Can Horner’s Syndrome Affect Both Eyes & Can Diabetes Cause Horner’s Syndrome?

Horner’s syndrome is a mixture of symptoms that are caused when there is a disturbance in the path of nerves that go from the brain to the face. The most common signs or symptoms are seen in the eye. It is a fairly rare condition. Horner’s syndrome can affect people of any age.(1)

Can Horner's Syndrome Affect Both Eyes?

Can Horner’s Syndrome Affect Both Eyes?

Horner’s syndrome often affects only one eye or one side of the face. But it is possible that both the eyes are affected at the same time and is known as bilateral Horner’s syndrome.

If the condition is unilateral and comparable with the normal eye, identifying Horner’s syndrome due to the presence of a sympathetic eye defect is simple. However, it is difficult to detect sympathetic bilateral defects because the primary signs of sympathetic nerves are drooping, pupil expansion, delayed re-expansion (dilation) and decreased response to cocaine eye drops. Detecting these signs may not only be clinically difficult as they may also be completely absent. In this regard, the diagnostic value of pupil size is only small, because only about a third of patients with unilateral Horner syndrome have a pupil diameter less than expected in the normal range, although they are always smaller than the normal eye.(2)

Can Diabetes Cause Horner’s Syndrome?

According to the research on dogs, diabetics are 20.4 times more likely to develop optic neuropathy than diabetics. Patients with diabetes are 86.3 times more likely to develop Horner’s syndrome than people without diabetes.(3)(4)


Some of the nerve fibers that connect the eyes to the brain make a detour. They run down from the brain, along the spinal cord. They emerge from the spinal cord at the level of the chest and then the run-up to the neck, through the skull and to the eye, next to the carotid artery. If these nerve fibers are interrupted anywhere on their path, Horner’s syndrome occurs.

Horner’s syndrome can occur alone or as a result of another disorder. The cause can be a disturbance in the neck or spinal cord, but also in the head or brain, such as B. the following:

  • Lung cancer
  • Other tumors
  • Swollen, pressure-sensitive cervical lymph nodes (cervical adenopathy)
  • Aortic dissection or carotid dissection (a tear in the arterial wall)
  • Thoracic aortic aneurysm (a bulge in the aortic wall)


Horner’s syndrome can be congenital.(2)


Horner’s syndrome attacks the eye on the side where the damaged nerve fibers lie.

Symptoms include the drooping upper eyelid (ptosis) and narrowed pupil (miosis). In some patients, the narrowed pupil affects vision in the dark. Most of those affected do not notice any change in their eyesight.

The affected side of the face may perspire less than normal or not at all and in rare cases is reddened.

In the congenital manifestation, the iris of the affected eye remains blue-gray, as at the time of birth.(5)


Eye drop test

Magnetic resonance imaging or computed tomography

Horner syndrome is suspected based on the symptoms.

To confirm the diagnosis “Horner syndrome” and to clarify the problem, the doctor carries out a two-part examination:

First, eye drops that contain small amounts of cocaine or other medicine (apraclonidine) are administered in both eyes.

If Horner’s syndrome is likely, a second exam will be done 48 hours later. The doctor gives Cathin drops in both eyes.

The reaction of the pupils can be used to determine whether Horner syndrome is likely and where the problem is.

Magnetic resonance imaging (MRI) or computed tomography (CT) of the brain, spinal cord, chest or neck is often prescribed to clarify whether there are tumors or other serious disorders that could cause nerve fibers between the brain and the eye to be interrupted.(5)

When Should You Go To The Doctor?

If Horner’s syndrome is suspected, a doctor must be consulted promptly. Typical warning signs that need to be clarified are narrowed pupils and a sunken eyeball, often associated with visual disturbances, pain in the area of the eye and excessive sweating. When these symptoms appear, there is most likely a serious medical condition that needs to be examined and treated if necessary. It is not always the Horner’s syndrome, but medical clarification is always necessary.

This applies in particular if the complaints appear to appear for no reason and persist over a longer period of time. People who have had a brain tumor in the past are particularly susceptible to the development of Horner’s syndrome. Nerve diseases and syringomyelia are also possible causes of the syndrome. It is best to speak to the responsible doctor if you count yourself among these risk groups. In addition to the family doctor, an ophthalmologist or a neurologist can also be consulted. In the event of a medical emergency, emergency medical treatment is required.(2)


If a cause can be identified, it will be dealt with. There is no specific treatment for Horner’s syndrome. Treatment is often unnecessary because the drooping of the eyelid is minimal.


  1. Khan Z, Bollu PC. Horner syndrome. StatPearls [Internet]: StatPearls Publishing; 2019.
  2. Smit DP. Pharmacological testing in Horner’s syndrome–a new paradigm. South African Medical Journal. 2010;100(11):738-740.
  3. Argüder E, Şentürk A, Hasanoğlu HC, Hasanoğlu İ, Kanbay A, Doğan HT. Unique case of pseudomembranous aspergillus tracheobronchitis: tracheal perforation and Horner’s syndrome. Mycopathologia. 2016;181(11-12):885-889.
  4. Foote BC, Michau TM, Welihozkiy A, Stine JM. Retrospective analysis of ocular neuropathies in diabetic dogs following cataract surgery. Veterinary ophthalmology. 2019;22(3):284-293.
  5. González-Aguado R, Morales-Angulo C, Obeso-Agüera S, Longarela-Herrero Y, García-Zornoza R, Cervera LA. Horner’s syndrome after neck surgery. Acta Otorrinolaringologica (English Edition). 2012;63(4):299-302.