Accuracy of modern intraocular lens power calculation formulas in refractive lens exchange for high myopia and high hyperopia.

PURPOSE: To determine the accuracy of the Holladay 2, Hoffer Q, SRK/T, and Haigis intraocular lens (IOL) power calculation formulas in high myopic and high hyperopic refractive lens exchange (RLE) with hydrophobic acrylic foldable IOLs. SETTING: Department of Ophthalmology, Johann Wolfgang Goethe University, Frankfurt am Main, Germany. METHODS: Preoperatively, axial length (AL) was measured by partial coherence interferometry with the IOLMaster. The RLE was performed by phacoemulsification with posterior chamber IOL implantation in the capsular bag. Optimization of the lens constants for each IOL type was done separately for eyes with a positive lens and eyes with a negative lens. Prediction error (predicted refraction - postoperative refraction) and mean absolute error were back-calculated for the Holladay 2, Hoffer Q, SRK/T, and Haigis formulas. RESULTS: Sixty-three eyes (44 myopic, AL >or=26.0 mm; 19 hyperopic, AL

Measuring contrast sensitivity under different lighting conditions: comparison of three tests.

PURPOSE: The purpose of this study was to evaluate three psychophysical tests for the measurement of contrast sensitivity (CS) and disability glare (DG) at different luminance levels. METHODS: In 60 eyes of 60 individuals (group 1: 20 healthy eyes of young individuals; group 2: 20 healthy eyes of elderly subjects; group 3: 20 eyes with nuclear cataract), CS with best correction was measured twice with the Frankfurt-Freiburg Contrast and Acuity Test System (FF-CATS) and the Functional Acuity Contrast Test (FACT, 1.5 cycles per degree [cpd]) at 167 cd/m2 and 0.167 cd/m2, and with the Pelli-Robson Chart (PRC) at 100 cd/m2 with and without glare. Repeatability of test and retest, and discriminative ability between the different subgroups, were assessed for CS values. RESULTS: Maximum CS values varied across tests. In all groups, highest CS values were obtained with the photopic FF-CATS. For FACT scores at 1.5 cpd, there was a ceiling effect for young subjects. CS scores obtained with the PRC were the lowest. The PRC had the best test-retest repeatability of all tests. Under mesopic conditions with glare, reliability was generally lower; the FF-CATS had the highest repeatability of the mesopic tests. The FF-CATS discriminated best between the different groups for all conditions. CONCLUSIONS: There are large discrepancies in the test results between CS testing methods, especially under different lighting conditions. Results from different CS tests are not interchangeable.

Incidence of posterior vitreous detachment after laser in situ keratomileusis.

BACKGROUND: Vitreoretinal complications are rare in laser in situ keratomileusis (LASIK). Increase in intraocular pressure caused by intraoperative suction with subsequent deforming of the ocular globe and excimer laser shock during the ablation have been discussed as possible causes. The purpose of this study was to determine the effect of LASIK on the vitreous body. PATIENTS AND METHODS: In a prospective study we performed ocular ultrasonography (B scan) immediately before and 1 week after LASIK procedure in 103 myopic or myopic-astigmatic eyes (53 patients, mean age 36.3 years, 32 women, 21 men). In particular, the prevalence, localization, and extent of posterior vitreous detachment (PVD) were determined. RESULTS: The mean spherical equivalent was -4.85 D (range -1.25 to -8.38) and the mean anteroposterior ocular globe length was 25.13 mm (range 23.31-27.65). Ninety-five eyes (92.2%) had no PVD preoperatively. Nine eyes out of this group (seven patients, 9.5%) developed incomplete PVD as assessed 1 week postoperatively. Eight eyes (7.8%) had a partial PVD preoperatively and in only one eye was an extension of vitreous detachment observed after the surgery. None of the preoperatively measured parameters could predict the occurrence of PVD by LASIK. CONCLUSIONS: LASIK may in rare cases lead to new occurrence of PVD or extension of a previously existing partial PVD.

Correlation of infrared pupillometers and CCD-camera imaging from aberrometry and videokeratography for determining scotopic pupil size.

PURPOSE: To compare 2 infrared pupillometers with a videokeratographer and 2 aberrometers for the determination of scotopic pupil size. SETTING: Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany. METHODS: The pupil diameter was measured in 100 eyes of 51 patients after 2 minutes of dark adaptation using the following devices: digital infrared pupillometer (Procyon Instruments Ltd.), handheld infrared pupillometer (Colvard) (Oasis Medical), Zywave aberrometer (Bausch & Lomb), Wasca aberrometer (Asclepion-Meditec-Zeiss), and Orbscan II topography system (Bausch & Lomb Surgical). Measurements taken with the Procyon pupillometer were considered reference values for comparison with the other devices. Statistical evaluation was performed using the Bland-Altmann method for comparison of measurement techniques. RESULTS: The mean pupil size was 6.10 mm +/- 0.86 (SD) with the Procyon pupillometer, 5.68 +/- 1.07 mm with the Colvard pupillometer, 5.91 +/- 1.01 mm with the Zywave aberrometer with the fixating target turned off, 5.09 +/- 1.14 mm with the Zywave aberrometer with the fixating target turned on, 5.59 +/- 0.99 mm with the Wasca aberrometer, and 3.75 +/- 0.67 mm with the Orbscan topographer. The limits of agreement were smallest for measurements between Procyon and Colvard and largest for measurements between Procyon and Orbscan. The sign test revealed statistically significant differences for all devices compared with the Procyon pupillometer (P<.001 in all cases) except the Zywave aberrometer with the fixating target turned off (P=.13). CONCLUSIONS: The Zywave wavefront sensor with the fixating target turned off using the study settings and light conditions provided measurements of scotopic pupil diameter that were closest to the reference values (Procyon). With the other devices (Colvard pupillometer, Zywave aberrometer with the fixating target switched on, Wasca aberrometer, and Orbscan topographer), the difference was statistically significant.

Comparison of manual and automated methods to determine horizontal corneal diameter.

PURPOSE: To compare 2 manual methods and 2 automated devices for measuring the horizontal corneal diameter (white-to-white [WTW] distance). SETTING: Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany. METHODS: In 100 eyes of 61 patients, the WTW distance was measured independently by 2 examiners using the following techniques: the Holladay-Godwin gauge, a measuring caliper, Zeiss IOLMaster, and Orbscan II topography system (Bausch & Lomb). The results were compared with measurements on magnified slitlamp photographs of the anterior eye segment. Statistical evaluation was performed using the Bland-Altman method for comparison of measurement techniques. RESULTS: The mean horizontal corneal diameter was 11.91 mm +/- 0.71 (SD) with the measuring caliper, 11.8 +/- 0.60 mm with the Holladay-Godwin gauge, 11.78 +/- 0.43 mm with the Orbscan II, and 12.02 +/- 0.38 mm with the IOLMaster. The coefficient of inter-rater repeatability was 1.30 for the caliper, 0.92 for the Holladay-Godwin gauge, 0.76 for the Orbscan II, 0.50 for the IOLMaster, and 1.16 for the manual measurement in anterior segment images. The results obtained with the caliper were statistically significantly different between the 2 examiners (P<.001). The measurements of examiner 2 using the caliper were significantly different from the measurements of the same examiner using the Holladay-Godwin gauge. This was not the case with the 2 automated devices. CONCLUSIONS: Automated measurement of the WTW distance provides more precise results than measurements using manual methods. The Zeiss IOLMaster had the highest reliability in measuring corneal diameter.

Intraindividual comparison of epithelial defects during laser in situ keratomileusis using standard and zero-compression Hansatome microkeratome heads.

PURPOSE: To determine the difference between the standard and a modified (zero-compression) Hansatome microkeratome head (Bausch & Lomb) in the incidence of epithelial defects. SETTING: Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany. METHODS: Ninety-three patients (186 eyes) with a mean age of 39.1 years +/- 9.5 (SD) having laser in situ keratomileusis (LASIK) in both eyes were enrolled in a prospective randomized study using intraindividual comparison. In 1 eye, the flaps were created with the Hansatome microkeratome using the standard Hansatome head and in the other eye, the flaps were created with a microkeratome head with a modified design (zero-compression head). Intraoperative evaluation of epithelial defects was done using a standardized protocol. Statistical evaluation was performed with McNemar and Bowker tests. RESULTS: Epithelial defects occurred in 21 eyes (22.6%) in which the standard head was used and in 2 eyes (2.1%) in which the zero-compression head was used. In the former group, 15 (16.1%) of the epithelial defects were larger than 1.5 mm(2); the remaining 6 (6.4%) were smaller than 1.5 mm(2). In the latter group, both epithelial defects were smaller than 1.5 mm(2); both patients also had an epithelial defect in the eye in which the standard Hansatome head was used. The difference between the 2 Hansatome heads in the incidence (P<.001, McNemar) and size (P<.001, Bowker) of the epithelial defects was statistically significant. CONCLUSIONS: The Hansatome microkeratome with a zero-compression head significantly reduced the occurrence of intraoperative epithelial defects. The change in the construction of the Hansatome head is a useful improvement in LASIK technology.

Comparison of a digital and a handheld infrared pupillometer for determining scotopic pupil diameter.

To compare a digital infrared pupillometer with a handheld infrared pupillometer for determining scotopic pupil size. Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany. In 100 eyes of 50 healthy individuals (mean age 38.8 years +/- 10.7 [SD]), the scotopic pupil size was measured with a digital (Procyon) and a handheld (Colvard) infrared pupillometer. After dark adaptation of 1 minute, measurements were performed with both devices by 2 examiners (E1 and E2). Agreement and repeatability were analyzed using a comparison method described by Bland and Altman. The mean scotopic pupil diameter was 5.90 +/- 0.97 mm (range 3.24 to 7.91 mm) with the Procyon and 5.78 +/- 0.98 mm (range 3.00 to 7.30 mm) with the Colvard pupillometer. The mean difference between the 2 devices was -0.01 mm (E1) and -0.24 mm (E2). The limits of agreement ranged from 2.84 (E1) to 3.24 (E2). The coefficients of repeatability were 0.64 (Procyon) and 1.16 (Colvard). The mean difference between E1 and E2 was -0.10 for the Procyon and 0.13 for the Colvard pupillometer. The limits of agreement ranged from 1.28 (Procyon) to 2.32 (Colvard). The digital infrared pupillometer (Procyon) demonstrated better repeatability and agreement in measuring scotopic pupil size than a handheld device (Colvard).