Evdoxia Terzi

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.

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.

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

Purpose: To compare a digital infrared pupillometer with a handheld infrared pupillometer for determining scotopic pupil size. Setting: Department of Ophthalmology, Johann Wolfgang Goethe‐University, Frankfurt am Main, Germany. Methods: 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. Results: 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). Conclusions: The digital infrared pupillometer (Procyon) demonstrated better repeatability and agreement in measuring scotopic pupil size than a handheld device (Colvard).

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 pupil‐ lometer, 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.

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 mm2; the remaining 6 (6.4%) were smaller than 1.5 mm2. In the latter group, both epithelial defects were smaller than 1.5 mm2; 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.

Intraocular lenses for the correction of refraction errors. Part II. Phakic posterior chamber lenses and refractive lens exchange with posterior chamber lens implantation

ZusammenfassungIm vorliegenden Übersichtsartikel wird der derzeitige Stand der Intraokularlinsenchirurgie zur Korrektur von Refraktionsfehlern dargestellt. Man unterscheidet zwischen additiver Chirurgie mit Kunstlinsenimplantation ohne Extraktion der kristallinen Linse [phake Intraokularlinse (PIOL)] und der Entfernung der natürlichen Linse mit Implantation einer Kunstlinse [refraktiver Linsenaustausch (RLA)]. Die phaken Intraokularlinsen (PIOL) werden in kammerwinkelgestütze und irisgetragene Vorderkammerlinsen sowie sulkusfixierte Hinterkammerlinsen unterteilt. Die Implantation der phaken IOL hat sich als effektives, sicheres, vorhersagbares und stabiles Verfahren zur Korrektur von höheren Ametropien erwiesen. Komplikationen sind selten und zwischen den 3 verschiedenen PIOL-Typen unterschiedlich, bei den Hinterkammerlinsen handelt es sich um Kataraktentwicklung und Pigmentdispersion. Der refraktive Linsenaustausch (RLA) wird bevorzugt dann bei hohen Ametropien eingesetzt, wenn keine Akkommmodationsleistung der natürlichen Linse mehr zu erwarten ist. Zu den Komplikationsmöglichkeiten des myopen RLA gehören die Netzhautablösung, zu denen des hyperopen RLA operative Schwierigkeiten bedingt durch das kurze Vordersegment.AbstractIn this overview, the current status of intraocular lens surgery to correct refractive error is reviewed. The interventions are divided into additive surgery with intraocular lens implantation without extraction of the crystalline lens (phakic intraocular lens, PIOL) or removal of the crystalline lens with implantation of an IOL (refractive lens exchange, RLE). Phakic IOLs are constructed as angle-supported or iris-fixated anterior chamber lenses and posterior chamber lenses which are fixated in the ciliary sulcus. The implantation of phakic IOLs has been demonstrated to be an effective, safe, predictable and stable procedure to correct higher refractive errors. Complications are rare and differ for the three types of PIOL; for posterior chamber lenses these are mainly cataract formation and pigment dispersion. RLE is preferable in cases of high ametropia in which the natural lens has lost its accommodative effect. The main complications for myopic RLA include retinal detachment, while hyperopic refractive lens exchange may be associated with surgical problems in the narrower anterior eye segment.

Quality of Vision After Refractive Surgery

After inventing, evaluating and perfecting refractive surgical procedures in recent years, one of the current efforts is to focus on “quality of vision” after various surgical interventions. The number of surgical procedures to correct refractive errors is steadily increasing, old procedures are replaced by newer, mostly better ones, the complication rate is decreasing, and the results of each of the established procedures are improving with more experience, better technology and scientific evaluation. Success or failure of refractive procedures, defined by criteria like safety, efficacy, stability and predictability [13] is based on Snellen acuity. However, some patients present with anatomically perfect results and excellent visual outcome with respect to these criteria measured in Snellen acuity,but complain of visual disturbances like decreased contrast, different colour perception, glare, halos or simply “bad vision”. In some cases the problem can be explained, e.g. by residual astigmatism or a decentred ablation zone in excimer surgery or the optic diameter of a phakic intraocular lens implant on halo perception, in other cases an immediate answer is not found. On the contrary, in retrospect there should have been problems (6mm ablation zone for LASIK with 7-mm scotopic pupil size diameter) that fortunately have never occurred. Therefore determining the outcome seems to be more complex. Why do only some patients complain? Are some complaints associated with simple residual refractive error or are there other much more sophisticated reasons for visual disturbances yet unknown to the patients [14]? The present chapter gives an overview of how quality of vision could be defined and determined and summarises typical disturbances which are known to date.