Asteroid hyalosis and axial length measurement using automated biometry

Accurate axial length measurements are needed before intraocular lens implantation in patients with asteroid hyalosis requiring cataract extraction. We suspected that falsely short axial length measurements may be obtained using automated A-scan biometry when we found an automated measurement of 15.90 mm in a patient with severe unilateral asteroid hyalosis. A manual biometry measurement of 21.90 mm was obtained for comparison; this was within 0.2 mm of the manual reading in the opposite uninvolved eye. A case-control study was performed on 20 unilateral asteroid hyalosis subjects using the uninvolved eye as the control, comparing automated biometry and manual A-scan biometry to assess the effect of asteroid hyalosis on automated biometry measurements. Five subjects (25%) with asteroid hyalosis had falsely short axial length measurements of more than 1.00 mm using automated biometry. This would result in more than 2.50 diopters of error in the implanted lens power. This case-control study demonstrates that falsely short axial length measurements may be obtained using automated biometry in patients with asteroid hyalosis, leading to significant error in intraocular lens power calculations.     

IOLMaster biometry: refractive results of 100 consecutive cases

AIMS: To study the refractive outcome of cataract surgery employing IOLMaster biometry data and to compare it with that of applanation ultrasonography in a prospective study of 100 eyes that underwent phacoemulsification with intraocular lens implantation. METHODS: The Holladay formula using IOLMaster data was employed for the prediction of implanted intraocular lenses (IOLs). One month after cataract surgery the refractive outcome was determined. Preoperative applanation ultrasonography data were used retrospectively to calculate the IOL prediction error. The two different biometry methods are compared. RESULTS: 100 patients, 75.42 (SD 7.58) years of age, underwent phacoemulsification with IOL implantation. The optical axial length obtained by the IOLMaster was significantly longer (p<0.001, Student's t test) than the axial length by applanation ultrasound, 23.36 (SD 0.85) mm v 22.89 (0.83) mm. The mean postoperative spherical equivalent was 0.00 (0.40) D and the mean prediction error -0.15 (0.38) D. The mean absolute prediction error was 0.29 (0.27) D. 96% of the eyes were within 1 D from the intended refraction and 93% achieved unaided visual acuity of 6/9 or better. The Holladay formula performed better than the SRK/T, SRK II, and Hoffer Q formulas. Applanation ultrasonography after optimisation of the surgeon factor yielded a greater absolute prediction error than the optimised IOLMaster biometry, 0.41 (0.38) D v 0.25 (0.27) D, with 93% of the eyes within 1 D from the predicted refraction. CONCLUSION: IOLMaster optical biometry improves the refractive results of selected cataract surgery patients and is more accurate than applanation ultrasound biometry.     

Laser interference biometry versus ultrasound biometry in certain clinical conditions

Purpose To compare laser interference biometry (LIB) with conventional ultrasound biometry in certain clinical conditions such as globe deformities, eccentric fixation, retinal detachment, macular edema or silicone oil-filled eyes.Setting Department of Ophthalmology, Würzburg University Eye Hospital, Germany.Methods We evaluated all patients who came to our university hospital for axial length measurement with our routine immersion biometry system (Grieshaber Biometry System) and compared the results with those obtained using the Zeiss IOLMaster of Carl Zeiss Jena, the commercially available LIB device.Results Selected case reports demonstrate the advantages and disadvantages of LIB. Advantages of LIB were found in patients with asymmetrically shaped globes, eccentric fixation, silicone oil-filled eyes and a fearful/nervous disposition. Disadvantages of the system were revealed in cases of retinal detachment, severe opacities along the visual axis and poor patient cooperation.Conclusion We showed that LIB is a valuable addition to the choice of biometric devices, when used with medical understanding.Presented in part at the Annual Meeting of the American Society of Cataract and Refractive Surgery (ASCRS) 2000 during the Optical Biometry Course of the European User Group for Laser Interference Biometry (EULIB)     

Ultrasound biometry in childhood

Within the last 18 months the authors have measured, in cases of juvenile cataract seen by them, the axial length of the eye and other parameters. As a control group, children from the authors' squint clinic, with various refractive errors, were examined. With the data thus gathered, correlation and regression analyses were performed, postoperative refraction values were calculated, and eye growth in phakic eyes was compared with that in aphakic eyes. Regression formulas were established which enabled the authors to calculate eye length at a given age, to determine the postoperative refraction of their juvenile cataract patients with great accuracy, and, so far, to prove that there is no significant difference between phakic and aphakic eyes as regards growth.     

Ultrasound biomicroscopic measurement of anterior chamber biometry between before and after pupil dilation in children

PURPOSE: To evaluate anterior chamber biometry of the eyes of normal children using ultrasound biomicroscopy (UBM) and to evaluate the differences in biometry between children and adults, and before and after pupil dilation in children. METHODS: Anterior chamber depth (ACD) and trabecular-iris angle (TIA) were measured in 94 normal children and 15 normal adults using UBM. Before and after pupil dilation were measured in 42 children with emmetropic and hyperopic eyes. RESULTS: In 66 emmetropic children, ACD and TIA were 2.93+/-0.18 mm and 34.42+/-4.02 degrees, respectively. In 28 hyperopic children, ACD and TIA were 2.92+/-0.21 mm and 35.05+/-4.42 degrees, respectively. There was no significant difference in anterior chamber biometry associated with the refraction. ACD did not differ between children and adults, but TIA in children was wider than in adults. There was no significant difference in ACD or TIA before versus after pupil dilation in any case. CONCLUSIONS: Anterior chamber biometry in children showed no differences before and after pupil dilation. Also, there was no difference in ACD of children as compared to adults; however, TIA in children was significantly wider than in adults.     

National biometry audit

PURPOSE: To determine compliance with the Royal College of Ophthalmologists' (RCOphth) biometry guidelines. METHOD: A structured telephone questionnaire of individuals who perform biometry in all eye departments in the United Kingdom (UK). RESULTS: A biometrist was interviewed in 107 of the UK's 178 eye departments. Nurses alone run the biometry service in 58% of departments, orthoptists alone in 13%, junior doctors alone in 6%, optometrists alone in 3%, and a combination of staff in 20%. Of the staff interviewed, 37% had been on external biometry training courses.One intraocular lens (IOL) calculation formula was used for all eyes in 61% of departments with 17% using the obsolete SRK II formula, 36% of departments used two or more formulae and only 4% adhered to the RCOphth guidelines to use Hoffer Q in eyes with axial lengths <22.0 mm, an average of all three formulae in eyes between 22.0 and 24.5 mm, Holladay in eyes between 24.6 and 26.0 mm, and SRK/T in eyes >26.0 mm.Audit of refractive results was claimed by 71% of units but in only 17 (16%) did the biometrist know the percentage of eyes with a prediction error 相似文献   

Comparison of refractive outcomes using immersion ultrasound biometry and IOLMaster biometry

Background:  The IOLMaster determines axial length using partial coherence interferometry. This study was designed to compare the refractive outcomes of patients who had been measured preoperatively by both immersion ultrasound and IOLMaster biometry.
Methods:  Patients were recruited from those who had undergone cataract surgery during the preceding 12 months by one surgeon at The Queen Elizabeth Hospital (55 eyes from 55 patients). Each patient underwent measurement of axial length by immersion ultrasound and the IOLMaster. Target refraction was determined using an SRK-T formula and the amount that this differed postoperative refraction was calculated for immersion ultrasound and the IOLMaster. These results were then compared.
Results:  Eyes measured longer by the IOLMaster method compared with immersion ultrasound (23.37 ± 0.87 vs. 23.25 ± 0.90 mm, t  = 4.83; P  < 0.0001). However anterior chamber depth was the similar. Postoperatively, final refractive outcome was 0.01 ± 0.63 dioptres (D) more hypermetropic than the target refraction when using the IOLMaster compared with 0.25 ± 0.73 D more myopic when using immersion ultrasound ( t  = 3.83; P  < 0.0001). Seventy-five per cent of patients were within 0.5 D of target refraction and 93% were within 1.0 D when the IOLMaster was used, compared with 49% and 85% within 0.5 and 1.0 D respectively when using immersion ultrasound (χ² = 8.34; P  = 0.04).
Conclusions:  Biometry performed using the IOLMaster produces a more predictable refractive outcome than immersion ultrasound, with patients' spherical equivalent more likely to be closer to their target refraction.     

Lenstar 与 A 超测量前房深度及晶状体厚度的比较

目的比较 Lenstar LS900光学生物测量仪与 A 超测量(ACD)、晶状体厚度(LT)的差异,以评价 Len-star 测量参数的准确性,为其临床应用提供依据.方法对31例(35只眼)白内障患者分别应用 Lenstar 与 A 超测量 ACD、LT,测量数据之间的差异采用配对 t 检验,一致性采用 Bland-Altamn 统计分析.结果 Lenstar 测量 ACD 为(3.047±0.384)mm,A 超为(2.853±0.397) mm,差异有统计学意义( t =2.242, P <0.05),一致性较差.测量 LT Lenstar 为(4.546±0.370) mm,A 超为(4.631±0.411) mm,差异无统计学意义( t =0.912, P ﹥0.05),一致性较差.结论 Lenstar 与 A 超的测量结果存在一定差异,在临床中应注意仪器之间的差异.     

Ocular biometry using Orbscan

Orbscan is a recent optical device that combines the Placido disk of the videokeratoscope and a scanning slit. The scanning slit measures the elevation of both the corneal surface (anterior and posterior) and the anterior iris-lens surface. Biometric measures of the anterior segment such as corneal thickness, anterior chamber depth, corneal diameter, and iridocorneal angle are obtained using spatial coordinates of various ocular surfaces. Orbscan is not only a corneal topograph but a versatile device capable of measuring the biometry of the anterior segment of the eye.     

散瞳对白内障合并高度近视患者眼球生物学测量和IOL度数计算的影响

目的:研究散瞳对白内障合并高度近视患者眼球生物学测量和人工晶状体(IOL)度数计算结果的影响及与正常眼轴白内障患者的区别。方法:采用IOL Master测量白内障合并高度近视患者22例34眼(A组)和正常眼轴白内障患者23例39眼(B组)散瞳前后眼轴(AL)、角膜曲率(K,包括K1和K2)、前房深度(ACD),并用SRK-T、Haigis公式计算IOL度数。结果:散瞳后A组ACD(3.84±0.58mm)较散瞳前(3.61±0.35mm)增加(P<0.01),B组ACD(3.30±0.70mm)也较散瞳前(3.13±0.63mm)增加(P<0.01),两组散瞳前后ACD差值无差异(P>0.05)。两组散瞳后AL、K测量值与散瞳前相比均未见明显差异(P>0.05)。散瞳前后两组采用SRK-T、Haigis公式计算IOL度数均无明显差异(P>0.05),但散瞳前后计算的IOL度数差异≥1D占比A组分别为15%、27%,B组分别为3%、5%。结论:散瞳引起白内障合并高度近视患者前房深度明显增加,与对正常眼轴白内障患者的影响相比无区别。散瞳对角膜曲率和眼轴测量没有影响。散瞳不影响用SRK-T、Haigis两种公式计算白内障合并高度近视患者IOL度数的计算结果,但相对正常眼轴患者出现大度数差别的几率较大,故建议在未散瞳状态下进行测量和计算以尽量减少误差。