Diabetes is one of the most common systemic conditions in patients presenting for cataract surgery at Northpark Private Hospital. It affects not only the likelihood of developing cataracts at an earlier age, but also the pre-operative assessment, the surgical planning, and the post-operative course. With careful preparation and appropriate monitoring, the vast majority of diabetic patients achieve excellent outcomes from cataract surgery. This post outlines what patients with diabetes should understand before proceeding, and what their treating team needs to consider.
Why do diabetic patients develop cataracts earlier?
Patients with diabetes develop cataracts at a younger age and with greater frequency than the general population. Chronically elevated blood glucose levels accelerate the accumulation of sorbitol within the crystalline lens through the polyol pathway, leading to osmotic changes that disrupt lens clarity. This process is accelerated in patients with poorly controlled diabetes and can result in clinically significant cataracts a decade or more earlier than would be expected in a non-diabetic patient of the same age.
A specific type of cataract associated with poorly controlled diabetes, sometimes called a snowflake or metabolic cataract, can develop rapidly in younger diabetic patients. These cataracts are characterised by white subcapsular opacities and can progress to a mature cataract over weeks to months in the setting of severe hyperglycaemia.
How does diabetes affect pre-operative assessment?
Before cataract surgery, diabetic patients require a more thorough assessment than patients without systemic disease. The key considerations are glycaemic control, retinal status, and the presence of diabetic macular oedema.
Glycaemic control is assessed by reviewing the patient's HbA1c. Surgery in the setting of poorly controlled diabetes carries higher risks including delayed wound healing, increased susceptibility to infection, and greater post-operative inflammation. Most surgeons prefer an HbA1c below 8 percent before proceeding with elective cataract surgery, though this threshold is not absolute and must be balanced against the visual need for surgery.
Retinal status must be assessed before cataract surgery in every diabetic patient. This is because cataract surgery can accelerate the progression of diabetic retinopathy in the post-operative period, and because pre-existing retinal disease will affect the visual outcome of surgery regardless of how well the cataract is removed. A fundus examination and, where indicated, optical coherence tomography (OCT) of the macula should be performed before surgery.
Diabetic macular oedema (DMO) requires specific attention. If significant DMO is present before cataract surgery, it should ideally be treated and stabilised with intravitreal anti-VEGF injections before the cataract procedure. Proceeding with cataract surgery in the setting of active DMO can worsen macular oedema post-operatively and significantly limit the visual outcome. In some cases, cataract surgery and intravitreal injection can be performed at the same sitting, but this requires careful planning and discussion between the surgeon and the patient.
Does cataract surgery worsen diabetic retinopathy?
This is one of the most common questions from diabetic patients and their referring practitioners. The answer is nuanced.
Cataract surgery can accelerate the progression of pre-existing diabetic retinopathy in the months following surgery, particularly in patients with moderate to severe non-proliferative diabetic retinopathy or proliferative diabetic retinopathy at the time of surgery. The mechanism is thought to involve surgical trauma, post-operative inflammation, and changes in vitreous oxygenation following lens removal.
In patients with mild or no diabetic retinopathy, cataract surgery is generally not associated with significant retinal progression. These patients still require post-operative retinal monitoring but the risk of significant progression is low.
In patients with more advanced retinopathy, the timing and sequencing of treatment requires discussion between the cataract surgeon and a medical retina specialist. In some cases, laser photocoagulation or intravitreal anti-VEGF treatment before cataract surgery is recommended to reduce the risk of post-operative progression.
What about lens selection for diabetic patients?
Lens selection in diabetic patients follows the same principles as in any cataract patient, with some important additional considerations.
Diffractive multifocal and trifocal lenses are generally not recommended for patients with significant diabetic macular disease. These lenses rely on good macular function to deliver their full range of vision, and any macular oedema or structural change will limit the visual outcome and may make the halos and reduced contrast associated with diffractive optics more bothersome.
For diabetic patients with healthy maculas and well-controlled disease, premium lens options including extended depth of focus lenses can be considered. The decision should be made on an individual basis after a thorough assessment of macular OCT and retinal status.
Standard monofocal lenses are appropriate for the majority of diabetic cataract patients and provide excellent visual outcomes when combined with good glycaemic control and appropriate retinal management.
Post-operative care and monitoring in diabetic patients
Diabetic patients require closer post-operative monitoring than patients without diabetes. The standard post-operative review schedule is modified to include retinal assessment at each visit, looking for signs of macular oedema progression or retinopathy worsening in the weeks following surgery. For a general overview of what to expect after cataract surgery, including when to seek urgent review, see our separate guide.
Patients with known diabetic retinopathy should be reviewed by a medical retina specialist in the months following cataract surgery, in addition to their routine surgical follow-up. Any new symptoms including distortion, blurring, or floaters after cataract surgery in a diabetic patient should prompt early review.
Glycaemic control in the post-operative period is important for wound healing and for minimising post-operative inflammation. Patients should continue their diabetic medications as directed by their GP or endocrinologist and should not make changes to their diabetic management without medical advice around the time of surgery.
When should diabetic patients be referred for cataract assessment?
GPs and optometrists managing diabetic patients should consider referring for cataract assessment when the cataract is causing significant visual impairment or functional limitation, when the cataract is limiting the ability to assess the retina adequately during diabetic eye screening, or when the patient is seeking assessment for premium lens options.
Early referral is particularly important in diabetic patients with active or progressive retinopathy, as coordinated management between the cataract surgeon and medical retina specialist may be needed before surgery can proceed. A referral that identifies the patient's diabetic history, current HbA1c, retinal status, and any history of intravitreal treatment will significantly assist the surgical planning process.
Referrals can be addressed to Northern Eye Consultants, Northpark Private Hospital, Bundoora. Our cataract surgeons at Northern Eye Consultants include subspecialty expertise in medical retina and manage diabetic eye disease including intravitreal injection therapy alongside cataract surgery planning. For information on costs and Medicare rebates for cataract surgery, see our guide to cataract surgery costs and Medicare.