Exophoria : Understanding, Identifying, and Managing This Eye Condition

1. What is Exophoria

   Exophoria is a term used to describe eye misalignment or eye deviation. It refers to the tendency of the eyes to deviate outward when a person is not focusing on an object.

   Exophoria is considered to be a type of heterophoria, which is the tendency of the eyes to deviate from their normal alignment when not engaged in a specific visual task. It is different from exotropia, a condition in which one eye constantly turns outward, and the binocular vision is not maintained.

2. Importance of Understanding Exophoria

   Exophoria can have a significant impact on a person’s vision, comfort, and overall eye health. Understanding it is important for the following reasons:

   • Exophoria is associated with eye strain, headache, and discomfort. Understanding about it can be helpful in preserving and restoring binocular vision.
   • Early detection can be helpful for timely intervention and better outcomes.
   • Knowing about the severity of the condition and about the symptoms, an appropriate treatment option can be chosen.
   • Early intervention and understanding of exophoria can be helpful in preventing complications such as amblyopia or further visual discomfort.
   • Managing exophoria effectively can significantly improve the quality of life of a person.

   Having an understanding of exophoria can be helpful in improving the overall health.

1. How is Exophoria Different from Other Eye Conditions

   Exophoria shares symptoms with some of the eye conditions but is different from them in the following aspects.

   Direction of Eye Deviation

   • Exophoria: The eyes tend to drift outwards when not actively focusing. They can be aligned to focus at a single point with conscious effort, maintaining binocular vision.
   • Exotropia: It is a form of strabismus, in which one eye consistently turns outward, away from the other eye. It is difficult to maintain binocular vision, leading to double vision.
   • Esophoria: It is the opposite of exophoria. The eyes in esophoria have a tendency to turn inward when not actively focused. Here, just like exophoria, binocular vision can be maintained.
   • Strabismus: Also known as crossed eye or squint, it is a general term for eye misalignment. It involves constant misalignment of the eyes, leading to a lack of binocular vision.

   Consistency of Eye Alignment

   • Exophoria: It is intermittent and most noticeable during periods of visual fatigue, stress, or prolonged near work. It can be corrected with the brain’s fusion mechanism.
   • Exotropia: It is a constant condition in which one eye is consistently turned outward. It does not self-correct and requires a treatment to realign the eyes.
   • Esophoria: It is usually intermittent and can be controlled.
   • Strabismus: It is a constant misalignment and the eyes do not work together as a team. The misalignment persists despite circumstances.

   Symptoms and Impact

   • Exophoria: It leads to eye strain, discomfort, and headache during working hours.
   • Exotropia: It leads to double vision and can significantly impact visual function and quality of life.
   • Esophoria: It causes eye strain and discomfort but does not result in double vision.
   • Strabismus: It causes double vision, impaired depth perception, and social or self-esteem issues due to visible misalignment of eyes.

2. Prevalence and Age Group Affected with Exophoria

   Exophoria is relatively common, especially in individuals who do not have any other significant eye alignment issues like strabismus. The prevalence rates may vary, but it is estimated that a substantial portion of the population experience exophoria to some degree.⁽⁷⁾

   It can be detected in children during routine eye examinations. It is common in school children as there is an increased demand for near vision such as reading or using digital devices. Adults may continue to experience exophoria. It may get more noticeable during extended periods of near work or visual stress.

   Some studies suggest exophoria being slightly more common in females but the differences are generally not substantial.

The causes of exophoria are related to eye anatomy, visual system, or neurological factors. Some common causes of exophoria include:

• Refractive Errors: Refractive errors including hyperopia (farsightedness), can contribute to Exophoria. Hyperopic eyes may have to exert extra effort to maintain focus on near objects.⁽¹⁾ This may lead to an outward eye.
• Muscle Imbalance: Imbalance in the extraocular muscles that are responsible for controlling eye movements can lead to exophoria.⁽²⁾ If the muscles causing an outward movement of the eye are stronger than the muscles that cause the eye to move inward, exophoria may be the result.
• Visual Stress: Prolonged periods of near work such as reading or using digital devices can strain the eyes and lead to exophoria.
• Fatigue: General eye fatigue can cause the eye to align outward leading to exophoria. This often occurs when the eye muscles get fatigued and less able to maintain alignment.
• Neurological factors: Neurological conditions affecting the brain’s control of eye movements can result in exophoria. Damage or dysfunction in the brain region responsible for coordinating eye movement can disrupt proper eye alignment.
• Visual Adaptation: In some individuals, there may be naturally occurring exophoria, which represents the eyes’ preferred resting position. These individuals are adapted to this alignment and it may not cause any discomfort or harm.
• Excessive Use of Corrective Lenses: Using inappropriate prescription eyeglasses or using the wrong corrective lens can induce or exacerbate exophoria. Having a correct prescription is important to avoid strain and misalignment.
• Stress and Anxiety: Stress and anxiety can affect eye focusing and alignment. During periods of stress, individuals may experience temporary exophoria.
• Heredity: If the family member has a history of eye misalignment or strabismus, the likelihood of experiencing exophoria may increase.⁽⁴⁾
• Injury: Head injury increases the risk of eye coordination.⁽³⁾

Exophoria may be asymptomatic or minimally symptomatic. It may not always require treatment. However, if exophoria causes discomfort, eye strain, or headaches, it can be managed with approaches like vision therapy, specialized eyeglasses, or exercises prescribed by an eye care professional. Symptoms of exophoria include:

• Eye strain especially during activities requiring prolonged near focus such as reading, writing, or doing digital activities.
• Discomfort around the eyes or forehead described as aching and tiredness.
• Frequent and recurrent headaches, particularly in the forehead.
• Double vision or sensation of ghosting.
• Reduced concentration in tasks involving prolonged near vision.
• Intermittent outward deviation of one or both eyes.

Depending on the type of exophoria people may find focusing on objects difficult. Problems with eye coordination may be difficult to notice. An ophthalmologist may be needed to diagnose exophoria. Diagnosing exophoria may involve:⁽⁵⁾

• Comprehensive Eye Examination: A comprehensive eye exam is conducted by an optometrist or ophthalmologist. It may involve:
  • Visual acuity test to determine clarity of vision
  • Refraction test to assess refractive errors such as hyperopia or myopia
  • A cover test is performed in which the eye care professional observes the eye alignment when one eye is covered.
  • An ocular motility test is done to evaluate eye movement and coordination.
  • Assessment of health is done to rule out other eye conditions or diseases that may contribute to symptoms.
• Symptom Assessment: The eye care professional enquires about the symptoms experienced which may include eye strain, discomfort, headaches, or double vision.
• Near Point of Convergence (NPC): It assesses how closely an individual can focus on a near object without experiencing eye drift. It helps quantify the degree of exophoria.
• Prism Testing: A prism lens may be used to measure the magnitude of exophoria. It involves using prisms to determine the amount of prism correction needed to align the eyes.
• Refraction Assessment: It is done to ensure the underlying errors such as hyperopia are adequately corrected to address potential contributors to exophoria.

On confirming the diagnosis, the eye care professional can determine an appropriate treatment.

There are various approaches that are aimed at improving eye coordination, alleviating symptoms, and enhancing visual comfort during close-up tasks. The choice of treatment depends on the severity of exophoria, the presence of symptoms, and the specific needs of an individual.

• Vision Therapy: It includes a structured and supervised program of eye exercise and activities guided by an optometrist or vision therapist, designed to improve eye coordination and binocular vision. It may include activities such as convergence exercises, eye tracking exercises, and activities enhancing visual perception and processing.
• Prism Lenses: These are prescribed to help an individual with exophoria align their eyes more effectively. These lenses contain prisms that bend light in a way to reduce eye drift.
• Orthoptics Exercises: These improve eye muscle coordination and binocular vision. These exercises involve focusing on a near target, gradually bringing it closer to the eyes and then moving it away. They train the eyes to converge and diverge more effectively.
• Specialized Eyeglasses: Eyeglasses with specific lens designs such as bifocal or progressive lenses may be prescribed to provide additional assistance for near tasks. These can help reduce the effort required to maintain binocular vision during close-up work.
• Pencil Push-Ups: These involve focusing on a small object as it moves closer to the eyes ⁽⁶⁾. It improves convergence ability. These exercises can be performed at home as a part of the vision therapy program.
• Reducing Visual Stress: Good visual habits, such as taking regular breaks during prolonged near work, maintaining proper lighting, and using ergonomic setups, can be helpful in reducing visual stress and discomfort associated with exophoria.
• Surgical Intervention: It is considered a last resort when other methods have not been effective and exophoria is significantly affecting daily life.

Regular follow-up appointments with an eye care professional are essential to assess progress and make necessary adjustments to the treatment plan.

Treatment can be helpful in correcting exophoria. People may experience improvement in coordination right away or it may take around 12 or more weeks to notice improvement in vision.⁽⁶⁾ However, the individual results may vary.

Symptoms may recur post lack of sleep, illness, or activities that trigger exophoria which include reading or using a computer. Early intervention and a proactive approach needed to manage exophoria can give a brighter and more comfortable visual future.