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Rod and cone visual pigments of 11 marine carnivores were evaluated. Rod, middle/long-wavelength sensitive (M/L) cone, and short-wavelength sensitive (S) cone opsin (if present) sequences were obtained from retinal mRNA. Spectral sensitivity was inferred through evaluation of known spectral tuning residues. The rod pigments of all but one of the pinnipeds were similar to those of the sea otter, polar bear, and most other terrestrial carnivores with spectral peak sensitivities (k max ) of 499 or 501 nm. Similarly, the M/L cone pigments of the pinnipeds, polar bear, and otter had inferred k max of 545 to 560 nm. Only the rod opsin sequence of the elephant seal had sensitivity characteristic of adaptation for vision in the marine environment, with an inferred k max of 487 nm. No evidence of S cones was found for any of the pinnipeds. The polar bear and otter had S cones with inferred k max of $440 nm. Flickerphotometric ERG was additionally used to examine the in situ sensitivities of three species of pinniped. Despite the use of conditions previously shown to evoke cone responses in other mammals, no cone responses could be elicited from any of these pinnipeds. Rod photoreceptor responses for all three species were as predicted by the genetic data.

It has been argued that the development and aging of the different achromatic and chromatic visual pathways may proceed independently. We review here the evidence for such independent changes with particular emphasis on electrophysiological results. Changes in chromatic and achromatic visual processing throughout the life span were studied using visual evoked potentials (VEPs). VEPs were recorded in response to the presentation of patterns designed to preferentially stimulate achromatic and S-(L+M) and (L-M) chromatic mechanisms. Recordings were made in subjects aged 1 week to 90+ years. Longitudinal measurements were obtained from several infants and cross-sectional measurements were obtained from infants and older subjects. Responses to achromatic reversing patterns at low spatial frequencies appeared early and changed rapidly. Latencies of the achromatic reversal response decreased to mature values within the first 12-15 weeks of life. Responses to chromatic pattern onsets, however, appeared later (L-M: 4 weeks; S: 6-8 weeks) and changed continuously throughout the first year of life. Chromatic waveforms from 1 year to puberty appeared inverted relative to the adult waveform. The waveforms did not appear adultlike until about 12-14 years of age. The latencies of the major negative component of the adult response reached a minimum around 17-18 years of age. Throughout the remainder of the life span, VEP latencies steadily increased and amplitudes slightly decreased. Latencies of responses to chromatic pattern onsets increased more rapidly than latencies to moderate contrast achromatic pattern reversals.

Electroretinogram (ERG) flicker photometry was used to examine the photopigment complements of representatives of four genera of Canid: domestic dog (Canis familiaris), Island gray fox (Urocyon littoralis), red fox (Vulpes vulpes), and Arctic fox (Alopex lagopus). These four genera share a common cone pigment complement; each has one cone pigment with peak sensitivity of about 555 nm and a second cone pigment with peak at 430–435 nm. These pigment measurements accord well with the conclusions of an earlier investigation of color vision in the dog, and this fact allows some predictions about color vision in the wild canids. An additional set of measurements place the peak of the dog rod pigment at about 508 nm.

Using a spatial, forced-choice, matching protocol, we have measured observers' ability to equate the contrasts of sinusoidal gratings which vary along differing directions in a 3-dimensional color space. In a given experiment, the observer obtained a perceptual match between the contrasts of two gratings whose chromaticities or luminances varied along differing chromatic directions which were selected from among five axes: an achromatic luminance axis (lum), an isoluminant axis where only S-cone activation varied (S-axis), an isoluminant axis where L- and M-cone activation varied in a complementary manner (LM-axis), an axis where only L-cone activation varied (L-axis), and an axis where only M-cone activation varied (M-axis). Even though these chromatic axes were chosen to activate independent mechanisms involved in the early stages of spatiochromatic visual processing, and despite the distinctly differing appearance of patterns from variations along differing directions, we find that observers can reliably make such pairwise contrast matches. Furthermore there is reasonable consistency of matching contrasts among observers and the pairwise contrast matches exhibit the properties of homogeneity and transitivity. This observed homogeneity and transitivity allows, for each color direction, the specification of a single scaling factor which relates perceptual contrast to physical contrast.

Visual evoked potentials were recorded in response to spatiochromatic stimuli modulated in different directions in cone-activation color space from subjects with congenital and acquired color defects. This technique was effective for detection and classification of both mild and severe forms of congenital deficits. Results suggest that the visual evoked potential is useful for early identification of color abnormalities in acquired deficits such as diabetes and that it is sensitive enough to detect regional retinal losses of sensitivity (e.g., as in central serous choroidopathy). The spatiochromatic visual evoked potential provides a systematic and sensitive indication of different color-vision anomalies.

X-linked incomplete achromatopsia (XIA), also called blue-cone monochromacy (BCM), is a rare cone disorder that most commonly results either from one of two conditions. The first condition is a deletion of the locus control region (LCR) which is a critical DNA element that lies upstream of the L and M photopigment gene array on the X-chromosome and is necessary for expression of the photopigment genes. The second condition is an inactivating point mutation within the coding sequence of the remaining photopigment gene in an array from which all but one gene has been deleted. Many previous studies have concluded that affected individuals either have only rods and S-cones (Blackwell & Blackwell, 1957, 1961; Daw & Enoch, 1973; Hess et al., 1989) or have rods, S-cones, and another cone type that contains the rod pigment (Pokorny et al., 1970; Alpern et al., 1971). However, Smith et al. (1983) described individuals with XIA who had residual L-cone function. Here we report results for a subject with XIA who appears to have residual M-cone function. Genetic analysis revealed that he had apparently normal genes for M-cone photopigment thus leaving open the possibility that he has a contribution to vision based on expression of these genes at a very low level.