Panel 3: Natural Resources and Biodiversity

An international law of property will have implications on the development of natural resources, as well as implications for biodiversity around the world. Development of natural resources has an impact on national economic growth. A number of legal regimes currently exist that govern the environmental impacts of natural resource development and biodiversity protection. This panel will explore the intersections of property law and cultural and natural resources

Sideslip of the medial rectus muscle during vertical eye rotation

PURPOSE: The kinematics of eye rotation is not entirely elucidated despite two centuries of fascination with the deceptively simple yet geometrically complex nature of the movement. Recently, the traditional view that oculorotatory muscles except the superior oblique muscle exert straight pull on the globe has been challenged by the claim that the muscles also go through a connective tissue pulley-like structure that holds them steady during eye rotation. Although earlier studies failed to observe sideslippage at the posterior part of muscles, a finding supportive of the pulley hypothesis, the conclusions should not be taken as conclusive given short-comings in the techniques used in the studies. METHODS: The authors developed a novel method of image analysis to improve spatial resolution and applied the method for investigating the medial rectus muscle, the entire length of which can easily be identified in magnetic resonance images. RESULTS: Contrary to previous reports, vertical sideslippage was observed at the posterior part of the muscle during vertical eye rotation between two tertiary eye positions. Furthermore, the sideslip varied as a function of horizontal eye position, in accordance with the half-angle rule of Listing's law. CONCLUSIONS: These findings are more consistent with the traditional view of the restrained shortest-path model than with the pulley model and have further implications for basic and clinical understanding of ocular kinematics

Covering one eye in fixation-disparity measurement causes slight movement of fellow eye

In the subjective measurement of fixation disparity (FD), the subject fuses contours presented in the peripheral macular areas of both eyes (fusion lock). The position of the eyes relative to each other is monitored by means of two haploscopically seen vertical lines presented in the central macular area, one above and one below a binocularly seen horizontal line. The subject is instructed to shift one of the vertical lines horizontally until the two are aligned, while fixating their intersection with the horizontal line. It has recently been questioned whether the foveolae really are pointed towards the perceived intersection. In this study, we monitored the position of one eye while intermittently covering the fellow eye, while the subject maintained fixation of the intersection of the remaining vertical line and the horizontal line. We found slight differences in position of the measured eye, depending on whether the other eye was covered or not, i.e. depending on the presence or absence of fusion in the macular periphery. These differences were more pronounced in the non-dominant eye

Preoperative prism adaptation test in normosensoric strabismus

In 19 patients with normosensoric esotropia, the squint angles measured with the alternate cover test were compared with those after prolonged prismatic correction of the squint angle and with those after prolonged occlusion of one eye. All patients showed an increase of the squint angle after prism adaptation. The angle was generally smaller after diagnostic occlusion of one eye than after prism adaptation. We assume that the increase in the squint angle after prism adaptation is caused by an anomalous sensorial relationship between the two eyes that was not detected with the usual psychophysical tests. Surgery tailored to the squint angle after prism adaptation seems advisable in patients with normosensoric esotropia

Intraoperative Adjustment in Strabismus Surgery under Topical Anesthesia

We evaluated the one-stage intraoperative adjustment strabismus surgery with adjustable suture under topical anesthesia. Medical records of the patients who had intraoperative adjustment surgery under topical anesthesia for horizontal or vertical strabismus in our hospital from March 1997 to March 2003 with follow-up of 6 months were analyzed retrospectively. Of the 71 patients, 48 patients had exotropia, 16 had esotropia, and 7 had hyper- or hypotropia. The overall success rates were 85.9% at 1 week, 83% at 1 month, 78.9% at 3 months, and 76.1% at 6 months after surgery. The procedure was not stopped in any patients, and no serious intra-operative or postoperative complications were noted. Intraoperative adjustment strabismus surgery under topical anesthesia is a simple, well-tolerated and effective procedure

Acute Comitant Esotropia in a Child With a Cerebellar Tumor

We report a case of acute comitant esotropia in a child with a cerebellar tumor. A 3-year-old boy was referred for management of a 9 month history of acute acquired comitant esotropia. On first presentation, the patient's angle of esodeviation was 50 prism-diopters (PD) at distance and near fixation without any lateral incomitance. The cycloplegic refraction revealed +0.75 diopters in both eyes. Very mild bilateral papilledema was found on the fundus examination, but the neurological examination did not reveal any other pathological findings. Brain MRI showed a 5 cm mass located in the midline of the cerebellum as well as hydrocephalus. The mass was completely excised and histological examination confirmed the diagnosis of pilocytic astrocytoma. Despite neurosurgery, the patient's strabismus remained unresolved. One year after neurosurgery, both medial rectus muscles were surgically recessed by 6 mm, resulting in esotropia of 8PD at distant and near fixation without restoration of bifoveal fusion at follow-up 2 years after the eye muscle surgery. Therefore, acute onset comitant esotropia in a child can be the first sign of a cerebellar tumor, even without any other neurological signs and symptoms