Partial Coherence Laser Interferometry Research Articles

Correlations between Magnitude of Refractive Error and Other Optical Components in Korean Myopes

PurposeWe evaluated ocular optical components and their interrelationships in myopic Korean patients.MethodsIn this prospective observational study, 1,011 consecutive patients were recruited from a refractive surgery clinic. The best-corrected visual acuity was >20 / 20 in all patients. The refractive error, axial length (AL), anterior chamber depth (ACD), lens thickness (LT), and vitreous chamber depth (VCD) were measured by an autorefractor and partial coherence laser interferometry (IOL Master). Central corneal thickness (CCT) was measured by ORBscan II topography.ResultsThe refractive errors had a positive correlation with LT but negative correlations with AL, ACD, VCD, and CCT. As the axial length increased, the ACD, VCD, and CCT increased but the LT decreased. The CCT had a positive correlation with gender, refractive errors, ACD, VCD, and AL but no correlation with age. The mean CCT was increased in proportion to the increase in AL.ConclusionsIn myopic Korean patients, as axial elongation progressed, the VCD and ACD deepened and the CCT thickened but the LT decreased. The CCT had a positive correlation with the degree of myopia and the AL.

Longitudinal Changes of Axial Length and Height Are Associated and Concomitant in Children

To examine the association between the longitudinal changes of axial length (AL) and height in Chinese children. The study participants were recruited from the Guangzhou Twin Registry. AL and height were measured every year from 2006 to 2008. AL was measured using partial coherence laser interferometry. Height was measured with the participants standing without shoes. Bivariate correlation coefficients and a multivariate generalized regression model were used to calculate the association between the changes of AL and height. Data from the first-born twins were selected to present the results: The right eye was arbitrarily selected to represent AL of the specific individual. Mean annual increases of AL and height were 0.22 (SD, 0.17) mm and 3.93 (SD, 3.02) cm, respectively. Correlations between AL and height were 0.47 (95% CI, 0.40-0.52) in 2006. The correlation between AL at 2006 and height at 2008 was 0.44 (95% CI, 0.37-0.51); the correlation between AL at 2008 and height at 2006 was 0.38 (95% CI, 0.32-0.45). These cross-trait cross-time correlation coefficients remained statistically significant after adjusting for age and sex. Plotting the changes of AL and height suggested that the changes of AL and height with age were concomitant; greater changes were observed in younger children. The association between AL and height in cross-sectional analysis and longitudinal changes may suggest common pathways for the development of eye size and body size in children.

Posterior capsule opacification and capsular bag performance of a microincision intraocular lens

To assess the axial stability and posterior capsule opacification (PCO)-inhibiting efficacy of a microincision hydrophilic intraocular lens (IOL) (Idea 613 XC) and a standard hydrophobic open-loop acrylic IOL (Acrysof SA60AT). Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom. Clinical trial. Patients with bilateral cataract received a microincision cataract surgery (MICS) IOL in 1 eye and a small-incision cataract surgery (SICS) IOL in the contralateral eye. Follow-up examinations were performed immediately after surgery and postoperatively at 1 week and 3 and 24 months. Posterior capsule opacification was assessed using retroillumination photography. Anterior chamber depth (ACD) was measured using partial coherence laser interferometry, and IOL tilt and decentration were measured using a Purkinje meter. Seventy eyes (35 patients) were enrolled. The mean ACD at 3 months was 4.91 mm ± 0.26 (SD) in the MICS group and 4.60 ± 0.23 mm in the SICS group. The anterior IOL shift over the first 3 months was slightly smaller with the MICS IOL (81 μm) than with the SICS IOL (254 μm). The mean ACD was 0.377 ± 178 μm deeper with the MICS IOL (P<.01, paired t test). Two years postoperatively, the amount of regeneratory PCO was higher with the MICS IOL than with the SICS IOL (image analysis software score 2.6 versus 1.9; P=.005). Two years after surgery, the PCO rate was slightly higher with the MICS IOL. The 2 IOLs had similar performance in terms of axial stability, decentration, and tilt. No author has a financial or proprietary interest in any material or method mentioned. Additional disclosures are found in the footnotes.

Shared Genetic Determinants of Axial Length and Height in Children

To describe the association between axial length (AL) and height and to estimate the extent to which shared genetic or environmental factors influence this covariance. Study participants were recruited from the Guangzhou Twin Registry. Axial length was measured using partial coherence laser interferometry. Height was measured with the participants standing without shoes. We computed twin pairwise correlations and cross-twin cross-trait correlations between AL and height for monozygotic and dizygotic twins and performed model-fitting analyses using a multivariate Cholesky model. The right eye was arbitrarily selected to represent AL of participants. Five hundred sixty-five twin pairs (359 monozygotic and 206 dizygotic) aged 7 to 15 years were available for analysis. Phenotypic correlation between AL and height was 0.46 but decreased to 0.19 after adjusting for age, sex, and age × sex interaction. Bivariate Cholesky model-fitting analyses revealed that 89% of phenotypic correlation was due to shared genetic factors and 11% was due to shared random environmental factors, which includes measurement error. Covariance of AL and height is largely attributable to shared genes. Given that AL is a key determinant of myopia, further work is needed to confirm gene sharing between myopia and stature.

Refractive error, axial length and anterior chamber depth of the eye in British adults: the EPIC-Norfolk Eye Study

PurposeTo describe the distribution, and demographic and socioeconomic correlates of refractive error and related ocular biometry in an older British population.MethodsRefractive error was measured using an auto-refractor without cycloplegia. Pseudophakic...

Distribution of Axial Length and Ocular Biometry Measured Using Partial Coherence Laser Interferometry (IOL Master) in an Older White Population

We aimed to describe norms for the distribution of axial length (AL) and other ocular biometric parameters in an older Caucasian population, measured using partial coherence laser interferometry (Zeiss IOL Master; Carl Zeiss AG, Oberkochen, Germany), a technique now routinely used in measuring AL before cataract surgery. We also aimed to assess age and gender relationships with these parameters and their correlations with spherical equivalent refraction (SER). Cross-sectional analysis of the Blue Mountains Eye Study (BMES) cohort at the examinations (10-year follow-up examination). From 2002 to 2004, 1952 persons (76% of surviving baseline BMES participants) aged 59 years or older had ocular biometry measured at the 10-year examinations. Spherical equivalent refraction was calculated as the sum of sphere +0.5 cylinder power, after protocol refraction. Measurements of AL, corneal curvature (K1), anterior chamber depth (ACD), and corneal diameter (WTW) were performed using the IOL Master. Only right phakic eyes (n = 1335) with biometry data were included. Axial length distribution. Mean AL was 23.44 mm (95% confidence interval [CI], 23.38-23.50) and was greater in men, 23.76 mm (CI, 23.68-23.84), than in women, 23.19 mm (CI, 23.11-23.27). The mean K1, ACD, and WTW were 43.42 diopters (D), 3.10 mm, and 12.06 mm, respectively. The AL and ACD distributions were both positively skewed and peaked, whereas the WTW and K1 distributions were near normal. From age 59 years or older, a mean reduction in AL with age was observed (P for trend = 0.005), 0.12 mm per decade (P = 0.0176) in women but only 0.02 mm per decade (P = 0.6319) in men. Mean SER was 0.58 D, and the distribution was peaked with a negative skew. The SER was negatively correlated with both AL (beta coefficient -0.688) and ACD (beta coefficient -0.222), but not with K1 or WTW. These data provide normative values in the older general population for AL measured using the IOL Master. Axial length distribution was peaked and skewed, suggesting an active modulation process.

Accuracy and reproducibility of axial length measurement in eyes with silicone oil endotamponade

Aim:To assess the accuracy and signal quality of axial length measurements by partial coherence laser interferometry (PCI) for optical biometry in eyes with conventional silicone oil (SO) or heavy silicone...

Corneal Biomechanical Changes in Diabetes Mellitus and Their Influence on Intraocular Pressure Measurements

To investigate possible corneal biomechanical changes in patients with diabetes mellitus and understand the influence of such changes on intraocular pressure measurements. The study group was composed of 120 eyes from 61 healthy control subjects and 81 eyes from 43 diabetic subjects. IOP was measured first with an ocular response analyzer (ORA) and subsequently with a Goldmann applanation tonometer (GAT). Central corneal thickness (CCT) was measured with an ultrasonic pachymeter attached to the ORA. Axial length (AL), anterior chamber depth (ACD), and keratometry readings were acquired with partial coherence laser interferometry during the same visit before all IOP and CCT determinations were made. Corneal hysteresis (CH) was found to be significantly lower in diabetic patients when compared with healthy control subjects (9.51 +/- 1.82 mm Hg vs. 10.41 +/- 1.66 mm Hg, P < 0.0001). There was no significant difference in terms of corneal resistance factor (CRF; P = 0.8). Mean CCT, GAT IOP, Goldmann-correlated IOP (IOPg), and corneal-compensated IOP (IOPcc) were significantly higher in diabetic patients than in healthy control subjects (P = 0.01 for CCT, P < 0.0001 for GAT IOP, IOPg, and IOPcc). Diabetes affects corneal biomechanics and results in lower CH values than those in healthy control subjects, which may cause clinically relevant high IOP measurements independent of CCT.

Association of Age, Stature, and Education With Ocular Dimensions in an Older White Population

To describe ocular biometry relationships in older white adults. Ocular dimensions were measured with partial coherence laser interferometry in 1968 persons (aged 58-100 years, 59% female) seen at the fourth examination of the Beaver Dam Eye Study. Generalized estimating equations-modeled associations of age, sex, height, and education with ocular dimensions: axial length, corneal curvature radius, and anterior chamber depth. The mean axial length was 23.69 mm; mean corneal curvature radius was 7.70 mm; and mean anterior chamber depth was 3.11 mm. Participants younger than 65 years had larger eyes (longer axial length, greater corneal curvature radius, and deeper anterior chamber depth) than persons aged 75 years or older. Mean axial length was 23.86 mm, 23.66 mm, and 23.55 mm in people aged 64 years and younger, 65 to 74 years, and 75 years or older, respectively. Generally, larger eyes were observed in men (vs women) and in taller (>178 vs <or=158 cm) and more educated (>16 vs <12 years) persons. Adjustment for height accounted for all sex differences. Age differences in axial length were attenuated (P = .06) after adjustment for both height and education. In this older white population, age and sex variations in ocular dimensions are partially explained by differences in stature and education.

Anterior chamber depth and change in axial intraocular lens position after cataract surgery with primary posterior capsulorhexis and posterior optic buttonholing

To compare axial position changes of the intraocular lens (IOL) by measuring anterior chamber depth (ACD) after small-incision cataract surgery with primary posterior continuous curvilinear capsulorhexis (PPCCC) and posterior optic buttonholing (POBH) of the IOL and after conventional cataract surgery with phacoemulsification and in-the-bag IOL implantation. Department of Ophthalmology, Medical University of Vienna, Austria. This prospective comparative study comprised 23 patients (46 eyes) with age-related cataract who had bilateral cataract surgery and implantation of an acrylic IOL (YA-60BB, Hoya). In randomized order, cataract surgery with PPCCC and POBH of the IOL was performed in 1 eye of each patient. In the fellow eyes, conventional phacoemulsification cataract surgery with in-the-bag IOL implantation was performed. The ACD was measured 1 to 2, 6, and 24 hours as well as 7 and 30 days postoperatively using high-resolution partial coherence laser interferometry. A baseline measurement was taken preoperatively in all patients. Ten patients completed 10 to 12 months of follow-up. Postoperatively, the axial IOL position was stable in eyes with PPCCC-POBH (P>.05). In contrast, a significant axial shift of the IOL in the anterior direction was observed in control eyes with in-the-bag IOL implantation (P<.001). The resulting refractive shift was significantly higher in control eyes than in eyes with PPCCC-POBH (P<.001). Combined PPCCC and POBH for cataract surgery significantly reduced postoperative anterior movement of the IOL.

Non-invasive biometric assessment of ocular rigidity in glaucoma patients and controls

To determine in vivo whether a pharmacologically induced change in intraocular pressure (IOP) leads to measurable changes in axial eye length and whether there is a difference between glaucoma patients and control subjects. 42 subjects (19 patients with primary open angle glaucoma and 23 control patients matched for age and gender) underwent axial eye length measurement using partial coherence laser interferometry and measurement of IOP using dynamic contour tonometry before and 2 h after oral intake of 500 mg acetazolamide. Student's t-test was used to compare differences in the means. An identical drop in IOP was induced in both the glaucoma (mean+/-SEM: 2.90+/-0.44 mmHg, n=19) and the control group (mean+/-SEM: 3.17+/-0.32 mmHg, n=23). The change in axial eye length was significantly smaller (P=0.026) in the glaucoma group (mean+/-SEM: -14.2+/-3.2 microm, n=19) compared with the control group (mean+/-SEM: -23.0+/-2.98 microm, n=23). Our results strongly suggest that the ocular rigidity is increased in patients with established glaucoma in comparison to control subjects. Ocular rigidity could play a role in the pathogenesis and pathophysiology of glaucoma. Determination of ocular rigidity could be helpful in detection of glaucoma.

Axial Length and Anterior Chamber Depth by IOL-Master, A-scan according to Viscosity of Silicone Oil

Purpose: To evaluate differences between partial coherence laser interferometry (IOL-Master, Zeiss) and A-scan measurement of axial length and anterior chamber depth in silicone oil-filled eyes according to viscosity. Methods: Using IOL-Master and A-scan, axial length and anterior chamber depth in silicone oil-filled eyes (n=54) and normal eyes (control, n=54) were measured and analyzed. In silicone oil-filled eyes, calculated axial lengths by A-scan using conversion factors, axial length multiplied by 0.71, and vitreous cavity multiplied by 0.64 (classic method) were compared with those calculated by IOL-Master. Anterior chamber depths were also analyzed., and axial lengths and anterior chamber depths were compared according to the viscosities of silicone oil for measurement by A-scan. Results: Axial length and anterior chamber depth using IOL-Master were shorter than those using A-scan by 9.45±1.81 mm (p

Heritability of Anterior Chamber Depth as an Intermediate Phenotype of Angle-Closure in Chinese: The Guangzhou Twin Eye Study

To assess the heritability of anterior chamber depth (ACD) and relative anterior chamber depth (ACD/axial length, rACD) in Chinese in a classic twin study. Twins aged 7 to 15 years living in two local districts were recruited from the Guangzhou Twin Registry. Anterior chamber depth and axial length were measured by partial coherence laser interferometry. Zygosity in all same-sex twin pairs was confirmed by genotyping with 16 polymorphic markers. The phenotypes of the right eyes were used in analysis. Heritability was assessed by structural variance component genetic modeling. In total, 1126 twin participants were available for analysis, including 357 monozygotic (MZ) and 206 dizygotic (DZ) twin pairs. ACD increased with age (0.036 mm per year, P < 0.001) and 0.09 mm shallower in the girls than in the boys (P < 0.001). Age- and sex-adjusted intraclass correlation coefficients (ICCs) for ACD were 0.92 for the MZ and 0.50 for the DZ twins; those for rACD were 0.89 for the MZ and 0.52 for the DZ twins. The best-fitting model yielded 90.1% (95% CI: 88.2%-91.7%) of additive genetic and 9.9% (95% CI: 8.3%-11.8%) of unique environmental effects for ACD and 89.2% (95% CI: 87.1%-90.9%) of additive genetic and 10.8% (95% CI: 9.1%-12.9%) of unique environmental effects for rACD. Additive genetic effects appear to be the major contributor to the variation of ACD and rACD in Chinese population. High heritability remained even when the data were corrected for the influence of myopia.

Myopic proptosis and the associated changes in axial components of the eye

To investigate the correlation between proptosis and changes of axial components in myopic eyes. One hundred and eighty-nine myopic and emmetropic eyes were included. There are one hundred and eighty-three right eyes and six left eyes. Based on axial length (AL), subjects were divided into three groups: low-myopia & emmetropia group, moderate myopia group, high myopia group. Refraction of the eye (SE, spherical equivalent) was measured by retinoscopy examination under mydriasis. Proptosis was measured by Exophthalmometer (K-0161 Hertel-Type). Axial components including axial length and corneal curvature and were measured by partial coherence laser interferometry (IOL-master). The correlation in results among proptosis, axial components, and refraction was evaluated. The proptosis in high myopia group was bigger than in the other groups (P < 0.01). The proptosis in moderate myopia group was bigger than in low-myopia and emmetropia group (P < 0.01). The axial length was shorter than 25 mm in low-myopia and emmetropia group, from 25.00 to 27.00 mm in moderate myopia group and equal or longer than 27 mm in high myopia group. There was an increasing trend in proptosis [ranging from (14.66 +/- 1.94) mm, (16.16 +/- 1.40) mm to (18.30 +/- 1.63) mm] and axial length [ranging from (23.54 +/- 0.73) mm, (25.77 +/- 0.53) mm to (30.08 +/- 2.09) mm] among the three groups, the order of groups in the ranging was from low-myopia and emmetropia group, moderate myopia group to high myopia group. There was a highly significant correlation between proptosis and AL (R(2) = 0.990, F = 18 450.30, P < 0.01). Refraction results in low-myopia and emmetropia group, moderate myopia group and high myopia group were (-0.76 +/- 1.29) diopters (D), (-5.33 +/- 2.37) diopters (D) and (-15.92 +/- 5.12) diopters (D) respectively. There was a moderate correlation between proptosis and SE (R(2) = 0.500, F = 187.05, P < 0.01). There was a highly significant correlation between axial length and refraction (R(2) = 0.892, F = 1537.83, P < 0.01). Myopic proptosis increases with the increasing AL and SE of the eye. The eyeball tends to expand backward and proptosis forward with the increasing AL and the proptosis forward appears to be more obvious.

Signal quality of biometry in silicone oil–filled eyes using partial coherence laser interferometry

To assess the practical feasibility and signal quality of axial length measurements by partial coherence laser interferometry in silicone oil-filled eyes with previous complicated vitreoretinal surgery. Department of Ophthalmology, University Cologne, Cologne, Germany. Using a Zeiss IOLMaster, axial length measurements and signal-to-noise ratios of optical biometry in silicone oil-filled eyes (n=45) and contralateral eyes without tamponade (n=41) were analyzed. Axial length measurements with signal-to-noise ratio > or =2 were feasible in 41 of 45 silicone oil-filled eyes (91%) and 37 of 41 eyes without tamponade (90%). Cataract, central retinal detachment, vitreous hemorrhage, and emulsified oil droplets attached to the intraocular lens were reasons for failure of partial coherence laser interferometry. The signal-to-noise ratio of the first 2 measurements was significantly smaller (P=.04) in silicone-filled eyes (4.4 +/- 2.0) than in eyes without tamponade (5.5 +/- 3.0). Axial lengths of the oil-filled eye and the contralateral eye showed a significant intraindividual correlation (P<.0001, Spearman r=0.84). Partial coherence laser interferometry shows good clinical practicability in silicone oil-filled eyes with previous complicated vitreoretinal surgery. Further studies are needed to assess the reliability of these measurements with regard to postoperative refraction after combined oil removal and cataract surgery.

National Biometry Audit II

To determine the change in compliance with the Royal College of Ophthalmologists biometry guidelines since the last National Audit 2 years ago and in particular to quantify the adoption of modern methods of axial length measurement and customization of A constants. A structured telephone questionnaire of individuals who perform biometry in all eye departments in the United Kingdom. A biometrist was interviewed in 94 of the 178 United Kingdom Ophthalmology departments. Compared with 2 years ago, nurses alone perform biometry more frequently (67 vs 51%) and junior doctors less frequently (9 vs 15%). More biometrists now attend external training courses (45 vs 37%). The Royal College of Ophthalmologists recommended intraocular lens calculation formulae (SRK-T, Hoffer Q, and Holladay) are used more commonly (30 and 15%) and audit of prediction error is being performed more frequently (78 vs 71%). The routine use of a partial coherence laser interferometry has increased from 35 to 61% in United Kingdom Ophthalmology departments. Currently, only one United Kingdom department is routinely using immersion ultrasound biometry. 'A' constants are customized in 47% of departments. Over the last 2 years, there has been improved implementation of the Royal College of Ophthalmologists guidelines on biometry. It is essential that the Royal College of Ophthalmologists guidelines are updated to include current best practice of routine use of partial coherence laser interferometry or immersion biometry and customization of A constants. A benchmark standard of 85-90% of patients achieving a final postoperative refraction within 1 dioptre of the predicted should be established.

Axial Length Scanning: Laser Interferometry Versus Ultrasound Biometry

In cataractous patients, the authors measured the axial length (AL) using both partial coherence laser interferometry (PCLI) and ultrasound biometry (UB), the latter performed by both an experienced and inexperienced operator. Both sets of AL measurements were compared to theoretical (calculated) AL values. AL measurements obtained with PCLI are as reliable as those recorded by an experienced operator using UB.

Effect of haptic design on change in axial lens position after cataract surgery

Purpose: To compare the postoperative changes in anterior chamber depth (ACD) between single-piece and multipiece AcrySof ® intraocular lenses (IOLs) (Alcon Laboratories, Inc.) and their effect on the postoperative refractive shift. Setting: Department of Ophthalmology, University of Vienna, Vienna, Austria. Methods: This prospective randomized bilateral study with intraindividual comparison comprised 104 eyes of 52 consecutive patients with age-related cataract. All patients had standardized cataract surgery with a temporal self-sealing incision, phacoemulsification, and IOL implantation in the capsular bag. The first 30 patients received a single-piece, 5.5 mm optic IOL (AcrySof SA30) in 1 eye and a multipiece IOL (AcrySof MA30) in the other eye. Another 22 patients received the corresponding 6.0 mm optic models (AcrySof SA60 and AcrySof MA60, respectively). Anterior chamber depth measurements and evaluation of the change in ACD during the first 6 postoperative months were performed using partial coherence laser interferometry. The amount of change in capsulorhexis size during the first 6 postoperative months was assessed using standardized retroillumination photographs. Results: Single-piece IOLs shifted significantly less postoperatively than multipiece IOLs. The multipiece IOLs shifted forward, especially from 1 day to 1 month. The change in the capsulorhexis area was similar between IOL types. Conclusions: Single-piece AcrySof IOLs shifted minimally after the first postoperative day; therefore, the prescription for spectacles in eyes with this IOL can be obtained soon after surgery.