A 72-year-old with diabetes, cataract, and a request for new glasses
A 72-year-old man with a 15-year history of type 2 diabetes requests new glasses because his distance vision has worsened over six months. He takes metformin and gliclazide; his last HbA1c was 8.9%. Unaided acuity is 6/18 OD and 6/24 OS, improving to 6/12 and 6/15 with pinhole. Anterior segment shows moderate nuclear sclerosis and cortical spoking in both eyes. Dilated fundoscopy reveals background diabetic retinopathy with a few microaneurysms and dot haemorrhages in the mid-periphery, no clinically significant macular oedema on your slit-lamp biomicroscopy, and no neovascularisation. IOP is 18 and 17 mmHg. He asks whether new glasses will fix his vision and whether he needs to see anyone else.
1. Explain the causes of his reduced vision and how you would determine the contribution of each.
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Causes of reduced vision in this patient:
- Cataract - moderate nuclear sclerosis and cortical spoking. Nuclear sclerosis causes index myopia, which can explain a refractive shift and worsening distance vision over months.
- Diabetic retinopathy - background changes alone rarely cause this degree of acuity loss unless there is macular oedema or ischaemia. Your slit-lamp view is not sufficient to exclude centre-involving oedema.
- Refractive error - pinhole improvement from 6/18 to 6/12 OD and 6/24 to 6/15 OS indicates a significant refractive component, but the residual pinhole deficit suggests additional pathology.
- Other - consider dry eye, which is common and treatable, and check for any cataract-related glare.
How to determine the contribution of each:
- Refraction - perform a careful subjective refraction. If acuity improves to near 6/9 with correction, refractive error is a major contributor. Note that a myopic shift may be cataract-related and unstable, so warn him the prescription may change.
- Pinhole - already done; the residual deficit after pinhole points to media or retinal pathology.
- Dilated fundus examination - you have done this; document the level of retinopathy carefully using a standard grading scheme.
- OCT or fundus photography - you cannot exclude macular oedema clinically with confidence. Refer for OCT if available.
- Contrast sensitivity and glare testing - useful to quantify cataract impact.
Key point: do not attribute all the vision loss to cataract. In a diabetic with 6/24 pinhole acuity, macular oedema must be excluded before attributing the loss to lens opacity.
2. What referral and co-management plan do you put in place, and what do you tell him about his diabetes?
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Referral and co-management:
- Ophthalmology referral - non-urgent but timely (weeks, not months) for:
- Assessment of cataract and discussion of surgery.
- OCT to exclude centre-involving macular oedema, which your biomicroscopy cannot rule out.
- Formal retinopathy grading.
- GP/endocrinology - his HbA1c of 8.9% is above target. Poor glycaemic control accelerates retinopathy and increases cataract surgery risk. Write to the GP asking for review of diabetes management.
- Do not finalise a new prescription as a long-term solution if cataract surgery is likely; you can provide a temporary update for driving and daily function, with a clear review date.
- Driving - check whether he meets the visual standard for driving. If acuity with correction is below the standard, advise him to stop driving and notify the licensing authority as required locally.
- Review - 3–6 months or sooner if symptoms change; annual dilated review is the minimum for a diabetic with retinopathy.
What to tell him about his diabetes:
- His diabetes is the main modifiable factor in his eye health. Better control reduces progression of retinopathy.
- Rapid improvement in HbA1c can transiently worsen retinopathy, so this should be managed by his diabetes team, not by crash dieting.
- He should report sudden vision change, floaters, or flashes urgently - these suggest vitreous haemorrhage or retinal detachment.
- Blood pressure and lipid control also matter.
Exam point: the judgement call is resisting the request to simply hand over glasses. The pinhole result and the diabetic status mandate referral before you attribute the loss to cataract.