Optometric Evaluation of visual Performance in PTVS after Concussion and the Role of Vision Therapy in Rehabilitation of Visual Function.
Concussion is a traumatic brain injury (TBI) that affects the brain function in many levels and can become manifest with a variety of signs and symptoms. It can occur after an accident during every day activities and is very common in athletes during sports (especially sports with physical contact). Although cases with severe symptoms can immediately and easily be diagnosed (especially by neurologists), “subcases” with mild or no apparent symptoms can go undiagnosed, many times because the patient does not look for medical opinion and is left untreated until symptoms get worse and interfere with the patient’s quality of life. These patients can suffer from what is named a “Post Traumatic Vision Syndrome” and the symptoms usually persist for at least a 3-month period or longer. This is why an experienced clinical optometrist can play a significant role in the diagnosis (at least to suspect the existence of a problem) in early stage and management (at least with the mitigation of the visual symptoms) for these patients in collaboration with other medical specialists.
Because vision is a complex neurological function any impairment in the central nervous system (CNS) [including the midbrain, the occipital lobe, the Frontal Eye Fields or other brain structures (LGN, MLF, Superior colliculus) involved in the visual process and eye movements] can lead to visual problems. In the case of a concussion or any TBI, some visual functions can be disorganized and this can cause specific problems, mainly related to the continuous sensory-motor feedback process of vision, which enables an individual to interpret its environment, by decoding and binding visual information, and act in it through motion. In other words, a mild disconnection between the system “eye-brain” occurs and that can create a shift in the proper visual function and consequently affecting the person’s ability to accurately interact with its environment. The same can be the case in any kind of neural damage relative to the visual pathways no matter what the cause is.
– Persistent headaches (even after a long period of time)
– Confusion and discomfort in crowded places (disorientation, and problems with proprioception)
– Balance problems and postural changes (in more severe cases)
– Dizziness and vertigo
– Vomiting and/or nausea
– Cognitive impairment
– Memory problems
– Sleeping problems
– Blurred vision
– Double vision
– Low blinking rate with secondary dry eye symptoms
– Reading difficulties (changes in performance at school for children that didn’t have such problems before)
– Light and/or Motion (hyper) sensitivity
– Oculomotor difficulties following a moving object (tracking and pursuit movements)
– Saccadic latency and poor performance in specific tests
– Vergence and accommodative problems leading to eye strain and fatigue especially at close work (reading or working in front of screens). Usually a remote NPC accompanied poor PFC and a drop in the AA (Amplitude of Accommodation)
– Visual field defects
– Intermittent tropias (mainly EXO deviations)
In every patient with a history of brain injury or other neurological events, who presents with or without some of the previous visual or general symptoms, standard tests should be performed by the optometrist during the routine optometric examination. Big changes in the refractive status of such patients can occur, but as a general rule small steps in changing the refraction must be preferred. These patients have difficulties in rearranging space with a new prescription. It is the ability of visual spatial orientation, based on the subconscious discrimination and the feedback between the focal/central visual process and the ambient/peripheral visual process (the “driving part” of vision), that is mainly disturbed on these patients. The visual input of these two processes cannot be matched and, as a result, these patients lose their ability of visual spatial judgment and therefore their way of moving can change under the “new data” of space perception, through neuropostural adaptation mechanisms. Research based on neuroimaging techniques like fMRI or Visual Evoked Potentials (VEP) is used for the documentation of that clinical phenomenon.
Apart from the standard optometric examination including a detailed ocular and medical history (regarding the cause of the TBI and possible medication taken) refraction (objective with retinoscopy and subjective) and a thorough binocular vision assessment, other clinical tests that can be used providing the optometrist with additional information about the patient’s visual neural status are the following:
It is a test that is approved as the most appropriate rapid visual screening tool for the evaluation of patients who had a whiplash injury, a concussion or any other neurological defect that can affect saccadic eye movements. It is basically a test for attention for people that have lost the ability of concentrating while doing tasks that require focusing and accuracy on saccadic movements. Reading is such a task. Scoring for the K-D test takes into account the reading speed (time that takes to complete the task) and the number of errors (false positives) the patient does while reading specific numbers in a specific layout on a sheet of paper. Its sensitivity enables the diagnosis of mild concussion cases without symptoms, something that is called “a silent concussion” and this is an additional reason that enhances its clinical importance.
Another test, also used as a screening tool for concussion in a similar “examination philosophy”, is the MULES test (Mobile Universal Lexicon Evaluation System) consisting in naming pictures depicting fruits, vegetables, animals and other objects as fast as someone can do. Color processing and object identification is an additional variable for this test.
A test which requires special equipment device. A flickering light is presented to the patient in varying frequencies (Hz) and the patient is asked to report when the flickering stops. People with hypersensitivity to light (as in PTVS) perform in higher thresholds than average. The use of digital devices (computer screens, smart phones, etc.) may cause a discomfort to these individuals.
In more severe cases of a concussion or a brain damage due to a neurological event like a cerebrovascular accident or a cerebral palsy leading to hemiplegia, a shift in the perception of the position of the body’s midline can happen. It can concern both the horizontal and the vertical axis (x-y) or a combination of them. Postural changes can occur in these patients, tilting their body, by weight bearing, to one or the other direction. Walking problems can arise in such patients in terms of spatial perception (a tilted floor for example) making them insecure.
The test is very simple, it consists of the movement of an object, like a wand or a ball, crossing the midline of the patient’s body in varying axes (like the motility test) and ask the patient to report when the object’s position coincides with their midline, with the nose as a reference point. A shift towards one direction can be interpreted as a defective opposite side.
The use of Yoked prisms (bases at the same direction) and binasal occlusion have been proved to be a solution for many of these cases combined with other types of therapy for such problems.
Activation of the Vestibulo-ocular reflex (VOR) by voluntary turning of the patient’s head horizontally from side to side in a certain pace and amplitude of movement [in degrees(·)] while trying to keep the gaze in a central target can cause headaches and dizziness in patients with PTVS after 5-10′ of the cessation of the testing.
Anisocoria, impairment in normal pupillary function (miosis or mydriasis) and a RAPD can be a sign for a neurological defect in the midbrain, visual pathways, optic nerve or a sign following a neurological imbalance after a TBI. It should always be performed thoroughly by the optometrist and combined with other clinical findings or data provided by ocular history for a more extended clinical picture of the patient.
Ocular motility (EOM) and all standard tests for the evaluation of saccades and smooth pursuit (tracking) movements should always be performed thoroughly (DEM).
Visual field defects and constrictions can occur in individuals suffering from PTVS and this can alter the total visual performance and function of the patients in many aspects of their everyday life. Blind spots (scotomas) throughout the visual field can be reported by such patients. Static perimetry (Goldmann), Short Wave Automated Perimetry (SWAP) and Frequency Doubling Technology (FDT) are the most appropriate tools for a precise and complete visual field screening but the confrontation VF test can give useful information in less time if such clinical equipment is not available.
Full examination of binocular vision: Accommodation, convergence, positive and negative relative convergence and accommodation, MAF/BAF and vergence facility with lenses and prism flippers, fusion and stereopsis.
The objectives of vision therapy in patients with PTVS are the alleviation of symptoms eventually aiming at the improvement of the patient’s every day activities and its quality of life. Active Vision Therapy has been proved to be effective in the management of vision disorders following a concussion. There are plenty of research papers and bibliography supporting the efficacy of vision therapy on partial or full recovery of vision after a concussion leading to PTVS both for children and adult patients.
For all patients with vision disorders associated with PTVS, an appropriate vision therapy program should be scheduled aiming at the rehabilitation of the impaired visual functions. The usual methods of vision training can be applied. Special care should be taken in the correction of oculomotor dysfunctions and all the necessary exercises aiming at reconstructing the spatial mapping and rebuilt the balance in the sensory-motor feedback mechanism.
Usual tools (among many others) used for Active Vision Therapy can be: Brock string, Marsden ball, Hart charts, Vectograms, Tranaglyphs, Stereograms, (with Red/Green and Polarized Glasses), Prism and Lens Flippers, Mazes, Computer Orthoptics.
Other treatment options include the use of colored filters for light sensitivity and syntonic phototherapy is also recommended for some cases of PTVS.
Finally, the effectiveness of “functional” optical corrections, in terms of a more behavioural approach, using lenses and prisms (as mentioned above) should always be considered to be a good starting point for helping people suffering from PTVS.
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