We see the world as three-dimensional, but because the retinal image is flat, we must derive the third dimension, depth, from two-dimensional cues. Image movement provides one of the most potent cues for depth. For example, the shadow of a contorted wire appears flat when the wire is stationary, but rotating the wire causes motion in the shadow, which suddenly appears three-dimensional. The neural mechanism of this effect, known as 'structure-from-motion', has not been discovered. Here we study cortical area MT, a primate region that is involved in visual motion perception. Two rhesus monkeys were trained to fixate their gaze while viewing two-dimensional projections of transparent, revolving cylinders. These stimuli appear to be three-dimensional, but the surface order perceived (front as opposed to back) tends to reverse spontaneously. These reversals occur because the stimulus does not specify which surface is in front or at the back. Monkeys reported which surface order they perceived after viewing the stimulus. In many of the neurons tested, there was a reproducible change in activity that coincided with reversals of the perceived surface order, even though the stimulus remained identical. This suggests that area MT has a basic role in structure-from-motion perception.

Abstract. Spectral attenuation and absorption coefficients of particulate matter and colocated hydrographic measurements were obtained in the Mid-Atlantic Bight during the fall of 1996 and the spring of 1997 as part of the Coastal Mixing and Optics experiment. Within the bottom boundary layer (BBL) the magnitude of the beam attenuation decreased and its spectral shape became steeper with distance from the bottom. Concurrently, the slope of the particulate size distribution (PSD) was found to increase with distance from the bottom. Changes in the PSD shape and the magnitude of the beam attenuation as functions of distance from the bottom in the BBL are consistent with particle resuspension and settling in the BBL, two processes that are dependent on particle size and density. For particles of similar density, resuspension and settling would result in a flattening of the PSD and an increase in the beam attenuation toward the bottom. In both fall and spring the magnitude of the particle attenuation coefficient correlates with its spectral shape, with a flatter shape associated with higher values of the attenuation. This observation is consistent with idealized optical theory for polydispersed nonabsorbing spheres. According to this theory, changes in the steepness of the particle size distribution (particle concentration as a function of size) will be associated with changes in the steepness of the attenuation spectra as a function of wavelength; a flatter particle size distribution will be associated with a flatter attenuation spectrum. In addition, the observed ranges of the beam attenuation spectral slope and the PSD exponent are found to be consistent with this theory.

The present review describes progress in addressing and solving several fundamental and applied problems involving optical oceanography. These problems include: primary productivity, ecosystem dynamics, biogeochemical cycling, upper ocean heating, and the impacts of anthropogenic disturbances on ocean dynamics. Technological advances in optical sensors and ocean observing platforms are being used to increase the variety and quantity of optical observations and to greatly expand their sampling capabilities in time and space. Remote sensing of ocean color from aircraft‐ and satellite‐borne instruments is vital to obtain regional‐ and global‐scale optical data synoptically. In situ observations provide complementary subsurface data sets with high temporal and spatial resolution. In situ observations are also essential for calibration and validation of remotely sensed data as well as for algorithm development and data assimilation models. Important challenges remain to synthesize regional and global optical data sets obtained from optical sensors and oceanographic platforms and to utilize these data sets in predictive models of oceanic optical, physical, and biogeochemical dynamics.

Biofouling is one of the primary limiting factors in terms of measurement accuracy and deployment longevity for oceanographic studies involving autonomous sampling. Copper can significantly reduce marine fouling for long-term optical sensor deployments in coastal and open-ocean environments. Copper can effectively replace previously used highly toxic chemical antifoulant methods. Copper-based antifouling systems can be employed with three types of optical sensors: 1) open, 2) enclosed or semienclosed, and 3) shuttered. Copper plates on open-faced backscattering sensors can enable deployment periods of longer than 60 days in coastal waters without biofouling. In addition, copper tubing on nine-wavelength absorption-attenuation meters (ac-9s) has extended measurement capabilities from about 10 days to greater than 60 days with no signs of biofouling in coastal waters. Implementation of copper shutters on optical sensors in open-ocean waters off Japan has resulted in extended deployment periods (410 days and possibly longer) for optical measurements whereas previous optical measurements in the open ocean were typically degraded within several weeks to at most a few months due to biofouling.

Sympathetic ophthalmia is a rare, bilateral granulomatous panuveitis following accidental or surgical trauma to one eye. The pathophysiology is not clearly understood, but is believed to be a T-cell mediated autoimmune response. Clinical presentation most often occurs within the first year after trauma; anteriorly it manifests as a chronic or acute uveitis with mutton-fat keratic precipitates, while posteriorly it is often accompanied by yellowish-white choroidal lesions or Dalen-Fuchs nodules. The mainstay of treatment consists of systemic anti-inflammatory agents such as oral corticosteroids, or other immunosuppressive agents. Newer treatments include intravitreal injections of steroids in combination with systemic therapy, periocular injections of steroids without systemic therapy, and injections of infliximab, an anti-vascular endothelial growth factor.