Evidence for Active Control of Rectus Extraocular Muscle Pulleys

PURPOSE. Connective tissue structures constrain paths of the rectus extraocular muscles (EOMs), acting as pulleys and serving as functional EOM origins. This study was conducted to investigate the relationship of orbital and global EOM layers to pulleys and kinematic implications of this anatomy. METHODS. High-resolution magnetic resonance imaging (MRI) was used to define the anterior paths of rectus EOMs, as influenced by gaze direction in living subjects. Pulley tissues were examined at cadaveric dissections and surgical exposures. Human and monkey orbits were step and serially sectioned for histologic staining to distinguish EOM fiber layers in relationship to pulleys. RESULTS. MRI consistently demonstrated gaze-related shifts in the anteroposterior locations of human EOM path inflections, as well as shifts in components of the pulleys themselves. Histologic studies of human and monkey orbits confirmed gross examinations and surgical exposures to indicate that the orbital layer of each rectus EOM inserts on its corresponding pulley, rather than on the globe. Only the global layer of the EOM inserts on the sclera. This dual insertion was visualized in vivo by MRI in human horizontal rectus EOMs. CONCLUSIONS. The authors propose the active-pulley hypothesis: By dual insertions the global layer of each rectus EOM rotates the globe while the orbital layer inserts on its pulley to position it linearly and thus influence the EOM's rotational axis. Pulley locations may also be altered in convergence. This overall arrangement is parsimoniously suited to account for numerous aspects of ocular dynamics and kinematics, including Listing's law. (Invest Ophthalmol Vis Sci. 2000;41: 1280 -1290 I nitial attempts to mathematically model binocular alignment showed the importance to extraocular muscle (EOM) action of EOM paths and the pivotal mechanical role of orbital connective tissues. The need for EOM path data motivated early radiographic studies in monkeys 1 and humans, 2 suggesting that paths of rectus EOMs are stabilized relative to the orbit. A decade ago, Miller 3 used relatively low-resolution MRI with three-dimensional (3-D) reconstruction to demonstrate stability of rectus EOM belly paths throughout the oculomotor range

Evidence for Active Control of Rectus Extraocular Muscle Pulleys

PURPOSE. Connective tissue structures constrain paths of the rectus extraocular muscles (EOMs), acting as pulleys and serving as functional EOM origins. This study was conducted to investigate the relationship of orbital and global EOM layers to pulleys and kinematic implications of this anatomy. METHODS. High-resolution magnetic resonance imaging (MRI) was used to define the anterior paths of rectus EOMs, as influenced by gaze direction in living subjects. Pulley tissues were examined at cadaveric dissections and surgical exposures. Human and monkey orbits were step and serially sectioned for histologic staining to distinguish EOM fiber layers in relationship to pulleys. RESULTS. MRI consistently demonstrated gaze-related shifts in the anteroposterior locations of human EOM path inflections, as well as shifts in components of the pulleys themselves. Histologic studies of human and monkey orbits confirmed gross examinations and surgical exposures to indicate that the orbital layer of each rectus EOM inserts on its corresponding pulley, rather than on the globe. Only the global layer of the EOM inserts on the sclera. This dual insertion was visualized in vivo by MRI in human horizontal rectus EOMs. CONCLUSIONS. The authors propose the active-pulley hypothesis: By dual insertions the global layer of each rectus EOM rotates the globe while the orbital layer inserts on its pulley to position it linearly and thus influence the EOM's rotational axis. Pulley locations may also be altered in convergence. This overall arrangement is parsimoniously suited to account for numerous aspects of ocular dynamics and kinematics, including Listing's law. (Invest Ophthalmol Vis Sci. 2000;41: 1280 -1290 I nitial attempts to mathematically model binocular alignment showed the importance to extraocular muscle (EOM) action of EOM paths and the pivotal mechanical role of orbital connective tissues. The need for EOM path data motivated early radiographic studies in monkeys 1 and humans, 2 suggesting that paths of rectus EOMs are stabilized relative to the orbit. A decade ago, Miller 3 used relatively low-resolution MRI with three-dimensional (3-D) reconstruction to demonstrate stability of rectus EOM belly paths throughout the oculomotor range

Association between age at menarche and risk of myopia in the United States: NHANES 1999-2008.

We evaluate the effect of menarche on myopia in women in the United States (US). A cross-sectional survey and examination were conducted using data from the 1999-2008 US National Health and Nutrition Examination Survey (NHANES), and 8,706 women aged ≥20 years (95% confidence interval [CI], 44.23 to 45.37) were enrolled. Characteristics were compared between nonmyopic and myopic participants. Univariable and multivariable logistic regression analysis was performed to evaluate the risk factors for myopia. A minimum p-value approach was used to estimate the cut-off point for age at menarche. The prevalence of myopia was 32.96%. Mean spherical equivalent (SE) were -0.81 diopters (95% CI, -0.89 to -0.73) and the mean age of menarche was 12.67 years (95% CI, 12.62 to 12.72). In the crude logistic regression model, age (odd ratio [OR] 0.98), height (OR, 1.02), astigmatism (OR, 1.57) (all p < 0.0001), age at menarche (OR, 0.95; p = 0.0005), white ethnicity, being born in the US, higher level of education, and higher annual household income (all p trend <0.0001) were significantly associated with myopia. 1-year increments in age at menarche was associated with a 4% decrease in the risk of myopia after adjusting for age, height, body mass index (BMI), ethnicity, and astigmatism (OR, 0.96; 95% CI, 0.93 to 0.99, p = 0.0288). The cut-off value for age at menarche was 15 years by the maximum chi-square test (p < 0.0001). Age at menarche may attribute to myopia progression, along with other environmental and individual risk factors

Dome-shaped macula in children and adolescents.

PurposeWe sought to evaluate the incidence and characteristics of dome-shaped macula (DSM) in children and adolescents with myopia.MethodsA retrospective review of medical records was performed to identify subjects who were younger than 19 years with myopia of -3.0 diopters or greater. The results of optical coherence tomography images were analyzed to identify DSM. The height and diameter of the dome were measured. Age, best-corrected visual acuity (BCVA), and refractive error of study participants who exhibited DSM were compared with those of patients who did not.ResultsAmong the 1,042 eyes of 615 patients, eight eyes (0.77%) of seven patients had DSM. Six of these eight eyes were not highly myopic (i.e., less than -6.0 diopters of spherical equivalents). Additionally, the mean height and diameter of the identified domes were 146.50 ± 42.33 μm and 4779.75 ± 699.38 μm, respectively. Patients with DSM were significantly older (mean age: 15.88 ± 2.36 years) than patients without it (11.51 ± 4.60 years; p = 0.007). The youngest affected patient was 11 years old. There was no significant difference in refractive errors (p = 0.629) or BCVA (p = 0.314) between the two groups.ConclusionsAlthough the incidence in this study was very low, DSM was found even in children and adolescents. In addition, 75% of affected individuals were not highly myopic. These results suggest that inherent traits may be involved in development of DSM

Long-term results of augmented unilateral lateral rectus muscle recession for dissociated horizontal deviation.

We report the long-term surgical results of augmented lateral rectus muscle (LR) recession for dissociated horizontal deviation (DHD) without concomitant exotropia (XT) or esotropia (ET). This retrospective review included patients with DHD without XT or ET who underwent augmented LR recession and were followed-up for ≥12 months. Each patient's medical records were evaluated to identify their demographics, preoperative angle of deviation, surgical procedure, success rate, and reoperation rate. A total of 11 patients with DHD were included (median patient age at surgery, 6 years; interquartile range [IQR], 5 to 10 years). Four patients (36.4%) had a history of infantile ET while three patients (27.3%) had a history of unilateral cataract surgery for congenital cataract. The median preoperative angle of DHD in the unilateral eye was 20 prism diopters (PD) (IQR, 15 to 25 PD). The median amount of LR recession was 8.0 mm (IQR, 7.5 to 8.0 mm). Three patients (27.3%) underwent simultaneous surgery for dissociated vertical deviation. At the final examination after a median follow-up period of 32 months (IQR, 24 to 58 months), 10 patients (91%) showed successful alignment. The long-term successful alignment rate after augmented LR recession for DHD was good; thus, application of this technique is appropriate in patients with DHD

Increase in esodeviation under cycloplegia with 0.5% tropicamide and 0.5% phenylephrine mixed eye drops in patients with hyperopia and esotropia

Abstract Backgroud To evaluate the manifestations of increased esodeviation under cycloplegia with 0.5% tropicamide and 0.5% phenylephrine in children with hyperopia and esotropia. Methods We reviewed the medical record of 34 children with hyperopia and esotropia who underwent a prism alternate cover test before and after instillation of mixed eye drops containing 0.5% tropicamide and 0.5% phenylephrine between November 2014 and October 2015. Increased angle of deviation was defined as 10 prism diopters (PD) or greater deviation after cycloplegia. The factors related to increased angle of deviation were evaluated using univariable and multivariable logistic regression analysis. Results The median age was 5.0 years (interquartile range, 3.75 to 5.0) and 12 patients (35.3%) were male. The median manifested refractive (MR) was +2.13 diopters (D) (+0.92 to +4.47) and cycloplegic refractive (CR) was +3.50 D (+1.72 to +5.66). The median difference between MR and CR was +0.88 D (+0.50 to +1.28). Thirteen patients (38.2%) showed increased esodeviation under cycloplegia and all had accommodative esotropia. A larger difference between MR and CR was the only significant factor affecting increased esodeviation in both univariable (OR = 4.72, P = 0.029) and multivariable (OR = 5.22, P = 0.047) analyses. Conclusion Children with hyperopia and esotropia often showed an increased angle of deviation after instillation of 0.5% tropicamide and 0.5% phenylephrine. This phenomenon reminded the clinicians that cycloplegics can have a different effect on esodeviation and suggested that increased angle of esodeviation may help to reveal the latent deviation in some patients with hyperopia and esotropia