Lenstar LS Research Articles

Predictive Accuracy of the Hill-RBF 2.0 Formula in Pediatric Eyes: Comparison of 5 Intraocular Lens Formulas.

To compare the predictive accuracy of the Hill-Radial Basis Function (Hill-RBF) 2.0 formula with the Barrett Universal II, Hoffer Q, SRK/T, and Holladay 1 formulas in pediatric eyes. In this observational study, 99 eyes of 70 children 4 to 18 years old with clinically significant congenital or developmental cataracts attending the pediatric ophthalmology clinic in Guru Nanak Eye Centre were included. Optical biometry was performed in all patients with the Lenstar LS-900 (Haag-Streit). Intraocular lens (IOL) power predicted by the Hill-RBF formula was selected. Mean absolute prediction error (MAE) at 8 weeks of follow-up was calculated for the Hill-RBF, Barrett Universal II, Hoffer Q, SRK/T, and Holladay 1 IOL power formulas. Percentages of eyes having residual refraction within ±0.50, ±0.50 to ±1.00, and greater than ±1.00 diopters (D) of target refraction were calculated. The MAEs were 1.08 ± 1.00 D for the Hill-RBF, 1.24 ± 1.20 D for the Barrett Universal II, 1.25 ± 1.06 D for the Hoffer Q, 1.25 ± 1.10 D for the SRK/T, and 1.28 ± 1.01 D for the Holladay 1 formulas. The Hill-RBF formula had the lowest MAE, which was significantly lower than the Holladay 1 and Hoffer Q formulas. However, the difference in MAE between the Hill-RBF and the SRK/T and Barrett Universal II formulas was not statistically significant (P > .05). The Hill-RBF group had the maximum percentage of eyes with residual error within ±0.50 D of the target refraction. The overall evidence from the studies indicates that the Hill-RBF method that uses artificial intelligence and works independent of specific anatomical features is non-inferior to the Barrett Universal II, Hoffer Q, SRK/T, and Holladay 1 formulas in pediatric eyes. [J Pediatr Ophthalmol Strabismus. 2023;60(4):282-287.].

Distribution of Pupil Size and Associated Factors: Results from the Population-Based Gutenberg Health Study.

Results 18,335 eyes of 9,559 participants aged 40 to 80 years were included in the analysis. Median pupil diameter was 4.19 mm in right eyes and 4.12 mm in left eyes. A smaller pupil was associated with older age, hyperopic refractive error, previous cataract surgery, diabetes, obesity, and ACE inhibitor intake, whereas wider pupil was associated with female gender, arterial hypertension, intake of tricyclic antidepressants, and intake of SNRI and tetracyclic antidepressants. Socioeconomic status and smoking were not associated with pupil size. Conclusion Individuals of older age, after cataract surgery, under therapy with ACE inhibitors and with diabetes have a smaller pupil. This should be taken into account when planning nonmydriatic fundus photography-based screening programs, for instance, for diabetic retinopathy.

Repeatability and comparability of a new swept-source optical coherence tomographer in optical biometry

PurposeTo evaluate the reproducibility in the measurement of ocular biometric parameters using a new swept-source optical coherence tomographer and its comparability with an optical low coherence reflectometry biometer. DesignAn observational, descriptive, cross-sectional study. Methods45 right eyes of 45 patients diagnosed with cataract were included. Three successive biometric measurements with Anterion and one with Lenstar LS900 were performed on each patient. The following variables were collected: axial length (AXL), anterior chamber depth (ACD), flat K (K1), steep K (K2), central corneal thickness (CCT), lens thickness (LT) and white-to-white distance (WTW). The intrasubject standard deviation (Sw) and the coefficient of Pearson “R” were calculated in order to assess the repeatability. The intraclass correlation coefficient (ICC) and the concordance correlation coefficient (CCC) were obtained to evaluate the comparability between devices. A Bland-Altman plot was performed for each variable. ResultsThe coefficient of Pearson was excellent and statistically significant in the evaluation of the repeatability in all the variables. The highest values were 0.987 (AXL), 0.983 (CCT) and 0.942 (ACD). There were no statically significant differences between repeated measurements with Anterion in all the parameters. The ICC and CCC were excellent in the evaluation of AXL, CCT and ACD, and were also good in regard to K1, K2, LT and WTW. ConclusionsPerforming biometry with the SS-OCT Anterion is a reliable and reproducible procedure, and it is comparable with the Lenstar LS900.

Comparative study for evaluation of the horizontal white-to-white corneal diameter using the optic low-coherent reflectometer and the Scheimpflug topography in normal Egyptian population

Purpose: Comparison of the horizontal white-to-white corneal diameter measured by Lenstar LS 900® (Haag‑Streit AG, Koeniz, Switzerland) and TOMEY TMS-5® (topographic modeling system, version 5) to assess the agreement between them. Setting: El-Agouza police hospital, Egypt. Materials and methods: Comparative prospective cross-sectional clinical study in which measurements of the horizontal WTW corneal diameter were obtained by LENSTAR LS900 and TOMEY TMS-5. Results: The study included 219 eyes of 115 randomly chosen normal Egyptian subjects of both sex (68 males and 47 females). The WTW diameters measured by LENSTAR LS900 and TOMEY TMS-5 ranged from 10.88 to 13.15 mm and 10.69 to 12.94 mm respectively. Lenstar LS 900 gives slightly higher values for WTW diameter than TOMEY TMS-5. Pearson coefficient of correlation (r) revealed a strong statistically significant level of correlation between WTW values measured by both devices (r = 0.87 with p<0.01). Paired samples t-test showed a small mean inter-device difference with high statistical significance (0.29 mm and p<0.01). The Bland-Altman limits of agreement for WTW values measured by them showed a LoA extending from -0.1 to 0.68 mm. Cf the patient.

Predictors of Femtosecond Laser–Assisted Arcuate Keratotomy Efficacy for Astigmatism Correction in Cataract Surgery

To evaluate the predictors related to the efficacy of epithelium- and Bowman membrane-penetrating femtosecond laser-assisted arcuate keratotomy (FSAK) in the treatment of preoperative astigmatism in patients with cataracts and to clarify the predictive role of the incision-to-limbus distance. This retrospective study included patients who underwent femtosecond laser-assisted cataract surgery combined with FSAK using the LenSX platform (Alcon Laboratories, Inc) at Beijing Aier-Intech Eye Hospital from March 2017 to December 2021. The Lenstar LS900 (Haag-Streit, Inc) was used to measure the horizontal corneal diameter, and ImageJ software (National Institutes of Health) was used to measure the vertical corneal diameter and incision-to-limbus distance. Finally, the measured values were converted. Changes in corneal astigmatism before and 3 months after surgery were analyzed using Alpins vector analysis. Correlation analysis and regression analysis were used to evaluate the factors associated with surgically induced astigmatism (SIA) in preoperative ocular biometric parameters. The study included 94 eyes of 94 patients. The mean target induced astigmatism was 1.36 ± 0.44 diopters (D), SIA was 0.82 ± 0.43 D, and mean difference vector was 0.70 ± 0.40 D. Pearson correlation analysis and univariate regression analysis showed that preoperative corneal astigmatism, arcuate keratotomy arc length, incision-to-limbus distance, and astigmatism type were significant predictors of SIA. Multiple variable regression analysis included parameters such as age, arcuate keratotomy arc length, and incision-to-limbus distance and established a multiple regression model of SIA (all P < .01). The incision-to-limbus distance was a significant independent predictor of SIA, and inclusion of this parameter may further improve the accuracy of the nomogram. [J Refract Surg. 2022;38(8):480-486.].

Comparison of central corneal thickness measurements with different non-contact devices in healthy children

PurposeTo investigate the agreement of the Combined Scheimpflug-Placido Disk System (Sirius), specular microscopy (Tomey EM-4000), non-contact tono-pachymetry (Canon TX-20P), and optical low-coherence reflectometry (Lenstar LS 900) devices in the measurement of central corneal thickness (CCT) in healthy children. MethodEighty-three eyes from 83 healthy children were included in the study. The mean age of the children was 11.1 ± 2.8 (range, 7–17) years. CCT was measured using the Sirius topography, Tomey specular microscopy, Canon TX-20P, and Lenstar LS 900 devices. To examine the agreement among these devices, 95% limits of agreement (LoA) and intraclass correlation coefficients (ICC) were determined. ResultsThe mean CCT values obtained using the Sirius topography, Tomey SM, Canon TX-20 P, and Lenstar 900 devices were 555.9 ± 37 µm, 553.5 ± 39 µm, 569.3 ± 33 µm, and 559.7 ± 38 µm, respectively. With the ICC method, the agreement rates were determined as 0.875 between Canon TX-20P and Sirius topography, 0.903 between Canon TX-20P and Lenstar LS 900, 0.842 between Canon TX-20P and Tomey EM-4000, 0.979 between Sirius Topography and Lenstar LS 900, 0.978 between Sirius topography and Tomey EM-4000, and 0.969 between Lenstar LS 900 and Tomey EM-4000. ConclusionThe devices with the closest results to each other were the Sirius and Tomey EM-4000 devices, with a statistically strong agreement. There was also a strong agreement between Sirius and Lenstar LS 900, although there was a 3.7-unit difference between them. Nevertheless, despite the strong agreements among these devices, because their CCT values varied statistically significantly, these devices should not be used interchangeably in clinical practice.

Repetibilidad y comparabilidad de un nuevo tomógrafo con tecnología SS-OCT en biometría óptica

PurposeTo evaluate the reproducibility in the measurement of ocular biometric parameters using a new swept-source optical coherence tomographer and its comparability with an optical low coherence reflectometry biometer. DesignAn observational, descriptive, cross-sectional study. Methods45 right eyes of 45 patients diagnosed with cataract were included. Three successive biometric measurements with Anterion and one with Lenstar LS900 were performed on each patient. The following variables were collected: axial length (AXL), anterior chamber depth (ACD), flat K (K1), steep K (K2), central corneal thickness (CCT), lens thickness (LT) and white-to-white distance (WTW). The intrasubject standard deviation (Sw) and the coefficient of Pearson «R» were calculated in order to assess the repeatability. The intraclass correlation coefficient (ICC) and the concordance correlation coefficient (CCC) were obtained to evaluate the comparability between devices. A Bland–Altman plot was performed for each variable. ResultsThe coefficient of Pearson was excellent and statistically significant in the evaluation of the repeatability in all the variables. The highest values were 0.987 (AXL), 0.983 (CCT) and 0.942 (ACD). There were no statically significant differences between repeated measurements with Anterion in all the parameters. The ICC and CCC were excellent in the evaluation of AXL, CCT and ACD, and were also good in regard to K1, K2, LT and WTW. ConclusionsPerforming biometry with the SS-OCT Anterion is a reliable and reproducible procedure, and it is comparable with the Lenstar LS900.

The binocular intraocular lens power difference in eyes with different axial lengths.

To investigate the binocular intraocular lens (IOL) power difference in eyes with short, normal, and long axial lengths (AL) using Lenstar LS 900 optical biometry. A total of 716 (1432 eyes) participants were included. The groups were categorized into short (group A: AL<22 mm), normal (group B: 22 mm≤AL≤25 mm), and long AL groups (group C: AL>25 mm). The central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), AL, anterior corneal keratometry, white-to-white (WTW), pupil diameter (PD), as well as IOL power calculated using embedded Barrett formula were assessed. Bland-Altman plots were used to test the agreement of the binocular parameters. In group A, the CCT of the right eye was significantly thinner than that of the left eye (P=0.044) with a difference of -2±8 µm [95% limits of agreement (LoA), -17.8 to 13.2 µm]. For group B, the PD and IOL power in the right eye were significantly lower than those of the left eye (P=0.001, <0.001) with a difference of -0.05±0.32 mm (95%LoA, -0.68 to 0.58 mm) and -0.18±1.01 D (95%LoA, -2.2 to 1.8 D). The AL of right eye was longer than that of the left eye (P=0.002) with a difference of 0.04±0.25 mm (95%LoA, -0.45 to 0.52 mm). No significant difference was observed for all the binocular parameters in group C. The percentage of participants with binocular IOL power difference within ±0.5 D were 62% (31/50), 68.3% (339/496), and 38.8% (66/170) in groups A, B, and C, respectively. The binocular parameters related to IOL power are in good agreement, but the binocular IOL power difference of more than half of participants with long AL is more than 0.50 D.

Comparison of keratometry versions in patients with corneal astigmatism

Purpose: to compare the corneal power at main meridians, the magnitude and the axis of corneal astigmatism and the reproducibility of measurements taken three times with different types of biometers.Material and methods. 22 subjects (24 eyes) with regular corneal astigmatism 1.89–8.02 D were given three biometry tests using IOL Master 500, Lenstar LS 900, IOL Master 700, Pentacam and Galilei G6.Results. The data were divided into groups depending on the principle of mathematical modeling of the corneal surface: group I involved the material processed by IOL Master 500, Lenstar LS 900, IOL Master 700; group II contained maps of the anterior corneal surface; and group III, those of the posterior surface. In group I, Lenstar showed the highest values of keratometry. In group II, the values of K1 , Kave in the 6 mm area were lower than in the pupil diameter area and than any values of K in the 4 mm area; the lowest values of K in this area were obtained on the Pentacam SimK. In group III, in the pupil diameter area (4.0–4.5 mm), all K values obtained with diverse equipment were different whilst in the 6 mm area the values differed only in the flat meridian. Astigmatism within groups I, III showed no difference while in group II the SimK data were different. The astigmatism axes obtained on IOLMaster 500 differed from the respective data provided by other devices. The devices of group I, 6 mm area, were the most stable.Conclusions. The highest values of keratometry are obtained when only the anterior surface of the cornea is taken into account, the lowest values are characteristic of the posterior surface. The stability of the parameter registered grew with the increase of the measured zone diameters. The biometers of group 1 showed the highest values of astigmatism with the maximum repeatability of the measurements

ANALYSIS OF CORNEAL ANTEROPOSTERIOR RATIO OF OPTICAL POWER USING OCT.

The aim of the study was to analyse the values of the anteroposterior corneal optical power ratio (AP ratio), to compare the resulting values with those of theoretical models of the eye, and to define the effect of using an individual ratio value on the approximation of the total corneal power. A total of 406 eyes were included. Each patient underwent an OCT (RTVue XR) examination, according to which the AP ratio of the cornea was determined, as well as the biometric parameters of the eye (Lenstar LS900). The correlation between the biometric parameters of the eye and the individual AP ratio values was evaluated using Pearsons correlation coefficient. In the analysis, the AP ratio results were compared with selected schematic models of the eye. Using Gaussian equations, a theoretical calculation of the total corneal optical power (KG) was performed, by fitting the AP ratio value and comparing it with the actually measured total corneal power (TCP). The mean value of the individually determined AP ratio was 1.17 ±0.02. The most frequently represented interval (33.74 %) was 1.17 to 1.18 AP ratio values, with the vast majority of eyes (79.56 %) in the range of 1.15 to 1.20. Individual values of total corneal optical power were statistically significantly different (p &lt; 0.05) from the theoretical values of TCP (except in the Liu-Brennan eye model, where p = 0.06). The lowest mean difference of values was found for the Navarro schematic model. The dependence of the measured AP ratio values and biometric parameters reached a moderate negative correlation (r = -0.50 for p &lt; 0.05) with the parameter corneal posterior surface curvature (Rp), as well as a weak negative correlation with limbal diameter WtW (r = -0.26 for p &lt; 0.05) and a weak positive correlation with central corneal thickness CCT (r = 0.17 for p &lt; 0.05). The assumption of a constant value of the AP ratio according to the selected schematic models of the eye is statistically significantly different from the actual measured values and was defined to have only a negative weak correlation with the size of the limbus diameter. Using the resulting average value of the determined AP ratio (1.17 ±0.02), a lower difference between real and calculated total corneal optical power was achieved.

Agreement analysis of Lenstar with other four techniques of biometry before cataract surgery.

To test whether some biometry measurements provided by the Lenstar LS900 compared well with the AL-Scan, Pentacam rotating Scheimpflug camera, Ultrasound Biomicroscopy (UBM) and Tomey EM-3000. Two hundred and one patients having routine cataract surgery had standard preoperative assessment. In this clinical study, the axis length (AL) and lens thickness (LT) were taken by Lenstar LS900 and AL-Scan; anterior chamber depth (ACD) was taken by Lenstar LS900, A-Scan, Pentacam and UBM; central corneal thickness (CCT) was taken by Lenstar LS900, Pentacam and Tomey EM-3000. The results were compared using a Wilcoxon-Mann-Whitney U test and Pearson correlation calculations. Agreement was assessed through intraclass correlation coefficients and Bland-Altman plots. The highest correlation was found between Lenstar and AL-Scan for AL (r = 0.975; P < 0.001). For LT measurements, the correlation between these two devices was also good (r = 0.699; P < 0.001). Excellent correlations were showed between Lenstar and Pentacam or UBM for ACD (r = 0.948, 0.704, respectively, both P < 0.001), but not between Lenstar and AL-Scan (r = 0.453, P < 0.001). The correlations of CCT between Lenstar and Pentacam or Tomey EM-3000 were both excellent (r = 0.817, 0.882, respectively, both P < 0.001). In phakic eyes of cataract patients, measurements of AL, LT, ACD and CCT from Lenstar LS900 yielded results that correlated very well with other clinical instruments.

Interocular Axial Length Difference and Treatment Outcomes of Anisometropic Amblyopia.

PurposeTo evaluate the effect of interocular axial length (AL) difference on outcomes of treatment for anisometropic amblyopia in comparison with normal participants.Methods In this historical cohort study, 83 patients with anisometropic amblyopia were divided into two age groups, 70 children (mean, 7.86 1.56 and range, 5–15 years) and 13 adults (mean, 26.46 10.87 and range, 16–45 years). The control group consisted of 43 non-amblyopic children and 17 non-amblyopic adults. Treatment outcomes after a period of one year were defined as successful or unsuccessful when posttreatment amblyopic corrected distance visual acuity (CDVA) was reported as 0.9 versus CDVA 0.8, respectively. AL was measured using a Lenstar LS900 (Haag-Streit AG, Switzerland).ResultsFifty-nine patients showed satisfactory treatment outcomes (55 children and 4 adults), while unsuccessful treatment outcomes were observed in 24 patients (15 children and 9 adults). The mean of amblyopia treatment duration was 1.24 0.76 years. The mean of interocular AL difference in all patients, control, successful and unsuccessful treatment outcome groups were 0.49 0.70mm (range, 0.00–3.89 mm), 0.12 0.07 mm (range, 0.02–0.41), 0.33 0.23 mm (range, 0.00–0.99 mm), and 1.81 0.80 mm (range, 1.14–3.89 mm), respectively. In both age groups, the mean of interocular AL difference in patients with unsuccessful treatment outcomes was greater than those with successful treatment outcomes and that of the control group (P 0.001).ConclusionThe results of this study suggest that the outcome of anisometropic amblyopia treatment may depend on the interocular AL difference.

Transient Eye Shortening During Reading Text With Inverted Contrast: Effects of Refractive Error and Letter Size.

PurposeMyopes have a reduced ability to elicit transient axial eye shortening after imposed positive defocus, which may be due to changes in the biochemical signaling cascade controlling choroidal thickness. We have investigated whether reading with inverted text contrast can still elicit transient axial eye shortening in myopes, like it has been shown in emmetropes.MethodsChanges in axial length before and after reading were measured with the Lenstar LS-900. Text with inverted contrast was read from a large screen at 2 m distance (angular subtense 35.9°, screen luminance matched in all conditions to 86 ± 7 cd/m²) for 30 minutes. Moreover, we investigated the effects of letter sizes. Two text sizes were tested: “small” text (letter height 13.75 arcmin) and “large” text (letter height 34.39 arcmin).ResultsReading text with inverted contrast induced eye shortening (–10.2 ± 9.5 µm) in myopic eyes (n = 11; refraction –3.5 ± 1.9 diopters [D]), showing that an inhibitory signal was still generated by the retina as in emmetropes. In 15 subjects (refraction +1.7 to –4.2 D) we found that small text does not elicit significant differences in axial length (P = 0.09). However, with large text, changes in axial length were clearly different for the both contrast polarities (standard contrast, +1.7 ± 9.0 µm; inverted contrast, –9.7 ± 8.9 µm; P = 0.0017).ConclusionsAlthough positive defocus may not be an effective intervention to inhibit further eye growth in myopes, other visual stimuli can still trigger choroidal thickening and possibly generate signals to decrease myopia progression.Translational RelevanceOur results have shown the optimized text features, which may have a positive impact on myopia control.

Repeatability of a new swept-source optical coherence tomographer and agreement with other three optical biometers.

To investigate the repeatability of Anterion and compare the agreement of ocular biometric measurements and predicted intraocular lens (IOL) powers with other three optical biometers. Flat keratometry (Kf), steep keratometry (Ks), J0 and 45 vectors, central cornea thickness (CCT), anterior chamber depth (ACD), and axial length (AL) from the Anterion, IOLMaster 700, Lenstar LS 900, and OA-2000 were recorded. The IOL powers were calculated with the Hoffer Q, Holladay 1, SRK/T, and Haigis formulas. The repeatability was evaluated using the within-subject standard deviation (Sw), repeatability coefficient (RC), coefficient of variation (COV), and intraclass correlation coefficient (ICC). Inter-device agreement between the four biometers was assessed with the 95% limits of agreement. In total, 101 right eyes of 101 participants were enrolled. The Anterion showed good repeatability for all the included biometric parameters with all the CoV ≤ 0.30% and ICC ≥ 0.930 except for J45 with moderate repeatability (ICC was 0.849). Good agreement was found among the four devices for Kf, Ks, J0, J45, ACD, and AL. Generally, wide 95% LoA was found for the predicted IOL powers with the four IOL calculation formulas between the four devices. The Anterion showed good repeatability of biometric measurements for most parameters. Good agreement among the four optical biometers was achieved for all the parameters except for CCT and the predicted IOL power. The AL values exhibited the best repeatability with Anterion and the best agreement among the biometers in our study.

Assessing the Efficacy of Four Diagnostic Devices and Four Nomograms in Posterior Chamber Phakic Intraocular Lens Size Selection.

To assess the efficacy of different devices and nomograms in predicting the most optimal Implantable Collamer Lens (ICL) (STAAR Surgical) size. This retrospective study includes 73 patients (142 eyes) who underwent ICL placement surgery. Anterior segment measurements were obtained by the OPD-Scan III (Marco), the Lenstar LS 900 (Haag-Streit AG/Alcon Laboratories, Inc), the Galilei G4 (Ziemer), and the VuMax ultrasound biomicroscopy device (UBM) (Sonomed Escalon). The efficacy of the four devices and four nomograms was assessed by comparing the indicated ICL sizes to the patient's postoperative vault measurements. Using white-to-white (WTW) measurements obtained by the Lenstar LS 900 and Galilei G4 coupled with the U.S. Food and Drug Administration's (FDA) (also called the manufacturer's) nomogram predicted the highest percentage (33% and 43%) of the 13.7 mm ICL sizes, respectively. Using the VuMax UBM coupled with the Dougherty nomogram indicated the highest percentage (80%) of the 12.6 mm ICL size. The ICL sizes predicted by UBM using the Parkhurst nomogram were comparable to those deemed ideal according to postoperative vault measurements. The Parkhurst nomogram predicted the most appropriate ICL size. When using WTW measurements, the optimized WTW nomogram showed promising results, especially in eyes whose preoperative calculations suggest low postoperative vaults. Moreover, clinicians should use caution when using the FDA nomogram because it showed a propensity toward indicating oversized ICLs. [J Refract Surg. 2022;38(2):106-111.].

Comparing low-coherence interferometry and A-scan ultrasonography in measuring ocular axial dimensions in young rhesus monkeys

We investigated a commercial low-coherence interferometer (LenStar LS 900 optical biometer) in measuring young rhesus monkey ocular dimensions. Ocular biometry data obtained using a LenStar and an A-scan ultrasound instrument (OPT-scan 1000) from 163 rhesus monkeys during 20–348 days of age were compared by means of coefficients of concordance and 95% limits of agreement. Linear regression was employed to examine and analyze the inter-instrument discrepancies. In young rhesus monkeys, the test-retest reliability of the LenStar was equal to or exceeded that of A-scan ultrasound (intraclass correlation = 0.86 to 0.93). The inter-instrument agreement was strong for vitreous chamber depth and axial length (coefficient of concordance = 0.95 and 0.86, respectively) and moderate for anterior chamber depth and lens thickness (coefficient of concordance = 0.74 and 0.63, respectively). The LenStar systematically underestimated ocular dimensions when compared to A-scan ultrasound (mean magnitude of difference = 0.11–0.57 mm). This difference could be minimized using linear calibration functions to equate LenStar data with ultrasound data. When this method was applied, the values between instruments were in excellent absolute agreement (mean magnitude of difference = 0.004–0.01 mm). In conclusion, the LenStar reliably measured ocular dimensions in young monkeys. When an appropriate calibration function is applied, the LenStar can be used as a substitute for A-scan ultrasonography.

An observational study of the correlation between axial length and retinal nerve fibre layer thickness in myopic eyes in a tertiary care centre in south india

Objective: To assess the correlation between axial length and retinal nerve fibre layer (RNFL) thickness in myopic eyes in a tertiary care hospital in a two-year period (August 2017 to June 2019). Methods: Institutional ethics committee approval was obtained. Written and informed consent was obtained from all the participants. One hundred eyes of 58 patients were screened. Myopic patients with > -0.50 D myopia in the age group of 18 to 40 years with intraocular pressure (IOP) <20 mm Hg were included in the study. Patients with a history of ocular trauma, glaucoma, ocular surgeries, optic nerve or macular diseases, pathological myopia, and media opacities were excluded from the study. An ophthalmic evaluation was done by assessing the visual acuity, IOP, slit-lamp examination, and perimetry using Humphrey field analyser II (Swedish interactive threshold algorithm SITATM testing strategy). After dilating the pupils with Tropicamide plus, posterior segment evaluation was done using a 90 D lens with slit lamp bio-microscopy as well as indirect ophthalmoscopy and 20 D lens. The axial length was measured using Lenstar LS 900. Optical Coherence Tomography (OCT) images were obtained using a 3 D OCT 1 Maestro machine by a single observer. Results: There was a statistically significant association between axial length and RNFL thickness in myopic eyes (P = 0.0003). As the axial length of the eyeball increases, the RNFL thickness decreases in all four quadrants except the temporal quadrant, producing a statistically significant negative correlation (r = -0.3551). Conclusion: There is a statistically significant association between axial length and RNFL thicknesses in all quadrants except the temporal quadrant. The negative correlation between axial length and RNFL thickness would be useful in avoiding misdiagnosis of glaucoma since RNFL thickness is low in both glaucoma and myopia.

Ocular Biometric Values and Prevalence of Corneal Astigmatism in Patients Candidate for Cataract Surgery.

Purpose:To analyze the biometric values and the prevalence of corneal astigmatism in cataract surgery candidates.Methods:This is a prospective study. Ocular biometric values and corneal keratometric astigmatism were measured by optical low-coherence reflectometry (Lenstar LS 900) before surgery in patients who were candidates for cataract extraction surgery. Descriptive measurements of biometric dimensions and keratometric cylinder data and their correlations with sex and age were evaluated.Results:Ocular biometric and keratometric values from 2084 eyes of 2084 patients (mean age 66.43, range 19–95 years) were analyzed. The mean values were as follows: corneal astigmatism 0.89 diopter (D), mean corneal keratometry 44.29 D, central corneal thickness 534 μ, internal anterior chamber depth (ACD) 3.11 mm, lens thickness 4.50 mm, and axial length 23.35 mm. Corneal astigmatism was <1.25 D in 1660 (79.5%) of eyes. Astigmatism was with-the-rule in 976 (46.8%) of eyes, against-the-rule (ATR) in 702 (33.7%), and oblique in 406 (19.5%). Analysis of corneal astigmatism revealed a change toward “ATR” with age which was not statistically significant. The ACD was correlated with age. The amount of corneal astigmatism had no correlation with age and sex.Conclusion:Corneal astigmatism was higher than 1.25 D in about 21% of cataract surgery candidates with slight differences between the various age ranges and had no correlation with age and sex.

Biometry in Silicone Oil Filled Eyes. A Review

The “gold standard” of modern vitreoretinal surgery is silicone oil tamponade of the vitreous cavity. The lens opacity development is in the list of complications of prolonged silicone oil eye filling (from 2 weeks to 2 years). Polydimethylsiloxanes hydrophobicity, direct contact with the front of the silicone bladder, macrophage and toxic reaction, trophic disturbances are the causes leading to the cataract initiation. This makes the problem of cataract surgery and preliminary intraocular lens calculation in silicone oil filled eyes before its removing very relevant as well as cloudy retina visualization and the necessity of minimization of number of operations through their combination. Certainly, the main error in IOL power calculation is associated with axial length measurement inaccuracy, as the most significant term of an equation. Silicone oil filled eyes biometry errors, and, consequently, postoperative refraction biases remain unresolved problem until now. To date authors report only 58 % of cases in which target refraction was achieved after combined surgery. Some researchers figure out that average calculation error after phacoemulsification with IOL implantation in avitreal eyes was 0.8 D despite of the optical biometry usage. Today it is represented by several methods: partial coherent interferometry, optical low-coherence reflectometry and optical coherence tomography, which are implemented in devices such as IOLMaster 500, Lenstar LS 900 and IOLMaster 700, which have their own characteristics and measurement accuracy. Their advantages as well as creation an accurate IOL calculation method for silicone oil filled eyes could reduce postoperative refraction error that outline significant medical and social problem.

The Effect of Axial Length Elongation on Corneal Biomechanical Property.

Background: To investigate the correlation between the corneal biomechanical parameter stress-strain index (SSI) and axial length (AL) in moderately elongated eye (MEE) and severely elongated eye (SEE). Methods: This study included 117 eyes from 117 participants. Among them, 59 (50.4%) had MEE (AL<26 mm) and 58 (49.6%) had SEE (AL≥26 mm). AL was measured using Lenstar LS-900, and central corneal thickness (CCT) and anterior chamber volume (ACV) were measured using Pentacam. SSI was measured via corneal visualisation Scheimpflug technology (Corvis ST). Kolmogorov-Smirnov test, Student’s t-test, and Pearson and partial correlation analyses were used for statistical analyses. Results: The mean (±SD) SSI was 1.08 ± 0.15 in the MEE group and 0.92 ± 0.13 in the SEE group (p < 0.01). SSI was positively correlated with age (MEE: r = 0.326, p < 0.05; SEE: r = 0.298, p < 0.05) in both groups; it was negatively correlated with AL (r = −0.476, p < 0.001) in the MEE group but not in the SEE group (p > 0.05). CCT was negatively correlated with AL (r = −0.289, p < 0.05) and ACV positively correlated with AL (r = 0.444, p < 0.001) in the MEE group. Neither CCT nor ACV was correlated with AL (p > 0.05) in the SEE group. Conclusion: Corneal biomechanical parameter SSI, which represents the stiffness of corneal tissue, was lower in the SEE group than in the MEE group. When analyzed separately, SSI was negatively correlated with AL in the MEE group, but not in the SEE group, which may provide insight into different ocular growth patterns between lower myopia and higher myopia.