Denny Marcos Garcia

Spontaneous Eyeblink Activity

Spontaneous blinking is essential for maintaining a healthy ocular surface and clarity of vision. The spontaneous blink rate (SBR) is believed to reflect a complex interaction between peripheral influences mediated by the eye surface and the central dopaminergic activity. The SBR is thus extremely variable and dependent on a variety of psychological and medical conditions. Many different methods have been employed to measure the SBR and the upper eyelid kinematics during a blink movement. Each has its own merits and drawbacks, and the choice of a specific method should be tailored to the specific needs of the investigation. Although the sequence of muscle events that leads to a blink has been fully described, knowledge about the neural control of spontaneous blinking activity is not complete. The tear film is dynamically modified between blinks, and abnormalities of the blink rate have an obvious influence on the ocular surface.

Graves upper eyelid retraction.

Graves upper eyelid retraction (GUER) is the most common and characteristic sign of Graves orbitopathy. Despite being well recognized since the 19th century, GUER is still a subject of controversy. We review GUER, including historical aspects, diagnosis, methods of measurements, ocular surface abnormalities, etiology, and medical and surgical treatments. There is no consensus about the mechanisms of its etiology or the best surgical correction. There is a need for quantitative studies on the effects of GUER on lid movements.

Supramaximal Levator Resection for Unilateral Congenital Ptosis: Cosmetic and Functional Results

Purpose: To analyze the cosmetic and functional results of a large series of patients with unilateral congenital ptosis without spontaneous compensatory ipsilateral frontalis hyperaction who underwent supramaximal levator resection (SMLPSr). Methods: A multicenter retrospective review of 35 children (14 girls and 21 boys) of mean age 5.5 ± 3.6 SD years with unilateral congenital ptosis who underwent surgery in 3 different countries: Italy, n = 8; Argentina, n = 11; and Brazil, n = 16. Preoperative evaluation included measurements of upper eyelid margin reflex distance (MRD1) and levator palpebrae superioris muscle excursion, assessment of frontalis hyperaction, and ocular motility examination. At least 6 months postoperatively, photographs were used to measure the upper eyelid contour of OU. The spontaneous blinking amplitude and downward eyelid saccades of OU were quantified in a subset of 14 patients. Quantitative comparison among the 3 centers was performed with nonparametric 1-way analysis of variance (Kruskal–Wallis). Paired t tests were used to compare the pre- and postoperative measurements, and p value < 0.05 was statistically significant. Results: The mean preoperative MRD1 of the operated eyes increased from 0.5 ± 1.1 SD mm to 3.4 ± 0.84 SD mm (t = 15.9; p < 0.000001), consequently the eyelid positional asymmetry decreased from 3.1 ± 1.21 mm to 0.1 ± 0.86 SD mm (t = 16.5; p ⩽ 0.000001). Twenty-nine percent of eyelids had mild contour abnormalities and 31.4% showed some degree of lash ptosis. Spontaneous blinks were abnormal in 93% of the cases (eyelids). The amplitude of the abnormal blinks ranged from 12.9% to 65.4% (mean = 37.1%) of the contralateral eyelids. Downward eyelid saccades were reduced in 79% of the eyelids. The amplitudes the saccades ranged from 2.2% to 84.6% (mean = 54.8%). Conclusions: In unilateral congenital ptosis, SMLPSr effectively reduces the positional asymmetry between eyelids. Mild contour abnormalities and lash ptosis are the main complications of the surgery. Postoperatively, spontaneous blinks and downward saccades were reduced in most eyelids. The reduced postoperative eyelid kinetics indicates that only patients with normal upward Bell signs are good candidates for this procedure.

Distribution of spontaneous inter-blink interval in repeated measurements with and without topical ocular anesthesia

PURPOSE To determine if the distribution of inter-blink time intervals is constant with repeated measurements with and without topical ocular anesthesia. METHODS Inter-blink time was measured in 15 normal subjects ranging from 19 to 32 years (mean ± SD= 23.9 ± 3.20) with the magnetic search coil technique on 3 different occasions, the last one with topical ocular anesthesia. RESULTS One-way analysis of variance for repeated measurements showed that topical anesthesia significantly reduced the blink rate (blinks per minute), which was constant in the first two measurements (F=8.27, p=0.0015. First measurement: mean ± SD= 13.7 ± 7.8; second measurement: 13.1 ± 8.5 SD; with topical anesthesia: = 7.2 ± 4.6). However, distributions shape was not affected when the blink rate was reduced. The three distributions followed a Log Normal pattern, which means that the time interval between blinks was symmetrical when the time logarithm was considered. CONCLUSIONS Topical ocular anesthesia reduces the rate of spontaneous blinking, but does not change the distribution of inter-blink time interval.

Spontaneous Blinking in Patients With Graves’ Upper Eyelid Retraction

Purpose: To describe spontaneous blink kinematics in Graves’ upper eyelid retraction (UER). Methods: The magnetic search coil technique was used to record spontaneous blinks of 15 healthy subjects (aged 23–56 years, 15 eyelids) and 15 patients with Graves’ UER (aged 22–62 years, 15 eyelids) during a 5-min period of video observation, and the signals were digitized at 200 Hz (12 bits). Overall, a total of 2,798 blinks were recorded for the controls and 1,860 for the patients. The distance between pupil center and upper eyelid margin in the primary position of gaze (MRD) was measured with the Image J software. Results: The blinking rate of patients was lower than that of control subjects, with a mean (± SEM) blinking rate (blinks/min) of 13.0 ± 1.7 for patients and of 20.0 ± 2.1 for the controls (t = 2.58, P = 0.016). There were no statistically significant differences in blink amplitude between controls (22.7 ± 3.1°) and Graves’ patients (24.7 ± 3.3°). However, while only 22% of the blinks performed by controls were smaller than MRD, this rate was 78% for patients. In addition, in blinks larger than 25°, patients showed lower down-phase velocity than controls. Conclusions: Patients with Graves’ UER show reduced blinks rates and abnormal blink kinematics, which might be related to the development of exposure keratitis in this disease.

Lateral and medial upper eyelid contour abnormalities in graves orbitopathy: the influence of the degree of retraction.

Purpose: To determine the location of contour abnormalities in Graves upper eyelid retraction. Methods: Multiple midpupil angular eyelid distances of 75 upper eyelids of 55 patients (mean age = 41.7 ± 13.3 SD years) in the inactive phase of Graves orbitopathy were measured with a recently developed custom-made software. Sixty eyelids of 60 normal subjects were also measured as a control group. A contour peak was defined by the highest midpupil angular eyelid distance normalized (divided) by the superior limit of normality (mean + 2SD). Results: In 45 eyelids (60%), the peaks were lateral between 120° and 150°. For high levels of retraction, the peaks tended to be centrally located with a substantial number of medial deformities (30 eyelids). Although the lateral and medial peaks were not affected by exophthalmometry, there was a statistically significant increase of medial peaks when midpupil eyelid distance was greater than 6.75 mm (&khgr;2 = 5.20, p = 0.02). Conclusions: Lateral contour abnormalities are more frequent than medial deformities. With minor degrees of retraction, there is a predominance of lateral peaks. With higher degrees of retraction, the number of medial abnormalities is similar to the lateral ones.

Modeling upper eyelid kinematics during spontaneous and reflex blinks

To test a mathematical model for measuring blinking kinematics. Spontaneous and reflex blinks of 23 healthy subjects were recorded with two different temporal resolutions. A magnetic search coil was used to record 77 blinks sampled at 200 Hz and 2 kHz in 13 subjects. A video system with low temporal resolution (30 Hz) was employed to register 60 blinks of 10 other subjects. The experimental data points were fitted with a model that assumes that the upper eyelid movement can be divided into two parts: an impulsive accelerated motion followed by a damped harmonic oscillation. All spontaneous and reflex blinks, including those recorded with low resolution, were well fitted by the model with a median coefficient of determination of 0.990. No significant difference was observed when the parameters of the blinks were estimated with the under-damped or critically damped solutions of the harmonic oscillator. On the other hand, the over-damped solution was not applicable to fit any movement. There was good agreement between the model and numerical estimation of the amplitude but not of maximum velocity. Spontaneous and reflex blinks can be mathematically described as consisting of two different phases. The down-phase is mainly an accelerated movement followed by a short time that represents the initial part of the damped harmonic oscillation. The latter is entirely responsible for the up-phase of the movement. Depending on the instantaneous characteristics of each movement, the under-damped or critically damped oscillation is better suited to describe the second phase of the blink.

Two-dimensional Video Analysis of the Upper Eyelid Motion During Spontaneous Blinking

Purpose: To validate and to report the results of a new inexpensive video-based method to measure upper eyelid motion during spontaneous blinks. Methods: Spontaneous blinks were simultaneously recorded in 21 healthy adult subjects for 5 minutes with magnetic search coil (MSC) and a portable video system (VDS) composed by a commercial high-speed camera coupled to a laptop computer and a blue light-emitting diode. Agreement between the 2 methods was assessed using qualitative comparison of the eyelid motion traces and Bland-Altman plots. Results: The blink traces registered with both methods were virtually identical. With the either method, the relationship between amplitude and maximum velocity was well fitted by linear regression with mean r values = 0.81 (MSC) and 0.85 (VDS). Bland-Altman plots showed good agreement between methods. The mean ± SE differences of amplitude (0.06 ± 0.17 mm) and maximum velocity (5.0 ± 3.4 mm/s) were not significant. With the VDS, it was also possible to quantify the horizontal component of the blink movements. The amplitude of the horizontal shift of the eyelid during blinks was 40% of the vertical downward phase of the movement. Conclusions: Blinking kinematics can be precisely measured using a simple and inexpensive video system suitable for clinical settings.

Graded Müllerectomy for Correction of Graves Upper Eyelid Retraction: Effect on Eyelid Movements

Purpose: To measure the effect of müllerectomy from posterior approach on the amplitudes of spontaneous blinking and downward eyelid saccades. Methods: Spontaneous blinks and downward upper eyelid saccadic movements of 16 patients (23 eyelids) with Graves orbitopathy were measured before and after müllerectomy from posterior approach. A new video system was used to continuously register the blinking activity while subjects viewed a commercial movie for 5 minutes. Downward eyelid saccades (30° of downgaze) were also measured with the video system. Results: Müllerectomy had no effect on the amplitude of the blink. However, as the eyelid margins were significantly lowered by the surgery, the amplitude of the blink movements relative to the pupil center increased substantially. The number of movements occluding the pupil center increased from 0% to 13%. Due to the increased efficiency of blinking, the blink rate decreased. Surgery induced a mean increase of 1.1 mm of downward saccades. Conclusions: The effects of müllerectomy on the blinks are indirect and related to correction of eyelid retraction. The relative amplitude of blink movements increases and blink rate decreases. Müllerectomy does affect the downward eyelid saccades increasing the ability of the upper eyelid to relax on downgaze.

Spontaneous Blinking Kinematics in Patients Who Have Undergone Autogeneous Fascia Frontalis Suspension

ABSTRACT Purpose: To measure spontaneous blink metrics and brow motion in patients with congenital ptosis operated with frontalis slings with autogenous fascia lata. Methods: An infrared three-dimensional video motion analyzer was employed to simultaneously measure brow motion and spontaneous blinks of 17 patients with congenital ptosis who underwent frontalis sling with autogenous fascia lata and a control group of equal number of healthy subjects. A customized software identified and quantified the amplitude and maximum velocity spontaneous blinks eyelid and brown motion during a 5-minute observation of a commercial movie. The corneal status of the patients with and without lagophthamos was evaluated with slit-lamp biomicroscopy with fluorescein staining. Results: Lagophthalmos was detected on 13 (76.5%) patients. Out of these 3 (23%) showed signs of inferior superficial keratopathy despite the presence of normal (upwards) Bell’s phenomenon in all of them. Blink rate was significantly diminished in the patients. The distribution of interblink time was similar in both groups. The mean amplitude of the down-phase of the patients’ blinks was only 38% of the controls. The main sequence slope of the patients’ blinks was abnormally low. In controls brow motion was a minute and random event no related to blinks. In the patients, the mean brow amplitude was five times higher than in controls reaching 45% of the blink amplitude. Conclusions: Spontaneous blink amplitude and velocity are severely impaired in patients with fascia lata autogenous slings. After surgery blinking amplitude is linearly related to the amplitude of brow motion.