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Cataract extraction is of undisputed efficacy in terms of improvements in both vision and quality of life. However, the benefits (and risks) of cataract surgery in patients with concomitant ocular diseases, such as age related macular degeneration (ARMD), are uncertain. With rapidly ageing populations and greater life expectancy, the number of patients with both cataract and ARMD will inevitably increase. How do we manage these patients? Is cataract surgery justified? Are there some who will benefit more than others? Conversely, does cataract surgery aggravate ARMD in other patients? Reliable data are lacking, but these issues are clearly important.
The paper by Armbrecht and colleagues in this issue of theBJO (p 1343) therefore represents an important and timely contribution to the literature. In this prospectively designed study of 187 patients, 90 with ARMD who underwent cataract surgery and two control groups (one with ARMD without cataract surgery and another without ARMD but with cataract surgery), the authors found significant improvements in both visual function and quality of life in patients with ARMD who had cataract surgery. Specifically, patients with mild and moderate ARMD benefited most from cataract surgery, especially if cataract was of moderate severity. Thus, this study provides data that suggest cataract surgery should be offered to selected patients with moderate cataract and mild/moderate ARMD, challenging the traditional view that most patients with ARMD are unlikely to benefit (and may even be harmed) from the procedure.
In a sense, the relation between cataract surgery and ARMD has been inconsistent. While some epidemiological studies have suggested an increased incidence and progression of ARMD among people who had cataract surgery, others have not found an association. In the Beaver Dam Eye study, Klein and colleagues found that eyes that had undergone cataract surgery were more likely to have a 5 year progression of age related maculopathy (OR 2.7; 95% CI, 1.7–4.4) and to develop signs of late age related maculopathy (OR 2.8; 95% CI, 1.0–7.6) than were eyes that were phakic, with the association significant despite controlling for other ARMD risk factors.1 However, in other large epidemiological studies, the Blue Mountains Eye Study and the Rotterdam Eye Study, no cross sectional association between cataract surgery and ARMD was observed.2 3
Fears that cataract surgery may be associated with higher risk of ARMD progression also arose from data based on clinical studies by Pollacket al,4-6 and from postmortem pathological studies by Van der Schaft et al.7 However, as pointed out by Armbrecht and colleagues, there are important limitations in these studies that suggest the results were inconclusive, and if anything, warrant further research.8 One such study by Shuttleworth and colleagues showed a clear benefit from cataract surgery in the majority of patients (more than two thirds) with ARMD.9 Nevertheless, the study was retrospective in nature (and subjected to recall and other bias) and the prevalence of ARMD in that study population was lower than expected (suggesting selective exclusion of patients with both ARMD and cataract). Armbrecht and colleagues' contribution in this issue of the BJO is important in two respects. Firstly, the prospective design, semistandardised grading of both cataract and ARMD, and objective assessment of visual function and quality of life represents additional improvements over Shuttleworthet al's study. Secondly, the study identified subgroups of patients who are more likely to benefit from cataract surgery; not unexpectedly, these were patients with mild or moderate ARMD and with moderate (and presumably more severe) cataract. However, caution is advised for several reasons. The study is limited by a short follow up period (5 months), inadequate power to detect progression of ARMD (particularly in the subgroup of patients with severe ARMD, n=8), possible inconsistencies in ARMD grading between the two study centres (direct ophthalmoscopy in Oxford, and photographic grading in Edinburgh), and selection bias inherent in any non-randomised design.
Where then do we go from here? There are several options. Firstly, an obvious “next step” is to consider a randomised clinical trial. This is not feasible as there will be ethical issues (for example, patients with mild cataract and moderate ARMD) and problems related to randomisation, masking, and objective assessment of benefits versus risks. If a clinical trial is not feasible, further prospective studies will provide much needed supporting evidence. These studies should preferably be multicentred and involve well defined prospective cohorts. They should be of sufficient power to detect significant difference in benefits and risks in different subgroups (combinations of mild/moderate/severe cataract and ARMD). These studies should have objective and standardised documentation of both cataract and ARMD severity, as well as preoperative and postoperative assessment of visual and quality of life outcomes. Some form of masking of the observers is critical. Finally, we have to adhere to the basic ethical principle of medicine: first do no harm, and remember that cataract surgery may, in some cases, subject patients to higher risk of blindness as a result of complications, such as progression of ARMD. Thus, certain high risk groups should be omitted from such a study.
Armbrecht et al's article has clearly started the ball rolling again on this very important problem. In the context of the data from this paper it appears that cataract surgery in patients with mild ARMD and moderate to severe cataract may be beneficial, but we should probably still be conservative in our management of patients with more severe ARMD and with mild cataracts. We await eagerly further studies to provide a consistent, reliable, and accurate answer to a question posed commonly by our patients with cataract and ARMD, “what are my chances of seeing better after a cataract operation?”