Ultrasound Pachymetry Research Articles

Flap thickness reproducibility in laser in situ keratomileusis with a femtosecond laser: Optical coherence tomography measurement

To compare ultrasound (US) pachymetry, Orbscan, and optical coherence tomography (OCT) measurements of the central corneal thickness (CCT) before laser in situ keratomileusis (LASIK) and evaluate the reproducibility of flaps created with the IntraLase femtosecond laser (IntraLase, Inc.) using OCT. Department of Ophthalmology, IIsan Paik Hospital, Goyang, Korea. Central corneal thickness was measured using OCT, US pachymetry, and Orbscan in 59 eyes of 30 patients before femtosecond laser LASIK. The postoperative corneal flap thickness, measured using OCT, was compared with the preoperative intended thickness. Optical coherence tomography, US pachymetry, and Orbscan measurements provided similar CCT values (P>.05). Corneal thickness values obtained using US or Orbscan correlated well with those obtained by OCT, with the correlation coefficient ranging from 0.804 to 0.889 (P<.05). The OCT measurements showed no significant difference between the postoperative flap thickness and the intended flap thickness (P>.05). Optical coherence tomography was comparable to US pachymetry and Orbscan in cornea thickness measurement. Optical coherence tomography was easy and relatively accurate to use preoperatively and in the early postoperative period. The femtosecond laser created highly reproducible flaps that corresponded with the preoperative intended thickness.

Comparison of Central Corneal Thickness using Anterior Segment Optical Coherence Tomography vs Ultrasound Pachymetry

To determine if there is a systematic difference in central corneal thickness (CCT) measured using anterior segment optical coherence tomography (AS-OCT) as compared with ultrasound pachymetry. Prospective observational study. Consecutive subjects with clinically normal corneas underwent CCT measurement by both ultrasound and AS-OCT while participating in a population-based study in Ghana, West Africa. One eye of each subject was randomly selected for analysis. Two measurements were taken and averaged. Agreement and interobserver variability were also analyzed. One hundred and fifty-five subjects of African ethnicity and average age 57 years (standard deviation [SD] 12; range, 40 to 98 years) were included. Measurements by AS-OCT and US were taken a mean of 15 days (maximum, six weeks) apart. The mean (SD) [range] US CCT was 525.3 microm (33.5) [422, 653] and 499.0 microm (32.0) [428, 613] with AS-OCT. Measurements by the two modalities were strongly correlated (r(2) = 0.82; P < .001), and a significant difference was observed between mean US and AS-OCT CCT (SD) [range] of 26.3 microm (14.2) [-63, 12] (P < .001). The width of the limits of agreement was 28 microm, about 6% of the average pachymetry reading. In 50 eyes randomly remeasured with OCT by a second observer, the intraclass correlation coefficient was 0.91. There was a small but significant systematic difference between observers (mean 6.9 microm, SD 10.9 microm), or 1.4% (P < .001), increasing the difference noted above. There is a reproducible systematic difference between CCT measurements taken with ultrasound and OCT. It is important to note in clinical practice, that measurements acquired by these two modalities are not directly interchangeable.

Comparison of central corneal thickness as measured by non‐contact specular microscopy and ultrasound pachymetry before and post LASIK

To compare central corneal thickness (CCT) measurements made by ultrasound pachymetry and non-contact specular microscopy in eyes before and post laser in situ keratomileusis (LASIK). Forty eyes of 20 consecutive refractive surgery candidates were included in this study. The CCT in both eyes was measured before and 3 months after LASIK with a non-contact specular microscope and a ultrasound pachymeter. Both before and after LASIK, the difference of the mean CCT between non-contact specular microscopy and ultrasound pachymetry was statistically significant (P < 0.001 before surgery, and P = 0.02 after surgery). The difference between them was -14.41 microm and -3.69 microm, respectively. In both situations, non-contact specular microscopy and ultrasound pachymetry measurements were highly correlated (r = 0.959, before surgery, and r = 0.979 after LASIK). Bland-Altman analysis showed that either before or post LASIK, the 95% limits of agreement have a span of approximately 30 microm. Preoperatively, the mean standard deviation of repeated measurements was 4.26 microm by ultrasound pachymetry, and 4.02 microm by non-contact specular microscopy, whereas it was 3.83 microm by ultrasound pachymetry, and 3.89 microm by non-contact specular microscopy, postoperatively. No statistically significant differences were found between the mean standard deviations by these two devices in both situations (P = 0.561 before surgery, and P = 0.849 after LASIK). Both before and after LASIK, non-contact specular microscopy is not in complete agreement with ultrasound pachymetry in measuring CCT. Both devices provided comparable repeatability of measurements.

Association between stature, ocular biometry and refraction in an adult population in rural Myanmar: the Meiktila eye study

To study the association between adult stature and ocular biometric parameters and refraction. In a population-based cross-sectional ophthalmic survey of 2418 adults (> or = 40 years old) living in the rural villages in central Myanmar, height and weight were measured using a standardized protocol, and body mass index was calculated. Non-cycloplegic refraction and corneal curvature were determined by an autorefractor. Ultrasound pachymetry was performed and ocular biometry, including axial length, anterior chamber depth, lens thickness and vitreous chamber length were measured using A-mode ocular ultrasonography. Height and weight were significantly correlated with age, gender and all the ocular biometric parameters, except lens thickness. After adjusting for age and gender, taller and heavier persons had eyes with longer axial length, deeper anterior and vitreous chambers, and flatter and thicker corneas than shorter persons. Height was not significantly correlated with refraction, and heavier persons tended to be less myopic (P < 0.001). Multivariate linear regression models revealed consistent results with the findings for association between height, weight and ocular biometry and refractive error. Adult stature is independently associated with vitreous chamber length and corneal radius in this Burmese population. Heavier persons were slightly hyperopic.

Comparison of Corneal Thickness Measurements by Ultrasound and Scheimpflug Photography in Eyes That Have Undergone Laser In Situ Keratomileusis

To compare two methods of measuring central cornea thickness (CCT) in eyes that have undergone laser in situ keratomileusis (LASIK). Prospective clinical trial. The corneal thickness from 104 eyes of 53 consecutive patients undergoing the one-year follow-up after LASIK was measured with both the Pentacam (Oculus, Inc, Wetzlar, Germany) and ultrasonic pachymetry. All patients were examined at one clinical setting, where first Pentacam imaging was performed by one technician and then ultrasound pachymetry was performed by a masked second technician. The results were compared. The average age of the patient population was 38 years (range, 22 to 56 years) of those who underwent the one-year follow-up examination an average of 406 days (range, 264 to 579 days) after LASIK. The mean CCT measurement was 506 +/- 29.5 microm (range, 454 to 574 microm) with the Pentacam topographer and 505 +/- 31.7 microm (range, 433 to 576 microm) with ultrasound pachymetry. The average difference (Pentacam minus ultrasound) was 1.4 +/- 10.4 microm (range, -21.8 to 23.4 microm). The Pentacam's CCT measurement and that of ultrasound pachymetry show good correlation. Pentacam pachymetry may be substituted for ultrasound in the post-LASIK patient.

Thin-flap LASIK to Increase the Range of Treatments Using the NIDEK EC-5000 CX Excimer Laser

To compare the safety, advantages, and disadvantages of two LASIK groups that underwent surgery with a standard-thickness 130-microm microkeratome head (standard thickness group) and a 90-microm microkeratome head (thin flap group) prior to ablation with the NIDEK EC-5000 CX excimer laser. Two hundred seventeen patients (420 eyes) with myopia or hyperopia underwent LASIK with either a 130-microm microkeratome head (137 eyes of 74 patients) or 90-microm microkeratome head (283 eyes of 143 patients). Corneal and stromal bed thickness prior to ablation were measured three consecutive times using ultrasound pachymetry. Averages of the corneal bed with the flap reflected, the flap thickness, and residual stromal bed were calculated for both groups. The postoperative appearance of the flaps and stroma in both groups were compared by slit-lamp examination. No difference in preoperative corneal thickness was found between groups. Eyes that underwent treatment with the 130-microm microkeratome head had a mean flap thickness of 163.6 +/- 29.60 microm (range: 71 to 246 microm). Eyes that underwent treatment with the 90-microm microkeratome head had a mean flap thickness of 113.30 +/- 24.26 microm (range: 65 to 182 microm). No intra- or postoperative complications occurred in either group. Flap appearance was similar in both groups. Both 130-microm and 90-microm microkeratome heads have similar predictability. Using a 90-microm microkeratome head leaves a thicker stromal bed for ablation.

The relationship between central corneal thickness and the optic disc in an elderly population: the Bridlington Eye Assessment Project

To determine population-based normative CCT data for elderly white subjects, with and without diabetes, and to explore the relationship between CCT and IOP and HRT2 measurements in such subjects with normal visual fields. All eligible subjects were consecutive in a population screened for eye disease. CCT was measured by ultrasound pachymetry, and the optic disc was morphometrically defined using Heidelberg retinal tomography (HRT2). Inclusion criteria were: (1) normal visual field on suprathreshold testing and (2) corrected logMAR acuity of at least 0.3 in both eyes. Subjects with significant corneal pathology, previous corneal surgery, or known history of glaucoma or treatment for raised intraocular pressure were excluded. One eye was randomly selected from each subject for analysis. In all, 983 eyes of 983 subjects were included with 690 HRT images deemed acceptable for the analysis. The mean age (414 men and 569 women) was 73.3 years (minimum 65 years). Mean (SD) CCT was 544.1 (36.5) microm, with a normally distributed range of 429-633 microm. There was no significant difference in CCT between men and women (mean CCT 546.1 and 542.7 microm, respectively, P=0.15, Student's t-test), though CCT was correlated weakly and negatively with age (Pearson's r=-0.063, P=0.047). Diabetic patients (n=103) had a greater mean CCT than non-diabetic patients (551.9 and 543.0 microm respectively, P=0.02). No significant correlation was found between any global optic disc parameter and CCT in the 690 eyes analysed. Elderly white eyes with normal fields have CCTs that are normally distributed, with those from diabetic persons having greater CCTs. No clear evidence of a relationship between CCT and HRT2 optic disc parameters used in glaucoma diagnosis was found.

Evolution of central corneal thickness in children with congenital glaucoma requiring glaucoma surgery

The purpose of the study was to investigate the evolution of central corneal thickness (CCT) in correlation to the intraocular pressure (IOP) in children with congenital glaucoma before and after glaucoma surgery. Nine eyes of five children (age 2 weeks to 6 months, mean 23 weeks) underwent trabeculotomy for congenital glaucoma. Corneal ultrasound pachymetry (PacScan 3000 AP, Technomed, Germany), tonometry using the Perkins tonometer, and slit-lamp examination (additionally to a clinical routine examination with retinoscopy, funduscopy, measurement of axial length and corneal diameter) were performed before and for at least 12 months after glaucoma surgery. In all children, corneal pachymetry and slit-lamp biomicroscopy--and whenever possible applanation tonometry--were performed without sedation or general anesthesia. If measurement of the IOP was not possible otherwise (in four of the five children), sedation with midazolam orally was used to measure the IOP at 2 weeks, 6 weeks, and 3 months after trabeculotomy, then every 3 months. Six of nine eyes had biomicroscopically clear corneas without visible corneal edema before trabeculotomy. In three eyes, a corneal edema was visible in at least one quadrant of the cornea. Regarding all eyes together, mean CCT was 651 +/- 138 microm before trabeculotomy; this decreased to 592 +/- 119 microm within 2 weeks after trabeculotomy. At 6 weeks and 3 months there was a further regression to 569.4 +/- 16 microm. Mean IOP was 18.6 +/- 7.5 mmHg before and decreased to 14.8 +/- 5.8 mmHg after glaucoma surgery. Regarding IOP data obtained under general anaesthesia, decrease of CCT was significantly correlated with decrease in IOP. There was no significant difference in the correlation between eyes with and without visible corneal edema. Corneal ultrasound pachymetry appears to be a valuable additional measure in the follow-up of infants and small children requiring glaucoma surgery.

Comparative Study of Central Corneal Thickness Measurement with Slit-Lamp Optical Coherence Tomography and Visante Optical Coherence Tomography

To evaluate the repeatability and reproducibility of central corneal thickness (CCT) measurements obtained by 2 anterior segment optical coherence tomography (OCT) imaging systems and to examine their agreements with ultrasound pachymetry. Observational cross-sectional study. Fifty eyes from 50 healthy normal subjects were recruited. In one randomly selected eye in each subject, CCT was measured by slit-lamp OCT (SLOCT), Visante OCT, and ultrasound pachymetry. For anterior segment OCT measurements, both automatic and manual CCTs were obtained. Twenty-five of the 50 subjects were invited for 2 more visits within a week to evaluate repeatability and reproducibility of CCT measurement. Central corneal thickness measurement obtained by the 3 methods and their agreements. Intrasession and intersession within-subject standard deviation (S(w)), precision (1.96xS(w)), coefficient of variation (CV(w)) (100xS(w)/overall mean), and intraclass correlation coefficient (ICC) were calculated to evaluate repeatability and reproducibility. Good repeatability and reproducibility were found for both automatic and manual CCT measurements obtained by SLOCT and Visante OCT. For intrasession repeatability, CV(w) and ICC values ranged between 0.9% and 1.2% and 0.96 and 0.98, respectively. For intersession reproducibility, the respective CV(w) and ICC values ranged between 1.2% and 1.4% and 0.94 and 0.96. Although no significant difference was found between automatic/manual SLOCT measurements and ultrasound pachymetry, automatic Visante OCT CCT (535.7+/-30.2 microm) was significantly less than CCT with ultrasound pachymetry (550.3+/-31.14 microm) (P<0.001). In contrast, manual Visante OCT measurement (558.8+/-32.8 microm) was slightly higher than ultrasound pachymetry (P<0.001). Nevertheless, SLOCT and Visante OCT measurement of CCT had 95% limits of agreement comparable to that of ultrasound pachymetry. The best agreement was observed in the manual SLOCT measurement (95% limits of agreement between -15.5 and 11.7 microm). Both SLOCT and Visante OCT automatic and manual CCT measurements were reliable and showed comparable agreement with ultrasound pachymetry. Although the 2 anterior segment OCT imaging systems have similar design and working principles, clinicians should be aware of the differences in CCT measurement between the 2 anterior segment OCTs.

Importancia del espesor corneal central en el estudio de hipertensos oculares, sospechosos de glaucoma y glaucomas preperimétricos

To compare the central corneal thickness, measured with an ultrasound pachymeter, in normal subjects, those with ocular hypertension, glaucoma suspects and patients with preperimetric glaucoma. 61 normal eyes (control group), 131 eyes with ocular hypertension, 62 glaucoma suspects (optic nerve head morphology compatible with glaucoma) and 36 patients with preperimetric glaucoma (abnormal short-wavelength automated perimetry) were prospectively and consecutively selected. Scatter plots of central corneal thickness, against the intraocular pressure values were calculated for each of the study groups. Ultrasound pachymetry measurements were compared between those with normal eyes and the other groups. Ocular hypertensive subjects had higher pachymetry values than the control group (p=0.009). No differences were found in the central corneal thickness between normal eyes and those who were glaucoma suspects, and between normal and preperimetric glaucomatous eyes. A mild direct logarithmic correlation was evident between central corneal thickness and the Goldmann tonometry result in the ocular hypertensive group. Ocular hypertensive subjects had thicker corneas than the other groups studied. Glaucoma suspects and preperimetric glaucoma patients had similar corneal thickness to the control group.

Central corneal thickness measurement with Pentacam, Orbscan II, and ultrasound devices before and after laser refractive surgery for myopia

To determine the agreement in central corneal thickness (CCT) measurements between the gold standard method of ultrasound (US) pachymetry (UP-1000, Nidek) and 2 noncontact systems based on Scheimpflug imaging (Pentacam, Oculus) and scanning-slit topography (Orbscan II, Bausch & Lomb) in myopic eyes before and after laser refractive surgery. Noor Vision Correction Center, Tehran, Iran. In this prospective study, 30 consecutive patients having refractive surgery for myopia were enrolled. All 60 eyes were examined with the 3 devices preoperatively and 6 weeks after surgery; the US measurements were performed last. The Pentacam and Orbscan II CCT readings were compared with the US readings. Both the original and corrected Orbscan II readings were used in the analyses. The mean CCT readings with US, Pentacam, and Orbscan II were, respectively, 555 microm, 548 microm, and 580 microm before surgery and 478 microm, 468 microm, and 474 microm after surgery. Preoperatively, the 95% limits of agreement (LoA) with US were -31 microm and +19 microm for the Pentacam device and -5 microm and +57 microm for the Orbscan II device. Postoperatively, the LoA were -40 microm and +19 microm and -51 microm and +50 microm, respectively. Corrected Orbscan II measurements gave 95% LoA of -48 microm and +6 microm before surgery and -85 microm and +5 microm after surgery. Refractive surgery had a modest effect on the agreement between Pentacam readings and US measurements. With Orbscan II, the 95% LoA width nearly doubled after surgery. Although the Pentacam seems to show better agreement than Orbscan II, especially after refractive surgery, it is not advisable to use the 3 devices interchangeably in every clinical situation.

Reproducibility and Repeatability of Central Corneal Thickness Measurement in Keratoconus Using the Rotating Scheimpflug Camera and Ultrasound Pachymetry

To assess repeatability, reproducibility, and agreement of rotating Scheimpflug camera (Pentacam Oculus, Wetzlar, Germany) and ultrasound pachymetry in measuring central thickness of keratoconic corneas. Method-comparison study. In 33 patients with keratoconus (one eye per patient), two examiners each used both pachymetric methods to measure central corneal thickness (CCT); in the same session, measurements then were repeated by examiner 1 (A.M.). The difference between two examiners, and between first and second measurements by examiner 1, with both methods and the difference between the two pachymetric methods in measuring central thickness of keratoconic corneas were noted. With the rotating Scheimpflug camera, interexaminer correlation was higher (intra-class correlation coefficient [ICC], 0.98 vs 0.76) and inter-examiner variability was lower (95% limits of agreement [95% LoA], -14.8 to 13.8 microm vs -18.0 to +49.5 microm) than with ultrasound pachymetry. Both methods showed close first- to second-measurement correlation (ICC, > 90), but the rotating Scheimpflug camera had lower variability (95% LoA, -14.5 to 14.2 microm vs -27.4 to 26.0 microm). Mean CCT was 478.9 +/- 34.6 microm with the rotating Scheimpflug camera and 486.6 +/- 30 microm with ultrasound pachymetry. Although the mean difference was small (-7.8 microm), the 95% LoA (-43.8 to 28.2 microm) showed that the difference between the two methods can be considerable. In keratoconic corneas, the rotating Scheimpflug camera provides measurements of central thickness that are more reproducible and repeatable than those obtained with ultrasound pachymetry. The rotating Scheimpflug camera seems to be suitable for disease staging and follow-up, when corneal thickness measurements may be repeated over time by different examiners.

Central corneal thickness among Aboriginal people attending eye clinics in remote South Australia

To determine the central corneal thickness (CCT) and its demographic associations among Aboriginal people attending eye clinics in remote South Australia. A clinic-based cross-sectional study was conducted involving opportunistic sampling of patients. Eligible participants underwent measurement of CCT by ultrasound pachymetry. The results were compared with a group of Caucasian control patients. All patients (189) who were invited to participate in the study had their CCT measured. The mean age was 44.8 +/- 14.5 years, and women comprised 57.7% of the sample. The control group consisted of 115 Caucasian participants. The mean age was 47.1 +/- 14.8 years, and women accounted for 55.7% of the sample. Mean CCT for Aboriginal participants was 514.9 +/- 30.5 microm in the right eye and 515.6 +/- 30.5 microm in the left eye (t = 1.1, P = 0.3). Mean right CCT for Caucasian participants was 544.6 +/- 31.9 microm and mean left CCT in this group was 547.1 +/- 32.2 microm (t = 4.6, P < 0.001). There was a significant difference between the right (t = 8.4, P < 0.001) and left (t = 8.8, P < 0.001) CCT of Aboriginal and Caucasian participants. The CCT among Aboriginal patients attending eye clinic in remote South Australia was significantly thinner than that of a Caucasian control group. Thinner corneas among this group of Aboriginal patients may indicate a need to adjust intraocular pressure according to CCT and to be more vigilant for glaucoma.

Comparison of Optical Low Coherence Reflectometry and Ultrasound Pachymetry in the Measurement of Central Corneal Thickness Before and After Photorefractive Keratectomy

To compare an ultrasound pachymeter with an optical low coherence reflectometry (OLCR) pachymeter for measuring pre- and postoperative central corneal thickness of patients undergoing photorefractive keratectomy (PRK). In a prospective, noncomparative, interventional study, 48 myopic eyes (mean manifest refractive spherical equivalent: -4.93 +/- 2.93 diopters [D]) of 30 healthy patients underwent PRK. Pre- and postoperative central corneal thickness was measured by two examiners (E1, E2) with an ultrasound pachymeter and an OLCR pachymeter. Agreement and inter-rater repeatability were determined using the comparison method described by Bland and Altman. The limits of agreement between the two devices ranged from 17.8 microm (E1) to 20.5 microm (E2) preoperatively and from 22.4 microm (E1) to 16.9 microm (E2) postoperatively. The coefficient of inter-rater repeatability ranged from 9.1 microm (ultrasound pachymeter) to 5.4 microm (OLCR pachymeter) preoperatively and from 7.1 microm (ultrasound pachymeter) to 4.7 microm (OLCR pachymeter) postoperatively. The OLCR pachymeter seems to show better pre- and postoperative repeatability compared to the ultrasound pachymeter. The agreement between the two devices should be considered acceptable for clinical practice. Photorefractive keratectomy did not affect the postoperative agreement and repeatability of the pachymeters.

Are pachymetric and tonometric asymmetry related?

Abstract Purpose: Goldmann applanation tonometry readings are affected by central corneal thickness. We have determined the level of pachymetric and tonometric asymmetry in normal, diabetic, ocular hypertensives and diabetic ocular hypertensive patients, and the relationship between both asymmetries. Methods: Four groups, one of 77 normal patients (N), one of 59 type II diabetic patients (DM), one of 74 patients with ocular hypertension (OHT), and one group of 61 type II diabetic ocular hypertensive patients (DMOHT) have been included. Ocular exploration, including ultrasound pachymetry, has been performed in all of them. Time from diagnosis and current treatment are also recorded. Interocular differences are analyzed by the SPSS 14.0 program using ANOVA and Pearson tests. Results: The pachymetric asymmetry between groups is not significant (ANOVA P &lt; 0,072). The difference between pachymetric assymetry in diabetic patients (DM+DMOHT) 6,83±5,45μ and non‐diabetic patients (N+OHT) 5,50±5,01μ is statistically significant (P &lt; 0.037). This difference is not significant between ocular hypertensives (OHT+DMOHT) and ocular normotensives (N+DM) (P &lt; 0,982). There is not linear correlation between pachymetric and tonometric asymmetry in the whole sample (r = 0,003). Pachymetric asymmetry correlates with time from diagnosis, and asymmetry is bigger under treatment with insuline, and in retinal proliferative stages. IOP asymmetry correlates with time from diagnosis, is bigger for insuline treated patients and is similar through the different stages of retinopathy. Conclusions: Pachymetric asymmetry is not related to tonometric asymmetry in this study. Diabetic patients showed bigger pachymetric asymmetry than non diabetic patients, but is not related to tonometric asymmetry.

Analysis of ectasia after laser in situ keratomileusis: Risk factors

To examine a database of laser in situ keratomileusis (LASIK) procedures for preoperative and operative factors assumed to increase the risk for developing post-LASIK ectasia. Private clinical practice. A computer database was queried for eyes that had LASIK for myopic refractive errors with the following characteristics: preoperative corneal thickness 500 microm or less, mean keratometry greater than 47.0 diopters (D), patient age 25 years or younger, attempted correction greater than -8.0 D, refractive astigmatism not with-the-rule and greater than 2.0 D, and residual stromal bed thickness (RST) 250 microm or less. Flap thickness and RST were measured using ultrasound pachymetry. All recorded information was exported to MS Excel and analyzed for eyes that had ectasia. Of the 9700 eyes in the database, none with the above characteristics developed ectasia over mean follow-up periods exceeding 2 years. Seven eyes had multiple risk factors without ectasia. Three eyes with abnormal preoperative topography developed ectasia. Individual preoperative and operative factors did not in and of themselves increase the risk for ectasia. Unmeasured and unknown factors that affect the individual cornea's biomechanical stability, in combination with some suspected risk factors as well as the current inability to identify corneas at risk for developing ectatic disorders, probably account for most eyes that develop ectasia today.

Graft Central Thickness Measurement by Rotating Scheimpflug Camera and Ultrasound Pachymetry after Penetrating Keratoplasty

To assess agreement between rotating Scheimpflug camera and ultrasound pachymetry in measuring graft central thickness, and compare reproducibility/repeatability of these methods in corneal grafts and normal corneas. Experimental study. Sixty-five patients with corneal grafts after penetrating keratoplasty and 20 controls with normal corneas (1 eye per patient). In 45 eyes with clear grafts after penetrating keratoplasty, graft central thickness measurements were compared between the 2 methods (examiner 1). In another 20 eyes with clear grafts after penetrating keratoplasty and in 20 normal corneas, 2 independent examiners (1 and 2) each employed both methods in a first session to assess interexaminer reproducibility; measurements were then repeated by examiner 1 alone in a second session, and differences with his first session measurements used to assess intraexaminer repeatability. Paired t test, intraclass correlation coefficient (ICC) and 95% limits of agreement (95% LoA) were calculated to assess differences, correlation, and variability of methods, examiners, and first-second measurements. Graft central thickness measurements by 2 methods. Difference of measurements by 2 examiners; and difference of first-second measurements by 1 examiner, in corneal grafts and normal corneas with both methods. Mean graft central thickness measurement was 556.9+/-41.8 microm with the rotating Scheimpflug camera and 561.8+/-40.8 with ultrasound pachymetry (P = 0.012). There was a significant linear correlation in graft central thickness measurement between the 2 methods (r = 0.93; P<0.001) and 95% LoAs were -34 to +23.4 microm. Interexaminer and intraexaminer correlations were high with both methods: ICCs were > or = 0.94 in corneal grafts and > or = 0.98 in normal corneas. Interexaminer and intraexaminer variability was slightly higher with the rotating Scheimpflug camera than with ultrasound pachymetry, and in corneal grafts than in normal corneas. Measurements of graft central thickness with the rotating Scheimpflug camera, although slightly lower, were comparable to those with ultrasound pachymetry. The reproducibility and repeatability of these methods in corneal grafts are only slightly lower than in normal corneas.

Tonometria, paquimetria e comprimento axial ocular em cães glaucomatosos submetidos à ablação uveal intravítrea

Estudaram-se as alterações tonométricas, paquimétricas e de comprimento axial em cães com glaucoma submetidos à ablação uveal intravítrea. Foram avaliados 13 olhos irreversivelmente cegos de cães que apresentavam glaucoma crônico unilateral, nos quais realizou-se a ablação uveal intra-vítrea, por meio de injeção na câmara vítrea de 0,5ml de sulfato de gentamicina (40mg/ml) associado a 0,3ml de fosfato de dexametasona (4mg/ml). As mensurações da pressão intra-ocular (Po), espessura corneana e eixo axial com tonometria de aplanação, paquimetria ultra-sônica e ultra-sonografias modos A e B foram realizadas no dia da ablação (M0) e após uma (M1), quatro (M4), oito (M8), 12 (M12), 24 (M24) e 48 semanas (M48). A Po diminuiu significativamente em todos os momentos em relação ao M0, com aumento da espessura corneana ao longo do experimento. Nas avaliações ultra-sonográficas notou-se diminuição significativa do bulbo ocular a partir de M4, com medidas ultra-sonográficas modo A significativamente maiores que as do modo B. O procedimento foi efetivo na redução da Po e na diminuição do eixo axial, demonstrando ser viável no controle do glaucoma crônico em olhos irreversivelmente cegos, e ser uma alternativa à enucleação e inserção de prótese ocular.

Central corneal thickness measurements using Orbscan II, Visante, ultrasound, and Pentacam pachymetry after laser in situ keratomileusis for myopia

To compare corneal pachymetry assessment using 4 measurement methods in eyes after laser in situ keratomileusis (LASIK) for myopia. Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong Eye Hospital, Hong Kong SAR. Fifty-two consecutive patients (103 eyes) who had LASIK for the correction of myopia had Orbscan II (Bausch & Lomb), Visante (Carl Zeiss Meditec), Pentacam (Oculus, Inc.), and ultrasound (US) pachymetry (Sonomed, 200P) 6 months after surgery. Data were analyzed using the paired sample t test, Bland-Altman plots, and linear regression. The mean postoperative pachymetry measured by US, Orbscan (0.89 acoustic factor), Pentacam, and Visante pachymetry were 438.2 microm+/-41.18 (SD), 435.17+/-49.63 microm, 430.66+/-40.23 microm, and 426.56+/-41.6 microm, respectively. Compared with the US measurement, Pentacam and Visante measurements significantly underestimated corneal thickness by a mean of 7.54+/-15.06 microm (P<.01) and 11.64+/-12.87 microm (P<.01), respectively. There was no statistically significant difference between US and Orbscan measurements. Pentacam and Visante measurements of corneal thickness 6 months after LASIK were significantly less than those obtained using Orbscan and US pachymetry, although all 4 measurement methods showed a high correlation with each other.

Does Blunt Ocular Trauma Induce Corneal Astigmatism?

To determine the effect of blunt ocular trauma on refractive astigmatism. Eighty-six eyes of 86 patients with known previous refractive status exposed to blunt ocular trauma were included in the study. Trauma-induced astigmatism (TIA) was calculated using vector analysis. In eyes with TIA, central corneal thickness was assessed by ultrasound pachymetry, and corneal topographies were obtained. Anterior-chamber angles were examined by Goldmann 3-mirror lens to find microhemorrhages, scarring, or recession. Patients were followed up between 8 and 12 months (average, 9.2 months). In 18 eyes (21%), TIA was detected. Six (7%) of these eyes had lenticular astigmatism caused by traumatic lens subluxation. In the remaining 12 eyes (14%), corneal topography showed regular astigmatic patterns, which were symmetrical in 3 eyes and asymmetric in the remaining 9. The etiologic factor was a game marble in 6 eyes and a stone in the remaining 6. The mean central corneal thickness was 535.75 microm (range, 498-570 microm) in these 12 eyes. In 9 of these 12 eyes, recession or scarring in the anterior-chamber angle was detected at 1 edge of the steepest axis. Blunt trauma can induce astigmatism. Hard and small objects are more likely to induce astigmatism.