Post Traumatic Vision Syndrome

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Top Contributors - Yagdutt Yagdutt, Kim Jackson, Nupur Smit Shah and Carina Therese Magtibay  

Introduction

Post traumatic vision Syndrome occur after a traumatic brain injury(TBI), Cerebrovascular insult or a neurovascular incident( Cerebral palsy, multiple sclerosis, concussion, whiplash). Trauma influence vision depending on parts of brain and external eye structures involved. Muscle imbalances in extra ocular eye muscles affect visual function as it depends on both motor and sensory components of vision. Sensory component of vision is dependant on proper motor function. Extraocular muscles align our eyes allowing to use both eyes together to perceive and process information. Affected visual processing mechanisms cause altered ability to comprehend and process visual and sensory feedback causing dysfunction in vision. Following a neurological insult various symptoms related to vision like headaches, diplopia, vertigo, asthenopia, photophobia, inability to focus and tracking objects can be noticed.

Clinical Signs and Symptoms

Binocular vision and accommodative disturbances in vision are common after mild Traumatic brain injuries. Oculomotor deficits in accommodative and binocular vision dysfunctions may occur from damage to the cranial nerves( Oculomotor, trochlear and abducens nerve). Exotropia and Exophoria are common after a neurological event. There are also difficulty in convergence and difficulty in accommodation and increased myopia (Blurred near vision). Patient also suffer from oculomotor dysfunction leading to vision problems. Patient report to have symptoms like double vision(Diplopia)Dizziness, Nausea, eye Strain (asthenopia), Sensitivity to light(Photophobia) and perceived movement of print or stationary Objects.

In addition to visual motor function there could be balance and posture can be affected as there can be midline shift. In Case of Homonymous hemianopsia(Loss of Vision on one side) there is a midline shift affecting Balance and posture leading to instability and frequent falls. Due to mismatch between Visual processes and sensorimotor information there is spatial disruption affecting binocular vision and patient reporting vertigo, dizziness, and balance problems.

Symptoms generally are better in morning. Symptoms get worse with activity and in busy high visual sensory environment. Sleep disturbances are also noticed in Post traumatic vision syndrome .

Tests for Diagnosis

• Cranial nerve testing – motor weakness in Cranial nerve 3, 4, or 6 may be contributing to diplopia, or vertical imbalances.Most commonly patients with posttraumaic vision syndrome experience difficulties with eye tracking, eye teaming/convergence, and eye focusing problems, which may be noticed using the following tests:

• Nuclear eye movements (Ductions)- Ductions compromise of each eye separately with one eye covered. limited eye movement or Ductions informs us about neurological involvement of eye. there are six movements of eye.Abduction refers to the outward movement of an eye. Adduction refers to the inward movement of an eye. Supraduction / sursumduction / elevation. Infraduction / deosumduction / depression. Incycloduction /intorsion. Excycloduction / extorsion.
• Supranuclear eye movements –Supranuclear eye movement involves versions, pursuits, saccades, convergence and vestibulo-occular reflex. Supranuclear eye movements inform us about upper or lower motor neuron lesion caused by trauma.
• Visual field testing – can give information on any type of vision loss if any the patient is experiencing. If visual field is affected it can indicate towards condition affecting visual pathways from optical nerve to occipital lobe, tumours, Injury, Poor circulation in brain.
• Vision Test– using letters and shapes can help indicate possible neglect or field of vision loss thus indicating neurological condition. visual acuity test generally utilizes reading from a standardized chart (Snellen chart) or a card held 20 feet (6 meters) away thus indicating vision changes.
• Visual neglect testing – often present with Post traumatic vision syndrome with traumatic brain injury. Patient demonstrate neglect of one side of body.

• Aneisokonia testing – may show discrepancies in object size between eyes when you are looking at same object in same direction.

• Hirschberg test & Cover Test: test for ocular alignment where we try to use a light source in midline from 2 feet to reflect on patient eyes while instructing them to focus on light source. Reflection of light should appear as a pin point while light near the center of pupil in each eye.

Management

• Management strategies involve remediation of dysfunctions that were discovered during the assessment.Early treatment in post traumatic vision syndrome is advised to avoid compensatory changes.
• If vision changes are noticed referral to an optometrist is advised. Investigation to find out if prism lenses with or with out occlusion are indicated should be done to start rehabilitation early.Optical devices like lenses and prisms can be used to help improve spatial orientation, posture and balance, and address issues regarding convergence, focus and binocular dysfunction. Presence of Symptoms (Double vision, Headaches, Blurry vision, Dizziness or nausea, Difficulty in concentration, Inability to find beginning of next line when reading, comprehension problem when reading, Going away from objects when brought close to him, Visual memory problems) of post traumatic vision syndrome warrants referral to specialist.
• Vision exercises with optical devices help in effective management of the symptoms. . Different diagnostic methods like testing of saccades, convergence and Vestibulo-ocuar reflex can also be used for training vision. If Oculomotor dysfunctions are present oculomotor training through vision exercises has been shown to be beneficial. Computer based programs and video games have been shown to be beneficial in vision rehabilitation.

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