Vertical Trefoil Research Articles

Analysis of third and fourth corneal high-order aberrations before and after small incision lenticule extraction (SMILE) in myopic and myopic astigmatic eyes using ray tracing aberrometry

BackgroundAim is to analyze alterations in third and fourth corneal higher-order aberrations using a ray tracing aberrometer (iTrace) induced by SMILE (small incision lenticule extraction) refractive surgery on Algerian patients; and also to investigate how corneal aberrations vary with spherical equivalent (SE), corneal central thickness (CCT), and age. Design Prospective, non-randomized case series that were carried out at the Chiali Smile Center, Algiers, Algeria.ParticipantsA total of 219 eyes from 110 myopic patients, with and without astigmatism, successfully concluded the ultimate follow-up. Participants exhibited an average age of 32.48 years, with preoperative mean corneal high-order aberrations (CHOA) measuring 0.005 ± 0.036 μm.MethodsA tracking trend analysis of high-order aberrations (HOAs) was conducted on the three groups of patients, assessing total corneal high-order aberrations after SMILE over periods of two, six, and twelve months.ResultsA substantial increase in total corneal high-order aberrations following SMILE, with a P value < 0.05. Conversely, there was a noteworthy and significant decrease in vertical trefoil for all groups (P value = 0.000). Interestingly, the corneal higher-order aberrations were more pronounced after two months compared to the six and twelve-month intervals. Spherical aberration demonstrated a significant increase with the extent of preoperative myopia and preoperative spherical equivalent both before and after SMILE surgery (P < 0.05), particularly in cases of high myopia. Moreover, there were significant reductions in preoperative and postoperative vertical coma (P = 0.047, P = 0.004, respectively) corresponding to the degree of preoperative myopia, with a more substantial decrease in vertical coma observed in cases of low myopia.ConclusionIn the post-SMILE period, a notable increase in vertical coma and spherical aberrations was observed, accompanied by a significant decrease in vertical trefoil across all eyes. These aberration changes were identified to be closely associated with the spherical equivalent.

Effect of Small Angle Misalignments on Ocular Wavefront Zernike Coefficients

Purpose: To assess the possible impact of minor changes in fixation on wavefront measurements as a potential constraint in detecting subtle temporal variations in ocular wavefront error. Methods: Twelve healthy subjects with an average age of 36.3 ± 8.8 were instructed to put their heads in the aberrometer’s chin-rest and look at a fixation target that was embedded in the device. The fixation targets were readily observable to the participants without accommodation, thanks to the aberrometer’s Badal system. When each eye was staring at the target, its wavefront aberration was recorded three times and then averaged for further analysis. The averaged Zernike coefficients were rescaled to the smallest value of the maximum round pupil found among all eyes (4.41 mm), and this procedure was repeated for each target. Results: Alteration of the fixation targets caused changes to the Zernike coefficients of defocus (C(2,0)), vertical trefoil (C(3,–3)), vertical coma (C(3,–1)), horizontal coma (C(3,1)), oblique trefoil (C(3,3)), primary spherical aberration (C(4,0)), and secondary spherical aberration (C(6,0)), but the changes were not statistically significant. Nevertheless, an alteration in the target’s size and shape exhibited a significant correlation across all of the aforementioned coefficients in both eyes (p &lt; 0.05). The total RMS of aberrations and the RMS of the spherical-like aberrations were both lowest while choosing the larger Maltese cross, and the bigger E-letter minimized the RMS of HOA and comatic aberrations. Conclusion: The aberrometric changes occur as a consequence of altering the fixational gaze and are within the range of the changes found after performing a near-vision task, so they might potentially act as a confounding factor when attempting to identify such small variations in the ocular wavefront. Using a smaller E-letter (5 arcmin) as an internal fixation target resulted in the least standard deviation of measurements, fixational stability, and higher accuracy in ocular wavefront measurements.

The impact of corneal higher-order aberrations on dynamic visual acuity post cataract surgery.

To explore the influence of corneal higher-order aberrations (HOAs) on dynamic visual acuity (DVA) post cataract surgery. A total of 27 patients with 45 eyes following cataract surgery were included in this study. The postoperative monocular object-moving DVA at the velocity of 20, 40, and 80 degrees per second (dps) were examined at 1 month. The total corneal HOAs were measured with Scheimpflug-based corneal topography. The correlation between postoperative DVA and HOAs was analyzed. Significant difference was shown among DVA at different velocities (P < 0.001). The 20 dps DVA was significantly better than 40 (P < 0.001) and 80 (P < 0.001) dps DVA. No significant difference was observed between 40 and 80 dps DVA (P = 0.420). The vertical coma and the root mean square (RMS) of coma (RMScoma) were statistically correlated with 80 dps DVA (P < 0.05). The vertical trefoil, RMStrefoil and total RMSHOA were statistically correlated with 40 and 80 dps DVA (P < 0.05). The spherical aberration was not significantly associated with postoperative DVA (P > 0.05 for all velocites). The multivariate linear regression model revealed that age was a significant influential factor for 20 dps DVA (P = 0.002), and RMStrefoil (4 mm) and age were significantly associated with 40 and 80 dps DVA (P ≤ 0.01). The research demonstrated that larger corneal HOAs, especially coma and trefoil aberrations were significantly associated with worse high-speed DVA, but not spherical aberration post cataract surgery.

The effect of transepithelial corneal collagen cross-linking treatment on optical quality of the cornea in keratoconus: 12-month clinical results.

To evaluate the effect of transepithelial corneal collagen crosslinking (CXL) treatment on the optical performance of the cornea at 12-month follow-up after CXL in patients with progressive keratoconus. One hundred and ten eyes of 67 patients were included. The following corneal optical aberrations over the 4-mm-diameter pupil were recorded via Sirius dual-scanning corneal tomography: total, anterior and posterior amount of corneal higher order aberrations [HOAs], vertical coma, horizontal coma, vertical trefoil, oblique trefoil, and spherical aberration, and Strehl ratio of point spread function (PSF). There were significant improvements in mean root mean square error values for corneal total HOA, total coma, anterior HOA, anterior coma, and vertical coma following CXL (P > 0.05, for all). No significant changes were found in the posterior aberometric parameters.PSF value did not change after CXL (P > 0.05). The corneal topographic measurements not revealed a change in the mean simulated keratometry-1, simulated keratometry-2, and maximum keratometry compared with the baseline measurements (P > 0.05, for all). At 12months, there was a significant improvement in the uncorrected (UCVA) and best corrected (BCVA) visual acuity (P < 0.001, both). Most corneal aberrations correlated significantly with postoperative BCVA, but changes in HOAs were not statistically associated with improvements in visual acuity. Transepithelial CXL was effective in stabilizing the keratometric indices and improving the most corneal aberrations in keratoconic eyes 1year after the procedure. While the healing effect on aberrations after CXL was in total and anterior parameters, no significant changes were observed in the posterior surface. In addition, it was observed that transepithelial CXL treatment did not cause a significant change in PSF distribution data.

Evaluation of Corneal High Order Aberrations in Post Laser-Assisted in Situ Keratomileusis versus Photorefractive Keratectomy in Myope

Background Aberrations of the eye are the difference between two surfaces: the ideal and the actual wave front. Higher order aberrations are a relatively small component, comprising about 10% of the eye’s total aberrations. High order aberrations increase with age and minor symmetry exists between the right and the left eyes. Aim and objectives To Compare corneal high order aberrations in post laser-assisted in situ keratomileusis with corneal high order aberrations in post Photorefractive keratectomy in myope. Subjects and methods this study was designed as a prospective randomized intervention study that conducted on 40 myopic eyes. The eyes divided into two randomized groups. Group A: 20 myopic eyes corrected with laser-assisted in situ keratomileusis and Group B: 20 myopic eyes corrected with Photorefractive keratectomy. Cases were collected for LASIK and PRK at operative theater in Beni-Suef University Hospital and clear vision laser center in Cairo, from May 2019 till January 2022. Result There was clinically significant difference between pre- and post-operative visual acuity, vertical trefoil and vertical coma of LASIK group and there was clinically significant between pre- and post-operative visual acuity, vertical trefoil and vertical coma of PRK group. But there was no significant difference between LASIK and PRK in visual acuity, spherical aberration, higher order 5 mm and 6 mm, vertical coma and Vertical trefoil. Conclusion There is non-significant increase in higher order aberration and spherical aberration post LASIK and post PRK with lesser amount in PRK.

Early, Forme Fruste keratoconus and normal thin cornea, evaluation of sensitive parameters by combined Placido Scheimpflug topography.

To determine the sensitive indices distinguishing forme-fruste keratoconus (FFKC) and early keratoconus (early KC) from thin normal corneas, and their cutoff values using Sirius topography. 156 eyes with normal thin corneas < 500 um (group 1), 99 eyes with early KC (group 2) and 41 eyes with FFKC (group 3), were assessed retrospectively for: corneal keratometric indices, pachymetry indices, corneal aberrations, elevation indices; thinnest corneal point elevation, Q value, root mean square (RMS) withRMS/ area (RMS/A); and KC summary indices of front and back surfaces; surface asymmetry index (SIf, SIb), elevation at KC vertex (KVf, KVb), Baiocchi-Calossi-Versaci index (BCVf, BCVb) and summation of its vector (BCV). Cutoff values were calculated. Keratometry indices were significantly different between early KC and thin normal cases (apex front curvature had the highest area-under-the-ROC-curve (AUROC) (0.926) in early KC, while only apex curvature and coordinates were significant in FFKC cases. Pachymetry indices did not show any significance in differentiating either early KC or FFKC from normal thin corneas. KC summary indices were highly significant among the 3 groups. The highest AUROC was observed with KVb in early KC (0.987) and with KVf in FFKC (0.831). Vertical coma and vertical trefoil showed the highest significance of all aberration parameters differentiating the 3 groups. Thinnest point elevation, RMS and RMS/A showed the highest AUROC in differentiating early KC and FFKC cases from thin normal corneas. Comparing early KC and FFKC to thin normal corneas, Sirius provided high precision in prediction.

One-year clinical efficacy evaluation of selective corneal wavefront aberration-guided FS-LASIK correction in patients with high myopia.

To evaluate the effectiveness, safety, predictability, precision and changes of higher-order aberrations (HOAs) on corneal front surface of selective corneal wavefront aberration-guided femtosecond laser-assisted in situ keratomileusis (CW-FS-LASIK) in patients with high myopia 1-year postoperatively. Totally 74 eyes of 37 patients with high myopia or myopic astigmatism in both the eyes who underwent the CW-FS-LASIK procedure in Xi'an Gaoxin Hospital from January 2021 to June 2021 were included. The changes of uncorrected distance visual acuity (UDVA), best corrected visual acuity (BCVA), spherical equivalent refraction (SER), astigmatism, HOAs and Strehl ratio (SR) on the anterior surface of the cornea after 1y of the surgery were analyzed. At postoperative 1y, the UDVA (logMAR) of 74 eyes (100%) reached 0 or better, including 0 in 8 eyes (10.81%), -0.1 in 45 eyes (60.81%), and -0.2 in 21 eyes (28.38%). The effectiveness index was 1.29±0.134. There was no decrease in postoperative BCVA compared with preoperative BCVA in all patients. Postoperative BCVA was the same in 44 eyes (59.46%) as preoperative BCVA, increased by 1 line in 23 eyes (31.08%) and increased by 2 lines in 7 eyes (9.46%) compared with preoperative BCVA. The safety index was 1.11±0.159. The estimated corrected SER before surgery was (-7.76±1.21) D, and the actual corrected SER was (-7.83±1.25) D (Y=0.9811X+0.2156, R2=0.9084). There was a high correlation between the estimated corrected SER and the actual corrected SER. The postoperative SER in 74 eyes (100%) was within ±0.75 D. The postoperative astigmatism of all was within -0.75 D to 0. Root mean square (RMS) HOAs of spherical aberration and SR within 5 mm of the corneal front surface were all increased compared with those before operation (P<0.01). The total coma, horizontal coma and vertical coma were all decreased compared with those before operation (P<0.01). There was no statistically significant difference in horizontal trefoil and vertical trefoil compared with preoperative ones (P>0.05). Selective CW-FS-LASIK for correction of high myopia is effective, safe, predictive, and accurate. For patients with preoperative RMS HOAs over 0.25 defocus equivalent, postoperative coma aberration can be significantly reduced, and SR value can be increased, thus corneal imaging quality can be improved.

Effect of Upper Lid Blepharoplasty Surgery on Corneal Topography and Corneal High-Order Aberrations.

The objective of this study was to prospectively investigate the effect of upper eyelid blepharoplasty surgery for dermatochalasis on corneal topographic data and high-order aberrations (HOAs). Fifty eyelids of 50 patients with dermatochalasis who underwent upper lid blepharoplasty surgery were prospectively studied. A Pentacam (Scheimpflug camera, Oculus) device was used to measure corneal topographic values, astigmatism degree, and HOAs before and at 2 months after upper eyelid blepharoplasty. The mean age of the patients included in the study was 55.96 ± 12.4 years, 40 (80%) were female and 10 (20%) were male. We found no statistically significant difference in the pre-and postoperative values of corneal topographic parameters (p > 0.05 for all). In addition, we observed no significant postoperative change in the root mean square values of low, high, and total aberration values. In HOAs, we detected no significant change in spherical aberration, horizontal and vertical coma, and vertical trefoil; we only found a statistically significant increase in horizontal trefoil values after surgery (p < 0.05). In our study, we found that upper eyelid blepharoplasty did not cause significant changes in corneal topography, astigmatism, and ocular HOAs. However, studies are reporting different results in the literature. For this reason, it is important for patients considering upper eyelid surgery to be warned about visual changes that may occur after surgery.

Evaluation of Ocular Higher-Order Aberrations in First-Degree Relatives of Patients With Keratoconus.

The aim of this study was to evaluate the corneal higher-order aberrations (HOAs) in first-degree relatives of patients with keratoconus (KCN) and compare with the normal population. In this prospective comparative study, 210 eyes from 105 family members of 28 patients with KCN and 210 normal eyes of 105 controls were enrolled. In each eye, corneal topography, tomography, and aberrometry were performed and compared between the 2 groups. This study included 61 female (58.1%) and 44 male participants (41.9%) and 105 age-matched and sex-matched controls with normal topographic cornea. In 14 of 105 first-degree relatives (13.33%) of patients with KCN, KCN was diagnosed with a male preponderance (71.5% male, 28.5% female). Tomographic indices and irregularity indices in 3 and 5 mm zone in Orbscan were significantly higher in the relative group. In addition, other irregularity indices of TMS-4 topography including surface regularity index, surface asymmetry index, difference sector index, SDP, and irregular astigmatism index were significantly higher in family members of patients with KCN. The most prevalent topographic pattern in the control group was the symmetric bowtie (57.1%) and in the relative group was the asymmetric bowtie (39.5%). In addition, significantly thinnest corneal pachymetry was detected in the relative group. Root mean square of all HOAs including vertical trefoil, vertical coma, horizontal coma, horizontal trefoil, quadrifoil, and fourth-order spherical aberrations were significantly greater in the relative group than controls. Owing to the high prevalence of undiagnosed KCN susceptibility in family members with KCN, keratorefractive surgery should be considered cautiously in these individuals. In addition, comprehensive preoperative examination should be considered to detect subtle topographic and HOAs in these individuals.

Long-Term Observation of Higher-Order Aberrations and Microdistortions in Bowman's Layer After Small Incision Lenticule Extraction for the Correcting Myopia With Spherical Equivalent Higher Than -9.0 Diopters.

PurposeTo evaluate the outcomes in corneal higher-order aberrations (HOAs) and microdistortions in the Bowman’s layer after femtosecond laser small incision lenticule extraction (SMILE) for correcting extremely high myopia.MethodsThis prospective study included patients with myopia with spherical equivalent ≥ -9.0 Diopters (D). SMILE was performed in forty eyes of 40 patients. Pentacam was used to evaluate HOAs before and at 1 day, 3 months, 6 months, and 2 years after surgery. Fourier-domain optical coherence tomography was used to evaluate microdistortions at 2 years postoperatively. Thirty-two eyes of 32 patients receiving femtosecond laser-assisted in situ keratomileusis (FS-LASIK) were enrolled as the control group. HOAs were measured before, at 1 day and at least 1 year postoperatively.ResultsAfter SMILE, the long-term safety and effectiveness index was 1.25 and 0.85, respectively. Microdistortions were observed in 73.5% of the eyes at 2 years, with an average number of 1.20 ± 1.22 microdistortions and an average width of 287.37 ± 259.00 μm. We detected more microdistortions in the horizontal meridian than in the vertical meridian (p = 0.035). The average number and width of microdistortions were both higher in the central region (≤4 mm) than in the peripheral region (4–8 mm) (both p < 0.001). With the exception of horizontal trefoil in the SMILE group and vertical trefoil in the FS-LASIK group, significant changes over time were observed in all other HOAs (all p < 0.05). Meanwhile, we detected significant increases in the total corneal HOA, spherical aberration (SA), and coma at all time-points after both surgeries (all p < 0.01). Compared with FS-LASIK, SMILE induced less SA (p < 0.001) and more horizontal coma (p = 0.036). In the SMILE group, the HOA, SA, and trefoil were more in the small optical zone (≤6.0 mm) than in the large optical zone (>6.0 mm) (all p < 0.05). The increase in SA and most trefoil correlated with the mean number of central microdistortions number (all p < 0.05).ConclusionFor myopia over −9.0D, the microdistortions in the Bowman’s layer were still detectable in most eyes long-term after SMILE. Both SMILE and FS-LASIK induced more HOAs, mainly HOA, SA, and coma. The small optical zone and microdistortions may affect postoperative aberrations.

Changes of high order aberrations after photorefractive keratectomy (PRK) and FemtoLASIK

Purpose: a comparative study of corneal and total wavefront aberration changes after traditional PRK and FemtoLASIK.Material and methods. Corneal and total wavefront aberrations were studied on OPD-Scan III aberrometer (Nidek) in 63 patients (126 eyes) with moderate and high myopia before and after FemtoLASIK (Ziemer + Nidek-Quest, Japan) (44 patients, 88 eyes) and PRK (Nidek-Quest, Japan) (19 patients, 38 eyes). Spherical aberration (SA) was considered as the sum Z4 + Z8 + Z12.Results. The corneal asphericity coefficient Q changed to positive values after both types of intervention. Corneal RMS HOA increased in both Femto and PRK groups. Corneal Tilt 1 increased after FemtoLASIK and moved to negative values after PRK, corneal tilt 2 moved to negative values after Femto and to positive values after PRK. The vertical trefoil showed no significant change in the Femto group and dropped in the PRK group. The vertical and horizontal coma (coma 7, coma 8) changed synchronously. Corneal SA increased after Femtolasic, and became negative after PRK. The total aberrations showed a lesser change and the changes were not synchronized with the corneal ones: in particular, the RMS HOA fell from 0.28 ± 0.05 to 0.19 ± 0.05 in the Femto group, while the corneal RMS increased significantly. In the PRK group, the corneal RMS HOA showed some increase, but it was much less than corneal RMS: from 0.25 ± 0.07 to 0.62 ± 0.02 μm. The total SA increased from 0.11±0.03 to 0.27±0.02 in the Femto group and showed an insignificant drop from 0.09±0.03 to 0.03 ± 0.01, while remaining positive in the PRK group.Conclusions. The changes of the wavefront after FemtoLASIK and PRK are both significant and different. The revealed differences in the changes of corneal aberrations correspond to different profiles of the anterior surface of the cornea formed after FemtoLASIC and PRK. The internal optics of the eye partially compensates the corneal aberrations induced by excimer laser surgery.

Corneal Asphericity Variations in Korean Myopic Children

Purpose: Corneal asphericity (Q-value) represents the difference in curvature from center to periphery of the cornea. This study evaluated horizontal and vertical asymmetry in corneal asphericity in myopic children and its relationship with various ocular parameters.Methods: This retrospective study included 47 eyes in 24 myopic Korean children. Corneal parameters, such as corneal asphericity and thickness, apical radius of curvature, and high order aberrations including total root mean square (RMS), spherical aberration, coma, and trefoil were analyzed by Pentacam. Axial lengths (ALs) and anterior chamber depths (ACDs) were measured by IOL master. From these values, characteristics of corneal asphericity differences between nasal-temporal and superior-inferior quadrants in myopic children and their relationship with other ocular parameters were evaluated.Results: The mean Q-value (8 mm) was -0.34 ± 0.10, representing a prolate corneal shape. The mean superior-inferior Q-value differences (8 mm) was 0.23 ± 0.17, which was greater than the mean nasal-temporal Q-value differences (8 mm) measured as 0.15 ± 0.13. The mean Q-value (8 mm) was not significantly related to AL or ACD, and Q-values in each quadrant (8 mm) also showed no significant relationship with corneal thickness in each corresponding quadrant. The nasal-temporal Q-value differences (8 mm) had a positive relationship with total RMS (p = 0.001) and a negative relationship with oblique trefoil (p = 0.045) and spherical aberration (p = 0.007). The superior-inferior Q-value differences (8 mm) showed a negative relationship with vertical trefoil (p = 0.003).Conclusions: The results of the study showed a variation of nasal-temporal and superior-inferior Q-value differences, and the relationship between corneal shape and other ocular dimensions in myopic Korean children. Further study with large data set is merited to ascertain the epidemiologic data of Asian ethnicity.

Effect of Accommodation on Peripheral Higher Order Aberrations

Knowledge of the effect of accommodation on image quality of peripheral retina is crucial for better understanding of the visual system, but only a few studies have been carried out in this area. This study was designed to evaluate the effect of accommodation on higher order aberrations from third to sixth Zernike polynomials in central and peripheral retina up to 23° off-axis. We used a Hartmann–Shack aberrometer to measure Zernike coefficients with both accommodated and non-accommodated eyes of 15 healthy subjects. Each Zernike coefficient, total higher order aberrations, spherical aberrations and astigmatism were compared between accommodated and non-accommodated status. Additionally, aberrations in the central retina were compared with the peripheral retina. Accommodation induced significant changes in the Zernike coefficients of vertical pentafoil C5−5 and secondary vertical tetrafoil C6−4 in central retina, secondary vertical astigmatism C4−2 on 23° of temporal retina, secondary vertical tetrafoil C6−4 and tertiary vertical astigmatism C6−2 on 10° of nasal retina, secondary vertical trefoil C5−3 and secondary vertical tetrafoil C6−4 on 23° of nasal retina, and horizontal tetrafoil C44, and secondary horizontal tetrafoil C64 on 23° of inferior retina (p &lt; 0.05). Total higher order aberration was lower in each retinal area examined with accommodation, but it was statistically significant only on 23° temporal retina and 11.5° and 23° of superior retina (p &lt; 0.05). Spherical aberration decreased with accommodation on 23° temporal retina (p = 0.036). Astigmatism was similar in non-accommodated and accommodated eyes. Overall, accommodation affected higher order aberration (HOA) asymmetrically in different peripheral retinal areas.

Effect of Central Corneal Thickness on Corneal Higher Order Aberrations After Cataract Surgery.

To investigate the changes of corneal higher order aberrations (HOAs) before and after phacoemulsification in patients with different central corneal thickness (CCT). In this retrospective non-randomized, non- comparative cases series, 51 eyes of 51 patients who underwent phacoemulsification were enrolled. The corneal total HOAs and Zernike coefficients (3rd and 4th order) over the 3- and 4-mm zones were measured by the iTrace aberrometer (Tracey Technologies). Participants were divided into three groups (528 µm or less, 529 to 550 µm, and greater than 550 µm) depending on the CCT tested by the LenStar LS900 (Haag Streit AG). The corneal aberrations between groups were compared with analysis of variance, the variation of corneal aberrations before and after phacoemulsification was analyzed by the paired-samples t test, and generalized linear models were used to compare postoperative aberrations between groups. Significant differences were found in oblique trefoil at 3 mm and vertical trefoil, oblique trefoil, and HOAs at 4 mm in the 528 µm or less group; vertical trefoil, oblique trefoil, oblique quadrafoil, and oblique secondary astigmatism at 3 mm and oblique trefoil and oblique secondary astigmatism at 4 mm in the 529 to 550 µm group; and vertical quadrafoil at 3 mm in the greater than 550 µm group. After corrected deviation of preoperative aberrations, there were significant differences in postoperative vertical coma and oblique secondary astigmatism at 4 mm when compared to the 528 µm or less and greater than 550 µm groups. The lower the CCT, the greater the change in corneal aberrations in patients with cataract after phacoemulsification. Surgeons should be aware of the potential for worse visual quality related to surgically induced aberrations in patients with thin corneas. [J Refract Surg. 2021;37(12):842-847.].

Factors Influencing Higher-order Aberrations in Young Myopes

Purpose : To investigate the effects of age, refractive errors, corneal refractive power, pupil diameter, and pupil center shift on high-order aberrations (HOAs) in young myopic eyes. Methods : The myopic eyes of aged 20 to 39 years who had no ophthalmologic diseases and refractive surgery were recruited. I-Profilerplus (Zeiss, Berlin, Germany) was used to measure HOAs and refractive errors, corneal refractive power, pupil diameter, and pupil shift, and factors affecting HOA were analyzed. Results : In young myopes, as the age increased, the total HOA was increased in the positive (+) direction (p<0.001), and the horizontal coma, vertical coma, and spherical aberration (SA) were increased in the negative (-) direction (all, p<0.001). As the equivalent spherical refractive errors increased in the negative (-) direction, the total HOA was increased in the negative (-) direction (p<0.001), and the SA was increased in the positive (+) direction (p=0.004). As the mean corneal refractive power increased, the total HOA and SA were increased in the negative (-) direction (p<0.001, p=0.025), and the horizontal coma and vertical coma aberration were increased in the positive (+) direction (p=0.001, p<0.001). As the pupil diameter increased, vertical trefoil and SA were increased in the positive (+) direction (all, p<0.001). As the pupil center shift increased toward the lateral, the horizontal coma aberration increased in the positive (+) direction (p=0.003), and as the pupil center shift increased toward the superior, the vertical coma aberration increased positive (+) direction (p<0.001). Conclusion : The ocular HOAs of the young myopes changes according to age, refractive error, corneal refractive power, pupil size, and pupil center shift and the results in this study would be cornerstones in designing lenses for spectacle and contact lens.

Evaluation of topographic, tomographic, topometric, densitometric, and aberrometric features of cornea with pentacam HR system in subclinical keratoconus.

To investigate topographic, tomographic, topometric, densitometric, and aberrometric parameters in subclinical keratoconus with the Pentacam HR imaging system. Data of 3128 patients were evaluated, finding in 108 patients clinical keratoconus in one eye and subclinical keratoconus in the other. Corneal topographic, tomographic, topometric, densitometric, and aberrometric values obtained using the Pentacam HR imaging system were compared between clinical keratoconus, subclinical keratoconus, and normal eyes. Comparing eyes with subclinical keratoconus and the control group, while flat K, horizontal coma, horizontal trefoil, and vertical trefoil values were similar (p > 0.05 for each), all other parameters were significantly different (p < 0.05 for each). Densitometry values of eyes with subclinical keratoconus were significantly higher in all layers of the 0-2mm annular area and in the anterior and central layers of the 2-6mm annular area compared to the control group (p < 0.05 for each). According to the receiver operating characteristic curve analysis, the densitometry region with the largest area under the curve was the anterior layer of the 0-2mm annular area. The sensitivity in this region was 79.4% and the specificity 73.2% in distinguishing eyes with subclinical keratoconus from normal eyes when 19.3 GSU was considered the threshold. Corneal densitometry values in the 0-2 and 2-6mm annular areas, especially in the anterior layers, are parameters that can be used to predict and distinguish subclinical keratoconus from normal eyes.

The Effect of Corneal Collagen Cross-Linking on Higher Order Aberrations in Keratoconus

Purpose: To assess the changes in ocular high order aberrations after collagen cross linking for keratoconus.&#x0D; Patients and Methods: This study included 30 eyes with confirmed KCN. Baseline evaluation focused on: UDVA and BSCVA using logMAR notation, MRSE, corneal topography using Orbscan IIZ and wave-front aberrometry using Zywave II. CXL was performed per ‘Dresden protocol’ through a 30-minutes exposure to 370 nm UVA with an irradiance of 3 mW/cm 2. Patients had comprehensive ophthalmic evaluation after 6 months with special attention to: UDVA, BSCVA, MRSE, corneal topography and wave-front aberrometry changes. &#x0D; Results: The mean age was 25.5±5.84 (20:31) years. After 6 months, there was a significant decrease in corneal thickness from 493.2± 24.17µ to 486.7±24.26µ (P&lt;0.05) and a significant decrease in K max from 47.4±1.17D to 46.1±1.17D (P&lt;0.05). BSCVA improved from preoperative value (0.00:0.5 logMAR (median 0.3)) to 6 months’ value (0.1:1.00 logMAR (median 0.2) (P &lt;0.05). Preoperative MRSE was -7.25: -0.5D (median -2.85D) and at 6 months was -6.25: -0.5D (median - 2.125D) (P&lt;0.05). A significant correlation was found at 6 months between changes in both BSCVA and: K max (P&lt;0.001), corneal thickness (P&lt;0.05), vertical coma (P&lt;0.001) and trefoil (P&lt;0.001). &#x0D; Conclusions: Improvement in HOA was detected after CXL for KCN. The changes in total, vertical coma and vertical trefoil aberrations were significantly correlated with postoperative improvement in BSCVA. Thus, improvement in HOA profile after CXL is one of the explanations of improvement in visual function after CXL in KCN.

Optical aberrations of the eyes with various degrees of myopia

The study included 134 eyes of 67 patients with mild, moderate and high myopia aged 7-28 (mean age 19.3±1.5 years). The following biometric parameters were examined: anterior chamber depth (ACD), lens thickness (LT), axial length (AL), as well as corneal and total aberrations. The parameters were studied on the Galilei G6 system (Ziemer Ophthalmic Systems AG, Switzerland) and the OPD-Scan III aberrometer (Nidek, Japan). Spherical aberration (SA) was estimated as the sum of Z4+Z8+Z12. As the refraction increased, the root mean square higher-order aberrations (RMS HOA) also increased significantly: from 0.24±0.02 μm in mild myopia to 0.45±0.03 μm in high myopia, and in eyes with AL of ≥27.0 mm - to 0.57±0.02 μm (p=0.01). An increase in vertical tilt, vertical coma and vertical trefoil were also observed. Total SA was positive and increased in eyes with moderate myopia compared to those with low myopia (from 0.02±0.01 μm to 0.06±0.02 μm, p=0.02), which coincided with changes in the internal optics of the eye: an increase in ACD and a decrease in LT. At the same time, no differences in corneal aberrations were observed among patients with low and moderate myopia. A significant decrease of SA occurred in high myopia (from 0.06 μm in low myopia to 0.015±0.02 μm in high myopia). The average value of SA was 0.005±0.01 μm in eyes with AL of ≥27.0 mm and appeared to be negative in 40% of cases. The average value of corneal SA was negative (-0.002±0.01μm) in eyes with AL of ≥27.0 mm. This group had predominantly patients with congenital myopia. An increase of total positive SA in patients with moderate myopia compared to those with low myopia is associated with changes in the internal optics of the eye (ACD, LT). Significant increase of higher-order aberrations and decrease of SA with the transition to negative values was observed in patients with high axial myopia.

The short term effect of trehalose and different doses of sodium hyaluronate on anterior corneal aberrations in dry eye patients

Aim To evaluate the short-term effect of 0.15% sodium hyaluronate (SH), 0.20% SH, and Trehalose + 0.15% SH on anterior corneal aberrations in dry eye patients. Methods 76 eyes of 76 dry eye patients were divided into three groups. Non-preserved 1.5 mg/mL SH was administered in group 1, non-preserved 2.0 mg/mL SH was administered in group 2, and non-preserved trehalose 30 mg/mL and 1.5 mg/mL SH was administered in group 3. Aberrometry measurements were performed before and 10 min after application of the artificial tear drop. Using the Pentacam Scheimpflug imaging system, total root mean square (RMS), lower-order aberration (LOA), higher-order aberrations (HOAs), spherical aberration (SA), trefoil, and coma aberrations were investigated. Results In each group; the RMS of total, LOA, HOAs, and spherical aberration were significantly decreased after the artificial drop instillation, compared with those of them at baseline; and in groups 1 and 2, vertical trefoil term was also significantly increased, compared with those of them at baseline. According to intergroup analyzes, there was no significant outcome. Conclusions It was observed that three artificial tears reduced the anterior corneal aberrations, in a 10-min period. The short-term effect of three artificial tears on the anterior corneal aberration was similar.

Optical Quality Assessment in Patients with Unilateral Congenital Ptosis: A Matched Case-Control Study

Background. To evaluate the differences in the corneal higher-order aberrations (HOAs) and optical quality of the ptosis eyes compared with the normal fellow eyes in the unilateral congenital ptosis patients. Methods. A matched case-control study was performed in 17 pairs of eyes in 17 unilateral congenital ptosis patients. The ptosis eye was enrolled in the ptosis group while the normal fellow eye was enrolled in the normal group. The HOAs obtained from Pentacam HR and the optical quality parameters obtained from Optical Quality Analysis System (OQAS) were compared between the two groups. Results. There were significant differences in a vertical coma and vertical trefoil on the anterior corneal surface between the ptosis group and the normal group p &lt; 0.05 . The OQAS parameters in the ptosis group were significantly different from those in the normal group p &lt; 0.05 . The vertical fissure height (VFH) showed a significant correlation with the total HOAs, 3rd HOAs, and vertical coma on the anterior corneal surface p &lt; 0.05 . Conclusions. Compared with the normal fellow eyes, the ptosis eyes showed significantly degraded optical quality. The eyelid position was important for the changes of corneal HOAs in the ptosis eyes. The reasons for the discrepancy of the OQAS parameters between the ptosis eyes and normal fellow eyes were multiple.