Adjustment formulae to improve the correlation of white-to-white measurement with direct measurement of the ciliary sulcus diameter by ultrasound biomicroscopy.

PURPOSE: This study evaluates the correlation between horizontal white-to-white (WTW) distance using Caliper and Orbscan IIz with the ciliary sulcus diameter measured by high frequency ultrasound biomicroscopy (UBM) and presents an adjustment formula to improve the correlation. METHODS: We measured horizontal sulcus-to-sulcus (STS) dimension of 273 right eyes of 273 high myopic patients with 35 MHz UBM and horizontal WTW using Orbscan IIz and Caliper. Mean WTW diameter, differences, and the correlation of measurement methods were evaluated. RESULTS: The mean spherical equivalent was -8.79 ± 4.87 diopters. Mean horizontal STS dimension with UBM was 12.13 ± 0.45 mm (range, 10.81-13.42 mm). Mean WTW diameter in the Caliper method was 11.70 ± 0.40 mm (range, 10.6-12.8 mm) and 11.70 ± 0.40 mm (range, 10.5-13.1 mm) in the Orbscan method. Mean difference of UBM STS and WTW with Caliper was 0.48 ± 0.28 mm (range, -0.19 to 1.37 mm). Mean difference of UBM STS diameter and Orbscan WTW was 0.38 ± 0.31 mm (range, -0.64 to 1.29 mm). The Pearson correlations of WTW diameter measured by Caliper and Orbscan with UBM's STS diameter were 0.778 and 0.773, respectively. This difference diminished after adjustment. The 95% limit of agreement was almost the same in Caliper and Orbscan (-0.07 to 1.03 compared with -0.23 to 0.99). CONCLUSION: There is a significant difference in measurements between STS diameter using UBM and WTW diameter utilizing Caliper and Orbscan. This difference diminished after our recommended adjustment.

Multivariate Analysis to Predict the Horizontal Anterior Chamber Diameter from Other Anterior Chamber Parameters Using Scheimpflug Imaging: Is There a Better Method Than Adding a Fixed Constant?

PURPOSE: To evaluate the predictive association between the horizontal anterior chamber diameter (HACD) and other measurements using Scheimpflug imaging, and to assess whether a method superior to using fixed constants can be proposed. METHODS: This hospital-based study was performed in the Cornea and Refractive Surgery Services, New Medical Center (NMC) specialty hospital, Abu Dhabi. Initially, 100 candidates were included serially in the model building group (group1). All candidates underwent detailed evaluation and Scheimpflug imaging (CSO, Sirus, Italy). Subsequently, another 100 candidates were included serially in the validation group (group 2). Candidates in both groups underwent the same tests. RESULTS: In group 1, the mean HACD was 12.25 ± 0.48 mm. This measurement correlated significantly with the horizontal visible iris diameter (HVID), anterior chamber depth, angle (ACA), and volume (ACV) (r = 0.2-0.7). The overall regression equation was HACD = 5.62 + 0.01 × ACV + 0.45 × HVID - 0.013 × ACA (adjusted R2 = 0.66, p < 0.001). Situation-based equations derived from the outcomes of group 1 were tested in group 2. Equation A included all factors found significant during model-building, Equation B included only non-volumetric significant factors, and situation C only included the HVID. Equations D through F used direct substitution by HVID plus a constant to predict HACD (the constant was 0.0, 0.5, and 1.0 for Equations D, E, and F, respectively). The predicted HACD (pHACD) was within ±0.5 mm of the actual HACD (aHACD) in 93%, 88%, 87%, 83%, 69%, and 16% case for Equations A, B, C, D, E, and F, respectively. The mean prediction error was -0.14 ± 0.27 mm (p = 0.08), -0.15 ± 0.28 mm (p = 0.03), -0.18 ± 0.30 mm (p = 0.001), -0.18 ± 0.32 mm (p < 0.001), 0.33 ± 0.35 mm (p < 0.001), and 0.83 ± 0.35 mm (p < 0.001) for Equations A, B, C, D, E, and F, respectively. CONCLUSION: Regression equations using Scheimpflug-derived anterior chamber parameters may predict HACD to varying degrees, depending on the input parameters. Adding 0.5 or 1.0 mm to the corneal diameter (CD) to estimate the HACD is not recommended.

Spontaneous Scleral Perforation of an Anterior Chamber Intraocular Lens.

A routine eye examination of a 69-year-old man revealed a scleral perforation of one of the haptics of the anterior chamber intraocular lens (AC IOL) which had been implanted many years ago. The patient was asymptomatic with good visual acuity. His history was negative for any trauma, eye rubbing, topical corticosteroid use, or autoimmune disease. The horizontal and vertical white-to-white diameters of the cornea in the right eye were 11.5 and 10.5 mm, respectively. Anterior segment optical coherence tomography showed the anterior chamber length to be 12.28 mm horizontally and 10.63 mm vertically. The patient underwent an IOL exchange, and the length of the explanted AC IOL was measured to be 12 mm. We speculate that the AC IOL, which was vertically aligned, was oversized. This case demonstrates the need for proper sizing and positioning of an AC IOL. In complex cases where AC IOL may be used, measuring the horizontal and vertical lengths of the anterior chamber by anterior segment optical coherence tomography prior to surgery may be useful.

Discrepancy of sulcus-to-sulcus diameter and its relationship with white-to-white diameter in high myopic eyes / 中华实验眼科杂志

Background Horizontal sulcus-to-sulcus (STS) and white-to-white diameter are important parameters for designing the proper size of collamer implantable contact lens (ICL).Inappropriate size of ICL may induce the complications postoperatively.Several previous studies compare horizontal STS and white-to-white diameter in normal eyes have been reported,but seldom in high myopic eyes.Objective This study was to investigate the discrepancy of STS diameters in 4 axes and analyze the relationship between horizontal STS diameter and white-towhite diameter in high myopia eyes.Methods The STS diameters in 4 axes (45,90,135 and 180 degrees) and the white-to-white diameters were measured in 48 eyes of 26 high myopia patients using the 50 MHz ultrasound biomicroscopy (UBM),the Orbscan-Ⅱ topography system,and the IOL Master,respectively.The mean spherical was (-12.93±3.87) diopters (D) (-8 to-20 D).Statistical evaluation was performed using the one-way ANOVA for comparison of measurement.The agreement of three devices was assessed using the Bland and Altman method.Results The mean STS diameter at 45,90,135 and 180 degrees was (12.06±0.50) mm,(12.27±0.50)mm,(12.03±0.46) mm and (11.84±0.47)mm,respectively.The 90 degree STS was significantly larger than other STS diameters (all at P＜0.05).The 180 degrees STS was significantly shorter than other STS diameters (all at P＜0.05).However,there was no significant difference between 45 degree STS and 135 degree STS (P=0.817).The mean WTW was (11.56±0.40) mm with Orbscan Ⅱ z topography system and (11.98±0.41) mm with IOLMaster.The WTW measured with Orbscan Ⅱ z was significantly shorter than the 180 degrees STS (t =-4.384,P =0.000).The WTW measured with IOLMaster was significantly larger than the 180 degrees STS (t =2.368,P =0.000).Bland-Altman analysis showed not very well agreement for measurements of WTW,STS between Orbscan Ⅱz and UBM,IOLMaster and UBM,Orbscan Ⅱ z and IOLMaster,the width of 95％ confidence interval (CI) were-0.57 to 1.12 mm,-0.96 to 0.67 mm,-0.73 to-0.13 mm,respectively.Conclusions The STS diameters in 4 different axes are not identical with each other in high myopia eyes.The longest STS is in the vertical meridian,the shortest STS is in the horizontal meridian.The WTW diameter measured with both Orbscan Ⅱ z and IOLMaster are not precise for calculating the horizontal STS in high myopia eyes.Three instruments cannot be interchanged for calculating the size of ICL.

Effect of Orthokeratologic Lenses on Myopic Progression in Childhood

PURPOSE: The present study assessed the influence of overnight orthokeratology (ortho-k) on the myopic progression in Korean children and analyzed factors affecting myopic progression. METHODS: The ortho-k group was comprised of 31 patients satisfying the inclusion criteria for ortho-k. In the ortho-k group, spherical equivalent refractive error (SER) was measured at baseline, and after 2 weeks, 6 and 12 months. The control group was comprised of 31 patients who were matched according to age, gender, and baseline SER of the ortho-k subjects. RESULTS: In the ortho-k group, the mean +/- SD changes in SER from 2 weeks to 6 months, 6 to 12 months, and 2 weeks to 12 months were -0.17 +/- 0.50 D, -0.04 +/- 0.76 D, and -0.21 +/- 0.78 D, respectively. In the control group, the changes in SER from baseline to 6 months, 6 to 12 months, and baseline to 12 months were -0.38 +/- 0.42 D, -0.44 +/- 0.38 D, and -0.82 +/- 0.68 D, respectively. Significant differences were found between changes in SER from 6 to 12 months and from baseline to 12 months (p or = -0.5 D with the group of SER change < -0.5 D, numeric values of white-to-white diameters of the 2 groups were different, and a significant correlation was found between the range of SER change and the white-to-white diameter (Pearson's r = -0.471, p = 0.008). CONCLUSIONS: Ortho-k is effective for slowing myopic progression. The smaller the white-to-white diameter, the slower the myopic progression could be.

Measurement of White-to-White Diameter and Anterior Chamber Depth by Dual Scheimpflug Camera

PURPOSE: To estimate the horizontal and vertical white-to-white diameters (WTW) and anterior chamber depths (ACD) with a dual Scheimpflug camera (GALILEI(TM), Ziemer, Switzerland) and to compare the estimates measured by a measuring caliper and ultrasound biomicroscopy (UBM PlusTM, Paradigm Inc., Utah, USA) in normal subjects. METHODS: Forty-four eyes of 23 subjects were evaluated. Corneal diameter as measured by GALILEI was directly compared with the white-to-white diameter (WTW) measured by a caliper and the correlation with ciliary sulcus diameter (STS) by UBM was evaluated. The anterior chamber depth (ACD) as measured by GALILEI(TM) was compared with the estimates measured by UBM. RESULTS: The horizontal and vertical diameters of WTW by GALILEI were not significantly different from the measurements taken by calipers (p>0.05, p>0.05, respectively), and there were no correlations between the measurements (r=-0.074, p>0.05 at 180degrees r=0.297, p>0.05 at 90degrees, respectively). The estimates by GALILEI did not correlate with those measured with UBM (r=-0.006, p>0.05 at 180degrees r=-0.222, p>0.05 at 90degrees, respectively). However, the mean ACD by GALILEI was deeper than thatby UBM (p<0.01), and the measurements correlated strongly with each other (r=0.760; p<0.01). CONCLUSIONS: The mean WTW measured by GALILEI was not significantly different from the measurements taken by calipers and the measurements did not correlate with each other. There was also no correlation with the measurementsby GALILEI and UBM. ACD by GALILEI was measured to be deeper those that by UBM.