PURPOSE: The purpose of this study is to investigate the effect of the suction time in forming the corneal flap with microkeratome on the corneal flap thickness. METHODS: Thirty porcine eyes were randomly assigned into 3 groups according to suction duration: group 1(10 sec), group 2(35 sec) and group 3(60 sec). The Hansatome microkeratome with 160 plate and a suction ring with 8.5mm diameter were used to create corneal flap. The thickness of central cornea was measured with automated ultrasound pachymeter before the procedure. And after making the flap, the remained corneal thickness was measured with the same method. Then, the difference between the two values was thought to be the corneal flap thickness. RESULTS: The mean corneal flap thickness in group1, 2, and 3 were 91.0+/-24.1 micromiter, 110.1+/-8.9 mu m and 127.2+/-6.1 mu m, respectively. The difference was significant among the three groups(p=0.010), and the longer suction duration made the flap thicker. CONCLUSIONS: These results suggest that in forming the corneal flap with microkeratome, the suction duration has an effect on the corneal flap thickness and an increase of suction duration makes the flap thicker in porcine eyes.
Cornea ; Suction* ; Ultrasonography

PURPOSE: To demonstrate the capability of anterior segment optical coherence tomography (OCT), to evaluate central corneal thickness (CCT) and to compare the results with those by Orbscan II and standard ultrasound (US) pachymetry. METHODS: One examiner measured the CCT of 44 normal eyes of 22 subjects using anterior OCT, Orbscan II, and US pachymetry. Non-contact measurements by anterior segment OCT and Orbscan II were performed first, followed by contact measurements using US pachymetry. Three consecutive measurements were taken with each method and the mean values and correlations were analyzed. RESULTS: The mean value of the CCT was 531.45+/-32.90 micrometer with anterior OCT, 537.11+/-32.21 micrometer with Orbscan II, and 548.18+/-34.17 micrometer with US pachymetry. There was no statistically significant difference among the values obtained by the 3 instruments (P>0.05). CCT measurements by anterior segment OCT were highly correlated with Orbscan II and US pachymetry (P<0.001) measurements. CONCLUSION: CCT measurements by anterior segment OCT are highly correlated with Orbscan II or US pachymetry measurements. Using non-contact anterior segment OCT, a closer examination of the anterior segment including the cornea is possible. The measurement of the CCT using anterior segment OCT is applicable because result values are similar to measurements by Orbscan II or US pachymetry.
Cornea ; Tomography, Optical Coherence* ; Ultrasonography

PURPOSE: To analyze and compare ultrasound pachymetry (USP) with a more recently adopted device, the intra ocular lens (IOL) master 700, which are both used to measure central corneal thickness. METHODS: The central corneal thickness was measured in 24 eyes of 12 glaucoma patients and in 83 eyes of 42 normal patients. First, the IOL master 700 was used to measure the central corneal thickness, followed by measurements taken using USP later. The results were analyzed using a paired t-test. We analyzed the agreement and the correlations between the two test devices by using Bland-Altman plots and the Pearson correlation test. To evaluate the reproducibility, measurements with the IOL master 700 were taken twice for a few normal patients within a small time interval. RESULTS: Via the IOL master 700, the thickness of the central cornea showed a high reproducibility and repeatability, demonstrating 2.7 ± 1.7 µm for the test-retest variability, 6.78% for the coefficient of variation, and 0.997 for the intraclass correlation value. The mean measurements using USP and the IOL master 700 are 554.4 ± 37.4 µm and 551.1 ± 37.1 µm, respectively, showing that the IOL master 700 measured significantly smaller values than USP with a p-value < 0.001. The deviations between the two methods are scattered throughout the 95% confidence interval. According to the Pearson correlation test, the measured values of the two test devices were found to have a highly positive correlation (r = 0.977, p < 0.0001). CONCLUSIONS: This study demonstrated that the central corneal thickness (CCT) measured via the IOL master was significantly thinner than that of USP, and the two test devices had a high correlation and good agreement. The CCT value measured via the IOL master 700 also exhibited high reproducibility.
Cornea ; Glaucoma ; Humans ; Tomography, Optical Coherence* ; Ultrasonography*

Experiments were performed in order to investigate the absorption of the ultrasound by the ocular tissues. Transducers of 5 and 10 MHz and diameters of 5 and 10mm were used. The amplitudes of echoes reflected from the flat metallic surface were measured as the reference echo after the ultrasonic beam passed through the cornea. crystalline lens, vitreous body, outer coats of the eyeball and the whole eyeball. The crystalline lens absorbed ultrasound most strongly whereas outer coats and vitreous body absorbed modorately. The absorption by the cornea was negligibly small compared with other tissues of the eye.
Absorption* ; Cornea ; Lens, Crystalline ; Transducers ; Ultrasonics ; Ultrasonography* ; Vitreous Body

PURPOSE: To investigate the accuracy of intraocular lens power calculations using simulated keratometry (simK) of dual Scheimpflug analyzer and 5 types of formulas in cataract patients. METHODS: The keratometry (K), axial length (AXL) and anterior chamber depth (ACD) were measured using ultrasound biometry (USB) combined with auto-keratometry (Auto-K), parital coherence interferometry (PCI; IOL master®) and dual Scheimpflug analyzer (DSA; Galilei®) in 39 eyes of 39 patients. Predicted refraction was calculated using Auto-K, mean K of PCI, and simK and total corneal power (TCP) of DSA in the Sanders-Retzlaff-Kraff (SRK-T) formula. The SRK-II, SRK-T, Holladay II, Haigis, and Hoffer-Q formula were used to calculate predicted refraction with the simK of DSA and AXL of USB. Manifest refraction, mean numerical error (MNE) and mean absolute error were evaluated 1, 3 and 6 months after cataract surgery. RESULTS: TCP of DSA was lower compared with other keratometric values (p < 0.05). The MNE was not different among Auto-K, mean K and simK. The MNE using TCP was larger compared with Auto-K, mean K and simK at 1 month after surgery (p < 0.05). There was a difference in MNE between simK and TCP of DSA at 6 months after surgery (p < 0.05). The MNE of SRK-T formula was the smallest in the intraocular lens (IOL) power calculation using the simK of DSA. CONCLUSIONS: We suggest using IOL power calculations with simK of DSA and SRK-T formula rather than TCP of DSA in cataract patients with normal corneas.
Anterior Chamber ; Biometry ; Cataract ; Cornea ; Humans ; Interferometry ; Lenses, Intraocular* ; Ultrasonography

PURPOSE: In this study we compared the intraocular pressures (IOPs) measured using dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) and investigated the correlation between central corneal thickness (CCT) and IOP. METHODS: In a prospective study, 178 eyes of 91 subjects with glaucoma and glaucoma suspect were enrolled. IOP was measured using DCT and GAT and CCT was measured using ultrasound pachymetry. Each eye was classified into 1 of 3 groups according to their CCT: low CCT (Group A; CCT < 525 microm), normal CCT (Group B; 525 < or = CCT < 561 microm), and high CCT (Group C; CCT > or = 561 microm). In each group, we investigated the correlation between CCT and IOP measurement using GAT and DCT. RESULTS: A significant correlation was found between CCT and IOP measured using GAT (p < 0.001), but not between CCT and IOP measured using DCT (p = 0.108) in all patients. Subgroup analysis showed that CCT affected IOP measured with GAT only in Group A (p = 0.027) and IOP measured with DCT was not affected by CCT in all 3 groups. CONCLUSIONS: IOP measured using GAT and DCT were significantly affected by CCT, especially when the CCT was low. CCT may have no effect on DCT thus, IOP measured using DCT is more reliable than GAT in patients with thin corneas.
Cornea ; Glaucoma ; Humans ; Intraocular Pressure ; Manometry* ; Prospective Studies ; Ultrasonography

The purpose of this report is to investigate experimentally how the corea, sclera, crystalline lens and focusing lens influence the ultrasound intensity and beam width and to find characteristic differences due to the transducer parameters; frequency and size. A time-amplitude ultrasonic diagnostic apparatus, Aloka Model SSD-2D was used with transcucers of 10 MHz and 5 MHz, 10 mm and 5 mm diameters. The metal ball, 1 mm in diameter, was served as the echo-reflecting target which was immersed in water and moved horizontally under the transducer with a micrometer screw. The distances between the transducer and the metal ball varied from 10 mm to 50 mm in 10 mm step. The amplitudes curves of the echoes so obtained were represented by relative values. In water control experiment, the nearer the metal ball from the transducer, the more irregular the curves, with multiple amplitudes maxima and minima. These irregular curves became homogeneous as the transducer moved away from the target. The multiple peak curves were more marked when measured with transducers of higher frequency and larger diameter. At the end of the near field only a single peak was found in the axial portion of the sound field. In the far field, the beam width reduced slightly due to the divergence of the beam accompanied by slight attenuation of the echo amplitudes. When the sound beam passed through the cornea and sclera, the form of the curves remained almost unchanged, but the amplitudes decreased slightly due to the absorption of the sound energy. Scleral tissue absorbed the energy more strongly then the corneal tissue. When the crystalline lens was placed under the transducer, divergence of the beam and themoderate absorption took place. This effect was more pronounced with the use of transducers of higher frequency and smaller diameter. When a focusing lens, 25 mm focal length, was attached to the transducer surface, sound beam converged to a narrow zone, followed by later scattering. These results suggest that the transducer should be selected as to the frequency and diameter according to the site of the lesion suspected and the nature of the pathology.
Absorption ; Cornea ; Lens, Crystalline ; Pathology ; Sclera ; Transducers ; Ultrasonics* ; Ultrasonography ; Water

PURPOSE: We compared and analyzed central corneal thickness (CCT) measurements according to the corneal thickness obtained with noncontact specular microscopy (NCSM) and ultrasound pachymetry (USP). METHODS: CCT was measured in the order of NCSM and USP by a single optometrist in 120 eyes of 120 healthy subjects. The measurements were compared between the devices and the measurement agreements and correlations between the devices were analyzed. To determine if the measurements differed depending on the thickness of the cornea, the patients were divided into three tertile groups from the thinnest patient by CCT measurement using USP, and then the differences in CCT measured by the two devices were analyzed. RESULTS: The CCT measurements using NCSM and USP were 548.25 ± 4.64 µm and 533.09 ± 35.96 µm, respectively. NCSM measurements were found to be thicker, showing statistically significant differences between the measurements (p < 0.001). The two examinations showed a high degree of correlation (r = 0.878; p < 0.01). In the three groups, the differences in CCT measurements between NCSM and USP were 12.93 ± 21.88 µm, 16.85 ± 15.89 µm, and 15.70 ± 20.46 µm, respectively, but the differences between the three groups were not statistically significant (p = 0.655). CONCLUSIONS: Our results show that although the differences in CCT measurements using NCSM and USP were consistent regardless of the corneal thickness, the CCT measurements by NCSM and USP were highly correlated.
Cornea ; Corneal Pachymetry ; Healthy Volunteers ; Humans ; Microscopy ; Ultrasonography

The maintenance of corneal endothelial cells is essential for success of corneal transplantation. Endothelial cell count by specular microscope and measurement of donor corneal thickness is useful in measuring the function of cornea. We studied difference of corneal thickness in central and peripheral corneal region in enucleated eye. We measured corneal thickness of 48 eyes(48 persons) with ultrasound pachymetry that were presented to The Eye Bank of Catholic University Medical College. Average age was 61.42+/-16.12 years and average time was 163.02+/-102.52 minutes until measurement of corneal thickness after death. Increased amount of corneal thickness was 136.73+/-101.44micrometer in center and 61.37+/135.46micrometer in periphery compared with normal average corneal thickness. According to these results, corneal edema due to functional loss of endothelial cells after death lead to increased corneal thickness, especially in central region being more statistically significant than peripheral region (p=0.002).
Cornea ; Corneal Edema ; Corneal Transplantation ; Endothelial Cells ; Eye Banks ; Humans ; Tissue Donors ; Ultrasonography

PURPOSE: Accurate assessment of corneal thickness is important in order to prevent iatrogenic corneal ectasia after laser in situ keratomileusis (LASIK). More accurate measurement is needed in LASIK enhancement because the cornea becomes thin after previous refractive surgery. We evaluated the reliability of corneal thickness measurement with ultrasound pachymeter (USP) in the thin corneas. METHODS: The corneal thickness was measured in the 22 eyes of 11 rabbits. The corneal flap was made with an Automated Corneal Shaper microkeratome (Bausch and Lomb, USA) with 130 micro meter plate and the flap was removed in order to make the cornea thin. Residual stromal bed (RSB) thickness was measured with USP and thickness gauge, and the two measurements were compared. RESULTS: Mean corneal thickness was 404.69 +/- 11.01 micro meter with USP and 133.23 +/- 15.66 micro meter with thickness gauge. RSB thickness measured with thickness gauge was 269.05 +/- 24.19 micro meter and this was not significantly different from the expected RSB thickness, although RSB thickness measured with USP was 388.14 +/- 10.17 micro meter, which was significantly different from the expected RSB thickness (p=0.00). CONCLUSIONS: In the thin corneas, corneal thickness measurement with ultrasound pachymeter is not reliable.
Cornea* ; Corneal Pachymetry* ; Dilatation, Pathologic ; Keratomileusis, Laser In Situ ; Rabbits ; Refractive Surgical Procedures ; Ultrasonography*