Posterior Corneal Aberrations Research Articles

Limitations of and Solutions to Using 6 mm Corneal Spherical Aberration and Q Value after Laser Refractive Surgery.

This study aimed to evaluate the spherical aberration (SA) in different corneal areas before and after femtosecond laser-assisted in situ keratomileusis (fLASIK) and transepithelial photorefractive keratectomy (tPRK), with the goal of identifying the limitations of and potential improvements in using SA within a 6 mm area. The study included 62 patients who underwent fLASIK and tPRK. Complete eye examinations including keratometry, corneal epithelial thickness, central corneal thickness, and topography were performed preoperatively and postoperatively. Anterior, posterior, and total corneal aberrations were measured preoperatively and three months postoperatively, with pupil diameters ranging from 2 to 8 mm. In the fLASIK group, compared to the preoperative SA, the anterior and total SA increased postoperatively in the 6 and 7 mm areas. In the tPRK group, meanwhile, the anterior and total SA of the 5 mm or larger areas increased postoperatively. An area of 6 mm or larger showed an increase in correlation with the changes in Q value and refractive correction. As the corneal SA and asphericity in the 6 mm zone cannot specifically demonstrate the status of areas smaller than 6 mm or changes in the optical zone after laser refractive surgery, comparison with normal values in various areas of the cornea is necessary.

Posterior corneal surface and anterior chamber changes after Small incision lenticule extraction and Femtosecond laser‐assisted laser in‐situ keratomileusis

AbstractWe aimed to evaluate the posterior corneal and anterior chamber changes following small incision lenticule extraction (SMILE) and femtosecond laser‐assisted laser in situ keratomileusis (FS‐LASIK). This retrospective study included 93 eyes for SMILE and 228 eyes for FS‐LASIK. Posterior corneal curvature, anterior chamber biometrics, and posterior corneal aberrations preoperatively and at 1 week and 3 months after surgery were evaluated. The correlation between surgical‐related factors and posterior corneal morphology changes, posterior corneal morphology changes, and posterior corneal aberration alterations were determined. There was an increase in mean posterior corneal radius (PCC R) and flat posterior corneal radius (PCC R1) and decrease in anterior chamber depth and anterior chamber volume in the SMILE and FS‐LASIK group (all p < 0.05). A significant difference was observed in posterior corneal higher‐order aberrations before and after the FS‐LASIK (p = 0.006). A negative correlation was found between alterations of PCC R and changes of posterior corneal spherical aberrations in the SMILE (r = −0.289) and FS‐LASIK group (r = −0.383). In conclusion, posterior corneal and anterior chamber biometrics are changed after SMILE and FS‐LASIK. Innovatively, we find that changes in posterior corneal morphology are correlated with posterior corneal aberration alterations.

Corneal Higher-Order Aberrations Measurements: Precision of SD-OCT/Placido Topography and Comparison with a Scheimpflug/Placido Topography in Eyes After Small-Incision Lenticule Extraction.

The aim of this study was to evaluate the measurements of corneal higher-order aberrations (HOAs) obtained by a new anterior segment optical coherence tomography (OCT) technique combined with a Placido topographer (the MS-39 device) in eyes with prior small-incision lenticule extraction (SMILE) and compare them to the measurements obtained by a Scheimpflug camera combined with a Placido topographer (the Sirius device). A total of 56 eyes (56 patients) were included in this prospective study. Corneal aberrations were analyzed for the anterior, posterior, and total cornea surfaces. Within-subject standard deviation (Sw), test-retest repeatability (TRT), and intraclass correlation coefficient (ICC) were used to assess the intraobserver repeatability and interobserver reproducibility. The differences were evaluated by paired t-test. Bland-Altman plots and 95% limits of agreement (95% LoA) were used to evaluate the agreement. High repeatability was observed for anterior and total corneal parameters, with Sw value < 0.07, TRT ≤ 0.16, and ICCs > 0.893, but not trefoil. For the posterior corneal parameters, ICCs varied from 0.088 to 0.966. Regarding interobserver reproducibility, all Sw values were ≤ 0.04 and TRT ≤ 0.11. ICCs ranged from 0.846 to 0.989, from 0.432 to 0.972, and from 0.798 to 0.985 for the anterior, total, and posterior corneal aberrations parameters, respectively. The mean difference in all aberrations was ≤ 0.05μm. All parameters showed a narrow 95% LoA. The MS-39 device achieved high precision in both anterior and total corneal measurements; the precision of posterior corneal higher-order RMS, astigmatism II, coma, and trefoil was lower. The two technologies used by the MS-39 and Sirius devices can be used interchangeably for measuring corneal HOAs after SMILE.

Repeatability and reproducibility of corneal higher-order aberrations measurements after small incision lenticule extraction using the Scheimpflug-Placido topographer

BackgroundTo evaluate the precision of corneal higher-order aberrations measurements after small incision lenticule extraction (SMILE) using the Sirius Scheimpflug-Placido topographer (CSO, Italy).MethodsSeventy-five eyes from 75 postoperative subjects were included in this prospective study. Three consecutive corneal aberrometric measurements were obtained with the Scheimpflug-Placido topographer by two experienced operators to assess intra- and inter-observer reproducibility. The within-subject standard deviation (Sw), test-retest repeatability (TRT) and the intraclass correlation coefficient (ICC) were calculated.ResultsFor intraobserver repeatability of anterior and total corneal aberrations, all ICCs were more than 0.922, except for trefoil (0.722 to 0.768). The ICCs of total root mean square (RMS), coma Z (3, ± 1), and spherical aberration Z (4, 0) were over 0.810 while higher-order RMS, trefoil Z (3, ± 3), and astigmatism II Z (4, ± 2) were below 0.634 for posterior corneal surface aberrations. All Sw values for all types of aberrations were equal to or below 0.07 μm. Regarding interobserver reproducibility, all TRT values were no more than 0.12 μm, 0.05 μm, and 0.11 μm for anterior, posterior, and total corneal aberrations, respectively. The ICC values ranged from 0.875 to 0.989, from 0.686 to 0.976 and over 0.834 for anterior, posterior, and total corneal aberrations, respectively.ConclusionsThe repeatability of measurements of anterior and total corneal aberrations with the Sirius system in corneas after SMILE surgery was high, except for trefoil. There was some variability in posterior corneal aberrometric measurements. High reproducibility of corneal aberrometric measurements was observed between measurements of both examiners, except for trefoil, with poor to moderate reproducibility.

Change patterns in the corneal sub-basal nerve and corneal aberrations in patients with dry eye disease: An artificial intelligence analysis

We aimed to investigate the change patterns in corneal sub-basal nerve morphology and corneal intrinsic aberrations in dry eye disease (DED). Our study included 229 eyes of 155 patients with DED and 40 eyes of 20 healthy control. We used the Oculus keratograph and the ocular surface disease index questionnaire to assess their signs and symptoms. In vivo confocal microscopy was used to observe the corneal sub-basal nerves, corneal endothelial cells, and Langerhans cells (LCs). An artificial intelligence (AI) technique run by the deep learning model generated the sub-basal nerve fibre parameters. Furthermore, we used the Pentacam HR system to measure the corneal intrinsic aberrations and corneal surface regularity indices. DED patients more frequently had increased anterior and total corneal aberrations than controls (P < 0.05). In addition, DED had decreased average density and maximum length of corneal nerve. (Both P < 0.01) The LC number was significantly correlated with maximum length (CC = −0.19, P = 0.01) of the sub-basal nerve fibre. Furthermore, the corneal nerve average density was negatively correlated with IHD, and anterior, posterior, and total corneal aberrations (All P < 0.05) especially the higher-order aberrations. Significant correlations were seen between corneal nerve morphology changes, analysed by AI and corneal intrinsic aberrations, particularly higher-order aberrations.

An investigation into the effects of ocular nebulization combined with meibomian gland massage on ocular surface status and corneal higher-order aberrations for the treatment of meibomian gland dysfunction.

To evaluate ocular surface status and corneal higher-order aberrations after a new ocular nebulization therapy combined with meibomian gland massage for the treatment of meibomian gland dysfunction (MGD). This prospective randomized study involved 38 patients diagnosed with MGD. Subjects were classified into two groups: the nebulization and meibomian gland massage group (or NB group, 14 patients, 28 eyes) and the eye drop group (or ED group, 24 patients, 48 eyes). Azithromycin solution and esculin and digitalis glycoside eye drops were tested in the therapy. Best-corrected visual acuity (BCVA) testing; noncontact tonometry; fundoscopy; the Ocular Surface Disease Index (OSDI) questionnaire; tear film assessment encompassing tear meniscus height (TMH) and non-invasive keratograph breakup time (NIKBUT); corneal fluorescein staining; the Schirmer I test (SIT); and anterior, posterior and total corneal aberrations were evaluated at 1 and 3 months after treatment. At 3 months, the NB group showed significantly better improvement than the ED group in terms of TMH (0.23 ± 0.04 versus 0.19 ± 0.05, p = 0.002) and first breakup time (f-BUT; 7.42 ± 2.49 versus 5.53 ± 2.12, p = 0.001). The average breakup time (Av-BUT) of the NB group was significantly longer than that of the ED group at 1 month (9.52 ± 2.70 versus 8.02 ± 2.33, p = 0.013) and 3 months (5.53 ± 2.12 versus 8.35 ± 2.38, p = 0.018). Both groups achieved improvement in corneal fluorescein staining (CFS) and SIT results at 1 and 3 months (p < 0.05). At the 3-month follow-up, anterior corneal trefoil aberrations decreased significantly in the NB group (p = 0.008), and improvements in anterior corneal coma aberrations and posterior corneal higher-order aberrations (HOAs) were observed in the ED group (p < 0.05) over the 4 mm pupil zone. Over a 6 mm zone at 3 months, anterior, posterior and total trefoil aberrations as well as total HOAs were significantly decreased in the NB group (p < 0.05), while posterior HOAs and trefoil aberrations were found to be decreased in the ED group (p < 0.05). For individual Zernike terms, anterior and total corneal Z(3, -3) showed decreases over the 4 and 6 mm zones, while no improvement was detected in the NB group at 3 months. In terms of comfort and visual quality, nebulization therapy combined with meibomian gland massage to deliver azithromycin solution and esculin and digitalis glycoside eye drops appears to be more effective in treating clinical symptoms and signs of MGD than simply applying esculin and digitalis glycoside eye drops.

Recovery of Contrast Sensitivity After Descemet Membrane Endothelial Keratoplasty.

To study the change in contrast sensitivities in eyes with Fuchs endothelial dystrophy and bullous keratopathy after Descemet membrane endothelial keratoplasty (DMEK). In this prospective study, 50 pseudophakic eyes of 50 patients who received DMEK surgery at the Charité-Universitätsmedizin Berlin were included. Visual acuity; contrast sensitivity using OPTEC 6500 at spatial frequencies of 1.5, 3, 6, 12, and 18 cycles/degree in photopic and mesopic light with and without glare; central corneal thickness (CCT); and anterior and posterior corneal aberrations were measured preoperatively and at 3 and 12 months postoperatively. Best-corrected visual acuity (preoperative 0.67 ± 0.46 and after 12 months 0.19 ± 0.16 LogMAR, P < 0.001) and photopic and mesopic contrast sensitivities with and without glare improved significantly, whereas CCT decreased significantly (preoperative 677 ± 114 μm, after 12 months 527 ± 29 μm, P < 0.001). Preoperative CCT correlates significantly with preoperative photopic contrast sensitivity (correlation coefficient -0.462, P = 0.002), and postoperative total anterior aberrations correlates with postoperative photopic contrast sensitivity (correlation coefficient -0.361, P = 0.006). Photopic and mesopic contrast sensitivities, especially with glare, are impaired in patients with Fuchs endothelial dystrophy and bullous keratopathy. The extent of the corneal thickening seems to mainly influence the contrast sensitivity preoperatively. DMEK surgery improves the contrast sensitivity significantly. However, higher postoperative anterior corneal aberrations limit the postoperative contrast sensitivities.

Comparative assessment of functional outcomes of different endothelial keratoplasty techniques

Comparative analysis of the higher-order aberrations (HOA) of the cornea after endothelial keratoplasty (EK) using DSAEK and DMEK techniques; evaluation of the correlation between higher-order corneal aberrations and functional outcomes of the treatment. The study included 47 patients (59 eyes). The main group consisted of 35 patients (35 eyes) with bullous keratopathy and Fuchs' endothelial dystrophy; among them, 19 patients underwent endothelial keratoplasty using the DSAEK technique and 16 - DMEK technique. The control group included 12 patients (24 eyes) of corresponding age without corneal pathology. Standard and special examination tests were performed before, as well as 6 and 12 months after the operation, including computed tomography and aberrometry of the cornea using the Pentacam HR system. Same tests were performed in the control group. The values of the main HOA of the anterior corneal surface: RMS coma (Z3±1, Z5±1), RMS spherical aberration (SA; Z40, Z60) and RMS HOA (Z3-6) 6 months after different EK techniques were statistically significantly higher than in the control group. A statistically significantly lower induction of aberrations of the posterior corneal surface after DMEK technique was revealed. Analysis of the final aberration pattern 6 months after surgery did not reveal any statistically significant differences in the values of the main (RMS coma, RMS SA, RMS HOA) total corneal aberrations after DSAEK and DMEK. A negative correlation was revealed between the best corrected visual acuity (BCVA) and HOA; however, it was statistically significant only for individual aberration values: RMS HOA (Z3-6) of the posterior corneal aberrations after DMEK (r= -0.634, p=0.049), and RMS coma (Z3±1, Z5±1) of the cornea after DSAEK (r= -0.57, p=0.042). Comparative analysis of total corneal HOA did not reveal a statistically significant difference in the main parameters: RMS coma, RMS SA, RMS HOA in patients after DSAEK and DMEK surgeries. Correlation analysis did not reveal any statistically significant effects of most aberrations on the functional outcomes of the treatment.

Eyes of Aniso-Axial Length Individuals Share Generally Similar Corneal Biometrics with Normal Eyes in Cataract Population.

Aims To determine the characteristics of corneal biometrics in eyes from aniso-axial length cataract patients compared with eyes from non-aniso-axial length individuals. Methods This is a retrospective case series. Cataract patients with preoperative binocular measurements were recruited. A binocular axial difference of ≥1 mm was considered to indicate aniso-axial length. The anterior segmental biometrics were measured using Pentacam HR (Oculus, Wetzlar, Germany) and IOLMaster 500 (Carl Zeiss Meditec, Jena, Germany). Comparisons of biometrics were made among 4 eye conditions: the longer eyes from aniso-axial length patients, the shorter eyes from aniso-axial length patients, the longer eyes from non-aniso-axial length patients, and the shorter eyes from non-aniso-axial length patients. The aniso-axial length eyes were also stratified into 8 subgroups with axial length (AL) increments of 1 mm, and the biometrics of the subgroups were compared. Results There was smaller anterior corneal astigmatism in the shorter aniso-axial length group than those in the longer aniso-axial length group (1.01 ± 0.70 D vs 1.12 ± 0.76 D, P=0.031). The longer aniso-axial length eyes had greater anterior corneal steep curvature (44.13 ± 1.69 D vs 43.87 ± 1.69 D, P=0.009) and anterior corneal astigmatism (1.12 ± 0.76 D vs 1.02 ± 0.69 D, P=0.023) compared with longer non-aniso-axial length subjects. Other corneal biometrics were similar between the aniso-axial length eyes and the non-aniso-axial length eyes. In the longer aniso-axial length group, the posterior corneal aberrations of eyes in the ≥5 mm subgroups were greater than those in the <5 mm subgroups (0.879 ± 0.183 μm vs 0.768 ± 0.178 μm for total aberrations, P < 0.001; 0.228 ± 0.086 μm vs 0.196 ± 0.043 μm for high-order aberrations, P=0.036; 0.847 ± 0.173 μm vs 0.741 ± 0.179 μm for low-order aberrations, P=0.001). Conclusion Eyes of aniso-axial length individuals share generally similar corneal biometrics with normal eyes in cataract population. Anterior corneal astigmatism of the longer eyes from the aniso-axial length cataract patients was higher than that of the longer eyes from the non-aniso-axial length individuals. Total posterior corneal aberrations of the longer aniso-axial length eyes increased when the binocular axial difference was over 5 mm.

Accuracy of the posterior corneal elevation values of Pentacam HR from different reference surfaces in early ectasia diagnosis.

Detecting the accuracy of various posterior elevation (PE) indices of Pentacam HR, and correlating them with some possibly related factors or parameters, in a cohort with early keratoconus (KC). A cross sectional study that was conducted at Eye World Hospital, Egypt. One hundred and two corneas were enrolled, including two groups; group 1 (50 corneas) having forme fruste or early KC, and group 2 (52 corneas) for healthy controls. Corneas were scanned using Pentacam HR (Oculus, Wetzlar, Germany). The investigated PE parameters were: PE from best fit sphere (BFS), PE from best fit toric ellipsoid (BFTE), PE from exclusion map of Belin Ambrosio's display (BAD), and PE from difference map of BAD. The four PE values were correlated to age, thinnest corneal thickness "TCT," posterior aberrations, and posterior Q value. All the investigated indices were significantly different in group 1 compared to group 2 (p < 0.001). Accuracy of PE parameters revealed the highest AUROC for PE from BFTE (AUROC = 0.989, and best cutoff > 4 um with sensitivity 96.00% and specificity 96.15%). PE from difference map was the least accurate. Correlation coefficients showed a significant correlation between all the studied PE parameters and some of the posterior aberrations (root mean square of higher order aberrations, vertical coma, and spherical aberrations), besides a significant correlation with posterior Q value. PE indices are sensitive detectors of early ectasia. PE from BFTE had the highest deduced AUROC. Alterations in PE values can significantly alter many posterior corneal aberrations and the posterior Q.

Ultrathin Descemet stripping automated endothelial keratoplasty versus Descemet membrane endothelial keratoplasty: a fellow-eye comparison

BackgroundTo compare the visual outcome and patients’ satisfaction after ultrathin Descemet stripping automated endothelial keratoplasty (UT-DSAEK) and Descemet membrane endothelial keratoplasty (DMEK) performed on fellow eyes of the same patients.MethodsIn this retrospective study, the records of 18 pseudophakic patients affected by Fuchs endothelial dystrophy who underwent DMEK in one eye and UT-DSAEK in the fellow eye were reviewed. Best corrected visual acuity (BCVA), corneal pachymetry, keratometry, corneal aberrations, photopic and mesopic contrast sensitivity, and endothelial cell counts measured 12 months after surgery in either eye were analyzed and compared. The results of a satisfaction questionnaire were also reviewed.ResultsTwelve months after surgery, BCVA was not significantly different in UT-DSAEK and DMEK eyes (0.10 ± 0.04 and 0.07 ± 0.07 logMAR, respectively); at both 4- and 6 mm optical zones total and posterior corneal higher order aberrations (HOAs), posterior astigmatism and total coma were significantly lower after DMEK; BCVA in both groups was significantly correlated mainly with anterior corneal aberrations; contrast sensitivity was higher after DMEK especially in mesopic conditions and at medium spatial frequencies; the endothelial cell density was similar, although slightly higher in the UT-DSAEK group (p = 0.10). The satisfaction questionnaire showed that although patients were highly satisfied from both procedures, more than half of them preferred DMEK and reported a more comfortable and quicker postoperative recovery.ConclusionsDMEK and UT-DSAEK showed no evidence of difference in terms of postoperative BCVA, although DMEK had a better performance in terms of contrast sensitivity, posterior corneal aberrations and overall patient satisfaction.

Correlation analysis between corneal biomechanical properties and high-order aberration in myopia

Objective To investigate the correlations between corneal biomechanical properties and corneal high-order aberrations (HOAs) in myopic eyes. Methods In this retrospective study, 263 right eyes with myopia or myopic astigmatism were enrolled from January to October 2015 in Tianjin Eye Hospital.The values of first applanation time (A1T), first applanation length (A1L), first applanation velocity (A1V), second applanation time (A2T), second applanation length (A2L), second applanation velocity (A2V), highest concavity time (HCT), highest concavity deformation amplitude (HCDA), highest concavity peak distance (HCPD), highest concavity radius (HCR) and non-contact intraocular pressure (IOPnct) were measured using the corneal visualization Scheimpflug technology (Corvis ST). The central corneal thickness (CCT) and wavefront aberrations of the anterior, posterior surface, and the total cornea were measured with Pentacam.Pearson correlation and stepwise multivariate linear regression analysis were applied to analyze the correlations between biomechanical properties and corneal HOAs.This study follows the Helsinki declaration.The experiment was approved by the Ethic Committee of Tianjin Eye Hospital.Informed consent was signed from each patient. Results There was a correlation between biomechanical properties and corneal HOAs.Negative correlations were found between A1L and the spherical aberration, HOAs RMS of anterior surface, total RMS and HOAs RMS of the posterior surface and HOAs RMS of the total cornea (P<0.05). HCRs were negatively correlated with total RMS of the total cornea and the anterior surface (P<0.05). The A2V was correlated with various aberrations.Multiple stepwise linear regression model analysis showed that, the correlation between the aberrations of anterior surface and biomechanical parameters, and the correlations between the total corneal aberration and biomechanical parameters were weak, the correlations between the aberrations of posterior surface and biomechanical parameters were strong. Conclusions There is a correlation between the biomechanical properties and corneal HOAs.The changes of the corneal biomechanical properties are mainly associated with the posterior corneal aberrations, which may contribute to the early diagnosis of subclinical keratoconus or dilated corneal disease. Key words: Corneal biomechanical properties; Aberration; Visual quality

Posterior cornea and thickness changes after scleral lens wear in keratoconus patients.

To evaluate the changes in the corneal thickness, anterior chamber depth and posterior corneal curvature and aberrations after scleral lens wear in keratoconus patients with and without intrastromal corneal ring segments (ICRS). Twenty-six keratoconus subjects (36.95 ± 8.95 years) were evaluated after 8 h of scleral lens wear. The subjects were divided into two groups: those with ICRS (ICRS group) and without ICRS (KC group). The study variables evaluated before and immediately after scleral lens wear included corneal thickness evaluated in different quadrants, posterior corneal curvature at 2, 4, 6 and 8 mm of corneal diameter, posterior corneal aberrations for 4, 6 and 8 mm of pupil size and anterior chamber depth. There was a statistically significant corneal thinning (p < 0.05) in the inferior region of the KC group and in the superior region of the ICRS group. No change (p > 0.05) in the anterior chamber depth was found. The KC group showed a steepening (p < 0.05) in the temporal quadrant and a flattening that mainly affected to the superior-nasal quadrant. The ICRS group showed a steepening (p < 0.05) that mainly affected to the superior-nasal quadrant. Regarding posterior corneal aberrations, only changes (p < 0.05) in Z4 for 8 mm and Z8 for 4 mm were found in the KC group. Short-term scleral lens wear showed a thinning of the cornea and changes in the posterior corneal curvature affects different regions in keratoconus patients with and without ICRS.

Persistence of the Cone on the Posterior Corneal Surface Affecting Corneal Aberration Changes After Intracorneal Ring Segment Implantation in Patients With Keratoconus.

To analyze the changes in anterior and posterior corneal surfaces and aberrations in patients who underwent intracorneal ring segment (ICRS) implantation for the treatment of keratoconus. Eighty-nine eyes of 59 patients with keratoconus who underwent ICRS implantation were analyzed. All eyes were evaluated using a tomography system combining a Placido disc and Scheimpflug photography before and at least 6 months after surgery. Total, anterior, and posterior corneal aberrations, anterior and posterior sagittal and tangential anterior and posterior curve analysis, keratometry (K), minimum corneal thickness, and anterior chamber depth were analyzed before and after surgery. Flattening with a decrease in the cone shape on the anterior corneal surface and steepening in the paracentral area with persistence of cone appearance on the posterior corneal surface were noted in all cases after ICRS implantation. The total corneal higher-order aberrations (HOAs) significantly decreased from 1.09 ± 0.43 to 0.71 ± 0.32 μm, and anterior corneal HOAs significantly decreased from 0.98 ± 0.46 to 0.81 ± 0.37 μm, whereas the posterior corneal HOAs increased from 0.53 ± 0.29 to 0.66 ± 0.25 μm after ICRS implantation (P < 0.05). There was a significant decrease in anterior maximum keratometry, but there was a significant increase in posterior maximum keratometry after ICRS implantation (P < 0.05). The cone shape persists on the posterior corneal surface despite its correction on the anterior corneal surface, leading to a decrease in anterior corneal aberrations and an increase in posterior corneal aberrations after ICRS implantation in eyes with keratoconus.

Toric Intraocular Lenses Versus Peripheral Corneal Relaxing Incisions for Astigmatism Between 0.75 and 2.5 Diopters During Cataract Surgery

To compare the outcomes after toric intraocular lens (tIOL) or peripheral corneal relaxing incisions (PCRI) for keratometric astigmatism (KA) between 0.75 and 2.5 diopters (D) during cataract surgery. Prospective randomized clinical trial. Eighty eyes (80 participants) received either tIOL or PCRI and were assessed preoperatively, 1, 3, 6, and 12months postoperatively. Uncorrected (UCDVA) and best-corrected distance logMAR visual acuity (BCDVA) at 12months. Uncorrected near visual acuity (UCNVA), manifest refraction, KA and mean keratometry (KM), corneal aberrometry, tIOL rotation, and quality-of-life questionnaire. Comparing tIOLs vs PCRIs, there was no significant difference in the UCDVA, BCDVA, and UCNVA. At 12months, 61% vs 53% had UDCVA of 20/25 or better, 100% vs 76% gained ≥1 lines, and 59% vs 43% were within ±0.13 D spherical equivalent. In the PCRI group, anterior KA decreased at 1month and remained stable thereafter; there was a nonsignificant trend toward a flatter posterior KA and steeper posterior KM and the total corneal Z2-2 was low at 1 and 12months. Over 12months, there were changes in posterior corneal tilt, coma, and hexafoil in the PCRI group. The mean rotation of the tIOLs at 12months was 1.8 ± 1.4 degrees. tIOL patients were happier and were glad to use the nonprescription sunglasses. There was no difference in visual acuity, although more tIOL patients gained ≥1 line and were within ±0.13 D. After PCRIs, the anterior KA decreased in the early postoperative period and remainedstable thereafter and posterior corneal aberrations changed constantly over 12months.

Anterior Corneal, Posterior Corneal, and Lenticular Contributions to Ocular Aberrations.

To determine the corneal surfaces and lens contributions to ocular aberrations. There were 61 healthy participants with ages ranging from 20 to 55 years and refractions -8.25 diopters (D) to +3.25 D. Anterior and posterior corneal topographies were obtained with an Oculus Pentacam, and ocular aberrations were obtained with an iTrace aberrometer. Raytracing through models of corneas provided total corneal and surface component aberrations for 5-mm-diameter pupils. Lenticular contributions were given as differences between ocular and corneal aberrations. Theoretical raytracing investigated influence of object distance on aberrations. Apart from defocus, the highest aberration coefficients were horizontal astigmatism, horizontal coma, and spherical aberration. Most correlations between lenticular and ocular parameters were positive and significant, with compensation of total corneal aberrations by lenticular aberrations for 5/12 coefficients. Anterior corneal aberrations were approximately three times higher than posterior corneal aberrations and usually had opposite signs. Corneal topographic centers were displaced from aberrometer pupil centers by 0.32 ± 0.19 mm nasally and 0.02 ± 0.16 mm inferiorly; disregarding corneal decentration relative to pupil center was significant for oblique astigmatism, horizontal coma, and horizontal trefoil. An object at infinity, rather than at the image in the anterior cornea, gave incorrect aberration estimates of the posterior cornea. Corneal and lenticular aberration magnitudes are similar, and aberrations of the anterior corneal surface are approximately three times those of the posterior surface. Corneal decentration relative to pupil center has significant effects on oblique astigmatism, horizontal coma, and horizontal trefoil. When estimating component aberrations, it is important to use correct object/image conjugates and heights at surfaces.

Changes in Corneal Power After Descemet Stripping Automated Endothelial Keratoplasty.

To examine the optical effects of Descemet stripping automated endothelial keratoplasty (DSAEK) by evaluating changes in anterior and posterior corneal curvatures and aberrations. Eighty-three eyes treated using DSAEK combined with cataract surgery (the DSAEK group) and 41 control eyes of healthy patients (the control group) were included. Patients were examined before and 1 year after surgery with autokeratometry and Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany). The preoperative posterior corneal curvature was estimated from the anterior corneal curvature. The mean intended postoperative refraction in the DSAEK group was -0.75 ± 0.62 diopters (D), which was statistically different from the achieved refraction of +0.50 ± 0.93 D at the 1-year follow-up (P < .001). The average biometry prediction error was a hyperopic shift of +1.27 ± 0.80 D. Anterior corneal power was significantly higher before than after DSAEK with a difference of -0.63 ± 0.68 D (P = .03) correlating significantly with the hyperopic change (r(2) = 0.23, P < .01). The posterior corneal power after DSAEK showed a significant steepening of -0.69 ± 0.38 D (P < .01) from the estimated preoperative power and a difference of -0.64 ± 0.38 D (P < .01) from the posterior corneal power in the control group. The change correlated significantly with the hyperopic change (r(2) = 0.10, P < .01). The combined changes in anterior and posterior keratometry increased the correlation coefficient to r(2) = 0.34 (P < .01). Significant differences were observed for total higher-order aberrations root mean square and coma root mean square after DSAEK compared to controls. No significant changes were observed in spherical aberration. The hyperopic shift in the DSAEK group can be explained by changes in anterior and posterior corneal surfaces. Spherical aberration was not changed by DSAEK, suggesting that aspherical intraocular lenses may be implanted on the same indications as in normal cataract surgery.

Repeatability of aberrometric measurements in normal and keratoconus eyes using a new Scheimpflug–Placido topographer

To evaluate the repeatability of the anterior and posterior corneal wavefront aberrations using the Sirius Scheimpflug-Placido topographer in normal eyes and keratoconus eyes. Bozok University Faculty of Medicine, Yozgat, Turkey. Evaluation of diagnostic test. In eyes of healthy subjects and eyes of keratoconus patients, 3 repeated measurements were obtained using the Scheimpflug-Placido topographer. Repeatability of the corneal aberrometric data using a 7th-order Zernike expansion (6.0 mm pupil) and central corneal power (3.0 mm zone) in the anterior and posterior corneal surfaces were analyzed. The within-subject standard deviation (Sw) and the intraclass correlation coefficient (ICC) were calculated. For all modal pairs, the Sw was 0.08 μm or less for anterior and posterior corneal aberrations in both groups. The ICC of the anterior corneal surface ranged from 0.607 (pentafoil) to 0.988 (primary coma) in keratoconus eyes (n = 41) and from 0.568 (quadrifoil) to 0.856 (primary coma) in normal eyes (n = 30). The ICCs for posterior corneal surface aberrometry were 0.656 to 0.873 and 0.592 to 0.824, respectively. For anterior and posterior corneal curvatures, the Sw was 0.12 or lower and the ICC values were more than 0.93 in all cases except the posterior corneal surface reading at the 3.0 mm corneal area in keratoconus eyes (ICC 0.875). The intraexaminer repeatability of most anterior corneal aberrations with the Scheimpflug-Placido system was moderate to high in normal eyes and keratoconus eyes. The system showed moderate repeatability for the posterior corneal surface. No author has a financial or proprietary interest in any material or method mentioned.

Intraocular pressure in keratoconus

This study aimed to investigate intraocular pressure (IOP) measurements taken using the dynamic contour tonometer (DCT) and the non-contact tonometer (NCT) in subjects with keratoconus. Intraocular pressure was measured in 20 keratoconus subjects and 20 age-matched control subjects using the DCT and NCT instruments. Central and off-centre measures were taken with the DCT in order to highlight any systematic errors associated with corneal biomechanical factors. Measures of anterior and posterior corneal topography and thickness were also taken in each subject. No significant difference was found between the central and off-centre DCT IOP readings for the keratoconus subjects and age-matched controls (p > 0.05). The average DCT IOP was 14.2 ± 1.4 mmHg in the keratoconus subjects and 14.2 ± 1.6 mmHg in the controls. However, the average NCT readings differed significantly (p < 0.001) between the keratoconus subjects (9.2 ± 1.5 mmHg) and the controls (12.9 ± 2.4 mmHg). Intraocular pressure measurements taken with the DCT showed no significant (p > 0.05) correlation with the severity of keratoconus as determined through measures of corneal topography and thickness. Equivalent IOP measurements taken with the NCT correlated significantly with certain measures of corneal curvature and thickness in the keratoconus population. The difference between DCT and NCT IOP was strongly correlated with measures of corneal topography and thickness, with differences increasing in more advanced keratoconus. The measurements obtained with the DCT do not appear to be dependent upon corneal factors, unlike those taken with the NCT. The presence or severity of keratoconus was not correlated with DCT IOP values.

Pentacam posterior and anterior corneal aberrations in normal and keratoconic eyes

Purpose: The aim was to evaluate the anterior and posterior corneal aberrations provided by the Pentacam system in normal and early to moderate keratoconic eyes.Methods: Fifteen normal eyes (normal group, mean age 32.60 ± 7.45-years) and 15 eyes with the diagnosis of keratoconus (keratoconus group, mean age 29.07 ± 8.66-years) were included in this study. All eyes received a comprehensive ophthalmologic examination including corneal topographic analysis with the Pentacam system. Keratometric, best‐fit sphere and corneal aberrometric data were recorded and analysed. Root mean square values (RMS) were calculated for primary coma and coma‐like aberrations.Results: Statistically significant differences were found in all anterior aberrometric parameters (all p < 0.02), except for horizontal primary and secondary coma Zernike terms (p = 0.61 and 0.72). Regarding posterior corneal surface, statistically significant differences among groups were found in primary spherical aberration, primary vertical coma, coma RMS and coma‐like RMS (all p < 0.01). In the normal group significantly higher levels of primary vertical coma, spherical aberration, coma and coma‐like RMS were found for the posterior corneal surface (all p < 0.04). In the keratoconus group, only significant differences among anterior and posterior corneal surfaces were found in coma RMS, coma‐like RMS and vertical coma (all p < 0.01). These higher levels of aberrations for the posterior corneal surface do not agree with the theoretical optical properties of this surface.Conclusions: With the Pentacam system, higher levels of vertical coma, primary coma and coma‐like aberrations are present in keratoconic eyes compared to normal eyes. The values provided by this device for posterior corneal aberrations are erroneous.