Vertical Heterophoria (Misalignment of the Eyes)

Vertical heterophoria, also known as misalignment of the eyes, is a visual disorder where the eyes slightly deviate from each other or cross when in a relaxed state. This can lead to blurred vision, fatigue, and headaches as the eye muscles are unable to perfectly align the eyes.

Heterophoria occurs relatively frequently, affecting an estimated 70–80% of the population. Keep reading to discover all about heterophoria meaning and more.

What is Vertical Heterophoria?

Misalignment of the eyes, also known as heterophoria, latent squint, or hidden squint, describes a visual disorder where the eyes are not optimally aligned when in a relaxed state. These terms combine to give the same heterophoria definition, where the visual axes of the eyes slightly deviate from each other even though they are directed at the same object.

Heterophoria results from an inaccuracy in the control of the eye muscles. Normally, these muscles work harmoniously to align the eyes precisely and enable sharp binocular vision. Binocular vision refers to the ability to see with both eyes simultaneously and create a single, three-dimensional image. This is a complex process requiring close cooperation between the visual apparatus and eye positioning. Therefore, heterophoria is a type of binocular vision dysfunction.

The visual apparatus includes all eye structures involved in the visual process and the underlying neural connections to the brain. This includes the eye lens, retina, optic nerve, and associated brain areas. Each eye captures an image slightly different from the other because each eye views from a slightly different angle. These differences between the images of the two eyes are known as binocular disparity.

Eye positioning refers to the position and alignment of the eyes relative to each other. For effective binocular vision, the eyes must be correctly aligned so they focus on the same point in the distance. This requires precise eye muscle work. When the eyes are not correctly aligned, it impairs binocular vision.

In heterophoria, this alignment is not correct. One eye may slightly move inward (esophoria) or outward (exophoria), or a slight vertical displacement (hyperphoria) may occur. Many people are affected by this misalignment without noticing it because the eye muscles and brain can compensate for the small deviations.

Causes of Vertical Heterophoria

Heterophoria has various causes that are classified into three main complexes: static, accommodative, and neurogenic.

• Static Heterophoria
  In the static complex, anatomical factors play a crucial role. These include the structure of the eye socket (orbit) and the position and nature of the supporting apparatus of the eyeball. Deviations in these anatomical components can lead to misalignment of the eyes, contributing to the development of heterophoria.
• Accommodative Heterophoria
  Accommodative heterophoria is often caused by refractive errors, visual disorders where the eye does not correctly focus light, resulting in blurred images on the retina. This means there are problems with the eye's refractive power that affect focusing (accommodation) on objects. The eye tries to compensate for nearsightedness by bulging the lens, causing the eyes to turn inward. A certain form of farsightedness can also cause accommodative heterophoria. In both cases, the eye's ability to adjust focus on near and distant objects is impaired.
• Neurogenic Heterophoria
  Neurogenic factors contributing to heterophoria include problems in transmitting visual impulses in the nervous system. This can result from nerve transmission disorders where signals are not properly conveyed. Additionally, impaired processing of these signals in ganglion cells (specialized nerve cells) or the central nervous system (CNS) can occur, leading to impaired or completely absent image processing. Reduced neurological processing of neural impulses typically results in the inability of the sensory fusion of images from both eyes, characteristic of heterophoria.

Heterophoria Symptoms

In most cases, heterophoria is only mild and often goes unnoticed as the brain can independently compensate for small eye misalignments. However, symptoms may occasionally occur, especially when tired, stressed, or after prolonged computer use without breaks. Here are some common heterophoria symptoms:

• Blurred Vision
  Misalignment of the eyes leads to blurred vision, especially during visual tasks such as reading or computer work. This blurred or fuzzy vision can be tiring and impair visual performance.
• Headaches
  People with heterophoria often complain of headaches caused by the effort to align the eyes to produce a clear image. These headaches may manifest in the forehead area or around the eyes.
• Neck Tension
  Unequal alignment of the eye muscles can cause tension in the neck and shoulder area as the body tries to compensate for the misalignment. This can lead to chronic neck pain and muscle tension.
• Double Vision
  A common symptom of heterophoria is double vision (diplopia), where an object is perceived as two separate images. This can make vision particularly disruptive and uncomfortable.
• Eye Fatigue
  The effort required to align the eyes for a clear image can lead to rapid eye fatigue, limiting visual activities such as reading or computer use.
• Difficulty with Spatial Vision
  Heterophoria can impair spatial perception as the eyes do not work well together. This can affect activities where spatial depth is important, such as driving or climbing stairs.
• Dizziness or Uncertainty
  Constantly trying to compensate for the deviation can lead to dizziness or a feeling of uncertainty, especially in situations requiring spatial vision.

How is Vertical Heterophoria Diagnosed

Diagnosing heterophoria requires a careful examination by an eye specialist. The following steps are usually involved in diagnosing heterophoria:

• Medical History and Symptoms
  The doctor begins with a thorough medical history, where the patient describes their symptoms and visual history. Questions about complaints such as blurred vision, headaches, double vision, and other visual discomforts are crucial to provide clues about heterophoria.
• Visual Examination
  The doctor conducts a comprehensive visual examination, including measuring visual acuity, determining refraction, and checking eye health. This examination helps rule out other possible causes of the symptoms and identify heterophoria.
• Cover-Uncover Test
  Eye tests are crucial to pick up eye dysfunction as quickly as possible. A crucial step in diagnosing heterophoria is the cover-uncover test. Each eye is alternately covered while the patient looks at an object. The doctor observes if one eye deviates when the other is covered. This test helps determine the type and degree of heterophoria.
• Prism Test
  In some cases, a prism test may be conducted to measure the exact deviation of the eyes. This allows the doctor to determine the strength of the required prism correction to align the eyes.
• Eye Movement Tests
  Special tests may be conducted to assess eye movements and the coordination of the eyes. These tests evaluate how well the eye muscles work and if there are deviations.
• Binocular Vision
  The patient's ability to achieve binocular vision is tested to check how well the eyes work together to form a sharp three-dimensional image.

Exercises to Alleviate Latent Squint

Special eye exercises can help with latent squint by strengthening the eye muscles and improving eye coordination. Examples of treatment for vertical heterophoria include alternating focusing on nearby and distant objects, drawing shapes with the eyes, or following moving objects.

• Focusing on Near and Distant Objects
  Sit in a quiet place and choose a close object (e.g., your finger) and a distant object (e.g., a window or picture on the wall). Focus on the close object first, ensuring it is sharp. Then shift your attention to the distant object, ensuring it is also sharp. Repeat this process 10–15 times, switching focus between the objects.
• Eye Movement Exercises
  Sit upright and focus on a fixed point in front of you. Slowly move your eyes up, then down, and then from side to side. Try to make the movements smooth and controlled without moving your head. Repeat this exercise several times.
• Eye Rolling
  Sit comfortably and close your eyes. Slowly roll your eyes clockwise, then counterclockwise. Repeat these movements several times.
• Saccadic Exercises
  Fixate on a point in front of you and mark another point in your peripheral vision. Quickly switch between these two points without moving your head. Gradually increase the speed of these movements.
• Pen Exercise
  Hold a pen or pencil at arm's length in front of your face. Focus on the tip of the pen and slowly bring it closer to your nose, keeping it in focus as long as possible without seeing double. Then slowly return to the starting position. Repeat this exercise several times.

It is important to perform these exercises regularly and be patient as it may take time for improvements to become visible. If you have severe discomfort or uncertainty, always consult an eye doctor for a professional assessment of heterophoria and advice.

Incidentally, regardless of whether you suffer from heterophoria, eye training is beneficial for strengthening the eye muscles and maintaining overall eye health.

Heterophoria Treatment

The method for correcting heterophoria aims to alleviate symptoms and make vision as comfortable and strain-free as possible. The use of prism glasses or a prism lens is often recommended. Here are some common heterophoria treatment options:

• Prism Glasses for Heterophoria
  Prism glasses for heterophoria, also known as prism lenses, are special visual aids equipped with prism lenses that deflect light rays in a specific direction. They are often used to correct heterophoria or other visual disorders where the eyes are not correctly aligned. By deflecting the light rays, these glasses help overlay the images from both eyes so the brain merges them into a single image. This helps reduce symptoms like double vision or blurred vision, making seeing more comfortable. It is important that prism glasses are individually fitted by a specialist to ensure they are effective and achieve the desired effect.
• Eye Muscle Training (Orthoptic Therapy)
  In some cases, targeted eye muscle training (orthoptic therapy) may be recommended to strengthen the eye muscles and improve the eyes' alignment. This therapy includes specific exercises aimed at improving the coordination of eye muscles. The aim is to enable the eyes to achieve better alignment and reduce symptoms. Orthoptic therapy is typically supervised by a specialist and can be helpful in alleviating the discomfort caused by heterophoria.
• Vision Training (Visual Training)
  Vision training, also known as visual training, includes exercises and activities aimed at improving vision skills. This training can help alleviate the symptoms of heterophoria by improving eye muscle strength and the ability to coordinate the eyes. It includes activities such as focusing on near and distant objects, tracking moving objects, and other exercises to improve visual skills.

The choice of the appropriate correction method depends on the individual symptoms and the degree of heterophoria. An eye specialist can conduct a thorough examination and determine the best course of action to alleviate symptoms and improve visual quality.

Conclusion

Misalignment of the eyes, also known as heterophoria, is a common visual disorder that can lead to various visual symptoms. Understanding the causes, symptoms, and treatment options is important to alleviate the discomfort caused by heterophoria. If you suspect you have heterophoria or experience visual symptoms, consult an eye specialist for a comprehensive examination and advice on the appropriate treatment options.