Detection of distortions in images of natural scenes in mild traumatic brain injury patients

Mild traumatic brain injuries (mTBI) frequently lead to the impairment of visual functions including blurred and/or distorted vision, due to the disruption of visual cortical mechanisms. Previous mTBI studies have focused on specific aspects of visual processing, e.g., stereopsis, using artificial, low-level, stimuli (e.g., Gaussian patches and gratings). In the current study we investigated high-level visual processing by employing images of real world natural scenes as our stimuli. Both an mTBI group and control group composed of healthy observers were tasked with detecting sinusoidal distortions added to the natural scene stimuli as a function of the distorting sinusoid's spatial frequency. It was found that the mTBI group were equally as sensitive to high frequency distortions as the control group. However, sensitivity decreased more rapidly with decreasing distortion frequency in the mTBI group relative to the controls. These data reflect a deficit in the mTBI group to spatially integrate over larger regions of the scene.

High-resolution microarray analysis unravels complex Xq28 aberrations in patients and carriers affected by X-linked blue cone monochromacy

The human X chromosome contains ∼ 1600 genes, about 15% of which have been associated with a specific genetic condition, mainly affecting males. Blue cone monochromacy (BCM) is an X-linked condition caused by a loss-of-function of both the OPN1LW and OPN1MW opsin genes. The cone opsin gene cluster is composed of 2-9 paralogs with 99.8% sequence homology and is susceptible to deletions, duplications, and mutations. Current diagnostic tests employ polymerase chain reaction (PCR)-based technologies; however, alterations remain undetermined in 10% of patients. Furthermore, carrier testing in females is limited or unavailable. High-resolution X chromosome-targeted CGH microarray was applied to test for rearrangements in males with BCM and female carriers from three unrelated families. Pathogenic alterations were revealed in all probands, characterized by sequencing of the breakpoint junctions and quantitative real-time PCR. In two families, we identified a novel founder mutation that consisted of a complex 3-kb deletion that embraced the cis-regulatory locus control region and insertion of an additional aberrant OPN1MW gene. The application of high-resolution X-chromosome microarray in clinical diagnosis brings significant advantages in detection of small aberrations that are beyond the resolution of clinically available aCGH analysis and which can improve molecular diagnosis of the known conditions and unravel previously unrecognized X-linked diseases.

Colour, Luminance and Crowding

Three experiments were performed to assess the effect backgrounds have on object discrimination. Experiment 1 investigated the discrimination of foveally presented Gaborised objects and non-objects with and without a surrounding background. Thresholds were obtained by modulating the Gabor patches in 7 different directions, either isolating the L-M, S-(L+M) and L+M geniculate mechanisms, or stimulating these mechanisms in combination. The spacing between background Gabor elements and the object contour was chosen so as to not cause crowding, on the basis of previously published work with luminance stimuli. No differences were found between the Michelson contrasts required for threshold with or without a background, except when signals in the S-(L+M) and L+M were combined. The signals were combined at an elevation of 30° in DKL colour space, which resulted in a mixture with a proportionally strong chromatic signal. Experiment 2 investigated this finding further using three background conditions: no background, a sparse background and a densely populated background. Object vs. non-object discrimination thresholds were obtained for the L+M and S-(L+M) isolating directions, along with two conditions that combined them at DKL luminance elevations of 30° and 60°. In the 60° combination, the proportion of the chromatic signal was lower than in the 30° combination. Thresholds were found to be largely stable across chromatic and luminance conditions and background class, again with the exception of the combination at 30° elevation. The final experiment examined Gabor orientation discrimination over the same conditions as experiment 2 using a classical crowding paradigm, with a peripheral target and a set of three target-flanker separations. Crowding was most pronounced in the 30° combination. We conclude that when S-(L+M) signals above a certain level are combined with luminance signals, an increase in crowding results. This is likely to underlie the adverse effect of such signals on the discrimination of objects with backgrounds. [Research supported by BBSRC New Investigator grant to JM].

Nutrition, oxidative damage, telomere shortening, and cellular senescence: individual or connected agents of aging?

There is substantial and long-standing literature linking the level of general nutrition to longevity. Reducing nutrition below the amount needed to sustain maximum growth increases longevity in a wide range of organisms. Oxidative damage has been shown to be a major feature of the aging process. Telomere shortening is now well established as a key process regulating cell senescence in vitro. There is some evidence that the same process may be important for aging in vivo. Very recently it has been found that oxidative damage accelerates telomere shortening. It is therefore possible for us to propose as an outline hypothesis that the level of nutrition determines oxidative damage which in turn determines telomere shortening and cell senescence and that this pathway is important in determining aging and longevity in vivo. We also propose that telomeres in addition to their well-recognized role in "counting" cell divisions are also, through their GGG sequence, important monitors of oxidative damage over the life span of a cell. This may explain the evolutionary conservations of this triplet in the repeat telomere sequence unit.

Complications of neodymium:YAG cyclophotocoagulation in the treatment of open-angle glaucoma

A retrospective study was performed to determine the complications that occurred after cyclophotocoagulation. The condition of 33 eyes in 25 patients was observed from 1 month to 1 year after application of cyclophotocoagulation with a neodymium:YAG (Nd:YAG) laser for open-angle glaucoma. The number of treatment burns ranged from 16 to 50, and laser output energy ranged from 3 to 7 J. Complications included anterior uveitis in 14 eyes (42%), conjunctival injection in 12 eyes (36%), pain in 9 eyes (30%), and conjunctival hemorrhage in 5 eyes (15%). Corneal edema, intraocular pressure spikes, and corneal epithelial defects were each noted in three (9%) of the eyes treated, whereas cataracts developed in four (12%) of the eyes. Two eyes (6%) developed anterior segment ischemia with subsequent phthisis bulbi. Seven eyes (21 %) demonstrated no adverse reactions.

Early growth determines longevity in male rats and may be related to telomere shortening in the kidney

Maternal protein undernutrition can influence the growth and longevity of male offspring in the rat. We tested the hypothesis that these differences in longevity were associated with changes in the rate of telomere shortening. We found age-related shortening of telomeres in the liver and kidney but not in the brain of male rats. Growth retardation in postnatal life was associated with significantly longer kidney telomeres and an increased longevity. Conversely, growth retardation during the foetal life followed by postnatal catch-up growth was associated with a shorter life span and shorter kidney telomeres. These findings may provide a mechanistic basis for epidemiological studies linking early growth retardation to adult degenerative diseases.

Testing for carotid atherosclerosis

BACKGROUND

Optometrists frequently examine patients with the signs and symptoms of carotid artery disease. Referral for appropriate testing is mandatory in such patients.

METHODS

A review of the noninvasive tests which an optometrist can perform in the office is presented. The paper also describes the noninvasive tests which are performed in vascular clinics on patients in whom carotid atherosclerosis is to be ruled out. Arteriography, both conventional and digital subtraction studies, is also described.

RESULTS

A discussion of the appropriate medical and surgical treatment of patients with carotid atherosclerosis and the ocular manifestations of it is included in the paper.

CONCLUSIONS

With the increasing expansion of the scope of practice for optometrists, it is imperative that the signs and symptoms of carotid atherosclerosis be understood and managed appropriately. Preliminary tests for carotid arterial disease can be performed in the office, and referral for more extensive testing is better accomplished when those tests are understood by the referring optometrist.

Adverse reactions during retinal fluorescein angiography

BACKGROUND

Fast sequence retinal fluorescein angiography is a commonly employed diagnostic procedure within the optometric practice with relatively few serious adverse reactions. A retrospective study was conducted to document the incidence of adverse reactions with this procedure.

METHODS

A total of 1,173 patient charts who had undergone intravenous injection for retinal fluorescein angiography at a specility referral clinic or a referral clinic at a school of optometry. All patients had been intra-venously injected with 500 mg of sodium fluorescein in 25% or 10% solution. Adverse reactions were noted within the charts.

RESULTS

The most common adverse reaction were nausea (.8% of patients) and urticaria (.6% of patients), with other reactions including emesis and hypoglycemia. Extravasation of dye was noted in .2% of patients. No acute anaphylaxis was noted.

CONCLUSIONS

Fast sequence retinal fluorescein angiography is a relatively safe diagnostic test. However, one should be prepared to handle acute anaphylaxis within the office before administering the test because of previously published cases of life-threatening reactions.

Basic science research in optometry: are we adequately prepared?

Optometry has not traditionally emphasized basic science research. With the increasing responsibilities taken on for the health care of our patients, it is essential that optometry develop its own scientific base of knowledge on which to rely. The need for good scientific investigators, the need for support for basic science research, as well as the importance of long-range planning for basic science research in optometry are discussed.

A clinical comparison of visual field testing between Goldmann-type manual perimetry and the Marco MT-336 automated perimeter

A randomized, prospective clinical trial was performed to compare the Marco MT-336 automated perimeter with Goldmann-type manual kinetic perimetry. The number of true and false, positive and negative scotomas were counted, as determined by the findings on the Marco perimeter, assuming that the Goldmann perimeter was the "gold standard." For eight of the available programs, the accuracy specificity, sensitivity, positive predictive value and negative predictive value were determined. Chi-squared testing across and within programs was performed to determine the degree of agreement between the tests as to the presence or absence of scotomas. Additionally, McNemar's test was used to determine the amount of random disagreement between the two methods of testing. Although there are inherent difficulties in the analysis, the authors conclude that the Marco MT-336 perimeter is an accurate instrument for both detecting and ruling out the presence of visual field defects.

Pyogenic granulomas

Four cases of conjunctival pyogenic granuloma are described. The patients ranged in age from 12-30 years. Surgical trauma preceded the development of two lesions in one patient and a second patient presented with a positive history of recurrent styes, a chalazion, and a questionable history of trauma to the lid. The other two patients had no known antecedent events that would explain development of the lesions. A review of the literature is included in the discussion, which details the etiology, incidence, clinical presentation, histopathology, symptoms, clinical course, differential diagnosis, and treatment of pyogenic granulomas.

The effect of topical 2.5% phenylephrine and 1% tropicamide on systemic blood pressure and pulse

A prospective double-blind trial is described in which patients were given either 1% tropicamide, 2.5% phenylephrine, a combination of the two drugs, or a placebo. Blood pressure measurements and pulse rates were determined at 5, 10 and 15 minute intervals post-instillation. No significant change in systolic or diastolic blood pressures were determined for any of the treatment groups at any of the time intervals; however, a slight but significant decrease in pulse rate was noted in some of the treatment groups. The data are analyzed according to other variables. Factors which may have influenced the findings are discussed.