There are different techniques or methods to record visual or retinal function changes in laboratory animals. Clinical visual electrophysiological testing is a non-invasive diagnostic method that can record animal visual function in vivo. It can be used as a tool to investigate the visual physiological phenomena. It is also taken as an objective indicator to monitor visual function changes， such as the effect of various factors （whether physical， chemical or biological） on visual functions， evaluation of therapeutic efficiency， diagnosis for disease or drug development. There are many factors that might affect visual electrophysiological testing results so experimental control studies are necessary. The investigation of the new methods， indicators and analysis methods are the focus of research in this field. Establishing a standard experimental methodology is crucial for the technique to become widespread with good quality control.

Objective  To study the effect of the duration of dark adaptation on electroretinography （ERG） in SD rats； to develop standardized research programs so results can easily be compared between different laboratories. Methods  In an experimental study， 42 SD rats （42 eyes） were randomly divided into 7 groups based on the duration of dark adaptation： 15 min， 30 min， 1 h， 4-6 h， 12-14 h， 15-17 h， and 24-26 h. Visual electrophysiology recordings were then taken. ANOVA was used to analyze the differences among the groups and a post hoc analysis was used to compare the difference between any two groups. Results  Different dark adaptation durations mainly affected the latencies of the dark-adapted ERG a-wave and b-wave of the rats′ ERG. The latency of 15 min dark adaption time was delayed longer compared with other dark adaption time group （P<0.05）. There was no significant effect when dark adaptation time was longer than 30 minutes. Conclusion  Dark adaptation durations impact ERG recordings. The minimum dark adaptation time for rat electroretinography recording is 30 minutes.

Objective To investigate the effect of circadian rhythm on the visual electrophysiology of the SD rat. Methods In this experimental study， 24 SD rats were divided into 4 groups randomly， 6 rats （6 eyes） in each group. Visual electrophysiology of the 4 groups was recorded at different time periods respetively with different stimulation parameters： 8：00-12：00 （morning）， 14：00-18：00 （afternoon）， 20：00-24：00 （midnight）， and 2：00-6：00 （before dawn）. ANOVA was used to analyze the differences among the groups and post hoc analysis was used to compare the difference between any two groups. Results The a-wave and b-wave amplitudes of dark-adapted electroretinogram （ERG） was higher in the afternoon and midnight than in the morning. The O2 amplitude of the oscillatory potentials was highest at midnight. The latency of the P1 wave of the 20 Hz flicker ERG reaction and the N1 wave of the visual evoked potential during the before draw was significantly shorter than that in the morning. Conclusion The cone and rod functions in SD rats are related to circadian rhythm， and it is more active at night than during the day. It is better to schedule visual electrophysiological recordings in SD rats during the same period of the day.

Objective To evaluate the longitudinal development of electroretinographic （ERG） sensitivity in normal SD rats. Methods In an experimental study， scotopic ERGs of 22 eyes of 22 rats were recorded postnatally （P） on P16， P18， P30±2 and P64±2 days. The stimulus light was white with gradient intensities. Rod sensitivity （S） and the saturated a wave （Rmp3） were obtained by fitting Hood′s function. Sensitivity of the b wave （σ） and maximum b wave （Vmax） were calculated by regression using the Naka-Rushton function. ANOVA was used to test the differences in ERG parameters at different postnatal ages. Results Both rod sensitivity （S） and b wave sensitivity （σ） increased with development. The highest Rmp3 was obtained at P18 while Vmax occurred at P30±2 days. Conclusion Alteration of rod sensitivity increased with postnatal development and reflected the developmental characteristics of rod function of SD rat.

Objective  To observe the characteristics of photopic ultraviolet-sensitive cone electroretinograms （UV-cone ERGs） in C57BL/6J mice. Methods  This was an experimental study. Ten adult wild-type C57BL/6J mice （10 eyes） were divided into 2 groups of 5 each. Photopic ERGs were elicited after 10 minutes of adaptation under a steady white background illumination of 30 cd·m^-2. Mice in the experimental group displayed UV-cone ERGs elicited by UV flashes （λ=363 nm） with stimulus intensities of 0.03 mW·s·m^-2， 0.30 mW·s·m^-2，1.00 mW·s·m^-2 and 3.00 mW·s·m^-2. Mice in the control group displayed white flash ERGs （stimulus intensities ranged from 0.02 to 10.00 cd·s·m^-2）. The maximum responses of the a- and b-wave amplitudes of the 2 groups were compared. An independent samples t test was used for statistical analysis. Results  As UV intensity increased to 0.30 mW·s·m^-2， the UV-cone ERG could be elicited with an amplitude of 14.8±3.0 μV. At an intensity of 1.00 mW·s·m^-2 or 3.00 mW·s·m^-2， oscillatory potentials （OPs） with a sizeable O_1-3 were recorded on the b-wave. But there were no obvious OPs in the control group. The maximum response showed that the b-wave amplitude of the experimental group was significantly higher than that of the control group （t=2.615， P＜0.05）， although there was no statistically significant difference in a-waves （t=-1.633， P＞0.05）. Conclusion  In adult C57BL/6J mice， the difference between photopic UV and white flash ERGs involve wave shape and maximum amplitude. Our results provide normal reference values for UV-cone ERGs in mice.

Objective To investigate the correlation between intraocular pressure （IOP） and central corneal thickness （CCT） and corneal spherical aberration as well as asphericity. Methods This was a cross-sectional study. Two hundred and sixteen eyes in 108 mild-to-moderate myopia patients were examined with the Pentacam HR anterior segment tomographer. The aspheric coefficient （Q value） and corneal spherical aberration results from the different quadrants in both the anterior and posterior corneas （including superior， inferior， nasal， temporal， horizontal and vertical directions） and the data 6， 7， 8 and 9 mm eccentric diameters were obtained. IOP and CCT were measured by a non-contact tonometer and A-scan ultrasonic corneal pachymeter， respectively. Patients were divided into 2 groups based on the degree of myopia. The relationship between the IOP with and without CCT and corneal spherical aberration as well as asphericity were analyzed. Data was processed using a Pearson correlation analysis， independent samples t test and one-way ANOVA. Results IOP was significantly correlated with anterior corneal asphericity （r=-0.30， P<0.05 for right eyes； r=-0.34， P<0.05 for left eyes）， but was not significantly correlated with anterior corneal spherical aberration in the mild myopia group. In the moderate myopia group， although IOP was significantly correlated with anterior corneal spherical aberration （r=0.31， P<0.05 for right eye； r=0.37， P<0.01 for left eye）， there was no significant correlation with anterior corneal Q value. CCT was only significantly correlated with the temporal corneal Q value （r=0.47， P<0.01 for right eyes； r=0.29， P<0.05 for left eyes）. Conclusion IOP induced a decrease in anterior corneal asphericity in mild myopes， however， it was positively correlated with anterior corneal spherical aberration. The reason for the difference may be related to the compensation mechanism of the cornea itself.

Objective  To study the relationship between the higher-order aberrations and low-， medium-， and high-contrast visual acuity in normal human eyes with excellent eyesight. Methods  A descriptive study was conducted and normal human eyes with excellent eyesight were selected for this test. With background brightness set at 260 lumens， visual acuities were measured at 4 contrast levels of 100%， 25%， 10% and 5%. At the same time， wavefront aberrations were measured with pupil diameters at 3.11 mm and 5.96 mm. The correlation between contrast visual acuity and wavefront aberration under different pupil sizes was evaluated， and fitted regression equations were determined by using linear regression analysis. Results  Visual acuity varied more significantly under low contrast levels than under high contrast. When pupil diameter was set at 3.11 mm， there was a linear correlation between the root mean square value （RMS） of higher-order aberrations and contrast visual acuity （mini coefficient of determination R2=0.1129）. Conclusion  Wavefront aberrations impact contrast visual acuity at all contrast levels.

Objective  To assess the accuracy， precision， repeatability， and reproducibility of biometric measurement of the mouse eye made by extended scan depth spectral domain optical coherence tomography （SD-OCT）. Methods  It was an experimental study. An SD-OCT with an extended depth range of 7.3 mm， A-scan speed of 28 kHz， axial resolution of 9.0 μm and transversally 19 μm was developed. Five 40-day-old C57BL/6 mice （10 eyes） were imaged with a custom built， extended scan depth SD-OCT in 2 sessions. Two scans were performed by operator 1 and a following scan by operator 2 at the first session， to determine repeatability and interoperator reproducibility. Intersession reproducibility was assessed by an additional scan performed by operator 1 2 days later. The data were compared to those from time-domain OCT （TD-OCT） by independent t test. All experiments were performed between 2：00 PM and 4：00 PM. The repeatability and reproducibility were evaluated by coefficient of repeatability/reproducibility， intraclass correlation coefficients （ICCs）， Wilcoxon matched-pairs test and Bland-Altman graph. Results  High-quality OCT images of the entire mouse eyes with high resolution were acquired. The ocular dimensions from TD-OCT measurements were close to these obtained by SD-OCT. The overall coefficients of repeatability/reproducibility for anterior chamber depth， lens thickness， vitreous chamber and axial length were all less than 3% and relevant intraclass correlation coefficients （ICCs） were nearly greater than 0.75， whereas these were less than 5% and ICCs were smaller for corneal thickness and retinal thickness. Wilcoxon analysis showed there was no statistically significant difference between any 2 groups for all parametres except corneal thickness of repeatability （Z=-2.310， P<0.05）. From the graph of differences against mean for the axial lengths， it can be seen that 100% of the values fall within 2 SDs of the mean. The overall coefficients of repeatability/reproducibility for curvatures were less than 5%. The ICCs for anterior curvature of the cornea and anterior/posterior curvatures of the lens were almost greater than 0.75， while it was greater than 0.45 for posterior curvature of the cornea. Graph of differences against means of average curvatures of reproducibility showed 5% data were without 2 SDs of the mean. Conclusion  SD-OCT is quite repeatable and reproducible for ocular dimension measurement of mouse eye. The novel method is helpful for monitoring the growth of the eye in normal mice and in strains that have developmental conditions such as myopia.

Objective To investigate the dynamic changes in the anatomy of the anterior segment with and without accommodation in primary and middle-school students. Methods This was a cross-sectional study. Ultrasound biomocroscopy （UBM） was used to test 54 primary students and 55 middle-school students in Fuzhou. Some parameters related to the ciliary body， iris， anterior chamber angle and other relevant data were measured with UBM. Data were analyzed using a paired t test and independent-samples t test. Results Results for the primary student group without accommodation were as follows： the ciliary process distance （CPD） was 160.53±17.78 μm， ciliary body thickness （CT） was 90.01±34.30 μm， iris-ciliary process distance （ICPD） was 23.11±3.33 μm， iris thickness （IT） 1 was 35.95±6.60 μm and IT2 was 52.81±9.94 μm， trabecular ciliary process distance （TCPD） was 151.27±23.11 μm， θ3 was 39.23°±7.46°， and θ4 was 56.02°±6.75°. The results with accommodation were as follows： 187.62±15.44 μm， 74.23±19.87 μm， 19.78±2.69 μm， 30.34±5.83 μm， 47.11±6.71 μm， 131.55±20.02 μm， 31.68°±5.14°， and 50.39°±4.89° （t=8.45， 2.93， 5.72， 4.68， 3.49， 4.74， 6.12， 4.96， P＜0.05）. The respective results for the middle-school student group without accommodation were as follows： 214.64±15.25 μm， 99.13±17.80 μm， 27.92±9.00 μm， 40.72±6.43 μm， 56.57±9.13 μm， 176.82±28.06 μm， 43.73°±6.93°， and 60.15°±10.48°. Results with accommodation were as follows： 271.38±11.96 μm， 93.27±10.42 μm， 21.66±7.54 μm， 35.68±4.37 μm， 50.17±6.49 μm， 136.41±19.35 μm， 39.51°±5.28°， and 53.68°±9.12° （t=20.91， 2.03， 3.81， 4.63， 4.08， 8.47， 3.46， 3.33， P＜0.05）. There was a significant difference between these 2 groups with accommodation（in the same sequence， t=30.95， 6.10， 4.47， 5.29， 2.37， 7.70， 2.32， and 6.98， P＜0.05）. Conclusion The most significant change occurs in the ciliary body with near accommodation： muscle fibers contract， especially in the circular muscles， and move forward and inward to induce the suspensory ligaments of the lens to loosen， thus achieving intense accommodation. The response is correlated with age： the younger the child， the more intense the response.

Objective To evaluate and determine the long-term effects of photorefractive keratectomy （PRK） on corneal endothelial cell density and morphology， and investigate their correlation with surgically designed parameters such as ablation depth and laser scan time. Methods In this retrospective study， 24 patients （44 eyes） who underwent PRK 10 years earlier and 45 normal eyes of 25 cases without any ophthalmologic surgery were enrolled in this study as the PRK group and the control group， respectively. Noncontact specular microscopy （Topcon， SP3000P， Japan） was used to measure central corneal endothelial cell density and morphology. A Pearson correlation was used to analyze the relationship between corneal endothelial cell density and morphology， and surgically designed parameters. The PRK group was divided into 3 subgroups based on the depth of tissue ablation： low ablation group （ablation depth <60 μm）， moderate ablation group （ablation depth： 60~90 μm） and high ablation group （ablation depth >90 μm）. The differences in corneal endothelial cell density and morphology between these 3 groups and the control group were analyzed. Data were analyzed using independent samples t test， Pearson correlation， ANOVA. Results The differences in average endothelial cell area， endothelial cell density， coefficient of variation of the endothelial cell area and percentage of hexagonal cells between the PRK group and control group were not statistically significant （t=-1.390， 1.323， 0.569， 0.788， P>0.05）. However， there were statistically significant correlations between average endothelial cell area and endothelial cell density and manifest refraction spherical equivalent （MRSE） （r=-0.424， 0.420， P＜0.01）. The 2 parameters were also significantly correlated with attempted ablation depth （r=0.391， -0.388， P＜0.01）. The differences in average endothelial cell area， endothelial cell density， coefficient of variation of the endothelial cell area and percentage of hexagonal cells between the low ablation group， moderate ablation group， high ablation group and control group were not statistically significant （F=2.195， 1.961， 0.817， 1.529， P>0.05）. Conclusion Compared to normal eyes， no significantly abnormal change in central corneal endothelial cell density or morphology was observed 10 years after PRK. MRSE and attempted ablation depth may have an effect on the average endothelial cell area and endothelial cell density.

Objective  To study the effect of altitude hypoxia and rapid decompression on the stability of the corneal flap after laser in situ keratomilersis （LASIK） in rabbits. Methods  In an experimental study， 36 eyes （18 Japanese white rabbits） were randomly divided into 3 groups 1 week after LASIK surgery： the control group， the altitude hypoxia group， and the rapid decompression group. The altitude hypoxia group ascended to 5500 m at the rate of 30-40 m/s remained there for 1-2 min， then returned to ground level at the rate of 200 m/s. The rapid decompression group ascended to 5500 m at the rate of 30-40 m/s， remained there for 1-2 min， then ascended rapidly to an altitude of 12 000 m in 0.13 s by adjusting a pressure-releasing device， remained at the high altitude of 3-5 s， finally returning to ground level at the rate of 200 m/s. The stability of the corneal flap was observed with an optical microscope and transmission electron microscope （TEM）. The stability of the corneal flap was analyzed by a x² test. Results  The images under the optical microscope and TEM showed that the interface tissue healing between the flap and stromal bed was clear with no separation， and was surrounded by regular collagen fibers in both the altitude hypoxia and rapid decompression groups. The differences between the two groups and the control group were insignificant （x²=0.22，P>0.05；x²=0.25， P>0.05）. Conclusion  Both altitude hypoxia and rapid decompression do not impact on the stability of corneal flaps after LASIK in rabbits.

Objective  To evaluate the corneal morphology and corneal mechanical sensitivity in patients under long-term prostaglandin analog treatment. Methods  A cross-sectional case-control study was performed in the Eye and ENT Hospital of Fudan University from August 2011 to April 2012. A total of 20 patients with bilateral primary open-angle glaucoma were enrolled， including 10 patients treated with prostaglandin eye drops for at least one year with an unchanged prescription during the final 6 months （group A）， and 10 untreated patients （group B）. Corneal sensitivity was assessed using the Cochet ＆ Bonnet esthesiometer. Corneal morphology was examined with an in vivo confocal microscope. A two-eye design model was used to evaluate the differences between the two groups. A Spearman correlation coefficient was used to analyze the relationship between corneal sensitivity and corneal subbasal cells. Results  The corneal basal epithelial cell density of group A was significantly higher than that of group B （7 009±638 cells/ mm² vs. 6 745±482 cells/ mm²； F=5.22， P<0.05）. Results were similar for the tortuosity of corneal subbasal nerves （1.71±0.46 vs. 1.42±0.43；F=7.29， P<0.05） and the grade for activated keratocytes （2.35±0.81 vs. 1.25±0.44； F=59.67， P<0.01）. In contrast， the branches of the corneal subbasal nerves （17.44±2.56 mm/ mm² vs. 19.54±5.02 mm/ mm²； F=8.22， P<0.05） and corneal sensitivity （54.25±6.74 mm vs. 59.50±1.54 mm； F=12.08， P<0.01） were significantly reduced in group A. The corneal endothelium did not present any morphological abnormalities. The reduced corneal sensitivity positively correlated with the density of the corneal subbasal nerves （r=0.379， P<0.05）. No correlations were found between corneal sensitivity and other factors such as tortuosity， reflectivity of subbasal nerves， the density of Langerhans cells or inflammatory cells. Conclusion  Significant morphological alterations in the cornea were found in glaucomatous patients with chronic prostaglandin analog treatment， except for endothelium cells. Corneal sensitivity was reduced， which correlated with a decreased density in corneal subbasal nerves.

Objective  To investigate early changes in anterior chamber parameters with the Allegro Oculyzer system after laser in situ keratomileusis （LASIK）. Methods  Thirty-nine patients （77 eyes） were recruited for this prospective self-control study. An Allegro Oculyzer anterial segment analysis system was used to measure the parameters of the anterior chamber （i.e. the anterior chamber volume， the anterior chamber angle of the four quadrants， and the central and peripheral anterior chamber depths） before and after LASIK. The Wilcoxon signed rank test was used for data analysis. Results  Before surgery， the posterior corneal tangential curvature， the anterior chamber volume， the anterior chamber angle（average/superior/inferior/nasal/temporal）， and the central and peripheral anterior chamber depths （superior/inferior/nasal/temporal） were： 6.19±0.23 D， 207±30.2 mm3， 40.4°±4.53°， 33.8°±8.57°， 33.9°±4.72°， 42.9°±5.00°， 42.9°±4.68°， 3.23±0.23 mm， 1.51±0.20 mm， 1.43±0.24 mm， 0.98±0.20 mm， and 1.03±0.21 mm， respectively. Seven days after the surgery， the parameters had changed to： 6.19±0.22 D，197±31.1 mm3， 40.6°±4.91°， 34.8°±8.15°， 33.9°±4.72°， 41.3°±5.32°， 43.5°±4.25°， 3.13±0.24 mm， 1.45±0.22 mm， 1.36±0.28 mm， 0.93±0.20 mm， and 0.96±0.21 mm， respectively. The differences between the anterior chamber volume and the central and peripheral anterior chamber depths were statistically significant （Z=-5.466， -7.352， -2.614， -2.546， -2.203， -3.327， P<0.05）. Conclusion  The anterior chamber volume and the central and peripheral anterior chamber depths decreased soon after LASIK was performed with the Allegro Oculyzer system. The change in the central anterior chamber depth was greater than that of the peripheral anterior chamber depth.

Objective  To investigate the associated factors leading to myopia in primary school students in a relatively developed region in Hangzhou. Methods  This was a cross-sectional study. By cluster sampling， primary students from 5 schools （grades 1-6） in Zhaohui District， Hangzhou， were recruited for this investigation. The right eye was examined and data were collected on spherical refraction， cylinder refraction， axial length and corneal curvature. Information was also obtained on family history， time spent on near reading after school and on weekends， and time spent on outdoor activities both after school and on weekends. A one-way ANOVA was used for analysis. Results  There were significant differences in gender， family history， time spent on near reading and outdoor activity between myopic and non-myopic groups. Females were more likely to be myopic than males （63.7% vs. 67.4%）. The students with myopic parents （F=10.559， P＜0.05） or those who spent more time on near reading on weekends （F=7.555， P＜0.05） and after school （F=2.492， P＜0.05） were more likely to be myopic. On the other hand， outdoor activities both after school （F=11.351， P＜0.05） and during weekends （F=6.387， P＜0.05） reduced the prevalence of myopia. Conclusion  Myopia in primary school students is associated with gender， family history， near reading and outdoor activity. So both genetic and environmental factors contribute to the development of myopia. The effect of environmental factors， especially near reading， is time-dependent， and ultraviolet exposure during outdoor activity plays a significant role.

Objective  To investigate the clinical effect on the correction of astigmatism with a posterior chamber phakic toric implantable collamer lens （TICL）. Methods  This was a prospective case study. Sixty-one patients （113 eyes） with moderate to high myopia who had undergone TICL implantation were evaluated before surgery and at 1， 3， and 6 months and 1 and 2 years after surgery to assess the safety， efficacy， predictability， stability and adverse events of the surgery. A repeated measures ANOVA test and SNK-q test were used to compare data at different time points， including best corrected visual acuity （BCVA）， uncorrected visual acuity （UCVA）， intraocular pressure （IOP） and the density of corneal endothelial cells. Results  Preoperative mean BCVA was 4.98±0.12， postoperative mean BCVAs were 5.04±0.08， 5.02±0.09， 5.05±0.10， 5.04±0.09 and 5.03±0.11， respectively， at 1， 3， and 6 months and 1 and 2 years after surgery. There were no significant differences for the BCVAs at the different time points （F=2.090， P>0.05）. Preoperative mean UCVA was 4.03±0.07， postoperative UCVAs were 4.92±0.10， 4.96±0.09， 4.95±0.12， 4.94±0.11， and 4.94±0.08 at different time points. All BCVAs were significantly different compared to BCVA before surgery （F=6.508，P<0.05）. Refractive status remained stable after surgery and astigmatism fell below 0.5 D. The TICL remained stable： 106 eyes （93.8%） had rotation less than 5° and 7 eyes （6.2%） had rotation of 5°~10° when measured at 6 months after surgery. There were no serious complications during or after surgery. Conclusion  Implantation of a TICL is safe and effective and provides predictable and stable refractive results in the treatment of astigmatism.

Oscillatory potentials （OPs） are a group of regular， high frequency wavelets superimposed on the ascending limb of the electroretinogram （ERG） b-wave. The ERG standard recommended by the International Society for Clinical Electrophysiology of Vision （ISCEV） suggests oscillatory potentials are one of the five routine examinations because OPs are sensitive functional indicators of the inner retina. Extraction of pure OPs depends largely on using filters correctly. However， many OPs studies fail to remove the low frequency components of the ERG simply because of inappropriate filter settings. In addition， the traditional method of OPs measurement summarizes the amplitude of each single wavelet. The reliability and repeatability of the method are significantly compromised by the low frequency contaminants. To extract pure OPs， it is essential to set the filter parameters appropriately. Calculating the area below the single-sided frequency spectrum curve by integration provides an accurate assessment of the total power of OPs.