Vertical Coma Research Articles

Optical and retinal changes influenced by different lighting conditions

Retinal morphology, specifically in its curvature, and ocular aberrations change when the eye adapts to different lighting conditions, including photopic, scotopic, mesopic, blue light, and red light. Sixty healthy young subjects with refractive error less than ±4.00D of sphere and 3.00D of cylinder, not suffering from accommodative problems, ocular or systemic pathology, and not having used electronic devices half an hour before or having taken substances that alter the retina during the 2 hours prior to the study were included. The subjects adapted to five lighting conditions, each for 5 minutes, in a controlled environment. Ocular aberrometry and Optical Coherence Tomography (OCT) were taken to capture images of the central and peripheral retina before (baseline measurement) and after adaptation to each lighting condition. The OCT images were exported and processed to analyze retinal curvature, obtaining parameters such as eccentricity, asphericity and shape factor. The results showed that the shape of the retina is hyperbolic prolate, becoming flatter in scotopic and blue light conditions, and more curved in mesopic conditions. Retinal curvature was closest to baseline under red light and photopic conditions. Aberrometric differences, particularly in the C(2,0) polynomial for defocus, showed higher values in mesopic, baseline, and scotopic conditions, and lower values in photopic, blue light, and red light. Significant differences were also observed in spherical aberrations C(4,0) and C(6,0), vertical coma C(3,-1), and trefoil C(3,-3). The spherical equivalent indicated more myopic values in mesopic, baseline, and scotopic conditions, and more hyperopic values in blue, photopic, and red light, suggesting a link between myopia and lower luminosity. The study concludes that illumination affects retinal curvature and ocular refraction, influencing myopia.

Corneal Allogenic Intrastromal Ring Segments (CAIRS) Versus Synthetic Segments: A Single Segment Comparative Analysis Using Propensity Score Matching.

To compare and assess the visual, refractive, and tomographic results of patients with corneal ectasia treated with either corneal allogenic intrastromal ring segments (CAIRS) or synthetic intrastromal corneal ring segments (ICRS) without concomitant corneal cross-linking. In this retrospective cohort study, 34 eyes with CAIRS were matched to 34 eyes with ICRS using the propensity score matching technique. Each group was matched on a oneto-one basis using multiple parameters such as central corneal thickness, vertical and horizontal coma, maximum anterior keratometry, steepest keratometry, and age. Visual, refractive, topographic, and aberrometric data were measured at baseline, 1 week, 1 month, 3 months, and 1 year postoperatively. Initial preoperative parameters were similar between the two groups. Both groups showed significant improvement at last follow-up time in corrected distance visual acuity (CDVA) (0.52 ± 0.23 to 0.16 ± 0.18 logarithm of the minimum angle of resolution [logMAR], P < .001; 0.44 ± 0.27 to 0.17 ± 0.21 logMAR, P < .001), topographic astigmatism (4.45 ± 2.75 to 3.14 ± 1.93 diopters [D], P = .001; 3.66 ± 2.22 to 2.36 ± 1.46 D, P = .007), maximum anterior keratometry (55.85 ± 7.53 to 50.69 ± 6.38 D, P < .001; 54.59 ± 6.95 to 50.71 ± 4.51 D, P = .003), and vertical coma (1.49 ± 1.02 to 0.38 ± 0.65 D, P < .001; 1.22 ± 0.75 to 0.52 ± 0.57 D, P < .001) for CAIRS and ICRS, respectively. The improvements observed in both groups at the last follow-up visit were comparable; however, the CAIRS group demonstrated a higher percentage of eyes gaining two or more Snellen lines of CDVA (60% vs 31.58%, P = .04), and a greater magnitude of reduction in vertical coma compared to the ICRS group, although this difference did not reach statistical significance. No major complications were observed with both groups, and one eye lost one CDVA line in the ICRS group. The mean thickness of the CAIRS segments at the last follow-up visit was 401.06 ± 100.12 µm, compared to 435.29 ± 26.19 µm for ICRS. Both CAIRS and ICRS demonstrated significant compression of stromal thickness above the segment (36.19% and 32.00%, respectively). When adequately matched for preoperative disease type and severity, eyes with CAIRS had a similar and notable clinical improvement compared to ICRS, with possibly better improvement in vertical coma and CDVA. [J Refract Surg. 2024;40(11):e863-e876.].

Changes in Corneal Higher Order Aberrations Following Cataract Surgery With Different Incision Sites: A Prospective, Randomized Study.

To compare the effect of superior and temporal clear corneal incisions, regardless of the steep axis, on postoperative changes in corneal higher order aberrations (HOAs) in patients with healthy corneas and mild preoperative corneal astigmatism. In this prospective cohort study, the right eyes of study participants were randomly assigned to one of two groups prior to cataract surgery: temporal incision (TI) and superior incision (SI). Preoperatively and 6 weeks after surgery, measurements were taken of corneal HOAs over a 6-mm optical zone. The study included 102 eyes (50 eyes in the TI group and 52 eyes in the SI group) that underwent routine phacoemulsification using a 2.4-mm clear corneal incision. Significant changes in vertical coma (P = .019), horizontal coma (P = .042), and vertical trefoil (P = .001) were observed in the SI group. In the subgroup analysis of the SI group, significant changes in vertical coma (P = .025) and vertical trefoil (P = .047) were observed in the eyes with preoperative with-the-rule corneal astigmatism, and significant changes in horizontal coma (P = .038) were observed in eyes with preoperative against-the-rule corneal astigmatism. The TI group showed no significant difference between the preoperative and postoperative periods. The SI induced vertical and horizontal coma in accordance with the preoperative axis of the steep meridian. These alterations in corneal HOAs may affect the quality of vision after surgery. TI may potentially provide an advantage over SI in terms of corneal HOAs. [J Refract Surg. 2024;40(11):e792-e796.].

Femtosecond Laser-Assisted Graft Preparation and Implantation of Corneal Allogeneic Intrastromal Ring Segments for Corneal Ectasia: 1-Year Results.

To evaluate the outcomes of patients treated with corneal allogeneic intrastromal ring segments cut with femtosecond laser (Femto-CAIRS) without concomitant corneal crosslinking. Patients with keratoconus treated with Femto-CAIRS at the American University of Beirut Medical Center were included (May 2022-January 2023). A proprietary software program was developed on the femtosecond laser to cut allogeneic segments. Visual, refractive, tomographic, aberrometric, and epithelial data by anterior segment optical coherence tomography were measured at baseline and 1, 3, 6, and 12 months postoperatively. 20 eyes of 15 patients were included and followed up for 12 months. The manifest refraction spherical equivalent and cylinder improved from -6.79 ± 4.9 diopter (D) and -4.25 ± 1.8 D to -1.88 ± 2.9 D (P < 0.001) and -2.64 ± 1.4 D (P = 0.01) 12 months postoperatively, respectively. 75% of eyes gained 3 or more corrected distance visual acuity lines, most of which (65%) gained 4 lines or more 12 months postoperatively. The maximum keratometry and vertical coma decreased by 5.2 D (P < 0.001) and 1 μm (P = 0.001), respectively, 3 months postoperatively and remained stable until 12 months. The largest anterior stromal elevation over the central 5-mm diameter decreased from 36.0 ± 18.2 μm preoperatively to 19.9 ± 9.25 μm at 1 week postoperatively (P < 0.001) and remained relatively stable. Epithelial thickness over the cone increased relative to baseline starting 1 month postoperatively and becoming stable after 6 months while the mean epithelial thickness central to the ring peaked at 1 month after which it decreased to reach a plateau at 6 months. The Femto-CAIRS procedure improves visual and tomographic parameters and allows repeatable and safe results with the possibility of customization for individualized management.

Correction of Presbyopia by Monocular Bi-Aspheric Ablation Profile.

The study aims to evaluate visual acuity and objective visual quality before and after the monocular bi-aspheric ablation profile for correction of presbyopia surgery. This prospective self-control study included 20 cases and 38 eyes of patients who underwent monocular bi-aspheric ablation profile correction of myopia with presbyopia at the Eye Hospital of Shandong University of Traditional Chinese Medicine from January 2023 to January 2024. These patients were selected for observation, and each patient's preoperative and postoperative uncorrected distance visual acuity (UDVA), uncorrected near visual acuity (UNVA), corrected distance visual acuity (CDVA), spherical aberration (SA) (within 6 mm), horizontal and vertical coma (within 6 mm), and corneal aspheric index (Q-value) (within 6 mm) were evaluated. Statistical data analysis was performed at different time points before and after the operation. There were statistically significant differences in UDVA between dominant and non-dominant eyes before and after surgery (Z = -3.784, p < 0.001; Z = -3.817, p < 0.001). Post-operatively, 90% of the non-dominant eyes achieved UNVA of J1 and above, and 95% of the bilateral eyes achieved UNVA of J1 and above. Significant differences were found in the SA of the dominant eyes, which showed a positive increase (Z= -3.784, p < 0.001); however, compared with the dominant eye, the SA of the non-dominant eye was negatively increased, but the difference was not statistically significant (p = 0.08). There was a significant difference in the vertical coma of the dominant eye before and after the operation, but there was no significant difference in non-dominant eyes. There was no significant difference in the change of binocular horizontal coma before and after the operation. There were significant changes in the Q value of both eyes before and after the operation (Z = -3.923, p < 0.001; Z = -3.51, p < 0.001). After the monocular bi-aspheric ablation profile, the cornea of the non-dominant eye showed a prolate shape, negative SA increased, and the UDVA and UNVA improved after the operation.

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.

Comparison of objective visual quality between SMILE and FS-LASIK in moderate-to-high myopia.

This study aims to compare the changes in the corneal wavefront aberrations and the objective visual quality resulting from two types of eye surgery-small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK)-in patients with moderate-to-high myopia. A prospective analysis was performed on 98 eyes of 51 patients who underwent SMILE. Additionally, 88 eyes of 45 patients who underwent FS-LASIK were analyzed. All patients underwent ocular examination preoperatively and at 1 day, 1 week, 1 month, and 3 months postoperatively. Corneal aberrations and objective visual quality were measured using the Optical Quality Analysis System II (OQAS II) and Optical Path Difference Scan III (OPD-Scan III). At postoperative 1 day and 1 week, there was a statistically significant difference in uncorrected distance visual acuity (UDVA) between SMILE and FS-LASIK (P < 0.05). Postoperative spherical (S), cylinder (C) and spherical equivalent refraction (SE) were similar between the two groups (P > 0.05). In both groups, the absolute magnitude of total higher-aberrations (tHOA), piston, vertical tilt, vertical coma, and spherical aberration (SA) increased after surgery compared to preoperative values (P < 0.05). There was no significant difference in Δhorizontal tHOA, Δhorizontal tilt, Δhorizontal coma, and Δhorizontal trefoil between the two groups (P > 0.05), and the FS-LASIK had higher Δvertical trefoil and ΔSA (P < 0.05) but lower Δpiston, Δvertical tilt, and Δvertical coma than the SMILE group (P < 0.05). There was a rise in objective scattering index (OSI) and a decline in both modulation transfer function (MTF) cutoff and Strehl ratio (SR) after surgery compared to preoperative values in both groups (P < 0.05). There was a statistically significant difference in the OSI at 1 day and 3 months between the two groups (P < 0.05). Postoperative MTF cutoff and SR were similar between the two groups (P > 0.05). Postoperative OSI was positively correlated with corneal tHOA (0.261 ≤ R ≤ 0.483, P < 0.05) and was negatively correlated with vertical tilt and vertical coma (-0.315 ≤ R ≤ -0.209, P < 0.05) in both groups. While both SMILE and FS-LASIK can effectively correct moderate-to-high myopia, there is an increase in corneal aberrations and a postoperative delay in objective visual quality. The cornea may require a longer recovery period in the SMILE. OPD-Scan III combined with OQAS II is a useful supplementary inspection for assessing the optical quality following refractive surgery.

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.

Topography-guided photorefractive keratectomy combined with accelerated corneal collagen cross-linking versus cross-linking alone for progressive keratoconus: a long-term prospective cohort study.

To comprehensively compare the long-term outcome of the combined topography guided photorefractive keratectomy (TG-PRK) with accelerated corneal cross-linking (ACXL) and ACXL alone in eyes with progressive keratoconus. The analysis focused on the changes in the detailed corneal aberrometric values. This single-center, prospective cohort study included 28 patients (30 eyes) of the TG-PRK plus ACXL group and 14 patients (15 eyes) of the ACXL alone group. The mean duration of the follow-up was 44 ± 10.18 months (ranged from 31 to 65 months). The preoperative data and the postoperative measurement data at the last follow-up visit, including demographic data, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, corneal topography, pachymetry, aberrometry and densitometry were analyzed. The CDVA significantly improved in the TG-PRK plus ACXL group at the last follow-up visit (p = 0.006), while no significant improvement was found in the ACXL alone group (p = 0.432). The maximal keratometry of the anterior corneal surface (Kmax) of both groups significantly decreased at the last follow-up visit (p < 0.05). Compared with the ACXL alone group, the Kmax of the TG-PRK plus ACXL group showed a greater decline (p = 0.008). The total corneal aberrations, the corneal lower-order aberrations (LOAs), the corneal higher order aberrations (HOAs), the vertical coma and the spherical aberration (SA) at the 4.0 mm and 6.0 mm zone of the TG-PRK plus ACXL group significantly decreased at the last follow-up visit (all p < 0.05). The declines of the total corneal aberrations, the corneal LOAs, the corneal HOAs and the vertical coma at the 4.0 mm and 6.0 mm zone of the TG-PRK plus ACXL group were significantly higher than those in the ACXL alone group (p < 0.001). Compared with ACXL alone, combined TG-PRK with ACXL procedure had a significantly higher reduction in the corneal HOAs and better CDVA, while providing a similar long-term stability and safety. For progressive keratoconus patients with adequate corneal thickness, the combined procedure might be a recommended treatment option.

Three-Month Comprehensive Outcomes of Topography-Guided LASIK Versus Keratorefractive Lenticule Extraction (KLEx): A Prospective Contralateral Study.

The aim of this study was to compare outcomes of topography-guided laser-assisted in situ keratomileusis (TG-LASIK) and small incision lenticule extraction (SMILE®) for correcting myopia and myopic astigmatism. In this prospective, randomized contralateral study, 34 patients (68 eyes) received TG-LASIK in one eye, and SMILE in their fellow eye. Efficacy, safety, predictability, higher-order aberrations, corneal tomography, biomechanics, and patient-reported outcomes (PROs) were assessed preoperatively and up to 3months postoperatively. Both platforms showed comparable efficacy at 3months (TG-LASIK 1.08 ± 0.19; SMILE 0.98 ± 0.17, p = 0.055). However, TG-LASIK demonstrated quicker visual recovery, with 63% and 89% achieving uncorrected distance visual acuity (UDVA) of 20/16 or better at 1day and 1week, respectively, compared to SMILE (34% and 63%; p < 0.05). Safety index at 3months did not significantly differ between TG-LASIK and SMILE (p = 0.223). TG-LASIK and SMILE had 44% and 56% of eyes within 0.13D of spherical equivalent (SEQ) target, respectively. SMILE induced more total higher-order aberrations (HOAs), vertical coma, and oblique trefoil than TG-LASIK at 3months (p < 0.05). Both platforms showed similar increases in epithelial remodeling, but SMILE induced thicker epithelium than TG-LASIK at the 7.0-mm nasal zonal area. No significant differences were found in corneal hysteresis (CH) or corneal resistance factor (CRF) at 3months (p > 0.05). Reported symptoms of glare, halos, rings, starbursts, or dry eye did not significantly differ between groups at 3months (p > 0.05). Overall, 59% of patients preferred their TG-LASIK treated eye at 1month, but 65% of patients had no specific eye preference at 3months. TG-LASIK and SMILE demonstrate excellent and comparable efficacy, safety, and predictability at 3months, but TG-LASIK offers faster postoperative visual recovery at 1day and 1week. TG-LASIK induces fewer HOAs than SMILE, but both procedures affect corneal biomechanics similarly. ClincialTrials.gov identifier, NCT05611294.

The HUC progression score: A new method for determining KERATOCONUS progression.

To establish new criteria for the progression of keratoconus, taking into account a Pentacam HR (high resolution) tomographeŕs repeatability limit. This is a retrospective observational study, including 224 eyes in 154 patients diagnosed with keratoconus and patients treated with crosslinking, with a follow-up of at least one year, in which the new progression score of the Cruces University Hospital for keratoconus progression was analyzed. This score takes into account: maximum keratometry, thinnest corneal thickness, maximum posterior elevation, vertical coma and RMS of high order aberrations, all based on the tomographer repeatability limit. The effectiveness or not of crosslinking was determined. The Receiver Operating Characteristics (ROC) curves obtained in our validation met the criteria by being far from the reference diagonal. Moreover, young patients are more likely to have keratoconus that progresses, and the percentage of patients that showed progression was 14.3% of the eyes studied, with the most advanced keratoconus showing the least progression. Taking into account the new progression score of the Cruces Hospital, we would have indicated crosslinking in 2 eyes only and we observed that none progressed one year after treatment. The the new progression score of the Cruces University Hospital is a method based on the real repeatability limit for keratoconic eyes. Moreover, it is easy to interpret and can be implemented with Pentacam software. It provides a numerical value that evaluates both the anterior and posterior surfaces of the cornea and corneal aberrations in the evolution of keratoconus.

Optical Characterization of a Rotationally Asymmetric Refractive Multifocal Intraocular Lens Compared to a Standard Monofocal One

This study compares a standard monofocal intraocular lens (IOL) with two rotationally asymmetric refractive multifocal IOLs, analyzing power profiles and wavefront data across three nominal powers. Tested IOLs included monofocal Acunex AN6 and multifocal AN6V (addition +1.50 D) and AN6VM (addition +3.00 D) by Teleon Surgical, at powers +10.00 D, +20.00 D, and +30.00 D. Using NIMO TR1504, power profiles, spherical aberration, and coma were analyzed. Multifocal lenses displayed an asymmetrical design, with zones for far and near vision and a central notch for far power. The multifocal AN6V and AN6VM showed neutral spherical aberration in the center, increasing to positive values, and finally achieving negative values towards the periphery. The vertical coma coefficient [Z(3:−1)] remains almost stable for the monofocal IOLs. The lower-addition multifocal IOLs induce primary vertical coma of +0.11 microns at 3 mm away from the lens center compared to +0.21 microns obtained with the high-addition lens. We can conclude that the multifocal AN6V and AN6VM lenses display an asymmetrical design. The final addition provided by these lenses depends on its nominal power. The variation of SA with optic size is more pronounced for the monofocal model, and it is dependent on the nominal power.

Comparison of visual outcomes and optical aberrations after SMILE with intraoperative Kappa angle adjustments between small and large Kappa angles

This study compares postoperative visual outcomes and optical aberrations after Small Incision Lenticule Extraction (SMILE) in patients with both small (S-Kappa: Kappa angle < 0.2 mm) and large Kappa (L-Kappa: Kappa angle ≥ 0.2 mm) angles. The evaluated aberrations include total higher-order aberrations (HOAs), horizontal coma (HC), vertical coma (VC), and spherical aberrations (SA), with procedures incorporating intraoperative Kappa angle adjustments. We retrospectively analyzed patient records undergoing SMILE utilizing linear mixed models (LMM). We assessed adjusted mean uncorrected distance visual acuity (UDVA), Strehl ratio (SR), total HOAs, VC, and SA at pupils of 3 mm and 6 mm for both S-Kappa and L-Kappa. The disparities between S-Kappa and L-Kappa were evaluated by LMM's adjusted mean differences. The differences in optical metrics were also assessed in eyes grouped by myopia levels: low, moderate, and high. A sensitivity analysis was conducted on a threshold of Kappa angle at 0.3 mm. Eight-five patients (169 eyes) were analyzed, and no significant pre-operative difference was found in UDVA (p = .222) or spherical equivalent (p = .433). Post-operative differences were found in SR at 3 mm pupil size (−0.06, p = .022), total HOA 3 mm (0.15, p = .022), HC 3 mm (0.04, p = .042), VC 3 mm and 6 mm (−0.08, p = .041; 0.04, p = .041). The stratified analysis for high myopia revealed significant differences in UDVA (−0.04, p = .037), HC 3 mm (0.07, p = .03), VC 6 mm (−0.21, p = .001), and SA 3 mm and 6 mm (0.07, p = .037; −0.09, p = .037). Sensitivity analysis showed no significant difference using a 0.3 mm Kappa threshold. While some optical aberrations exhibited statistical differences between S-Kappa and L-Kappa, their clinical significance is limited. Thus, a large Kappa angle might not substantially influence post-operative optical aberrations when intraoperative Kappa angle adjustments are implemented.

Wavefront Changes during a Sustained Reading Task in Presbyopic Eyes.

The objective of this study was to assess the effect of sustained reading on the temporal changes in the wavefront error in the presbyopic eye. The wavefront aberration of the eyes was measured using an IRX3 Shack-Hartmann aberrometer before and after (immediately, 5 min, and 10 min after) a reading task. Temporal changes in C20, C40, and C3-1 coefficient values of the eyes were plotted, showing a predominant number of V-shaped patterns (for C40 and C3-1) and inverse V-shaped patterns (for C20) among the study group, and the percentages (between 27 and 73%) were reported. The median of the total RMS of aberrations and the RMS of HOA (higher-order aberrations), which included comatic (3rd order) and spherical-like aberrations (4th and 6th order), increased immediately after finishing the near-vision reading task and then decreased. The median of RMS of comatic aberrations had a similar pattern of variations, while the median of RMS of spherical-like aberrations displayed an opposite pattern. Simulating the aberration changes due to lens decentration caused by relaxed zonules during 4 D accommodation in an eye model demonstrated that the expected range of changes for the vertical coma and spherical aberrations are in the order of 0.001 and 0.01 μm, respectively, which could justify why the observed changes were not statistically significant. The observed dynamic changes in HOA might be linked to the biomechanical characteristics and alterations in the displacement of the crystalline lens following prolonged near-vision tasks in presbyopic people. Although some predominant patterns under some conditions were shown, they exhibit considerable inter-subject and inter-ocular variability. This might be due to slight misalignments while fixating on the internal extended object in the aberrometer.

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.

Comparative Study of Primary SMILE, SMILE Enhancement, and Femtosecond Laser-Assisted LASIK on Higher Order Aberrations and Corneal Densitometry.

To compare differences in corneal densitometry (CD) and higher order aberrations (HOAs) in eyes that underwent small incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) for the treatment of myopia and myopic astigmatism at postoperative months 3, 6, and 12, and to evaluate their changes in a separate cohort of eyes after SMILE enhancement. In this prospective, randomized, paired-eye clinical trial, consecutive eligible participants were randomized to undergo SMILE or FS-LASIK in either eye. Main outcome measures were CD and HOAs preoperatively and at 3, 6, and 12 months postoperatively. A separate cohort of consecutive patients who had SMILE and underwent enhancement were also included for comparison. For CD, no significant differences were found between SMILE and FS-LASIK up to month 12. For HOA measured by wavefront aberrometry, both SMILE and FS-LASIK had an increase in total root mean square (RMS) HOAs, spherical aberration (SA), and vertical coma up to month 12. SMILE had an additional increase in vertical quatrefoil, and FS-LASIK had an increase in horizontal coma at month 12. FS-LASIK had higher SA than SMILE, whereas SMILE had higher vertical quatrefoil than FS-LASIK at month 12. Central and posterior zone CD had significantly decreased after SMILE enhancement compared to after primary SMILE up to 2 years after enhancement. RMS HOAs, lower order aberrations, and SA were all increased after SMILE enhancement compared to after primary SMILE. SMILE induced lower SA but higher vertical quatrefoil than FS-LASIK at 1 year. Both SMILE and FS-LASIK had similar increases in RMS HOAs and vertical coma up to 1 year. There were no differences in CD between both groups. SMILE enhancement additionally had decreased central and posterior CD but greater RMS HOAs and SA compared to primary SMILE. [J Refract Surg. 2024;40(5):e291-e303.].

Uneven Corneal Epithelial Redistribution After Femtosecond Laser-Assisted Lenticule Intrastromal Keratoplasty in Correcting Moderate-to-High Hyperopia.

To evaluate the characteristic of corrective epithelial thickness after femtosecond laser-assisted lenticule intrastromal keratoplasty (LIKE) to correct moderate-to-high hyperopia. The prospective case series study of the LIKE procedure was performed to correct moderate-to-high hyperopia. The epithelial thickness map was generated by anterior segment optical coherence tomography (AS-OCT) in the corneal central 9-mm zone. Keratometry and corneal higher order aberrations were analyzed by Pentacam (Oculus Optikgeräte GmbH) preoperatively and postoperatively. In the 26 eyes of 13 participants who underwent the LIKE procedure for moderate-to-high hyperopia, the attempted spherical equivalence (SEQ) was +6.50 ± 1.09 diopters (D). Compared to the preoperative epithelial thickness maps, the postoperative epithelial thickness had become significantly thinner in the central 5-mm zone; the difference was 6 to 7 µm. The paracentral epithelium performed nonuniform remodeling; the thinnest epithelial thickness was located in the inferotemporal section, which has the greatest difference from the superonasal; the difference between these two was approximately 3 µm. Through correlation analysis, it was found that the sections with thinner epithelium were significantly related to corneal curvature and corneal vertical coma. The LIKE procedure can be used to correct moderate-to-high hyperopia. This study further indicated the epithelial remodeling characteristic after the LIKE procedure: the central and paracentral corneal epithelial thickness becomes thinner, and the epithelial thickness distributes non-uniformly, which may be the important factor of the postoperative curvature asymmetric distribution and induction of corneal vertical coma. [J Refract Surg. 2024;40(5):e321-e327.].

Comparative visual outcomes of the first versus second eye following small-incision lenticule extraction (SMILE)

BackgroundThis study aimed to compare the visual outcomes of the first operated eyes with those of the second operated eyes following small-incision lenticule extraction (SMILE).MethodsA total of 202 patients (404 eyes) underwent SMILE using the tear film mark centration method for myopia and myopic astigmatism correction. Baseline characteristics, objective optical quality, decentered displacement, induced corneal aberrations, and modulation transfer function (MTF) values were assessed. Linear regression analyzed the relationship between decentration and visual quality parameters, including corneal aberrations and MTF values.ResultsNo significant difference was observed in objective visual quality, efficacy, and safety indexes between the two groups (all P > 0.05). The average decentered displacement for the first and second surgical eyes was 0.278 ± 0.17 mm and 0.315 ± 0.15 mm, respectively (P = 0.002). The horizontal coma in the first surgical eyes were notably lower than in the second (P = 0.000). MTF values at spatial frequencies of 5, 10, 15, and 20 cycles/degree (c/d) were higher in the first surgical eyes compared to the second (all P < 0.05). Linear regression indicated that high-order aberrations (HOAs), root mean square (RMS) coma, spherical aberration, horizontal coma, vertical coma, and eccentric displacement were all linearly correlated. Furthermore, MTF values exhibited a linear relationship with eccentric displacement across these spatial frequencies.ConclusionsThere was no discernible difference in visual acuity, efficacy, or safety between the two operated eyes. Nonetheless, the first operated eyes exhibited reduced decentered displacement and demonstrated superior outcomes in terms of horizontal coma and MTF values compared to the second operated eyes following SMILE. The variations in visual quality parameters were linearly correlated with decentered displacement.

Comparative Analysis of Corneal Higher-Order Aberrations after Laser-Assisted In Situ Keratomileusis, Photorefractive Keratectomy, and Small Incision Lenticule Extraction with Correlations to Change in Myopic Q-Value and Spherical Equivalent with and without Astigmatism.

Background: This retrospective chart review compared the higher-order aberrations (HOAs) among photorefractive keratectomy (PRK), laser-assisted in situ keratomileusis (LASIK), and small incision lenticule extraction (SMILE) alongside changes in spherical equivalent (SEQ) and corneal shape (Q-value). Methods: Analyzing 371 myopic eyes, including 154 LASIK, 173 PRK, and 44 SMILE cases, Pentacam imaging was utilized pre-operatively and at one-year post-operative visits. Results: All procedures resulted in 100% of patients achieving an uncorrected distance visual acuity (UDVA) of 20/40 or better, with 87% of LASIK and PRK, and 91% of SMILE patients having 20/20 or better. Significant increases in HOAs were observed across all procedures (p < 0.05), correlating positively with SEQ and Q-value changes (LASIK (0.686, p < 0.05), followed by PRK (0.4503, p < 0.05), and SMILE (0.386, p < 0.05)). Vertical coma and spherical aberration (SA) were the primary factors for heightened aberration magnitude among the procedures (p < 0.05), with the largest contribution in SMILE, which is likely attributed to the centration at the corneal apex. Notably, PRK showed insignificant changes in vertical coma (-0.197 µm ± 0.0168 to -0.192 µm ± 0.0198, p = 0.78), with an increase in oblique trefoil (p < 0.05). Conclusions: These findings underscore differences in HOAs among PRK, LASIK, and SMILE, helping to guide clinicians.

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.