Experimentally induced myopia does not affect post-hatching development of the chick lens

Myopia, as characterized by a large refractive error (e.g. -10.7 +/- 0.4 D), was induced in post-hatch chicks by a 14 day application of a goggle that was designed to blur the retinal image. In comparison to untreated eyes, the treated eye showed significant changes in wet eye weight and both axial and equatorial lengths. However, the lenses of myopic and non-myopic eyes were not significantly different in focal characteristics, light transmittance or total soluble protein content. Thus the lens neither contributes to, nor compensates for the large refractive error observed in experimentally induced myopia.     

高度近视眼进展与眼内压的相关分析

目的:通过对高度近视眼进展与眼内压的相关关系的分析,探讨高度近视眼与原发性开角型青光眼的内在联系。方法:选取高度近视眼患者104例208眼,随机平均分成2组,治疗组给予派立明眼药水滴眼降眼压治疗3次/d,对照组给予人工泪液滴眼3次/d。定期进行裸眼视力、矫正视力、自动验光仪散瞳验光、裂隙灯显微镜、眼底、视野检查以及A型超声波测量眼轴、非接触眼压计监测眼压,连续随访2a,比较两组在屈光状态、眼轴长度、眼内压、视野的差异。结果:随访2a两组视野并未呈现明显变化。治疗组平均眼内压13.25±4.43mmHg,平均屈光度-8.38±1.93D,对照组平均眼内压15.53±4.37mmHg,平均屈光度-9.32±1.81D,两组比较差异具有统计学意义;眼轴治疗组为25·94±1.08mm,对照组为25.56±1.02mm,两两比较差异无统计学意义。但随着眼轴的延长,高度近视眼的屈光度增加。结论:高度近视眼进展与眼内压可能有一定的内在联系,应重视对高度近视眼的眼内压监测,防止由于高度近视眼的眼底改变而漏诊青光眼。     

Topical vanadate lowers intraocular pressure in rabbits

In unanesthetized rabbits the topical application of vanadate lowered intraocular pressure. Tonographic outflow facility and episcleral venous pressure were unaltered by topical vanadate. As estimated from the tonographic data, aqueous humor flow was reduced by approximately 30%. Posterior chamber aqueous humor ascorbate increased in the eye receiving topical vanadate, and this was compatible with a decreased rate of aqueous humor flow. Topical vanadate did not alter anterior chamber aqueous humor protein or cyclic AMP. In five monkeys intraocular pressure was also significantly reduced by topical vanadate.     

Thyroxine increases the rate but does not alter the pattern of innervation during embryonic chick corneal development

PURPOSE: Embryonic chick corneal nerves reach limbal mesenchyme by embryonic day (E)5, encircle the cornea in several days, then defasciculate into the stroma simultaneously from all sides, while extracellular keratan sulfate proteoglycan (KSPG) accumulates from posterior to anterior stroma. Precocious thyroxine (T4)-induced increases in corneal thinning/transparency are blocked by 2-thiouracil (2-TU) inhibition of T3 synthesis. The hypothesis for this study was that precocious T4 exposure increases corneal innervation similarly. METHODS: E8 embryos received T4, 2-TU, T4+2-TU, or buffer; corneas were harvested on E12. Corneal nerves were stained with neuronal beta-tubulin-specific TuJ1 antibody or chick nerve-specific CN antibody. Corneal thickness was determined from cryostat sections, and mRNA expression was measured by real-time PCR. RESULTS: Nerves avoided the cornea until E9, then entered the anterior stroma, extended toward and reached the cornea center by E14, and never invaded posterior stroma. E7 to E18 corneal expressions of nerve growth factor and neurotrophin-3 genes were unchanged; receptor gene expressions rose. E7 to E12 semaphorin 3A and 3F and ephrin A2 and A5 expressions did not change significantly; semaphorin and ephrin/eph expressions increased from E9 to E18. E8 T4 administration increased nerve extension by E11, but did not alter circumferential penetration, anterior-only penetration, or neurotrophin expressions. 2-TU prevented T4-induced precocious corneal thinning, but augmented T4 nerve stimulation. CONCLUSIONS: No changes in corneal neurotrophin or nerve pathfinding gene expressions accompany corneal transition to nerve growth cone permissiveness. T4 increases corneal nerve penetration rates by a non-T3-dependent mechanism. Results are consistent with possible roles for corneal KSPGs in regulating corneal nerve growth.     

Afocal magnification does not influence chick eye development.

In defocus-induced ametropia experiments, retinal blur circles are a likely source of information as to the magnitude but not the sign of the defocus. However, magnification (and minification) produced by the lenses may be a cue. In this study, 1-day-old broiler chicks (N = 13) were treated monocularly for 7 days with special goggles containing approximately afocal iseikonic lenses which were designed to produce 10% retinal image magnification. This is a little less than the magnification produced by +10 D defocusing lenses used to produce about 10 D of hyperopia in earlier work. Intraocular dimensions of both eyes were measured by A-scan ultrasonography on the first and last day. Refractive states of both eyes were measured daily with a retinoscope and trial lenses. After the birds were sacrificed, the eyes were enucleated, weighed, and measured with calipers. Before the treatment there was no difference in the refractive state or dimensions of the right and left eyes. After 1 week of goggle wear there was still no significant difference between the eyes in spite of the magnification produced by the goggles. These data suggest that factors other than magnification are responsible for the ability of the eye to respond to the sign of defocus.     

调节诱导的眼内压变化在近视发生发展中的作用

在近视的发生发展中,近距离工作是最重要的环境因素。但近距离工作及其诱导的调节作用是通过何种机制导致近视发生发展并不清楚。近年来,科学家们发现持续视近可通过引起眼轴暂时性延长而导致暂时性近视,并认为这一过程可能是通过调节诱导的眼内压（IOP）和生物力学结构的变化介导的。现就调节对IOP和眼球结构的机械作用及IOP在近视的发生发展中的作用作一综述,以加深对近视发生发展机制的理解。     

Lacquer crack lesions in experimental chick myopia

• Background: Lacquer crack lesion (LCL) is a complication of human pathologic myopia, accompanied by loss of retinal pigment epithelium (RPE) and break of Bruch’s membrane. The present paper describes comparable lesions occurring in prolonged experimental myopia in the chick. • Methods. Form-deprivation myopia was induced by unilateral eyelid suturing on the 1st day after hatching. Bruch’s membrane in NaOH hydrolyzed preparations and vascular corrosion casts of the choroidal vasculature were examined with scanning electron microscopy. Histological changes in the retina and choroid were also examined with light and transmission electron microscopy. • Results: Pale and linear lesions were found in the myopic chick eyes at the age of 8 weeks. In the lesion area, Bruch’s membrane was totally broken up and the network of choriocapillaries was totally ruptured with highly atrophied marginal capillaries. The retina was continuous, but was depressed to form a groove in the lesion with the apparently intact inner retina and degenerated photoreceptor cells. Attenuated fibroblasts encompassed the outer circumference of the lesion. RPE cells were scattered in the tissue space inside the fibroblastic investment and also in the choroidal stroma without their polarity. • Conclusion: The formation of LCL was suggested to be a result of passive stretch exerted upon Bruch’s membrane and the capillary network due to abnormal enlargement of the myopic eyes. These results may promote further understanding of the mechanism regarding the development of human lacquer cracks. Received: 2 May 1997 Accepted: 30 July 1997     

Topical 8-bromo-cyclic GMP lowers intraocular pressure in rabbits

The topical application of 8-bromo-3'-5'-cyclic guanosine monophosphate (8BrcGMP) produces significant decreases in intraocular pressure (IOP) in rabbit eyes. Maximum effects are obtained with a 4% concentration, and IOP is reduced significantly (P less than 0.001) between 30 and 240 min after administration of the agent. The decrease in IOP occurs without significant change in tonographic outflow facility. A significant further decrease in IOP can be induced by topical 8BrcGMP in rabbits whose IOP has been lowered by the systemic administration of the carbonic anhydrase inhibitor acetazolamide.     

鸡眼形觉剥夺性近视的实验研究

目的建立鸡形觉剥夺近视模型,观察形觉剥夺眼屈光、巩膜形态学改变。方法将孵出后一天的家鸡25只,以右眼为形觉剥夺眼,左眼为开放对照眼,2周后进行检影验光,并摘出眼球,测量眼轴长和赤道径。观察巩膜软骨层中细胞密度、增殖细胞率,并测量角巩膜的干湿重。结果剥夺眼的屈光度平均为-11.9±4.6D,对照眼平均为+3.0±1.2D,两者差异有显著性意义,轴长较对照眼明显延长（P<0.01）,剥夺眼的巩膜干湿重均明显重于对照眼（P<0.01）,并且巩膜软骨中增殖细胞率明显高于对照眼（P<0.05）,但细胞密度则低于对照眼（P<0.05）。结论鸡眼形觉剥夺可产生一定程度的近视和眼轴延长,并伴随着巩膜的病理形态改变。     

Acetylsalicylic acid does not reduce the intraocular pressure variation in ocular hypertension or glaucoma

The purpose of this study was to measure if intraocular pressure (IOP) and IOP variations in patients with ocular hypertension and glaucoma are decreased by acetylsalicylic acid (ASA). The hypothesis to be tested was that short-term fluctuations in the IOP are caused by breaks of the inner wall of Schlemm's canal that are repaired by platelets inducing a cycle of breaks and repair. Furthermore, prostaglandins affect uveoscleral outflow and ASA inhibits prostaglandin biosynthesis and platelet aggregation. This implies that ASA may have complex effects on the IOP and its variations.In 28 patients with ocular hypertension or glaucoma the IOP was measured seven times during 2 hr on two succeeding days. Five hundred mg ASA or placebo was administrated orally in a masked fashion 15 hr prior to the second session. After wash-out, this procedure was repeated with a cross-over design. The same study outline was used in 28 glaucoma patients except for the cross-over design.There were no statistically significant differences in the mean IOP or in the IOP variations between the placebo treated and the ASA treated eyes in either group, and there were no significant differences between the day before and after treatment in any group. The results suggest that ASA does not affect IOP variations in a clinically significant way and that a single dose of ASA has no significant effect on mean IOP.     

儿童近视性屈光参差眼的眼压分析

目的为了探讨近视和眼压的关系,本文对近视性屈光参差患者双眼的眼压进行了测量观察。方法对49例年龄为7～14岁、双眼屈光度差值≥2.5D(2.50D～6.62D)的屈光参差者的双眼屈光度、眼压、中央角膜厚度和角膜曲率分别进行测量。结果近视性屈光参差患者双眼中高屈光度眼(7.44D±2.57D)的眼压(17.18 mmHg±2.56 mmHg)与低屈光度眼(3.89D±2.41D)的眼压(17.22 mmHg±2.82 mmHg)无统计学显著性差异(t=-0.075,P=0.940)。近视屈光度与眼压(r=0.040,P=0.372)、中央角膜厚度与眼压(r=0.011,P=0.808)和角膜曲率(r=0.062,P=0.166)均无相关性。结论儿童近视性屈光参差双眼的屈光度与眼压无关。     

The preoperative intraocular pressure level predicts the amount of underestimated intraocular pressure after LASIK for myopia

AIMS: To evaluate the statistical significance of the parameters that affect underestimation of intraocular pressure (IOP) after laser in situ keratomileusis (LASIK) for myopia. METHODS: In this prospective case series study, patient age, axial length, preoperative corneal curvature, preoperative central corneal thickness (CCT), preoperative IOP, and ablation depth were studied to determine whether they affect the underestimation of IOP in the right eyes of 100 consecutive patients who underwent LASIK. RESULTS: The preoperative IOP was the most important parameter for an amount of underestimated Goldmann applanation tonometric IOP (GAT) and non-contact tonometric IOP (ncIOP) at 1 month (r = 0.654, p<0.0001, R(2) = 0.427, and r = 0.694, p<0.0001, R(2) = 0.481, respectively) and 3 months (r = 0.637, p<0.0001, R(2) = 0.406, and r = 0.726, p<0.0001, R(2) = 0.527, respectively). Patient age was statistically significant for underestimating the GAT at 1 month, and both the ablation depth and CCT were statistically significant parameters for underestimating the ncIOP at 1 month and at 3 months by stepwise multiple regression analysis (F>4.000). However, these parameters had small bivariate correlation coefficients, and were considered as minor parameters. CONCLUSION: Preoperative IOP is the most important parameter that affects an underestimation of IOP after LASIK for myopia. Eyes with a higher true IOP have a larger underestimation of the IOP after LASIK for myopia. From these results, the importance of the modulus of elasticity on IOP measurements was discussed.     

基质金属蛋白酶-2在实验性近视眼鸡巩膜成纤维细胞的表达

目的研究基质金属蛋白酶-2(matrix metalloproteinases-2,MMP-2)在形觉剥夺性近视眼(formdeprivation myopia,FDM)鸡巩膜成纤维细胞的表达。方法20只1d龄来亨雏鸡以半透明眼罩遮盖右眼14d制备FDM动物模型,随机取10只FDM眼去除遮盖7d作为恢复组,均以对侧未遮盖眼作为对照组。将各组小鸡眼后极部巩膜成纤维细胞作体外培养并传2代,行光镜与透射电镜形态学观察,并采用SABC免疫细胞化学染色法检测MMP-2的表达,进行计算机图像分析及统计学检验。结果培养的正常鸡巩膜成纤维细胞胞浆表达MMP-2,阳性灰度值为192·2319±1·2521。FDM组细胞MMP-2染色阳性灰度值为168·1730±5·0039,较对照组MMP-2表达明显增高(P<0·01)。恢复组阳性灰度值为180·4001±2·3522,其MMP-2表达较FDM组有所回降(P<0·01),但与对照组相比仍有升高,差异有显著性(P<0·01)。结论MMP-2参与形觉剥夺性近视眼的发生发展与恢复的过程,在近视发生机制中起重要作用。     

高度近視患者白内障術後的眼壓燮化觀察

目的觀察高度近視患者白内障術後的眼壓變化,評價手術方式對其的影響.方法高度近視白内障患者190例,分爲ECCE和PHACO兩組,分别觀察.結果術後随訪中,ECCE組眼壓升高25例,占21.93%,開角型青光眼3例,占2.63%;PHACO組眼壓升高3例,占3.94%,可疑開角型青光眼1例.結論高度近視白内障患者術後眼壓升高存在一過性升高和青光眼發作兩種情况,超聲乳化術後眼壓升高較少.     

高度近视LASIK术后眼压值的变化

目的 探讨LASIK治疗高度近视术后眼压变化与角膜切削量的关系.方法 427例高度近视患者按屈光度分成A组(-6.0D至-10.00D)和B组(-10.0至-21.0D),施行LASIK术前后用非接触眼压计(NCT)测量眼压,并分析其与角膜切削量的关系.结果 两组眼压术后明显下降.A组为12.21±3.22 mmHg;B组为10.48±2.76mmHg(P＜0.001).角膜切削量占术前角膜中央厚度A组为12.4～18.9 %;B组为19.0～34.7 %(P＜0.01).结论 LASIK治疗高度近视术后NCT眼压值下降与角膜中央厚度变薄和抗压强度减弱有关.     

Subconjunctival suspension of RU486 lowers intraocular pressure in normal rabbits.

RU486 is both a progesterone blocker and a corticosteroid blocker (peripheral). Subconjunctival injections of 0.2 ml of a 1% suspension of RU486 powder (2 mg) were given twice weekly to one eye chosen at random of 12 rabbits. The fellow eye received the same volume, 0.2 ml, of vehicle (normal saline) only. Ocular tension was measured twice daily for six days per week by an Alcon pneumatonograph, the tonometrist(s) being unaware of which eyes were treated and which untreated. A small but significant reduction in intraocular pressure, about 0.7 mmHg, occurred in treated eyes. No intereye difference in the ocular hypertensive response to intraperitoneal injections of distilled water (50 ml/kg) was found. Clinical trials are planned in which a larger fall is expected because the trabecular meshwork in patients with open-angle glaucoma or ocular hypertension is presumably more affected by (normal) tissue levels of corticosteroid.