Influence of refractive error on pupillary dynamics in the normal and mild traumatic brain injury (mTBI) populations / Influencia del error refractivo sobre la dinámica pupilar en las poblaciones normales y las afectadas de lesiones cerebrales traumáticas leves (mTBI)

Purpose: There have been several studies investigating static, baseline pupil diameter in visually-normal individuals across refractive error. However, none have assessed the dynamic pupillary light reflex (PLR). In the present study, both static and dynamic pupillary parameters of the PLR were assessed in both the visually-normal (VN) and the mild traumatic brain injury (mTBI) populations and compared as a function of refractive error. Methods: The VN population comprised 40 adults (22-56 years of age), while the mTBI population comprised 32 adults (21-60 years of age) over a range of refractive errors (-9.00 D to +1.25 D). Seven pupillary parameters (baseline static diameter, latency, amplitude, and peak and average constriction and dilation velocities) were assessed and compared under four white light stimulus conditions (dim pulse, dim step, bright pulse, and bright step). The Neuroptics, infrared, DP-2000 binocular pupillometer (30 Hz sampling rate; 0.05 mm resolution) was used in the monocular (right eye) stimulation mode. Results: For the majority of pupillary parameters and stimulus conditions, a Gaussian distribution best fit the data, with the apex centered in the low myopic range (-2.3 to -4.9D). Responsivity was reduced to either side of the apex. Conclusions: Over a range of dynamic and static pupillary parameters, the PLR was influenced by refractive error in both populations. In cases of high refractive error, the PLR parameters may need to be compensated for this factor for proper categorization and diagnosis

Objetivo: Existen diversos estudios que han investigado el diámetro pupilar estático y basal en individuos con visión normal en todo el espectro de errores refractivos. Sin embargo, ninguno de ellos ha evaluado el reflejo dinámico pupilar a la luz (RPL). En el presente estudio, se evaluaron tanto los parámetros pupilares estáticos como los dinámicos en poblaciones con visión normal (VN) y en las afectadas de lesiones cerebrales traumáticas leves (mTBI), comparándolos en función del error refractivo. Métodos: La población VN incluyó a 40 adultos (de 22 a 56 años de edad), mientras que el grupo de mTBI incluyó a 32 adultos (de 21 a 60 años de edad) para un rango de errores refractivos (de -9D a + 1,25D). Se valoraron siete parámetros pupilares (diámetro estático basal, latencia, amplitud, constricción máxima y media, y velocidades de dilatación), comparándose bajo cuatro situaciones de estímulo con luz blanca (pulso tenue, punto tenue, pulso brillante, y punto brillante). Se utilizó el pupilómetro binocular con infrarrojos DP-200 de Neuroptics (30 Hz de muestreo; 0,05 mm de resolución) en el modo de estimulación monocular (ojo derecho). Resultados: Para la mayoría de los parámetros pupilares y situaciones de estímulo, los datos se ajustaron a una distribución gausiana, centrándose el ápex en el rango miópico bajo (-2,3 to -4,9D). La respuesta se redujo a ambos extremos del ápex. Conclusiones: Para un rango de parámetros pupilares dinámicos y estáticos, el RPL se vio influenciado por el error refractivo en ambas poblaciones. En casos de error refractivo elevado, los parámetros de RPL pueden necesitar compensarse por este factor, para su debida categorización y diagnóstico

Influence of refractive error on pupillary dynamics in the normal and mild traumatic brain injury (mTBI) populations.

PURPOSE: There have been several studies investigating static, baseline pupil diameter in visually-normal individuals across refractive error. However, none have assessed the dynamic pupillary light reflex (PLR). In the present study, both static and dynamic pupillary parameters of the PLR were assessed in both the visually-normal (VN) and the mild traumatic brain injury (mTBI) populations and compared as a function of refractive error. METHODS: The VN population comprised 40 adults (22-56 years of age), while the mTBI population comprised 32 adults (21-60 years of age) over a range of refractive errors (-9.00D to +1.25D). Seven pupillary parameters (baseline static diameter, latency, amplitude, and peak and average constriction and dilation velocities) were assessed and compared under four white-light stimulus conditions (dim pulse, dim step, bright pulse, and bright step). The Neuroptics, infrared, DP-2000 binocular pupillometer (30Hz sampling rate; 0.05mm resolution) was used in the monocular (right eye) stimulation mode. RESULTS: For the majority of pupillary parameters and stimulus conditions, a Gaussian distribution best fit the data, with the apex centered in the low myopic range (-2.3 to -4.9D). Responsivity was reduced to either side of the apex. CONCLUSIONS: Over a range of dynamic and static pupillary parameters, the PLR was influenced by refractive error in both populations. In cases of high refractive error, the PLR parameters may need to be compensated for this factor for proper categorization and diagnosis.

Understanding the effects of mild traumatic brain injury on the pupillary light reflex.

The pupillary light reflex represents an optimal visual system to investigate and exploit in the mild traumatic brain injury (mTBI) population. Static and dynamic aspects of the pupillary light reflex were investigated objectively and quantitatively in the mTBI population. Pupillary responsivity was found to be significantly delayed, slowed and reduced, but symmetrical in nature, and with a smaller baseline diameter, as compared with normals. Several pupillary parameters also discriminated between those with versus without photosensitivity. Thus, dynamic pupillometry provides several objective biomarkers for the presence of mTBI and photosensitivity, gives insight into the global sites of neurological dysfunction and possible related mechanisms, and should result in improved patient care.

Quantifying pupillary asymmetry through objective binocular pupillometry in the normal and mild traumatic brain injury (mTBI) populations.

INTRODUCTION: Little is known about human inter-ocular pupillary asymmetry (IOPA). Thus, the purpose of the present investigation was to assess objectively static and dynamic IOPA in normals and in individuals with mild traumatic brain injury (mTBI). METHODS: The pupillary light reflex (PLR) was assessed in an adult population of normals and in those with mTBI using the Neuroptics DP-2000 binocular pupillometer. Four stimulus conditions were used to optimize the assessment. Two aspects of the pupil were assessed: baseline diameter prior to light stimulation and the dynamic amplitude of constriction following light stimulation. RESULTS: There was no statistical difference in either the static or dynamic IOPA between the two groups. Thus, the data were combined for a better global parameter estimate. The mean average static IOPA was 0.26 mm (SD = ± 0.20 mm) or 4.17% (± 3.29%). The mean average dynamic IOPA was dependent on the light stimulus condition, with the average across all four test conditions being 0.11 mm (± 0.10 mm) or 1.84% (± 1.70%). DISCUSSION: The inter-ocular pupillary effects of mTBI appear to be symmetrical rather than asymmetrical in nature. The findings provide clinicians and researchers a useful quantitative guideline to assess normal vs abnormal static and dynamic inter-ocular pupillary asymmetry (IOPA) in these two populations.

Objective Pupillary Correlates of Photosensitivity in the Normal and Mild Traumatic Brain Injury Populations.

OBJECTIVE: No objective vision biomarker for photosensitivity currently exists. The present study sought to uncover potential biomarkers for photosensitivity within the pupillary light reflex. METHODS: The pupillary light reflex was evaluated in those with mild traumatic brain injury (mTBI) and in normal individuals, with and without photosensitivity, under a range of test conditions. The Neuroptics DP-2000, infrared, binocular pupillometer was used for both binocular stimulation and recording. Twelve pupil parameters and 6 stimulus conditions were quantitatively assessed in 32 adults with mTBI and compared to 40 normal adult controls. RESULTS: Normal subjects with photosensitivity exhibited four significant differences (p < 0.05) as compared with their nonphotosensitive cohort: larger constriction amplitude, faster average constriction velocity, faster peak constriction velocity, and slower recovery time. mTBI subjects with photosensitivity manifested six significant differences (p < 0.05) as compared with their nonphotosensitive cohort: larger baseline diameter, larger minimum diameter, faster peak dilation velocity, faster T50 and T75 recovery times, and a larger pupil diameter at 6 seconds poststimulus. DISCUSSION: Several pupillometry parameters were significantly different in those with and without photosensitivity in both populations tested. These specific parameters could serve as potential, objectively based biomarkers for photosensitivity in these specific populations.

Comparison of pupillary dynamics to light in the mild traumatic brain injury (mTBI) and normal populations.

PURPOSE: To determine if mTBI adversely affects the pupillary light reflex (PLR). METHODS: The PLR was evaluated in mTBI and compared to normal individuals under a range of test conditions. Nine pupil parameters (maximum, minimum and final pupil diameter, latency, amplitude and peak and average constriction and dilation velocities) and six stimulus conditions (dim pulse, dim step, bright pulse, bright step, bright red step and bright blue step) were assessed in 32 adults with mTBI (21-60 years of age) and compared to 40 normal (22-56 years of age). The Neuroptics, infrared, DP-2000 binocular pupillometer was used (30 Hz sampling rate; 0.05 mm resolution) with binocular stimulation and recording. RESULTS: Different test conditions allowed for discrimination of different parameters. For any of the given six test conditions, five-to-eight of the nine pupillary parameters were statistically different (p < 0.05) between the two diagnostic groups. The most promising parameters for diagnostic differentiation were constriction latency, all pupillary diameters, average constriction velocity and peak dilation velocity. CONCLUSIONS: MTBI adversely affects the PLR. This suggests an impairment of the autonomic nervous system. The findings suggest the potential for quantitative pupillary dynamics to serve as an objective mTBI biomarker.

Photosensitivity in mild traumatic brain injury (mTBI): a retrospective analysis.

PRIMARY OBJECTIVE: To determine whether photosensitivity (PS) changes over time and, if so, what factors may be related to the change; furthermore, to determine whether tint density changes over time, all in mild traumatic brain injury (mTBI). DESIGN AND METHODS: A retrospective analysis of 62 patient records (aged 18-40 years) with mTBI and PS was conducted. All charts were obtained from the SUNY/College of Optometry clinics from 2004-2011. RESULTS: Fifty per cent demonstrated reduced PS over time, with most occurring after year 1 post-injury (40%). Promotion of PS reduction appears to be associated with the lack of spectacle tint usage (p = 0.01) and the use of contact lenses (p = 0.03). Inhibition of PS reduction appears to be associated with tinted lenses (p = 0.06), hyperacusis (p = 0.03), dry eye (p = 0.04), migraines (p = 0.03) and loss of consciousness at the time of injury (p = 0.05). Concerning tint density changes over time, 71% (p = 0.002) maintained the same degree over time, while 27% (p = 0.002) reduced and 2% waxed and waned. CONCLUSION: Neural adaptation to PS appears to be a long-term process. Tint usage may act to inhibit this adaptive process, while the use of contact lenses may act to promote it. These findings may provide guidance in the clinical management of photosensitivity in the mTBI population.

Corneal collagen cross-linking: an introduction and literature review.

BACKGROUND: This literature review analyzes the scientific evidence available regarding corneal collagen cross-linking (CXL) as a treatment option for progressive keratectasia. METHODS: A literature search was performed using dates from 1990 to August 2010 regarding CXL Specific areas of focus for the literature review include safety and efficacy of the procedure as a stand-alone treatment or when used in conjunction with Intacs® corneal implants (Addition Technology™) or photorefractive keratectomy (PRK). RESULTS: A total of 50 clinical trials and studies were identified, 20 of which met the inclusion criteria. Results of the included literature support the conclusion that CXL is a safe and efficacious treatment for progressive keratectasia. The results of CXL alone have shown stabilization or improvement in the maximum keratometry readings, best-corrected visual acuity, uncorrected visual acuity, and spherical and cylinder refractive measurements. CXL has been shown to enhance the effects of Intacs and has been proven successful when used in conjunction with PRK. CONCLUSION: CXL is an effective treatment for limiting the progression of keratectasia, thus reducing the need for penetrating keratoplasty. CXL has a similar side-effect profile and similar risk level as PRK.