More to the eye than vision:
Why the eye is critical for health and performance
Detection of light in the eye gives us sight, but is also critical to the normal regulation of physiology and behavior. In the figure below we can see that detection of light in the eye of a mouse: (1) supports vision; (2) acts as a time cue for circadian and seasonal rhythms; (3) modifies behavioral states that help the mouse avoid predators and conserve energy; (4) adjusts pupil size to improve vision; (5) modifies the release of widely acting hormones melatonin and cortisol; and (6) has acute effects on arousal measures such as heart rate – probably as part of the light regulated behaviors.
So how does this affect people?
- Jet Lag.Trips across time zones place the internal clock and external time in conflict, making us mentally and physically groggy.
- Seasonal depression.Many people struggle with long winter nights, but some can benefit greatly from increasing their daily light exposure with morning light therapy.
- The lecture hall snooze.We have all felt sleepy in a dimly lit classroom despite having a coffee in hand and an exciting subject being presented
Even Darwin probably had the occasional snore during his then controversial presentation on the origin of species.
Why is this important in healthcare?
Because the eye is central to the normal regulation of physiology, eye disease can have serious consequences for our health and quality of life. However, we know very little about which eye diseases affect our physiology, how they affect us, and what we can do to minimize any negative effects.
Goal:To establish abnormalities in light-regulated physiology as part of the standard of care in Ophthalmology, and determine appropriate patient management approaches.
To achieve this goal we must: understand this function of the eye, how it is affected by different eye diseases, how that affects health and performance, and then find ways to minimize negative consequences of eye disease on health and performance.
Approach:To understand which kinds of eye diseases negatively affect physiology, and the mechanisms involved, we have been studying selected animal models. We have found that different retinal diseases have very different and system specific effects on physiology. In short, phenotype is not simply determined by gross retinal pathology, but by the specific molecular mechanism of disease, and the age at which function was lost.
As we advance this effort to the clinic, we will initially connect phenotype with disease mechanism by studying molecularly characterized patients. Ultimately, this means that treatment or condition management planning must be tailored to the disease mechanism. We are therefore also directing our effort to understand the mechanisms by which eye disease affects health, initially concentrating on the effects of disruption of the widely acting hormone melatonin.
Finally, we are studying which specific aspects of light-regulated physiology could contribute to long-term health issues, and how we might intervene to avoid those health issues. We are currently focusing on the effect of light on melatonin, a hormone that affects risk for type-2 diabetes and breast cancer.