COGNITIVE IMPAIRMENT

Ophthalmologists need to be aware of the link between dementia and visual decline, and the potential for overlap and misdiagnosis of both, Joanna Jefferis MD told delegates attending the XXXVI UKISCRS Congress. Cataracts and cognitive impairment are both common age-related problems, and ophthalmologists are increasingly likely to encounter patients who have either, both, or forms of dementia that incorporate visual impairment, said Dr Jefferis, Claremont Wing Eye Department, Royal Victoria Infirmary, Newcastle, UK.

As dementia patients who display early visual issues can frequently present first to ophthalmology services, Dr Jefferis said it is important that ophthalmologists familiarise themselves with the types of cognitive conditions that have visual elements or mimic symptoms. “Visual symptoms can be the presenting feature of dementia, and can be either complex or simple, such as having difficulty reading, blurring of vision, recognising objects and visual acuity,†she explained. The most common forms of dementia are Alzheimer’s and dementia with Lewy bodies, which presents with prominent visual features such as hallucinations and visuospatial dysfunction. Parkinson’s disease dementia and the very rare Creutzfeldt-Jakob disease also have visual elements, she elaborated.

“Also, posterior cortical atrophy, a form of Alzheimer’s which affects the posterior and visual part of the brain, is a reasonably newly recognised problem which presents invariably first to eye care providers. It causes progressive reading and visuospatial problems. For example, they are able to perceive individual elements of a scene but not a whole scene at once,†Dr Jefferis commented.

She noted that as dementia and cataracts both share similar symptoms, they can frequently be misdiagnosed as each other. Common symptoms of both cataracts and cognitive issues include difficulties in negotiating steps, reading and recognising faces, blurred vision and glare while driving. So there is plenty of scope for misdiagnosis. When these patients have coexisting cataracts, it may be even more difficult to distinguish visual complaints due to cataract from those due to dementia.

“We may more commonly be getting the problem of cataracts muddled with cognitive impairment. This could lead to unnecessary surgeries,†she said quoting a number of research and case studies that backed this assertion up. One retrospective study of 22 patients (Cooper 2005) with the Heidenhain variant of sporadic CJD (sCJD) showed that 77 per cent had initially presented to ophthalmology services, and two of these patients had cataract extraction before the diagnosis of sCJD was made.

The study noted that as ocular intervention carries with it the risk of onward transmission, awareness of this condition among ophthalmologists is important. She also cited a separate case study of a 77-year-old female with visual issues including past history of retinal detachment, reporting seeing white lines and flowers, with a VA of 6/9 in the right eye and 6/12 in the left eye who was diagnosed with mild to moderate cataracts.

However, Dr Jefferis said following cataract surgery on the patient's left there was no real improvement in her symptoms and she reported visual hallucinations. “Following a number of cognitive tests, including Montreal Cognitive Assessment, which has a lot of visuospatial aspects, we were able to diagnose this patient as having dementia with Lewy bodies, and that had been the reason for the visual symptoms she had been experiencing,†she explained.

Can surgery improve cognition?

Dr Jefferis examined the hypothesis of whether cognitive function can be improved through cataract surgery in dementia patients. “We know that cognition gets worse with time and vision gets worse with time, and can be related to each other. So if we can improve vision, can we therefore improve cognition?†she asked. Looking at international research on the issue, Dr Jefferis said that there are studies that support a yes and a no answer.

However, upon careful analysis and looking at whether there were control groups involved in the studies, she said her opinion is that no, there is not currently sufficient evidence that cataract surgery can lead to a notable improvement in cognitive function. She also looked at the separate question as to whether cognitive function influences the visual outcomes of cataract surgery. While there is increasing evidence that cortical factors have a role to play in declining visual function with advancing age, Dr Jefferis said cognitively impaired patients appear to have equal visual outcomes to non-cognitively impaired patients following cataract surgery.

Quoting her own research on the results of cataract surgery in 100 patients aged 75 years and over with varying levels of cognition, she reported that those with the lowest levels of cognition had the poorest levels of visual acuity pre-surgery. Postoperatively, her early research findings suggest that the visual results are not significantly different between the three cognitively defined patient groups. Dr Jefferis acknowledged the challenges in differentiating dementia and cataract symptoms in elderly patients and encouraged ophthalmologists to be cautiously thorough in diagnosing and electing to treat cataracts in this cohort. Speaking to EuroTimes following her presentation, she said a multidisciplinary approach with ophthalmic, neurological and psychiatric input is an effective way to diagnose and manage complex visual problems in older people.