Peripheral Refraction and Axial Growth Rate After Multifocal or Monofocal Intraocular Lens Implantation in Chinese Pediatric Cataract Patients

Abstract

Purpose: The purpose of this study was to compare relative peripheral refraction (RPR) and axial growth in Chinese pediatric patients with cataract who underwent multifocal or monofocal intraocular lens (IOL) implantation.

Methods: Pediatric patients with cataract aged 3 to 6 years who underwent IOL implantation from 2020 to 2021 were enrolled in this study. The patients received multifocal or monofocal IOL implantations with optic capture in Berger's space. The axial length (AL) was measured with a Zeiss IOL Master 700, and autorefraction at the horizontal retina within 30 degrees eccentricities was recorded with a Grand Seiko WAM-5500 autorefractor. The RPR was calculated by subtracting the central refraction from the peripheral refraction. The axial growth rate was calculated as the change in the AL divided by the number of follow-up years.

Results: Twenty-six children (38 eyes) implanted with multifocal IOLs and 19 children (30 eyes) implanted with monofocal IOLs completed the study. No significant differences were observed in preoperative characteristics between the two groups (P > 0.05). The generalized estimating equation (GEE) model revealed that the axial growth rate was significantly associated with the IOL type (P = 0.049) after adjusting for surgical age and follow-up intervals, with multifocal IOL eyes showing lower annual growth rate than monofocal IOL eyes. Additionally, compared with monofocal IOL eyes, multifocal IOL eyes exhibited greater peripheral myopic defocus at 20 degrees and 30 degrees on the temporal retina (P < 0.001 and P = 0.005, respectively). The GEE model also revealed a positive correlation between the annual axial growth rate and the 20 degrees temporal retina RPR (P = 0.018).

Conclusions: Chinese pediatric patients with cataract who underwent multifocal IOL implantation exhibited less axial growth, potentially caused by greater peripheral myopic defocus.

Cataracts are a common cause of blindness in children, with an annual incidence rate of approximately 1.8 to 3.6 of 10,000.¹ Implanting monofocal intraocular lenses (IOLs) is the standard of care for pediatric cataract surgery; however, this type of IOLs cannot provide clear distance and near visual acuity (VA) simultaneously. This limitation can lead to significant anisometropia in children with unilateral cataracts, which affects visual function.² An increasing number of studies^3–5 have demonstrated that the use of multifocal IOLs in children is safe and effective from the perspective of postoperative VA and visual function reconstruction. Unfortunately, the above studies did not explore postoperative eye development; however, solving postoperative ametropia and restoring postoperative VA are both key clinical focuses and challenges. Our early prospective study compared the postoperative axial development of another group of pediatric patients with unilateral cataract⁶ and first proposed that multifocal IOL implantation may be a protective factor against excessive axial growth; however, further research on the possible mechanism by which multifocal IOLs slow axial elongation is lacking. 

Myopia is an epidemic and is predicted to affect approximately 50% of the world's population by 2050 unless new strategies to fight myopia are developed.⁷ The etiology of myopia has been linked to interactions among multiple environmental and genetic risk factors, including education, limited time outdoors, and parental myopia as major risk factors.⁸ Previous treatments for controlling myopia progression were based on reducing foveal hyperopic defocus because a rapid increase in axial length (AL) can be observed after exposure to hyperopic defocus.⁹ However, the foveal area forms only a small part of the eye; the peripheral refraction of the greater peripheral retinal areas plays an important role in eyeball development.^10,11 In the field of myopia prevention and control, peripheral myopic defocus has been shown to potentially inhibit axial elongation in humans.¹¹ In addition, peripheral myopic defocus is typically created by optical-based treatments, such as peripheral positive refractive spectacles,^12,13 multifocal contact lenses,^14,15 and orthokeratology lenses.¹⁶ On the basis of the above reports, additional positive refraction around multifocal IOLs theoretically generates peripheral myopic defocus and myopia control effects. 

In this study, we first comprehensively evaluated peripheral refraction, astigmatism, and postoperative axial growth in pediatric patients with cataract. In addition, patients who were implanted with multifocal and monofocal IOLs were compared. 

Methods

Study Design and Population

Fifty Chinese pediatric patients with cataract aged 3 to 6 years old who underwent cataract surgery and IOL implantation were enrolled in this prospective study between July 6, 2020, and August 2, 2021. The study adhered to the principles of the Helsinki Declaration. All the families were informed of the treatment plan before surgery and provided written informed consent. The study was approved by the Ethics Committee of the Qingdao Eye Hospital of Shandong First Medical University (No. 2019(25)) and registered with the Chinese Clinical Trial Registry (ChiCTR identifier: 1900023155). 

Patients were distinguished based on the type of IOL selected jointly by doctors and patients’ families: 28 patients (15 patients with unilateral cataract and 13 patients with bilateral cataract) had multifocal IOL implantation, and 22 patients (9 patients with unilateral cataract and 13 patients with bilateral cataract) had monofocal IOL implantation. None of the participants had systemic diseases, a history of ocular trauma or corneal surgery, ocular structural abnormalities, severe uveitis, severe retinal disease, pupil adhesion, or secondary glaucoma.³ To reduce confounding factors that may affect eye development, such as poor VA or additional surgery is needed to clear the visual axis.¹⁷ Patients whose best-corrected distance visual acuity (BCDVA, 5 m) was better than 0.3 LogMAR at the last follow-up and without complications, such as posterior capsular opacification or glaucoma throughout the entire follow-up period were eligible for analysis. 

Preoperative Examination

A complete ophthalmological examination, including VA, intraocular pressure measurement, slit‒lamp microscopy, and fundus evaluation of both eyes, was performed before surgery.³ All participants’ eyes were dilated with 3 drops of 0.5% tropicamide, with each drop instilled at 5-minute intervals to achieve maximum pupillary dilation and cycloplegia. Refractive error measurements were performed 30 minutes after instillation of the third drop, using a NIDEK ARK-1 (Nidek Co., Ltd., Aichi, Japan), and the average of 6 measurements was used for the analysis. The AL and corneal curvature were measured using an IOL Master 700 (Carl Zeiss Meditec, Jena, Germany), and the average of 6 measurements was calculated. The AL was measured in the same manner after surgery. 

The Hoffer Q and Holladay 2 formulas were used to calculate IOL power when patients had shorter ALs (≤22.00 mm) or steeper corneas (>43.50 diopters [D]), and the Holladay, Hoffer Q, and Barrett Universal II formulas were used when the AL was greater than 22.00 mm or the corneal curvature was 43.50 D or less.¹⁸ We chose +0.50 D for the refractive target for subjects whose AL was 23.50 mm or longer and +0.75 to +2.50 D for the refractive target for subjects whose AL was shorter than 23.50 mm. 

IOLs and Surgical Technique

The monofocal iSert 251 (Hoya Corp., Japan) is an acrylic, hydrophobic, aspherical lens with a negative spherical aberration of 0.18 µm. The multifocal Tecnis ZMB00 (Johnson & Johnson Vision, USA) features acrylic optics measuring 6.0 mm in diameter, a negative spherical aberration of 0.27 µm, and a +4.00 D near addition outside the optical zone at the IOL plane. 

Cataract surgery and IOL implantation were performed by a single experienced cataract surgeon (author Y.S.H.) under a Lumera 700 (Carl Zeiss OPMI) surgical microscope, as previously described.³ Briefly, a 2.2-mm limbal incision was made while the patient was under general anesthesia. After 5.5 mm, anterior continuous curvilinear capsulorhexis (ACCC) was performed, and the lens was removed via aspiration. After an IOL was placed in the capsular bag, a posterior continuous curvilinear capsulorhexis (PCCC) was created. A lens hook was used to push the IOL to slide posteriorly through the opening with the haptics in the capsular bag to achieve optic capture. 

Postoperative Treatment and Measurements

Occlusion therapy was started within 1 week after cataract surgery, and patching was prescribed for patients with amblyopia. The patching dose ranged between 2 and 6 hours daily, depending on the patient's postoperative BCDVA.⁴ 

One month after surgery, autorefraction and subjective refraction without cycloplegia were measured, and refractive correction was prescribed. Patients with implanted multifocal IOLs typically need only one pair of single-vision glasses to correct the reserved hyperopia, whereas patients with monofocal IOLs typically need two pairs of glasses or bifocal glasses to correct distance and near VA. 

Central and peripheral refractions were measured using a WAM-5500 open-field autorefractor (Grand Seiko Co., Hiroshima, Japan) in all patients without cycloplegia 1 month after surgery. The subjects focused on Maltese crosses placed as the central and peripheral targets at eccentricities along the horizontal meridians (10 degrees, 20 degrees, and 30 degrees temporally and nasally) in the subject’s visual location at eye level on a flat wall located 5 m from the eye. The participants were instructed to turn the eye only for the peripheral refraction measurements by keeping their head fixed in the head-chinrest of the autorefractor. This method was adopted because no differences were reported in peripheral refraction measurements due to eye or head turning.¹⁹ All the measurements were recorded by aligning the focused measuring circle to the approximate geometrical center of the pupil, as shown through the video display of the autorefractor. Five measurements were obtained at the central retinal eccentricity and at each peripheral retinal eccentricity, and the average was considered the absolute refraction. The measurements were repeated if the sphere or cylinder power measurement varied by >0.50 D. 

VA was assessed using the Snellen chart by the same optometrist. BCDVA, distance-corrected intermediate visual acuity (DCIVA; 66 cm), distance-corrected near visual acuity (DCNVA; 33 cm), and the best-corrected near visual acuity (BCNVA; 33 cm, LogMAR) of monofocal IOL eyes were recorded (patients implanted with multifocal IOLs did not require near-spectacle correction and BCNVA was not measured). Stereoscopic vision was assessed using Titmus stereotest cards while the eyes were dissociated optically with polarized glasses measured in seconds of an arc at a distance of 0.4 m (under near-spectacle correction for monofocal IOL eyes). The contrast sensitivity (CS) of the eye was tested using the Mars Letter Contrast Sensitivity Test (Mars Perceptrix, Chappaqua, NY) at a distance of 0.4 m (under near-spectacle correction for monofocal IOL eyes). 

Definitions

The spherical equivalent refraction (M) was defined as the sphere plus one-half of the cylinder. The spherical power (S), cylindrical power (C), and axial power (θ) were calculated. The relative peripheral refraction (RPR) was calculated for each retinal eccentricity by subtracting the central region from the peripheral M measurements (peripheral M-central M). The J₀ (C at orthogonal 90 degrees and 180 degrees meridians) was −(C/2)cos(2θ), and the J₄₅ (C at 45 degrees and 135 degrees meridians) was −(C/2)sin(2θ).²⁰ For the RPR, positive values indicate relative peripheral hyperopic defocus, whereas negative values indicate relative peripheral myopic defocus. Positive values for eccentricity refer to the temporal retina location (toward the fovea from the optic disc), and negative values indicate the nasal retinal location (toward the optic disc from the fovea). The annual axial growth rate was calculated as the change in AL divided by the number of follow-up years (the follow-up months divided by 12). 

Statistical Analysis

All statistical analyses were performed using IBM SPSS Statistics software (IBM Corp., Armonk, NY, USA). The Kolmogorov‒Smirnov test was used to assess the normality of the data distributions. Data are presented as the means ± SDs or medians (interquartile ranges [IQRs]) according to their normality. Categorical variables, such as the percentages of patients within different ranges of stereoacuity, were expressed as percentages (%). 

Data from both eyes were analyzed by using a generalized estimating equation (GEE) model to account for the potential correlation between the eyes. The GEE model was used to assess the potential associations among the axial growth rate, refractive parameters, visual functions, and the type of the implanted IOL (monofocal IOL versus multifocal IOL). The surgical age and the follow-up interval were included as covariates for both the axial growth rate and visual functions. Comparison of other continuous variables between the two groups was conducted via either an independent samples t-test or the Mann-Whitney U test, depending on the normality of the data distribution. A paired t-test was used to compare the cataract eyes and healthy fellow eyes in patients with unilateral cataract. The correlation between the axial growth rate and RPR was analyzed by using the GEE model. P < 0.05 was considered to indicate statistical significance. 

Results

Among the enrolled patients, 5 patients were excluded, including 2 patients with multifocal IOL and 1 patient with monofocal IOL with a BCDVA below 0.3 LogMAR, 1 patient with monofocal IOL who was lost to follow-up, and 1 patient with monofocal IOL who was diagnosed with posterior capsular opacification 1 year after surgery. Among the 45 eligible patients, 26 (38 eyes) patients underwent implantation of multifocal IOLs, 14 had unilateral cataracts, 12 had bilateral cataracts, 19 (30 eyes) patients underwent implantation of monofocal IOLs, 8 had unilateral cataracts, and 11 had bilateral cataracts. 

No differences in the preoperative characteristics were noted between patients who received monofocal or multifocal IOLs (P > 0.05; Table 1). There were no differences in the demographic or clinical characteristics of the unilateral cataract participants (Table 2). 

Table 1.

 

The Demographic and Clinical Characteristics of the Participants

 

Table 2.

 

The Demographic and Clinical Characteristics of the Unilateral Cataract Participants

 

According to the GEE model, the axial growth rate in pediatric cataract eyes was significantly associated with the IOL type after adjusting for surgical age and follow-up intervals (P = 0.049). Compared with monofocal IOL eyes, multifocal IOLs eyes presented a significantly lower annual growth rate (0.10 ± 0.09 mm/year versus 0.15 ± 0.08 mm/year; Fig. 1). 

Figure 1.

 

Boxplots demonstrating the difference in the annual growth rate between eyes with multifocal IOL implantation and those with monofocal IOL implantation. Error bars = minimum to maximum. The horizontal line indicate the group median. Every point represents one data point. Level of significance = *P < 0.05; a generalized estimating equation model adjusted for surgical age and follow-up intervals.

All the IOL-implanted eyes presented a greater negative shift in the temporal retina location than in the nasal retina location. The GEE model results showed that the RPR values at temporal 20 degrees and 30 degrees were significantly correlated with the type of the implanted IOL (P < 0.001 and P = 0.005, respectively), with greater myopic defocus of the temporal location noted in the eyes implanted with multifocal IOLs (Fig. 2A). Table 3 shows a significant positive correlation between the axial growth rate and the 20 degrees temporal retinal RPR (P = 0.018). For peripheral astigmatism, the GEE model showed no significant association between the peripheral J₀ and the type of the implanted IOL (P > 0.05; Fig. 2B), but the eyes implanted with multifocal IOLs presented greater negative astigmatic defocus at the J₄₅ plane in the retinally nasal 30 degrees region than those implanted with monofocal IOLs (P = 0.015; Fig. 2C). 

Figure 2.

 

Comparison of the relative peripheral refraction along the horizontal retinal location between eyes implanted with multifocal IOLs and those implanted with monofocal IOLs. (A) The Y axis shows the mean relative peripheral M, which is equal to the peripheral M-central M. The spherical equivalent refraction (M) was defined as the sphere plus one-half of the cylinder. (B) The Y-axis shows the mean relative peripheral J₀, where J₀ is the cylindrical power at orthogonal 90 degrees and 180 degrees meridians. (C) The Y-axis shows the mean relative peripheral J₄₅, where J₄₅ indicates cylindrical power at the 45 degrees and 135 degrees meridians. Definition = For the RPR, positive values indicate relative peripheral hyperopic defocus, whereas negative values indicate relative peripheral myopic defocus. Positive values for eccentricity refer to the temporal retina location (toward the fovea from the optic disc), and negative values indicate the nasal retinal location (toward the optic disc from the fovea). Error bars = SE. Levels of significance = *P < 0.05, **P < 0.01, and ***P < 0.001, a generalized estimating equation model.

Table 3.

 

GEE Model Results for Relative Peripheral Refraction for Each Eccentric Retinal Location Associated With the Axial Growth Rate

 

Axial growth rates and RPRs were compared between cataract eyes and healthy fellow eyes in patients with unilateral cataract (Fig. 3). Compared with healthy fellow eyes, multifocal IOL eyes presented a lower growth rate (0.11 ± 0.09 mm/year versus 0.17 ± 0.06 mm/year, P = 0.045; see Fig. 3A) and more peripheral myopic defocus at the 30 degrees temporal retina RPR (–1.28 ± 0.90 D vs. –0.61 ± 0.49 D, P = 0.027; see Fig. 3B). However, there were no significant differences in the eye growth or the RPR between the eyes implanted with monofocal IOLs and the healthy fellow eyes (see Figs. 3C, 3D). 

Figure 3.

 

Annual growth rate and relative peripheral refraction in cataract eyes and healthy fellow eyes of patients with unilateral cataract. (A) Annual growth rate in cataract eyes implanted with multifocal IOLs and in healthy fellow eyes. (B) Relative peripheral refraction in cataract eyes implanted with multifocal IOLs and in healthy fellow eyes. (C) Annual growth rate in cataract eyes implanted with monofocal IOLs and in healthy fellow eyes. (D) Relative peripheral refraction in cataract eyes implanted with monofocal IOLs and in healthy fellow eyes. Definition = For the RPR, positive values indicate relative peripheral hyperopic defocus, whereas negative values indicate relative peripheral myopic defocus. Positive values for eccentricity refer to the temporal retina location (toward the fovea from the optic disc), and negative values indicate the nasal retinal location (toward the optic disc from the fovea). Error bars = Minimum to maximum (A, C). The horizontal line indicates the group median. Every point represents one data point. Error bars = SE (B, D).

The GEE model analysis, after adjusting for surgical age and follow-up intervals, showed that the BCDVA and BCNVA at the last follow-up were not significantly associated with the IOL type (P > 0.05). However, both DCIVA and DCNVA were significantly associated with the IOL type, with multifocal IOL patients demonstrating better VA (0.32 ± 0.11 vs. 0.40 ± 0.16 LogMAR, P = 0.024 and 0.22 [0.15 to 0.30] vs. 0.52 [0.40 to 0.70] LogMAR, P < 0.001; Fig. 4A). Additionally, the patients implanted with both types of IOLs showed no significant differences in the CS and stereopsis test results (Figs. 4B, 4C). 

Figure 4.

 

Differences in visual function at the last follow-up after implantation of the multifocal and monofocal IOLs. (A) Visual acuity at distance, middle, and near for eyes implanted with multifocal and monofocal intraocular lenses (BCDVA, best-corrected distance visual acuity; DCIVA, distance-corrected intermediate visual acuity; DCNVA, distance-corrected near visual acuity; BCNVA, best-corrected near visual acuity). (B) Contrast sensitivity between eyes implanted with multifocal and monofocal IOLs. (C) Percentage of patients with stereoacuity after multifocal and monofocal intraocular lens implantation. Annotation: (A) BCNVA, comparison between the best-corrected near visual acuity of eyes with monofocal IOL implantation and the distance-corrected near visual acuity of eyes with multifocal IOL implantation. Error bars = SE. Levels of significance = *P < 0.05 and ***P < 0.001, a generalized estimating equation model adjusted for surgical age and follow-up intervals.

Compared with multifocal IOL eyes, healthy fellow eyes had better BCDVA (0.02 ± 0.04 vs. 0.12 ± 0.08 LogMAR, P = 0.001), DCIVA (0.05 ± 0.06 vs. 0.33 ± 0.12 LogMAR, P < 0.001), DCNVA (0.01 ± 0.02 vs. 0.21 ± 0.09 LogMAR, P <0.001; Fig. 5A), and CS (1.53 ± 0.09 vs. 1.37 ± 0.13, P < 0.000; Fig. 5B). Compared with the monofocal IOL eyes, the healthy fellow eyes also had better BCDVA (0.02 ± 0.02 vs. 0.10 ± 0.07 LogMAR, P = 0.005), DCIVA (0.04 ± 0.04 vs. 0.39 ± 0.16 LogMAR, P = 0.001), DCNVA (0.00 [0.00 to 0.02] vs. 0.52 [0.40 to 0.52] LogMAR; P < 0.001), BCNVA (0.00 [0.00 to 0.02] vs. 0.17 ± 0.09 LogMAR, P = 0.002; Fig. 5C), and CS (1.54 [1.48 to 1.60] vs. 1.39 ± 0.13, P = 0.008; Fig. 5D). 

Figure 5.

 

The visual function of cataract eyes and healthy fellow eyes in patients with unilateral cataract was compared at the last follow-up. (A) Visual acuity at distance, middle, and near for eyes implanted with multifocal IOLs and their healthy fellow eyes. BCDVA, best-corrected distance visual acuity; DCIVA, distance-corrected intermediate visual acuity; DCNVA, distance-corrected near visual acuity. (B) Contrast sensitivity between eyes with multifocal IOL implantation and their healthy fellow eyes. (C) Visual acuity at distance, middle, and near for eyes implanted with monofocal IOLs and their healthy fellow eyes. BCDVA, best-corrected distance visual acuity; DCIVA, distance-corrected intermediate visual acuity; DCNVA, distance-corrected near visual acuity; BCNVA, best-corrected near visual acuity. (D) Contrast sensitivity between eyes implanted with monofocal IOLs and their healthy fellow eyes. Annotation: (C) BCNVA, comparison between the best-corrected near visual acuity of eyes with monofocal IOL implantation and the distance-corrected near visual acuity of the healthy fellow eyes. Error bars = SE. Levels of significance = **P < 0.01 and ***P < 0.001 for a paired t-test.

Discussion

The process and control of axial growth after pediatric cataract surgery are complex and incompletely understood, and the duration of vision deprivation, age at surgery, ethnicity, laterality, and complications²¹ may affect postoperative axial growth. The present study revealed that the differences in the power profiles between IOL designs are reflected in peripheral refraction and axial growth after lenses are implanted into Chinese pediatric patients with cataract. Compared with monofocal IOL eyes, eyes implanted with multifocal IOLs have less axial growth. Moreover, the positive correlation between temporal retina RPR and axial changes suggests that the lower axial growth rate of multifocal IOL eyes may be attributed to greater peripheral negative refraction. 

The differences in axial growth between multifocal and monofocal IOL eyes may be explained by central and peripheral refraction. We provided hyperopic spectacles for pediatric patients with cataract 1 month after surgery to correct central hyperopic defocus as soon as possible. However, some patients who undergo monofocal IOL implantation exhibit low utilization of the near location when wearing bifocal glasses²² or low compliance when wearing two pairs of glasses, which increases the incidence of hyperopic defocus in cataract eyes⁶ and may be one of the reasons for the faster annual growth rate. On the other hand, the positive correlation between the retinal temporal RPR and axial changes (see Table 3) further revealed that the eyes implanted with multifocal IOLs implantation presented more peripheral negative shifts at 20 degrees and 30 degrees in the temporal location of the retina (see Fig. 2), which was associated with less axial growth. Compared with monofocal IOL implantation, multifocal IOL implantation potentially leads to less myopic shift, therefore, the hyperopic refractive targets should be appropriately reduced in pediatric patients with cataract. 

Insufficient or excessive postoperative axial growth can always be observed in clinical practice. When axial growth is less than expected, patients may need to wear hyperopic correction glasses for an extended period,²³ which could prevent them from achieving spectacle independence with multifocal IOLs. Excessive axial growth can result in significant myopia at long-term follow-up^24,25 and may even increase the risk of retinal detachment caused by increasing AL,²⁶ these effects are clearly more unfavorable to the long-term visual development of children’s eyes. Given that myopia control in children has become a global issue,⁸ cataract doctors should take the prevention and control of myopia in both cataractous and healthy fellow eyes of pediatric patients with cataract seriously. 

Guo et al.²⁷ reported that the axial elongation in Chinese preschoolers was 0.14 mm/year from 3 to 6 years of age. The growth rate was similar to that of the patients who underwent monofocal IOL implantation in our study (0.15 mm/year). Our results revealed no statistically significant difference in axial growth between eyes with monofocal IOLs and healthy fellow eyes in pediatric patients with unilateral cataract, nor was there a difference in the RPR (see Figs. 3C, 3D). These findings suggest that the implantation of monofocal IOLs may not alter eye development in children.^17,28,29 Notably, the multifocal IOL eyes presented slower axial growth than the healthy fellow eyes (see Fig. 3A), which validates the results of our other study on patients with unilateral cataract⁶; we found that this difference may be related to the more negative RPR in multifocal IOL eyes. Additionally, the annual growth rate of multifocal IOL eyes was lower than that reported by the Guo et al.²⁷ study. These results provide some evidence that multifocal IOLs are potentially valuable for myopia control in pediatric patients with cataract. 

Simth et al.³⁰ demonstrated through animal experiments that there is a correlation between signals from the periphery and axial growth of the eye, which may dominate overall axial growth. The present study validated the positive correlation between the RPR and axial growth rate in pediatric cataract IOL eyes and proposed that one of the reasons for the relatively slow axial growth of multifocal IOL eyes is their greater peripheral myopic defocus. Similar conclusions were also drawn by Jakobsen et al.,³¹ who reported that the orthokeratology lenses with myopia prevention and control effects were positively correlated between baseline peripheral refraction and axial growth. Although it is unknown whether the relationship between peripheral defocus and myopia progression is causal or simultaneous, there is growing evidence that peripheral myopic defocus may be an effective inhibitor of axial elongation in humans.³² 

Temporal retinal signals may play a dominant role in controlling axial growth in patients with myopia.³³ The optic disc in the nasal retina, as an anatomic constraint and asymmetrical difference in retinal ganglion density, represents a potential factor that makes the temporal retina more important for axial growth than the nasal retina.³⁰ The positive correlation between the RPR of the temporal retina and axial changes in our study confirms the above conclusion. However, our results revealed that the correlation was greater at 20 degrees temporal retina eccentricity than at more central or peripheral retinal locations. Whereas Panorgias et al.³⁴ suggest that a retinal location between 6 and 12 degrees is more sensitive to optical blur. Although peripheral myopic defocus has been demonstrated to be a potent trigger for decreasing myopia progression, the level of defocus and the degree to which retinal eccentricity influences eye growth remain inconclusive and warrant further exploration. 

We studied peripheral refraction and peripheral astigmatism defocus along the J₀ and J₄₅ planes in patients who underwent implantation with the two types of IOLs and compared their postoperative visual function, as previous studies have reported that excessive peripheral defocus, especially off-axis astigmatism, may have performance and safety implications for activities requiring good peripheral vision³⁵ and may even cause a significant reduction in contrast detection sensitivity.³⁶ In agreement with the findings of a previous study,⁵ our results revealed that CS and stereoacuity were similar in pediatric patients with cataract after monofocal or multifocal IOL implantation (see Figs. 4B, 4C), which may be related to the similar BCDVA and BCNVA after the implantation of the two types of IOLs (see Fig. 4A). From the perspective of peripheral refraction, the maximum difference in the RPR of 0.56 D and 0.50 D in the relative peripheral astigmatism (see Fig. 2) may not be sufficient to cause differences in visual function. Notably, multifocal IOL eyes have better DCIVA and DCNVA (see Fig. 4A), suggesting that multifocal IOLs have advantages in spectacle independence.³⁷ However, compared with those of healthy fellow eyes, the CS and VA remain relatively low in IOL eyes (see Fig. 5). Restoring postoperative VA and enhancing the optical performance of the IOL to match that of healthy eyes remains a significant challenge. 

The current study has several limitations that should be acknowledged. Given that this is the first study to link the IOL peripheral defocus with eye development in pediatric patients with cataract, no other peer-reviewed literature is available for reference. In addition, we did not measure the RPR across the vertical meridian or ocular aberrations after the IOL implantation. However, these factors may also be related to the development of eye growth, and we will explore this topic in the future. Finally, the small sample size increases the risk of type I error where the null hypothesis is rejected when it in fact is true. This increases potential bias and may affect the generalizability of the results. Further multicenter, large-sample studies are needed to verify the impact of monofocal or multifocal IOL implantation on the optical parameters of pediatric patients with cataract and explore the mechanisms by which multifocal IOLs delay axial growth. 

In conclusion, our findings reveal the possible role of multifocal IOLs with retinal peripheral myopic defocus in the horizontal direction. Pediatric patients with cataract receiving multifocal IOLs exhibit a reduced axial growth rate compared with patients receiving monofocal IOLs; this reduction may be attributed to greater peripheral myopic defocus in multifocal IOL eyes. Compared with monofocal IOLs, when multifocal IOLs are implanted in pediatric patients with cataract, relatively fewer hyperopic refractive targets should be preserved. However, the precise value needs to be determined through further large-sample multicenter clinical studies. 

Acknowledgments

Supported by the National Natural Science Foundation of China, Grant/Award Numbers: 82171027; and The Taishan Scholar Program, Grant/Award Number: ts20190983. 

Disclosure: Q. Du, None; Y. Zhang, None; Y. Huang, None