Abstract
Along with the motor symptoms, Parkinson’s disease (PD) patients experience a wide range of non-motor problems including visual disturbances. These are multifaceted, but often underreported as such. In a visual survey questionnaire, 78% PD patients reported at least one problem related to vision or visuospatial functioning. The most frequent encountered problems are impaired contrast sensitivity, color discrimination, visuospatial processing, ocular or eyelid movements and diplopia followed by visual misperceptions and hallucinations. Some patients report dry eyes, ocular pain or photophobia. The pathophysiological basis of the visual disturbances is not completely understood. Changes in the visual cortex were detected with functional MRI before the visual symptoms were clinically evident. Further studies are necessary to determine how these changes will contribute to development of visual symptoms in PD patients. Other authors consider a dopaminergic deficit in the retina to be responsible for some of these symptoms, being known that dopamine is the major neurotransmitter in the amacrine and interplexiform cells in the retina. Visual hallucinations are likely to be a result of disruption across related yet diverse neural circuitry. The therapy is only symptomatic and not always satisfactory. It includes ophthalmological treatment and specific treatment for hallucinations. Optical Coherence Tomography (OCT) is a new investigation method who offers quantitative morphology of gross retinal histology. The thinning of the peripapillary retinal nerve fiber layer was observed in PD. Some studies mentioned that macular thickness measured by the OCT could be a promising biomarker of PD. This work shows how complex the visual problems in PD patients can be and the importance of a thorough and multidisciplinary approach.
Highlights
The nonmotor symptoms (NMS) of Parkinson’s disease (PD) have received a lot of attention in the last few years
Diplopia is one of visual symptoms that is included in the questionnaire. 21.9% of patients with PD reported diplopia to the questionnaire compared to 4.2% in the control group and most patients had not declared prior diplopia to the physicians (6)
Another study in Europe using NMS-Quest reported a prevalence of diplopia in PD patients of 18.2% and one study in China using the same questionnaire has found diplopia in 16.7% of PD patients (7)
Summary
The nonmotor symptoms (NMS) of PD have received a lot of attention in the last few years. First described by James Parkinson in the 19th century may play a significant role in determining the general quality of life of the patient. Despite this fact, they have still been underrecognized and undertreated (1). In the context of PD sensitive symptoms one can distinguish visual disturbances They frequently do not receive enough attention during the consultation neither from the physician, nor from the patient. Visual symptoms are underreported and multifaceted with various origin from the disturbed ocular motility to a retinal dysfunction or malfunction of attentional control networks in the brain (3,4). Ocular motor function in PD subjects fluctuates in response to treatment, which complicates ophthalmic management (2,4)
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