Brit. . Ophthal. (I975) 59, 586

Corneal rust removal by electric drillClinical trial by comparison with manual removal

NICHOLAS BROWN, RICHARD CLEMETT, AND RODNEY GREYFrom the Department of Clinical Ophthalmology, Moorfields Eye Hospital, London

The rusty ferrous corneal foreign body is a commonreason for attendance at casualty departments.Improved efficiency in the treatment of this con-dition would reduce both the clinician's timespent with each patient and the patient's time offwork.

Rust has a toxic effect on the corneal stroma, andif left in situ, after removal of the foreign body therust-stained tissue undergoes necrosis and sloughs.Early removal of all rust without damage to thecornea is therefore the aim of any form of treatment.

Medical treatment in the form of local Des-ferrioxamine has been used in the hope of removingrust without causing any stromal destruction. Aclinical trial to test Desferrioxamine against surgical(manual) removal, and against expectant treatment(McGuinness and Knight-Jones, I968), showedthat surgical removal was significantly better thanDesferrioxamine, and that Desferrioxamine wassignificantly better than expectant treatment.Other studies of Desferrioxamine (North, I970;Valvo, I967; and Wise, I966) demonstrated theusefulness of this treatment, but have not shown itto be superior to surgical treatment.

Rapid complete surgical removal with minimaltrauma to the comea can at present be expected tooffer the best form of treatment. The electric drillwas introduced for this purpose and has beenimproved in design in recent years. The firstdescription of an electric drill for corneal rustremoval appears to be that of Witzeman (1936).Other instruments have been described (Hardesty,I965; Soukup, I968; and Worst, 196I). All theseinstruments rotate dental burrs.The manually rotated dental burr has also been

advocated (Grossmann, 1950), and was the methodin use at this hospital before the introduction of anelectnrc drill.

Before the drill is applied to the cornea, theforeign body needs to be lifted off by a Bowmanneedle, but syringe needles have been advocatedfor their convenience (Applebaum, 1943; andHarding, 1943). A disposable syringe needle isnow preferred.Address for reprints: N. Brown, Department Clinical Ophthal-mology, Moorfields Eye Hospital, City Road, London ECIV 2PD

In spite of the number of corneal electric drillsdescribed, there appears to have been no clinicaltrial of their performance. A study is now reportedin which electric drill rust removal is comparedwith manual removal. Design criteria for electricdrills are also considered.

Materials and methods

INSTRUMENTS

After experience with a prototype instrument, a newslim electric drill (Fig. i) which can be held in the handlike a pencil has been built to our design. It has a springfriction chuck to hold dental burrs and is operated bylight finger pressure from any side on a ring. A brake isincorporated so that the drill stops rotating very soonafter the operator's finger is lifted, which is consideredto be a useful safety feature.The drill is advanced obliquely to the eye so that the

side and not the pole of the dental burr works on thecornea. In this position the operator has the best controlof the cutting pressure and of the depth of excavationof the cornea. For this reason a straight drill is betterthan one with an angle between the handle and theaxis of the drill shaft.

SELECTION OF PATIENTS

Patients were selected from those making their firstattendance at the casualty department at MoorfieldsEye Hospital, without having received treatment else-where. All patients included had significant corneal rustwith or without the ferrous foreign body still present.Patients with insignificant corneal rust were excludedas it was considered that they would soon improve witheither form of treatment and so dilute the result of thetrial.

Altogether 121 patients entered the trial, of whom 64received electric drill treatment, and 57 manual treat-ment.

CONDUCT OF THE TRIAL

The doctor who made the decision to include the patientin the trial did not himself perform any treatments, butgave each patient an envelope containing a card on whichwas printed either 'Drill' or 'Manual'. The patient wasthen treated in a separate room by one of the threeauthors according to the written instruction.

copyright. on D

ecember 3, 2020 by guest. P

rotected byhttp://bjo.bm

j.com/

Br J O

phthalmol: first published as 10.1136/bjo.59.10.586 on 1 O

ctober 1975. Dow

nloaded from

Corneal ruist removal 587

FIG. i Hand held electric drill

with dental burr

The patients were instructed to return each day for

follow-up until their condition had healed. They were

examined at follow-up by the doctor who had first

seen them and who was unaware which treatment they

had received. If he considered that further rust removal

was indicated, the patient again received the same

method of treatment as on the first occasion.

A brief proforma was used for each examination.

This included the patient's name and study number,

number of attendances, presence of pain, drawing of

corneal rust, drawing of epithelial lesion, and record

of stromal oedema and anterior chamber activity.

METHOD OF TREATMENT

M~anual

Manual treatment is conducted in a manner which is

traditional in this hospital. The eye is anaesthetized

with Amethocaine drops i per cent. The patient is

seated at the slit lamp and the ferrous foreign body, if

present, is lifted off with a 40 mm x o-8 mm disposable

syringe needle. A sterile dental burr is then held between

the thumb and index finger and rotated against the

cornea. The eye is treated with Hyoscine drops I per

cent, Oc. Chloramphenicol i per cent and protected bya pad and knitted shield.

Electric drillThe patient is prepared as for manual removal andseated at the slit lamp. The ferrous foreign body islifted off and the dental burr applied by the electricdrill. Drilling is continued until all the rust stain isremoved. Medicaments and padding are applied asabove.

Results

The results are presented in the Table. The smallerrust rings were easily removed by either manualor electric drill treatments. Large deeply infiltratedrust rings were difficult to remove completely bymanual rotation of the dental burr. The morecentral parts of the rust ring were in soft necrotictissue, that were easy to remove, but the peripheralpart of the ring was found to be in firm stromaltissue, which was not easy to remove. Persistencewith manual removal at this point caused an irre-gular breakup of the crater. This led to incompleteremoval in several patients (Table), which resultedin further treatment being needed at their nextattendance when the rust ring had increased indiameter.There was no difficulty in removing the complete

rust ring at the first treatment using the electricdrill. The drill cut cleanly in firm cornea and underslit-lamp control it was easy to remove all the rustand to avoid removing healthy cornea beyond thering. This left a smooth crater (Figs 2-4), whichcontrasted with the irregular crater after manualremoval. With slit-lamp control, the electric drillwas found to be entirely safe and there were noinstances of unintentional corneal excavation.

Table Results of clinical trial comparing patientstreated manually with those treated zwith anelectric drill

Details Drill Manual

Total number of patients treated 64 57Mean treatment time (seconds) 70 i62Percentage of patients requiring

second treatment o 9 4Mean duration of attendance

(days) 3.I8 3.84Mean persistence of pain (days) Oo02 o064Mean persistence of rust (days) o-Io o083Mean epithelial healing time

(days) 2.45 2-87Mean time for clearance of

stromal infiltrate (days) I43 I-90

copyright. on D

ecember 3, 2020 by guest. P

rotected byhttp://bjo.bm

j.com/

Br J O

phthalmol: first published as 10.1136/bjo.59.10.586 on 1 O

ctober 1975. Dow

nloaded from

588 British Journal of Ophthalmology

FIG. 2 Corneal macrophotograph offerrous foreignbody in situ

FIG. 3 Same eye. The ferrous foreign body has beenlifted off leaving rust ring

FIG. 4 Same eye. The rust ring has been removed byelectric drill. The slit beam shows a smooth-sided crater

The numerical results (Table) show that thedrill was better for every measurement, but insome parameters with a poor degree of statisticalsignificance.No patient who was treated with the electric

drill required a second treatment, whereas fivepatients (9.4 per cent) of those manually treatedrequired a second treatment.The mean duration of attendance was less for the

patients treated by electric drill (3 I 8 days comparedwith 3-84 days, which is barely significant (P=0o2)).Persistence of pain was significantly shorter in thegroup treated by electric drill (mean o-02 dayscompared with o-64 days for manual removal). Thetime for epithelial healing was not significantly lessin the drill group (P=o04). The electric drilltreatment took less than half as long as the manualtreatment.

Discussion

The present study shows that corneal rust removalby electric drill is more efficient than manualremoval. McGuinness and Knight-Jones (I968)showed manual removal to be better than treatmentby Desferrioxamine; they concluded that Desfer-rioxamine should still be used if proper facilitiesfor manual removal were not available. Both elec-

copyright. on D

ecember 3, 2020 by guest. P

rotected byhttp://bjo.bm

j.com/

Br J O

phthalmol: first published as 10.1136/bjo.59.10.586 on 1 O

ctober 1975. Dow

nloaded from

Corneal rust removal 589

tric drill removal and manual removal should beperformed at the slit lamp, so where this instru-ment is not available Desferrioxamine should stillbe considered.

Conclusion

The dental burr rotated by an electric drill is thequickest, safest, and most precise forn of treatrnentfor comeal rust rings. It enables complete removalof the corneal rust at a single treatment and leavesa smooth crater that is no larger than the originalrust ring. Pain relief is more rapid after electricdrill removal; this is probably related to the com-

plete removal of the rust. Epithelial and stromalhealing are marginally faster than after manualremoval and the patients' duration of attendanceis less.The ideal drill is a slim straight instrument,

which rotates dental burrs and is operated by alight finger pressure. A brake which stops drillrotation on lifting the finger is a useful safetyfeature.

We should like to thank Professor Barrie Jones for hisadvice and encouragement in initiating this study andthe staff of the Dental Workshop at University CollegeHospital for their engineering skill.

References

APPLEBAUM, A. (I943) Arch. Ophthal. (Chicago), 30, 262GROSSMANN, E. E. (1950) Amer. 5'. Ophthal., 33, 293HARDESTY, H. H. (I965) Ibid., 6o, 526HARDING, G. F. (I943) Arch. Ophthal. (Chicago), 29, I34MCGUINNESS, R., and KNIGHT-JONES, D. (I968) Brit. Jt. Ophthal., 52, 777NORTH, P. J. (1970) Ibid., 54, 498SOUKUP, F. (I968) (s. Oftal., 24, 146VALVO, A. (I967) Amer. _t. Ophthal., 63, 98WISE, J. B. (I966) Arch. Ophthal. (Chicago), 75, 698WITZEMAN, L. A. (1936) Ibid., I6, 857WORST, J. G. F. (I96I) Amer. 5'. Ophthal., 52, 122

copyright. on D

ecember 3, 2020 by guest. P

rotected byhttp://bjo.bm

j.com/

Br J O

phthalmol: first published as 10.1136/bjo.59.10.586 on 1 O

ctober 1975. Dow

nloaded from