo- Plastic Conferenco, July 1967 (Editor: P. V. Rycroft), Pergamon Press, Oxford, 525.

RUBEN, M. (l969), I n Rycroft, P. V. (Ed.), op. a t . , 527. TROCJTMAN, R. C. (1973), " Microsurgical Control of

Corneal Astigmatism in Cataract and Kcrato- plasty ", Trans. Amer. Acad. Ophthnl. Otolaryng., 77 : OP-563.

TROUTMAN, R. C., and MELTZER, &I. (1972), " Astigmatism and Myopia In lirratoronuq ", Trans. Amer. Ophthal. SOC., 70 : 265.

OP'IWAI, CONTILOL IN KYRATOPIASTY 153