The eye has many reflexes that help us see clearly, track visual targets, and more. Understanding these reflexes also helps doctors to diagnose health conditions, as some conditions can change the way our eyes respond to stimuli.
Why Are Our Eye Reflexes Important?
Many naturally occurring reflexes related to the eye serve important purposes. For example, they may help to optimize the amount of light that hits the retina, help to stabilize the images on the retina, or work to protect the eye from damage.
Generally speaking, a reflex continues to exist in a species for a reason, even if it sometimes works strangely in practice. For example, we may tear as an emotional response despite emotional trauma not having much to do with eye health.
Different Eye Reflexes
There are at least thirteen eye reflexes, including these:
- Pupillary light reflex
- Pupillary dark reflex
- Westphal-Piltz reflex
- Ciliospinal reflex
- Near/accommodative response
- Corneal reflex
- Vestibulo-ocular reflex
- Bell’s reflex
- Lacrimatory reflex
- Optokinetic reflex
- Oculocardiac reflex
- Oculo-respiratory reflex
- Oculo-emetic reflex
The basics of these reflexes are as follows:
Pupillary Light Reflex
This reflex is an automatic constriction of the pupil in response to light. It helps adjust how much light reaches the retina, working in conjunction with the pupillary dark reflex to somewhat optimize how much light the eye can take in based on current conditions.
Pupillary Dark Reflex
The pupillary dark reflex causes pupil dilation in response to darkness, helping the eye to absorb more light as needed. This dilation also can be triggered by non-visual stimuli, including loud noises or being pinched.
This reflex isn’t fully understood, named after being noted by researchers Von Graefe, Westphal, and Piltz independently. It is a reflex that causes pupillary constriction in darkness or when one closes their eyes to go to sleep, and it may be connected to oculomotor disinhibition.
This reflex causes pupillary dilation in response to noxious stimuli (a term that refers to stimuli that are associated with pain and potentially tissue damage), including being pinched on the face, neck, or torso.
Also called the near/accommodative triad, this is actually a trio of reflexes: the pupillary accommodation reflex, the lens accommodation reflex, and the convergence reflex, working together. In basic terms, this response is how the eye can redirect its gaze from a distant to nearby object, adjusting to accommodate and help improve the level of detail it can discern.
The corneal reflex causes both eyes to blink if one eye’s cornea receives tactile stimulation. In other words, if one cornea is touched or otherwise physically affected, it is a healthy person’s natural response to blink both eyes, not just the affected eye.
This reflex is a key part of tracking objects as the head moves, allowing the eyes to move the opposite of one’s head movements and still maintain a steady gaze. This is actually one of the easier reflexes to safely see in motion, as you can try focusing on an object and then move your head away.
The fairly complex movements required to maintain that gaze comes naturally to healthy humans, generally resulting in a fairly steady focus even if the head is moved quite fast.
This reflex refers to the natural inclination of the eyes to roll up if both eyelids are forcibly closed. While not every healthy person has this reflex, it is present in about 90 percent of the population.
It is much more obvious in people with certain disorders. Its presence or absence is frequently used to help diagnose various health issues.
The lacrimatory reflex is the tearing reflex, causing tears to secrete under certain conditions. The two stimuli most obviously connected to eye health that can cause tearing include bright lights and exposure to certain physical or chemical stimuli, such as smoke. We may also tear as a result of emotional upset, vomiting, coughing, and yawning.
This reflex helps to stabilize images on the retina by acting in two distinct phases: one where the eye slowly moves to pursue visual targets and another where it rapidly adjusts to focus on a particular target.
The oculocardiac reflex is a reflex in which physical stimulation to the eye or adnexa (an area related to the reproductive system that is down in the pelvis) causes a decrease in a person’s resting heart rate of about 10 to 20 percent.
This reflex happens as a result of pressure on the eye, pressure on a person’s orbit, or by stretching of the extraocular muscles. It causes a decrease in respiration, resulting in shallow breathing or even temporarily stopping breathing.
This is a reflex that can cause nausea and vomiting as a result of manipulating extraocular muscles. This is typically noticed as an effect of certain eye surgeries, where those areas may have been worked on and a patient wakes up nauseous.
The above is a significant amount of information and admittedly may be a bit difficult for a non-expert to parse. But a subject worth discussing related to these reflexes is reflex dysfunction, which describes when a person’s reflexes do not align with those associated with a healthy person.
If a person is suspected to have a health condition of some kind, especially related to the eye, a doctor can often check these reflexes to narrow down conditions a person might have. For example, checking a patient’s Bell’s reflex can help in the diagnosis of Steele-Richardson syndrome, Parinaud syndrome, double elevator palsy, thyroid eye disease, and more.
Depending on the reflex affected, reflex dysfunction may not be particularly detrimental on its own (although it may signal a more serious health condition), or it may significantly impact a person’s vision or overall quality of life. There are also different levels of dysfunction, with more severe dysfunction generally impacting a person more than milder dysfunction.
- Reflexes and the Eye. (August 2022). American Academy of Ophthalmology.
- Pupillary Light Reflex. (July 2022). StatPearls.
- Compensatory Increase of the Cervico-Ocular Reflex With Age in Healthy Humans. (November 2003). The Journal of Physiology.
- Eye and Head Movements and Vestibulo-Ocular Reflex in the Context of Indirect, Referent Control of Motor Actions. (June 2020). Journal of Neurophysiology.
- The Relationship Between Reflex Eye Realignment and the Percept of Single Vision in Young Children. (January 2021). Scientific Reports.