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Photocoagulation for DiabeticRetinopathy

THE LANCET

THE narrow beam of intense white light from thexenon arc was first used in the treatment of diabetic

retinopathy by MEYER-SCHWICKERATH in 1959.1Since then, many thousands of diabetics have beentreated by this comparatively simple technique,and modifications employing monochromatic,coherent laser emission-notably, the green-lightargon laser2 useful for its very narrow beam and its

preferential absorption by red-cell hæmoglobin—are still being evaluated. Despite widespread appli-cation of this treatment and some strong advo-

cacy,3-S the varied manifestations and the episodic,unpredictable progression of diabetic retinopathyhave made it difficult to define the indications andassess the value of the treatment. Serious visual

disability due to diabetic retinopathy is a leadingcause of blindness among middle-aged people inBritain6 and a few years ago was estimated by theCommittee on Blindness of the British Diabetic As-sociation to be the cause of visual loss in about1500 people a year in the U.K. Pituitary ablation,the sole active form of treatment for which some

advantage had been shown, 9 was applicable onlyto a small, highly selected subgroup of younger,reasonably fit diabetics with retinopathy suffi-

ciently advanced to justify a procedure itself carry-ing a substantial risk to health and life but not sofar advanced that retinal changes were irreversible.Otherwise, apart from last-ditch attempts to slowprogression of retinopathy by rigorous improve-ment of metabolic "control" of the diabetes, theclinician could do little but wait for the inevitablesuccession of events-in younger patients, usuallyrepeated hæmorrhage, retinovitreous vasoprolifer-ation, and fibrosis and in older patients, advancingmaculopathy-that would usher in blindness.A preliminary, two-year report in the April,

1976, issue of the A -merican Journal of Ophthalmo-

1. Meyer-Schwickerath, G. Bucherei Augenarztes, 1959, 33, 1.2. L’Esperance, F. A. Trans. Am. Ophthal. Soc. 1968, 66, 828.3. Dobree, J. H., Taylor, E. Trans. Ophthal. Soc. U.K. 1968, 85, 313.4. Okun, E., Johnston, G. P. in The Treatment of Diabetic Retinopathy (edited

by M F. Goldberg and S. L. Fine); p. 523. U.S.P.H.S. Publication no.1890, Washington D.C., 1969.

5. Rubinstein, K., Myska, V. Br. J. Ophthal. 1972, 56, 1.6 Sorsby, A Rep. publ. Hlth med. Subj. no. 28, 1972.7. Report on Diabetic Blindness in the United Kingdom. British Diabetic As-

sociation, 1969.8 Lundbæk, K., Malmros, R., Anderson, H. C., et al. Excerpta med. int.

Congr. Ser. 172 (edited by J. Ostman). Amsterdam, 1969.9. Kohner, E. M, Joplin, G. F., Cheng, H., Blach, R., Fraser, T. R. Trans.

Ophthal. Soc. U.K. 1972, 92, 79.

logy’O gives the strong support of a well-organisedclinical trial to the advocates of photocoagulationin diabetic retinopathy. Confined to patients withvasoproliferative changes in at least one eye orsevere non-proliferative changes in both eyes, thetrial confirms the grim prognosis for vision in eyesso affected. Taking the group as a whole, however,it strongly suggests that photocoagulation will

approximately halve the risk of catastrophic visualloss. 1732 patients with the retinal changes de-scribed above but with visual acuity of 20/100 orbetter in both eyes were enrolled in a 15-centre

study, directed by an executive committee headedby Dr MATTHEW DAVIS, coordinated by the Univer-sity of Maryland, and generously financed by theU.S. Department of Health, Education and Wel-fare. One randomly selected eye of each patient wassubjected to treatment with xenon-arc or argon-laser photocoagulation (also chosen randomly); theother, untreated eye was observed as the control.Aimed, focal coagulation of surface new vessels, in-cluding those on the optic disc when the laser wasused, or extensive scatter coagulation of the retina("pattern bombing" or "retinal ablation") wereemployed. An important end-point in the two-yearanalysis was "severe visual loss", defined as visualacuity less than S/200 at two or more consecutive,four-monthly follow-up visits. It occurred in 9.4%of untreated eyes and in 4. 1% of treated eyes, a dif-ference very highly unlikely to have arisen bychance. Some evidence of visual recovery in these

badly affected eyes was recorded about twice asoften in treated as in untreated eyes. Analysis ofthe initial appearance of the eyes from retinal

photographs supported the clinical view that severevisual loss was likely when neovascularisation wasclassified as moderate or severe (particularly whenit involved the optic disc) and most likely of allwhen these changes were accompanied by freshhæmorrhage. Treatment effects were so striking inthese most vulnerable groups that the trial

organisers have felt constrained to modify the pro-tocol and recommend treatment for control eyes. Ina large number of eyes with neither neovascularisa-tion nor haemorrhage, presumably the fellow eye ofone more severely affected which qualified the pa-tient for the trial, the cumulative rate of severevisual loss over two years was only 2-1% in un-treated and 2-9% in treated eyes. Inevitably with adestructive treatment like photocoagulation, therewas a price to be paid for prevention of severevisual loss. Minor losses of acuity (2-4 lines of testtype) were more frequent in treated than in un-treated eyes, though after two years the differencewas very small (13.0% versus 10.5%). There wasalso some sacrifice of visual field, more so with thexenon-arc than with the argon-laser treatment.

10. Diabetic Retinopathy Study Research Group. Am. J. Ophthal. 1976, 81,383.

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There were, however, hints that the xenon arc wasalso more effective than the argon laser in preserv-ing vision. Some would take that paradox to sup-port the argument that the more substantial retinalablation also removes more of the source of a

pathogenic factor which drives the retinopathyonwards.

In the older, usually non-insulin-dependent dia-betic, vasoproliferative retinopathy is uncommonand it is the more extensive variants of "back-

ground" retinopathy which threaten vision. An in-terim report on the results of a small multicentretrial, sponsored by the British Diabetic Associ-

ation,11 was restricted to older patients with dia-betic maculopathy. In 76 patients with both eyesroughly equally affected with retinal hxmorrhages,exudates, and macular oedema with visual acuity of6/9 or less, or with circinate hard exudate involv-ing the macular region with vision better than 6/9,a randomly selected eye from each patient was sub-mitted to xenon-arc photocoagulation appliedlocally to lesions lateral to the macula, more

generally to all visible lesions, or to the centre ofcircinate exudates. More control eyes (18) thantreated eyes (8) deteriorated to blindness over a fol-low-up period of up to three years. The mean slow-ing effect of treatment on the rate of deteriorationof visual acuity was statistically significant but

small, with no obvious trend to increase with pass-ing time and most evident in patients with interme-diate degrees of visual deficit at baseline. The de-sign of this trial was good but its scale hardlyadequate to answer its primary questions.

So we now seem to have a simple, low-risk treat-ment which will, in the short term at least, delayvisual deterioration in diabetic retinopathy in pa-tients with retinal neovascularisation, especiallywhen this is more than slight and when it is accom-panied by retinal haemorrhage, and also perhaps inolder patients with maculopathy. In "ordinary"background retinopathy risk to vision is low anduninfluenced by photocoagulation. To take advan-tage of this new information (and to react promptlyto further developments) we should consider redep-loying our clinical resources. A first step should bethe repeated, systematic ophthalmoscopic screeningof patients under adequate conditions of mydriasis,and at intervals determined by the retinal appear-ance and by the type and duration of diabetes. Averification stage for questionable lesionsshould probably include fluorescein retinal angio-grams which show up small tufts of new vesselswhich may escape ordinary clinical examination.Referral of patients with treatable lesions to an

ophthalmologist with access to a photocoagulatorshould follow without delay, and treatment byaimed photocoagulation, retinal ablation, or both(and to include new vessels on the disc where the

11. Interim Report of a Multicentre Controlled Study. Lancet, 1975, ii, 1110.

argon laser is available) should be performed. Aplanned schedule of follow-up observations andadditional coagulation completes the schema.Where all of this cannot be done within a singlehospital, ad-hoc district, area, or even regional ar-rangements should be made. We must not overlookthe anxiety of the patient for his vision as heobserves the increased interest and activity centredon his eyes. Nor must we sweep into this system pa-tients with retinopathy unsuitable for treatment.For simple background retinopathy we can andneed do little but observe and improve diabetic con-trol. When extensive retinal or pre-retinal fibrosisis already present, photocoagulation may acce-

lerate contraction and hasten retinal detachment.

Very occasionally vitreous haemorrhage may occursoon after treatment, especially if large venouschannels are too closely approached. Diabetic

retinopathy is the most readily visible and clinicallyeloquent manifestation of a process which is pro-gressing in other tissues and organs, not least therenal glomerulus. Enthusiasm for photocoagula-tion, a destructive process and clearly not the endof the road in the treatment of diabetic retino-

pathy, should not deflect more general efforts to

prevent diabetic microvascular disease. This aspir-ation may well defy fulfilment until we have madea deeper penetration into the continuing mystery ofthe causation of diabetic microangiopathy.

The Future of Community MedicineTHE specialty of community medicine emerged

in Britain from a union of the Todd Commissionon Medical Education, the Hunter Working Party,and the reorganisation of the National Health Ser-vice. A turbulent infancy and childhood aré almostinevitable since each of the three parents has dif-ferent expectations of the child. And already we arehearing the cries of doom and disaster.

Before and even after Todd, medical studentsseldom opted for careers in public health or com-munity medicine, and there is concern that the

quality of entrant to the specialty is poor. Thisweek Dr HEATH and Dr PARRY (p. 82) put forwardsome ideas on the future of community medicineand they make a valuable contribution in the

emphasis they put on proper manpower planning.Perhaps the figures they cite, with their promise ofrapid promotion for the able, will encourage moredoctors to choose this sphere. HEATH and PARRYdo, however, seem to overlook some of the seriousproblems which community medicine has to tackle.The first concerns role and identity. The Hunterworking party slightly confused the issue by con-centrating on management aspects. In fact, only