Cataract Surgery in Patients with Diabetes: Preoperative Planning, Risks, and What to Expect

Diabetes is one of the most important systemic conditions affecting cataract surgery outcomes. Patients with diabetes develop cataracts earlier than the general population and face a two to five times higher risk of cataract formation. According to a study published in Primary Care Diabetes in 2023, up to 20 percent of all cataract surgeries are performed on patients with diabetes. The diabetic eye has several specific vulnerabilities that affect surgical planning, expected outcomes, and postoperative risks that differ from those in patients without diabetes. This post is written for both patients and referring optometrists and GPs, and covers the complete management of cataract surgery in Melbourne in the diabetic patient from preoperative assessment through postoperative care.

How diabetes affects the eye and cataract surgery risk

Diabetes affects multiple structures of the eye in ways that are directly relevant to cataract surgery planning. Compared with patients without diabetes, diabetic patients face a higher risk of poor pupil dilation, reduced corneal endothelial reserve, impaired wound healing, and elevated risk of postoperative macular oedema. Understanding these vulnerabilities allows the surgical team to plan appropriately and reduce the risk of complications.

The corneal endothelium is more vulnerable in diabetic patients. Endothelial cell density is typically reduced and endothelial pump function is impaired, making diabetic eyes more susceptible to postoperative corneal oedema. Phacoemulsification energy delivery during surgery causes endothelial cell loss in all eyes but the effect may be more clinically significant in diabetic eyes with already-compromised endothelial reserve.

The pupil frequently dilates poorly in diabetic patients. Diabetic autonomic neuropathy affects the pupillary dilator muscle, resulting in a small rigid pupil that does not dilate adequately with standard mydriatic drops. Inadequate dilation limits surgical access and increases the risk of anterior and posterior capsular complications. Pupil expansion devices including iris hooks and Malyugin rings, and intracameral pharmacological agents, are used routinely when dilation is insufficient.

Wound healing is impaired in diabetic patients. Elevated blood glucose impairs leukocyte function and the cellular response to infection and tissue repair. This increases the risk of postoperative wound-related complications, surgical site infections, and delayed epithelial healing. Optimising glycaemic control before surgery is the primary modifiable factor in reducing this risk.

The risk of postoperative macular oedema is significantly elevated in diabetic patients with pre-existing diabetic retinopathy, as discussed in detail below.

Preoperative assessment in diabetic patients

The preoperative assessment for cataract surgery in diabetic patients requires specific additional steps beyond the standard cataract workup. HbA1c measurement, macular OCT, dilated fundus examination to stage diabetic retinopathy, and ocular surface assessment are all mandatory before scheduling surgery. Each finding directly affects the surgical plan, IOL selection, and the expected postoperative outcome.

HbA1c measurement is essential. The 2024 Standards of Care in Diabetes from the American Diabetes Association recommend an HbA1c target of less than 8 percent for elective surgery. An HbA1c above this level signals suboptimal chronic glycaemic control and should prompt optimisation with the patient's endocrinologist or GP before scheduling surgery. Higher HbA1c is associated with increased infection risk, impaired wound healing, and greater postoperative macular oedema risk.

Macular OCT is mandatory before cataract surgery in all diabetic patients. It identifies the presence and severity of diabetic macular oedema (DMO), which is the most important factor limiting postoperative visual outcome. If centre-involving DMO is present, it should be treated before or at the time of cataract surgery. Proceeding with cataract surgery in the presence of untreated significant DMO will produce a poor visual outcome regardless of how well the cataract is removed.

Dilated fundus examination assesses the severity of diabetic retinopathy. Proliferative diabetic retinopathy (PDR) with active neovascularisation should be treated with laser photocoagulation and/or intravitreal anti-VEGF before cataract surgery wherever possible. Surgery in the presence of active PDR carries a substantially elevated risk of iris neovascularisation, vitreous haemorrhage, and tractional retinal detachment.

Corneal topography and biometry should include assessment of the tear film and corneal surface. Diabetic patients frequently have tear film dysfunction which, as in patients using long-term preserved glaucoma drops (discussed in our guide to cataract surgery with glaucoma), can affect the accuracy of keratometry measurements and IOL power calculation.

Renal function should be noted. Patients with diabetic nephropathy may be on medications that affect perioperative management including SGLT2 inhibitors, which require cessation before surgery as discussed below.

Glycaemic management on the day of surgery: what to take and what to omit

Managing diabetic medications on the day of cataract surgery requires a specific plan confirmed between the surgeon, anaesthetist, and the patient's treating physician before the day of surgery. The target blood glucose range is 5.6 to 10.0 mmol/L in the four hours before the procedure. Patients should be scheduled first on the operating list wherever possible. Each class of diabetes medication requires individual consideration as set out below.

The following guidance is based on the 2024 American Diabetes Association Standards of Care, the Society for Ambulatory Anesthesia (SAMBA) 2023 updated consensus statement on perioperative blood glucose management, and the 2022 Centre for Perioperative Care (CPOC) guidelines.

Blood glucose below 5.6 mmol/L (hypoglycaemia) is dangerous in a fasting patient and must be corrected before proceeding. Blood glucose above 10 mmol/L does not automatically require postponement of routine cataract surgery but should be documented and managed in the perioperative period.

Fasting requirements for cataract surgery under topical anaesthesia with sedation vary by institution and anaesthetist preference. Most centres require a minimum fast of two hours for clear fluids and six hours for food. Patients with diabetes should be scheduled first on the operating list wherever possible to minimise the fasting period and the period of glycaemic instability.

Oral hypoglycaemic medications:

Metformin should be omitted on the day of surgery. The primary reason is the theoretical risk of lactic acidosis with contrast media in patients with renal impairment, though this risk is very low in elective cataract surgery without contrast. Omitting metformin on the day of surgery is the standard recommendation and does not require a prolonged washout period. Metformin can be resumed the following day once normal oral intake has been established.

SGLT2 inhibitors (empagliflozin, dapagliflozin, canagliflozin) should be omitted three to four days before surgery. SGLT2 inhibitors are associated with a risk of euglycaemic diabetic ketoacidosis in the perioperative fasting period, a serious complication in which ketoacidosis develops without the typical marker of elevated blood glucose, making it clinically difficult to detect. Patients on these medications must be clearly identified at the preoperative assessment and the cessation plan communicated to their GP.

Sulphonylureas (glipizide, gliclazide, glibenclamide) should be omitted on the morning of surgery. Sulphonylureas stimulate insulin secretion independently of blood glucose and carry a significant hypoglycaemia risk in a fasting patient. They should not be taken on the morning of surgery and can be resumed with the first meal after surgery.

GLP-1 receptor agonists (semaglutide, dulaglutide, liraglutide) have recently attracted attention in the perioperative setting because of their gastric motility effects. Current guidance from the American Society of Anesthesiologists (2023) recommends considering omission of weekly GLP-1 agonists for one week before elective surgery due to their gastric emptying delay and associated aspiration risk under anaesthesia. Daily GLP-1 agonists should be omitted on the day of surgery. This recommendation applies even for topical anaesthesia cataract surgery with sedation given the sedation component. Patients on semaglutide (Ozempic or Wegovy) should specifically raise this with their anaesthetist at the pre-operative assessment.

DPP-4 inhibitors (sitagliptin, saxagliptin) are generally continued on the morning of surgery as they carry a low hypoglycaemia risk when used alone.

Insulin management:

Long-acting basal insulin (glargine, detemir, degludec): the evening before surgery, the dose should be reduced by 20 to 25 percent to reduce hypoglycaemia risk during the fasting period. The morning dose of long-acting insulin, if applicable, should similarly be reduced by 20 to 25 percent or omitted in consultation with the patient's treating physician or endocrinologist.

Intermediate-acting insulin (NPH): the dose given the evening before surgery should be reduced by 25 percent. The morning NPH dose should be omitted on the day of surgery.

Short-acting and rapid-acting insulin (NovoRapid, Humalog, Apidra): mealtime insulin doses should be omitted when meals are omitted. Correction doses for hyperglycaemia may be given in the perioperative period under the guidance of the anaesthetist.

Insulin pumps (CSII): patients on continuous subcutaneous insulin infusion pumps should continue their basal rate but bolus doses should be omitted during fasting. The pump management plan should be confirmed with the patient's endocrinologist before surgery.

Blood glucose should be checked on arrival at the day surgery facility and immediately before the procedure. Patients should bring their glucose monitoring equipment and any insulin they may need.

These instructions must be individualised for each patient. The general guidance above is based on published consensus guidelines but does not replace the patient's own physician's specific instructions. Any uncertainty should be resolved with the treating endocrinologist or GP before the day of surgery.

Visual outcomes by stage of diabetic retinopathy

The expected visual outcome after cataract surgery in diabetic patients depends directly on the stage of diabetic retinopathy present before surgery. Patients without retinopathy achieve outcomes comparable to non-diabetic controls. Those with advanced proliferative retinopathy and macular involvement have the most limited outcomes. Knowing the retinopathy stage before surgery is essential for setting accurate expectations at the preoperative consultation.

No diabetic retinopathy: patients with diabetes but no retinal changes can expect visual outcomes comparable to patients without diabetes. A systematic review published in 2025 found that patients with type 2 diabetes without pre-existing retinopathy or macular disease achieved postoperative visual acuity outcomes similar to non-diabetic controls.

Non-proliferative diabetic retinopathy (NPDR) without maculopathy: a retrospective study of 150 eyes showed mean postoperative best-corrected visual acuity of 6/9 (20/30) in this group, representing good functional vision. Visual outcomes are generally satisfactory provided the macula is not involved.

NPDR with maculopathy: postoperative mean BCVA was 6/12 (20/40) in the same study, with outcomes limited by the macular disease. Pre-operative treatment of DMO is the most important modifiable factor for improving this outcome.

PDR without maculopathy: postoperative mean BCVA was 6/12 (20/40). The retinopathy itself limits outcomes and postoperative monitoring for progression is essential.

PDR with maculopathy: postoperative mean BCVA was 6/24 (20/80), reflecting the combined effect of macular disease and advanced retinopathy.

Advanced diabetic eye disease: the poorest outcomes were observed in this group with mean postoperative BCVA of 6/48 (20/160). Careful pre-operative counselling about realistic expectations is essential.

Diabetic macular oedema: pre and postoperative management

Diabetic macular oedema (DMO) is the most important complication affecting visual outcomes after cataract surgery in diabetic patients. It requires specific assessment and management both before and after surgery. Centre-involving DMO present before surgery must be treated before proceeding. Cataract surgery itself can trigger or worsen DMO, with the risk peaking at three to six months postoperatively and highest in patients with pre-existing moderate to severe NPDR.

Pre-existing DMO before cataract surgery: centre-involving DMO present before surgery significantly limits the expected visual outcome. The current evidence and clinical consensus support treating DMO before or at the time of cataract surgery rather than proceeding and hoping the DMO will resolve spontaneously. Options include:

Intravitreal anti-VEGF injection (bevacizumab, ranibizumab, aflibercept) given four to six weeks before cataract surgery to reduce macular thickness. A 2023 study published in Graefes Archive of Clinical and Experimental Ophthalmology comparing pre-operative versus post-operative intravitreal aflibercept for DME in cataract surgery patients found that pre-operative injection produced better visual outcomes than post-operative injection alone (Khattab et al., Graefes Arch Clin Exp Ophthalmol. 2023;261(11):3223-3229).

Intravitreal injection at the time of cataract surgery, combined with phacoemulsification. A 2024 review in International Ophthalmology summarised evidence supporting combined cataract surgery with intravitreal injection as an effective approach for managing DMO in the cataract surgery setting.

Topical NSAIDs given before surgery for four to six weeks can reduce the inflammatory contribution to postoperative macular oedema.

Post-operative DMO: cataract surgery itself can trigger or worsen DMO due to the inflammatory response to surgery. A landmark multicentre UK study published in PubMed (UK DR EMR Users Group Report 2) analysed 4,850 eyes and found that the rate of developing treatment-requiring DMO increased sharply in the year after cataract surgery, peaking in the three to six month postoperative period. Risk was strongly associated with preoperative retinopathy grade: the risk of post-operative DMO in the first year was 1.0 percent in eyes with no pre-operative DR, 5.4 percent with mild NPDR, 10.0 percent with moderate NPDR, 13.1 percent with severe NPDR, and 4.9 percent with PDR. Patients with moderate and severe NPDR are at particularly high risk and should be counselled accordingly and monitored closely after surgery (PubMed 28487377).

The primary mechanism is prostaglandin-mediated disruption of the blood-retinal barrier following the inflammatory stimulus of surgery. Postoperative topical steroid and NSAID drops help reduce this inflammatory stimulus. Eyes with pre-existing DMO or severe NPDR should be followed with macular OCT at four to six weeks and three months after surgery. New or worsening DMO requires prompt intravitreal treatment.

Proliferative diabetic retinopathy: pre and postoperative considerations

Proliferative diabetic retinopathy (PDR) represents the most advanced stage of diabetic retinopathy and carries the highest surgical risk in the cataract setting. Active PDR with neovascularisation should be treated before cataract surgery wherever possible. The risks of proceeding with inadequately treated PDR include iris neovascularisation, neovascular glaucoma, vitreous haemorrhage, and tractional retinal detachment.

Active PDR with neovascularisation of the disc or retina should ideally be treated before cataract surgery. Published guidelines recommend panretinal laser photocoagulation for preproliferative and early PDR before cataract surgery because of the elevated risk of postoperative iris neovascularisation and retinopathy progression. Intravitreal anti-VEGF therapy has largely replaced or supplemented laser in the management of active PDR before surgery. The cataract itself may limit adequate retinal visualisation for laser treatment, in which case cataract surgery may need to proceed first with close postoperative monitoring.

Iris neovascularisation (rubeosis iridis) is a serious complication that can develop after cataract surgery in eyes with inadequately treated PDR. New blood vessel formation on the iris surface can progress to neovascular glaucoma, an aggressive and difficult-to-treat form of elevated intraocular pressure. Pre-operative treatment of PDR and intravitreal anti-VEGF before surgery reduce this risk.

Vitreous haemorrhage can occur postoperatively in eyes with PDR due to bleeding from neovascular tissue. If this occurs it may clear spontaneously over weeks or require vitrectomy.

Tractional retinal detachment is the most severe complication of advanced PDR and requires vitreoretinal surgical management. Cataract surgery in eyes with traction should only be performed in consultation with a vitreoretinal surgeon.

IOL options in diabetic patients

The choice of intraocular lens in diabetic patients follows similar principles to cataract surgery with macular degeneration and cataract surgery with glaucoma, with important diabetes-specific considerations around retinopathy progression and future macular risk. Monofocal lenses are the standard recommendation for patients with existing diabetic retinopathy. Diffractive premium lenses are generally avoided because the risk of future macular disease means a lens that performs well today may perform poorly as the retinal disease advances.

Diffractive trifocal and multifocal lenses are generally not recommended in diabetic patients with significant diabetic retinopathy. Macular disease from diabetic retinopathy causes contrast sensitivity loss, and diffractive IOLs further reduce contrast by splitting light. The combination produces poor functional vision. Even in diabetic patients without current maculopathy, the risk of future diabetic macular oedema and retinopathy progression means that a premium diffractive lens chosen today may perform poorly as the retinal disease progresses.

Monofocal lenses are the standard recommendation for patients with diabetic retinopathy. They maximise optical efficiency and contrast, which is most important in an eye at risk of macular compromise. For a complete guide to IOL types and patient selection criteria, see our premium IOL guide Australia.

Non-diffractive EDOF lenses may be considered in selected patients with well-controlled diabetes and no retinopathy or very early stable retinopathy, where the risk of future macular disease is low. This requires careful individual assessment.

Toric lenses for astigmatism correction are appropriate in diabetic patients and do not carry the contrast concerns of diffractive designs.

Hydrophobic acrylic lens materials are generally preferred in diabetic patients because of the lower risk of posterior capsule opacification compared with hydrophilic materials in the context of chronic intraocular inflammation from diabetic eye disease.

Patients who also have coexisting dry AMD or geographic atrophy face additional macular considerations relevant to IOL selection. Information on new treatments for geographic atrophy and dry AMD is available in our dedicated guide for patients managing both conditions.

Postoperative complications specific to diabetic patients

Diabetic patients face a higher rate of several postoperative complications beyond macular oedema and retinopathy progression. Infection risk is elevated due to impaired immune function. Corneal oedema may be more prolonged due to reduced endothelial reserve. Posterior capsule opacification may develop more rapidly. Wound healing is slower. Each of these complications requires awareness at the postoperative review and prompt management when identified.

Infection: the risk of postoperative endophthalmitis is higher in diabetic patients due to impaired immune function. Adherence to postoperative antibiotic drop regimens is particularly important. Symptoms of infection including increasing pain, redness, and blurred vision in the first one to two weeks require urgent same-day assessment.

Corneal oedema: diabetic corneas with reduced endothelial cell density may take longer to recover clarity after surgery. Prolonged postoperative corneal oedema is more common and may require extended use of hypertonic saline drops or, rarely, corneal transplantation in severe cases.

Posterior capsule opacification (PCO): PCO may develop more rapidly in diabetic patients and may require YAG laser capsulotomy. The YAG procedure is safe in diabetic eyes but the decision to proceed should be made carefully in eyes with active macular disease as the YAG inflammatory stimulus can worsen DMO.

Wound healing: delayed wound healing and increased risk of suture-related complications are more common in poorly controlled diabetes. Any wound-related symptoms require prompt review.

Postoperative monitoring schedule for diabetic patients

Diabetic patients require a more frequent and prolonged postoperative monitoring schedule than non-diabetic cataract patients. The elevated risks of DMO development and retinopathy progression in the months after surgery mean that macular OCT at six weeks and three months is mandatory for all diabetic patients, not just those with pre-existing retinopathy. This monitoring schedule differs from the standard cataract follow-up and should be communicated clearly to the patient before surgery.

The minimum recommended postoperative monitoring schedule for diabetic cataract patients is:

Day one review: wound assessment, IOP check, early complication screening.

Six weeks: macular OCT to assess for DMO. This is the earliest time point at which post-operative DMO can be reliably detected and treated. Fundus examination to assess retinopathy status.

Three months: repeat macular OCT and fundus examination. This is the peak risk period for post-operative DMO development.

Six months: final refraction. Assessment of retinopathy stability. Referral to medical retina if new or worsening macular oedema or retinopathy progression is identified.

What optometrists and GPs need to know: referral guidance

For referring optometrists and GPs, the most useful referrals for diabetic cataract patients include the current HbA1c, diabetes medications, retinopathy stage, and any recent OCT reports. This information directly affects the surgical plan and the timing of surgery. Patients with active PDR or centre-involving DMO should be referred for retinal assessment concurrently with or before cataract referral. Information on referral information for optometrists and GPs is available on this site.

For patients with diabetes presenting with cataract, the following information is most useful to include in the referral:

Current HbA1c and date of measurement. If HbA1c is above 8 percent, a note that glycaemic optimisation is being pursued is helpful.

Current diabetes medications, specifically noting any SGLT2 inhibitors or GLP-1 receptor agonists which require specific perioperative management.

Stage of diabetic retinopathy and any history of DMO or PDR treatment.

Most recent macular OCT report if available.

Any history of renal impairment relevant to SGLT2 inhibitor cessation timing.

Patients with active PDR or centre-involving DMO should ideally be referred to a retinal specialist concurrently or before cataract surgery referral, or the cataract referral should flag that retinal assessment is still pending. Coordinating cataract and retinal management avoids surgical delays and optimises the sequence of treatment.

For information on the financial aspects of cataract surgery, including cataract surgery costs and Medicare rebates in Australia, see our dedicated cost guide. For patients with coexisting conditions affecting the macula, including cataract surgery with macular degeneration, additional guides on this site may assist with preoperative counselling and referral planning.

For cataract surgery in diabetic patients at Northern Eye Consultants, further referral and patient information is available on the Northern Eye Consultants website.

Arranging an assessment

If you have diabetes and have been told you need cataract surgery, or if an optometrist has detected a visually significant cataract at your annual diabetic eye review, a preoperative assessment with an experienced cataract surgeon is the next step.

I consult at Northern Eye Consultants, Northpark Private Hospital, Bundoora, and at Bass Coast Eye Centre, Wonthaggi. A referral from your GP or optometrist is required. Referrals can be addressed to Dr Ross MacIntyre at either location.

Contact Northern Eye Consultants to arrange an appointment. For referral information for GPs and optometrists, visit the Northern Eye Consultants for-referrers page. Further information on cataract surgery Melbourne including a published five-year surgical outcomes audit is available at drmacintyre.com.

References

1. Postoperative Visual Acuity Outcomes After Phacoemulsification in Patients With Type 2 Diabetes Mellitus: A Systematic Review. PMC12826558. https://pmc.ncbi.nlm.nih.gov/articles/PMC12826558/
2. Outcomes of Cataract Surgery in Eyes With Diabetic Retinopathy. PMC12488266. https://pmc.ncbi.nlm.nih.gov/articles/PMC12488266/
3. The UK Diabetic Retinopathy Electronic Medical Record Users Group Report 2: real-world data for the impact of cataract surgery on diabetic macular oedema. PubMed 28487377. https://pubmed.ncbi.nlm.nih.gov/28487377/
4. Khattab AM, Hagras SM, Lotfy NM. Pre-operative versus post-operative intravitreal aflibercept injection for management of DME in patients undergoing cataract surgery. Graefes Arch Clin Exp Ophthalmol. 2023;261(11):3223-3229. https://pubmed.ncbi.nlm.nih.gov/37329361/
5. Optimizing treatment for diabetic macular edema during cataract surgery. Front Endocrinol (Lausanne). 2023. https://pubmed.ncbi.nlm.nih.gov/36761187/
6. Society for Ambulatory Anesthesia Updated Consensus Statement on Perioperative Blood Glucose Management. PubMed 38517760. https://pubmed.ncbi.nlm.nih.gov/38517760/
7. Update on the perioperative management of diabetes mellitus. BJA Education. 2024. https://www.bjaed.org/article/S2058-5349(24)00049-0/fulltext
8. Centre for Perioperative Care. Guideline for Perioperative Care for People with Diabetes Mellitus. Updated December 2022. https://cpoc.org.uk/sites/cpoc/files/documents/2022-12/CPOC-Diabetes-Guideline-Updated2022.pdf
9. Management of macular oedema in diabetic patients undergoing cataract surgery. Int Ophthalmol. 2024;44(1):166. https://pubmed.ncbi.nlm.nih.gov/38557801/