Corneal diameter and axial length in congenital glaucoma

The corneal diameter was recorded and the ocular axial length measured by A-scan ultrasonography in 31 eyes of 17 children (ages 0.05 to 7.0 years) who had undergone or were about to undergo surgery for primary congenital glaucoma. These measurements were also done in 60 normal eyes of 33 children (ages 0.20 to 9.6 years) undergoing nonophthalmic surgery. Both measures were usually greater than normal in the glaucomatous eyes. However, the corneal diameter was more sensitive than the axial length in identifying congenital glaucoma. The axial length measurement did not provide additional useful information for any of the eyes. We conclude that the corneal diameter is a more reliable guide than the axial length in the assessment of congenital glaucoma. A transparent plastic gauge for rapid and accurate measurement of the corneal diameter is described.     

Ocular axial length in unilateral congenital cataracts and blepharoptosis

Biometry performed in patients with unilateral dense congenital cataracts and unilateral complete blepharoptosis did not show a consistent elongation of the involved eye. The antero-posterior axis of the visually deprived eye was longer than that in the normal fellow eye in some but shorter or unchanged in other patients. These findings are in accord with the hypothesis gained from monkey experiments that visual deprivation during infancy may deregulate axial growth of the eye. However, unlike in monkeys where axial elongation usually prevails, this effect of visual deprivation is less predictable in humans.     

Changes in axial length following trabeculectomy and glaucoma drainage device surgery

AIM: This study examines the changes in axial length (AL) after trabeculectomy and glaucoma drainage device (GDD) surgery and enabled an equation to be derived allowing prediction of AL change after filtering surgery. METHODS: This was a prospective, interventional case series from the Glaucoma Service of the Doheny Eye Institute. Patient population: One eye of 39 patients undergoing trabeculectomy and 22 undergoing Baerveldt tube shunt implantation for uncontrolled glaucoma. INTERVENTION: These patients had AL measurements by non-contact, partial coherence interferometry preoperatively, at 1 week, 1 month, and >3 months after surgery. MAIN OUTCOME MEASURES: Axial length and intraocular pressure were compared at preoperative and postoperative visits. Postoperative intraocular pressure (IOP) was categorised as hypotonous (0-4 mm Hg), low (5-9), normal (10-17), and high (18 or more). RESULTS: There was a statistically significant reduction in IOP after 3 months of -12.8 (SD 1.5) mm Hg following trabeculectomy (p<0.001), and -10.7 (1.9) mm Hg after GDD (p<0.001). There was a statistically significant reduction in AL, which was similar after trabeculectomy and GDD at all time points (p<0.001), of -0.15 (0.03) and -0.21 (0.04) mm (1 week), -0.18 (0.02) and -0.10 (0.02) mm (1 month), and -0.16 (0.03) and -0.15 (0.03) mm (3 months). At 3 months or later the AL reduction was related to postoperative IOP and to the amount of IOP reduction (p<0.05, stepwise multiple regression). 10.2% (4/39) of trabeculectomy patients had hypotony after 3 months, with a mean AL reduction (-0.39 (0.11)) that was statistically significantly lower (p<0.01) than the other trabeculectomy eyes (-0.14 (0.15)). CONCLUSIONS: There is a small but statistically significant decrease in AL after both trabeculectomy and GDD surgery, greater in eyes that are hypotonous after surgery. The authors suggest that AL reduction can be predicted after 3 months by the formula: AL reduction (mm) = -199+0.006 x IOP reduction+0.008 x final IOP.     

Long axial length as risk factor for normal tension glaucoma

Background  The high prevalence of normal tension glaucoma (NTG) in the Japanese requires special screening tests other than measurements of only the intraocular pressure (IOP). This study was carried out to determine whether there is a significant association between the axial length of the eye and the presence of NTG. Methods  We reviewed the medical records of all patients who were scheduled to undergo cataract surgery alone or combined with glaucoma surgery at the same time. There were 87 patients with NTG, 137 with POAG, and 978 non-glaucomatous control cases. The axial length, IOP, curvature of the anterior corneal surface, age, and gender were determined at the time of the operation. If both eyes had surgery, data from only the right eyes were analyzed. An association of these parameters with NTG and POAG was analyzed by logistic regression analysis. The three groups were analyzed for differences in the axial length using the Kruskal-Wallis test followed by the Mann-Whitney U test. Results  The axial length was significantly associated with NTG (odds = 1.24, P = 0.002) and POAG (odds = 1.28, P = 0.001). The incidence of either POAG or NTG was significantly higher in patients with axial lengths ≥25.0 mm (odds = 2.29, P < 0.001, Fisher’s exact test). The age at the time of cataract surgery was weakly but significantly correlated negatively with the axial length (r = −0.24, P < 0.001, Pearson’s correlation coefficient test). Men had significantly longer axial lengths than women. Conclusions  Long axial lengths can be considered a risk factor for NTG and POAG, and patients with long axial lengths need to be carefully examined for glaucoma.     

Calibration of axial length measurements with the Zeiss IOLMaster

PURPOSE: To study the conditions for consistent axial length measurements with partial coherence interferometry (PCI) performed with the Zeiss IOLMaster. SETTING: University Eye Clinic, Aarhus, Denmark. METHODS: A consecutive, unselected series of 1289 cataractous eyes were measured with the optical technique of PCI according to the IOLMaster as well as with conventional (contact) A-scan ultrasound (US) for the measurement of axial length. For each PCI reading, the signal-to-noise ratio (SNR) was recorded and used for comparison with the US measurement. All patients had routine phacoemulsification with implantation of an intraocular lens (IOL). In 284 cases, the patients were reexamined 2 to 3 months after surgery and the axial length was again measured using PCI. The readings of the IOLMaster, which had been calibrated against immersion US from the manufacturer, were recalculated to represent the true optical length and used in the analysis of the consistency of the measurements. RESULTS: Not all readings obtainable with the IOLMaster were of good quality, and large differences with conventional US were found. The error between US and PCI decreased significantly with increasing SNR, showing a minimum error at an SNR value above 2.1. The SNR correlated significantly with the visual acuity with considerable scatter, however. Excluding readings with a poor quality (SNR <2.1), the postoperative PCI measurements showed a high correlation with the preoperative measurement (r = 0.99), showing a mean difference of 0.08 mm +/- 0.12 (SD). The difference was highly significantly different than zero (P < .001) and may be explained by a higher refractive index of the biological lens than assumed in the original calibration of the IOLMaster. CONCLUSIONS: The quality of the axial length readings of the IOLMaster was influenced by the SNR value. However, with proper SNR evaluation and recalibration of the PCI measurements, it is possible to achieve consistent PCI readings with little variation between preoperative and postoperative measurements. These results are promising for a higher accuracy of the IOL power calculation.     

Comparison axial length measurements from three biometric instruments in high myopia

AIM: To compare the axial lengths (ALs) measured with Lenstar, IOLMaster and A-scan contact ultrasound (Ultrasound) in normal and high myopia (HM). METHODS: Eighty-four normal eyes and 49 HM eyes were included. Three consecutive measurements were performed on each eye in the following order: Lenstar, IOLMaster, and Ultrasound. The repeatabilities of the AL measurements for each instrument were assessed by calculating the pooled coefficients of variation (CVs) of 18 eyes in each group. Comparisons between the HM and normal groups were made with independent sample t-tests. The inter-device agreements were evaluated with Bland-Altman analyses and paired two-tailed t-tests. RESULTS: For normal group, the CVs of the AL measurements taken with the Lenstar, IOLMaster and Ultrasound were 0.001%, 0.01% and 0.14%, respectively. The corresponding CVs for the HM group were 0.005%, 0.02% and 0.15%, respectively. There was significant difference between the Lenstar and the IOLMaster in normal group (P=0.031) but not in HM group (P=0.100). In the two groups, the Lenstar and the IOLMaster produced higher values than did the Ultrasound (all P<0.001). All three instruments exhibited good agreement in terms of AL values. For the intraocular lens (IOL) power calculation using SRK II formula, the Lenstar and the IOLMaster showed 0.5 D higher than Ultrasound in both groups (all P<0.001). No significant difference existed between the Lenstar and the IOLMaster for the IOL power calculation in both normal (P=0.474) and HM group (P=0.103). CONCLUSION: The three devices exhibited excellent intra-visit repeatabilities in the AL measurements. The AL and IOL power difference between partial coherence interferometry and ultrasound instruments should be noticed.     

青光眼术后眼轴长度改变的临床分析

目的 研究青光眼术后眼轴长度的改变,为临床高眼压状态下准确计算人工晶状体的屈光度数提供参考依据.方法 对19例青光眼行抗青光眼手术治疗后的眼压、眼轴长度的改变进行分析.结果 本组19例青光眼行抗青光眼手术治疗,术后平均眼压(15.20±2.66) rnm Hg与术前平均眼压(60.27±10.60) mmHg相比,差异有统计学意义(t=19.15,P=0.000);术后平均眼轴长度(21.86±0.80) mm与术前平均眼轴长度(22.28±0.81) mm相比,差异有统计学意义(t=49.19,P=0.000);手术前后平均眼压差为(45.07±10.26) mmHg,平均眼轴长度差为(0.42±0.04) mm.结论 高眼压引起眼轴长度增加,对于术前眼压不能控制的膨胀期白内障继发青光眼,测量眼轴时应考虑眼压因素对测量结果的影响,避免术后发生人工晶状体屈光误差.     

Repeatability of autorefraction and axial length measurements after laser in situ keratomileusis

PURPOSE: To assess the repeatability and agreement of refractive error measurements and the repeatability of axial length (AL) measurements in patients after laser in situ keratomileusis (LASIK). SETTING: The Ohio State University College of Optometry, Columbus, Ohio, USA. METHODS: Subjective refraction, autorefraction measurements with the Grand Seiko and Humphrey autorefractors, and AL measurements with the IOLMaster were completed for 40 previously myopic LASIK patients under noncycloplegic and cycloplegic conditions on 2 separate occasions. RESULTS: The mean difference between visits for axial length measurements was 0.008 mm +/- 0.04 (SD). The between visits repeatability for all refractive error measurements were <0.75 diopter (D). The mean difference between the subjective refraction and the Humphrey autorefractor for spherical equivalent was statistically significant under noncycloplegic conditions (-0.90 D, P<.0001) and cycloplegic conditions (-2.05 D, P<.0001). The mean difference between subjective refraction and Grand Seiko autorefraction measurements was not significant under noncycloplegic conditions (+0.05 D, 95% limits of agreement [LoA]=-0.99, 1.09; P=.52) conditions but was statistically significant, but not clinically relevant, under cycloplegic conditions (+0.17 D, 95% LoA=-0.73, 1.07; P=.03). CONCLUSIONS: Refractive error measurements after LASIK using the Grand Seiko autorefractor are reliable and agree well with subjective refraction measurements.     

IOLMaster700与IOLMaster500眼轴测量的一致性评价

目的 评价基于扫频OCT技术的IOLMaster700与IOLMaster 500对术后眼眼轴测量的一致性。设计 诊断试验。研究对象 单一眼科手术术后患者88例（109眼）。方法 根据眼科手术类型将患者分为准分子激光角膜屈光手术后、有晶状体眼人工晶状体植入术后、白内障摘除术后、白内障摘除人工晶状体植入术后、玻璃体切除术后、玻璃体切除硅油填充术后6组。采用IOLMaster700和IOLMaster500，由一名有经验的技术人员在同一时间测量各组患者的眼轴长度（AL）。采用配对样本t检验分析两种不同仪器测量结果的差异性，采用组内相关系数（ICC）和Bland-Altman分析进行一致性评价。主要指标 AL，ICC和Bland-Altman分析结果。结果 准分子激光角膜屈光手术后组和白内障摘除人工晶状体植入术后组中两种仪器所测得的AL差异具有统计学意义（P<0.001）。各组ICC为0.999~1.000，95%CI为0.998~1.000。Bland-Altman分析显示各组AL测量值差值95%一致限（LoA）最大绝对值为0.014~0.089。结论 IOLMaster 700与IOLMaster 500对眼科术后患者眼轴测量具有较好的一致性。     

Accuracy of ultrasound measurements of the axial length of the eye

Ultrasonic assessment of the axial length of the eye provides important baseline data for the calculation of the dioptric power of an artificial intraocular lens. The accuracy of ultrasonic biometry performed by an OPHTASCAN B apparatus is discussed based on evaluation of a group of repeated measurements of the axial length and depth of the anterior chamber in 592 bulbi.     

The ratio of lens thickness to axial length for biometric standardization in angle-closure glaucoma

Biometric measurements were made by ultrasonography in 44 left eyes of 44 patients with primary angle-closure glaucoma. We defined the ratio between the lens thickness and the axial length (lens thickness/axial length factor) as a representative and unifying unit for biometric assessment of the eye. This factor defined the relationship between the lens, iris, and cornea and thus the status of the angle. Lens thickness/axial length factor values were found to be age dependent and were greater than normal for most age groups with angle-closure glaucoma. The mean normal value was 1.91 +/- 0.44; the mean values for patients in different age groups with angle-closure glaucoma ranged from 1.87 +/- 0.11 to 2.39 +/- 0.17.     

先天性上睑下垂合并共同性外斜视的屈光状态及眼轴长度特征

目的：探究轻中度先天性上睑下垂合并共同性外斜视患者屈光状态及眼轴长度的特征。

方法：回顾性研究。收集2011-09/2021-02我院收治的轻中度先天性上睑下垂合并共同性外斜视(CPE)患者18例,轻中度单纯先天性上睑下垂(CP)患者19例和单纯共同性外斜视(CE)患者30例。比较三组患者屈光不正的患病率、弱视率、球镜度、散光度、等效球镜及眼轴长度。

结果：CPE组发生上睑下垂双眼发病共17例(94%),而CP组单眼发病共13例(69%),两组患者单双眼发病有显著差异(χ²=15.531,P<0.001)。三组间屈光参差及近视患病率差异有统计学意义(χ²_屈光参差=8.732,P_屈光参差=0.013; χ²_近视=6.047,P_近视=0.049)。CPE组屈光参差(χ²=8.072,P=0.004)及近视(χ²=4.555,P=0.033)患病率高于CP组,而CPE组与CE组之间屈光参差(χ²=0.559,P=0.454)及近视(χ²=0.055,P=0.815)患病率差异无统计学意义。CPE组球镜度(χ²=-31.143,P=0.002)、散光度(χ²=-23.434,P=0.028)、等效球镜度(χ²=-30.137,P=0.003)较CP组更偏向近视,眼轴(χ²=26.289,P=0.012)长于CP组,而与CE组无显著差异。儿童患者中CPE组的球镜较CE组更偏向近视(χ²=-16.831,P=0.016),等效球镜较CP组更偏向近视(χ²=-18.391,P=0.020)。

结论：轻中度先天性上睑下垂合并共同性外斜视可加剧轴性近视、近视性散光和屈光参差的发生发展,较单纯上睑下垂更为严重。故早期行全面眼科评估并及时手术治疗可能有助于防治CPE对视力造成的损害。     

不同手术方法治疗闭角型青光眼合并短眼轴的对比观察

目的:比较单纯小梁切除术和小梁切除术联合白内障超声乳化联合人工晶状体植入术(以下简称三联术)治疗闭角型青光眼合并短眼轴的疗效。方法:回顾分析2005-07/2009-01收住我院的闭角型青光眼合并短眼轴患者31例39眼。行单纯小梁切除术者25眼,行三联术者14眼。术后随访1～25(平均9.51±6.11)mo。结果:术后眼压:三联术者术后眼压平均(11.31±0.69)mmHg,手术前后有显著统计学差异(P<0.01);小梁切除术者术后平均(18.47±3.54)mmHg,手术前后差异有统计学意义(P<0.05);最佳矫正视力:三联术者术后均提高,≥0.3者占78%,小梁切除术者术后5眼视力不增反降,≥0.3者占32%,两者差异有显著性;UBM(超生生物显微镜)检查:小梁虹膜角(TIA)三联术者手术前后差异有显著性,小梁切除术者手术前后无显著性差异;中央前房深度(ACD):三联术术后平均为(3.22±0.53)mm,手术前后有显著性差异(P<0.01),小梁切除术后平均为(2.21±0.41)mm,比较差异无显著性;术后并发症:三联术术后并发症少,且均无需再手术纠正,小梁切除术者术后并发症较多,部分严重且持久,需再次手术。结论:小梁切除术联合白内障超声乳化联合人工晶状体植入术治疗闭角型青光眼合并短眼轴较单纯小梁切除术设计更合理,手术成功率高,疗效好,并发症少。     

Accuracy of axial length measurements from immersion B-scan ultrasonography in highly myopic eyes

AIM:To evaluate the accuracy of axial length (AL) measurements obtained from immersion B-scan ultrasonography (immersion B-scan) for intraocular lens (IOL) power calculation in patients with high myopia and cataracts.METHODS:Immersion B-scan, contact A-scan ultrasonography (contact A-scan), and the IOLMaster were used to preoperatively measure the AL in 102 eyes from 102 patients who underwent phacoemulsification and IOL implantation. Patients were divided into two groups according to the AL:one containing patients with 22 mm≤AL<26 mm(group A) and the other containing patients with AL≥26 mm (group B). The mean error (ME) was calculated from the difference between the AL measurement methods predicted refractive error and the actual postoperative refractive error.RESULTS:In group A, ALs measured by immersion B-scan (23.48±1.15) didn’t differ significantly from those measured by the IOLMaster (23.52±1.17) or from those by contact A-scan (23.38±1.20). In the same group, the standard deviation (SD) of the mean error (ME) of immersion B-scan (-0.090±0.397 D) didn’t differ significantly from those of IOLMaster (-0.095±0.411 D) and contact A-scan (-0.099±0.425 D). In group B, ALs measured by immersion B-scan (27.97±2.21 mm) didn’t differ significantly from those of the IOLMaster (27.86±2.18 mm), but longer than those measured by Contact A-scan (27.75±2.23 mm, P=0.009). In the same group, the standard deviation (SD) of the mean error (ME) of immersion B-scan (-0.635±0.157 D) didn’t differ significantly from those of the IOLMaster (-0.679±0.359 D), but differed significantly from those of contact A-scan (-0.953±1.713 D, P=0.028).CONCLUSION:Immersion B-scan exhibits measurement accuracy comparable to that of the IOLMaster, and is thus a good alternative in measuring AL in eyes with high myopia when the IOLMaster can’t be used, and it is more accurate than the contact A-scan.     

Effect of cycloplegia on axial length and anterior chamber depth measurements in children

Background: Cycloplegia has been shown to have no effect on axial length measurement made with the IOLMaster in adults. The current study aimed at evaluating the effect of cycloplegia on axial length and anterior chamber depth (ACD) measurements made with the IOLMaster and an ultrasonic biometer in children. Methods: Pre‐ and post‐cycloplegic axial length and ACD were measured with the IOLMaster followed by the Sonomed A‐5500 in 31 children aged from seven to 15 years by the same examiner. The 95% limits of agreement (LoA) were determined, if there were no significant correlations found between the mean differences and their means. Results: Seven subjects were excluded. Results from the remaining 24 subjects show that the effects of cycloplegia, instruments, and interaction between cycloplegia and instrument on axial length measurement were insignificant (repeated measure ANOVA F_1,23 < 2.19, p > 0.15). The 95% LoA in cycloplegia were better with the IOLMaster (‐0.04 to 0.04 mm) than with the Sonomed A‐5500 (‐0.13 to 0.14 mm). The 95% LoA between the two instruments were similar with and without cycloplegia (pre‐cycloplegia: ‐0.20 to 0.27 mm; post‐cycloplegia: ‐0.17 to 0.22 mm). There was no significant interaction between cycloplegia and instrument in ACD measurement (repeated measure ANOVA F_1,23= 0.85, p = 0.37), however, ACD was 0.05 to 0.06 mm shorter before cycloplegia (repeated measure ANOVA F_1,23= 44.70, p < 0.001) and was 0.06 to 0.08 shorter measured with the IOLMaster (repeated measure ANOVA F_1,23= 28.81, p < 0.001). Conclusion: Effects of cycloplegia on axial length measurement in children made with IOLMaster and Sonomed A‐5500 were insignificant. In contrast, ACD measurement was significantly affected by cycloplegia and different instruments.