British Journal of Ophthalmology, 1986, 70, 402-410

I. Cataract surgery: interim results and complicationsof a randomised controlled trialOXFORD CATARACT TREATMENT AND EVALUATION TEAM (OCTET)*

SUMMARY A randomised controlled trial in progress for more than five years, with no loss tofollow-up (except death), assessed 333 eyes treated by three methods of cataract surgery. Theywere (A) intracapsular extraction and contact lens usage, (B) intracapsular extraction andimplantation of an iris supported lens (Federov I), and (C) extracapsular extraction andimplantation of an iridocapsular lens (Binkhorst 2-loop). The purpose of the paper is to reportinterim visual results, complications, and corneal endothelial cell loss. More eyes in groups A(contact lens) and C (extracapsular+implant) achieved better visual acuity than in group B(intracapsular+Federov lens), which also had more postoperative complications. Both implantgroups lost more endothelial cells than the non-implant group, which did not differ significantlyfrom group B before one year.

A randomised controlled clinical trial on cataractsurgery was started in 1980 at a time when there wasgeneral uncertainty whether intracapsular or extra-capsular extraction was the better method for remov-ing cataracts and whether the potential risks of lensimplantation would outweigh the benefits, sincecontact lenses can be used as an alternative in thecorrection of aphakia.'The practice at the time was strongly influenced by

the published works of Binkhorst, and the mostwidely used. intraocular lenses were iris supported.2As it is clearly impracticable to have too manyrandomization categories in a clinical trial of this

*PARTICIPANTS: Principal investigators: H Chcng, K McPhcrson,'A J Bron. Contributing surgeons: H Cheng, D Boase, G Bell.Anacsthetist: R Fordham. Research fellows: N Price, P Jacobs,M Noble, S MacLennan, A K Bates. Consultant in contact lenses:J Kcrsley. Independent review committee: A R Elkington,'M Ruben,4 J Mann,' A Ridgway.' Computer programmer: L Jones.Photographer: D Barbour. Contact lens practitioner: D White.Opticians (optometrists): U O'Beirn, C Lydon. Nurse technician:A Ambrose. Trial administrators: M Platts, K Smith. TRIALLOCA I ION: The Eye Hospital, Oxford.

'Department of Community Medicine and General Practice, OxfordUniversity, Oxford.2Harley Street, London.'Department of Ophthalmology, Southampton University.4Moorficids Eye Hospital, London.'Manchester Royal Infirmary, Manchester.

Correspondence to Mr H Cheng, FRCS, The Eye Hospital, WaltonStreet, Oxford OX2 6AN.

nature, it was possible to test only one style ofimplant in each category of treatment, and the lenseschosen were the Binkhorst 2-loop iridocapsular lensfor extracapsular extraction and a modifiedBinkhorst 4-loop lens for intracapsular extraction(the Federov I lens). The Federov I lens was chosenbecause the participating surgeons were alreadyfamiliar with this lens and had used it for more thanfive years' and because it was widely used in theUnited Kingdom at the time. The Shearing type ofposterior chamber lens was not yet widely known.

It was appropriate to compare lens implantationwith conventional intracapsular surgery and the useof contact lenses, which would eliminate the opticaldisadvantages of aphakic spectacles. If contact lensescould be fitted and tolerated universally, there wouldscarcely be a need for lens implantation. The choiceof the type of contact lens, however, need not berestricted, since they can be and are freelyexchanged, provided the best techniques andmaterial are available to the patients in the study.Although a reversal of trends has occurred in

relation to the number of iris supported and posteriorchamber lenses used,4 the latter is by no meanstrouble free.' There are many patients fitted with irissupported lenses who still require careful manage-ment based on sound facts. Furthermore, there areremarkably few well documented reports of the longterm follow-up of intraocular lenses in general. So farall reports with a minimum follow-up period of five

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I. Cataractsurgery: interim results and complications ofa randomised controlled trial

years are of iris supported lenses,6 and only one hasno loss of patients to follow-up.7The authors believe that this is the first randomised

controlled trial to be reported, and, though themodes of treatment tested are no longer popular,the results of the study would still be useful andshould provide both valid data to help formulateopinions and background information to test futureclaims.The purpose of this paper is to report on:

(1) interim visual acuity, (2) complication rates,(3) corneal endothelial cell loss.

Patients and methods

The patients were recruited from a pool of casesrequring surgery, the need for which is based onvisual criteria. All eligible patients were given adetailed written account of the choices of treatment.They were interviewed and given explanations,usually in the presence of a relative, and signedinformed consent was obtained. Their age range wasfrom 55-90 (Table 1). Exclusion criteria aimed toeliminate patients with other ocular diseases likely to

Table I Age range ofpatients

No. ofpatients Age range in years

23 55-5933 60-6464 65-6998 70-7474 75-7940 80-841 1 85-89

Table 2 Exclusion criteria

General categories Specific categories

1. Corneal disease e.g., Fuchs's dystrophy, corneaguttata >10 dimples, scarringold herpes

2. Open-angle glaucoma3. Shallow anterior chamber <2 5 mm4. Iritis Presence or history of5. Juvenile onset diabetes Presence of proliferative

mellitus retinopathy in either eye or ofmoderate backgroundretinopathy in fellow eye

6. Axial myopia >6-0 DS7. Previous retinal disease e.g., Vein occlusion, retinal

detachment, degenerativedisease, known maculardegeneration

8. Mobility problems e.g., Parkinsonism, stroke, severeaffecting arthritishands

9. Keratoconjunctivitissicca10. Only eye

affect visual outcome and to ensure inclusion only ofthose patients with uncomplicated senile cataract.Patients had also to be suitable and willing to wear acontact lens (CL) (Table 2).To be eligible to contribute patients to the study

the surgeon must be familiar with both intra- andextracapsular techniques; must have carried out atleast 300 cataract operations, which must include aminimum of 25 lens implantations; and must abide bythe protocol.Those who took part were in fact much more

experienced. Surgeon I had been doing lens implantsurgery since 1973 and had used extracapsularsurgery for two years before the study began.

RAN DOMISATIONThree randomisation categories were used: group(A) intracapsular extraction and contact lens (CL);group (B) intracapsular extraction (IC) and 4-loopiris supported Federov lens; group (C) extracapsularextraction (EC) and 2-loop Binkhorst iridocapsularlens.Each contributing surgeon had his cases random-

ised separately, and it was permitted to randomise.the second eye in the study if the first eye of thatpatient had been assigned a contact lens.

SURGERYThe surgical method was standardised in a manualand approved by each participating surgeon. Minorvariations were allowed to suit individual needs.

All the surgery was performed with the use of aZeiss OpMic VI microscope. The 140-160° sectionwas two-planed and had a short limbal-based flap. 8/0virgin silk was used initially but after the first fewmonths 10/0 monofilament interrupted sutures wereused for all patients with the knot buried within thesclera. Two to three preplaced sutures were used,and closure was finished with three or four additionalsutures. a-Chymotrypsin was used routinely for ICwith implant (group B) but optional for patients over70 years old without an implant (group A). Forextracapsular extraction (group C) the standard 'canopener' technique was used for capsulotomy, andnuclear expression was followed by manual suction ofthe cortex by means of a coaxial or twin barrelledcannula which permitted simultaneous aspirationand infusion.Two iridectomies were routinely performed for the

implant groups after the second case of pupil blockglaucoma had occurred.

Lens implantation was carried out only when an airbubble could be maintained in the anterior chamber,and the procedure was abandoned if there wasvitreous loss. Preoperative medication included theuse of intravenous mannitol for all patients destined

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Oxford Cataract Treatment and Evaluation Team (OCTET)

for an implant who were less than 70 years old andhad no contraindications to its use. All but twopatients had general anaesthesia, which was of auniform technique' with halothane and assistedrespiration.The patients were seen daily for five days or until

their discharge, but scheduled postoperative assess-

ments were made at 48 hours, the fifth day, onemonth, six months, and thereafter at each anniver-sary of surgery. The clinical assessment was made byresearch registrar trained in ophthalmic observa-tions. The visual acuity was assessed independentlyby a trained optician (optometrist) who had no

professed bias towards either mode of treatment.Masking procedures were used in endothelial cellcounting, in reading fluorescein angiograms, andwhere possible in reading the end point of cornealthickness measurements. Masking was attempted inrefraction, but in practice it was difficult and notalways practicable to do this for large numbers ofpatients. However, the assessment ofcorrected visualacuity was carried out by a forced choice method as

defined in the manual and was used throughout thestudy. The method was similar to the one used in theDiabetic Retinopathy Study.9An experienced contact lens practitioner fitted all

contact lenses at six weeks to two months, and relatedcomplications were seen by a visiting consultant incontact lenses. A nurse practitioner, herself a CLwearer, helped patients manage their CL and had a

telephone which enabled patients to contact herdirectly. Uncomplicated cases with daily-wear hardlenses were seen as often as necessary until tolerancewas established. Thereafter, they were seen at thescheduled visits. Soft daily-wear and extended-wearlenses were checked as often as needed until a quietstage was reached, and thereafter at three-monthlyintervals for extended-wear cases.

COMPLICATIONSBased on the experience of a Pilot Study' 27 knownevents or complications were listed which requiredeither additional hospital visits or treatment. Ingeneral, postoperative complications were defined as

follows if they did not conform to those listed inTable 5: as an event (1) needing additional surgicalintervention, or (2) related to the surgery and reduc-ing the visual acuity by two lines of the Snellen chartto 6/12 (20/40), or (3) requiring prolonged additionalmedication.

Additional events were recorded on these criteria.All patients suffering a drop in acuity to 6/12 (20/40)or by two lines of Snellen with no obvious cause hadfluorescein angiography performed, which was readindependently. Cystoid macular oedema (CMO) was

recorded only if it was proved angiographically.

ENDOTHELIAL CELL COUNTSCorneal endothelial cells were photographed with aNikon non-contact specular microscope and countsderived by grid counting. The method has beendescribed"' and its precision estimated." Cell densi-ties were estimated before surgery, at one month, sixmonths, and yearly after operation. Masking pro-cedures were used for counting.

Results

Three hundred and twenty-seven patients and 333eyes were recruited from 15th January 1980 to 31June 1983. The number of patients asked initiallywas not known, but 400 patients were formallyapproached and 67 elected to have lens implants. Sixpatients allowed both eyes to be randomised for thetrial. The mean age of patients was 72 years with arange as shown in Table 1. The numbers in eachgroup are shown in Table 3.

DEATH AND LOSS TO FOLLOW-UPOne year from the beginning of the study twopatients each from groups A and B had died, but bythe three-year stage the number dead had increasedto 21 (A=6, B=7, C=8). However, apart from deaththere was no loss to follow-up.

RAN DOMISATIONThe numbers of patients treated by each surgeon inthe three treatment groups are shown in Table 3.There was one deviation from protocol regarding therandomisation. In one case surgeon III changed fromEC to IC extraction because the pupil would notdilate sufficiently to permit him to use his technique.

OPERATIVE COMPLICATIONSThe intraoperative complications are listed in Table4. Surgeon III contributed only 17 cases in the lastyear of the study, and all his cases were enteredwithin his first six months of joining.

Vitreous loss was the most serious complicationand occurred more frequently in EC than in ICsurgery. Capsule rupture occurred more frequentlyduring routine intracapsular surgery than when it wascombined with lens implantation. In no case whereruptured capsule had occurred was residual lens

Table 3 Numberofeyes and patients by treatment groups

Groups No. ofeyes No. ofpatients

A 111 109B 110 110C 112 112

Four patients have CL in one eye and an implant in the other. Somepatients in Group A are also in groups B and C.

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Table 4 Complications duringsurgery arranged bysurgeon

Surgeon I (n=274) Surgeon 11 Surgeon III(n=42) (n=17)

Complication n=56 n=218 n=42 n=17

Ist6 After6months monthsA B C A B C A B C A B C

Ruptured 2 4 2 1 1capsule

Vitreous loss 1 4 2 1 1 2 2Hyphaema 1 4 2 2 1 2Torn iris 1 1 3Others* 1 1 1

*Others=one local anaesthesia used (A); one torn descemet'smembrane (B); one misplaced inferior loop (B).n=number of eyes.Group A= IC, B=C+Federov I lens, C= EC+Binkhorstiriodcapsular lens.

Table 5 Failure ofimplantation

Surgeon Totalno. Group Vitreous Bulgy Torn Rupturedpatients loss vitreous iris vitreous

face face but novitreousloss

1 274 B 5 1 1C 5 1 - -

2 42 B 2 -

C 2 - - -

3 17 B - 1 - -C - - _ _

matter sufficient to interfere with vision. Approxi-mately 30% of cases of IC extraction (group A) hadno a-chymotrypsin, but only one of these patientssuffered a ruptured capsule.There were nine and six cases respectively in

groups B and C where implantation was abandoned,either because of vitreous loss or to avoid seriouscomplications (Table 5); but these cases remained intheir randomisation categories for the considerationof postoperative complications and visual results.

Table 6 Postoperative complications and events

Complications Groupsorevents

A B C

I Yr AGG I Yr AGG I Yr AGG

Raised pressureCMOCapsule opacitySuture removalUveitis (severe)Subluxed implantShallow anterior chamberHypopyonHyphaemaBlepharitisCorneal abrasionCorneal abscessMarginal keratitisBullous keratopathyConjunctival blebVitreous to sectionExcess remaining

lens matterExcess deposits on

implantDislocated implantVein occlusionRetinal detachmentSuture reactionPupil block glaucomaCorneal oedemaEpiscleritis prolongedImplant removal and

anterior vitrectomyChoroidal effusionIris in woundEndophthalmitisInfected corneal ulcerDisplaced pupilChoroiditisRepositioning of implantTear in Descemet'smembrane

Intracapsular implant/endothelial touch

Traumatic rupture ofsection and implantextrusion

Low-tension glaucomaVitreous opacitiesIris cyst

18 19 37 38 169 10 20 24(23) 14

412(10) 15(13) 112 3 12

8(*1 1 92 2 77 7 52 10 13 7(5) 03 6 12 6(4)

03 3 13 3

'5)

3

21 3 01 1 0

12

1 1 02 2 2(1)

2

13 171310(5)98(7)53

1

3

3

1

222202(1)2

7(6)3124(3)100

0

3 3

2222

I I

I I

0 1

1 1

POSTOPERATIVE COMPLICATIONSThe postoperative events or complications are listedin Table 6. Treatment groups are arranged accordingto initial randomisation, and all cases were includedin this assessment. Cases with raised pressure-26 mmHg are listed in Table 7. Significantly, moreeyes in group B had raised intraocular pressure thanin Group C (p<0-001). There were significantly moreeyes with raised pressure following the use of a-chymotrypsin, but its use was not associated withhigh pressures at 48 hours, the fifth day, or subse-quently. 'Hypopyon' included all cases with the

Group A= intracapsular extraction+CL, B= intracapsularextraction+Federov I lens, C=cxtracapsular extraction+ Binkhorstiridocapsular lens. AGG=aggregatc episodes for five years.Where an eye had more than one episode of a complication thenumber of eyes affected are shown in parentheses.

morphological appearance of a hypopyon withoutany distinction being made between an infection anda fibrin clot. All such cases were treated for infectionfor 24 hours and a clinical decision made as towhether an infection had occurred. In only two caseswhen the 'hypopyon' occurred in the immediate

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Table 7 Time course of'raisedpressure' complication*

Number ofeyesbygroup

A B C

0-48h 8 13 248h-1wk 2 2 01 wk-1 month 6 20 81 month-12 months 1 2 5Later than 12 months 2 1 1Cumulative total 19 38 16

*1OP >26mmHg or lower lOP deemed clinically to requiretreatment.

postoperative period, in groups B and C respectively,was there pain, and in no case was there an eventualdrop in visual acuity to less than 6/9 (20/30).

Subluxation of the implant occurred more fre-quently in the IC group, and all cases recorded ashaving this complication have suffered displacementof one loop. Five cases were rectified surgically, eightcases by positioning the patient and by the use ofdrops. One eye suffered four subluxations before theimplant was fixed by a McCannel suture. In only oneother instance had subluxation occurred twice in thesame eye.The depth of the anterior chamber was measured

at regular intervals and recorded as shallow if it wasless than 2*4 mm. In four cases such shallowingoccurred within 48 hours, and immediate surgicalintervention to reform the anterior chamber wasrequired. The others either had no lens inserted or nocorneal touch, and no surgery was needed in thesecases.

'Corneal oedema' indicates the presence ofoedemawithin the limbal wound. More than one case ofbullous keratopathy occurred in each of the implantcategories but not until two years after surgery.

Angiographically proved cystoid macular oedemaappeared twice as frequently in group B as in groupAand much more frequently than in group C, but thedifference is not statistically significant. Interest-ingly, of the 14 cases in group C with CMO, all buttwo had intact posterior capsules. For groups B andC, CMO was not related to subluxation, but therewas a significant association between CMO anduveitis (p<0.004).

Suture reaction was recorded if the patient soughtadvice at an unscheduled visit or if the suture neededto be removed either because of excessive reaction orbecause of astigmatism. The former virtually dis-appeared after 10-0 monofilament sutures were used,and 16 eyes, almost equally distributed between thegroups, had sutures removed because of astigmatismgreater than 4 dioptres.That there were more hyphaemata after one year

in group C is surprising, but one eye had twomicroscopic hyphaemata of no definite cause, prob-ably owing to sphincter erosion.

Corneal abrasion and abscess formation occurringin group C (EC with implant) were contact lensproblems in eyes which failed to receive an implantbecause of intraoperative complications.The complications which were unresolved at one

year are listed in Table 8.

ENDOTHELIAL CELL DENSITIESEndothelial cell counts of the operated eyes were notavailable for the first 16 patients who entered thestudy. Subsequently all had endothelial cell photo-graphs taken. The mean cell densities of the threetreatment groups were similar before surgery. Onemonth postoperatively cell loss was significantlygreater in the EC group, though the overall amountof cell loss was acceptable and the values were nottoo different from those published in the currentliterature.'5 Cell loss increased with time up to one

Table 8 Unresolved or unresolvable complications atoneyear

No. ofeyes by treatmentgroups

A B C

Unresolved Not Unresolved Not Unresolved Notresolvable resolvable resolvable

Glaucoma 1 11 5Shallow anterior chamber 1 1Uveitis 3Subluxed implant 2Corneal oedema 1Vein occlusion 1Capsule opacity 2Cystoid macular oedema 4 5 3Blepharitis 2 1 1Diplopia 1 1 1

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Table 9 Endothelial cell loss: percentage loss in each groupup to one year

Treatmentgroup I Month 6 Months I Year

A. Mean 10.7 12-1 15-1SD 16-4 13-5 14-0n= 74 83 78

B. Mean 10-9 14-1 20.1SD 12-4 13-1 16-9n= 75 83 78

C. Mean 16.3 18-7 23-3SD 16-3 15-5 11-8n= 74 88 86

Results ofvariance analysis:A v. B NS NS p<0-06Bv. C p<0-05 p<0-05 NSAv. C p<0 (5 p<0-01 p<0-001Overall integrity p<0.05 p<0-01 p<0-01

n=Number of eyes. NS=not significant.

year, and at each time point the amount of cell losstended to be greater for group C than for the othertwo groups. Variance analysis of the results of thethree groups showed a significant difference at eachof the three time points (Table 9). Only the patientsof surgeon I were included to -reduce potentialvariables in surgical techniques and because hecontributed more cases than the other two combined.The overall results suggest that both implant groupslost more cells than the non-implant group, and,

though the IC group with implant did slightly betterthan the EC group in the early stages, there was nosignificant difference between the two implantgroups at one year. These results were not altered bythe inclusion of cases from surgeons II and III.

VISUAL ACUITYThe visual acuities at one month (Fig. 1) and at oneyear (Fig. 2) are grouped according to levels of visionin Table 10. At the one-month stage the acuities forgroup A were obtained by spectacle correction, butthe one-year acuities were obtained by a combinationof contact lenses and additional spectacle correction.More eyes achieved 6/9 (20/30) acuity or better ingroup A than in the others at one month, but thistrend was reversed at one year (Table 10). Ninety-seven patients in group A were still wearing CL at theend of one year (44 daily wear and 53 extendedwear). Twenty-three patients had 6/18 (20/60) acuityor less at the one-year stage. The causes of poorvisual acuity and the postoperative complications arelisted in Table 11.

Discussion

The study design would have been improved if afourth arm of EC extraction without implant couldhave been introduced into the randomisation. Thiswas not considered ethical, as it was not a current

Number of eyes40-

30-

20 -

10-

0-6 /5

S...# S ...# l'.'' Slf# g...'l....# B..# E# S _6/6

m.::..*:-:-:*:-*:*:

z ...

E ..| '.'''.'2< *:<

< ..!s

i *:s .:s .,# s# s .....6/9

GroupACOB ESC O

I/C+C.L.I /C + Fed.E/C + I -C

6/12 6/18 6/24 6/36Fig. 1 Corrected distance visual acuity at one month postoperatively by treatmentgroups.

&M rM., fD6/60 CF <: HM

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Oxford Cataract Treatment and Evaluation Team (OCTET)

Number of eyes

GroupA aB 61C a

I/C +C.L.I /C + Fed.E/C + I-C

6/12 6/18 6/24 6/36 6/60u-

CF < HMFig. 2 Corrected distance visual acuity at oneyearpostoperatively by treatment groups.

mode of treatment at the time of inception of thestudy. A weakness of the study is that there is no

allowance for incorporating innovations which maybe considered improvements in treatment. Astrength is the standardized conditions, which were

maintained more or less constant throughout thestudy. Critics of the Federov I implant used inconjunction with IC extraction argued that theanterior loops can cause intermittent corneal touch,but a study using high-speed cinefilm did not confirmthis impression in cases without complications.'2Results of interim reviews monitored by an inde-

Table 10 Number ofeyes with different levels ofcorrectedVA (%)

Treatment No. of Snellen acuitygroup eyes

¢616(20120) ¢619(20130) 26112(20140)

1 MonthA 109 66(60) 93 (85) 103 (94)B 107 47 (44) 70(65) 88 (82)C 111 46(41) 84(75) 98(88)1 YearA 107 54(50) 93(87) 103(96)B 101 56(55) 79(78) 85(84)C 110 73(66) 99(90) 103(94)

; = Equal to or better.

pendent committee and conducted at six-monthlyintervals did not show differences between groupsthat were significantly great to warrant a change inthe structure of the study, and recruitment was

completed as planned.Surgeons II and III contributed comparatively few

cases, so that their intraoperative complicationsmay not be representative. Surgeon I's contributionsform the bulk of the study, so an analysis of hisintraoperative data is more meaningful. Among hispatients vitreous loss was the major complication andoccurred more frequently in EC extraction and the

Table 11 Eyes with VA <6112 and associated complication

Corrected VA

6/18 6/24 6/36 6/60 CF PL Complication Total eyes

B A B C Mac. deg. 4ACACB BA CMO 7C C Ret. detachment 2

A Glaucoma IB Uveitis 1

C ??Subluxed implant 1C Vein occlusion 1BAC A A Unknown 5

Total 22

Each letter indicating one case of that treatment group (group A=8,B=6, C=8).

40

30

20

10 -

0-i) 6/5

-

g...............

X ,.l'6/6 6/9

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I. Cataractsurgery: interim results and complications ofa randomised controlled trial

first six months of the study. Although he had beenusing EC extraction routinely for two years, it is stillpossible that in the first six months his surgicaltechniques and operating condition had not yet beenperfected. These factors may have accounted for thehigher rate of complications than later on. A reviewof the surgical notes showed that all cases of vitreousloss in group C occurred while cortical lens matterwas being removed and before the stage of lensimplantation had been reached.The most numerous postoperative complications

were raised pressure and cystoid macular oedema.An arbitrary level of pressure was selected, and anyeye with a pressure of 26 mmHg or greater wasconsidered to have raised pressure, which occurredmore frequently in group B than in groups A and C(p<0.001). In group B a-chymotrypsin was usedroutinely to facilitate delivery of the cataract becausethe pupil was often poorly dilated. Only Mydrilate(cyclopentolate 1%) was used to enlarge the pupil sothat the iris could remain responsive to intracameralMiochol (acetylcholine 1% and mannitol 3%) duringsurgery. A small pupil was thus obtained to maintainthe iris supported implants in the correct position.However, even allowing for the fact that only 70% ofeyes in group A had received a-chymotrypsin, theproportion of eyes developing raised pressure ingroup B was still higher than in group A. Signifi-cantly, more eyes developed raised pressure if a-chymotrypsin was used, but there was no correlationbetween the use of a-chymotrypsin and the level ofthe rise in pressure. In all cases the pressures werecontrolled or settled spontaneously by the six-monthstage.By doing fluorescein angiography only when there

is a reduction of vision, our method of assessmentwould detect only clinical CMO. This complicationoccurred in group B (IC+implant) more commonlythan in the other two groups, but the difference is notstatistically significant. In groups A, B, and C therewere only two, three, and one cases respectivelywhich remained unresolved by the one-year stage.Interestingly, all but two of the 14 cases with CMO ingroup C had intact capsules, which clearly are notalways an effective protection against this complica-tion.Nine eyes with implants were noted to have some

shallowing of the anterior chamber, and eight ofthem occurred in group B. In half of the eyes thecause was not known with certainty, but in half theshallowing was due to displacement (without sub-luxation) of the implant. Although the majorityresolved spontaneously, that this should occur sofrequently in group B is a worrying feature of thistype of implant.Some complications occurred more than once in

the same eye, and Table 6 distinguishes betweenepisodes recorded and the number of eyes affected.Fortunately the number of eyes developing the samecomplication more than once is limited.Some complications are not expected in the first

year, and thus no case of bullous keratopathy wasrecorded until after the two-year stage was reached.Likewise only four cases had capsule opacitiesaffecting visual acuity, but the aggregate total was19 by the time the study had been in progress for 4-5years.

If serious complications are considered, there wasno significant difference between groups except forraised pressure, because of small numbers; but, asregards the number of all the complications, group Bhad far more than group A or C.

If a grading system" was used to assign a numericalscore for each complication, more points beingawarded the more serious the event, group B scoredsignificantly higher than either group C or A. Thuseither by looking at the frequency of occurrence ofcomplications or by the use of a grading system groupB seemed to be doing less well than the other twogroups.From the point of view of visual acuity the

difference between groups is not significant or great,but the trend suggests that, at the one-year stage,group C is doing better than either group B orgroup A.Almost all the patients in group A had been fitted

with a contact lens by the one-year stage, and theproportion of eyes achieving 6/9 (20/30) acuity orbetter had diminished in comparison with the one-month stage, when the visual acuities were obtainedthrough spectacle correction (Table 10).

In our study of cell loss only central cornealdensities were estimated, as the number of patientsinvolved would make a study of morphology logistic-ally impossible. At one month cell loss would reflectintraoperative factors. Although cell loss was signifi-cantly greater with the EC group, it was only 16.3%,and, with the mean loss of 10-7 and 10*9% respect-ively in the other groups, the results are withincurrent claims, 14 '" which suggests that the surgery hasbeen competently carried out. It is, however, a littlesurprising that the loss in the IC group with a two-plane iris supported lens was significantly less than inthe EC group, which suggests that it is technicallypossible to execute the manoeuvres of implanting aniris-supported lens without undue trauma. That theimplant groups should lose significantly more cellssubsequently is worrying, but it is comforting to findthat by the one-year stage there is no significantdifference between the IC groups with implant andthe EC group.Many variables may affect cell loss, and a more

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Oxford Cataract Treatment and Evaluation Team (OCTET)

detailed discussion will be presented in a separatereport on cell loss after a longer follow-up, which isclearly necessary to determine whether increased losswith time is clinically important.

Cell loss apart, the evidence thus far, from thecomplication and visual acuity data, suggests thatlens implantation with extracapsular extraction com-pares favourably with intracapsular extraction andthe use of a contact lens. However, significantly morecomplications occurred in eyes with iris supportedlenses, amply confirming current opinion that suchlenses should be avoided for new cases of lensimplantation.

This work was supported by the National Eye Institute Grant No.EY02677-05.

References

I NIH Consensus Development Conference. J Am IntraoculImplant Soc 1980; 6: 21-4.

2 Worthen DM, Boucher JA, Buxton JN, et al. Interim FDAreport on intraocular lenses. Ophthalmology (Rochester) 1980;87: 267-71.

3 Cheng H, Law AB, McPherson K, Price NC. Longitudinal studyof intraocular lens implants after intracapsular cataract extrac-tion. Trans Ophthalmol Soc 1981; 101: 79-83.

4 Stark WJ, Worthen DM, Holladay JT, et al. The FDA report onintraocular lenses. Ophthalmology (Rochester) 1983; 90: 311-7.

5 McDonnell PJ, Green WR, Maumenee AE, et al. Pathologyof intraocular lenses in 33 eyes examined postmortem.Ophthalmology (Rochester) 1983; 90: 386-403.

6 Borrow JC, Drews RC. Long term results of lens implantation.In: Rosen E, Arnott E, Haining W, eds. Intraocular lensimplantation. Toronto: Mosby, 1984: 657.

7 Noble M, Cheng H. Jacobs PM, Salmon JD, McPherson K. Longterm follow-up of intraocular lens implants. Br J Ophthalmol1984; 68: 373-9.

8 Adams AP, Freedman AF, Henville JD. Normocapnic anaes-thesia for intraocular surgery. BrJ Ophthalmol 1979; 63: 204-10.

9 Diabetic retinopathy study research group. Design, methods andbaseline results. Invest Ophthalmol Vis Sci 1981; 21: 149-209.

10 Price NC, Cheng H. Contact and non-contact specular Vcro-scopy. Br J Ophthalmol 1981; 65: 568-74.

11 Cheng H, Jacobs PM, McPherson K, Noble MJ. Precision of celldensity estimates and endothelial cell loss with age. ArchOphthalmol 1985; 103: 1478-81.

12 Jacobs PM, Cheng H, Price NC. Pseudophakodonesis andcorneal endothelial contact: direct observations by high-speedcinematography. Br J Ophthalmol 1983; 67: 650-4.

13 Oxford Cataract Treatment and Evaluation Team. The use of agrading system in the evaluation of complications in a random-ised controlled trial on cataract surgery. Br J Ophthalmol (sameissue).

14 Bourne WM, Waller RR, Liesengang TJ, Brubaker RF. Cornealtrauma in intracapsular and extracapsular cataract extractionwith lens implantation. Arch Ophthalmol 1981; 99: 1375-6.

15 Liesengang TJ, Bourne WM, Ilstrup DM. Short- and long-termendothelial cell loss associated with cataract extraction andintraocular lens implantation. Am J Ophthalmol 1984; 97: 32-9.

Acceptedfor publication 15 October 1985.

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