Phaco does not worsen diabetic retinopathy

By Sean Henahan

SHEFFIELD - Contrary to previous reports, a new study concludes that phacoemulsification does not appear to accelerate the course of diabetic retinopathy following cataract surgery.

British investigators at the Royal Hallamshire Hospital in Sheffield, England conducted a prospective, case controlled study of postoperative diabetic retinopathy and maculopathy.

Mean preoperative visual acuity was 6/36, ranging from 6/12 to "hand movements". Following the surgery, 74% of patients gained at least two lines of vision, with 63% testing 6/12 or better. The patients whose postoperative acuity was 6/36 or worse had associated problems including ischaemic maculopathy, persistent macular oedema, AMD or ischaemic branch retinal vein occlusion.

The researchers assessed and graded diabetic retinopathy and diabetic maculopathy in both the operated and non-operated eyes before surgery and one day and one, three, six and 12 months thereafter.

These studies revealed progression of retinopathy in 11 patients out of 50. The retinopathy progressed in both operated and unoperated eyes in seven of these cases. In three other cases the retinopathy progressed only in the treated eye, while in one case progression was seen only in the unoperated eye.

The researchers also evaluated macular oedema before and after surgery. Thirteen eyes demonstrated postoperative macular oedema. Of these, four had transient pseudophakic cystoid macular oedema and nine had true diabetic maculopathy.

The maculopathy progressed in both eyes in five patients. In four patients maculopathy progressed only in the operated eye. Two unoperated eyes also showed signs of progression.

The research team says the results indicate no statistically significant difference in progression of either retinopathy or maculopathy in operated and unoperated eyes postoperatively. However, retinopathic progression was associated with a higher mean HbA1C and insulin treatment in both treated and untreated eyes, the researchers said.

"Uncomplicated phacoemulsification cataract surgery does not cause acceleration of diabetic retinopathy postoperatively and any progression that is observed probably represents the natural history of the disease.

"Although macular oedema is common after cataract surgery, it may follow a benign course and in many patients, the development of clinically significant macular oedema postoperatively probably represents natural disease progression rather than being a direct effect of surgery," the researchers reported.

A survey of the literature conducted by retinal surgeon Stephen Winder, study author David Squirrell and colleagues at the Royal Hallamshire Hospital shows reported progression rates ranging from 15% to 70% in diabetic patients undergoing cataract surgery.

Indeed, the current guidelines of the Royal College of Ophthalmologists warn that diabetic retinopathy may worsen after cataract surgery. But that opinion was based on retrospective reviews of ECCE procedures. Moreover, few prospective, controlled trials have looked at this question.

Further parsing of the data shows that the rate of retinopathy progression reported in the current study is close to that reported in other studies that did look at similar patients. Other studies also note that the rate of progression appears to be influenced by such factors as the adequacy of glycaemic control, the extent of preoperative retinopathy and the duration of diabetes, the researchers said.

"While our findings have to be interpreted with caution, we believe they may have important implications for the future care of diabetic patients with cataracts. Previously, because of the perceived threat of rapidly progressive postoperative diabetic retinopathy and maculopathy, authors recommended that cataract extraction should not be conducted on patients with diabetes until the vision deteriorated to at least 6/36.

"We believe this argument is no longer valid. Our data and that of others suggest that cataract surgery has minimal impact on the postoperative course of an eye's diabetic retinopathy," they concluded.

Postoperative treatment protocol
The surgeons performed panretinal photocoagulation in all cases where proliferative diabetic retinopathy was evident.

Patients did not undergo fluorescein angiography prior to cataract surgery. Patients in whom macular oedema with associated exudates on the first postoperative day evaluation were scheduled to receive laser photocoagulation treatment as soon as possible.

Fluorescein angiography was performed in all patients who developed new or recurrent macular oedema within three months of cataract surgery. They were then classified as having either cystoid macular oedema or diabetic maculopathy. Surgery was not considered for at least three months after diagnosis.

Rather, patients received topical and/or regional steroids. Laser photocoagulation was recommended if the macular oedema persisted at three months. Patients who developed macular oedema more than three months after cataract surgery were also scheduled for laser treatment.

Two of the eyes that developed macular disease had no preoperative diabetic maculopathy. In both cases, fluorescein angiography revealed a pattern of hyperfluorescence indicating 'Irvine Gass' pseudophakic cystoid maculopathy. Both of those eyes responded to medical treatment within three months.

Eleven eyes that developed signs of macular oedema had received treatment for macular oedema some time prior to cataract surgery and were considered stable at the time of the cataract procedure. Two of those eyes responded to medical therapy and the remaining nine were diagnosed as having progressive diabetic macular oedema.

The study appeared in study in the British Journal of Ophthalmology 2002; 86:565-571.

Top