The effect of cycloplegia in the accuracy of autorefraction, keratometry and axial length using the Myopia Master.

BACKGROUND: Assessing refractive errors under cycloplegia is recommended for paediatric patients; however, this may not always be feasible. In these situations, refraction has to rely on measurements made under active accommodation which may increase measurements variability and error. Therefore, evaluating the accuracy and precision of non-cycloplegic refraction and biometric measurements is clinically relevant. The Myopia Master, a novel instrument combining autorefraction and biometry, is designed for monitoring refractive error and ocular biometry in myopia management. This study assessed its repeatability and agreement for autorefraction and biometric measurements pre- and post-cycloplegia. METHODS: A prospective cross-sectional study evaluated a cohort of 96 paediatric patients that underwent ophthalmologic examination. An optometrist performed two repeated measurements of autorefraction and biometry pre- and post-cycloplegia. Test-retest repeatability (TRT) was assessed as differences between consecutive measurements and agreement as differences between post- and pre-cycloplegia measurements, for spherical equivalent (SE), refractive and keratometric J0/J45 astigmatic components, mean keratometry (Km) and axial length (AL). RESULTS: Cycloplegia significantly improved the SE repeatability (TRT, pre-cyclo: 0.65 D, post-cyclo: 0.31 D). SE measurements were more repeatable in myopes and emmetropes compared to hyperopes. Keratometry (Km) repeatability did not change with cycloplegia (TRT, pre-cyclo: 0.25 D, post-cyclo:0.27 D) and AL repeatability improved marginally (TRT, pre-cyclo: 0.14 mm, post-cyclo: 0.09 mm). Regarding pre- and post-cycloplegia agreement, SE became more positive by + 0.79 D, varying with refractive error. Myopic eyes showed a mean difference of + 0.31 D, while hyperopes differed by + 1.57 D. Mean keratometry, refractive and keratometric J0/J45 and AL showed no clinically significant differences. CONCLUSIONS: Refractive error measurements, using the Myopia Master were 2.5x less precise pre-cycloplegia than post-cycloplegia. Accuracy of pre-cycloplegic refractive error measurements was often larger than the clinically significant threshold (0.25 D) and was refractive error dependent. The higher precision compared to autorefraction measurements, pre- and post-cycloplegia agreement and refractive error independence of AL measurements emphasize the superiority of AL in refractive error monitoring.

Association of choroidal thickness and blood flow features with asymmetric axial lengths in children with unilateral myopic anisometropia.

BACKGROUND: Considering that changes in the choroidal thickness are closely related to ocular growth, we studied the choroidal thickness (CT) and the blood flow features in children with unilateral myopic anisometropia (UMA) as well as investigating the relationship between choroidal changes and myopia. METHODS: Subjective refractive, axial length (AL), and biometric parameters were measured in 98 UMA children (age: 8-15 years). CT and choroidal blood-flow features, including the choroidal vessel volume (CVV), choroidal vascularity index (CVI), and choriocapillaris perfusion area (CCPA), were measured through swept-source optical coherence tomography angiography. The macular region was categorized into four concentric circles of diameters 0-1 mm (central fovea), 1-3 mm (parafovea), 3-6 mm (perifovea), and 6-9 mm (extended), and further categorized into superior (S), inferior (I), temporal (T), and nasal (N) quadrants. RESULTS: The aforementioned four regions of myopic eyes displayed significantly lower CT, CVV, and CVI than those of non-myopic eyes. CCPA changes differed across different regions of both the eyes (parts of N and T quadrants). There was an inverse association between CT and the interocular AL difference (central and other regions S, T quadrant). No correlation was noted between CVV and CVI with interocular AL difference. CT and CVV were positively correlated in the 0-6-mm macular region of myopic eyes (Spearman correlation coefficient = 0.763, P < 0.001). CONCLUSIONS: In UMA children, CCT and blood flow may be related to myopia progression. A robust correlation between CT and CVV in the 0-6-mm macular region and reduced CT and diminished blood flow indicated an association with myopia.

Peripheral Ganglion Cell Complex Thickness and Retinal Microvasculature in Myopia Using Wide-Field Swept-Source OCT.

Purpose: This study aims to investigate the impact of axial elongation on ganglion cell complex thickness (GCCT) and retinal capillary density (CD) using wide-field swept-source optical coherence tomography angiography. Methods: A retrospective cross-sectional analysis was conducted involving 506 eyes. Fovea-centered scans were obtained to assess the subregional GCCT and capillary density across the whole retina, the superficial capillary plexus (SCP), and deep capillary plexus (DCP) among three groups: normal control, high myopia (HM) eyes with axial length < 28 mm, and HM eyes with axial length > 28 mm. Regional variations (central vs. peripheral, quadrants difference [superior, inferior, nasal, and temporal]) were analyzed. Results: In HM eyes with axial length > 28 mm, GCCT and retinal CD exhibit a general decline in most regions (P < 0.05). In HM eyes with axial length < 28 mm, significant reductions were observed specifically in peripheral regions, as in the GCCT beyond the 3 × 3 mm2 area and CD in the 9-12 mm whole retina, 9-12 mm superior SCP, and 6-12 mm DCP (P < 0.05). Maximum GCCT and retinal CD reduction with axial elongation was observed in subregions beyond 6 × 6  mm2. Conclusions: GCCT beyond the 3 × 3 mm2 area and peripheral retinal CD beyond the 6 × 6  mm2 area were more susceptible to axial elongation and are thereby deserving of particular attention. Translational Relevance: It is necessary to evaluate different regions during the clinical assessment of the effect of myopia on the fundus and pay close attention to the peripheral retina.

Comparison between cycloplegic and noncycloplegic refraction in young adult myopes.

SIGNIFICANCE: This study explores the difference between cycloplegic and noncycloplegic refraction in young adult myopes. PURPOSE: From the available literature, it is unclear whether cycloplegia is necessary when refracting young adults. This study investigates the agreement between noncycloplegic autorefraction and cycloplegic autorefraction and investigates factors affecting the agreement between the two methods. METHODS: In total, 125 myopes with ages ranging between 18 and 26 years were included from Australia and Vietnam. Each participant underwent noncycloplegic autorefraction and cycloplegic autorefraction. Cycloplegia was induced with 1% ophthalmic tropicamide. RESULTS: The mean spherical equivalent difference (95% confidence interval) between noncycloplegic autorefraction and cycloplegic autorefraction was -0.20 D (-0.25 to -0.14 D; t124 = -7.18, p<0.0001 ) . A mean difference of >0.25 D was seen in 46.8% of eyes. The lower and upper limits of agreement were -0.80 and 0.41 D, respectively. With univariate analysis, factors including age, degree of refractive error, accommodation amplitude, and distance phorias showed no impact on the average difference between cycloplegic autorefraction and noncycloplegic autorefraction. Yet, eyes with near exophoria ( F2,120 = 6.63, p=0.0019) and Caucasian eyes ( F3,121 = 2.85, p=0.040) exhibited the smallest paired differences. However, in the multivariate analysis, only near exophoria was associated with a lower mean difference. A significantly smaller proportion (34.9%) of eyes with near exophoria had a paired difference of -0.25 D or more compared with esophoria (50%) and orthophoria (65%; χ2 = 6.6, p=0.038). CONCLUSIONS: Noncycloplegic autorefraction results in more myopic refractive error than cycloplegic autorefraction in young adults.

Clinical observations of EVO-ICL implantation with single incision without viscoelastic agent.

BACKGROUND: To investigate the safety and effectiveness of non-viscoelastic agent technique for EVO-ICL implantation. METHODS: A total of 181 myopia eyes that underwent non-toric ICL without viscoelastic agent through single incision from Beijing Tongren Hosipital were included. An analysis was conducted on the quantity of haptics that were initially implanted intraoperatively into the posterior chamber. Intraocular pressure (IOP) was evaluated at before and 2 h,24 h,1week,6month after surgery. Anterior chamber volume(ACV), anterior chamber depth(ACD), anterior chamber angle(ACA), pupil diameter(PD) and corneal densitometry density (ECD) were evaluated at before and 24 h postoperatively. Refractive outcomes were investigated at before, 24 h ,7 days and 6months. Vault was evaluated at 24 h ,7 days and 6months. RESULTS: The efficacy and safety indices were 1.30 ± 0.32 and 1.31 ± 0.32, respectively. Of 181 eyes, 99 eyes received 4 haptics on the first attempt without any adjustment, and 72 eyes received lens alignment without an viscoelastic agent. The success rate of the viscoelastic agent free procedure was 94.5%. Two hours postoperatively, IOP was 17.41 ± 3.77 mmHg, which was significantly higher than baseline value (t = 8.930, P < 0.000), however there was no significant difference between preoperative IOP and IOP at 1 day ,1 week and 6 months postoperatively. The ECD changed from 2895.52 ± 253.73 cells/mm2 preoperatively to 2873.66 ± 244.17 cells/mm2 at 1 day and 2882.63 ± 239.97 postoperatively, and the difference was not statistically significant (t = 1.811, P = 0.072). The ACA was narrowed by 42% on the first day. CONCLUSION: The pure viscoelastic agent free technique is an efficient and safe way for ICL implantation. It can be a safer method of ICL implantation because of it reduces the risk of complications associated with ocular hypertension at the early postoperative stages. TRIAL REGISTRATION: Chinese Clinical Trial Registry (ChiCTR2000036335) at August 20, 2020.

Progressive Paracentral Visual Field Loss at Low Intraocular Pressures Following LASIK.

Intraocular pressure is currently the only known reliable, modifiable risk factor for the development and progression of glaucoma. Other risk factors for glaucoma include increasing age, myopia, decreased central corneal thickness, and low corneal hysteresis (CH) measurements. Photoablative keratorefractive surgery including laser assisted in situ keratomileusis (LASIK) has become a common way to treat refractive error, with over 25 million procedures performed in the United States alone. Though myopic LASIK has been associated with a decrease in CH measurements, relatively little is known about the risk of LASIK on glaucoma onset and progression. Here we present an observational study of 4 consecutive relatively young and otherwise healthy glaucoma patients with a history of myopic LASIK who showed progression of paracentral visual field deficits at intraocular pressures of 12 mm Hg or less while being carefully monitored. Therefore, these patients required lower targets of intraocular pressure, in the single-digit range, to slow or halt progression. In this cohort, the average corneal hysteresis was more than 2 standard deviations below normal values. This series suggests that additional study into the association of LASIK and glaucoma is warranted, including the potential risk contribution of diminished CH. These studies may be particularly relevant as patients who underwent LASIK procedures in the early 2000s may now be at increased risk of glaucoma due to the risk factor of age.

Choroidal Changes During and After Discontinuing Long-Term 0.01% Atropine Treatment for Myopia Control.

Purpose: Few studies have explored choroidal changes after cessation of myopia control. This study evaluated the choroidal thickness (ChT) and choroidal vascularity index (CVI) during and after discontinuing long-term low-concentration atropine eye drops use for myopia control. Methods: Children with progressive myopia (6-16 years; n = 153) were randomized to receive 0.01% atropine eye drops or a placebo (2:1 ratio) instilled daily over 2 years, followed by a 1-year washout (no eye drop use). Optical coherence tomography imaging of the choroid was conducted at the baseline, 2-year (end of treatment phase), and 3-year (end of washout phase) visits. The main outcome measure was the subfoveal ChT. Secondary measures include the CVI. Results: During the treatment phase, the subfoveal choroids in both treatment and control groups thickened by 12-14 µm (group difference P = 0.56). During the washout phase, the subfoveal choroids in the placebo group continued to thicken by 6.6 µm (95% confidence interval [CI] = 1.7 to 11.6), but those in the atropine group did not change (estimate = -0.04 µm; 95% CI = -3.2 to 3.1). Participants with good axial eye growth control had greater choroidal thickening than the fast-progressors during the treatment phase regardless of the treatment group (P < 0.001), but choroidal thickening in the atropine group's fast-progressors was not sustained after stopping eye drops. CVI decreased in both groups during the treatment phase, but increased in the placebo group after treatment cessation. Conclusions: On average, compared to placebo, 0.01% atropine eye drop treatment did not cause a differential rate of change in ChT during treatment, but abrupt cessation of long-term 0.01% atropine eye drops may disrupt normal choroidal thickening in children.

Comparative analysis of surgically induced astigmatism following cataract surgery: influence of previous myopic correction and corneal parameters.

PURPOSE: This retrospective study investigated the impact of corneal parameters on surgically induced astigmatism (SIA) in eyes with prior myopic correction undergoing cataract surgery. SETTING: Department of Ophthalmology, San Marino Hospital, San Marino, Republic of San Marino. DESIGN: This case-control study analyzed existing data retrospectively, without randomization or masking. METHODS: Eighty eyes divided in group 1 (40 eyes previous underwent refractive surgery for myopia) and group 2 ( 40 myopic eyes) that underwent cataract surgery with intraocular lens (IOL) implantation were included. SIA was calculated using values from the IOL Master Zeiss 700 and mean pupil power (MPP) derived from the CSO Sirius Topographer (based on 3 mm pupil size) with vectorial analysis from doctor Hill software. RESULTS: No significant difference in SIA was observed between eyes with prior myopic photorefractive keratectomy and the control group (p > 0.05). SIA calculations using the IOL Master and CSO Sirius Tomographer yielded similar results. There was no significant correlation between SIA and axial length, corneal curvature, peripheral corneal thickness, or anterior chamber depth (p > 0.05). However, an inverse correlation was found between SIA and horizontal corneal diameter (p < 0.05). CONCLUSIONS: Corneal parameters, such as axial length, corneal curvature, peripheral corneal thickness, and anterior chamber depth, showed no significant influence on SIA. The inverse correlation between SIA and horizontal corneal diameter in study group suggests potential influence of white-to-white distance on SIA. These findings highlight the importance of considering corneal parameters for optimizing surgical outcomes.

A clearer vision: unveiling the importance of cycloplegic refraction and the pseudomyopia prevalence in Chinese preschoolers.

BACKGROUND: This study aimed to investigate the difference between cycloplegic and noncycloplegic refraction and evaluate the pseudomyopia prevalence in Chinese preschool children during the outbreak of COVID-19. METHODS: A cross-sectional study was conducted in the Tongzhou District of Beijing, China. Refractive error was measured under both noncycloplegic and cycloplegic conditions with autorefraction. The difference between noncycloplegic and cycloplegic spherical equivalent refraction (SER) and pseudomyopia prevalence were analyzed. Pseudomyopia was defined as SER ≤-0.50D in precycloplegic assessments and >-0.50D in post-cycloplegic assessments. RESULTS: Out of the 1487 participants who were enrolled in the study, 1471 individuals (98.92%) between the ages of 3-6 years completed all required procedures. A statistically significant difference in refraction was observed between noncycloplegic and cycloplegic measurements, the median of difference in spherical equivalent refraction (SER) of 0.88D (dioptre)(0.50,1.38). There was a high intraclass correlation (ICC) between these two methods for cylinders (ICC = 0.864; 95% CI, 0.850-0.877). The median DSE for myopia, emmetropia and hyperopia were 0.25D (0.00, 0.38),0.25D (0.06, 0.50) and 1.00D (0.62, 1.38), an hypermetropes showed considerably greater differences than myopes and emmetropes (Kruskal-Wallis test, H = 231.023, P = 0.000). Additionally, girls displayed a greater DSE than boys. Furthermore, when comparing against-the-rule (ATR) and oblique astigmatism, it was found that with-the-rule (WTR) astigmatism had the largest DSE. The study found varying prevalence rates of myopia, emmetropia, and hyperopia with and without cycloplegia, which were 1.90% vs. 10.06%, 11.49% vs. 50.31%, and 86.61% vs. 39.63%, respectively. Additionally, the overall prevalence of pseudomyopia was determined to be 8.29%. Participants with pseudomyopia had a significantly higher mean difference in SER (DSE) compared to non-pseudomyopic participants. CONCLUSIONS: Cycloplegic refraction is more sensitive than a noncycloplegic one for measuring refractive error in preschool children. Pseudomyopia is prevalent in preschool children during the COVID-19 outbreak period. Our study indicates the possibility that cycloplegic refraction should be performed in preschool children routinely.

Clinical outcomes after topography-guided FS-LASIK for myopia with nonastigmatic eyes.

BACKGROUND: To analyze the clinical outcomes after topography-guided femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) with Phorcides Analytic Engine (PAE) algorithm or Custom-Q FS-LASIK for myopia with nonastigmatic eyes. METHODS: In this retrospective study, a total of 90 eyes with myopia without manifest astigmatism (82 patients) were included. All surgeries were performed by topography-guided FS-LASIK planned with a PAE algorithm (42 eyes) or Custom-Q system (48 eyes). Refractive, visual outcomes and corneal aberrations were compared between the two groups. RESULTS: At 6 months postoperatively, the postoperative uncorrected distance visual acuity (UDVA) was 20/20 or better in 42 eyes (100%) in the PAE compared with 44 eyes (92%) in Custom-Q (P = .120). The postoperative UDVA of 20/16 or better was measured in 92% of eyes in the PAE group and 81% of eyes in the Custom Q group (P = .320). Postoperative corrected distance visual acuity, manifest refractive spherical equivalent and refractive astigmatism were similar between the two groups (P > .05). The postoperative optical path difference (OPD) and Strehl ratio (SR) were significantly better in the PAE group compared with the Custom Q group. CONCLUSIONS: Topography-guided FS-LASIK with PAE algorithm or Custom Q demonstrated similar refractive efficacy and predictability. PAE for the patients with zero manifest astigmatism demonstrated better results in correcting corneal aberrations.

LASIK Versus PRK Based on Increased Risk of Corneal Haze: Assessing Current Decision-Making Capabilities of Six Artificial Intelligence Models in Refractive Surgery.

PURPOSE: To investigate the current decision-making capabilities of 6 different artificial intelligence (AI) models by assessing their refractive surgery recommendations (laser in-situ keratomileusis [LASIK] or photorefractive keratectomy [PRK]) for a theoretical patient with a history of keloid formation. METHODS: Claude-2 (Anthropic, 2023), GPT-4 (OpenAI, 2023), GPT-3.5 (OpenAI, 2022), Gemini 1.0 (Google DeepMind, 2023), Microsoft Copilot (Microsoft AI, 2023), and Google-PaLM (Google AI, 2022) underwent three systematic queries to determine the most appropriate surgical plan (LASIK or PRK) for a theoretical patient with an increasing manifest refraction of -3.50, -5.00, and -7.00 diopters (D) in both eyes, an uncomplicated ocular examination, and history of keloid formation. They were then tasked with providing published scientific references to support their responses. The AI models' recommendations were compared to those of a group of 6 experienced ophthalmologists, serving as a benchmark. RESULTS: The group of ophthalmologists unanimously recommended LASIK (6/6 ophthalmologists), in contrast to the unanimous initial recommendation for PRK from the AI models (6/6 models). Of the 42 references provided by the AI models, 55% were fictitious and 45% were authentic. Only 1 of the 6 models altered its initial recommendation to LASIK when presented with the same patient with a history of keloid formation but with increasing severity of myopia (-3.50 to 5.00 to 7.00 D). DISCUSSION: It is evident that current AI models lack the critical-thinking abilities required to accurately analyze and assess apparent risk factors in clinical scenarios, such as the risk of corneal haze after PRK at higher levels of myopia, particularly in cases with a history of keloid formation. [J Refract Surg. 2024;40(8):e533-e538.].

Impact and Correction of an Anterior Phakic Intraocular Lens on Swept-Source Optical Coherence Tomography Biometry.

PURPOSE: To evaluate the impact of anterior chamber phakic intraocular lens (pIOL) on swept-source optical coherence tomography (SS-OCT) biometric measurements and IOL power calculation. METHODS: This retrospective analysis of 67 eyes of 49 patients with previous anterior chamber pIOL implantation analyzed the accuracy of automatic segmentation of the anterior surface of the crystalline lens and its impact on anterior chamber depth (ACD, measured from epithelium to lens), lens thickness measurements, and IOL power calculation. The sample was divided into two groups: correct detection of the anterior surface of the crystalline lens and inaccurate detection. Segmentation of eyes from the inaccurate detection group was manually corrected and ACD and lens thickness were calculated using ImageJ software. IOL power was calculated using 7 formulas for both measurements. RESULTS: The anterior surface of the crystalline lens was mis-identified in 13 (19.4%) eyes. ACD was underestimated (Δ -0.85 ± 0.33 mm, P < .001) and lens thickness was overestimated (Δ +0.81 ± 0.25 mm, P < .001). Manual correction changed the target spherical equivalent only in the Haigis formula (P = .009). After correction for segmentation bias, the Pearl DGS, Cooke K6, and EVO 2.0 formulas showed the lowest prediction error, with the Pearl DGS showing greatest accuracy within ±1.00 diopters of prediction error range (81.0%). CONCLUSIONS: SS-OCT biometry misidentifies the anterior surface of the crystalline lens in a significant proportion, resulting in significant IOL power calculation error in the Haigis formula. Manual proofing of segmentation is mandatory in every patient with anterior chamber pIOL implantation. After correct segmentation, the Pearl DGS, Cooke K6, and EVO seem to be the best formulas. [J Refract Surg. 2024;40(8):e562-e568.].

Safety and Effectiveness of Laser in Situ Keratomileusis Using the Teneo 317 Model 2 for Correcting Myopia and Myopic Astigmatism: Results of the U.S. FDA Clinical Trial.

PURPOSE: To evaluate the safety and effectiveness of a new aspheric ablation profile for correcting myopia and myopic astigmatism. METHODS: This prospective, multicenter study included patients who underwent laser in situ keratomileusis (LASIK) using a new aspheric ablation profile of the Technolas Teneo 317 (Model 2) excimer laser (version 1.28 US SW) by Technolas Perfect Vision, Bausch+Lomb, Inc. No nomogram adjustments were made, and the patient's manifest refraction was entered into the laser (for treatment). Postoperative assessments included visual and refractive outcomes. Patients were asked to complete the Patient-Reported Outcomes With LASIK (PROWL) questionnaire preoperatively and postoperatively. RESULTS: A total of 333 eyes from 168 patients with a mean age of 33 ± 7 years were included. At postoperative 9 months, uncorrected and corrected distance visual acuities of 20/25 or better were seen in 97.8% and 100% of eyes, respectively. None of the eyes lost two or more lines of corrected distance visual acuity. The mean manifest spherical refraction improved from -5.67 ± 2.52 diopters (D) preoperatively to -0.04 ± 0.32 D postoperatively, with 92.7% of eyes achieving residual refractive error within ±0.50 D. Residual refractive cylinder within ±0.50 and ±1.00 D was seen in 93% and 99.4% eyes, respectively. The refractive outcomes were stable throughout the follow-up of 9 months. The proportion of patients satisfied with their vision rose from 27.7% preoperatively to 98.1% postoperatively. CONCLUSIONS: LASIK performed using a new aspheric ablation profile of the Technolas Teneo 317 (Model 2) excimer laser is safe and effective for correcting myopia and myopic astigmatism, yielding excellent visual and refractive outcomes that were stable over 9 months. [J Refract Surg. 2024;40(8):e544-e553.].

Clinical Characteristic and Tear Film Biomarkers After Myopic FS-LASIK: 1-Year Prospective Follow-up.

PURPOSE: To assess the long-term (1-year) effect of myopic femtosecond laser-assisted in situ keratomileusis (FSLASIK) on clinical characteristics and tear film biomarkers. METHODS: Eighty eyes from 80 patients who underwent FSLASIK were evaluated. Ocular surface symptoms and signs were evaluated using specific questionnaires and tests. The corneal nerves and dendritic cells were examined using in vivo confocal microscopy. Corneal sensitivity was evaluated using a Cochet-Bonnet esthesiometer. Tear inflammatory cytokines and neuropeptides were evaluated using Luminex immunoassay. These examinations were performed preoperatively and at 1, 3, 6, and 12 months postoperatively. RESULTS: Seventy-three participants completed all follow-up visits. Following FS-LASIK, ocular symptoms and signs (except Schirmer I test) worsened at 1 month but corneal and conjunctival stainings improved by 3 months. The numbers of dendritic cells and activated dendritic cells increased at the 3-month postoperative visit and recovered to preoperative levels by the 6-month visit. Ocular symptoms and corneal sensitivity recovered to preoperative levels at the 12-month visit. Tear break-up time and corneal nerve morphology were not recovered to preoperative status at the 12-month visit. Interleukin (IL)-1ß, IL-17A, tumor necrosis factor-α, and substance P tear levels significantly increased at all postoperative visits compared to preoperative levels. Corneal staining scores positively correlated with tear IL-1ß and IL-17A levels, whereas corneal nerve morphology positively correlated with corneal sensitivity and negatively correlated with substance P levels. CONCLUSIONS: Although most clinical variables improved at 12 months postoperatively, some tear inflammatory cytokines and substance P remain altered beyond 12 months, indicating that ocular homeostasis is not completely recovered. [J Refract Surg. 2024;40(8):e508-e519.].

Comparison of clinical outcomes of a corneal wavefront- and topography-guided platforms for laser in situ keratomileusis on virgin eyes: an expanded cohort study.

PURPOSE: To compare the clinical outcomes of myopiacorrected with corneal-wavefront-guided (CWG) laser in situ keratomileusis (LASIK) with AMARIS 1050S (SCHWIND eye-tech-solutions GmbH & Co. KG) and corneal-topography-guided (CTG) LASIK with WaveLight EX500 (Alcon Laboratories, Fort Worth, TX). METHODS: In this prospective, pseudo-randomized expanded cohort study, a total of 266 patients were subjected to binocular LASIK surgery, either with WaveLight EX500 (WaveLight group) or Amaris 1050S (AMARIS group) platforms. Data related to right eyes were selected for analysis. Corneal higher-order aberration (HOA) was selected as the primary endpoint; while visual acuity and refraction were the secondary endpoints. All the endpoints were assessed at 3 months postoperatively. RESULTS: There were 134 eyes in the AMARIS group and 132 eyes in the WaveLight group. After 3 months of postoperative follow-up, spherical and coma aberrations were significantly lower (P < 0.05) in the WaveLight group (spherical aberration: - 0.104 ± 0.199 µm; coma aberration: - 0.117 ± 0.202 µm) in comparison with the AMARIS group (spherical aberrations: 0.254 ± 0.146 µm; coma aberrations: 0.316 ± 0.297 µm). In the AMARIS group, 96.3% of the eyes achieved an uncorrected distance visual acuity (UDVA) of 20/20 while in the WaveLight group, 96.2% of the eyes achieved an UDVA of 20/20. Furthermore, the mean postoperative manifest refraction spherical equivalent (MRSE) was - 0.02 ± 0.28 in the AMARIS group and - 0.05 ± 0.21 in the WaveLight group (P = 0.34). CONCLUSIONS: Both WaveLight EX500 and Amaris 1050S LASIK showed excellent refractive and visual outcomes. In addition, the WaveLight group showed minimal spherical and coma aberrations when compared to the AMARIS group.

Early elastic and viscoelastic corneal biomechanical changes after photorefractive keratectomy and small incision lenticule extraction.

PURPOSE: To compare early changes in the corneal biomechanical parameters after photorefractive keratectomy (PRK) and small incision lenticule extraction (SMILE) and their correlations with corneal shape parameters. METHODS: One hundred twenty four eyes received myopic PRK and SMILE for similar amounts of myopia. Corneal tomography with Pentacam HR, biomechanical parameters using Corvis ST, and Ocular Response Analyzer (ORA) were evaluated before and 2 weeks after surgery. The change in each parameter was compared between groups, while the difference in central corneal thickness and cornea-compensated intraocular pressure measured before and after surgery were considered as covariates. RESULTS: A significant reduction was seen in the corneal stiffness parameter at first applanation, and an increase in deformation amplitude ratio (DAR), and integrated inverse radius (IIR) in both groups after surgery (p < 0.001) Changes in DAR, and IIR were significantly greater in the SMILE than in the PRK group (p < 0.001) Corneal hysteresis (CH) and corneal resistance factor (CRF) decreased in both SMILE and PRK groups after surgery, (p < 0.001) with no statistically significant difference between groups (p > 0.05) Among new Corvis ST parameters, DAR showed a significant correlation with changes in Ambrosio relational thickness in both groups (p < 0.05). CONCLUSIONS: Both techniques caused significant changes in corneal biomechanics in the early postoperative period, with greater elastic changes in the SMILE group compared to the PRK group, likely due to lower tension in the SMILE cap and thinner residual stromal bed in SMILE. There were no differences in viscoelastic changes between them, so the lower CH may reflect the volume of tissue removed.

[A preliminary study on the characteristics of refractive parameters and retinal blood flow in dominant eyes].

Objective: To explore the characteristics of refractive parameters and retinal and choroidal blood flow in dominant and non-dominant eyes. Methods: A cross-sectional study. Students who were 18 to 32 years old and had emmetropia or myopia but no systemic diseases were recruited from universities in Wuhu, Anhui Province from April 2019 to August 2023. They were divided into 4 groups based on the difference in spherical equivalent between two eyes:<0.50 D (group A), 0.50 to 1.74 D (group B), 1.75 to 2.49 D (group C), and≥2.50 D (group D). The card hole method was used to determine the dominant eye. The refractive parameters of both eyes were recorded, including spherical equivalent, myopia degree, astigmatism degree, axial length, and corneal curvature difference (K2-K1). Optical coherence tomography angiography was performed to measure the blood flow density of the superficial retinal capillaries, deep retinal capillaries (DVC), avascular layer (AC), entire retina, choroidal capillaries, and choroidal vessels, as well as the retina and choroid as a whole. Statistical analysis was conducted using the paired sample t-test, chi square test, and variance analysis. Results: A total of 78 eligible subjects, aged (24.50±2.36) years old, 28 males and 50 females, were included. Fifty subjects had the right eye and 28 had the left eye as the dominant eye. Forty-two subjects had high myopia in the dominant eye, and 30 had high myopia in the non-dominant eye. There were statistically significant differences (all P<0.05) in the spherical equivalent [(-4.588±2.534) D vs. (-4.058±2.453) D], myopic spherical power [(-4.253±2.504) D vs. (-3.779±2.425) D], and axial length [(25.531±1.212) mm vs. (25.256±1.238) mm] between dominant and non-dominant eyes among all subjects, as well as in the astigmatism degree of groups A and C, spherical power of groups B to D, and spherical power and axial length of groups C and D. There were also statistically significant differences (all P<0.05) in the blood flow density of the DVC [(0.291±0.130) vs. (0.257±0.148)], AC [(0.347±0.118) vs. (0.326±0.126)], and overall retina and choroid [(0.385±0.102) vs. (0.349±0.084)] between dominant and non-dominant eyes among all subjects, as well as in the blood flow density of the superficial retinal capillaries, DVC, AC, choroidal capillaries, and overall retina and choroid of groups C and D, density of the choroidal vessels of group C, and density of the entire retina of group D. Conclusions: In young individuals with emmetropia or near vision, the degree of myopia in dominant eyes is higher than that in non-dominant eyes. When the difference in the spherical equivalent between two eyes is ≥1.75 D, the blood flow density of the retina and choroid in the dominant eye is greater than that in the non-dominant eye.

Wide-field optical eye models for emmetropic and myopic eyes.

Ocular wavefront aberrations are used to describe retinal image formation in the study and modeling of foveal and peripheral visual functions and visual development. However, classical eye models generate aberration structures that generally do not resemble those of actual eyes, and simplifications such as rotationally symmetric and coaxial surfaces limit the usefulness of many modern eye models. Drawing on wide-field ocular wavefront aberrations measured previously by five laboratories, 28 emmetropic (-0.50 to +0.50 D) and 20 myopic (-1.50 to -4.50 D) individual optical eye models were reverse-engineered by optical design ray-tracing software. This involved an error function that manipulated 27 anatomical parameters, such as curvatures, asphericities, thicknesses, tilts, and translations-constrained within anatomical limits-to drive the output aberrations of each model to agree with the input (measured) aberrations. From those resultant anatomical parameters, three representative eye models were also defined: an ideal emmetropic eye with minimal aberrations (0.00 D), as well as a typical emmetropic eye (-0.02 D) and myopic eye (-2.75 D). The cohorts and individual models are presented and evaluated in terms of output aberrations and established population expectations, such as Seidel aberration theory and ocular chromatic aberrations. Presented applications of the models include the effect of dual focus contact lenses on peripheral optical quality, the comparison of ophthalmic correction modalities, and the projection of object space across the retina during accommodation.