Posterior Corneal Higher-order Aberrations Research Articles

Evaluation of Anterior and Posterior Corneal Higher Order Aberrations for the Detection of Keratoconus and Suspect Keratoconus

To investigate the application of anterior and posterior corneal higher-order aberrations (HOAs) in detecting keratoconus (KC) and suspect keratoconus (SKC). A retrospective, case-control study evaluating non-ectatic (normal) eyes, SKC eyes, and KC eyes. The Sirius Scheimpfug (CSO, Italy) analyses was used to measure HOAs of the anterior and posterior corneal surfaces. Sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) were calculated. Two-hundred and twenty eyes were included in the analysis (normal n = 108, SKC n = 42, KC n = 70). Receiver operating characteristic (ROC) curve analysis revealed a high predictive ability for anterior corneal HOAs parameters: the root mean square (RMS) total corneal HOAs, RMS trefoil, and RMS coma to detect keratoconus (AUC > 0.9 for all). RMS Coma (3, ±1) derived from the anterior corneal surface was the parameter with the highest ability to discriminate between suspect keratoconus and normal eyes (AUC = 0.922; cut-off > 0.2). All posterior corneal HOAs parameters were unsatisfactory in discriminating between SKC and normal eyes (AUC < 0.8 for all). However, their ability to detect KC was excellent with AUC of >0.9 for all except RMS spherical aberrations (AUC = 0.846). Anterior and posterior corneal higher-order aberrations can differentiate between keratoconus and normal eyes, with a high level of certainty. In suspect keratoconus disease, however, only anterior corneal HOAs, and in particular coma-like aberrations, are of value. Corneal aberrometry may be of value in screening for keratoconus in populations with a high prevalence of the disease.

Anterior and posterior corneal higher-order aberrations in early diagnosis and grading of keratoconus

ABSTRACTClinical relevanceEvaluation of corneal higher-order aberrations can be used clinically to diagnose early cases of keratoconus as well as to classify the severity of keratoconus.BackgroundTo investigate the anterior and posterior corneal higher-order aberrations (HOAs) up to the sixth order and their ability to identify early keratoconus (KCN) as well as differentiate different severities of KCN using cross-validation analysis.MethodsThis prospective cross-sectional comparative study was performed at a tertiary eye hospital in Tehran, Iran, in 2019. The study sample consisted of 95 eyes of 95 patients with KCN and 53 eyes of 53 normal individuals. The eyes with KCN were classified into three groups based on the Amsler–Krumeich classification system: group 1 (mild KCN), group 2 (moderate KCN), and group 3 (severe KCN). Corneal wavefront analysis was performed using Pentacam HR.ResultsBased on the magnitude of AUC, posterior vertical secondary coma (Z5−1) had an excellent discriminant ability (AUC: 0.91) and anterior vertical coma (Z3−1) and anterior vertical secondary coma (Z5−1) had a good discriminant ability (0.8 < AUC < 0.89) for differentiating eyes with mild KCN from normal eyes. The anterior and posterior primary spherical aberrations (Z4°) had an excellent ability (AUC > 0.9), and anterior secondary spherical aberration (Z6°) had a good ability (AUC: 0.83) for differentiating moderate from mild KCN. In the differentiation of severe from moderate KCN, anterior and posterior primary aspherical aberrations (Z4°) had a good AUC value (AUC > 0.8).ConclusionComa-like aberrations had a good discriminant ability between normal eyes and eyes with mild KCN. Spherical aberrations showed a good ability for differentiating between different stages of KCN. The cut-off values reported in this study can be used for early detection of KCN as well as classification of KCN severity.

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.

Accelerated versus Standard Corneal Cross-linking for Progressive Keratoconus in Syria.

PurposeTo compare the outcomes of accelerated versus standard corneal cross-linking for the treatment of progressive keratoconus.Methods In this retrospective comparative study, 63 eyes of 40 patients with progressive keratoconus were divided into two groups; 27 eyes in group one were treated with an accelerated protocol (10 mW/cm, 9 min) and 36 eyes in group two were treated with the standard method (3 mW/cm, 30 min). Visual acuity, refraction, corneal topography, corneal tomography, and anterior and posterior corneal higher-order aberrations (HOAs) were assessed preoperatively and 18–30 months postoperatively.ResultsThe LogMAR uncorrected and corrected distance visual acuity values were improved in both groups postoperatively. However, the improvement was significantly higher in group one (P 0.05, all). The flattening in the anterior keratometry readings, flat K, steep K, and average K were significantly higher in group two (P 0.001, all). The maximum anterior keratometry (AKf) values significantly decreased in both groups, whereas the maximum posterior keratometry (AKb) values increased. The reduction in the minimum corneal thickness (ThKmin) was significantly greater (36.49um) in group two, compared to 10.85um in group one. There was a significant increase in the posterior average keratometry, and a significant decrease in the posterior astigmatism, along 3 mm meridian in S-CXL (P = 0.03, P = 0.008, respectively), while the corresponding values showed no statistical significance in group one (P 0.05). The anterior corneal trefoil was significantly reduced in group one (P = 0.002), whereas anterior total HOAs and coma were significantly improved in group two (P 0.0014, all). The posterior corneal spherical aberration decreased significantly in group one (P = 0.02), while group two revealed significant reduction in the posterior trefoil values (P = 0.011). The change in the anterior maximum keratometry was significantly and positively correlated to the preoperative maximum keratometry in group two (P = 0.53, P = 0.003).ConclusionAn accelerated cross-linking protocol using 10 mW/cm for 9 min showed more visual improvement and less pachymetric reduction when compared to the standard protocol, however, anterior corneal flattening, posterior corneal steepening, and the change in the posterior astigmatism were significantly higher in the standard protocol; while corneal HOAs were improved in both protocols.

Soft contact lens-induced corneal deformation in the posterior corneal surface

ObjectiveThis case report aims to highlight the corneal deformation induced by soft contact lens (SCL) wear, which is accompanied by changes in not only the anterior but also the posterior surface of cornea. Case ReportCases are presented of two patients who wore non- planned replacement SCL for more than 15 years fabricated from materials with low oxygen permeability, sought a consultation with complaints of visual acuity loss in the both eyes. Anterior segment optical coherence tomography imaging demonstrated corneal deformation in the posterior as well as the anterior surface in both eyes of two patients, resulting in the diagnosis of corneal deformation induced by SCL wear. After the cessation of lens wear, there were improvements in visual acuity, anterior and posterior corneal higher-order aberrations, and changes in the anterior corneal shape, whereas the posterior corneal shape was improved in one case and remained mildly deformed in the other case. ConclusionWearing SCLs with low oxygen permeability for long time periods, could induce corneal deformation in patients, indicating the need for careful observation of changes in not only the anterior but also the posterior corneal surface.

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.

Factors Influencing Visual Acuity in Fuchs' Endothelial Corneal Dystrophy.

In eyes with mild Fuchs' endothelial corneal dystrophy without significant corneal edema, objective scattering index has the strongest influence on distance visual acuity, followed by the anterior corneal densitometry. Our findings suggest that distance visual acuity deteriorates in eyes with higher forward light scatter. To evaluate the factors affecting distance visual acuity in patients with Fuchs' endothelial corneal dystrophy. This retrospective study comprised 31 eyes of 31 patients with mild Fuchs' dystrophy without corneal edema and 25 eyes of 25 age-matched healthy subjects. Stepwise multiple regression analysis was used to assess the relationship between distance acuity with age, sex, forward light scatter, corneal backward scatter, anterior and posterior corneal higher-order aberrations, endothelial cell density, central corneal thickness, and corneal astigmatism. The forward light scatter, corneal backward scatter, and corneal higher-order aberrations were significantly larger in the Fuchs' dystrophy group than those in the control group (P ≤ .004). In a univariate analysis, with higher forward light scatter, anterior corneal backward scatter, corneal higher-order aberrations, and age, the distance acuity significantly deteriorated in eyes with Fuchs' dystrophy. In a multiple linear regression analysis, explanatory variables relevant to the distance acuity were the forward light scatter (P < .001, partial regression coefficient B = 0.035) and anterior corneal backward scatter (P = 0.2, B = 0.008) (adjusted R = 0.694). Eyes with higher light scatter, especially forward light scattering, showed deteriorated visual acuity. Results suggest that forward light scatter and corneal backward scatter play a more important role in visual performance than corneal higher-order aberrations in Fuchs' endothelial corneal dystrophy.

Optical Quality of the Cornea After Descemet Membrane Endothelial Keratoplasty

To evaluate corneal higher-order aberrations (HOAs) and backscattered light before and after Descemet membrane endothelial keratoplasty (DMEK) and their correlation with visual outcome. Retrospective study. In a total of 118 consecutive eyes of 118 patients who underwent uneventful DMEK for Fuchs endothelial dystrophy at a tertiary referral center, best spectacle-corrected visual acuity (BSCVA), corneal HOAs, and backscattered light were evaluated preoperatively and at 6 months postoperatively. Outcome data were compared to an age-matched control group with uncomplicated eyes (n = 27). Compared to the control group, Fuchs endothelial dystrophy eyes, before as well as 6 months after DMEK, showed higher values of anterior and posterior HOAs and backscattered light (P < .033). Postoperative anterior HOAs and backscattered light (0-2 mm) were associated with lower 6-month BSCVA (positively related with logMAR BSCVA) (P ≤ .020). Anterior corneal HOAs did not change from preoperative to 6 months after DMEK (P = .649), while total posterior HOAs (RMS third to sixth Zernike order) and haze decreased (P < .001). Anterior and posterior corneal HOAs, as well as backscattered light from the cornea, were elevated in eyes suffering from Fuchs endothelial dystrophy and remained higher throughout 6 months after DMEK. If present, anterior surface irregularities and anterior corneal haze may be the most important limiting factors in visual rehabilitation after DMEK.

Higher-order aberrations after corneal collagen crosslinking for keratoconus and corneal ectasia

To determine changes in higher-order aberrations (HOAs) after corneal collagen crosslinking (CXL). Cornea and refractive surgery practice. Prospective randomized controlled clinical trial. Corneal and ocular HOAs were measured and analyzed using the Pentacam device and Ladarwave aberrometer, respectively, at baseline and 12 months after CXL. Ninety-six eyes (64 keratoconus, 32 ectasia) of 73 patients had CXL. A fellow-eye control group comprised 42 eyes. The mean preoperative total anterior corneal HOAs, total coma, 3rd-order coma, and vertical coma were 4.68 μm ± 2.33 (SD), 4.40 ± 2.32 μm, 4.36 ± 2.30 μm, and 4.04 ± 2.27 μm, respectively. At 1 year, the mean values decreased significantly to 4.27 ± 2.25 μm, 4.01 ± 2.29 μm, 3.96 ± 2.27 μm, and 3.66 ± 2.22 μm, respectively (all P<.001). There were no significant changes in posterior corneal HOAs. The mean preoperative total ocular HOAs, total coma, 3rd-order coma, trefoil, and spherical aberration were 2.80 ± 1.0 μm, 2.60 ± 1.03 μm, 2.57 ± 1.03 μm, 0.98 ± 0.46 μm, and 0.90 ± 0.42 μm, respectively. At 1 year, the mean values decreased significantly to 2.59 ± 1.06 μm, 2.42 ± 1.07 μm, 2.39 ± 1.07 μm, 0.88 ± 0.49 μm, and 0.83 ± 0.38 μm, respectively (all P=.01). After CXL, HOAs were significantly improved compared with the control group. Changes in HOAs were not statistically associated with an improvement in visual acuity or most subjective visual symptoms, however. Corneal and ocular HOAs decreased after CXL, suggesting an improvement in corneal shape.

Characteristic Higher-Order Aberrations of the Anterior and Posterior Corneal Surfaces in 3 Corneal Transplantation Techniques

To investigate the corneal higher-order aberrations (HOAs) of the anterior and posterior corneal surfaces in eyes that underwent penetrating keratoplasty (PK), deep anterior lamellar keratoplasty (DALK), and Descemet stripping automated endothelial keratoplasty (DSAEK). Retrospective, case-control study. study population: Twenty-four eyes underwent PK, 28 eyes underwent DALK, and 19 eyes underwent DSAEK; 29 normal eyes served as controls. observation procedures: The anterior and posterior corneal heights and pachymetric data were obtained with a Scheimpflug-based corneal topographer. Corneal HOAs for 4-mm pupils were calculated from the height data and were expanded with normalized Zernike polynomials. The HOAs resulting from the anterior and posterior corneal surfaces were compared among the procedures. main outcome measures: Anterior and posterior corneal HOAs (root mean square). Control eyes had significantly lower total HOAs and Zernike vector terms of the anterior and posterior surfaces than the other groups, except for spherical aberration. The mean anterior corneal surface total HOAs in the PK, DALK, DSAEK, and control groups were 1.38 ± 0.67 μm, 1.19 ± 0.57 μm, 0.61 ± 0.33 μm, and 0.21 ± 0.07 μm, respectively. The anterior corneal HOAs in the DSAEK group were significantly less than those in the PK group (P < .001) and DALK group (P < .001). The mean posterior corneal surface total HOAs were, respectively, 0.20 ± 0.09 μm, 0.24 ± 0.11 μm, 0.27 ± 0.15 μm, and 0.07 ± 0.02 μm. There were no significant differences in the posterior corneal HOAs among the treatment groups. Because the refractive indices between the anterior and the posterior surfaces differed greatly, eyes that undergo DSAEK have lower anterior corneal HOAs compared with PK or DALK eyes. However, the anterior and posterior corneal HOAs in DSAEK eyes still were greater than those in control eyes.