Age effects on saccadic suppression of luminance and color

Saccadic eye movements modulate visual perception: they initiate and terminate high acuity vision at a certain location in space, but before and during their execution visual contrast sensitivity is strongly attenuated for 100 to 200 ms. Transient perisaccadic perceptual distortions are assumed to be an important mechanism to maintain visual stability. Little is known about age effects on saccadic suppression, even though for healthy adults other major age-related changes are well documented, like a decrease of visual contrast sensitivity for intermediate and high spatial frequencies or an increase of saccade latencies. Here, we tested saccadic suppression of luminance and isoluminant chromatic flashes in 100 participants from eight to 78 years. To estimate the effect of saccadic suppression on contrast sensitivity, we used a two-alternative forced choice (2AFC) design and an adaptive staircase procedure to modulate the luminance or chromatic contrast of a flashed detection target during fixation and 15 ms after saccade onset. The target was a single horizontal luminance or chromatic line flashed 2° above or below the fixation or saccade target. Compared to fixation, average perisaccadic contrast sensitivity decreased significantly by 66% for luminance and by 36% for color. A significant correlation was found for the strength of saccadic suppression of luminance and color. However, a small age effect was found only for the strength of saccadic suppression of luminance, which increased from 64% to 70% from young to old age. We conclude that saccadic suppression for luminance and color is present in most participants independent of their age and that mechanisms of suppression stay relatively stable during healthy aging.     

Daytime levels of melatonin in patients with age‐related macular degeneration

Purpose: Melatonin (N‐acetyl‐5‐methoxytryptamine) (MT) is a hormone that acts as an antioxidant. It is produced by the pineal gland and within the retina; its release is blocked by light entering the eye. We examined whether MT daytime levels differ between pseudophakic patients with age‐related macular degeneration (ARMD) and pseudophakic subjects without any ocular pathology of the same age. Methods: A prospective, cross‐sectional, observational study was performed. Pseudophakic patients of the same age group were included. Patients underwent complete ophthalmic examinations and blood sampling between 08:00 and 10:00 hr. MT daytime value in the serum was the main outcome measure. Results: Sixty‐nine pseudophakic patients were included. Fifty patients with exudative and non‐exudative ARMD were in the study group while 19 patients were controls. Patients with ARMD had significantly higher daytime levels of MT (P = 0.003). There were significant differences in MT daytime levels between the exudative and non‐exudative forms (P = 0.009). MT values also correlated with the best‐corrected visual acuity (r = ?0.285, P = 0.019). Conclusion: These data indicate that pseudophakic patients with ARMD produce more MT during the day compared to pseudophakic subjects without ARMD. This may be caused by the reduced visual acuity in patients with ARMD, whereby less light reaches the photoreceptors, allowing MT secretion to continue during the day. Because MT also acts as an antioxidant and daytime levels are higher in patients with ARMD, these results might be interpreted as a rescue factor.     

褪黑素对过氧化氢诱导晶状体上皮细胞氧化损伤的保护作用

目的：探讨褪黑素对过氧化氢诱导晶状体上皮细胞氧化损伤的保护作用。
　　方法：晶状体上皮细胞传代培养后,分别加入不同浓度褪黑素预处理12h后,加入100μmol/L H2 O2继续孵育24h, MTT比色法检测褪黑素对H2 O2诱导的晶状体上皮细胞活力的影响,流式细胞仪检测细胞凋亡率,比色法检测凋亡相关因子Caspase-3及Caspase-9的活性。
　　结果：MTT结果显示褪黑素对晶状体上皮细胞活性无影响,该药物可以抑制过氧化氢诱导的细胞活性的下降,流式细胞计数结果显示褪黑素可以抑制过氧化氢诱导的细胞凋亡,此外,褪黑素还可以减少过氧化氢所致晶状体上皮细胞内Caspase-3及Caspase-9的活性,并且,伴随褪黑素作用时间的延长其活性呈下降趋势。
　　结论：褪黑素可以明显抑制过氧化氢诱导的晶状体上皮细胞的凋亡,从而为寻求有效的防治白内障药物提供可靠的实验依据。     

Ocular and systemic melatonin and the influence of light exposure

Melatonin is a neurohormone known to modulate a wide range of circadian functions, including sleep. The synthesis and release of melatonin from the pineal gland is heavily influenced by light stimulation of the retina, particularly through the intrinsically photosensitive retinal ganglion cells. Melatonin is also synthesised within the eye, although to a much lesser extent than in the pineal gland. Melatonin acts directly on ocular structures to mediate a variety of diurnal rhythms and physiological processes within the eye. The interactions between melatonin, the eye, and visual function have been the subject of a considerable body of recent research. This review is intended to provide a broad introduction for eye‐care practitioners and researchers to the topic of melatonin and the eye. The first half of the review describes the anatomy and physiology of melatonin production: how visual inputs affect the pineal production of melatonin; how melatonin is involved in a variety of diurnal rhythms within the eye, including photoreceptor disc shedding, neuronal sensitivity, and intraocular pressure control; and melatonin production and physiological roles in retina, ciliary body, lens and cornea. The second half of the review describes clinical implications of light/melatonin interactions. These include light exposure and photoreceptor contributions in melatonin suppression, leading to consideration of how blue blockers, cataract, and light therapy might affect sleep and mood in patients. Additionally, the interactions between melatonin, sleep and refractive error development are discussed. A better understanding of environmental factors that affect melatonin and subsequent effects on physiological processes will allow clinicians to develop treatments and recommend modifiable behaviours to improve sleep, increase daytime alertness, and regulate ocular and systemic processes related to melatonin.     

The eyes of deep-sea fish I: Lens pigmentation, tapeta and visual pigments

Deep-sea fish, defined as those living below 200 m, inhabit a most unusual photic environment, being exposed to two sources of visible radiation; very dim downwelling sunlight and bioluminescence, both of which are, in most cases, maximal at wavelengths around 450-500 nm. This paper summarises the reflective properties of the ocular tapeta often found in these animals, the pigmentation of their lenses and the absorption characteristics of their visual pigments. Deep-sea tapeta usually appear blue to the human observer, reflecting mainly shortwave radiation. However, reflection in other parts of the spectrum is not uncommon and uneven tapetal distribution across the retina is widespread. Perhaps surprisingly, given the fact that they live in a photon limited environment, the lenses of some deep-sea teleosts are bright yellow, absorbing much of the shortwave part of the spectrum. Such lenses contain a variety of biochemically distinct pigments which most likely serve to enhance the visibility of bioluminescent signals. Of the 195 different visual pigments characterised by either detergent extract or microspectrophotometry in the retinae of deep-sea fishes, ca. 87% have peak absorbances within the range 468-494 nm. Modelling shows that this is most likely an adaptation for the detection of bioluminescence. Around 13% of deep-sea fish have retinae containing more than one visual pigment. Of these, we highlight three genera of stomiid dragonfishes, which uniquely produce far red bioluminescence from suborbital photophores. Using a combination of longwave-shifted visual pigments and in one species (Malacosteus niger) a chlorophyll-related photosensitizer, these fish have evolved extreme red sensitivity enabling them to see their own bioluminescence and giving them a private spectral waveband invisible to other inhabitants of the deep-ocean.     

Short wavelength light filtering by the natural human lens and IOLs – implications for entrainment of circadian rhythm

Purpose: Photoentrainment of circadian rhythm begins with the stimulation of melanopsin containing retinal ganglion cells that respond directly to blue light. With age, the human lens becomes a strong colour filter attenuating transmission of short wavelengths. The purpose of the study was to examine the effect the ageing human lens may have for the photoentrainment of circadian rhythm and to compare with intraocular implant lenses (IOLs) designed to block UV radiation, violet or blue light. Methods: The potential for photoentrainment of circadian rhythm was computed for 29 human donor lenses (18–76 years) and five IOLs (one UV, two violet and two blue light blocking) based on the transmission properties of the lenses and the spectral characteristics of melanopsin activation and two of it′s physiological outcomes; melanopsin‐driven pupillary light reponse and light‐induced melatonin suppression. Results: The potential for melanopsin stimulation and melatonin suppression was reduced by 0.6–0.7 percentage point per year of life because of yellowing of the natural lens. The computed effects were small for the IOLs and did not exceed that of a 22.2‐year‐old natural lens for the blue‐blocking IOLs. Conclusion: The results show that photoentrainment of circadian rhythm may be significantly impaired in older subjects because of the colour filtering characteristics of the human lens, whereas the effects were small for all three types of IOLs studied. Consequently, the ageing process of the natural lens is expected to influence the photoentrainment of circadian rhythm, whereas IOLs are not expected to be detrimental to circadian rhythm.     

The effect of lens aging and cataract surgery on circadian rhythm

Many organisms have evolved an approximately 24-hour circadian rhythm that allows them to achieve internal physiological homeostasis with external environment. Suprachiasmatic nucleus (SCN) is the central pacemaker of circadian rhythm, and its activity is entrained to the external light-dark cycle. The SCN controls circadian rhythm through regulating the synthesis of melatonin by pineal gland via a multisynaptic pathway. Light, especially short-wavelength blue light, is the most potent environmental time cue in circadian photoentrainment. Recently, the discovery of a novel type of retinal photoreceptors, intrinsically photosensitive retinal ganglion cells, sheds light on the mechanism of circadian photoentrainment and raises concerns about the effect of ocular diseases on circadian system. With age, light transmittance is significantly decreased due to the aging of crystalline lens, thus possibly resulting in progressive loss of circadian photoreception. In the current review, we summarize the circadian physiology, highlight the important role of light in circadian rhythm regulation, discuss about the correlation between age-related cataract and sleep disorders, and compare the effect of blue light- filtering intraocular lenses (IOLs) and ultraviolet only filtering IOLs on circadian rhythm.     

Influence of dietary melatonin on photoreceptor survival in the rat retina: an ocular toxicity study

Previous studies have shown that melatonin treatment increases the susceptibility of retinal photoreceptors to light-induced cell death. The purpose of this study was to evaluate under various conditions the potential toxicity of dietary melatonin on retinal photoreceptors. Male and female Fischer 344 (non-pigmented) and Long-Evans (pigmented) rats were treated with daily single doses of melatonin by gavage for a period of 14 days early in the light period or early in the dark period. In another group, rats were treated 3 times per week with melatonin early in the light period, and then exposed to high intensity illumination (1000-1500 lx; HII) for 2h, and then returned to the normal cyclic lighting regime. At the end of the treatment periods, morphometric measurements of outer nuclear layer thickness (ONL; the layer containing the photoreceptor cell nuclei) were made at specific loci throughout the retinas. In male and female non-pigmented Fischer rats, melatonin administration increased the degree of photoreceptor cell death when administered during the nighttime and during the day when followed by exposure to HII. There were some modest effects of melatonin on photoreceptor cell death when administered to Fischer rats during the day or night without exposure to HII. Melatonin treatment caused increases in the degree of photoreceptor cell death when administered in the night to male pigmented Long-Evans rats, but melatonin administration during the day, either with or without exposure to HII, had little if any effect on photoreceptor cell survival. In pigmented female Long-Evans rats, melatonin administration did not appear to have significant effects on photoreceptor cell death in any treatment group. The results of this study confirm and extend previous reports that melatonin increases the susceptibility of photoreceptors to light-induced cell death in non-pigmented rats. It further suggests that during the dark period, melatonin administration alone (i.e., no HII exposure) to pigmented male rats may have a toxic effect on retinal cells. These results suggest that dietary melatonin, in combination with a brief exposure to high intensity illumination, induces cellular disruption in a small number of photoreceptors. Chronic exposure to natural or artificial light and simultaneous intake of melatonin may potentially contribute to a significant loss of photoreceptor cells in the aging retina.     

儿童白内障人工晶状体度数的选择及术后视力矫正

目的:观察儿童白内障人工晶状体植入术后视力、屈光度,探讨儿童白内障选择合适人工晶状体的依据。方法:3￣11岁儿童52例83眼,手术时按年龄分为两组,A组3￣6岁,27例50眼;B组6￣14岁,25例33眼均植入人工晶状体,术后1mo进行视网膜检影验光,每0.5a复验,随访6mo￣3a,对术后屈光度及最终矫正视力进行观察。结果:A组平均屈光度变化为3.17±2.90D。B组平均屈光度变化为1.08±1.37D,11眼(13.3%)BCVA≥1.0,45眼(55.6%)BCVA≥0.5,5眼(6.0%)≤0.3。结论:儿童白内障尽早手术的同时,根据年龄段,植入欠矫的人工晶状体并配戴框架眼镜,是恢复儿童良好的视力的关键。     

人工晶状体囊袋内悬吊治疗晶状体半脱位的临床观察

目的：探讨白内障超声乳化联合人工晶状体(IOL)囊袋内悬吊固定治疗晶状体半脱位(SL)的疗效。

方法：回顾性分析2014-06/2017-12于我院就诊的SL(悬韧带断离范围≤270°)患者18例18眼,均行白内障超声乳化联合IOL单襻或双襻囊袋内悬吊固定术,其中2眼同时行25G微创玻璃体切除术。术后随访6～12mo,观察最佳矫正视力(BCVA)、眼压(IOP)、IOL位置、眼底情况等,记录术中和术后并发症情况。

结果：本组患者均顺利完成手术。术后3mo,BCVA(0.43±0.30)较术前(1.48±0.68)明显改善(t=7.30,P<0.01),IOP均恢复正常(≤21mmHg),IOL均处于正位,无偏心、移位。本组患者术中和术后均未出现严重眼部并发症。

结论：单襻或双襻囊袋内悬吊固定IOL是治疗SL的一种有效的手术方式,不仅可以保持IOL位于正常生理位置、恢复患者视功能,而且经济实用,避免囊袋张力环(CTR)相关的并发症发生。     

Spectral sensitivity of melatonin suppression in the zebrafish pineal gland

The pineal gland of the zebrafish (Danio rerio) is a clock-containing photoreceptive organ. Superfused pineal glands kept in darkness display rhythmic melatonin production that lasts for days, with high melatonin levels during the night and low levels during the day. Nocturnal light, however, evokes an acute suppression of melatonin synthesis in the photoreceptor cells. Towards characterizing zebrafish pineal photopigment that is involved in the acute melatonin suppression we have measured the spectral sensitivity of melatonin-suppression response in superfused pineal glands. The effect of 2 h light exposure of seven wavelengths (lambdaavg 408, 460, 512, 560, 608, 660 and 697+/-10-15 nm) at multiple irradiances (10(7)-10(14) photons/cm2/s) was determined, and an action spectrum was plotted. The resultant action spectrum provides evidence for the involvement of multiple photopigments in melatonin suppression. The most efficient melatonin-suppression response was achieved by exposure to light of around 512 nm; however, another peak of lower irradiance sensitivity was observed in the middle to long wavelengths. Opsins-specific RT-PCR analysis confirmed the expression of exo-rhodopsin and visual red-sensitive opsin in the pineal gland, while other zebrafish visual opsins as well as VA and VAL opsins were not detected. Dartnall monograms for exo-rhodopsin and visual red-sensitive opsin account for most but not all of the spectral sensitivity features. Therefore, additional pineal photopigments may contribute to the melatonin-suppression response in the pineal gland.     

褪黑素对体外培养的人视网膜色素上皮细胞增殖的影响

目的观察褪黑素对体外培养的人视网膜色素上皮细胞生长、增殖的影响,寻找药物以防治增殖性玻璃体视网膜病变。方法分别将不同浓度的褪黑素(0,125ng·L-1,250ng·L-1,500ng·L-1)加入体外培养的视网膜色素上皮细胞培养液,72h后用四甲基唑盐(MTT)比色法在自动酶标测定仪测540nm处的吸光值A,并计算出不同浓度条件下的细胞增殖抑制率。结果褪黑素在不同浓度下抑制视网膜色素上皮细胞增殖,并存在剂量-效应关系,实验组125ng·L-1和500ng·L-1组与对照组比较有显著性差异(P<0.001),但实验组250ng·L-1组与对照组之间的差异无显著性。结论褪黑素能抑制体外培养的人视网膜色素上皮细胞增殖,可作为防治增生性玻璃体视网膜疾病的侯选药物作进一步研究。     

Age and the lens — refraction and accommodation

The increasing radius of the lens surfaces and the development of cortex and nucleus due to the differences in refractive indices, explain the physiological changes in refraction and accommodation which occur during life.     

Sex, age and the birefringence of the human crystalline lens

Measurements were made of the birefringence of intact human crystalline lenses and of single lens fibres in the age range of 4 to 93 years. Birefringence changes were observed when the lenses were stressed. It was possible to obtain high correlations between the optical and mechanical properties of the lenses. Male and female lenses had significantly different properties, the latter pointing to a greater disposition to irreversible changes under minimal stress. Age produced systematic changes. Both stress and age parameters are analyzed.     

Pigmented Striae of the Anterior Lens Capsule and Age-Associated Pigment Dispersion of Variable Degree in a Group of Older African-Americans: An Age, Race, and Gender Matched Study

PURPOSE: To investigate pigmented striae of the anterior lens capsule in African-Americans, a potential indicator of significant anterior segment pigment dispersion. METHODS: A group of 40 African-American subjects who exhibited pigmented lens striae (PLS) were identified from a non-referred, primary eye care population in Chicago, IL, USA. These subjects were then compared to an age, race, and gender matched control group relative to refractive error and the presence or absence of diabetes and hypertension. RESULTS: The PLS subjects (mean age = 65.4 +/- 8.8 years, range = 50-87 years) consisted of 36 females and 4 males. PLS were bilateral in 36 (85%) of the 40 subjects. Among the eyes with PLS, 21 (55%) of 38 right eyes and 22 (61%) of 36 left eyes also had significant corneal endothelial pigment dusting, commonly in the shape of a Krukenberg's spindle. Ten (25%) of the PLS subjects had either glaucoma or ocular hypertension (7 bilateral, 3 unilateral). The presence of trabecular meshwork pigment varied from minimal to heavy. The mean +/- SD (range) refractive error of the PLS right eyes was +1.61 +/- 1.43D (-1.50 to +5.00D) and +1.77 +/- 1.37D (-1.00 to +5.00D) for the left eyes. Based on these data, the PLS right eyes were +1.63D (Student's t, p = 0.0001; 95% CI = +0.82 to +2.44D) more hyperopic on average than the control right eyes, and the PLS left eyes were +1.77D (p = 0.0001; 95% CI = +0.92 to +2.63D) more hyperopic on average than the control left eyes. Trend analysis showed a gradually increasing likelihood of PLS with increasing magnitude of hyperopia in both eyes (Mantel-Haenszel chi-square, p = 0.001). Among PLS subjects, 24 (60%) of 40 were hypertensive and 9 (23%) of 40 were diabetic. However, these proportions were not significantly different (two-tailed Fisher's exact test; hypertension: p = 0.30; diabetes: p = 0.70) from the randomly selected controls. CONCLUSIONS: Among our African-American group, which consisted predominately of females >50 years of age, the likelihood of PLS increased with increasing hyperopic refractive error. This finding is consistent with the possibility that PLS may, in some circumstances, indicate a significant pigment dispersal process due to iris-lens rubbing that may be associated with crowding of anterior segment structures. Additional study is warranted to further assess the nature of PLS, their precise relationship with an age-related pigment dispersal process, and their true significance as a risk factor for development of glaucoma.     

蓝光及蓝光滤过型人工晶状体对体外培养人视网膜色素上皮细胞的影响

目的探讨蓝光滤过型人工晶状体（intraocular lens，IOL）对含N-亚视黄基-N-视黄基乙醇胺（A2E）的人视网膜色素上皮（retinal pigment epithelium，RPE）细胞的细胞活力、氧化应激及分泌血管内皮生长因子（vascular endothe-lial growth factor，VEGF）、色素上皮衍生因子（pigment epithelium detived factor，PEDF）的影响。方法体外培养含A2E的RPE细胞，用低强度蓝光持续照射，在光通路上置蓝光滤过型（AcrySof Natural）或紫外线阻挡型（AcrySof）IOL。细胞分为：A组（AcrySof Natural IOL，光照）；B组（AcrySof IOL，光照）；C组（光照，无IOL）；D组（无光照，无IOL）。CCK-8检测细胞活力，流式细胞仪检测活性氧自由基（reactive oxygen species，ROS）水平，酶联免疫吸附法检测还原型谷胱甘肽（glutathione，GSH）、VEGF、PEDF含量。结果A、B、C和D组细胞活力分别为（76.9±3.9）％、（42.5±4.3）％、（35.2±4.1）％、（96.7±3.1）％；ROS分别为511.53±67.43、1011.15±174.88、1022.23±158.72、452.82±77.98：GSH分别为（15.34±4.77）μmol／L、（2.57±1.96μmol/L、（1.58±1.13）μmol/L、（19.73±5.49）μmol／L；VEGF／PEDF比值分别为1.40、9.76、14.86、0.71。同B、C组相比，A组细胞活力和GSH含量明显提高，ROS含量和VEGF／PEDF比值明显下降（P〈0.05）。结论蓝光滤过型IOL对A2E介导的RPE细胞蓝光损伤有保护作用，能够降低蓝光诱导的ROS和VEGF水平，优于紫外线阻挡型IOL。     

PUVA therapy and the lens reconsidered

On the basis of animal experiments there appears to be a theoretical chance that lens changes will occur in patients receiving PUVA treatment. In the published studies the incidence of lens changes in patients treated with PUVA is very low. In this study changes were observed both during PUVA treatment and during a long follow-up period. The absence of typical lens changes in patients aged 55 years and older is remarkable. A possible relationship between these findings and information obtained by experiment is discussed.     

Determining the power of a negative lens field expander

In 1984, Kozlowski, Mainster and Avila derived a formula for the power of the lens needed in the negative lens field expander. Their method is based on the principle of telescopic magnification. In this technical note, we use the principle of spectacle magnification and obtain the power of the same lens. Both methods are presented for comparison. Practitioners may choose either method in determining the power of the negative lens field expander for their low vision patients, but the spectacle magnification method has the advantages of simplicity and familiarity to ophthalmic practitioners.