Mean Keratometry Research Articles

A novel sandwich technique of minimally invasive surgery for corneal perforation.

This study aimed to describe a novel sandwich technique of minimally invasive surgical implantation by using corneal stromal lenticules for corneal perforation. This prospective observational study included nine patients aged 23-79 years (mean, 54 ± 9) from Tianjin Eye Hospital. Corneal stromal lenticules with a central thickness of 120μm were obtained from small incision lenticule extraction(SMILE). With the corneal perforation as the central point, an iris-repositor was used to manually create a mid-stromal pocket; the stromal lenticular button was gently inserted into the intrastromal pocket and flattened. The graft was sandwiched between the anterior and posterior corneal stromal pockets; the incision was closed using two sutures. The primary health outcome measured in this study was the logMAR best spectacle-visual acuity at 6 months postoperatively. Corneal perforation closure and anterior chamber formation occurred immediately after surgery. No epithelial implantation, infection, or allogeneic rejection was observed during the follow-up. No patients required a penetrating keratoplasty. Anterior segment optical coherence tomography revealed a mean thickness of the grafted tissue of 122 ± 21μm, with a clear interface in all cases. Comparing the baseline and postoperative 6-month values, the mean logMAR best spectacle-corrected visual acuity was improved from 0.18 ± 0.12 to 0.52 ± 0.31 (P < 0.001). There was significant reduction in the mean manifest spherical equivalent, refractive cylinder, and mean keratometry readings. The novel minimally invasive surgical method for corneal implantation. It was an effective alternative treatment that could restore corneal integrity and improve vision in patients with corneal perforations. This method appears safe, easy, cost- and time-effective, and reliable.

Agreement between a new fully automatic ocular biometer based on optical low-coherence reflectometry and an optical biometer based on Scheimpflug imaging combined with partial coherence interferometry

BackgroundTo analyze the difference and agreement between measurements obtained by a new fully automatic optical biometer, the SW-9000 μm Plus, based on optical low-coherence reflectometry (OLCR) and a commonly used optical biometer (Pentacam AXL) based on Scheimpflug imaging with partial coherence interferometry (PCI).MethodsThe central corneal thickness (CCT), anterior chamber depth (ACD, from epithelium to anterior lens surface), lens thickness (LT), mean keratometry (Km), corneal astigmatism, corneal diameter (CD), pupil diameter (PD), and axial length (AL) of 74 eyes (from 74 healthy subjects) were measured using the SW-9000 μm Plus and the Pentacam AXL to determine the agreement. Double angle plots were used for astigmatism vector analysis. Bland–Altman and 95% limits of agreement (LoA) were calculated.ResultsStatistically significant differences were detected for all parameters but J0 vector. The Bland–Altman analysis of AL, CCT, ACD, Km, CD, J0 and J45 indicated a high level of agreement between the two devices. Among AL, CCT, ACD, Km, J0, J45, CD, and PD, the 95% LoA ranged from -0.07 to 0.05 mm, -9.67 to 7.34 mm, -0.11 to 0.04 mm, -0.25 to 0.50 D, -0.22 to 0.20 D, -0.15 to 0.20 D, -0.23 to 0.35 mm and 1.55 to 3.77 mm, respectively.ConclusionsThe measurements of AL, CCT, ACD, Km, corneal astigmatism, and CD showed a narrow LoA and may be used interchangeably in healthy subjects between the new OLCR optical biometer and the Scheimpflug/PCI biometer; however, a poor agreement was noted for PD values.

Comparison of ocular biometric measurements and intraocular lens power calculation using different methods in eyes with implantable collamer lenses

This prospective cohort study included 80 healthy candidates for Implantable Collamer Lens (ICL) implantation who underwent biometric assessments with Scheimpflug imaging (the Pentacam-AXL) and swept-source optical coherence tomography (SS-OCT; the IOLMaster-700), both before and 3 months after surgery. The main outcome measures were mean keratometry, anterior chamber depth, axial length, and various intraocular lens (IOL) calculation formulas (Haigis, SRK/T, Hoffer Q, Holladay 1, Barrett Universal 2, and Olsen). The interchangeability of the devices was assessed by generating 95% limits of agreement (95% LoA) and associated Bland-Altman plots. The average age of the participants was 31.5 ± 5.4 years (22–43), with 58 (72.5%) being female. Among the cases analyzed, 11 (13.4%) had incorrect anterior lens surface segmentation using the IOLMaster-700, and 1 case (1.2%) had inappropriate segmentation using the Pentacam-AXL. Postoperative IOL power calculation resulted in readings that were, on average, 0.15 to 0.30 D higher compared to preoperative measurements. The 95% LoAs could differ by up to 0.85 D higher after surgery, indicating weak agreement between pre- and postoperative measurements. There was poor agreement between the IOLMaster-700 and Pentacam-AXL in IOL power calculation for eyes with post-ICL implantation, with a difference of more than 1 D in the 95% LoAs. In conclusion, Scheimpflug imaging was found to be less susceptible than the SS-OCT technique to segmentation errors of the anterior lens surface after ICL implantation. Neither device showed interchangeable results for pre- versus postoperative IOL power calculation. The determination of IOL power by the IOLMaster-700 versus Pentacam-AXL was not interchangeable in eyes with ICL implantation.

Five-year changes in retinal nerve fibre layer thickness in the adult population: a population-based cohort study.

Distinguishing between the pathological thinning of the retinal nerve fibre layer (RNFL) and age-related reduction requires a comprehensive understanding of the longitudinal changes in RNFL thickness within a healthy population. To determine five-year changes in RNFL thickness and associated factors in people aged 45-69 years. This report pertains to the second and third phases of the Shahroud Eye Cohort Study. Participants were recruited by a multi-stage cluster sampling in Shahroud, Iran. Data on demographic details, visual acuity, non-cycloplegic refraction, and slit-lamp biomicroscopy were collected. High-definition optical coherence tomography was employed for retinal imaging. A total of 1,524 eyes from 908 participants were examined. The average RNFL thickness was 92.2 ± 8.5 (95% CI: 91.6 to 92.8) and 93.1 ± 8.7 μm (95% CI: 92.5 to 93.7) in the first and second phases with a five-year mean change of 0.95 ± 4.15 μm (95% CI: 0.70 to 1.20). The RNFL thickness mean changes in the superior, inferior, nasal, and temporal quadrants were 2.51 ± 7.86 (95% CI: 2.01 to 3.02), 2.93 ± 7.39 (95% CI: 2.56 to 3.29), -0.53 ± 6.15 (95% CI: -0.84 to -0.21), and -1.01 ± 4.67 μm (95% CI: -1.27 to -0.75), respectively. The five-year changes in average RNFL thickness were inversely correlated with axial length (β = -0.69, p < 0.001), mean keratometry (β = -0.37, p = 0.017), and baseline RNFL thickness (β = -0.617, p < 0.001). In hyperopic individuals, the increase in average RNFL thickness (β = 0.65, p = 0.012) was significantly greater than in those with emmetropia. Macular volume (β = 1.65, p < 0.001) showed a direct association with five-year changes in average RNFL thickness. Over 5 years, RNFL thickness changes were clinically insignificant in the normal population. The mean RNFL thickness seems to remain stable unless there is ocular disease. However, increased axial length and steeper keratometric readings were linked to RNFL thinning. Those with thicker RNFL measurements were at higher risk of thinning over time.

Quantitative assessment of corneal biomechanical changes in vivo after photorefractive intrastromal corneal cross-linking using optical coherence elastography.

Photorefractive intrastromal corneal cross-linking (PiXL) treatment corrects myopia by enhancing localized central corneal biomechanics. However, the dose-effect relationship between the changes in corneal biomechanics and alterations in corneal curvature resulting from this treatment remain unclear. We therefore developed an acoustic radiation force optical coherence elastography (ARF-OCE) technique to investigate the dose-effect relationship in PiXL. ARF-OCE measurements and corneal topography were performed 3 days before and 1 week after PiXL treatment. Depth-resolved Young's modulus images of the in vivo corneas were obtained based on the phase velocity of the Lamb wave. PiXL treatments with five ultraviolet-A (UVA) energy doses (5.4, 15, 25, 35, and 45 J/cm2) were administered to rabbit corneas in vivo (n=15). The percentage change in Young's modulus (ΔE%) of the cornea increased from 0.26 to 1.71 as the UVA energy dose increased from group I (5.4 J/cm2) to group V (45 J/cm2). Meanwhile, the change in the mean keratometry (ΔKm ) of the cornea increased from 0.40 to 2.10 diopters (D) as the UVA energy dose increased from group I to group IV (35 J/cm2). Furthermore, a statistically significant positive correlation was observed between ΔE% and ΔKm in groups I to IV. With increasing UVA energy dose, the corneal Young's modulus significantly increased. Given the observed correlation, ΔE% holds promise as a new quantitative biomechanical parameter for determining the dose-effect relationship in PiXL treatment. It should be emphasized that there may be an inflection point of ΔE%, at which corneal keratometry ceases to flatten and begins to increase. The ARF-OCE system has demonstrated its efficacy in quantitatively assessing changes in corneal biomechanics in vivo following PiXL treatment. This technique has great potential in facilitating the quantitative determination of the dose-effect relationship in PiXL treatment.

Evaluation of Corneal Biomechanics Using Brillouin Microscopy in Chinese Adults With Myopia.

To evaluate the corneal biomechanical metrics of Chinese adults with myopia and identify relevant factors of Brillouin microscopy. In this cross-sectional study, corneal biomechanics in Chinese adults with myopia were quantified and analyzed using Brillouin microscopy and the Corvis ST (CST) (Oculus Optikgeräte GmbH) and analyzed. Univariate linear regression was used with potential factors including age, sex, spherical equivalent (SE), intraocular pressure (IOP), central corneal thickness (CCT), and mean keratometry (Kmean). The study included 87 eyes of 87 participants (mean age: 24.47 ± 6.27 years). Central, Mean, maximum (Max), minimum (Min), standard deviation, and Max-Min Brillouin modulus (BM) values obtained from Brillouin microscopy exhibited values of 2.826 ± 0.039, 2.827 ± 0.027, 2.864 ± 0.034, 2.790 ± 0.038, 0.108 ± 0.042, and 0.074 ± 0.041 GPa, respectively. No significant correlations were found between BM parameters and age, sex, SE, IOP, or CCT. However, the Mean (β = -0.251, P = .019), Min (β = -0.315, P = .003), and Max-Min (β = 0.229, P = .033) BM values were significantly associated with Kmean. The Central, Mean, Min, and Max BM values negatively correlated with the Tomographic Biomechanical Index measured by CST (Spearman's r = -0.24, -0.35, -0.29, and -0.23, respectively, all P < .05). Brillouin microscopy accurately reflects corneal biomechanical parameters in Chinese adults with myopia, independent of IOP and CCT, with a good correlation with CST. Concurrent evaluation of the corneal curvature is imperative when employing Brillouin microscopy in clinical practice. [J Refract Surg. 2024;40(10):e768-e776.].

Distribution of Ocular Biometry and Intraocular Lens Power in Patients Undergoing Cataract Surgery in an Eye Camp in Northern Pakistan

Purpose: To report ocular biometric data of patients undergoing cataract surgery in an eye camp in a city of Northern area of Pakistan. Design: Cross-sectional descriptive study. Place and Duration of Study: A surgical eye camp was set up in the month of September 2022 for 6 days in a private hospital in Skardu. Methods: A total of 119 patients were selected with a non-probability consecutive sampling technique. Ocular biometry of permanent local residents with significant cataractswas included. Incomplete biometry data and coexisting diseases like corneal opacity, pterygium, and severe dry eye causing errors in biometry were excluded. Keratometry was done with an automated refractor-keratometer. Axial length was calculated with an A-scan (ultrasound contact method) and intraocular lens (IOL) power was calculated. Results: A total of 119 patients were selected for biometry among 3908 individuals visiting an eye camp. The mean axial length was 22.13 ± 1.25 SD mm. The mean keratometry readings (K1) was 43.28 ± 1.83 Diopter and (K2) 44.26 ± 1.67 D. The mean intraocular lens (IOL) power was 24.78 ± 3.43 D. The mean K readings were more in males as compared to females (p-value &lt;0.005). There was no significant difference in axial length and IOL power among genders. Conclusion: This study gives normative data on ocular biometric parameters of patients undergoing cataract surgery at high altitudes in Skardu, Pakistan. These biometric values can be used as reference values in the local population

Comparison of measurements and calculated lens power using three biometers: a Scheimpflug tomographer with partial coherence interferometry and two swept source optical coherence tomographers

PurposeTo compare the biometric measurements obtained from the Pentacam AXL Wave, IOLMaster 700, and ANTERION and calculate the recommended intraocular lens power using the Barrett Formulae.MethodsThis was a retrospective cross-sectional study of patients who underwent biometry using the Pentacam AXL Wave, IOLMaster 700, and ANTERION. Flat keratometry (K1), steep keratometry (K2), anterior chamber depth (ACD), and axial length (AL) from each device were measured and compared. These parameters were used to calculate the recommended IOL powers using the Barrett formula.ResultsThe study included 252 eyes of 153 patients. The IOLMaster had the highest acquisition rate among the two biometers. The Pentacam obtained the shortest mean AL, the IOLMaster measured the highest mean keratometry values, and the ANTERION measured the highest mean ACD. In terms of pairwise comparisons, keratometry and axial length were not significantly different between the Pentacam-IOLMaster and ANTERION-IOLMaster groups, while the rest of the pairwise comparisons were statistically significant. In nontoric and toric eyes, 35–45% of patients recommended the same sphere of IOL power. In another 30–40%, the Pentacam and ANTERION recommended an IOL power one step greater than that of the IOLMaster-derived data. 50% of the study population recommended the same toric-cylinder IOL power.ConclusionsThe Pentacam AXL Wave, IOLMaster 700, and ANTERION can reliably provide data for IOL power calculations; however, these data are not interchangeable. In nontoric and toric eyes, 35–45% of cases recommended the same sphere IOL power, and in another 30–40%, the Pentacam and ANTERION recommended one-step higher IOL power than the IOLMaster-derived data. In targeting emmetropia, selecting the first plus IOL power is advisable when using the Pentacam and ANTERION to approximate the IOL power calculations recommended by the IOLMaster 700.

Corneal Cross-Linking for Pediatric Keratoconus.

The aim of this study was to evaluate corneal cross-linking (CXL) for keratoconus in pediatric patients. After keratometric qualification according to the Amsler-Krumeich system, corneal collagen cross-linking was performed using ultraviolet light and photosensitizing riboflavin drops in 111 eyes of 74 children with a mean age of 15 ± 1.67 years. None of the children studied wore contact lenses before the procedure. Visual acuity, intraocular pressure, keratometry, and pachymetry parameters were analyzed before and after corneal cross-linking. Visual acuity was 0.64 ± 0.31 and 0.66 ± 0.29 before CXL and at the end of the follow-up, respectively; the difference was not statistically significant. The mean intraocular pressure before CXL was 14.48 ± 3.13 mmHg, while the mean value at the end of the follow-up was 14.23 ± 3.03 mmHg; no statistically significant difference was found. Pre- and post-CXL astigmatism was 3.98 ± 2.34 Dcyl and 3.63 ± 1.86 Dcyl, respectively; the difference was not statistically significant. The mean keratometry before CXL was 47.99 ± 3.96 D; the mean post-follow-up value was 47.74 ± 3.63 D. The mean corneal thickness (pachymetry) at the apex of the keratoconus-the thinnest zone of the cornea-before CXL was 492.16 ± 38.75 µm, while the mean value at the end of the follow-up was 479.99 ± 39.71 µm; the difference was statistically significant. Corneal cross-linking is an effective method for preventing keratoconus progression in children. However, further and detailed ophthalmic follow-up of patients who underwent CXL before the age of 18 is highly advisable.

Change of ectropion surgery on astigmatic vector and ocular biometry

Aim: To evaluate corneal astigmatism change and intraocular lens (IOL) power values following ectropion surgery. Materials and Methods: This comparative prospective research included patients with involutional ectropion who were divided using the snap-back test. The severity of ectropion increased progressively to reach the highest levels in Group 4. Patients underwent lateral tarsal strip procedures, and preoperative and 3-month postoperative biometry measurements were performed. Results: While the mean flattest keratometry (K1), steepest keratometry (K2), and mean keratometry (Km) values exhibited nonsignificant increases at 3 months after surgery in Groups 1 and 2 (p&amp;gt;0.05 for all), the mean values of K1, K2, and Km were increased with statistical significance in Groups 3 and 4 at 3 months postoperatively (p&amp;lt;0.05 for all). Conclusion: According to the snap-back test, ectropion in advanced stages will affect topographic values and IOL power calculations. If surgeons are going to perform cataract or refractive surgery after ectropion repair, they may consider changing the lens power selection accordingly.

Distribution and associated factors of keratometry and corneal astigmatism in an elderly population

To determine the distribution of keratometry and corneal astigmatism (CA) and their association with demographic factors, systemic parameters, anthropometric measures, ocular biometric indices, and refractive errors in people aged 60 years and above. In this cross-sectional study, 160 clusters were randomly selected from Tehran city (Iran) using the multi-stage cluster sampling method. All participants underwent optometric examinations including testing uncorrected and best-corrected distance visual acuity, non-cycloplegic autorefraction, and subjective refraction. Pentacam imaging for all participants was carried out using Pentacam AXL. Keratometry and CA were reported based on Pentacam’s data. The average, standard deviation (SD) and 95% confidence interval (CI) of flat keratometry (Kf), steep keratometry (Ks), mean keratometry (mean K), and CA were 44.02 ± 1.58 D (95% CI 43.94–44.1), 44.86 ± 1.67 D (95% CI 44.78–44.94), 44.44 ± 1.58 D (95% CI 44.36–44.52), and 0.84 ± 0.74 D (95% CI 0.81–0.87), respectively. The 95% and 99% percentiles of mean K were 47.1 and 48.6 D, respectively. According to the multiple generalized estimating equation model, the mean K was significantly higher in males, in myopes, and in those with higher systolic blood pressure. Moreover, the mean K was inversely related to the axial length, height, anterior chamber depth (ACD), corneal diameter, and central corneal thickness (CCT). The prevalence of various types of CA based on a cut-off > 0.50 D was as follows; with-the-rule: 32.5% (95% CI 30.6–34.4), against-the-rule: 18.2% (95% CI 16.7–19.7), and oblique: 10.0% (95% CI 9.1–11.0). The present study investigated the normal distribution of keratometry and CA in individuals ≥ 60 years, and results can be used in clinical matters, especially in intraocular lens power calculation. Sex, systolic blood pressure, height, and some biometric components such as ACD, corneal diameter, and CCT were significantly related to keratometry and should be considered.

Comparison of ocular biometric parameters between two swept-source optical coherence tomography devices and Scheimpflug tomography in patients with cataract.

To assess and compare the variations and agreements across different ocular biometric parameters using swept-source optical coherence tomography (SS-OCT) and Scheimpflug tomography in patients diagnosed with cataract. This prospective case series was conducted at Tianjin Medical University Eye Hospital. In total, 212 eyes from 212 patients scheduled for phacoemulsification were included. Eyes were evaluated preoperatively using two SS-OCT devices (IOLMaster700 and CASIA2) and Scheimpflug tomography (Pentacam). Central corneal thickness (CCT), anterior chamber depth (ACD), aqueous depth (AQD), white-to-white distance (WTW), flat simulated keratometry (Kf), steep simulated keratometry (Ks), mean keratometry (Km), and total corneal keratometry (TKm) were measured. Intraclass correlation coefficient (ICC), 95% confidence intervals (CI) and limits of agreement (LoA) widths were conducted to assess differences and correlations between devices. All parameters, except for Ks, were significantly different. Pairwise comparison revealed no significant differences between keratometry obtained by IOLMaster 700 and Pentacam. LoA widths of all paired comparisons for Ks were >0.80 D. Except for WTW between IOLMaster 700 and CASIA2 and between CASIA2 and Pentacam, other Pearson's coefficients between devices showed a strong correlation (all r>0.95). The ICC of WTW (ICC=0.438, 95%CI 0.167-0.625) showed poor reliability. The reliability of CCT, ACD, and AQD was excellent (all ICC>0.95), whereas that of TKm was good (ICC=0.827, 95%CI 0.221-0.939). A significant linear correlation was also observed among devices. The ocular parameters derived from the use of IOLMaster700, CASIA2, and Pentacam exhibit significant discrepancies; as such, measurements from these devices should not be deemed as interchangeable.

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

BackgroundAssessing 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.MethodsA 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).ResultsCycloplegia 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.ConclusionsRefractive 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.

Refractive Outcomes After Scleral Fixation of the Carlevale Intraocular Lens.

To assess the refractive predictability of the Carlevale sutureless scleral fixation intraocular lens (IOL) (Sole-ko IOL Division) power calculation. This retrospective, non-comparative, interventional case series included patients without a capsular support having undergone sutureless scleral fixation IOL implantation in two French hospitals between October 2019 and April 2022. IOL calculation was performed with the Barrett Universal II, Hoffer Q, Holladay 1, and SRK/T formulas with constant optimization to achieve a mean arithmetic prediction error equal to zero. The main outcomes were prediction error (PE) and its standard deviation (SD-PE), the median absolute error (MedAE), the mean absolute error (MAE), and the percentage of eyes with PE within ±0.50, ±1.00 and ±2.00 diopters (D) 6 months after surgery. Thirty eyes of 30 patients were included in the study. The mean age was 66.6 years, the mean axial length was 24.31 mm, and the mean keratometry was 43.07 D. SDPE ranged from 0.73 to 0.87 D depending on the formula. MedAE ranged from 0.38 to 0.61 D, and MAE from 0.52 to 0.68 D. Between 46.7% and 56.7% of eyes were within ±0.50 D, 76.7% and 90.0% were within ±1.00 D, and 96.7% were within ±2.00 D of target equivalent. No statistically significant difference was observed between the four formulas for any outcomes. This study confirmed that the design of the Carlevale sutureless scleral fixation IOL provides satisfactory refractive results. [J Refract Surg. 2024;40(8):e527-e532.].

Risk Factors for Postoperative Refractive Error in New-Generation Intraocular Lens Calculation Formulas.

We examined differences in the accuracy of three intraocular lens (IOL) calculation formulas: the traditional Sanders-Retzlaff-Kraff/Theoretical (SRK/T) formula; the Barrett Universal II (BU II) formula, which is a new-generation IOL calculation formula; and the postoperative spherical equivalent prediction using artificial intelligence and linear algorithms developed by Debellemanière, Gatinel, and Saad formula (PEARL-DGS [PEARL]) formula, and evaluated factors that cause postoperative refractive error (PE). The study included 205 patients (205 eyes) with a mean age of 75.2 ± 8.7 years who underwent cataract surgery at our institution from December 2018 to October 2023. The PE of the three IOL calculation formulas was calculated and compared. Multivariate logistic regression analysis was performed with a PE higher than ±0.50 D as the dependent variable, and age, sex, axial length (AL), mean keratometry (mean K), anterior chamber depth (ACD), lens thickness (LT), and white-to-white (WTW) as independent variables. The mean PE (ME)±standard deviation of the SRK/T, BU II, and PEARL formulas was 0.11 ± 0.52, 0.11 ± 0.50, and 0.21 ± 0.50 D, respectively. MEs of the three IOL calculation formulas were significantly different from 0 (p < 0.01). The median absolute error (MedAE) was not significantly different among the three IOL calculation formulas (p = 0.83). The percentage of PE within ±0.50 D was not significantly different among the three IOL calculation formulas (p = 0.13). Multivariate logistic regression analysis showed that the significantly associated factors with PE higher than ±0.50 D were AL, ACD, and LT for the SRK/T formula, sex and LT for the BU II formula, and LT for the PEARL formula (all p < 0.05). In the BU II and PEARL formulas, AL was excluded as a factor affecting PE, indicating that LT was a risk factor.

Investigating the topographic effect of epithelium in myopic eyes with subtle topographic preoperative abnormalities.

To explore the topographic effect of the epithelium in keratoconus suspected (KCS) and in normal Placido classified corneas. Rothschild Foundation, Paris, France. Prospective interventional case series. Anterior corneal specular Placido topography using OPD-Scan II was performed in 97 eyes of 67 patients undergoing photorefractive keratectomy for myopia, before and after epithelium removal. The differences in axial keratometry, asphericity, and astigmatism were computed. After epithelial peeling, some Placido-normal classified corneas became KCS. Therefore, we have subdivided this group into 2 groups: one of normal classified corneas which stayed normal after epithelium removal (Group NN) and another of corneas that became KCS classified (Group NK). The mean difference in axial mean keratometry in the third central millimeter rings was +0.50 ± 0.24 diopters (D), 0.69 ± 0.31 D, and 0.49 ± 0.35 D and the mean difference in the magnitude of epithelial-induced astigmatism in the first central millimeter ring was 0.37 D × 89 degrees (positive cylinder), 0.54 D 86 degrees, and 0.52 D 86 degrees, respectively, in Group NN, NK, and KK (KCS corneas that stayed KCS). These differences were significant ( P < .0001). Preoperative keratometry was the only predictive factor differentiating Group NN from NK ( P < .001). The epithelial layer tended to reduce the magnitude of the Bowman layer's astigmatism, prolateness, and keratometry, more importantly in Group NK. In the KK group, we found a similar trend as in normal eyes (Group NN). The epithelium would be able to mask Bowman layer's irregularities until a certain degree of severity.

Parameters influencing the effectiveness of femtosecond laser-assisted capsulotomy in white cataract surgery

PurposeTo explore the parameters that may influence the effectiveness of femtosecond laser-assisted capsulotomy in white cataract surgery and its cutoff points. DesignA retrospective case series. MethodsThis retrospective case series study enrolled patients with white cataract who had undergone surgery at Changsha Aier Eye Hospital from July 2018 to January 2020. All patients underwent femtosecond laser-assisted capsulotomy using a contact femtosecond laser device (LenSx, Alcon Laboratories, USA). The sex, age, corrected distance visual acuity (CDVA), intraocular pressure (IOP), axial length (AL), lens thickness (LT), anterior chamber depth (ACD) and mean keratometry (Km) were recorded. All eyes were divided into successful capsulotomy group and unsuccessful capsulotomy group according to the capsulotomy integrity. Both groups were compared and two-sample t-test was used in order to find the optimal cutoff points of the parameters. Results60 eyes of 59 patients were included in the study. A successful capsulotomy was achieved in 36 eyes (60 %), while unsuccessful capsulotomy occurred in 24 eyes (40 %). Although no significant differences were observed in sex (P = 0.704), AL (P = 0.598) and Km (P = 0.873) between both groups, LT (P < 0.01), ACD (P = 0.014) and age (P < 0.01) were significantly different; a LT of 5.21 mm was found to be the optimal cutoff point. ConclusionsFemtosecond laser-assisted capsulotomy in white cataract is safe and effective. LT, ACD and age may influence the effectiveness of femtosecond laser-assisted capsulotomy in patients with white cataracts. LT is the main associated parameter and 5.21 mm is the optimal cutoff point for LT.

Outcomes of Donor Corneas of Different Thicknesses From Endothelial Keratoplasty in Deep Anterior Lamellar Keratoplasty for Keratoconus.

To evaluate the outcomes of divided residual donor corneas obtained from endothelial keratoplasty in keratoconus with deep anterior lamellar keratoplasty (DALK). In this retrospective, comparative, clinical study, 103 keratoconic eyes that underwent DALK were enrolled; 67 eyes received thin grafts from Descemet stripping automated endothelial keratoplasty, and 36 received thick grafts from Descemet membrane endothelial keratoplasty. Baseline and postoperative central corneal thickness (CCT), inferior corneal thickness, uncorrected distance visual acuity, corrected distance visual acuity, corneal astigmatism, mean keratometry, biomechanical properties, and complication rates were measured. Six months after transplantation, the group receiving thin grafts had a CCT of only 455.1 ± 43.0 μm, whereas that of the group receiving thick grafts was 546.7 ± 44.2 μm. Both CCT and inferior corneal thickness in the thin group were significantly lower than those in the thick group (measured with Pentacam at 36 months, P < 0.001) and remained throughout the 5-year follow-up period. Both procedures had comparable postoperative logarithm of the minimum angle of resolution UDVAs, logarithm of the minimum angle of resolution corrected distance visual acuity, astigmatism, and mean keratometry values (36 months; P = 0.335, 0.286, 0.680, and 0.365, respectively). Corneal biomechanical analysis revealed that the thin group had a significantly higher stiffness parameter at the first applanation than the thick group at the 2-year follow-up (P = 0.036) while other parameters were equivalent. The outcomes of keratoplasty with donor tissue are comparable regardless of the thickness of the graft, which suggests that transplantation with either type of the split corneal procedure for DALK in patients with keratoconus is feasible.

A Technique of Multiple Corneal Allogeneic Ring Segments Prepared From a Single Corneal Graft: A Case Series.

To describe a novel technique for preparing multiple corneal allogeneic ring segments (CAIRS) from a single corneal graft using femtosecond laser technology. This is a case series of 10 eyes from 10 patients with keratoconus who underwent FS-assisted CAIRS implantation using corneas from 4 donors at the Hospital Foundation Adolphe de Rothschild-Noémie de Rothschild institute. A preoperative and postoperative examination was performed at 1 day, 1 week, and 1 month. Anterior segment OCT and corneal tomography with aberrometric and pachymetric analyses were performed at each visit. Visual, refractive, and topographic parameters were extracted. The thickness and width of implanted CAIRS were analyzed. Patients were classified according to keratoconus severity: group A (maximal keratometry Kmax <75D) and group B (Kmax >75D). At 1 month postoperatively, both groups A and B showed a significant decrease in mean keratometry by 4.78 ± 1.57D and 12.87 ± 4.62D, respectively. Total and higher order aberrations decreased by 5.66 ± 4.55 and 0.65 ± 1.54 in group A and by 9.45 ± 9.15 and 0.49 ± 1.39 in group B, respectively. The corrected distance visual acuity improved by 4.8 ± 1.7 lines in group A. Visual improvement was not significant in group B. One eye in group B exhibited acute rejection and required explantation. FS-assisted multiple CAIRS implantation using a single corneal graft maximizes the utilization of viable corneal tissue. CAIRS implantation is an effective and biocompatible therapeutic alternative, particularly in cases of moderate to advanced keratoconus with Kmax <75D.

Refractive errors in patients with Bardet Biedl syndrome

ABSTRACT Purpose Bardet-Biedl Syndrome (BBS) is a rare autosomal recessive ciliopathy. Within corneal development, primary cilia serve a critical role. We sought to investigate the association of BBS with corneal astigmatism among a cohort of patients with BBS. Methods This was a cross-sectional, retrospective study performed at a pediatric ophthalmology department of a tertiary hospital. The study enrolled 45 patients with genetically confirmed Bardet-Biedl syndrome, encompassing a total of 90 eyes observed from February 2011 to August 2021. Spherical and cylindrical refractive errors and keratometry outcome measures, including diopter (D) values at the flattest and steepest axes, were recorded. Corneal astigmatism of greater than 3D is considered extreme corneal astigmatism based on previously published data. Results Among 45 patients (M:26; F:19), the mean age was 16.4 ± 8.2 years, and the mean best-corrected visual acuity was 20/60. The most common molecular diagnosis was BBS1, seen in 24 of 45 (53.3%). Among all the patients, the mean spherical refractive error was −2.9 ± 3.8D. The mean cylindrical refractive error was 2.6 ± 1.5D. The mean keratometry values at the flattest axis was 43.5 ± 5.3D (39.4–75.0) and at the steepest axis was 47.2 ± 7.3D(41.5–84.0). Among all the patients with BBS, the mean corneal astigmatism was 3.7 ± 1.0D(0.5–7.1), which is considered extreme. Conclusion A cohort of individuals with BBS demonstrated high corneal astigmatism. These results suggest an association between corneal astigmatism and primary ciliary dysfunction and may assist in clinical management and future therapeutic targets among BBS and other corneal disorders.