Cataract management in the diabetic eye

In this step we look at the additional clinical steps needed to effectively manage cataract in people with diabetes. This article is adapted from Rice, J. Cataract and diabetic retinopathy. Comm Eye Health Vol. 24 No. 75 2011 pp 09. Published online 31 October 2011.

Cataract is the opacification of the lens in the eye. It can be managed easily through cataract surgery, which is widely practiced. It is important to remember that cataract surgery may make diabetic retinopathy worse in people with diabetes. Even in well established cataract surgery facilities, managing people with diabetes requires additional planning and consideration.

Before cataract surgery

Before planning a cataract surgery for a patient with diabetes it is important to:

• Ensure blood sugars are controlled. There are no guidelines or recommended cut off levels but it is important the patient achieves the best control possible before surgery.

• Check that the patient’s level of vision matches the density of the cataract, as decreased vision may also be due to maculopathy

• Evaluate the iris carefully, to rule out neovascularisation on the iris. These are signs of ocular comorbidities such as neovascular glaucoma and proliferative retinopathy.

• If possible, use optical coherence tomography (OCT) to access the macula.

During cataract surgery

Eyes with mild to moderate non-proliferative diabetic retinopathy at the time of surgery are considered less at risk. Those with severe non-proliferative and proliferative diabetic retinopathy have a higher risk of progressive disease. Any clinically significant macular oedema (CSMO) which is present at the time of surgery is likely to progress and eyes with previously treated CSMO are also at increased risk of recurrence. The risk of progression is increased if the operation is complicated by excessive manipulation, vitreous loss, or severe post-operative inflammation.

Ideally, when the cataract does not preclude laser treatment, the diabetic retinopathy and maculopathy should be effectively controlled for at least three months before surgery.

Dense cataracts can sometimes prevent adequate examination or treatment of the retina in patients with diagnosed or suspected severe non-proliferative and proliferative diabetic retinopathy. In this case, its best to deliver pan-retinal photocoagulation either during the procedure or in the early post-operative period.

If the surgeon plans to give laser treatment with a contact lens in the early post-operative period, they should suture the cataract wound. If it is still hazardous to use a contact lens then effective slit lamp laser can still be applied through a non-contact 78D or 90D lens. Indirect laser for pan-retinal photocoagulation can also be used.

If the patient has diabetic maculopathy and/or more advanced retinopathy, the surgeon should consider intravitreal triamcinolone or anti-VEGF at the end of the procedure to reduce macular oedema. Triamcinolone targets the inflammation that exacerbates the oedema. Anti-VEGFs also reduce retinal swelling and may improve visual outcomes. Intravitreal steroids may cause raised intraocular pressure and anti-VEGF agents increase the risk of tractional complications in eyes with fibrovascular proliferation. The surgeon should still apply macular laser for CSMO post-operatively.

Cataract surgery, Solomon Islands © Anthony Hall, CC BY-NC-SA-4.0

During the post-operative period

In diabetes patients, it is very important to minimise post-operative inflammation. Surgeons should use post-operative topical non-steroidal anti-inflammatory drugs in addition to routine topical steroid preparations, particularly in those with pre-existing macular oedema.

In summary

Diabetes patients with mild to moderate diabetic retinopathy and no maculopathy have a good prognosis following cataract surgery. More advanced retinopathy or maculopathy should be controlled at least three months prior to surgery if possible.

Laser is the most recognised form of treatment but pharmacological agents play an important role in the management of these patients. It is also important to monitor high-risk patients in the post-operative period.

Visual outcomes following cataract surgery may vary between patients, with some improving to near normal levels whilst others may have poor vision post operatively. It’s therefore essential to provide pre-operative counselling to manage patients’ expectations.