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Background: Corneal Scheimpflug tomography is a commonly used non-invasive imaging technique., Objectives: This review article summarizes the principles of the technique and recent results from the literature with a focus on keratoconus diagnostics., Material and Methods: Review of the literature, own data and expert opinions., Results: Corneal Scheimpflug tomography allows topography of the anterior and posterior surfaces as well as spatially resolved pachymetry and densitometry. Measurements obtained with currently available systems are highly reproducible but not interchangeable. Combining topographic and pachymetric data allows a highly sensitive and specific diagnostic modality for the early diagnosis of keratoconus., Conclusions: Due to the versatility, precision and easy handling, corneal Scheimpflug tomography is the most important imaging technique for the anterior segment of the eye.

Background: For the detection of early stages of keratoconus (KC) several metrics have been developed in recent years. The aim of the study was to assess the suitability of keratometric indices to discriminate between eyes with early and subclinical KC from normal eyes., Methods: From 33 eyes with early KC (group 1), 16 eyes with subclinical KC (group 2) und 121 normal eyes (group 3) the following metrics were computed from axial keratometric data: central keratometry (cK), astigmatism (AST), paracentral inferior-superior keratometric difference (PISD), skew of the steepest axes index (SRAX), the KISA% index, a discriminant function from the KISA% parameters AST, cK, PISD and SRAX (DKISA), corneal C(3) (-1) and a discriminant function from corneal Zernike coefficients (1(st)-7(th) order, pupil diameter 6 mm). The discriminative ability of these metrics between KC and normal eyes was assessed using receiver operating characteristic (ROC) curves and measuring the area under the curve (A (z)ROC)., Results: Applying the published criteria, the Rabinowitz-McDonnell test (cK and PISD) and KISA% lacked sensitivity. Adjustment of critical values using ROC curve analysis improved the discriminative ability. The PISD (A (z)ROC 1 versus 3: 1, 2 versus 3: 0.947) and C(3) (-1) (A (z)ROC 1 and 0.98, respectively) metrics were the two single parameters with the highest discriminative ability. By weighting KISA parameters and Zernike coefficients with discriminant analyses, 100% of group 1 eyes (DKISA) and 96.7% of group 2 eyes (DA) were correctly classified., Conclusion: After lowering the critical values the keratometric indices yielded a high discriminative ability for the detection of early KC stages. However, the excellent classification rates for wavefront-based metrics were not achieved.

Objective: The purpose of this study was to evaluate a novel technique for the correction of postoperative astigmatism after penetrating keratoplasty with the use of the femtosecond laser creating astigmatic keratotomies (femto-AK) in the scope of a retrospective case series., Methods: Clinical data of ten eyes of nine patients with high residual astigmatism after penetrating keratoplasty undergoing paired femto-AK using a 60-kHz femtosecond laser (IntraLase™, AMO) were analyzed. A new software algorithm was used to create paired arcuate cuts deep into the donor corneal button with different cut angles. Target values were refraction, uncorrected visual acuity, best corrected visual acuity, topographic data (Orbscan®, Bausch & Lomb, Rochester, NY, USA), and corneal wavefront analysis using Visual Optics Lab (VOL)-Pro 7.14 Software (Sarver and Associates). Vector analysis was performed using the Holladay, Cravy and Koch formula. Statistical analysis was performed to detect significances between visits using Student's t test., Results: All procedures were performed without any major complications. The mean follow-up was 13 months. The mean patient age was 48.7 years. The preoperative mean uncorrected visual acuity (logMAR) was 1.27, best corrected visual acuity 0.55, mean subjective cylinder -7.4 D, and mean topometric astigmatism 9.3 D. The postoperative mean uncorrected visual acuity (logMAR) was 1.12, best corrected visual acuity 0.47, mean subjective cylinder -4.1 D, and mean topometric astigmatism 6.5 D. Differences between corneal higher order aberrations showed a high standard deviation and were therefore not statistically significant., Conclusions: Astigmatic keratotomy using the femtosecond laser seems to be a safe and effective tool for the correction of higher corneal astigmatisms. Due to the biomechanical properties of the cornea and missing empirical data for the novel femto-AK technology, higher numbers of patients are necessary to develop optimal treatment nomograms.

Contrast perception is an important visual function. Contrast sensitivity (CS) is affected by to optical reasons (aberrations, scatter, diffraction) or neural dysfunction (e.g., glaucoma, optic nerve diseases). In clinical practice the measurement of CS is relevant for disease monitoring, expert opinions, roadworthiness assessment, and recruitment screening. Furthermore, CS testing is often required in studies assessing optical quality, e.g., cataract or refractive surgery. Adding an appropriate glare source allows measurement of the glare-induced loss of CS (disability glare). Compared to high-contrast acuity, CS is more variable and strongly depends on the type of test, illumination, test strategy, and contrast definition; ceiling effects are quite common among many tests. Maximal standardization is important, especially for follow-up exams. In summary, CS testing cannot be regarded as a routine test. The present report by the DOG commission for quality management of psychophysical assessment covers the physiological background, testing principles, and strategies and presents a tabular overview of common tests.

In recent years, wavefront analysis has ceased to be purely a laboratory application and emerged as a method used in ophthalmological diagnosis. This development has been promoted mainly by the widespread use of wavefront-guided LASIK (laser in situ keratomileusis). However, aberrometry is still not a common diagnostic technique, and for many ophthalmologists interpretation of the results is difficult. The second part of this serial paper reviews findings that are relevant for the ophthalmological community and highlights current scientific applications in this area.

In recent years, wavefront analysis has emerged from a pure laboratory application to an ophthalmological diagnostic method. This development was promoted mainly by the widespread use of wavefont-guided LASIK. However, aberrometry is still not a common diagnostic technique and the results of measurements are difficult to understand and to interpret for many ophthalmologists. The first part of this 2-part series summarizes the basics of wavefront errors, aberrometry and wavefront analysis to give a comprehensive overview for the interested ophthalmologist and clinical scientist. The second part will review such findings that are relevant for the ophthalmological community and highlight current scientific applications.

Purpose: To investigate the clinical impact of the postoperative ocular wavefront error (WFE) on subjective quality of vision (SQV) after LASIK., Method: Forty-one myopic eyes of 21 patients underwent uneventful LASIK (median -4.63 D). Preoperatively and 1 month postoperatively, WFE measurements were performed and overall SQV was assessed for two lighting conditions (photopic and mesopic) with a questionnaire. Three different WFE representations were computed for a pupil diameter of 6 mm: (1) the visual quality metric VSOTF (visual Strehl ratio based on the optical transfer function), (2) RMS (root mean square) values of the Zernike orders 2-5, and (3) individual Zernike coefficient for orders 2-5. The impact of the postoperative WFE on SQV was calculated using linear regression analysis., Results: For photopic conditions R(2) was 0.24 for model 1 (VSOTF), 0.31 for model 2 (RMS values), and 0.29 for model 3 (Zernike coefficients). Second-and fifth-order aberrations had significant influence on SQV. For mesopic conditions, results were similar., Conclusion: Subjective quality of vision after wavefront-guided LASIK could be explained partially by the ocular WFE.

Background: The entity of subclinical keratoconus (SKC) has not been defined sufficiently yet. The aim of the study was to describe ocular wavefront aberrations of clinically inconspicuous fellow eyes in patients with early keratoconus (KC) as a model of SKC and to assess the feasibility of higher-order wavefront analysis to discriminate eyes with SKC from normal eyes., Methods: This prospective study included eight clinically inconspicuous fellow eyes of eight patients with newly detected KC in the contralateral eye and a paracentral inferior-superior difference (PISD) <1.4 D. In total, 15 eyes of 12 patients with newly diagnosed KC and a PISD >1.4 D were included as positive controls and 71 healthy eyes of 40 patients served as negative controls. The wavefront error was measured in all eyes with a Hartmann-Shack sensor. Discriminant analysis was performed with input from ocular HOA data and PISD. Receiver operating characteristic (ROC) curves were plotted for PISD, single Zernike coefficients, and for the output values of the discriminant functions to investigate their usefulness for discrimination between SKC eyes, early KC eyes, and healthy controls., Results: There were significant differences between inconspicuous fellow eyes (group 2) and controls (group 3) for PISD, for the coefficients Z3(-3), Z3(-1), Z4(0) and Z5(-1), and for the output values of the discriminant functions. The latter discriminated between groups 2 and 3 with maximum sensitivity and specificity (A(z) ROC=1), whereas discriminative ability was considerably lower for single Zernike coefficients., Conclusion: Single Zernike coefficients did not appear to be useful for the detection of SKC. Using discriminant analysis, from PISD and higher-order Zernike coefficients a metric with very high discriminative ability between normal and SKC eyes could be constructed.

Correction of myopia, hyperopia and astigmatism within its indicated margin by means of refractive corneal surgical procedures such as LASIK and surface ablation (e.g. PRK) is one of the standard procedures in ophthalmology. Now that advances in the fields of surgical techniques and the technical devices employed have further progressed in terms of safety and predictability, research also focuses on optical quality. "Optical quality" is not a clearly defined parameter, but can be captured indirectly by means of directly measured data. One has to start with the anatomical properties of the eye, which determine the optical images on the retinal level. The quality of the retinal image influences the eye's function, i.e. acuity and contrast perception. Finally, there is the subjective perception of the image we receive. "Optical quality" as such is reflected by the patient's evaluation of this image perception. Three phenomena are especially responsible for deterioration of the quality of the retinal image: diffraction, aberrations and dispersion. Some of the methods for measuring optical quality are subjective questionnaires, functional testing procedures for measuring visual acuity and contrast sensitivity, optical measuring procedures for the determination of optical quality, as well as biomicroscopy, aberrometry and corneal topography for assessing anatomical changes.

Background: The purpose of the present study was to evaluate a computerized test for measurement of contrast sensitivity thresholds under variable ambient and glare luminance levels., Methods: A total of 40 eyes of 40 healthy subjects were examined with the FF-CATS and the Functional Acuity Contrast Test (FACT) at 0.167 cd/m(-2) (mesopic) and 167 cd/m(-2) (photopic). Measurements were performed twice with and without glare in a randomized fashion. Tests were evaluated according to three criteria: (1) repeatability, (2) discriminative ability, and (3) validity., Results: The FF-CATS showed a higher discriminative ability between the two groups compared to the FACT charts. Under photopic conditions, the COR value was 0.39 for the FF-CATS and 0.26 for the FACT charts; under mesopic illumination, the COR value for the FF-CATS was 0.46 and 0.36 for the FACT charts., Conclusion: The FF-CATS is a reliable, sensitive, valid, and flexible test system for the determination of visual acuity and contrast sensitivity thresholds under variable ambient and glare luminance conditions.

Background: The implantation of aspherical IOLs with negative spherical aberration should equalize the positive spherical aberration of the cornea. The aim of our study was the intraindividual comparison of higher order aberrations (HOA) after implantation of an aspherical and spherical IOL., Patients and Methods: In ten patients we randomly implanted an aspherical IOL in one eye and a spherical IOL in the other. After 3 months, we used a Hartmann-Shack sensor to measure total HOA, 3rd to 5th order as well as spherical aberration Z4.0, in mydriasis. We compared all aberrations intraindividually for pupil diameters of 3.5-6 mm., Results: For both IOLs, all aberrations rose with increasing pupil diameter. However, after implantation of the aspherical IOL total HOA, 4th order and spherical aberration Z4.0 were lower, for 4th order aberration and Z4.0 even significantly. For 3rd and 5th order aberrations, there was no difference between both IOLs., Conclusions: With implantation of aspherical IOLs, total HOA, 4th order and spherical aberration Z4.0 could be reduced compared to spherical IOLs.

Background: The purpose of the present study is to demonstrate the change of higher order wavefront aberrations (HOA) after implantation of an iris claw pIOL., Methods: Thirteen eyes of seven patients were examined preoperatively and 1 month after implantation of an Artisan lens. The mean preoperative spherical equivalent was -10.69+/-1.92 D (-7.63 to -14.88 D). The diameter of the IOL optic was 6 mm and the lens was inserted though a tunnel incision at 12 o'clock. The root mean square (RMS) wavefront error was computed for all aberrations of the third to fifth order for pupil diameters of 3.5 and 6 mm., Results: On average, HOA RMS changed for a 3.5 mm pupil by 0.037+/-0.089 microm (6 mm pupil: 0.405+/-0.245 microm). Third-order aberrations changed by 0.031+/-0.098 microm (0.320+/-0.269 microm). For both pupil diameters, a notable increase of Z 3,-3 of 0.117+/-0.085 microm (0.596+/-0.350 microm) could be observed depending on the distance between the limbus and incision. Fourth-order aberrations changed on average by 0.018+/-0.037 microm (0.280+/-0.143 microm), namely Z 4,0 increased by 0.025+/-0.034 microm (0.296+/-0.164 microm)., Conclusion: After implantation of the Artisan lens HOA increased slightly. Particularly induction of Z 3,-3 and Z 4,0 contribute to the increase of HOA. The induction of trefoil ( Z 3,-3) is a result of the incision, whereas the increase of spherical aberration is due to the implant.

The present review describes the current status of wavefront-guided corneal surgery and up-to-date results. Wavefront-guided LASIK procedures performed to date achieved uncorrected vision of i.o or better in a larger number of patients than with conventional LASIK surgery, but the "eagle eye" has remained the exception. In part of the patients reductions of higher order aberrations could be obtained, but in the majority of ca-ses an increase was observed. This increase was however less than with conventional LASIK surgery. Correction of higher order aberrations has not yet been perfected since the predictability of corrections appears to be deserving of improvement on the one hand and aberrations are still induced by the technique on the other hand.

Purpose: The purpose of this investigation was to evaluate the safety, efficacy, predictability, stability and complications of LASIK for the treatment of hyperopia and hyperopic astigmatism using a scanning spot excimer laser., Patients and Methods: A total of 64 consecutive LASIK operations (37 patients, mean age 41 years, range 22-68 years) have been evaluated. The Hansatome microkeratome producing a superior hinge (flap diameter 9.5 mm) and a scanning spot excimer laser with an optical zone of 6.0 mm were used. Examinations were performed preoperatively, after 1 day, 7 days, 1 month, 4 and 12 months., Results: One year after the primary procedure only 1 eye lost 2 or more lines of best-corrected visual acuity, 91% were within +/-1 line and 4 eyes gained 2 lines. Of these eyes 50 (86%) reached an uncorrected visual acuity of > or=0.5, 32 (55%) > or=0.8, 16 (28%) > or=1.0, 24 eyes (41%) needed a refractive correction of +/-0.5 D, 44 eyes (76%) of +/-1.0 D and 55 eyes (95%) of +/-2.0 D. The mean spherical equivalent after 1 year was +0.17+/-0.85 D., Conclusions: LASIK is suitable for the correction of hyperopia (up to a maximum of +5 D) and for hyperopic astigmatism (up to a maximum of -5 D). However, results were better in lower hyperopia (up to +3 D) than in the moderate hyperopia. The refractive results showed overall a good stability during the 12-month study period, but higher regression occurred in a few cases.

Background: Diffuse lamellar keratitis (DLK) is a sterile inflammation after lamellar corneal surgery. A clinical staging for DLK was recently set up. In this observational case series, the clinical and confocal microscopic findings of stages 1-3 are reported., Methods: Six eyes of six patients (three eyes with DLK stage 1, two eyes with DLK stage 2, and one eye with DLK stage 3) were examined by slit lamp biomicroscopy and confocal microscopy., Results: In all cases, confocal microscopy showed an infiltration of inflammatory cells into the anterior stroma and the flap interface. The number of cells varied between the eyes with DLK stage 1, and both stage 2 corneas had dense infiltrates. In the eye with stage 3 DLK, an aggregation of decayed cells, most likely granulocytes, was noticed clinically and by confocal microscopy., Conclusions: The DLK stages represent different clinical intensities of interface inflammation after LASIK. While stages 1 and 2 have a similar confocal microscopic appearance, stage 3 is a result of aggregation of a high amount of inflammatory cells.

Purpose: Recently laser-in-situ-keratomileusis (LASIK) has been increasingly used to correct refractive errors. The purpose of this investigation was to evaluate the safety, efficacy, predictability, stability and complications using the scanning spot excimer LASIK technology., Patients and Methods: The results of 100 consecutive LASIK operations carried out between 2/1998 and 2/1999 on 60 patients (mean age 37 years, range 20-55 years) have been evaluated. The Hansatome microkeratome with a superior hinge (flap diameter: 9.5 mm) and a scanning spot excimer laser (Technolas C-Lasik 217) were used in all cases. The mean spherical equivalent of the subjective manifest refraction was -6.96 +/- 2.87 diopters (D), the mean sphere was -6.47 +/- 2.71 D and the mean astigmatism was -0.98 +/- 0.94 D. In 6% of the eyes preoperative visual acuity was not better than 20/40. Examinations were performed preoperatively, after 1 and 7 days, after 1,4 and 12 months. Safety, efficacy, predictability, stability and complications were calculated using the datagraph software (version 1.11)., Results: All 100 eyes were examined after 1 day and 1 week, 96 after 1 month, 95 after 4 months and 92 after 1 year. Following 1 year none of the eyes lost 2 or more lines of best corrected visual acuity, 99% were within +/- 1 line and 1% gained 2 lines (safety index 1.03). In 92% of all eyes an uncorrected visual acuity of > or = 0.5 was reached, in 77% > or = 0.8 and in 51% > or = 1.0 (efficacy index 0.89). For 60 eyes (65.21%) a refractive correction of +/- 0.5 D was necessary, for 82 eyes (89.13%) +/- 1.0 D and for 91 eyes (98.91%) +/- 2.0 D. The mean spherical equivalent after 1 year was -0.15 +/- 1.31 D. Between 1 and 12 months a mean regression of -0.14 D occurred. On the request of the patients, 5 eyes were retreated during the study period for under- or over-correction. Complications due to the microkeratome did not occur. Corneal infections were not observed, a diffuse lamellar keratitis (DLK) was seen in 12 cases, but all cases healed with no loss of visual acuity. In 7 eyes a slight decentration of the ablation was observed using corneal topography, which in one case caused an increase in glare sensitivity., Conclusions: LASIK with superior hinge and scanning spot excimer photoablation is suitable for the correction of myopia (up to a maximum of -12 D) and for myopic astigmatism (up to a maximum of -5 D). The refractive results showed a high stability during the 12-month study period but there is still room for improvement of the predictability.