透明角膜切口白内障术后角膜曲率的临床观察*

目的:观察年龄相关性白内障行透明角膜切口超声乳化吸除及人工晶体植入术后角膜曲率的变化及相对稳定的时间。方法:收集2016年6月-8月在哈尔滨医科大学附属第一医院伍连德纪念医院进行的3.0 mm透明角膜切口白内障超声乳化吸除及人工晶体植入术的患者200例216眼,其中男88例、女128例,平均年龄71.2岁,进行相应的术前检查,并检查术前、术后第一天、一周、一个月、和三个月时的角膜曲率、视力、眼压并行相应的统计学分析。结果:术后不同时间点视力0.5的恢复情况:第一天为147眼(68.05%)、一周为175眼(81.02%)、一个月为193眼(89.35%)、三个月为197眼(91.20%);术前角膜曲率为43.94±1.35、术后第一天、术后一周的角膜曲率分别为44.98±1.06、44.45±1.18,与术前相比有显著性差异(p0.05),术后一个月、三个月的角膜曲率分别为44.13±1.27、44.02±1.24,与术前相比无显著性差异(p0.05);术源性散光于术后一天达到最大,随后逐渐减小,术后一个月、三个月与术后一天比较有显著性差异(p0.05),术后三个月与一个月比较无显著性差异(p0.05),术源性散光术后逐渐下降,并于一个月时趋于稳定。结论:3.0 mm透明角膜切口白内障超声乳化吸除及人工晶体植入术患者在术后一个月的角膜曲率基本稳定,恢复至术前状态,屈光状态趋于稳定,术源性角膜散光较小,术后视力恢复至较好状态。     

角膜生物力学的测量及临床应用进展

摘要：角膜是重要的屈光间质,约占眼光学系统总屈光力的70％;因其特殊的生理结构,可表现出复杂的生物力学性质。随着近年来科学技术的进步,用于测量角膜生物力学的方法也在不断更新,获得的生物力学参数也更加精确。越来越多的国内外研究团队将对角膜生物力学的研究同临床相结合,发现当角膜形态发生变化时,其生物力学参数也会发生相应的改变。因此,可以通过对患者角膜生物力学的测量来判断病变的发展程度,也可以根据所测得的力学参数来进行手术设计,甚至可以初判患者的愈后情况。但在角膜生物力学方面的研究仍缺乏深度,对其与部分临床疾病的联系仍缺乏充分的认知,仍需探讨如何将角膜生物力学检查更好地服务于临床。本文将对角膜生物力学的离体、活体测量方法及其目前在圆锥角膜、青光眼、翼状胬肉、屈光不正及屈光不正的矫正等临床方面的应用研究作一综述。     

垂体腺苷酸环化酶激活肽衍生多肽RHMP的重组制备及促角膜损伤修复的初步研究

利用基因工程技术高效制备具有促进角膜损伤修复功能的垂体腺苷酸环化酶激活肽(PACAP)衍生多肽RHMP,并在体外研究其生物学效应,为角膜疾病的治疗提供了新思路。采用基因重组技术表达重组肽RHMP,经Chitin-Beads柱纯化、HPLC及SDS-PAGE、质谱鉴定后,研究其对小鼠角膜损伤修复的影响。实验结果表明:利用基因重组技术制备的PACAP衍生多肽RHMP的分子量为3.4kDa,纯度为96%;将重组肽作用于创伤后的小鼠角膜,12h、24h、36h、48h后角膜修复率分别为(49.58±1.74)%、(93.66±3.39)%、(99.6±0.43)%、(99.8±0.14)%,而对照组修复率分别为(9.76±1.58)%、(29.02±1.63)%、(55.10±1.49)%、(78.59±2.52)%,P<0.001,差异具有统计学意义,重组肽RHMP可显著促进小鼠角膜损伤修复。因此,利用以上确立的表达、纯化策略,可实现新型基因重组PACAP衍生多肽RHMP的高效制备,重组多肽RHMP可快速有效地促进损伤角膜的修复,从而有望成为一种新型角膜损伤治疗药物;同时,建立的小鼠角膜上皮损伤模型可用于相关药物的生物学效应研究。     

超声乳化术与小切口囊外摘除术治疗白内障患者的疗效及对角膜内皮细胞及生存质量的影响

目的:探讨超声乳化术与小切口囊外摘除术治疗白内障患者的疗效及对角膜内皮细胞及生存质量的影响。方法:选取2015年3月到2017年6月在我院接受治疗的白内障患者203例,根据随机数字表法将患者分为对照组100例和观察组103例。对照组患者给予小切口囊外摘除术进行治疗,观察组给予超声乳化术进行治疗。于术前、术后1周、术后1个月、术后3个月对所有患者的视力进行检测。于术前、术后2周检测患者的眼角膜内皮细胞数量,并计算细胞密度和六角形细胞比率。于术前和术后1个月采用生活质量评定量表对患者的生活质量进行评测,记录患者术后出现的并发症。结果:术前、术后1个月、术后3个月,两组患者的视力比较差异无统计学意义(P0.05),术后1周观察组患者的视力明显高于对照组(P0.05);术后2周两组患者的细胞密度、六角形细胞比率均降低,对照组的细胞密度低于观察组(P0.05)。术前、术后1个月两组患者的自理能力、活动能力、社交能力、心理情绪得分比较差异无统计学意义(P0.05),术后1个月两组患者的自理能力、活动能力、社交能力、心理情绪得分均高于术前(P0.05)。两组患者的并发症发生率比较差异无统计学意义(P0.05)。结论:与小切口囊外摘除术相比,超声乳化术能在短期内更快的提升患者视力,且对患者的眼角膜内皮细胞损伤较小,但两种手术近期疗效和并发症情况基本一致,且对患者生活质量的影响无差异。     

下挖深度对节能日光温室环境因子日变化及空间分布的影响

对山东省泰安市下挖0、0.5、1.0、1.5m节能日光温室(不同下挖深度温室的结构参数完全一致)太阳直射辐射能截获量进行分析,研究了2009年12月20日—24日(冬至日前后)和2010年6月19日—23日(夏至日前后)温室环境因子日变化规律及其空间分布特点.结果表明:随着下挖深度的增加,下挖壁面在温室内的阴影面积逐渐增加,进入室内的太阳直射辐射逐渐由南向北迁移,地面辐射/后墙辐射值逐渐减小;日光温室下挖深度在0～1.0m时,下挖越深,温室气温和地温增温效果越显著、保温效果越好,下挖深度达1.5m时增温效果则显著下降、最低地温偏离度增大;下挖越深,温室内光照度越低、相对湿度越大.兼顾温室的采光与保温性能,泰安地区10m跨度的下挖式日光温室的适宜下挖深度应不超过1.0m.     

施磷量与施磷深度对玉米-大豆套作系统磷素利用率及磷流失风险的影响

为充分发挥间套作种植体系磷素高效利用优势、降低土壤磷素流失,采用田间试验分析了3种施磷(P_2O_5)水平(CP:168 kg·hm^-2;RP_1:135 kg·hm^-2;RP_2:101 kg·hm^-2)与3个施磷深度(D_1:集中施在距离地面5 cm处;D_2:集中施在距离地面15 cm处;D_3:于距离地面5、15 cm处各施一半)处理下玉米-大豆套作系统作物地上部生物量、籽粒产量、植株吸磷量、土壤全磷与速效磷含量、磷吸附-解吸特征,以期为优化西南玉米-大豆套作系统磷素管理提供理论依据.结果表明:与对照不施磷处理(P_0)相比,各施磷处理显著增加了作物地上部生物量、籽粒产量、植株吸磷量、土壤全磷和速效磷含量.相同施肥深度下,处理RP_1与CP相比,作物籽粒产量差异不显著,但显著提高了植株地上部吸磷量,因此RP_1处理的磷素表观利用率显著高于CP处理.相同施磷量下,不同施磷深度间比较,作物地上部生物量、籽粒产量、植株吸磷量、土壤全磷和速效磷含量均以D_2处理最高.依据土壤磷的吸附-解吸特征参数可知,当施磷深度为D_2、施磷量为RP_1时,土壤对磷的固持能力最强,在降低磷素流失上表现出较强优势.因此,玉米-大豆套作系统中适当减少磷肥施用量和加大磷肥施用深度在保证作物产量的同时,有利于提高磷素利用率,减少土壤磷流失.     

清醒镇静与深度镇静在食管胃底静脉曲张内镜诊疗术的麻醉效果及安全性分析

摘要 目的：研究在清醒镇静与深度镇静下实施食管胃底静脉曲张内镜诊疗术的麻醉效果及安全性分析。方法：选取在我院2020年5月至2022年5月收治的94例食管胃底静脉曲张患者,按照随机数字表法将静脉曲张患者分为对照组和观察组,每组47例。对照组采用清醒镇静（咪达唑仑+芬太尼）,观察组采用深度镇静在对照组基础上增加丙泊酚。观察对照组与观察组手术治疗时患者基生命体征变化以及手术治疗后的麻醉效果及安全性。比较两组患者治疗后治疗后的总有效率。结果：观察组总有效率显著高于对照组,差异具有统计学意义（P<0.05）。观察组出院时间、麻醉达标时间及术后拔管时间显著小于对照组,差异具有统计学意义（P<0.05）。各时间点实验组患者HR相比差异无显著性（P＞0.05）。在T2,T3,T4时,实验组患者MAP、HR均较对照组显著降低（P＜0.05）。两组患者手术时Ramsay评分和术后满意度比较,两组患者均无统计学差异。对照组和观察组不良反应发生率分别为12.75%和8.49%,两组比较差异无统计学意义（P>0.05）。结论：深度镇静对于食管胃底静脉曲张行内镜诊疗疗效显著而且安全可靠,疗程短,见效快,恢复快,患者接受程度高,提高治疗成功率,值得进行推广。     

全飞秒激光与飞秒激光辅助Lasik治疗高度近视患者的效果及对角膜曲率、视觉质量的影响分析

摘要 目的：探究全飞秒激光与飞秒激光辅助Lasik治疗高度近视患者的效果,并分析治疗对患者角膜曲率、视觉质量的影响。方法：选择2020年7月至2022年7月在我院接受治疗的120例（240眼）高度近视患者为研究对象,按照随机数字表法结合患者意愿的方式将其区分为研究组（n=60,接受飞秒激光辅助Lasik治疗）与对照组（n=60,接受全飞秒激光治疗）,对比两组患者术前术后调制传递函数截止频率（MTF）值及客观散射指数（OSI）、角膜曲率变化、屈光度差异、视力情况差异,统计两组患者各类并发症发生率并进行比较。结果：（1）两组患者术前MTF值及OSI组间差异无统计学意义（P>0.05）,术后研究组患者的MTF值和OSI值均明显低于对照组,差异具有统计学意义（P<0.05）;（2）术前、术后90 d两组患者的最佳矫正视力组间差异无统计学意义（P>0.05）,但组内前后比较两组患者的最佳矫正视力均较术前有明显提高（P<0.05）;（3）术前两组患者的角膜前表面曲率以及后表面曲率组间差异均无统计学意义（P>0.05）,术后90 d时开展组间比较,研究组患者角膜前表面曲率中K1、K2以及Km值均明显低于对照组（P<0.05）,但后表面曲率中K1、K2以及Km值组间差异无统计学意义（P>0.05）;进一步分析显示,两组患者术前术后前表面曲率K1、K2以及Km值有明显变化（P<0.05）,后表面曲率K1、K2以及Km值前后差异无统计学意义（P>0.05）;（4）统计研究组患者共出现弥漫性层间反应2例,感染1例,角膜内生1例,并发症总发生率3.33%（4/120）,明显高于对照组的0.00%（0/120）（P<0.05）。结论：全飞秒激光和飞秒激光辅助Lasik术对高度近视均具有较好的治疗效果,相比于全飞秒激光术,飞秒激光辅助Lasik术在改善患者视觉质量方面明显占优,但其并发症发生率同样更高,全飞秒激光术术后视觉质量,但安全性更高,建议临床上结合患者实际情况灵活选择术式,以改善高度近视患者预后。     

基于无人机影像与面向对象-深度学习的滨海湿地植物物种分类

明确滨海湿地植物物种类型及其分布状况是实现滨海湿地精细化生物多样性监测的基础,对于滨海湿地的保护管理与生态可持续发展均具有重要意义。本研究以无人机可见光遥感影像为基础数据源,在定量分析最优分割尺度与最优分类特征组合的基础上,应用面向对象-U-net深度学习方法对闽江河口湿地植物物种类型进行分类,并与K最近邻、决策树、随机森林和贝叶斯分类方法进行精度对比分析,以期为滨海湿地植物物种遥感精细分类与生物多样性保护管理提供方法借鉴与科学参考。研究结果表明,利用面向对象-U-net深度学习方法提取不同滨海湿地植物物种类型的分类精度可达95.67%,总体精度较其他分类方法提高6.67%–13.67%, Kappa系数提高0.12–0.31,且分类整体性好。此外,实现植物物种光谱特征、形状特征、纹理特征与高度特征的最优特征选择对于有效提高湿地植物物种信息分类精度具有重要作用,应用最优分割尺度实现影像分割可提高整体分类效率。     

同轴常规切口与微切口超声乳化术对白内障患者视力、角膜散光以及泪液炎性因子的影响

摘要 目的：探讨同轴常规切口与微切口超声乳化术对白内障患者角膜散光、视力以及泪液炎性因子的影响。方法：选取2018年1月~2019年12月期间我院收治的白内障患者80例,根据随机数字表法分为对照组（n=40）和研究组（n=40）,对照组患者采用同轴常规切口超声乳化术,研究组采用同轴微切口超声乳化术,比较两组患者术中前房稳定性、最佳矫正视力、平均超声能量、角膜散光程度、有效超声乳化时间、泪液炎性因子以及术后恢复时间,记录两组术后并发症发生率。结果：两组术后1d、术后1周、术后1个月、术后3个月最佳矫正视力呈升高趋势,且研究组高于对照组（P<0.05）。研究组术后1周、术后1个月、术后3个月角膜散光程度低于对照组（P<0.05）。两组患者有效超声乳化时间、平均超声能量、术中前房稳定人数占比比较差异无统计学意义（P>0.05）;研究组术后恢复时间短于对照组（P<0.05）。两组术后3个月泪液白介素-6（IL-6）、肿瘤坏死因子-α（TNF-α）均下降,且研究组低于对照组（P<0.05）。两组术后并发症发生率比较差异无统计学意义（P>0.05）。结论：与同轴常规切口超声乳化术相比,同轴微切口超声乳化术治疗白内障患者,在改善患者角膜散光、视力以及泪液炎性因子水平方面效果显著,且不增加术后并发症发生率。     

Comparison of Anterior Segment Biometric Measurements between Pentacam HR and IOLMaster in Normal and High Myopic Eyes

Purpose

To compare the anterior chamber depth (ACD), keratometry (K) and astigmatism measurements taken by IOLMaster and Pentacam HR in normal and high myopic (HM) eyes.

Design

A prospective observational case series.

Methods

Sixty-six normal eyes and 59 HM eyes underwent ACD, keratometry and astigmatism measurements with both devices. Axial length (AL) was measured on IOLMaster. The interdevice agreement was evaluated using the Bland-Altman analysis and paired t-test. The correlations between age and AL & ACD were analyzed. Vector analysis was used to compare astigmatism measurements.

Results

The ACD from IOLMaster and Pentacam HR was different for the normal group (P = 0.003) but not for the HM group (P = 0.280). IOLMaster demonstrated higher steep K and mean K values than Pentacam HR for both normal and HM groups (P<0.001 for all). IOLMaster also have higher flat K values for the HM groups (P<0.001) but were statistically equivalent with Pentacam HR for the normal group (P = 0.119) IOLMaster and Pentacam HR were different in astigmatism measurements for the normal group but were statistically equivalent for the HM group. For the normal group, age was negatively correlated with AL, IOLMaster ACD and Pentacam HR ACD (r = -0.395, P = 0.001; r = -0.715, P < 0.001; r = -0.643, P < 0.001). For the HM group, age was positively correlated with AL but negatively correlated with IOLMaster ACD and Pentacam HR ACD (r = 0.377, P = 0.003; r = -0.392, P = 0.002; r = -0.616, P < 0.001).

Conclusions

The IOLMaster and Pentacam HR have significant difference in corneal power measurements for both normal and HM groups. The two instruments also differ in ACD and astigmatism measurement for the normal group. Therefore, a single instrument is recommended for studying longitudinal changes in anterior segment biometric measurements. Age should be considered as an influencing factor for both AL and ACD values in the normal and HM group.     

Anterior Chamber Depth and Refractive Change in Late Postoperative Capsular Bag Distension Syndrome: A Retrospective Analysis

Purpose

To assess the characteristic findings and effects of laser capsulotomy in patients with late postoperative capsular bag distension syndrome (CBDS).

Methods

Twenty patients diagnosed with late postoperative CBDS between July 2010 and August 2013 were retrospectively reviewed. Before and 1 week after capsulotomy, changes in the anterior chamber depth (ACD) were assessed using ultrasound biomicroscopy. Changes in the refractive status and uncorrected visual acuity (UCVA) were also measured 1 week and 1 month after capsulotomy. For patients who received bilateral cataract surgery, preoperative ACD and axial length measured by IOLMaster were compared between the two eyes.

Results

Twenty-two eyes from 20 patients who had undergone laser capsulotomy showed a mean UCVA improvement of 0.27 ± 0.24 logMAR (range, 0.00–0.90). ACD was increased by an average of +0.04 mm (95% confidence interval, +0.01 to +0.06 mm, p = 0.034), equivalent to predicted refractive change of +0.10 D. The discrepancy between actual (+1.33 D) and predicted refractive change after capsulotomy suggests that refractive change may not be generated from IOL displacement in late postoperative CBDS. Preoperative ACD was deeper in the eye with late postoperative CBDS in all bilaterally pseudophakic patients (mean, 3.68 mm vs. 3.44 mm in the fellow eye, p = 0.068).

Conclusions

Late postoperative CBDS showed refractive changes that were resolved successfully after laser capsulotomy. The convex lens effects of opalescent material in the distended capsular bag may play a major role in myopic shift. A larger preoperative ACD is possibly associated with the development of late postoperative CBDS.     

The Relationship between Corvis ST Tonometry Measured Corneal Parameters and Intraocular Pressure,Corneal Thickness and Corneal Curvature

The purpose of the study was to investigate the correlation between Corneal Visualization Scheimpflug Technology (Corvis ST tonometry: CST) parameters and various other ocular parameters, including intraocular pressure (IOP) with Goldmann applanation tonometry. IOP with Goldmann applanation tonometry (IOP-G), central corneal thickness (CCT), axial length (AL), corneal curvature, and CST parameters were measured in 94 eyes of 94 normal subjects. The relationship between ten CST parameters against age, gender, IOP-G, AL, CST-determined CCT and average corneal curvature was investigated using linear modeling. In addition, the relationship between IOP-G versus CST-determined CCT, AL, and other CST parameters was also investigated using linear modeling. Linear modeling showed that the CST measurement ‘A time-1’ is dependent on IOP-G, age, AL, and average corneal curvature; ‘A length-1’ depends on age and average corneal curvature; ‘A velocity-1’ depends on IOP-G and AL; ‘A time-2’ depends on IOP-G, age, and AL; ‘A length-2’ depends on CCT; ‘A velocity-2’ depends on IOP-G, age, AL, CCT, and average corneal curvature; ‘peak distance’ depends on gender; ‘maximum deformation amplitude’ depends on IOP-G, age, and AL. In the optimal model for IOP-G, A time-1, A velocity-1, and highest concavity curvature, but not CCT, were selected as the most important explanatory variables. In conclusion, many CST parameters were not significantly related to CCT, but IOP usually was a significant predictor, suggesting that an adjustment should be made to improve their usefulness for clinical investigations. It was also suggested CST parameters were more influential for IOP-G than CCT and average corneal curvature.     

Distribution of Posterior Corneal Astigmatism According to Axis Orientation of Anterior Corneal Astigmatism

Purpose

To investigate the distribution of posterior corneal astigmatism in eyes with with-the-rule (WTR) and against-the-rule (ATR) anterior corneal astigmatism.

Methods

We retrospectively examined six hundred eight eyes of 608 healthy subjects (275 men and 333 women; mean age ± standard deviation, 55.3 ± 20.2 years). The magnitude and axis orientation of anterior and posterior corneal astigmatism were determined with a rotating Scheimpflug system (Pentacam HR, Oculus) when we divided the subjects into WTR and ATR anterior corneal astigmatism groups.

Results

The mean magnitudes of anterior and posterior corneal astigmatism were 1.14 ± 0.76 diopters (D), and 0.37 ± 0.19 D, respectively. We found a significant correlation between the magnitudes of anterior and posterior corneal astigmatism (Pearson correlation coefficient r = 0.4739, P<0.001). In the WTR anterior astigmatism group, we found ATR astigmatism of the posterior corneal surface in 402 eyes (96.6%). In the ATR anterior astigmatism group, we found ATR posterior corneal astigmatism in 82 eyes (73.9%). Especially in eyes with ATR anterior corneal astigmatism of 1 D or more and 1.5 D or more, ATR posterior corneal astigmatism was found in 28 eyes (59.6%) and 9 eyes (42.9%), respectively.

Conclusions

WTR anterior astigmatism and ATR posterior astigmatism were found in approximately 68% and 91% of eyes, respectively. The magnitude and the axis orientation of posterior corneal astigmatism were not constant, especially in eyes having high ATR anterior corneal astigmatism, as is often the case in patients who have undergone toric IOL implantation.     

ABCC5, a Gene That Influences the Anterior Chamber Depth,Is Associated with Primary Angle Closure Glaucoma

Anterior chamber depth (ACD) is a key anatomical risk factor for primary angle closure glaucoma (PACG). We conducted a genome-wide association study (GWAS) on ACD to discover novel genes for PACG on a total of 5,308 population-based individuals of Asian descent. Genome-wide significant association was observed at a sequence variant within ABCC5 (rs1401999; per-allele effect size = −0.045 mm, P = 8.17×10⁻⁹). This locus was associated with an increase in risk of PACG in a separate case-control study of 4,276 PACG cases and 18,801 controls (per-allele OR = 1.13 [95% CI: 1.06–1.22], P = 0.00046). The association was strengthened when a sub-group of controls with open angles were included in the analysis (per-allele OR = 1.30, P = 7.45×10⁻⁹; 3,458 cases vs. 3,831 controls). Our findings suggest that the increase in PACG risk could in part be mediated by genetic sequence variants influencing anterior chamber dimensions.     

Corneal Curvature Radius and Associated Factors in Chinese Children: The Shandong Children Eye Study

PurposeTo investigate the distribution of the (CCR) and its associated factors in children.MethodsUsing a random cluster sampling method, the school-based, cross-sectional Shandong Children Eye Study included children aged 4 to 18 years from the rural county of Guanxian and the city of Weihai in the province of Shandong in East China. CCR was measured by ocular biometry.ResultsCCR measurements were available for 5913 (92.9%) out of 6364 eligible children. Mean age was 10.0±3.3 years, and mean CCR was 7.84±0.27 mm (range: 6.98 to 9.35 mm). In multivariate linear regression analysis, longer CCR (i.e. flatter cornea) was significantly associated with the systemic parameters of male sex (P<0001;standardized regression coefficient beta: -0.08;regression coefficient B:-0.04; 95% Confidence Interval (CI):-0.05,-0.03), younger age (P<0.001;beta:-0.37;B:-0.03;95%CI:-0.04,-0.03), taller body height (P = 0.002;beta:0.06;B:0.001;95%CI:0.000,0.001), lower level of education of the father (P = 0.001;beta:-0.04;B:-0.01;95%CI:-0.02,-0.01) and maternal myopia (P<0.001;beta:-0.07;B:-0.04;95%CI:-0.06,-0.03), and with the ocular parameters of longer ocular axial length (P<0.001;beta:0.59;B:0.13;95%CI:0.12,0.14), larger horizontal corneal diameter (P<0.001;beta:0.19;B:0.13;95%CI:0.11,0.14), and smaller amount of cylindrical refractive error (P = 0.001;beta:-0.09;B:-0.05;95%CI:-0.06,-0.04).ConclusionsLonger CCR (i.e., flatter corneas) (mean:7.84±0.27mm) was correlated with male sex, younger age, taller body height, lower paternal educational level, maternal myopia, longer axial length, larger corneas (i.e., longer horizontal corneal diameter), and smaller amount of cylindrical refractive error. These findings may be of interest for elucidation of the process of emmetropization and myopization and for corneal refractive surgery.     

Fluid Mechanics of the Human Eye: Aqueous Humour Flow in The Anterior Chamber

We consider and compare the various different kinds of flow that may take place in the anterior chamber of a human eye. The physical mechanisms responsible for causing such flows may be classified as follows: (i) buoyancy-driven flow arising from the temperature difference between the anterior surface of the cornea and the iris, (ii) flow generated by the aqueous production of the ciliary body, (iii) flow generated by the interaction between buoyancy and gravity while sleeping while sleeping in a face-up position, (iv) flow generated by phakodenesis (lens tremor), (v) flow generated by Rapid Eye Movement (REM) during sleep. Each flow is studied using a traditional fluid mechanics/asymptotic analysis approach. We also assess the veracity of a hypothesis that was recently advanced [see Maurice, D.M., 1998. The Von Sallman Lecture 1996: An ophthalmological explanation of REM sleep. Exp. Eye. Res. 66, 139–145, for details] to suggest that, contrary to previous opinion, the purpose of REM during sleep is to ensure corneal respiration in the absence of the buoyant mixing that routinely takes place due to (i) above during waking conditions.