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Editor,—We were interested to read Shuttleworth and colleagues’ recent paper on the benefit of cataract surgery on patients with age related macular degeneration (ARMD).1The article suggested that the prognosis of patients with ARMD after cataract extraction was not as poor as had been previously thought and that more than two thirds of patients benefit from surgery and consider the procedure worthwhile.
Previous research has suggested that cataract surgery may increase the progression of ARMD. Van de Schaft et al 2 reported an increased prevalence of disciform macular degeneration in postmortem pseudophakic eyes with IOL implants. The Beaver Dam Eye Study3 indicated a statistically significant relation between cataract surgery at baseline and the incidence and progression of disciform ARMD. Pollacket al 4 reported a 19% increase in progression following surgery on the first eye of patients with moderate, bilateral ARMD. In a further study5 they reported an even higher incidence of progression (24%) when the second eyes of patients with previous uneventful postoperative maculopathic course were operated on.
In 1997, we performed a pilot study to assess the feasibility of a major prospective study comparing the progression of ARMD on patients undergoing cataract surgery, with age matched controls. A quality of life questionnaire was administered before and after surgery to a group of patients (n=23) diagnosed with ARMD, and their case notes reviewed retrospectively for visual acuity, simple grading of ARMD, and status of fellow eye. Thirteen patients had mild dry ARMD, seven had moderate dry ARMD, two had severe dry, and one had severe wet ARMD at the time of surgery. Visual acuity (classified into four categories—less than 6/60; 6/60– 6/36; 6/24 to 6/18; and 6/12 to 6/6) improved in 18 patients, remained the same in three, and deteriorated in two patients. The poor visual outcome of the five patients whose eyesight did not improve was directly attributable to their ARMD and not to other ocular conditions. Both patients whose visual acuity declined had moderate, dry ARMD.
When quality of life measures were considered two areas showed significant change. Before surgery only 16% of patients reported that they were satisfied with their vision and 84% were dissatisfied. Following surgery 71% of patients were satisfied with their vision and only 29% were dissatisfied. Visual disability was assessed using the VF-14,6 a widely used questionnaire of patient functional impairment designed for use in cataract studies, and the mean score increased from 54% to 73%.
The rate of ARMD reported in these studies, although widely different, is still higher than would be expected by the natural course of the disease over the same period.7 Some of the variation in reported incidence and progression may be attributed to study design. Shuttleworth et al’s study was retrospective, with information gathered from case notes and a questionnaire, and included patients with all forms of ARMD. Pollacket al’s study was prospective and had strict inclusion criteria—only patients with moderate ARMD were selected. It is possible that the patients included in Pollacket al’s study were at a greater risk of progression, as all the patients had an intermediate form of the disease, which may still have been active. Surgery may provoke an inflammatory reaction or mechanical trauma that speeds up the degenerative process or triggers a more severe response.
These studies suggest that there is a specific group of patients who are at greatest risk of ARMD progression following cataract extraction, and it is this group of patients that we must try to identify for better assessment, follow up, and documentation of the disease.
At present, we are conducting a prospective case control study, funded by the Gift of Thomas Pocklington, that aims to determine the effects of cataract surgery on ARMD progression. We hope that it will yield valuable information enabling clinicians to assess the quality of life improvement and risk progression of ARMD in our increasing elderly population.
Editor,—We thank Ambrecht et al for their interest in our paper. They raise a number of interesting points.
We are aware of the evidence within the ophthalmic literature regarding the effect of cataract surgery upon the progression of ARMD. Although epidemiological evidence is suggestive of an association between cataract surgery and the development of exudative disease or geographic atrophy, this does not imply causation. We note that the Rotterdam study did not find such an association.
Postmortem studies have also provided some supportive data, however, van der Schaft et al make the point that the best assessment of the changes that occur after cataract extraction is to compare the operated eye with the fellow non-operated eye. In this study only 16 cases were suitable for such a comparison and no histological difference could be found between these eyes.
Although the two studies from Pollack et al find an increased incidence of progression of ARMD in eyes that have undergone cataract surgery, both draw data from small groups of patients and neither are RCTs. In addition, in their first paper assessments of fundus fluorescein angiograms by a blinded observer, necessary to confirm symmetrical disease, do not appear to have been performed and no statistically significant difference between operated and non-operated eyes was found. Pollack et al do not recommend withholding surgery in this group of patients although postoperative monitoring is advised.
We are encouraged that Ambrecht et alhave found cataract surgery to be of benefit in patients with ARMD using quality of life measures and the VF-14. However, large scale randomised control trials, with ARMD of all grades of severity, are required in order to identify those patients most likely to benefit from cataract surgery and also to identify those patients most at risk of disease progression.
We suggest that for the present time cataract surgery should not be denied to any patient on the grounds that their ARMD may progress. Indeed, on the basis of our study we conclude that the benefits considerably outweigh the risks.
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