David Carden

Lutein supplementation over a one-year period in early AMD might have a mild beneficial effect on visual acuity: the CLEAR study.

PURPOSE We investigated the effect of daily supplementation with lutein (L) capsules on macular pigment optical density (MPOD) and visual acuity (VA) in patients with early age-related macular degeneration (AMD). METHODS A randomized, double-blind, placebo-controlled, two-center investigation of the effects of L supplementation in early AMD was conducted. The duration of the trial was 12 months. The centers were Manchester, United Kingdom and Maastricht, the Netherlands. L capsules (10 mg Ester) or a placebo (P) were taken daily. There were 72 patients (mean age 70.5 ± 8.7) assigned randomly to either L (n = 36) or P (n = 36) groups. MPOD using a flicker-based technique (MPS9000) and best corrected VA (LogMAR) were measured at the beginning and at 4-month intervals over the duration of the 12-month supplementation period. Blood serum samples were collected to monitor compliance. RESULTS At the end of the trial, an overall increase in the mean MPOD level was found for the L group from 0.38 ± 0.19 to 0.53 ± 0.22 optical density (OD) units. According to a mixed design ANOVA, this was statistically significant (P < 0.001). No change in MPOD was found for the P group. There was no significant change in VA in the L group (n = 36). The P group (n = 36) showed a statistically significant deterioration from 0.05 ± 0.13 to 0.09 ± 0.13 (P < 0.05). When comparing the change in VA over the supplementation period, there was a significant difference between the two groups (P < 0.05). To avoid ceiling effects, 2 subgroups of patients with VA worse than 0.06 at baseline were reanalyzed. In the L subgroup (n = 19) a mean improvement in VA from 0.23 ± 0.12 at baseline to 0.16 ± 0.10 at visit 4 was observed (P < 0.05). In the P subgroup (n = 14), there was a small deterioration from 0.18 ± 0.13 to 0.19 ± 0.12 (P = 0.70). The improvement in VA in the L subgroup was compared to the deterioration in VA in the P group and this effect reached statistical significance (P < 0.05). CONCLUSIONS L supplementation increases MPOD levels in early stage AMD patients. According to the VA measurements, the progress of the disease might be slowed in some patients with augmented levels of MP. (ClinicalTrials.gov number NCT01042860.).

Macular pigment optical density measurement; a novel compact instrument

A compact device to derive the optical density of human macular pigment (MP) using heterochromatic flicker photometry is described. The validity of the system is assessed by measuring the optical density spectra of MP in 12 healthy subjects and comparing this with well-established previously published values. The mean spectral absorbance characteristics of MP across subjects corresponds well with accepted values. As reported in other studies, our measurements show a wide variation of MP optical densities between individuals. In our technique within-subject variability is low; standard deviations are between 0.025 and 0.15 in most cases. The overall optical density of MP ranged from 0.08 to 0.84 with a mean of 0.496 and standard deviation of 0.257 at 460 nm. The stimulus size was 0.95 degrees. The unique feature of the technique is that it allows free viewing (not Maxwellian View) of the stimulus, it can be conducted easily and quickly and does not need frequent re-calibration.

Correspondence between retinal reflectometry and a flicker-based technique in the measurement of macular pigment spatial profiles

A comparison of macular pigment optical density (MPOD) spatial profiles determined by an optical and a psychophysical technique is presented. We measured the right eyes of 19 healthy individuals, using fundus reflectometry at 0, 1, 2, 4, 6, and 8 deg eccentricity; and heterochromatic flicker photometry (HFP) at 0, 0.5, 1, 2, 3, 4, 5, 6, and 7 deg, and a reference point at 8 deg eccentricity. We found a strong correlation between the two techniques. However, the absolute estimates obtained by fundus reflectometry data were higher than by HFP. These differences could partly be explained by the fact that at 8 deg eccentricity the MPOD is not zero, as assumed in HFP. Furthermore, when performing HFP for eccentricities of <1 deg, we had to assume that subjects set flicker thresholds at 0.4 deg horizontal translation when using a 1-deg stimulus. MPOD profiles are very similar for both techniques if, on average, 0.05 DU is added to the HFP data at all eccentricities. An additional correction factor, dependent on the steepness of the MPOD spatial distribution, is required for 0 deg.

Macular pigment measurement in clinics: controlling the effect of the ageing media

We report a series of experiments designed to ensure that Macular Pigment Optical Density (MPOD) measurements obtained with a clinical instrument are not influenced by lens yellowing and ocular media optical density. These effects were determined in six subjects using seven Lee Colour Temperature Correcting filters to simulate changes in the transmittance of the ocular media with age. Calculated simulated age matched the data linking age and optical density reported in the literature, and the MPOD was independent of simulated age. The instrument allows an estimation of MPOD to be made which is based only on a foveal (centre‐only) measurement rather than, as is conventional, making a comparison between foveal and peripheral measurements. We assessed the performance of this facility by comparing the centre‐only estimate of MPOD with that obtained from both central and peripheral measurements in 5616 eyes. The 95% limits of agreement for the two estimates was 0.13 OD units.

Lesions of Primate Visual Area V4 Produce Long-Lasting Deficits to Color Constancy

The effect of partial and near total lesions of visual cortical area V4 in primates was studied and the selective deficits induced were monitored over a period of several years. The lesions primarily affected colour constancy and did not affect simple hue or object discrimination. A severe relearning difficulty was found for simple hue discrimination following near total area V4 lesions, but hue discrimination thresholds were normal, whereas the colour constancy deficit remained. We conclude that area V4 contains a centre important for colour constancy.

Slowed dark adaptation in older eyes; effect of location

Purpose The rate of rod sensitivity recovery following a photobleach is a basic measure of the integrity of the outer retina. Rods are selectively impaired in aging and many disorders of the retina, notably Age‐Related Macular Degeneration (AMD). It is not known for certain whether the age‐related deficit is a pan‐retinal effect or if there are localised regions of impaired rod function. To address this important issue a dual arc stimulus was developed that samples sensitivity recovery in two retinal locations. Methods Arc‐shaped stimuli were presented on a black CRT screen at two locations, in the inferior visual field. Following a bleach, which was localised to the stimuli, recovery of sensitivity was measured using a modified method of adjustment technique. Neutral density filters were used to extend the luminance range of the CRT. Sensitivity recovery functions were fitted by non‐linear regression to a seven‐parameter model. Results Pairs of sensitivity recovery functions were generated from the stimuli. The cone phases of these functions were identical. The slopes of the S2 sections of the curves were steeper for the outer stimuli for both young (p < 0.001) and older (p = 0.003) observers. The difference between the two was the same for the two groups. The &agr; point was reached slightly earlier for the young observers and with the outer stimulus but neither of these effects reached statistical significance. The &bgr; point occurred earlier for the outer stimuli and this effect was statistically significant only for the older group. Conclusions The method places minimal demands on observers. The fact that rod sensitivity recovery is slowed in the older normal eye to the same extent in the two locations suggests that this deficit may be uniform across the retina. As there are localised losses in scotopic function in AMD, the technique is ideally suited to distinguishing impaired recovery dynamics due to normal ageing from those caused by disease. HighlightsRate of rod sensitivity recovery following a photobleach is a basic measure of retinal integrity.Rods can be selectively impaired in aging and diseases of the retina but it is unknown if the deficit is pan‐retinal.A dual arc stimulus was developed that samples sensitivity recovery in two retinal locations.Data suggest that although rod sensitivity recovery is slowed in the older normal eye, it is uniform across the retina.The technique could be used to distinguish between impaired sensitivity due to ageing or disease.

Guest editorial - Kulikowski Festschrift

This special issue represents the proceedings of a meeting to honour Janus Kulikowskis scientific career, held in September 2003 in Manchester. The meeting was universally regarded as successful, both scientifically and as a congenial occasion, appropriate to Januss colourful career. The presentations were of a high standard as one might expect of Januss associates and ex-colleagues. Equally importantly, the meeting captured the essence of Januss idiosyncratic approach to scienceöoriginal, sometimes inaccessible ideas, sharp discussion, uncompromising rigour and a dash of humour. The editors of this special issue would like to express their sincere gratitude to all the authors for their efforts in producing the papers and responding diligently to the referees. We offer this account of Januss career as a personalised view, tainted by anecdotes from Janus and others, all of which were almost certainly strongly biased. Nevertheless, if read in conjunction with his list of references, one can see a consistent thread of personalities in the chronology which should testify to its veracity. Janus first came to the UK in 1964 as a British Council Scholar at the National Physical Laboratory in Teddington and the Physiological Laboratory, Downing Street, Cambridge. Whilst there, he came into contact with Horace Barlow, Matthew Alpern, Gerald Westheimer, and many other contemporary vision scientists. He has particularly fond memories of frequent rather sharp discussions with John Robson. At St Johns college he met Paul Dirac who introduced him to the uncertainty principle, and from these discussions emerged the embryo of the notion of a compromise between space and spatial-frequency analysis in visual cortex. Guest editorial Perception, 2005, volume 34, pages 891 ^ 902