The Effect of Cycloplegia on the Ocular Biometric and Anterior Segment Parameters: A Cross-Sectional Study

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.

Suitability of multifunction devices Myah and Myopia Master for monitoring myopia progression in children and adults

PURPOSE

To assess the feasibility of using multifunction instruments to measure axial length for monitoring myopia progression in children and adults.

METHODS

Axial length was measured in 60 children (aged 6-18 years) and 60 adults (aged 19-50 years) with multifunction instruments (Myah and Myopia Master) and stand-alone biometers (Lenstar LS900 and IOLMaster 700). Repeatability (measurements by the same examiner) and reproducibility (measurements by different examiners) were computed as the within-subject standard deviation (Sw) and 95% limits of agreement (LoA). Inter-instrument agreement was computed as intraclass correlation coefficients. The threshold for detecting myopic progression was taken as 0.1 mm. Measures were repeated only in children following the administration of 1% tropicamide to determine the impact of cycloplegia on axial length.

RESULTS

Overall, the IOLMaster 700 had the best repeatability in children (0.014 mm) and adults (0.009 mm). Repeatability Sw values for all devices ranged from 0.005 to 0.021 mm (children) and 0.003 to 0.016 mm (adults). In children, reproducibility fell within 0.1 mm 95% of the time for the Myah, Myopia Master and IOLMaster 700. Agreement among all devices was classified as excellent (ICC 0.999; 95% CI 0.998-0.999), but the 95% LoA among the Myah, Myopia Master and Lenstar LS900 was ≥0.1 mm. Cycloplegia had no statistically significant effect on axial length (all p > 0.13).

CONCLUSIONS

The Myah and Myopia Master multifunction instruments demonstrated good repeatability and reproducibility, and their accuracy was comparable to stand-alone biometers. Axial length measurements using different instruments can be considered interchangeable but should be compared with some caution. Accurate axial length measurements can be obtained without cycloplegia. The multifunction instruments Myah and Myopia Master are as well suited for monitoring myopia progression in children as the stand-alone biometers IOLMaster 700 and Lenstar LS900.

Longitudinal Changes in Refractive Development in Highly Hyperopic Children: A 2.6-11.2 Year Follow-up of Preschoolers Diagnosed with High Hyperopia

PURPOSE

This study aims to elucidate the longitudinal refractive and ocular biometric alterations in preschool children with high hyperopia who underwent early interventions.

METHODS

We conducted a retrospective analysis of preschool children diagnosed with high hyperopia at Tianjin Medical University Eye Hospital between 2011 and 2023. Inclusion criteria required an initial examination with cycloplegic refraction, bilateral spherical equivalent power (SE) ≥ +5.00D with a difference <1.00D, a minimum two-year follow-up, and at least three ocular biometric measurements. The annual axial growth rate evaluated emmetropization in highly hyperopic children. We applied Restricted Cubic Spline (RCS) models to explore potential nonlinear relationships between age and spherical equivalent, axial length, corneal curvature, and axial length-to-corneal curvature ratio. Additionally, Mixed-effects models were employed to investigate factors associated with changes in refractive error and axial length.

RESULTS

The study enrolled 60 eligible subjects, with a median initial diagnosis age of 3.5 years (IQR, 2.8-4.9 years) and a median last visit age of 9.3 years (IQR, 8.1-10.8 years). The average follow-up duration was 5.7 years. RCS analysis revealed notable nonlinear changes in spherical equivalent power, axial length, and axial length-to-corneal curvature ratio, although corneal curvature displayed no statistically significant nonlinear trend. Factors affecting SE changes included the presence of strabismus, the use of cycloplegia, baseline SE, and age. Conversely, changes in axial length solely correlated with baseline axial length and age.

CONCLUSION

Highly hyperopic preschool children undergoing early intervention display a marked emmetropization tendency, though most still remain moderately to highly hyperopic, with the progression of refractive changes showing non-uniform patterns with respect to age.

Changes in ocular biometrics following cycloplegic refraction in strabismic and amblyopic children

This study was aimed to analyze ocular biometric changes following cycloplegia in pediatric patients with strabismus and amblyopia. Cycloplegia is routinely used to measure refractive error accurately by paralyzing accommodation. However, effects on axial length (AL), anterior chamber depth (ACD), keratometry (Km), and white-to-white distance (WTW) are not well studied in this population. This retrospective study examined 797 patients (1566 eyes) undergoing cycloplegic refraction at a Samsung Kangbuk hospital pediatric ophthalmology clinic from 2010 to 2023. Ocular biometry was measured before and after instilling 1% cyclopentolate and 0.5% phenylephrine/0.5% tropicamide. Patients were categorized by strabismus diagnosis, age, refractive error and amblyopia status. Differences in AL, ACD, Km, WTW, and refractive error pre- and post-cycloplegia were analyzed using paired t tests. ACD (3.44 ± 0.33 vs 3.58 ± 0.29 mm, P < .05) and WTW (12.09 ± 0.42 vs 12.30 ± 0.60 mm, P < .05) increased significantly after cycloplegia in all groups except other strabismus subgroup (Cs) in both parameters and youngest subgroup (G1) in ACD. Refractive error demonstrated a hyperopic shift from -0.48 ± 3.00 D to -0.06 ± 3.32 D (P < .05) in overall and a myopic shift from -6.97 ± 4.27 to -8.10 ± 2.26 in high myopia (HM). Also, AL and Km did not change significantly. In conclusion, cycloplegia impacts ocular biometrics in children with strabismus and amblyopia, significantly increasing ACD and WTW. Refractive error shifts hyperopically in esotropia subgroup (ET) and myopically in high myopia subgroup (HM), eldest subgroup (G3) relating more to anterior segment changes than AL/Km. Understanding cycloplegic effects on biometry is important for optimizing refractive correction in these patients.

Effect of mydriasis on chord mu value in cataract surgery candidates

PURPOSE

This study investigates the relationship between pupil size during biometry examinations and the chord mu value in candidates for cataract surgery.

METHODS

Retrospective analysis of ocular biometry measurements was performed on consecutive cataract surgery candidates above 50 years of age, examined between 2018 and 2020 at a single tertiary referral center. Statistical analysis assessed the association between pupil size and the chord mu value. The population was categorized into groups based on pupil size, and an analysis was conducted on the barycenter positions of the iris and pupil center for each group.

RESULTS

The analysis included 2877 patients. A weak positive correlation was observed between the chord mu value and pupil size using Pearson's test (r = 0.160, p < 0.01). Group stratification by pupil size indicated temporal and inferior shifts in pupil center barycenter as pupil size increased, reflecting asymmetrical pupil dilation during mydriasis. A moderate positive correlation between the chord mu value and chord alpha value was identified (Pearson's test, r = 0.641, p < 0.01). As expected, no correlation was found between chord alpha value and pupil size.

CONCLUSIONS

Chord mu values were higher in patients with mydriatic pupils, likely due to asymmetric pupil dilation and center displacement. Evaluating chord mu values requires considering pupil status and conducting biometry under standardized lighting to prevent misinterpretation caused by pharmacological dilation. This caution is crucial to avoid erroneously excluding eligible patients from multifocal IOL implants. Alternatively, the chord alpha value could serve as a more appropriate alternative in such scenarios.

Assessing the Impact of Tropicamide on Anterior Segment Parameters in Diabetic Patients: A Randomized Clinical Trial

INTRODUCTION

Evaluation of anterior segment parameters is crucial in ophthalmic procedures such as intraocular surgeries and contact lens fitting. However, the use of tropicamide in diabetic patients presents challenges due to its potential impact on biometric measurements. This study aims to investigate and compare the effects of 0.5% and 1% tropicamide on anterior segment parameters in diabetic patients.

METHODS

This double-masked randomized clinical trial enrolled 98 patients with diabetes mellitus. Participants were randomly assigned to receive either 0.5% or 1% tropicamide. Anterior segment parameters were measured using Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany) before and 30 minutes after tropicamide administration. Parameters included anterior chamber depth (ACD), anterior chamber volume (ACV), anterior chamber angle (ACA), keratometry, central corneal thickness (CCT), white-to-white distance (WTW), and pupillary diameter (PD).

RESULTS

Both concentrations of 0.5% and 1% tropicamide induced significant changes in anterior segment parameters. There was a notable increase in PD (2.99 ± 0.62, 3.11 ± 0.55, respectively, both P-values < 0.001), ACD (both 0.10 ± 0.05, both P-values < 0.001), ACV (16.69 ± 9.56, 17.51 ± 9.26, respectively, both P-values < 0.001), and WTW (0.06 ± 0.14, 0.03 ± 0.30, respectively, both P-values < 0.001), along with a decrease in ACA (-3.50 ± 10.65, -3.30 ± 6.87, P-value < 0.001 and P-value=0.001, respectively), and CCT (-6.10 ± 8.06, -6.39 ± 9.97, respectively, both P-values < 0.001) post-dilation. However, no significant changes were observed in keratometry (front Km (-0.03 ± 0.19, -0.04 ± 0.21, respectively), back Km (0.01 ± 0.05, 0.004 ± 0.05, respectively), P-values> 0.05).

CONCLUSION

Both concentrations of tropicamide exhibited comparable effects on anterior segment parameters in diabetic patients. These post-dilation changes should be considered for accurate intraocular lens power calculation and decision-making for cataract, phakic intraocular lens, and refractive surgeries.

Effect of Cycloplegia on Anterior Segment Structures and Scleral Thickness in Emmetropic Eyes

Purpose: To evaluate the effects of topical cyclopentolate hydrochloride-induced cycloplegia on anterior segment biomechanics in emmetropic eyes using anterior segment-optical coherence tomography (AS-OCT). Methods: Twenty-five emmetropic eyes of 25 volunteers were included. All underwent central corneal thickness (CCT) and anterior chamber depth (ACD) measurements. Anterior scleral thickness (AST) was measured at the level of the scleral spur (SS)(AST-0), 1,000 μm posterior of the SS (AST-1), and 2,000 μm posterior of the SS (AST-2) in the nasal and temporal quadrants using AS-OCT. All measurements were repeated after cycloplegia. Results: The mean age was 30.6 ± 12.4 (8-45) years. The mean CCT did not significantly change after cycloplegia (P = 0.7). The mean ACD was significantly increased [3.3 ± 0.2 (2.7-3.9) to 3.7 ± 0.3 (3-4.2) μm; P = 0.001]. In the nasal quadrant, the mean AST-1 and AST-2 were 512.3 ± 34.4 (433-570) and 529.6 ± 34.2 (449-599); decreased to 478 ± 26.8 (423-530) and 486.2 ± 28.3 (422-544) μm, respectively, after cycloplegia (P = 0.00; P = 0.00). In the temporal quadrant, the mean AST-1 and AST-2 were 522.5 ± 24.7 (473-578) and 527.2 ± 39.9 (450-604); decreased to 481.1 ± 33.7 (421-550) and 484.6 ± 26.6 (433-528) μm, respectively (P = 0.00; P = 0.00). There was no significant difference in AST-0 after cycloplegia in both quadrants [from 697.5 ± 46 (605-785) to 709.5 ± 64.7 (565-785) for nasal and from 718.4 ± 40.1 (632-796) to 722.9 ± 60.6 (596-838) for temporal; P = 0.2; P = 0.3, respectively]. Conclusion: After cycloplegia, there was a significant thinning of ASTs posterior to SS and a slight increase in AST in the SS level. ACD deepened after cycloplegia, and there was no significant change in CCT. Cycloplegic agents temporarily inhibit ciliary muscle contraction and may affect anterior segment parameters and sclera. Inhibition of forward-inward movement of the ciliary body by cycloplegia affects ASTs and ACD by causing a change in the mechanical force of the ciliary muscle on the sclera.

Effects of atropine and tropicamide on ocular biological parameters in children: a prospective observational study

BACKGROUND

The effectiveness of cycloplegia in delaying the progression of myopia and its application in refractive examination in children have been extensively studied, but there are still few studies on the effects of atropine/tropicamide on ocular biological parameters. Therefore, the purpose of this study was to explore the effects of atropine/tropicamide on children's ocular biological parameters in different age groups and the differences between them.

METHODS

This was a prospective observational study in which all school children were examined for dioptres and ocular biological parameters in the outpatient clinic, and 1% atropine or tropicamide was used for treatment. After examination, we enrolled the patients grouped by age (age from 2 to 12 years treated by atropine, 55 cases; age from 2 to 10 years treated by tropicamide, 70 cases; age from 14 to 17 years treated by tropicamide, 70 cases). The ocular biological parameters of each patient before and after cycloplegia were measured, and the difference and its absolute value were calculated for statistical analysis using an independent-samples t test.

RESULTS

We compared the value and the absolute value of the differences in ocular biological parameters before and after cycloplegia in the same age group, and we found that the differences were not statistically significant (P > 0.05). There were significant differences in the corresponding values of AL, K1 and ACD among the different age groups (P < 0.05). Before cycloplegia, there were significant differences in AL, K, K1, K2 and ACD in different age groups (P < 0.05). However, the differences in AL, K, K1, K2 and ACD among different age groups disappeared after cycloplegia (P > 0.05).

CONCLUSIONS

This study demonstrated that atropine/tropicamide have different effects on cycloplegia in children of different ages. The effects of atropine/tropicamide on ocular biological parameters should be fully considered when evaluating the refractive state before refractive surgery or mydriasis optometry for children of different ages.

Effect of cycloplegic agents (1% cyclopentolate hydrochloride and 1% tropicamide) on anterior segment parameters

Background

Cycloplegic drops are commonly used in ophthalmology practice. Changes in anterior segment parameters may occur after cycloplegia. These changes can be evaluated with corneal topography.

Objective

This study aimed to compare the effects of 1% cyclopentolate hydrochloride and 1% tropicamide on anterior segment parameters using the Sirius Scheimpflug imaging technique.

Design

A cross-sectional study.

Methods

One hundred twenty eyes of sixty healthy volunteers with spherical equivalent (SE) values of 0 to ±1 diopter (D) were studied. The right eye of each subject had instillation of cyclopentolate hydrochloride 1% (Group 1) and the left eye of each subject had instillation of tropicamide 1% (Group 2). SE, intraocular pressure, and corneal topography measurements were performed before and 40 min after instillation were compared.

Results

In Group 1, SE, aqueous depth, anterior chamber depth, iridocorneal angle (ICA), anterior chamber volume (ACV), and pupil size (PS) values were significantly increased (p < 0.001, p = 0.01, p < 0.001, p = 0.03, p < 0.001, and p < 0.001, respectively). In Group 2, SE, ICA, ACV, and PS were significantly increased (p < 0.001 for all). Keratometric values (K1 and K2) and central corneal thickness changed insignificantly in both groups (p > 0.05). The effects of the two administered agents on all parameters were similar (p > 0.05).

Conclusions

Cyclopentolate hydrochloride and tropicamide affected SE, ICA, ACV, and PS values significantly. These parameters are important in intraocular lens (IOL) power calculations. PS is also important in refractive surgery and cataract surgery with multifocal IOL implantation. Although there was an insignificant difference between the agents, the effects of tropicamide on the parameters were smaller than those of cyclopentolate.

Prediction of spherical equivalent difference before and after cycloplegia in school-age children with machine learning algorithms

Purpose

To predict the need for cycloplegic assessment, as well as refractive state under cycloplegia, based on non-cycloplegic ocular parameters in school-age children.

Design

Random cluster sampling.

Methods

The cross-sectional study was conducted from December 2018 to January 2019. Random cluster sampling was used to select 2,467 students aged 6-18 years. All participants were from primary school, middle school and high school. Visual acuity, optical biometry, intraocular pressure, accommodation lag, gaze deviation in primary position, non-cycloplegic and cycloplegic autorefraction were conducted. A binary classification model and a three-way classification model were established to predict the necessity of cycloplegia and the refractive status, respectively. A regression model was also developed to predict the refractive error using machine learning algorithms.

Results

The accuracy of the model recognizing requirement of cycloplegia was 68.5-77.0% and the AUC was 0.762-0.833. The model for prediction of SE had performances of R^2 0.889-0.927, MSE 0.250-0.380, MAE 0.372-0.436 and r 0.943-0.963. As the prediction of refractive error status, the accuracy and F1 score was 80.3-81.7% and 0.757-0.775, respectively. There was no statistical difference between the distribution of refractive status predicted by the machine learning models and the one obtained under cycloplegic conditions in school-age students.

Conclusion

Based on big data acquisition and machine learning techniques, the difference before and after cycloplegia can be effectively predicted in school-age children. This study provides a theoretical basis and supporting evidence for the epidemiological study of myopia and the accurate analysis of vision screening data and optometry services.

Changes in ocular biological parameters after cycloplegia based on dioptre, age and sex

The effects of cycloplegia on ocular biological parameters in children have been extensively studied, but few studies have compared these parameters between different refractive states, ages, and sexes. Therefore, the purpose of this study was to investigate the changes in ocular biometry before and after cycloplegia in different groups based on dioptre, age and sex. We examined a total of 2049 participants in this cross-sectional study. A comprehensive eye examination was conducted before cycloplegia. Cycloplegia was implemented with the application of atropine or tropicamide. Ocular biological parameters were evaluated after cycloplegia, including axial length (AL), mean keratometry (K), flat keratometry (K1), steep keratometry (K2), central corneal thickness (CCT), anterior chamber depth (ACD) and white-to-white (WTW) distance. All the participants were categorized based on dioptre, age and sex. Statistical analysis was performed with paired t tests and Wilcoxon signed-rank tests. Regarding dioptre, AL was found to be increased significantly in the Fs, Ast and FA (p < 0.05) postcycloplegia groups. We observed significant increases in K, K1, K2 and ACD in the Fs group (p < 0.05) after cycloplegia. Regarding age, we found significant increases in AL, CCT and ACD in group 1 (p < 0.05), but AL decreased significantly in groups 2 and 3 (p < 0.05) postcycloplegia. There were no significant changes found in K, K1 and K2 in the three groups after cycloplegia (p > 0.05). Regarding sex, AL and WTW were found to decrease significantly among males and increase significantly among females (p < 0.05) postcycloplegia, while K, K1 and K2 showed the opposite trends. This study showed that there were differences in some ocular biological parameters after cycloplegia across different groups; in particular, there were significant differences in AL, CCT and ACD. Attention should be devoted to the influence of cycloplegia in clinical work.

Effect of pupil dilation on biometry measurements and intraocular lens power in eyes with high myopia

Purpose

The present study sought to evaluate the effects of pupil dilation on ocular parameter measurements and intraocular lens (IOL) power calculation using IOLMaster in highly myopic cataract patients.

Materials and methods

A total of 233 eyes were included in this prospective study and assigned to four groups based on range of axial length (AL) as follows: group A:26–28 mm, group B:28–30 mm, group C:30–32 mm, and group D:32–36 mm. Flattest and steepest keratometry (K1 and K2), AL, anterior chamber depth (ACD), lens thickness (LT), and white-to-white (WtW) were determined using IOLMaster before and after administration of topical tropicamide. The corresponding IOL powers were calculated using Sanders–Retzlaff–Kraff/theoretical (SRK/T), Haigis, and Barrett Universal II formulas.

Results

Variations in AL, K1 and K2 following dilation were not significant (P > 0.05 in all groups). The results showed that ACD increased significantly after dilation (P = 0.000 in all groups), whereas LT decreased significantly after dilation (P = 0.000, 0.000, 0.001, and 0.003). Post-dilation WtW increased significantly in Group A, B, and C (P = 0.001, 0.001, and 0.025) but not in Group D. When IOL power was calculated as a discrete variable, significant differences were observed between pre- and post-dilation IOL power.

Conclusion

Pupil dilation in cataract eyes with high myopia does not cause significant changes in AL and K. However, it significantly increases ACD as well as WtW values and significantly decreases the LT value. Surgeons should evaluate the effect of pupil dilation on IOL power prediction as the present findings show extreme cases. Notably, Barrett Universal II formula had the best concordance between different pupil conditions in long eyes.

An evaluation of the IOLMaster 700 and its agreement with the IOLMaster v3 in children

PURPOSE

To evaluate the repeatability and reproducibility of the swept-source optical coherence tomographer Zeiss IOLMaster 700 and compare its outputs with those obtained using partial coherence interferometry (Zeiss IOLMaster v3) in a healthy, paediatric population.

METHODS

This is a cross-sectional, observational study. Examiner 1 took two sets of biometric measurements (axial length [AL], mean corneal radius of curvature [K_mean ], anterior chamber depth [ACD] and lens thickness [LT]) using the IOLMaster 700, and one set of measurements (AL, K_mean and ACD) using the IOLMaster v3. Examiner 2 took one full set of measurements using the IOLMaster 700. Mean differences and 95% limits of agreement (LOA) were calculated, and Bland and Altman plots used to explore repeatability and reproducibility of the IOLMaster 700 alongside establishing its agreement with the IOLMaster v3.

RESULTS

Mean participant age was 7.52 ± 0.58 years. Repeatability analyses demonstrated small mean differences and narrow 95% LOA for AL (0.001, -0.013 to 0.015 mm), K_mean (0.002, -0.020 to 0.024 mm), ACD (-0.003, -0.031 to 0.024 mm) and LT (0.001, -0.024 to 0.026 mm), respectively. Similarly, small mean differences and narrow 95% LOA established excellent reproducibility (AL 0.001, -0.016 to 0.018 mm; K_mean -0.001, -0.027 to 0.025 mm; ACD -0.010, -0.041 to 0.021 mm; LT 0.002, -0.016 to 0.020 mm). The IOLMaster 700 and IOLMaster v3 demonstrated good agreement with small mean differences and narrow 95% LOA (AL 0.009, -0.034 to 0.052 mm; K_mean 0.016, -0.013 to 0.044 mm; ACD 0.134, 0.055 to 0.212 mm).

CONCLUSIONS

When used within a paediatric population, these data demonstrate the IOLMaster 700 to be highly repeatable and reproducible for measures of AL, K_mean , ACD and LT. There is excellent inter-instrument agreement between the IOLMaster 700 and IOLMaster v3 for measures of AL and K_mean . ACD measurements show weaker agreement. These data will be useful when considering reports from population-based studies of refractive error and clinical myopia research.

Comparison of Simulated and True Keratometry Measurements Using Swept-Source Optical Coherence Tomography and Dual Scheimpflug-Placido Imaging

Purpose

To compare simulated and total keratometry and corneal astigmatism values between the IOLMaster 700 and Galilei G4 devices.

Methods

A retrospective chart review was conducted for all patients undergoing phacoemulsification by a single surgeon (RTP) from March through September 2020 and who underwent imaging with both the IOLMaster 700 and Galilei G4. Exclusion criteria were prior corneal surgery, keratectatic diseases and inability to obtain a reliable image during image acquisition. Mean, flat, and steep keratometry values as well as astigmatism magnitude were compared.

Results

A total of 200 eyes of 100 patients were included. Intraclass correlation coefficients (ICC) were moderate or high for all variables. Mean difference ± SD in SimK and TrueK between devices (G4-IOLM) was 0.05 ± 0.318 diopters and −1.1156 ± 0.438 diopters, respectively (p < 0.05 for both). The IOLM measured steeper TrueK value than the G4. For SimK, there was a statistically significant difference between devices only for mean keratometry (K), whereas for TrueK, there were significant differences in flat K, steep K, and mean K. Astigmatism analysis revealed a difference in mean (±SD) SimK of 0.07 (±0.57) D at 94 degrees and in mean TrueK of 0.04 (±0.85) D at 108 degrees.

Conclusion

Though there is overall good correlation between the IOLMaster 700 and Galilei G4 in SimK and astigmatism measurements, there is a significant difference in TrueK measurements, with the IOLM measuring steeper values by about 1.0 diopter as compared to the G4.

The Effect of Cyclopentolate on Ocular Biometric Components

SIGNIFICANCE

It is apparent that a variety of biometric changes are caused by different types of cycloplegic eye drops. However, these effects are inconsistent and have not been reported in different refractive groups.

PURPOSE

The purpose of this study was to determine the effect of cyclopentolate 1% on ocular biometric components in different types of refractive errors in children.

METHODS

This cross-sectional study was conducted on 226 eyes of 113 schoolchildren in Shahroud, northeast Iran, with a mean ± standard deviation age of 9.20 ± 1.65 years. All participants had noncycloplegic and cycloplegic objective refraction using an autorefractometer. Cycloplegia was induced using cyclopentolate 1% eye drops. Biometric measurements were made with Allegro Biograph (WaveLight AG, Erlangen, Germany) before and after administering cycloplegic drops. Mixed-effect model regression was used to analyze the data.

RESULTS

After cycloplegia, the vitreous chamber depth (VCD) (-0.043; 95% confidence interval [CI], -0.067 to -0.019 mm), lens thickness (-0.146; 95% CI, -0.175 to -0.117 mm), axial length (-0.009; 95% CI, -0.012 to -0.006 mm), and lens power (-0.335; 95% CI, -0.463 to -0.208 D) decreased significantly, whereas the anterior chamber depth (ACD) (0.183; 95% CI, 0.164 to 0.202 mm), anterior segment length (0.036; 95% CI, 0.014 to 0.058) mm), lens central point (0.109; 95% CI, 0.094 to 0.124 mm), and pupil diameter (1.599; 95% CI, 1.482 to 1.716 mm) increased (P value for all tests, <.001). For changes in VCD and ACD, a significant interaction was observed between different types of refractive errors and cycloplegia, such that the adjusted mean change for ACD was significantly lower and for VCD was significantly higher in hyperopes compared with emmetropes. Lens center moves backward in myopes (0.17 mm) and stays the same in hyperopes under cycloplegia.

CONCLUSIONS

According to the findings of this study, cycloplegia reduces the thickness of the crystalline lens and subsequently causes an increase in the ACD. Cycloplegia-related ocular biometric changes were different by type of refractive error.

Effects of Cyclopentolate Hydrochloride Dosage on Anterior Segment Parameters in Young Adults (Measured with Pentacam)

Purpose

To assess the effects of 0.5% and 1% cyclopentolate on the main parameters of the anterior segment (central corneal thickness (CCT), anterior chamber angle (ACA), depth (ACD) and volume (ACV)) in low/moderate myopia and hyperopia along with the effect on IOP.

Patients and Methods

Both eyes of 30 subjects (15 myopic and 15 hyperopic) with mean age±standard deviation of 21.4±3.6 years were enrolled. Each participant was administered two drops of cyclopentolate 1% in the right eye and two drops of cyclopentolate 0.5% in the left eye, 15 minutes apart. All participants underwent intraocular pressure (IOP) measurement using noncontact tonometry, and anterior chamber parameter measurement using Pentacam.

Results

Following the use of 0.5% and 1% cyclopentolate among the hyperopic group, there was a statistically significant increase in ACD for 1% (pre 2.762±0.28 mm and post 2.89±0.25 mm) and 0.5% (pre 2.71±0.28 and post 2.86±0.27 mm) and ACV for 1% (pre 141.40±20.59 mm³ and post 154.35±19.69 mm³) and 0.5% (pre 137.40±20.48 mm³ and post 152.93±20.50 mm³). In contrast, ACA decreased with both doses 1% and 0.5%, but was not statistically significant (p for both >0.05%). With 0.5% and 1% cyclopentolate among the myopia group, there was a significant increase in ACD following cyclopentolate 1% (pre 3.18±0.22 mm and post 3.25±0.21 mm) and 0.5% (pre 3.200±0.22 mm and post 3.26±0.05 mm), p˂0.05. The ACV was significantly increased following 1% cyclopentolate, p˂0.001. The ACA showed a statistically significant decrease following cyclopentolate 1%, P=0.01, but not a significant decrease after cyclopentolate 0.5%, P=0.170. There was a significant increase in the IOP after 1%, p˂0.001, while a decrease with 0.5%, p=0.008.

Conclusion

A topical dosage of cyclopentolate 1% showed significant changes in ACA and ACV among the hyperopia and myopic groups compared to 0.5%. Therefore, it is important to consider the use of a 0.5% cyclopentolate dosage to minimize changes to anterior chamber parameters.

The effect of cycloplegia on the ocular biometry and intraocular lens power based on age

BACKGROUND

To investigate the effect of cycloplegia on the ocular biometry and intraocular lens (IOL) power in different age groups.

METHODS

This cross-sectional study enrolled 240 right eyes of 240 healthy volunteers. Three groups were formed (range to years; group 1: 50-60, group 2: 30-40 and group 3: 10-20, respectively). We measured keratometry, central corneal thickness (CCT), white-to-white (WtW) distance, anterior chamber depth (ACD), and axial lentgh (AL) both before and after cycloplegia. The IOL powers were calculated using Sanders-Retzlaff-Kraff/theoretical (SRK/T), Holladay 1 and Haigis formulas. AL-Scan (Nidek Co., Gamagori, Japan) was used for all measurements.

RESULTS

There was a significant increased in keratometry, CCT, ACD, AL, and Holladay 1 after cycloplegia (p < 0.05), whereas WtW, SRK/T, and Haigis were not changed significantly in group 1 (p > 0.05). Keratometry, SRK/T, Haigis, and Holladay 1 significantly decreased; ACD and WtW significantly increased postcycloplegia (p < 0.05) but AL and CCT did not change significantly in group 2 (p > 0.05). Significant increased in ACD, CCT, WtW, and AL, significant decreased in SRK/T and Haigis were observed postcycloplegia (p < 0.05), while the changes in keratometry and Holladay 1 were not significant in group 3 (p > 0.05).

CONCLUSIONS

This study demonstrated there is significant difference in many ocular parameters and IOL power formulas before and after cycloplegia. Especially, ACD showed significant changes in all age groups. Therefore, to avoid refractive prediction errors the IOL power calculation formulas using the ACD should be considered.