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ECOS findings show that improved surgery can bring improved outcomes THE latest findings from the European Cataract Outcome Study (ECOS) indicate that while there has been little improvement overall in terms of patients' surgical outcomes and complication rates over the last five years, those centres adopting modern techniques more rapidly have had better results, according to a series of presentations at the XXI Congress of the ESCRS. The ECOS results include data from over 23,000 cataract procedures carried out at a total of 72 centres in 22 European countries from 1995 to 2002. During that time the number of countries and clinics participating annually has more than doubled while the number of procedures analysed has more than trebled, rising from 1403 cases in 1995 to 4983 in 2002, said Mats Lundstrom MD, the chairman of the study. "One of the main purposes of this study is to provide participating units and surgeons with a benchmark for good practice in cataract surgery and to allow surgeons to compare their results with others in an anonymous way. They then have a better idea of what they can achieve. The variations in results are the basis for quality improvement," he said. Echoing the findings of practice surveys conducted in Europe , the ECOS results show that most centres have adopted phaco and small incision techniques, Dr Lundstrom noted. As of 2002, the 42 centres participating that year used phaco for a mean of 93.3% of cataract procedures and 15 clinics used phaco exclusively. In addition, foldable IOLs accounted for a mean of 77.5% of IOLs implanted at the various centres. Their frequency of use ranged from 10% to 100% of cases and 26 of the 42 centres used the lenses in over 90% of cases. Throughout the study years nearly all patients have received posterior chamber IOLs, while small proportions have received anterior chamber lenses or were left aphakic. Most of the centres performed the majority of their surgeries on an outpatient basis. The mean frequency of inpatient surgery was 29.2%, and only 10 centres performed inpatient surgery in more than 50% of cases. Patients' mean preoperative visual acuity in their better eye, was 0.5 or better in a mean of 64% of cases, and 0.8 or better in a mean of 31.7%.Postoperative visual acuity in the treated eye was =0.5 in a mean of 85% of cases.The difference between target refraction and postoperative refraction was less than one dioptre in a mean of 75.6% of cases. The mean induced astigmatism was 0.62 D using the subtraction method of measurement and 0.72 D using the Naeser method. Dr Lundstrom noted that on the surface the ECOS findings seem to suggest that, contrary to expectations, the widespread adoption of newer technologies such as phacoemulsification and foldable IOLs has apparently not resulted in a concomitant improvement in refractive and visual outcomes. For example, throughout the years 1995-2002 the mean difference between target and achieved refraction has wavered between 0.7 D and 0.8 D and the proportion within one dioptre has remained fairly consistent at about 75%. Similarly, the proportion with postoperative visual acuity worse than 20/40 has remained fairly steady at around 15%. The same has held true for surgically induced astigmatism which has ranged between 0.59 D and 0.66 D (subtraction method). However, Dr Lundstrom said a closer look at the individual clinics who had been participating in ECOS since the beginning suggested that where there had been changes to more modern cataract extraction techniques there had also been improvements in outcome. "If you look at the interested and keen surgeons who have participated every year you will find remarkable changes in behaviour and also some improvements in outcome."Complication rates unchangedOn the other hand complication rates have remained unaltered even in those centres adopting newer cataract surgery techniques, Dr Lundstrom said. In 1995 the proportion of procedures with "any complications" was 3.51%; in 2002 it was 3.94%. The incidence of specific complications has remained similarly steady. For example, the rate of posterior capsule rupture has ranged between 2.16% and 2.43% and the rate of vitreous loss has ranged between 1.06% and 1.58%. "Surprisingly, those centres that have modified their surgery have experienced no reductions in their surgical complication rates. However, the ECOS study has been useful in showing which types of pre-existing morbidities will give rise to each type of complication. This provides better information for the surgeon and the patient when surgery is discussed," he added. Dr Lundstrom noted that the ECOS questionnaire has recently been expanded to include questions regarding whether patients had undergone previous refractive surgery. Helen Seward FRCS, FRCOphth, the honorary secretary of ECOS said that it is thanks to the sharp but limited focus of the ECOS questionnaire that its findings are so relevant to cataract surgeons. "It is important to limit the amount of data collection to that which is most useful. Important outcome measures can be measured with relatively simple data collection." As an example of how telling just one simple outcome measure can be, Dr Seward highlighted one of the key findings of ECOS to date, namely the percentage with worse vision than they started with. Between 1997 and 2005, the percentage of such outcomes has shown no improvement, varying from 2.5% to 3.0% and averaging at 2.76%. Clues to causes for poor outcome. Ana lysis of the ECOS data showed that a poor outcome correlated significantly with the incidence of complications, which in turn correlated with poor pre-operative visual acuity, dense cataracts and pre-operative co-morbidity. "This raises the question of what can we do to reduce the complications in this group. Machinery and surgical techniques have improved and yet the complication rates remain the same. We need to know why." Similarly, the percentages who are more than one dioptre outside target refraction have remained fairly consistent at around 20%. "The kind of questions the ECOS findings raise include whether cataract surgery has not improved from 1997 to 2003, whether transition to phaco in some centres is skewing the figures, and also whether cataract surgery is as good as it is going to get. It also allows us to arrive at an evidence-based ‘acceptable complication rate' while perhaps offering clues as to how we might bring the complication rate down." Astigmatism reduced in some centres Liv Drolsum MD maintained that a survey of eight clinics which participated in ECOS from 1997 to 2001 indicate that an increase in small incision surgery has resulted in less induced astigmatism. Postoperative astigmatism at the eight centres fell from 0.42 D to 0.18 D during the years 1997-2001, Dr Drolsum said, adding: "The units which accounted for most of the reduction were those which had the highest increase from standard extracapsular technique to phaco. Furthermore the use of foldable IOLs also increased during these years. As we know, small-incision surgery with implantation of foldable IOLs results in lower induced astigmatism." The eight centres in the study were from the UK , Sweden , Norway , Denmark , Germany and Portugal . In 1997, a little more than 700 (728) eyes were included. By 2001, the number increased to 1316 and a total of 5113 eyes were included in the analysis, Dr Drolsum said. During those years there was a statistically significant increase in the frequency of phaco procedures, from 87% to 96%. However, while in some units the frequency increased from 34% phaco to 91% phaco in 2001, other units had a very high frequency of phaco in 1997 as well. Almost all of the clinics had a similar increase in the use of foldable lenses, from around one-third of lenses implanted in 1997 to 90% in 2001. Patients in the study also appeared to be undergoing cataract surgery at an increasingly earlier stage of their disease when their visual disability was not as far advanced. In 1997 the mean preoperative BCVA was 0.26, while in 2001 it was 0.34. The difference is statistically significant. The frequency of second eye surgery, increased from 35% to 40% during the years of the study. On the other hand, the mean difference between target and final refraction was not significantly changed between 1997 and 2001, remaining at around 0.6 D. "This may reflect a lack of change over the years in the equipment used for measuring the axial length and IOL power calculation formulas have not changed over the years. However, there is no information on how target refraction was measured in the different units," Dr Drolsum said, summing up: "There has been a favourable development over the years, more small incision surgery resulting in less astigmatism, and maybe this improvement in clinical outcome is one of the reasons for a more liberal indication for surgery. Hopefully, participation in the ECOS has had a positive influence on the outcome of cataract surgery." Mats Lundstrom MD, Helen Seward FRCS, FRCOphth. Liv Drolsum MD
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