King–Devick Test
The King–Devick Test (K–D Test) is defined by Mosby’s Medical Dictionary as a tool for evaluation of saccade, consisting of a series of test cards of numbers. The test cards become progressively more difficult to read due to variability of spacing between the numbers. Both errors in reading and speed of reading are included in deriving a score. Saccades are quick, simultaneous movements of both eyes.
The King–Devick Test was developed in 1976 by Alan King, O.D. and Steven Devick, O.D. as an indicator of saccadic performance as it relates to reading ability. In 1983, a sample of 1202 children ages six to fourteen was screened using the K–D Test. The study done by the State University of New York (SUNY) concluded that the test was quick and easy to score and could be administered by non-eye care practitioners. For more than 30 years, the King–Devick Test has been a proven indicator of oculomotor inefficiencies regarding eye movements during reading. The King–Devick Test (K–D Test) is utilized as a tool in schools, eye care and psychologist offices to help detect learning disabilities, including dyslexia.
The King–Devick Test is an objective, physical test based on the measurement of the speed of Rapid Number Naming (reading aloud a series of single digit numbers from left to right on three test cards), and screens for impairments of eye movements, attention, language, and other correlates of suboptimal brain function. The sum of the three test card time scores constitutes the summary score for the entire test. The test can be administered in less than two minutes. In 2011, researchers published study findings supporting the utility of the King–Devick Test as a sideline remove-from-play concussion screening tool.
Formats
Concussion
The King–Devick Test, a remove-from-play concussion screening tool, is a two-minute test that requires an athlete to read single digit numbers displayed on test cards, a computer, or an iPad and can be administered by coaches, athletic trainers, medical professionals and parents. Athletes must establish an individual preseason or pregame baseline. A baseline is the cumulative amount of time it takes to read the three test cards aloud. For baseline testing, the entire test should be administered twice. The fastest cumulative time of the two attempts with no errors is considered to be the baseline. Immediately or soon after a suspected head trauma, the athlete is given the King–Devick Test once and if the time to complete the test is any worse (longer) than the athlete’s baseline test time and/or if there are errors, the athlete should be removed-from-play and should be evaluated by a licensed professional. The test has relevance to sports such as: football, hockey, soccer, boxing, lacrosse, rugby, basketball and all other contact or collision activities. The King–Devick Test is used in youth leagues, high school and college athletic programs. The test is also used at the professional level in Arena Football League, the National Hockey League (NHL), Major League Soccer (MLS), and Major League Lacrosse (MLL).
In 2010, researchers from the University of Pennsylvania Perelman School of Medicine published a study in Neurology (journal) of an investigation of the King–Devick Test as a potential rapid sideline screening test for concussion in a cohort of 39 boxers and mixed martial arts (MMA) fighters. A pre-fight K-D test baseline was determined and a post-fight K-D test was also administered after bouts. Post-fight K–D time scores were significantly worse (higher) than pre-fight scores for participants who had sustained head trauma during the match. Additionally, statistical analysis showed that the K–D test had high test-retest reliability. The researchers concluded that the King–Devick Test is an accurate and reliable method for identifying athletes with head trauma, and is a strong candidate rapid sideline screening test for concussion.
In 2010, a longitudinal study published in the Journal of the Neurological Sciences was conducted involving 219 athletes from the University of Pennsylvania varsity football, sprint football, women’s and men’s soccer and basketball teams. Each subject underwent baseline King–Devick (K–D testing) prior to the start of the 2010-11 playing season. For athletes who had concussions during the season, K–D testing was administered immediately on the sidelines and changes in score from their baseline were determined. For the 10 athletes who had concussions, K–D testing showed worsening from their baseline score/time. Additionally, the effect of the physical exertion on K–D test performance was studied in a subgroup analysis of men's basketball-players who received K–D testing immediately following an intense two hour scrimmage. These athletes, none of which sustained concussion, did not show any worsening of their K–D score, but instead showed improvement from baseline even in the setting of post-workout fatigue demonstrating that the K–D test is robust to physical fatigue. This study of collegiate athletes provided further evidence in support of the K–D Test as a strong candidate rapid sideline visual screening tool for concussion.
In August 2011, Ralph Nader publicly called for the mandatory implementation of the King–Devick Concussion test in high school and youth sports. “Too many sports organizations, from little leagues to the professional level, continue to have their heads in the sand when it comes to concussion safety and prevention measures," said Nader. “The growing mound of research showing the often devastating long-term effects of sports-related brain trauma demands that we take proactive measures to protect our young athletes’ brains. The King–Devick test is a simple and objective sideline screening test that can be administered by coaches, trainers and parents.” Some sports medicine doctors and trainers have called the King–Devick test the “missing link” for practical sideline management of concussions due to its simplicity, objectivity and effectiveness.
In 2012, the K–D test was studied in the amateur New Zealand rugby athletes over the course of a competitive season. In this pilot study of 50 rugby athletes (mean age 19.3 years ± 4.0 standard deviation) published in Journal of the Neurological Sciences, the K–D test was able to accurately identify three players with witnessed head trauma who were subsequently diagnosed with concussion. By testing all athletes post-match, the K–D test was able to identify two players that had sustained a concussive injury that was neither reported nor witnessed. In this rugby cohort, the K-F Test was not only useful in identifying changes in players with witnessed head trama, but in identifying changes in players with an un-witnessed, suspected concussion by simply testing all players after contact play.
In 2012, the K–D test was included in a comprehensive review published in Current Neurology & Neuroscience Reports comparing sports-concussion testing tools. The review stated that the K-D test captures impaired eye movements and saccades, attention and language which involve the integration of functions of the brainstem, cerebellum and cerebral cortex and thus proposed that the K–D test has the potential to capture brain impairment not observed in standard neurocognitive testing. It reported that the K–D test can be administrated in the quickest amount of time (less than 2 minutes as compared to others requiring upwards of 20 minutes for test administration). The K–D test does not require a medical professional to administer, assesses more the 50% of the brain’s pathways and gives a definite and objective outcome measure making it practical for sideline use at all levels of sports.
Before the Fall 2012 football season, King–Devick test kits were donated to all Chicago Public Schools (CPS) high school football programs by the Dave Duerson Foundation to ensure that every CPS football team had an effective sideline remove-from-play concussion screening tool. The donation was made in an effort to contribute to a safer game of football in the memory of Dave Duerson who was a former Chicago Bears football player.
In 2013, the K–D test was investigated in a prospective observational cohort study of 37 (mean age 22.0 years ± 4.0 years) amateur New Zealand Rugby Union players across 24 games. There were 22 concussive incidents recorded over the duration of the competitive season. Five concussive incidents were witnessed and accurately identified by the K–D test. Routine post-match screening for concussion with the K–D test identified an additional 17 unrecognized incidents in which players had not shown, or reported, any signs or symptoms of a concussion but who had sustained meaningful head injury. This study further supports that the K–D test is sensitive to neurological changes such as those seen with sports-related concussion.
In 2013, a prospective study evaluated the K–D test in the Philadelphia Flyers professional ice hockey team. In this exploratory analysis of 27 athletes (mean age 28.0 years ± 5.0 years) two players tested rinkside immediately following concussion demonstrated worsened K–D test scores from baseline. For Sport Concussion Assessment Tool 2's (SCAT2) Standardized Assessment of Concussion (SAC) components, however, these athletes showed no differences between baseline and rinkside concussion testing, but reported symptoms of concussion. Additionally, at baseline testing for the cohort, lower scores for the SCAT2 SAC Immediate Memory Score and Overall SAC score were associated with greater (worse) times required to complete the K–D test. Both working and saccadic eye movements share closely related anatomical brain structures, including the Dorsolateral Prefrontal Cortex (DLPFC) an area vulnerable to injury in concussion and therefore may explain some of the eye movement and memory related symptoms in athletes and other patients with concussion.
In 2013, a study of the K–D test in a cohort of 47 high school football players during the 2012 football season was presented at the prestigious Association for Research in Vision and Ophthalmology (ARVO) annual meeting. During the season, three athletes sustained concussion and all demonstrated increased (worse) K-D test performance times when tested shortly after the on-field injury. K–D test times were worsened by 41%, 100% and 143% respectively in these three athletes. Test-retest reliability was analyzed using intraclass correlation coefficients (ICC) between baseline and end of season data and demonstrated high test-retest reliability, supporting previous studies. This study showed that the K–D test is effective as a rapid sideline tool to identify concussion at the high school youth sports level.
In 2013, a study comparing the Symbol Digit Modalities Test (SDMT) and the K–D test in a cohort of 16 mixed martial arts (MMA) fighters was presented at the European Neurological Society Annual Meeting. Fighters were given K-D Test at both pre-fight and post-fight by a single examiner. Changes in scores were compared for those with head trauma during the fight vs. those without. There was a modest correlation between head trauma during the match and worsening (increase) in K–D scores (r=0.54, p=0.015), the actual change (r=0.42, p=0.055) and the percentage change in K–D scores from pre to post-fight (r=0.50, p=0.025). There was only small to medium correlation between worsening of SDMT score (decrease) and K–D score. There was no correlation between SDMT scores and concussions during the match. This study concluded that the K-D test is vastly superior to the SDMT as a sideline determinant of concussion in MMA fighters.
In 2013, a study of the K–D test in a cohort of 96 collegiate athletes, 35 elite extreme snow sport athletes and 12 university non-athletes was conducted to examine the differences in baseline test scores between genders and across collegiate and extreme sport professional athletes using the K–D test. The finding were presented at the National Athletic Trainers' Association 2013 Annual Meeting. Each participant established a K-D baseline using the King-Devick Test Online System (KDTOS) on the K–D test iPad app. The researchers from Weber State University found that there was a significant difference between sport types. Extreme snow-sports (M=47.69, SD=7.58) were significantly slower than university football (M=42.85, SD= 8.19) and university men's hockey (M=36.43, SD=8.06). University women's soccer (M=46.45, SD=7.48) was significantly slower than university men's hockey (M=35.43, SD= 8.06). There was no significant difference in test time-score between athletes and non-athletes. No significant difference was found between male and female. The study concluded that the results show there are differences in time to perform the K–D test between sports. This could be due to the number of repeated, sub-concussive blows that are experiences by athletes in different sports and emphasizes the need for individual baselines to be established.
In 2013, a study of 127 collegiate football and men's and women's basketball investigating the K–D test as a sideline screening tool was presented at the American Academy of Optometry 2013 Annual Meeting. This study examined the effect of concussion on K–D test performance and the effect of physical exercise on K–D scores in the absence of concussion. The participants underwent K–D baseline testing at pre-season physicals. Football players with suspected head injury were immediately tested using the K–D test on the sidelines. Post-season testing was also performed. Basketball players were tested immediately following an intense 2.5 hour workout to test the effects of physical exercise on K–D performance. Sideline scores of concussed athletes (n=11) were significantly higher than baseline (36.5±5.6s, vs. 31.3±4.5s, p<0.005, Wilcoxon signed-rank test). There was no worsening in K–D scores after physical fatigue. Rather, in basketball players, K-D scores post-workout showed improvement (31.8±4.9 vs. 34.5±4.8, p<0.05, Wilcoxon signed-rank test). Post-season testing showed improvement of scores consistent with known learning effects of the K-D test as a performance measure (35.1±5.2s vs. 34.4±5.0s, p<0.05, Wilcoxon signed-rank test). Test-retest reliability was analyzed between baseline and post-season testing resulting in high levels of test-retest reliability. This study supports the K–D test as an accurate, reliable sideline tool to identify concussions.
In 2013, the British Journal of Sports Medicine published the Consensus Statement on Concussion the Sport: The 4th International Conference on Concussion in Sport held in Zurich, November 2012. The statement noted that in order to improve the SCAT2, future research should consider the inclusion of vision tests, specifically the King–Devick Test.
In 2013, Neurosurgery published an article underscoring the need for the K-D test, a basic yet highly predictive sideline test that can be performed by laypersons during a game to determine concussive as well as sub-concussive events. Specifically stating, "The need for sideline rapid assessment of mild head injury is fundamental to limiting the deleterious effects of repeated impacts to the head. The great majority of athletes are at the youth sports level and not in collegiate or professional sports, which leaves many important decisions to be made by parents and coaches on the sideline. This structural element of sport is unlikely to change since allocating medically trained people to youth sports will require unavailable financial resources. Accordingly, empowering adults to administer a simple, rapid, yet effective test is paramount to preventing repeated head injury. As increasing evidence suggests that even mild impact to the head can lead to accruing neuropathology, it may be prudent to routinely perform sideline testing for players involved in even modest collisions. This could help avoid return to play of athletes with sub-concussive impacts as knowledge about head injury continues to evolve."
In 2013, the Journal of Neurological Sciences published a study examining convenient tools to provide accurate and rapid information to assist in evaluating concussions as well as effective ways to assess and track recovery following the injury. The K–D test was compared with the Post-Concussion Symptom Scale (PCSS) and computerized neurocognitive composite scores in 35 adolescent concussion patients (age 16.1 ±1.7 years) over four clinical visits. K-D times improved with each visit during the period of concussion recovery and paralleled improvements in PCSS, reaction time and visual motor speed. The article concluded that the findings support the use of K-D testing in an acute setting and as part of a multidimensional approach to assessing concussion status during a potential long-term recovery period.
In 2013, the Journal of Child Neurology published a study assessing 10 youth football players immediately before and after their season to explore the effects of football participation on selected clinical measures of neurological function. Oculomotor performance was assessed by the K–D test, and was shown to improve moderately to significantly (P 1/4 .047-.115). This study showed that a 12-week season of youth football did not impair the postural stability, neurocognitive function or oculomotor performance measures of the participants.
In 2013, the National Institutes of Health funded a report, Sports-Related Concussions in Youth: Improving the Science, Changing the Culture. The report identified the K–D test as a tool to be used either by trained responders as part of an acute sideline or in-field assessment of by health care providers during subsequent clinical evaluation.
In 2014, the Journal of Sports Medicine and Physical Fitness published a study examining the K–D test as a screening tool for concussion when administered by layperson sports parents in a cohort of amateur boxers. The K–D test was administered to each athlete pre and post-fight by trained laypersons who were masked to the head trauma status of each athlete. The matches were watched by a ringside physician, who tested athletes with suspected head trauma with the Military Acute Concussion Evaluation (MACE). In the absence of concussion, post-fight KD scores were better than the best baseline score (41.0 vs 39.3s, p=0.34, Wilcoxon signed-rank test). One boxer sustained a concussion as determined by the ringside physician. This boxer was accurately identified by the layperson K–D testers due to a worsening in K–D test compared to baseline and an increased number of errors. This study supported the K–D test as a rapid sideline screening tool for concussion that can be effectively administered by non-medically trained laypersons.
In 2014, Sports Medicine published a systematic review of the literature in regard to the history, pathophysiology, recognition, assessment, management and knowledge of concussion. The review states that the task of the K-D tests requires integration of multiple sensory inputs, motor efforts and cognitive processes such as target selection, Sustenance of attention, spatio-termporal memory and expectation. It highlighted that poor oculomotor function has been determined as one of the most robust discriminators for the identification of an mTBI. The K–D test was recommended as part of the initial sideline assessment to identify athletes with concussion.
In 2014, Annals of Internal Medicine published a comprehensive clinical practice article, In the Clinic: Concussion to review the current evidence for prevention, diagnosis, treatment, and prognosis of concussion. The K-D test was recommended as a tool for rapid oculomotor examination that can be used in the office or on the sideline to determine impairment of eye movements associated with an acute concussion and that the 1-minute test is useful to determine removal from play.
In 2014, The Sport Journal published a study, Baseline Concussion Testing in Different Environments: A Pilot Study, in order to examine the reliability of baseline testing with King–Devick Test in different environments. Participants were tested in both quiet and loud environments. They found that there were no significant changes in KD scores between quiet and loud environments.
In 2014, a retrospective study featured in Neurology Clinical Practice examined King–Devick Test as a complement to components of the SCAT3. Baseline and post injury testing from University of Florida athletes for King–Devick Test, Standardized Assessment of Concussions (SAC) and Balance Error Scoring System (BESS) were explored. Among 30 athletes with concussion, King–Devick Test identified 79% of concussions, and SAC showed a ≥ 2 point worsening in 52% of concussed athletes. Combining K–D and SAC captured abnormalities in 89%; adding the BESS identified 100% of concussions. The study highlights the value of adding a visual test that measure neurologic dysfunction not captured by sideline cognitive or balance tests. Additionally correlations in the study between K-D scores and ImPACT visual motor scores at baseline were similar to previous studies. and support the validity of the K-D test as a test that requires visual function.
In 2014, Mayo Clinic investigated the K-D test in a study of 141 high school hockey players. Baseline, immediate post-concussion and post-season K-D test administrations were completed. During the season, 20 athletes reported head injury. All 20 had immediate post-concussion K-D times higher (worse) from baseline and scores in concussed players remained abnormal over time as postseason assessments for all but 2 were worse. To determine the impacts of fatigue and sub concussive hits on KD scores a subgroup of 51 non-concussed players were assessed before and after a game and showed no significant time change. The study also detected potential brain injuries in athletes who had not reported symptoms of concussion by demonstrating worsening King–Devick times at the end of the season. “The King–Devick test represents a rapid, accurate, and cost-effective tool to identify concussion on the sideline and make appropriate game-time, remove-from-play decisions,” said Dr. Amaal Starling, Mayo Clinic neurologist and co-investigator of the study.
In 2014, researchers at New York University School of Medicine (NYU) presented a study of Vision-Based Performance Testing as a Complement to SCAT3/Child-SCAT3 in Youth and Collegiate Athletes at the American Academy of Neurology Sports Concussion Conference. Members of a youth ice hockey and lacrosse league as well as collegiate athletes from NYU and Long Island University (LIU) were included in this prospective study examining the K-D test, SAC (cognition) and time tandem-gait (balance) tests. Baseline K-D scores improved with increasing age in the youth cohort. Among 12 athletes with concussion during the season, K-D worsened from baseline by an average of 5.2 seconds and compared to an improvement of 6.4 seconds in non-concussed controls (n=14). K-D showed the greatest capacity to distinguish concussed vs. control groups based on changes from baseline (ROC curve areas from logistic regression models, accounting for age= 0.92 for K-D, 0.87 for tandem, 0.68 for SAC, p=0.0004 for comparison of areas). Researchers concluded that "rapid number naming is a useful visual performance tool to diagnose concussed athletes at youth and collegiate levels. Adding a rapid and simple vision-based test to the cognitive and balance performance measures of SCAT3/Child-SCAT3 enhances detection capabilities of current sideline testing".
Reading
The King–Devick saccadic eye movement test is a clinical screening tool for eye movement dysfunctions. The test is easy to administer and has been incorporated in many visual screening protocol used by non-professionals. The test is also used in formal investigation for understanding learning related visual problems. Children attending New York Public schools were screened using the King–Devick Test and there was a significant correlation with their citywide achievement test scores and was significant for predicting those students in the lower 25% of the class for all grades.
The more educators can be educated in accurate detection of vision problems; more can be done in helping children achieve academically as well. Saccadic eye movement deficiencies can be improved with training and correspondingly reading performance can be improved. Performance on the King–Devick Test is related to reading performance as young as 5 and 6 year olds in kindergarten. In addition, the King–Devick Test has shown to be statistically and practically significant in the reading development in adults.
The King–Devick Test is a readily available and useful tool for assessing oculomotor functions, and its components can also be used for in-school eye-movement training purposes. The King–Devick Test comprises one demonstration card and three test cards, which contain several rows of random numbers that become progressively more difficult to follow with either spotting or tracking skills. The test is scored based on age, speed and accuracy. Participants are asked to read the numbers on the three test cards from left to right as quickly as possible without making any errors. The sum of the three test card times, along with number of errors reading the test cards are recorded. The score is compared to pass/fail normative data for subjects from 6 years old through adulthood.
Reading Remediation
The King–Devick Remediation software, based on the rapid number naming and eye movement task of the K-D test, has been studied as an in-school remediation tool to train the physical act of reading to improve reading fluency. Students in grades 2-4 were screened for reading inefficiency using the King–Devick Test. Subjects who failed the test were entered into the study. A verbalized reading fluency evaluation was administered to all subjects to serve as a measure of baseline and post-training reading performance. The training consisted of three 20 minute sessions (one hour total) per week for six weeks using the K-D Remediation software. The results of the study showed a statistically significant improvement in reading fluency among individuals who underwent training.
In 2014, Clinical Pediatrics journal published a study evaluating the effect of saccadic training using the King–Devick Remediation software on reading fluency. Participants in kindergarten through third grade received standardized reading fluency testing pre and post training. Training consisted of saccadic training using the King–Devick remediation software 20 minutes per day, three days a week for six weeks. Researchers found that those who received saccadic training using the King–Devick remediation software had significantly higher reading fluency scores after training. Also, their post training scores were significantly higher than the control group. The study concluded that saccadic training via the King–Devick remediation software can significantly improve reading fluency.
Severe Sleep Deprivation Functionality Prediction
In April 2012, a study was published in Neurology investigating the effect of severe sleep deprivation on the speed and accuracy of eye movements as measured by the King–Devick test. Neurology residents and staff from the University of Pennsylvania Health System underwent baseline K–D testing followed by post call K–D testing. The study concluded that the K–D test is sensitive to the effects of severe sleep deprivation on cognitive functioning, including rapid eye movements, concentration, and language function.
Multiple Sclerosis Quality of Life Measure
In 2012, neurologists from the University of Pennsylvania presented work examining the role of the K-D test as a measure of eye movements in multiple sclerosis (MS). In the distinguished presentation, The King–Devick Test of Rapid Eye Movements: A Bedside Correlate of Disability and Quality of Life in Multiple Sclerosis the relationship of rapid eye movements, visual function, retinal structure, and vision-specific quality of life status was compared in a cohort of MS patients to a group of disease-free controls. K-D scores in the MS group were significantly higher (worse) compared to the disease-free control group. The K-D test was shown to correlate well with binocular visual function, disability and vision-specific quality of life in MS. It was recommended that the K-D test be considered for inclusion in future MS trials as a rapid efferent visual function test.
In 2013, the King–Devick test was further studied in a larger cohort of patients with Multiple Sclerosis (MS) and presented at the Association for Research in Vision and Ophthalmology. The results show that the K-D test captures visual dysfunction, vision specific quality of life and neurology impairment in MS. K-D scores reflected work disability as well as retinal structure changes as measured by optical coherence tomography (OCT). Additionally, history of optic neuritis and abnormal binocular visual acuity, both common ocular complications of MS, were associated with worse K-D scores suggesting that the K-D test captures both afferent and effect components of vision. In 2014, the study was published in the Journal of Neurological Sciences.
Parkinson's disease Quality of Life Measure
In 2013, the King–Devick test was studied in a Parkinson's disease (PD) cohort at the Arizona Parkinson's Disease Consortium and the Mayo Clinic. PD patients were compared to patients with Essential Tremor (ET) and disease-free controls. K–D scores were significantly higher (worse) for the PD group as compared to the ET group and the control group even after adjusting for age and [...]. This showed that the K–D test may be a quick tool for quantifying visual and cognitive function in Parkinson's disease at bedside. The study was published in Parkinsonism & Related Disorders.
Hypoxia
In 2013, Mayo Clinic studied the King–Devick test as a tool for the early detection of hypoxia-induced cognitive impairment. The performance of 25 subjects on the K–D test was measured in normoxic (normoxia) conditions followed by hypoxic (hypoxia) conditions (8% O2 equivalent to 7101 m) and then again in normoxia. K–D test completion time after exposure to 3 minutes of hypoxia was significantly longer than the Baseline Test (54.5 ± 12.4 s hypoxic vs. 46.3 ± 10.4 s baseline). Upon returning to normoxia the completion time was significantly shorter than in hypoxia (47.6 ± 10.6 s post-test vs. 54.5 ± 12.4 s hypoxic). There was no statistically significant difference between baseline test and post-test times, indicating that all subjects returned to their normoxic baseline levels. SpO2 decreased from 98 ± 0.9% to 80 ± 7.8% after 3 min on hypoxic gas. During the hypoxic K–D test, SpO2 decreased further to 75.8 ± 8.3%. In this study the K–D test has been shown to be an effective test to detect hypoxic impairment at early pre-symptomatic stages. The K–D test may also be used to afford a reassessment of traditional measures used to determine hypoxic reserve time. The study was published in Aviation, Space, and Environmental Medicine. In October 2013, a Mayo Clinic press release quoted principal investigator Jan Stepanek, M.D., the Aerospace Medicine Program Director and Co-Director of the Aerospace Medicine & Vestibular Research Laboratory. "This study provides an objective indication of hypoxia that is involuntary, reliable and repeatable," Dr. Stepanek said. "This means that people can be tested for cognitive declines before having symptoms, because often people won't have symptoms until it is too late."