近视眼LASIK术后眼高阶像差变化

探讨近视眼LASIK术后眼波阵面像差高阶像差各项的变化。方法:采用NIDEK OPD-Scan ARK-1000型波前像差扫描系统对LASIK治疗近视的62只眼在术前术后眼的波前像差进行了评估。在术前、术后10天、术后一个月分别测量眼的波阵面像差。比较6mm瞳孔下高阶像差各项的变化。结果:在全部接受检查的病例中,总的高阶像差(RMSh)均有所增加。从Zernik各项绝对值来看,球差C12变化最大。术后10天比术前增加6．7742倍(P=0．0001)。其次是彗差C7 C8(X轴、Y轴上的彗差),分别增加了4．883倍(P=0．0001)、3．7523倍(P=0．0001)。结论:LASIK术后眼的总的高阶像差均方根值(RMSh)明显增加,尤其是球差和彗差;但在恢复过程中高阶像差有下降的趋势。用像差仪来指导和评估LASIK等屈光手术可以更全面、更准确。     

Optical quality of the ocular lens of the sea lamprey (<Emphasis Type="Italic">Petromyzon marinus</Emphasis>) during the mature and transformer periods of life

While larval sea lampreys exist as eyeless filter feeders for several years, they transform into free-swimming juveniles (transformers) that attach parasitically to prey fish as they develop sexual maturity. This study examines lamprey lens development and optics and, since the lens is often the only refractive component of an aquatic eye, the data also provide an indication of visual ability during transformer and adult periods of life. Seven adult sea lampreys (0.40–0.55 m) and eight transformers (0.15–0.18 m) were sacrificed, the eyes removed and lenses dissected, measured, and placed in an automated laser scanning instrument. Back vertex focal length (spherical aberration) was measured for 14 beam positions across each lens by using a digital camera to record the position of the refracted beam. Transformer lenses exhibit positive spherical aberration, with average focal lengths varying from about 2.40 mm near the lens center and 1.06 mm at the lens periphery. On the other hand, the lenses from adults are largely corrected for spherical aberration, with average focal lengths varying from 2.19 mm to 2.44 mm. This result indicates that the younger lenses do not have a gradient refractive index necessary to mitigate the aberration and that further study of this model may reveal the relation between lens embryology and the development of such a gradient.     

Short-Term Stability in Refractive Status Despite Large Fluctuations in Glucose Levels in Diabetes Mellitus Type 1 and 2

Purpose

This work investigates how short-term changes in blood glucose concentration affect the refractive components of the diabetic eye in patients with long-term Type 1 and Type 2 diabetes.

Methods

Blood glucose concentration, refractive error components (mean spherical equivalent MSE, J0, J45), central corneal thickness (CCT), anterior chamber depth (ACD), crystalline lens thickness (LT), axial length (AL) and ocular aberrations were monitored at two-hourly intervals over a 12-hour period in: 20 T1DM patients (mean age ± SD) 38±14 years, baseline HbA1c 8.6±1.9%; 21 T2DM patients (mean age ± SD) 56±11 years, HbA1c 7.5±1.8%; and in 20 control subjects (mean age ± SD) 49±23 years, HbA1c 5.5±0.5%. The refractive and biometric results were compared with the corresponding changes in blood glucose concentration.

Results

Blood glucose concentration at different times was found to vary significantly within (p<0.0005) and between groups (p<0.0005). However, the refractive error components and ocular aberrations were not found to alter significantly over the day in either the diabetic patients or the control subjects (p>0.05). Minor changes of marginal statistical or optical significance were observed in some biometric parameters. Similarly there were some marginally significant differences between the baseline biometric parameters of well-controlled and poorly-controlled diabetic subjects.

Conclusion

This work suggests that normal, short-term fluctuations (of up to about 6 mM/l on a timescale of a few hours) in the blood glucose levels of diabetics are not usually associated with acute changes in refractive error or ocular wavefront aberrations. It is therefore possible that factors other than refractive error fluctuations are sometimes responsible for the transient visual problems often reported by diabetic patients.     

Spherical aberration of the fish lens: interspecies variation and age

Summary Spherical aberration of the eyes of a spectrum of freshwater fishes was determined by photographing the refractive effects of excised crystalline lenses on multiple parallel split laser beams. In general, spherical aberration is minimized by the developmentally related variation in lens refractive index. However, spherical aberration is marked and non-monotonic in a non-visual species such as the bullhead. Furthermore, the size and variability of the aberration appears to be related to visual need as indicated by diet and feeding habits. For example, the lenses of predatory sight feeders such as the pike (Esox lucius) or rock bass (Ambloplites rupestris) are optically superior to that of an omnivorous feeder as the carp (Cyprinus carpio).The effect of age was tested by examining rock bass lenses from fish two to seven years of age. Lens quality, as indicated by the amount of change in posterior focal length for beams of varying eccentricity from the optic axis, is optimum in lenses from five year old fish. The significance of this variation in lens quality is uncertain and requires further study with greater attention to specimens of advanced age.     

Optical properties of a cephalopod eye (the short finned squid,Illex illecebrosus)

Summary The extent to which the cephalopod eye is optically similar to the teleost eye was determined by measuring refractive error, accommodative ability, spherical and chromatic aberrations, and refractive indices and radii of curvature of the ocular media. The squid eye is well corrected optically underwater although a tendency toward hyperopia exists. This may be due to the existence of chromatic aberration and the fact that an aquatic environment is somewhat limited to the blue end of the spectrum. Accommodation takes place by movement of the lens toward the retina in a manner similar to the teleost eye. However, the squid lens is not spherical but slightly flattened. The lens is overcorrected as far as spherical aberration is concerned. Thus peripheral light rays focus further from the lens than paraxial ones. The function of this unusual example of lens development is unknown.     

Relation between phylogenetic position, lipid metabolism and butyrate production by different Butyrivibrio-like bacteria from the rumen

The Butyrivibrio group comprises Butyrivibrio fibrisolvens and related Gram-positive bacteria isolated mainly from the rumen of cattle and sheep. The aim of this study was to investigate phenotypic characteristics that discriminate between different phylotypes. The phylogenetic position, derived from 16S rDNA sequence data, of 45 isolates from different species and different countries was compared with their fermentation products, mechanism of butyrate formation, lipid metabolism and sensitivity to growth inhibition by linoleic acid (LA). Three clear sub-groups were evident, both phylogenetically and metabolically. Group VA1 typified most Butyrivibrio and Pseudobutyrivibrio isolates, while Groups VA2 and SA comprised Butyrivibrio hungatei and Clostridium proteoclasticum, respectively. All produced butyrate but strains of group VA1 had a butyrate kinase activity <40 U (mg protein)⁻¹, while strains in groups VA2 and SA all exhibited activities >600 U (mg protein)⁻¹. The butyrate kinase gene was present in all VA2 and SA bacteria tested but not in strains of group VA1, all of which were positive for the butyryl-CoA CoA-transferase gene. None of the bacteria tested possessed both genes. Lipase activity, measured by tributyrin hydrolysis, was high in group VA2 and SA strains and low in Group VA1 strains. Only the SA group formed stearic acid from LA. Linoleate isomerase activity, on the other hand, did not correspond with phylogenetic position. Group VA1 bacteria all grew in the presence of 200 μg LA ml⁻¹, while members of Groups VA2 and SA were inhibited by lower concentrations, some as low as 5 μg ml⁻¹. This information provides strong links between phenotypic and phylogenetic properties of this group of clostridial cluster XIVa Gram-positive bacteria.     

Adhesion molecules (ICAM-1 and VCAM-1) and diabetic retinopathy in type 2 diabetes

The expression of intercellular adhesion molecule (ICAM-1) and vascular cell adhesion molecule (VCAM-1) were studied in the conjunctiva of diabetic patients with and without retinopathy. All patients underwent a complete ophthalmic examination including ocular fundus and retinal fluorescein angiography. The indirect immunoperoxidase method was performed on 15 normal conjunctivas taken during cataract surgery (group 1), on 40 eyes of 40 patients with type 2 diabetes without diabetic retinopathy (DR) (group 2) and 13 eyes of 13 patients with DR (group 3). ICAM-1 and VCAM-1 are located in epithelial cells, vascular endothelial cells and in stromal cells. Our results show a statistically significant increase in the immunohistochemical expression of these proteins in the conjunctiva of diabetic patients with and without DR in comparison with normal conjunctiva (P = 0.001). Noteworthy, ICAM-1 and VCAM-1 are upregulated in the conjunctiva of diabetic patients with and without retinopathy, reflecting the inflammatory nature of this condition and suggesting a possible role for these mediators in the pathogenesis of diabetic microangiopathy.     

Aberrations of chick eyes during normal growth and lens induction of myopia

Understanding the control of eye growth may lead to the prevention of nearsightedness (myopia). Chicks develop refractive errors in response to defocusing lenses by changing the rate of eye elongation. Changes in optical image quality and the optical signal in lens compensation are not understood. Monochromatic ocular aberrations were measured in 16 chicks that unilaterally developed myopia in response to unilateral goggles with −15D lenses and in 6 chicks developing naturally. There is no significant difference in higher-order root mean square aberrations (RMSA) between control eyes of the goggled birds and eyes of naturally developing chicks. Higher-order RMSA for a constant pupil size exponentially decreases in the chick eye with age more slowly than defocus. In the presence of a defocusing lens, the exponential decrease begins after day 2. In goggled eyes, asymmetric aberrations initially increase significantly, followed by an exponential decrease. Higher-order RMSA is significantly higher in goggled eyes than in controls. Equivalent blur, a new measure of image quality that accounts for increasing pupil size with age, exponentially decreases with age. In goggled eyes, this decrease also occurs after day 2. The fine optical structure, reflected in higher-order aberrations, may be important in understanding normal development and the development of myopia.     

Chromosomal aberration assessment of silver rasbora fish (Rasbora tornieri) living near gold mine area with heavy metal contamination

This study aimed to investigate arsenic (As), cadmium (Cd), chromium (Cr), and lead (Pb), contamination in water, sediment, and Rasbora tornieri samples and chromosomal aberration in R. tornieri near gold mine area compared to unaffected area. The heavy metal concentrations in the samples were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-OES). The difference of As, Cr, and Pb concentrations in R. tornieri samples between the gold mine and unaffected areas was statistically significant (p < 0.05), but the difference was not significant for Cd. The diploid chromosome number of R. tornieri from both areas was 2n = 50, and the chromosomal aberrations of R. tornieri were higher in the gold mine area than those in the unaffected area. There are six types of chromosomal aberrations, including centric fragmentation (CF), centric gap, single chromatid gap, fragmentation, deletion, and polyploidy. The most common chromosomal aberration in the samples from the gold mine area was CF, and the difference in chromosomal aberration and the cells with chromosomal aberrations in R. tornieri between the areas was statistically significant (p < 0.05). The percentages of chromosomal aberrations in the R. tornieri samples from the gold mine and the unaffected areas were 16.60 and 1.66, respectively.     

Ocular dimensions and cone photoreceptor topography in adult Nile Tilapia <Emphasis Type="Italic">Oreochromis niloticus</Emphasis>

Information on the anatomy of the eye and the topography of cone photoreceptor cells in the retina is presented for the Nile Tilapia (Oreochromis niloticus). In adults, the shape and proportions of the ocular components of the prominent eye conform to the general form of fish eyes, as determined using cryo-sectioned eyes. The lens is approximately spherical and there is little variation in the distance from the centre of the lens to the border between the choroid and retina at a range of angles about the optical axis. The average ratio of the distance from the centre of the lens to the retina: lens radius (Matthiessen’s ratio) is 2.44:1. In retinal wholemounts, single and double (twin) cone photoreceptors, forming a square mosaic, are present. Peak photoreceptor densities for both morphological cone types are found in the temporal retina. Using peak cone densities and estimates of focal length from cryo-sectioned eyes, visual acuity is calculated to be 5.44 cycles per deg. The lack of apparent specific ocular or retinal specializations and the relatively low visual acuity reflect the lifestyle of the Nile Tilapia and may allow it to adapt to changes in visual environment in its highly variable natural habitat as well as contributing to the ‘ecological flexibility’ of this species.     

Benefit of Bi-Ocular Visual Stimulation for Postural Control in Children with Strabismus

Vision is important for postural control as is shown by the Romberg quotient (RQ): with eyes closed, postural instability increases relative to eyes open (RQ = 2). Yet while fixating at far distance, postural stability is similar with eyes open and eyes closed (RQ = 1). Postural stability can be better with both eyes viewing than one eye, but such effect is not consistent among healthy subjects. The first goal of the study is to test the RQ as a function of distance for children with convergent versus divergent strabismus. The second goal is to test whether vision from two eyes relative to vision from one eye provides better postural stability. Thirteen children with divergent strabismus and eleven with convergent strabismus participated in this study. Posturtography was done with the Techno concept device. Experiment 1, four conditions: fixation at 40 cm and at 200 cm both with eyes open and eyes covered (evaluation of RQ). Experiment 2, six conditions: fixation at 40 cm and at 200 cm, with both eyes viewing or under monocular vision (dominant and non-dominant eye). For convergent strabismus, the groups mean value of RQ was 1.3 at near and 0.94 at far distance; for divergent, it was 1.06 at near and 1.68 at far. For all children, the surface of body sway was significantly smaller under both eyes viewing than monocular viewing (either eye). Increased RQ value at near for convergent and at far for divergent strabismus is attributed to the influence of the default strabismus angle and to better use of ocular motor signals. Vision with the two eyes improves postural control for both viewing distances and for both types of strabismus. Such benefit can be due to complementary mechanisms: larger visual field, better quality of fixation and vergence angle due to the use of visual inputs from both eyes.     

Functional Visual Acuity of Early Presbyopia

Purpose

To evaluate visual function in patients with early presbyopia using the functional visual acuity (FVA) test.

Methods

This study included 27 eyes of 27 healthy older volunteers (mean age, 44.1 ± 2.6 years) and 14 eyes of 14 healthy young volunteers (mean age, 28.4±4.8 years). The distance-corrected visual acuity (DCVA), distance-corrected near VA (DCNVA), subjective amplitude of accommodation (AA), and distance and near pupillary diameters were measured. The distance FVA and distance-corrected near FVA (DCNFVA) were measured using the FVA Measurement System. The standard Schirmer test and standard tear break-up time measurement also were performed.

Results

The logarithm of the minimum angle of resolution (logMAR) DCVA was better than 0 in all subjects. The percentages of subjects with logMAR DCNVA below 0 was significantly lower in the presbyopia group than in the young group. The DCNFVA in the presbyopia group was significantly (P < 0.001) poorer than the DCNVA in that group. Significant linear negative correlations were seen between the DCNVA and AA (r = -0.507, P < 0.001) and the DCNFVA and AA (r = -0.681, P < 0.001) in the older subjects. Stepwise regression analysis showed that only the AA was a significant factor predictive of the DCNFVA in the presbyopia group. Tear function parameters were not adopted in the regression model.

Conclusions

Measurement of the DCNFVA can detect decreased AA in early presbyopia better than measurement of the conventional near VA. The DCNFVA is a good index for early presbyopia.     

Night myopia studied with an adaptive optics visual analyzer

Purpose

Eyes with distant objects in focus in daylight are thought to become myopic in dim light. This phenomenon, often called “night myopia” has been studied extensively for several decades. However, despite its general acceptance, its magnitude and causes are still controversial. A series of experiments were performed to understand night myopia in greater detail.

Methods

We used an adaptive optics instrument operating in invisible infrared light to elucidate the actual magnitude of night myopia and its main causes. The experimental setup allowed the manipulation of the eye''s aberrations (and particularly spherical aberration) as well as the use of monochromatic and polychromatic stimuli. Eight subjects with normal vision monocularly determined their best focus position subjectively for a Maltese cross stimulus at different levels of luminance, from the baseline condition of 20 cd/m² to the lowest luminance of 22×10⁻⁶ cd/m². While subjects performed the focusing tasks, their eye''s defocus and aberrations were continuously measured with the 1050-nm Hartmann-Shack sensor incorporated in the adaptive optics instrument. The experiment was repeated for a variety of controlled conditions incorporating specific aberrations of the eye and chromatic content of the stimuli.

Results

We found large inter-subject variability and an average of −0.8 D myopic shift for low light conditions. The main cause responsible for night myopia was the accommodation shift occurring at low light levels. Other factors, traditionally suggested to explain night myopia, such as chromatic and spherical aberrations, have a much smaller effect in this mechanism.

Conclusions

An adaptive optics visual analyzer was applied to study the phenomenon of night myopia. We found that the defocus shift occurring in dim light is mainly due to accommodation errors.     

The Chernobyl fallout in Salzburg/Austria and its effect on blood chromosomes

The radioactive fallout of the Chernobyl accident caused an increase in radiation dose of 20 to 110 per cent over the normal environmental burden to the inhabitans of Salzburg City in Austria (in a distance of about 1300 km from the accident). The structural chromosome aberration in the lymphocytes of the peripheral blood of 15 test-persons have been investigated one year after the accident. From two of these we know also the aberration frequencies before the accident which were significantly lower. The results from all test persons were pooled according to their Cs137 and Cs134 content, measured by whole body counter. Their mean additional blood doses from the incorporated caesium plus the external fallout radiation were 0.23, 0.36 and 0.55 mGy/yr. The aberration frequencies increased with dose. The slope of the best straight-line through the points was 2.0 +/- 0.7 total chromosome type aberrations in 100 metaphases per mGy/yr. This result fits in well with former investigations of persons with individually calculated radiation burden from the environment. The sharp increase with dose at this low level is not compatible with values extrapolated from high doses. The usual dose assessment based on chromosome aberrations extrapolated from high to low doses is therefore not possible in the range considered in this investigation.     

Anti-VEGF in treatment of diabetic macular edema

Diabetic macular edema is the leading cause of moderate visual deterioration in patients with diabetic retinopathy. Ranibizumab) blocks vascular endothelial growth factor (VEGF) induced hyperpermeability of blood vessels. In this prospective case series we investigated the efficacy and safety of anti-VEGF treatment in reduction of central retinal thickness (CRT) and improvement in visual acuity (VA) in patients with diabetic macular edema (DME). 9 patients were followed up for 6 months and treated monthly with intravitreal ranibizumab. VA and CRT were measured at each visit. Treatment was discontinued as the peak improvement of either parameter was reached and reinstituted in case of deterioration/recurrence of edema. Study endpoints included: VA using ETDRS chart, CRT and number of injections at 6 months. Mean VA from all 9 patients increased by 0.3 lines of logMAR (p < 0.05 compared to baseline), and CRT decreased from 515 +/- 123 microm to 310 +/- 110 microm. The improvement of VA after ranibizumab injection was in correlation with a decrease in CRT. Mean of 4 injections were needed to control the disease during the follow-up period. Ranibizumab treatment was effective in VA and reducing CRT. Several injections were needed to control the disease. Regular OCT examinations and retreatment are advised in order to maintain initially reached VA.     

人眼波前像差表示、测量及矫正研究

目的:波前像差引导的准分子激光角膜消融是屈光手术的新方法,研究人眼波前像差的测量原理、方法、表示、人眼波前像差准分子激光矫正的原理,以此理论用于准分子激光人眼像差矫正系统。方法:采用理论研究、计算机模拟、实验室实验等手段。分析人眼像差的概念和产生的原因,用数学的Zern ike多项式来表示像差,理论上定量分析Zern ike多项式表示的波前像差与角膜切削深度的关系,研究准分子激光切削角膜的机理,研究准分子激光进行矫正人眼像差的原理框图。结果:通过计算机模拟和实验室实验,用准分子激光矫正低阶和高阶像差是可行的。结论:用波前像差来引导屈光手术,使人眼的视力能够达到20/10上,并能避免当前PRK、LASIK屈光手术前后像差增大而引起的对视觉质量的影响。     

Thrombospondin-1, a natural inhibitor of angiogenesis, is present in vitreous and aqueous humor and is modulated by hyperglycemia

Negative regulators of angiogenesis play a major role in maintaining vascular homeostasis. Thrombospondin-1 (TSP1) is a natural inhibitor of angiogenesis. This report examines the presence of TSP1 in ocular samples and determines whether its production is altered in diabetes. Western blot analysis detected a 140 kDa antiangiogenic fragment of TSP1(gp140) in vitreous samples prepared from normal human and rat eyes. Intact TSP1 was detected in aqueous humor samples prepared from normal rat and bovine eyes. In contrast, TSP1 was virtually absent in vitreous and aqueous humor samples prepared from diabetic rat eyes. Furthermore, production of TSP1 by microvascular endothelial cells in culture was sensitive to high concentrations of glucose. Retinal blood vessels appeared nonuniform and dilated in diabetic animals when compared to control animals. These results demonstrate that TSP1 and its antiangiogenic fragment are present in aqueous humor and vitreous of normal rat eyes and are dramatically reduced in diabetes. Thus, TSP1 may play a role in ocular vascular homeostasis and its absence may contribute to vascular dysfunctions associated with diabetes.     

Normal Monocular and Binocular Visual Acuity in Seven-Year-Old Children

The purpose of this study was to obtain age-specific normative data for visual acuity (VA) in sevenyear- old children. The sample included a total of 127 healthy children (mean age 7.53 ± 0.025 years) without ophthalmic disorders. Monocular and binocular VAs were determined to the threshold level at two distances, 5 m and 0.5 m, using eye charts with eight intermediate levels between 1.0 and 2.4 (in the decimal notation system) with widely spaced tumbling Snellen’s E optotypes randomly distributed in four orientations. Since the optotypes were located in lines at intervals that were twice as large as the size of the optotype itself, they could be considered as single stimuli. The normal monocular and binocular VAs were 1.279 ± 0.025 and 1.491 ± 0.028 at 5 m and 1.256 ± 0.024 and 1.388 ± 0.025 m at 0.5 m, respectively (mean ± standard error of mean). Interocular differences in VA are also discussed. Our findings show that the normal VA in seven-yearold children is higher than the clinically accepted norm of 1.0; therefore, VA measurement to the threshold level is necessary for earlier visual disorders to be detected.     

Observations on the effect of X-ray alone and in combination with ultrasound on human chromosomes

Summary Human peripheral blood was treated with ultrasound either before or after irradiation, and chromosome aberrations in lymphocytes of peripheral blood cultures compared to those resulting from an equivalent dose of irradiation given alone.When peripheral blood is sonicated at a high intensity (3 W/cm²) for 10 min after irradiation, there is an increase in aberration frequency as compared to control samples receiving the equivalent radiation dose alone. However, should the blood be sonicated at the same frequency and for the same time period before radiation there is no significant increase in total chromosome aberrations over the irradiated controls. On the contrary a significant decreases occurs in certain classes of aberration.When sonification with a lower intensity (20 mW/cm²) was used in combination with irradiation the reverse effect was noted. Ultrasound administered for 10 min after radiation caused no significant increase in aberrations. On the contrary increasing the period of sonification to one hour resulted in a lowering of all types of aberration, significant in the case of dicentrics and total chromosome aberrations, when compared to irradiation alone. Reversing the order of treatment again resulted in the opposite effect to that achieved with comparable experiments at high intensities of sonification. Ultrasound before radiation did not produce lower breakage rates. Instead, when the period of sonification was increased to one hour, the number of aberrant cells, fragments, and total aberrations rose significantly over controls.It is suggested that sonification produces chemical changes affecting cellular repair systems, which when combined with ionising radiation, results in an increased or decreased repair effect depending on the dose, duration, and order of treatment.Dedicated to Prof. Dr. Felix Mainx on the occasion of his 80th birthday     

A detailed paraxial schematic eye for the White Leghorn chick

We studied the normal ocular development of the chick (Gallus gallus domesticus, White Leghorn) up to 15 days of age using both longitudinal and cross-sectional methods. The change in refractive error, corneal curvature and axial ocular distances were used to construct schematic eyes. Equations are presented which allow prediction of refractive error changes associated with changes in vitreous chamber depth. The mean refractive error was +3.2 D at hatching, which reduced by 66% over the first 3 days and stabilized by 11 days of age. The lens thickened and the anterior chamber deepened from hatching, but vitreal elongation and corneal flattening were delayed until after the first 3 days, suggesting that normal eye growth may be initially inhibited or inactive during an initial emmetropization period, and subsequently activated in response to myopic defocus arising from the continually expanding lens. Finally, when compared with published data on other chick strains, we find differences in the degree of hyperopia at hatching due to differences in lens thickness. However, the rate of ocular and vitreal expansion and the developmental changes in corneal power are similar, making the schematic eyes presented here generally applicable to different strains of chickens.