Effect of Cycloplegia on Corneal Biometrics and Refractive State

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.

Understanding accommodative control in the clinic: Modeling latency and amplitude for uncorrected refractive error, presbyopia and cycloplegia

Accommodation is the process of adjusting the eye's optical power so as to focus at different distances. Uncorrected refractive error and/or functional presbyopia mean that sharp focus may not be achievable for some distances, so observers experience sustained defocus. Here, we identify a problem with current models of accommodative control: They predict excessive internal responses to stimuli outside accommodative range, leading to unrealistic adaptation effects. Specifically, after prolonged exposure to stimuli outside range, current models predict long latencies in the accommodative response to stimuli within range, as well as unrealistic dynamics and amplitudes of accommodative vergence innervation driven by the accommodative neural controller. These behaviors are not observed empirically. To solve this issue, we propose that the input to blur-driven accommodation is not retinal defocus, but correctable defocus. Predictive models of accommodative control already estimate demand from sensed defocus, using a realistic "virtual plant" to estimate accommodation. Correctable defocus can be obtained by restricting this demand to values physically attainable by the eye. If we further postulate that correctable defocus is computed using an idealized virtual plant that retains a young accommodative range, we can explain why accommodative-convergence responses are observed for stimuli that are too near-but not too far-to focus on. We model cycloplegia as a change in gain, and postulate a form of neural myopia to explain the additional relaxation of accommodation often seen with cycloplegia. This model produces plausible predictions for the accommodative response and accommodative convergence signal in a wide range of clinically relevant situations.

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.

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.

The Combined Effect of Tropicamide and Phenylephrine on Corneal Astigmatism Axis

PURPOSE

To analyze astigmatism axis changes after tropicamide and phenylephrine combined instillation.

METHOD

One hundred and thirty-one eyes from 66 patients enrolled this cross-sectional study. An extensive ocular examination was carried out prior to tropicamide and phenylephrine instillation. Power and axis value from flat, steep, and mean keratometry were calculated using an Auto Kerato-Refractometer (AKR). Later, topography and tomography maps were evaluated with Pentacam HR® (Oculus, Wetzlar, Germany). Subsequently, a single drop of tropicamide 1% and phenylephrine hydrochloride 10% were instilled twice, with a five-minute gap between each instillation. After 30 minutes, the AKR and Pentacam HR® tests were repeated.

RESULTS

Incyclotorsion was found in 59 eyes (45.1%) and mean absolute incyclotorsion change was 3.91 ± 3.62 degrees (0.10 to 14.20). Excyclotorsion was found in 72 eyes (54.9%) and mean excyclotorsion change was 4.99 ± 5.94 degrees (0.20 to 36.20). We observed that 74.6% and 68.1% of eyes experienced incyclotorsion and excyclotorsion within 0 to 5 degrees, respectively. Fewer patients experienced incyclotorsion and excyclotorsion changes within 5 to 10 degrees, precisely 11.8% and 19.4%, respectively. Eyes that experienced over 10 degrees of incyclotorsion and excyclotorsion were 13.6% and 12.5%, respectively.

CONCLUSION

Astigmatism axis could change after combined tropicamide and phenylephrine instillation. Reference axis marking in astigmatism correction surgery should be performed under the same circumstances as the astigmatism axis has been measured.

Cycloplegic Effects on the Cylindrical Components of the Refraction

It is important to predict which astigmatic patients require separate refraction for near vision. This study compared cylindrical components changes by cyclopentolate 1% for the low and high amount of astigmatism. The right eyes of 1014 healthy individuals (307 males and 707 females) with cylindrical refractive power more than -0.5 diopter on autorefractometer were selected. Both male and female patients in the age range of 17-45 years were refracted before and after cycloplegia, using 1% cyclopentolate. All volunteers were classified into 2 subgroups including the lower astigmatism group (-2.25 to -0.50) and the higher astigmatic group (-2.50 to over). Alpines' method was used to compare the effect of cycloplegic drop on cylindrical power. The mean age in the lower astigmatism group (29.58; 95% CI: 29.18 to 29.99 years) was not significantly different from the higher astigmatic group (29.85; 95% CI: 29.07 to 30.62) and there were no significant differences in gender between these two groups (P=0.54). Differences between wet and dry refraction in J0 (-0.03; 95% CI:-0.06 to -0.008) and J45 (-0.03; 95% CI:-0.06 to -0.01) were significant only in the higher astigmatic group. Axis changes by the cycloplegic drop in the lower astigmatism group were 3.51 (CI: 3.22 to 3.81) and axis changes by the cycloplegic drop in the higher astigmatism group were 2.21 (CI: 1.73 to 2.49). In patients with a lower amount of astigmatism (-2.25 to -0.50), additional near subjective refraction could be done for precise determination of axis and in patients with a higher amount of astigmatism (-2.50 to over), near subjective refraction might be done for precise determination of power.

Refractive characteristics of keratoconus eyes with corneal Vogt's striae: A contralateral eye study

PURPOSE

The aim of this study was to assess and compare clinical characteristics of bilateral keratoconus patients with unilateral Vogt's striae.

METHODS

In this contralateral eye study, refractive status were evaluated in patients with bilateral keratoconus whose corneas had definite slit-lamp biomicroscopic evidence of unilateral Vogt's striae. All cases underwent a comprehensive ophthalmic examination. Some refractive errors components provided by autorefraction were converted to vectorial notation for power vector analysis. Finally, the outcomes were compared between keratoconus eyes with and without Vogt's striae.

RESULTS

Fifty patients aged 20 to 38 years (27.43±5.5) were recruited in this study. The results showed a significant difference in uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), non-cycloplegic and cycloplegic autorefraction including sphere, cylinder, spherical equivalent, and J₀, between keratoconus eyes with and without Vogt's striae (all P<0.05), except for J₄₅ (P=0.518 in non-cycloplegic autorefraction and P=0.574 in cycloplegic autorefraction). Comparison of cycloplegic and non-cycloplegic autorefraction in both study groups showed significant differences in the sphere and spherical equivalent (all P<0.001), but no significant difference was found in cylinder, J₀, and J₄₅ between the study groups (all P>0.05).

CONCLUSIONS

Comparison of the cycloplegic and non-cycloplegic autorefraction in keratoconus eyes with and without Vogt's striae showed significant differences in UDVA, CDVA, and some refractive errors components provided by autorefraction between the two groups, with a worse condition in KCN eyes with Vogt's striae.

Subtle changes of the crystalline lens after cycloplegia: a retrospective study

BACKGROUND

The purpose of this study was to evaluate the shape of the crystalline lens in terms of biometry and diopters before and after cycloplegia using the CASIA2 swept-source (SS) optical coherence tomography (OCT) system on the anterior segment.

METHODS

This was a retrospective study. Children and adolescents (26 males and 29 females, aged 4-21 years) with simple ametropia were selected for optometry and CASIA2 imaging at 2 separate visits before and after cycloplegia. Diopter values were derived from the spherical power (S) obtained by optometry. Biometric parameters of the crystalline lens, including the anterior chamber depth (ACD), anterior and posterior curvature of the lens (ACL and PCL), lens thickness (LTH), lens decentration (LD), lens tilt (LT), and equivalent diameter of the lens (LED), were measured by the CASIA2 system. The differences in these parameters after compared with before cycloplegia were determined, and their relationships were analyzed.

RESULTS

Fifty-five participants (106 eyes) were initially enrolled. There was a significant difference (P < 0.05) in the S (t=-7.026, P < 0.001), ACD (t=-8.796, P < 0.001), ACL (t=-13.263, P < 0.001) and LTH (t = 7.363, P < 0.001) after compared with before cycloplegia. The change in the PCL (t = 1.557, P = 0.122), LD (t = 0.876, P = 0.383), LT (t = 0.440, P = 0.661) and LED (t=-0.351, P = 0.726) was not statistically significant (P > 0.05). There was a significant (P < 0.05) correlation of the change in the S with that in the ACL (r = 0.466, P < 0.001), LTH (r=-0.592, P < 0.001), and LED (r = 0.223, P = 0.021) but not the PCL (r = 0.19, P = 0.051), LD (r=-0.048, P = 0.0628) or LT (r=-0.022, P = 0.822). Furthermore, the change in the ACD was closely related to the change in crystalline morphology. However, in children and adolescents, we found that the change in crystalline morphology was unrelated to age.

CONCLUSIONS

Changes in lens morphology after compared with before cycloplegia are mainly related to the ACL and LTH, but there is no difference in the PCL, LD, LT, or LED. In the adolescent population, change in the S is related to change in the ACL, LED and LTH. However, age is unrelated to the shape and tendency of the crystalline lens. Further research is required to determine whether the same conclusion applies to different age groups and different refractive states (myopia, hyperopia, emmetropia) .

Effect of Tropicamide on crystalline Lens rise in low-to-moderate myopic eyes

Background

Cycloplegics have been reported to induce changes in the lens thickness. However, the studies of correlation between cycloplegia and the lens position are limited. This study aims to investigate changes in crystalline lens rise (CLR) and other anterior segment parameters after inducing cycloplegia with tropicamide.

Methods

In this consecutive case study, 39 children (20 boys and 19 girls; mean age, 9.51 ± 1.75 years, mean spherical equivalence [SE], − 1.9 ± 1.5 D) with low-to moderate myopia were examined using CASIA 2 both before and after 30 min of administering 5-cycles (each 5 min apart) of 0.5% tropicamide. Measurements included CLR, crystalline lens thickness (CLT), mean radius of curvature of the anterior/posterior surface of the lens (Rf_ave/Rb_ave), anterior chamber depth (ACD), anterior chamber width (ACW), and central corneal thickness (CCT). Correlations of CLT and CLR with ACD, SE, and age were assessed respectively.

Results

CLT and CLR decreased significantly after cycloplegia (p < 0.001 and p < 0.001, respectively); whereas CCT, ACD, and Rf_ave increased (p = 0.008, p < 0.001, p < 0.001, respectively). A positive correlation was found between CLR and SE (r = 0.565, p < 0.001). However, a negative correlation between ACD and CLR was found before and after cycloplegia (r = − 0.430, p = 0.006; r = − 0.342, p = 0.035, respectively).

Conclusions

The crystalline lens appeared thinner and moved backward after cycloplegia. ACD increased mainly due to the backward movement of the crystalline lens. These results aid in elucidating the impact of crystalline lens changes during the process of accommodation.

The Effect of Topical Cyclopentolate on Anterior Segment Parameters in Patients with Keratoconus

Objectives:

To investigate the effect of cycloplegia on anterior segment structures in keratoconus and forme fruste keratoconus patients using corneal topography.

Materials and Methods:

In this study, 40 patients with keratoconus (group 1), 40 patients with forme fruste keratoconus (group 2), and 40 healthy subjects (group 3) were evaluated prospectively. Flat keratometry (K) value (K1), steep K value (K2), mean K value (Kmean), maximum K value (Kmax), corneal astigmatism value, anterior chamber depth (ACD), symmetry index front, symmetry index back, thinnest corneal thickness, central corneal thickness and corneal volume were measured using Sirius topography before and after cycloplegia. Results were compared with one way ANOVA test.

Results:

The mean age of the participants was 24.4±6.2 years for group 1, 26.3±4.3 years for group 2 and 26.5±6.1 years for group 3. There was no difference between the groups with respect to mean age and gender (p>0.05). Mean K1 value was 45.54±2.43 diopters (D) before cycloplegia and 45.46±2.48 D after cycloplegia for group 1 (p=0.044). K1 value didn’t change significantly after cycloplegia for group 2 and 3 (p=0.275, p=0.371). There was no significant difference in K2 and Kmean values after cycloplegia for all groups (p>0.05). Kmax value decreased significantly after cycloplegia in group 1 (p=0.001), but the difference was not significant for group 2 and 3 (p=0.087, p=0.241). ACD increased significantly after cycloplegia in all groups (p=0.001).

Conclusion:

Cycloplegia causes corneal flattening only in manifest keratoconus patients, leading to an increase in ACD in all groups.