Characterization of Dysfunctional Lens Index and Opacity Grade in a Healthy Population.

This study enrolled 61 volunteers (102 eyes) classified into subjects < 50 years (group 1) and subjects ≥ 50 years (group 2). Dysfunctional Lens Index (DLI); opacity grade; pupil diameter; and corneal, internal, and ocular higher order aberrations (HOAs) were measured with the i-Trace system (Tracey Technologies). Mean DLI was 8.89 ± 2.00 and 6.71 ± 2.97 in groups 1 and 2, respectively, being significantly higher in group 1 in all and right eyes (both p < 0.001). DLI correlated significantly with age (Rho = −0.41, p < 0.001) and pupil diameter (Rho = 0.20, p = 0.043) for all eyes, and numerous internal and ocular root-mean square HOAs for right, left, and all eyes (Rho ≤ −0.25, p ≤ 0.001). Mean opacity grade was 1.21 ± 0.63 and 1.48 ± 1.15 in groups 1 and 2, respectively, with no significant differences between groups (p ≥ 0.29). Opacity grade significantly correlated with pupil diameter for right and all eyes (Rho ≤ 0.33, p ≤ 0.013), and with some ocular root-mean square HOAs for right and all eyes (Rho ≥ 0.23, p ≤ 0.020). DLI correlates with age and might be used complementary to other diagnostic measurements for assessing the dysfunctional lens syndrome. Both DLI and opacity grade maintain a relationship with pupil diameter and internal and ocular HOAs, supporting that the algorithms used by the device may be based, in part, on these parameters.

Efficacy of Perceptual Learning-Based Vision Training as an Adjuvant to Occlusion Therapy in the Management of Amblyopia: A Pilot Study.

A retrospective study was conducted to evaluate preliminarily the efficacy of perceptual learning (PL) visual training in medium-term follow-up with a specific software (Amblyopia iNET, Home Therapy Systems Inc., Gold Canyon, AZ, USA) for visual acuity (VA) and contrast sensitivity (CS) recovering in a sample of 14 moderate to severe amblyopic subjects with a previously unsuccessful outcome or failure with patching (PL Group). This efficacy was compared with that achieved in a patching control group (13 subjects, Patching 2). At one-month follow-up, a significant VA improvement in the amblyopic eye (AE) was observed in both groups, with no significant differences between them. Additionally, CS was measured in PL Group and exhibited a significant improvement in the AE one month after the beginning of treatment for 3, 6, 12, and 18 cycles/º (p = 0.003). Both groups showed long-lasting retention of visual improvements. A combined therapy of PL-based visual training and patching seems to be effective for improving VA in children with amblyopia who did not recover vision with patching alone or had a poor patching compliance. This preliminary outcome should be confirmed in future clinical trials.

Analysis of Intrasession Repeatability of Ocular Aberrometric Measurements and Validation of Keratometry Provided by a New Integrated System in Mild to Moderate Keratoconus.

PURPOSE: To evaluate the intrasession repeatability and validity of corneal curvature measurements provided by a new multifunctional device and to assess the intrasession repeatability of its ocular aberrometric measures. METHODS: This prospective study comprises 37 mild to moderate keratoconus eyes of 37 patients. In all cases, 3 repeated measures of corneal topography and ocular aberrometry were performed with the iDesign 2 system (iD2; Johnson & Johnson Vision Care Inc, Jacksonville, FL) and one keratometric measurement was performed with the intraocular lens-(IOL) Master 500 (Carl Zeiss Meditec Inc, Dublin, CA) and Sirius (CSO) (SIR) systems. RESULTS: The within-subject SD (Sw) was <0.50 D for all iD2 keratometric measurements, with intraclass correlation coefficient (ICC) >0.980. Sw and ICC for the keratometric axis were 2.60 degrees and 0.992, respectively. Concerning aberrations, all Sw values for high-order Zernike terms were ≤0.11 µm (ICC > 0.900), and all Sw values for refraction data were <0.75 D (ICC > 0.95), except for J45. No statistically significant differences were found between the devices in any keratometric parameter evaluated (P ≥ 0.222), but the limits of agreement between the devices were clinically relevant. The magnitude of K readings and astigmatism correlated significantly with the difference in these parameters between iD2 and SIR (0.432 ≤ r ≤ 0.489, P ≤ 0.041). CONCLUSIONS: The iD2 system provides consistent measures of keratometry and ocular aberrometry in eyes with mild to moderate keratoconus. Keratometric data obtained with this system in these eyes cannot be considered as interchangeable with data provided by intraocular lens-Master 500 and SIR.

Interchangeability of corneal curvature and asphericity measurements provided by three different devices.

AIM: To evaluate the interchangeability of keratometric and asphericity measurements provided by three measurement systems based on different optical principles. METHODS: A total of 40 eyes of 40 patients with a mean age of 34.1y were included. In all cases, a corneal curvature analysis was performed with IOL-Master (IOLM), iDesign 2 (ID2), and Sirius systems (SIR). Differences between instruments for flattest (K1) and steepest (K2) keratometric readings, as well as for magnitude and axis of corneal astigmatism were analyzed. Likewise, differences in asphericity (Q) between SIR and ID2 were also evaluated. RESULTS: Mean differences between devices for K1 were 0.20±0.21 (P<0.001), -0.12±0.36 (P=0.046) and -0.32±0.36 D (P<0.001) for the comparisons IOLM-SIR, IOLM-ID2 and SIR-ID2, respectively. The ranges of agreement for these comparisons between instruments were 0.41, 0.70, and 0.70 D. For K2, mean differences were 0.31±0.33 (P<0.001), -0.08±0.43 (P=0.265) and -0.39±0.38 D (P<0.001), with ranges of agreement of 0.65, 0.84, and 0.74 D. Concerning magnitude of astigmatism, ranges of agreement were in the limit of clinical relevance (0.49 D, P=0.011; 0.55 D, P=0.386; 0.43 D, P=0.05). In contrast, ranges of agreement were clinically relevant for astigmatic axis (26.68°, 33.83° and 18.37°, P≥0.121) and for Q between SIR and ID2 (0.16, P<0.001). CONCLUSION: The keratometric corneal power, astigmatic axis and asphericity measurements provide by the three systems evaluated cannot be considered as interchangeable, whereas measurements of corneal astigmatism obtained with SIR and ID2 can be considered as interchangeable for clinical purposes.

Differences in corneo-scleral topographic profile between healthy and keratoconus corneas.

PURPOSE: To evaluate the differences in corneo-scleral topographic profile between healthy and keratoconus eyes, and their potential diagnostic ability for keratoconus detection. METHODS: Prospective comparative study including 21 keratoconic eyes (11 patients) and 88 healthy eyes (88 patients). In all cases, a complete eye exam was performed including an evaluation of the corneo-scleral profile. The diagnostic ability of corneo-scleral topographic parameters to detect keratoconus was evaluated using the receiver operating characteristic (ROC) curve. RESULTS: A significant lower inferior tangent angle at limbus (ITA) was found in the keratoconic group compared to the control group (p = 0.024). Regarding sagittal heights, significant differences between groups were found in temporal sagittal height (TSH) for 11 mm (p = 0.040), 12 mm (p = 0.041) and 13 mm corneal chords (p = 0.040), difference between temporal and nasal sagittal heights (T-NSH) for 12 mm (p = 0.025) and 13 mm (p = 0.034), and maximum sagittal height (MaxSH) for 12 mm (p = 0.043), with higher values in keratoconus. In bilateral cases, these differences were not found when comparing with the least severe keratoconus eye. Statistical significance for the ROC curve was only found for ITA (p = 0.025), 12-mm (p = 0.048) and 13-mm TSH (p = 0.042), and 13-mm T-NSH (p = 0.037), with cutoff values associated to limited values of sensitivity and specificity. CONCLUSIONS: The corneo-scleral profile in keratoconus presents higher levels of asymmetry compared to healthy eyes, especially in eyes with moderate and advanced stages of the disease. The diagnostic accuracy of corneo-scleral topographic data alone for keratoconus detection is limited and must be used in conjunction with other clinical parameters.

Usefulness of bandage contact lenses in the immediate postoperative period after uneventful myopic LASIK.

PURPOSE: To determine the usefulness of a silicone-hydrogel bandage contact lens (BCL) in the immediate postoperative period after uneventful myopic laser in-situ keratomileusis (LASIK). METHODS: The study design was randomized but not masked and data collection was prospective. This study comprised 51 consecutive myopic eyes intervened by means of the LASIK technique to compensate their refractive error. Patients were randomly assigned to two different groups. The experimental group included 24 eyes of 12 patients that were fitted with a BCL immediately after the flap replacement. The control group included 27 eyes of 14 patients with no BCL. Patients were examined 24h after the surgery; the experimental group was analyzed immediately after the extraction of the BCL. Postoperative uncorrected distance visual acuity (UDVA) and postoperative topographic indexes were compared to baseline in both groups. RESULTS: The experimental group achieved worse results in the majority of the studied variables. Postoperative UDVA was worse in experimental group (p<0.01). Likewise, corneal asphericity (Q) was significantly higher in experimental group (p=0.024). Topographic indexes showed higher asymmetry in the corneal maps pertaining to experimental group. Specifically, the index of surface variance (ISV) (p=0.017) and index of vertical asymmetry (IVA) (p=0.031) were higher in experimental group. Also, the postoperative central corneal thickness (CCT) resulted in higher values for eyes pertaining to experimental group. CONCLUSIONS: The fitting of a silicone-hydrogel BCL after uneventful LASIK provokes morphological changes in the ocular structures that may lead to a worse UDVA secondary to a higher postoperative CCT and corneal edema.

Clinical outcomes at one year following keratoconus treatment with accelerated transepithelial cross-linking.

This study evaluated the clinical outcomes in keratoconus corneas following accelerated transepithelial corneal collagen cross-linking (CXL) (Avedro KXL® system, Waltham, MA, USA) over one year of follow-up. The mean depth of the demarcation line measured by optical coherence tomography (OCT) was 205.19 µm. One month after surgery, a non-statistically significant change was noted in sphere (P=0.18) and in spherical equivalent (P=0.17), whereas a significant improvement was observed in corrected distance visual acuity (P=0.04). A significant change was observed in topographic astigmatism (P=0.03) and posterior corneal a sphericity (P=0.04). Accelerated transepithelial CXL may be a useful technique for the management of progressive keratoconus.

Evaluation of the diagnostic ability of vector parameters characterizing the corneal astigmatism and regularity in clinical and subclinical keratoconus.

PURPOSE: To evaluate the diagnostic ability of the vector parameters ocular residual astigmatism (ORA), topography disparity (TD) and topographic astigmatism CorT (anterior and total) for the detection of clinical and subclinical keratoconus, and to develop a detection model based on them. METHODS: This study comprised a total of 61 keratoconus eyes (KC group), 19 eyes with subclinical keratoconus (SKC group) and 100 healthy eyes (control group). In all cases, a complete eye exam was performed including an analysis of the corneal structure with the Sirius system (Costruzione Strumenti Oftalmici, CSO). Likewise, the iASSORT software (ASSORT Pty) was used to calculate in all cases the vector parameters ORA, TD and CorT. RESULTS: Significant differences among groups were found in ORA, TD and CorT (anterior and total) (p<0.001). The diagnostic ability of ORA (cutoff 1.255 D, sensitivity/specificity 82%/92%) and TD (cutoff 1.035 D, sensitivity/specificity 78.5%/86%) for the detection of keratoconus was good, whereas anterior and total CorT showed a poorer diagnostic ability. ORA (cutoff 0.925 D, sensitivity/specificity 63.2%/77%) and TD (cutoff 0.710 D, sensitivity/specificity 74%/68%) showed an acceptable diagnostic ability for the detection of subclinical keratoconus, but anterior and total CorT did not. A detection model for subclinical keratoconus was obtained by logistic regression analysis involving TD, anterior corneal spherical aberration and posterior high order aberrations. CONCLUSIONS: The vector parameters ORA and TD are useful for the diagnosis of clinical and subclinical keratoconus. In this last condition, the combination of TD with corneal aberrometric data provides a consistent detection model.

Intra-session repeatability of iridocorneal angle measurements provided by a Scheimpflug photography-based system in healthy eyes.

PURPOSE: The purpose of this study was to evaluate intra-session repeatability of measurements of the iridocorneal angle at different meridians in the nasal and temporal areas in healthy eyes using the Sirius Scheimpflug photography-based system in glaucoma analysis mode. METHODS: A total of 43 eyes of 43 patients ranging in age from 36 to 79 years were enrolled in the study. All eyes received a comprehensive ophthalmologic examination including a complete anterior segment analysis with the Costruzione Strumenti Oftalmici [CSO] Sirius system. Three consecutive measurements of nasal and temporal angles at 0°, ±10°, ±20°, and ±30° meridians were obtained in order to assess the intra-session repeatability of iridocorneal angle measurements provided by the device using the glaucoma analysis mode. Within-subject standard deviation (Sw), coefficient of variation (CV), and intraclass correlation coefficient (ICC) values were calculated. RESULTS: The mean Sw was 1.07 ± 1.09°, 1.22 ± 1.53°, 0.66 ± 0.51°, 0.86 ± 0.57°, 0.68 ± 0.65°, 0.84 ± 0.68°, and 0.91 ± 0.70° at the temporal 30°, 20°, 10°, 0°, -10°, -20°, and -30° positions, respectively. Mean Sw was 3.13 ± 3.15°, 3.43 ± 3.63°, 2.75 ± 2.29°, 2.19 ± 1.55°, 1.90 ± 1.49°, 2.14 ± 1.74°, and 2.24 ± 2.06° at the temporal -30°, -20°, -10°, 0°, 10°, 20°, and 30° positions, respectively. Mean CV ranged from 1.36 ± 1.05 % (nasal 0° position) to 10.92 ± 13.95 % (nasal -20° position). ICC values ranged from 0.778 to 0.972. CONCLUSIONS: The glaucoma analysis mode of the Sirius system provides consistent measurements of the iridocorneal angle at different meridians in healthy eyes, with slightly less consistency for nasal measurements. It may be considered a clinically useful non-invasive technique for the detection of potentially occludable angles.

Clinical Validation of Adjusted Corneal Power in Patients with Previous Myopic Lasik Surgery.

Purpose. To validate clinically a new method for estimating the corneal power (P c ) using a variable keratometric index (n kadj) in eyes with previous laser refractive surgery. Setting. University of Alicante and Medimar International Hospital (Oftalmar), Alicante, (Spain). Design. Retrospective case series. Methods. This retrospective study comprised 62 eyes of 62 patients that had undergone myopic LASIK surgery. An algorithm for the calculation of n kadj was used for the estimation of the adjusted keratometric corneal power (P kadj). This value was compared with the classical keratometric corneal power (P k ), the True Net Power (TNP), and the Gaussian corneal power (P cGauss). Likewise, P kadj was compared with other previously described methods. Results. Differences between P cGauss and P c values obtained with all methods evaluated were statistically significant (p < 0.01). Differences between P kadj and P cGauss were in the limit of clinical significance (p < 0.01, loA [-0.33,0.60] D). Differences between P kadj and TNP were not statistically and clinically significant (p = 0.319, loA [-0.50,0.44] D). Differences between P kadj and previously described methods were statistically significant (p < 0.01), except with P cHaigisL (p = 0.09, loA [-0.37,0.29] D). Conclusion. The use of the adjusted keratometric index (n kadj) is a valid method to estimate the central corneal power in corneas with previous myopic laser refractive surgery, providing results comparable to P cHaigisL.

Clinical utility of ocular residual astigmatism and topographic disparity vector indexes in subclinical and clinical keratoconus.

PURPOSE: We aimed to characterize the distribution of the vector parameters ocular residual astigmatism (ORA) and topography disparity (TD) in a sample of clinical and subclinical keratoconus eyes, and to evaluate their diagnostic value to discriminate between these conditions and healthy corneas. METHODS: This study comprised a total of 43 keratoconic eyes (27 patients, 17-73 years) (keratoconus group), 11 subclinical keratoconus eyes (eight patients, 11-54 years) (subclinical keratoconus group) and 101 healthy eyes (101 patients, 15-64 years) (control group). In all cases, a complete corneal analysis was performed using a Scheimpflug photography-based topography system. Anterior corneal topographic data was imported from it to the iASSORT software (ASSORT Pty. Ltd), which allowed the calculation of ORA and TD. RESULTS: Mean magnitude of the ORA was 3.23 ± 2.38, 1.16 ± 0.50 and 0.79 ± 0.43 D in the keratoconus, subclinical keratoconus and control groups, respectively (p < 0.001). Mean magnitude of the TD was 9.04 ± 8.08, 2.69 ± 2.42 and 0.89 ± 0.50 D in the keratoconus, subclinical keratoconus and control groups, respectively (p < 0.001). Good diagnostic performance of ORA (cutoff point: 1.21 D, sensitivity 83.7 %, specificity 87.1 %) and TD (cutoff point: 1.64 D, sensitivity 93.3 %, specificity 92.1 %) was found for the detection of keratoconus. The diagnostic ability of these parameters for the detection of subclinical keratoconus was more limited (ORA: cutoff 1.17 D, sensitivity 60.0 %, specificity 84.2 %; TD: cutoff 1.29 D, sensitivity 80.0 %, specificity 80.2 %). CONCLUSION: The vector parameters ORA and TD are able to discriminate with good levels of precision between keratoconus and healthy corneas. For the detection of subclinical keratoconus, only TD seems to be valid.

Comparative analysis of the visual performance and aberrometric outcomes with a new hybrid and two silicone hydrogel multifocal contact lenses: a pilot study.

BACKGROUND: The aim was to evaluate the visual performance achieved with a new multifocal hybrid contact lens and to compare it with that obtained with two other currently available multifocal soft contact lenses. METHODS: This pilot prospective comparative study comprised a total of 16 presbyopic eyes of eight patients ranging in age from 43 to 58 years. All patients were fitted with three different models of multifocal contact lens: Duette multifocal (SynergEyes), Air Optix AQUA multifocal (Alcon) and Biofinity multifocal (CooperVision). Fittings were performed randomly in each patient according to a random number sequence, with a wash-out period between fittings of seven days. At two weeks post-fitting, visual, photopic contrast sensitivity and ocular aberrometry were evaluated. RESULTS: No statistically significant differences were found in distance and near visual acuity achieved with the three different types of multifocal contact lens (p ≥ 0.05). Likewise, no significant differences between lenses were found in the monocular and binocular defocus curve (p ≥ 0.10). Concerning contrast sensitivity, better monocular contrast sensitivities for 6, 12 and 18 cycles per degree were found with the Duette and Air Optix multifocal compared to Biofinity (p = 0.02). Binocularly, differences between lenses were not significant (p ≥ 0.27). Furthermore, trefoil aberration was significantly higher with Biofinity multifocal (p < 0.01) and Air Optix (p = 0.01) multifocal compared to Duette. CONCLUSIONS: The Duette multifocal hybrid contact lens seems to provide similar visual quality outcomes in presbyopic patients with low corneal astigmatism, when compared with other soft multifocal contact lenses. This preliminary result should be confirmed in studies with larger samples.

Influence of the difference between corneal and refractive astigmatism on LASIK outcomes using solid-state technology.

PURPOSE: To evaluate the influence of the difference between preoperative corneal and refractive astigmatism [ocular residual astigmatism (ORA)] on outcomes obtained after laser in situ keratomileusis (LASIK) surgery for correction of myopic astigmatism using the solid-state laser technology. METHODS: One hundred one consecutive eyes with myopia or myopic astigmatism of 55 patients undergoing LASIK surgery using the Pulzar Z1 solid-state laser (CustomVis Laser Pty Ltd, currently CV Laser) were included. Visual and refractive changes at 6 months postoperatively and changes in ORA and anterior corneal astigmatism and posterior corneal astigmatism (PCA) were analyzed. RESULTS: Postoperatively, uncorrected distance visual acuity improved significantly (P < 0.01). Likewise, refractive cylinder magnitude and spherical equivalent were reduced significantly (P < 0.01). In contrast, no significant changes were observed in ORA magnitude (P = 0.81) and anterior corneal astigmatism (P = 0.12). The mean overall efficacy and safety indices were 0.96 and 1.01, respectively. These indices were not correlated with preoperative ORA (r = -0.15, P = 0.15). Furthermore, a significant correlation was found between ORA (r = 0.81, P < 0.01) and PCA postoperatively, but not preoperatively (r = 0.12, P = 0.25). Likewise, a significant correlation of ORA with manifest refraction was only found postoperatively (r = -0.38, P < 0.01). CONCLUSIONS: The magnitude of ORA does not seem to be a predictive factor of efficacy and safety of myopic LASIK using a solid-state laser platform. The higher relevance of PCA after surgery in some cases may explain the presence of unexpected astigmatic residual refractive errors.

New-generation hybrid contact lens for the management of extreme irregularity in a thin cornea after unsuccessful excimer laser refractive surgery.

PURPOSE: To report a very successful outcome obtained with the fitting of a new-generation hybrid contact lens of reverse geometry in a thin cornea with extreme irregularity due to the presence of a central island after unsuccessful myopic excimer laser refractive surgery. METHODS: A 32-year-old man attended to our clinic complaining of very poor vision in his right eye after bilateral laser in situ keratomileusis (treatment or surgery) for myopia correction and some additional retreatments afterward. After a comprehensive ocular evaluation, contact lens fitting with a reverse geometry hybrid contact lens (SynergEyes PS, SynergEyes, Carlsbad, CA) was proposed as a solution for this case. Visual, refractive, and ocular aberrometric outcomes with the contact lens were evaluated. RESULTS: Distance visual acuity improved from a prefitting uncorrected value of 20/200 to a postfitting corrected value of 20/16. Prefitting manifest refraction was +6.00 sphere and -3.00 cylinder at 70°, with a corrected distance visual acuity of 20/40. Higher order root mean square for a 5-mm pupil changed from a prefitting value of 1.45 to 0.34 µm with the contact lens. The contact lens wearing was reported as comfortable, and the patient was very satisfied with this solution. CONCLUSIONS: The SynergEyes PS contact lens seems to be an excellent option for the visual rehabilitation of corneas with extreme irregularity after myopic excimer laser surgery, minimizing the level of higher order aberrations and providing an excellent visual outcome.

Ocular residual astigmatism and topographic disparity vector indexes in normal healthy eyes.

PURPOSE: To define a range of normality for the vectorial parameters Ocular Residual Astigmatism (ORA) and topography disparity (TD) and to evaluate their relationship with visual, refractive, anterior and posterior corneal curvature, pachymetric and corneal volume data in normal healthy eyes. METHODS: This study comprised a total of 101 consecutive normal healthy eyes of 101 patients ranging in age from 15 to 64 years old. In all cases, a complete corneal analysis was performed using a Scheimpflug photography-based topography system (Pentacam system Oculus Optikgeräte GmbH). Anterior corneal topographic data were imported from the Pentacam system to the iASSORT software (ASSORT Pty. Ltd.), which allowed the calculation of the ocular residual astigmatism (ORA) and topography disparity (TD). Linear regression analysis was used for obtaining a linear expression relating ORA and posterior corneal astigmatism (PCA). RESULTS: Mean magnitude of ORA was 0.79 D (SD: 0.43), with a normality range from 0 to 1.63D. 90 eyes (89.1%) showed against-the-rule ORA. A weak although statistically significant correlation was found between the magnitudes of posterior corneal astigmatism and ORA (r=0.34, p<0.01). Regression analysis showed the presence of a linear relationship between these two variables, although with a very limited predictability (R(2): 0.08). Mean magnitude of TD was 0.89D (SD: 0.50), with a normality range from 0 to 1.87D. CONCLUSION: The magnitude of the vector parameters ORA and TD is lower than 1.9D in the healthy human eye.

Pilot study of hyperopic LASIK using the solid-state laser technology.

BACKGROUND: To evaluate and report the visual, refractive, and aberrometric outcomes of LASIK for the correction of low to moderate hyperopia in a pilot group using a commercially available solid-state laser METHODS: Prospective pilot study including 11 consecutive eyes with low to moderate hyperopia of six patients undergoing LASIK surgery using the Pulzar Z1 solid-state laser (CustomVis Laser Pty Ltd., currently CV Laser). Visual, refractive, and aberrometric changes were evaluated. Potential complications were evaluated as well. Mean follow-up time was 6.6 months (range, 3 to 11 months). RESULTS: A significant improvement in LogMAR uncorrected distance visual acuity (UDVA) was observed postoperatively (p = 0.01). No significant change was detected in LogMAR corrected distance visual acuity (CDVA) (p = 0.21). Postoperative LogMAR UDVA was 0.1 (about 20/25) or better in ten eyes (90.9 %). Mean overall efficacy and safety indices were 1.03 and 1.12. Postoperatively, no losses of lines of CDVA were observed. Postoperative spherical equivalent was within ± 1.00 D in ten eyes (90.9 %). With regard to aberrations, no statistically significant changes were found in higher order and primary coma RMS postoperatively (p ≥ 0.21), and only minimal but statistically significant negativization of primary spherical aberration (p = 0.02) was observed. No severe complications were observed. CONCLUSION: LASIK surgery using the solid-state laser technology seems to be a useful procedure for the correction of low to moderate hyperopia, with minimal induction of higher order aberrations.

Clinical validation of an algorithm to correct the error in the keratometric estimation of corneal power in normal eyes.

PURPOSE: To validate clinically in a normal healthy population an algorithm to correct the error in the keratometric estimation of corneal power based on the use of a variable keratometric index of refraction (n(k)). SETTING: Medimar International Hospital (Oftalmar) and University of Alicante, Alicante, Spain. DESIGN: Case series. METHODS: Corneal power was measured with a Scheimpflug photography-based system (Pentacam software version 1.14r01) in healthy eyes with no previous ocular surgery. In all cases, keratometric corneal power was also estimated using an adjusted value of n(k) that is dependent on the anterior corneal radius (r(1c)) as follows: n(kadj) = -0.0064286 r(1c) +1.37688. Agreement between the Gaussian (P(c)(Gauss)) and adjusted keratometric (P(kadj)) corneal power values was evaluated. RESULTS: The study evaluated 92 eyes (92 patients; age range 15 to 64 years). The mean difference between P(c)(Gauss) and P(kadj) was -0.02 diopter (D) ± 0.22 (SD) (P=.43). A very strong, statistically significant correlation was found between both corneal powers (r = .994, P<.01). The range of agreement between P(c)(Gauss) and P(kadj) was 0.44 D, with limits of agreement of -0.46 and +0.42 D. In addition, a very strong, statistically significant correlation of the difference between P(c)(Gauss) and P(kadj) and the posterior corneal radius was found (r = 0.96, P<.01). CONCLUSION: The imprecision in the calculation of corneal power using keratometric estimation can be minimized in clinical practice by using a variable keratometric index that depends on the radius of the anterior corneal surface. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.