This study investigated preoperative CCT in eyes diagnosed with congenital cataracts and compared it with eyes without intraocular disease (control group). The findings indicated no significant differences in CCT between the operated and fellow eyes in unilateral cataracts or between bilateral and unilateral cataracts. However, when cataracts were categorized according to morphology, the others group showed significantly thicker CCT than did the control group. Additionally, postoperative CCT measurements were higher than preoperative measurements. The lack of significant differences in CCT between bilateral and unilateral cataracts suggests that the presence of a cataract in one or both eyes does not inherently influence corneal thickness. This finding aligns with the results of previous studies [13, 14] that have shown similar CCT measurements in various congenital cataract presentations, indicating that cataract presence alone may not be a determining factor for CCT changes. Similarly, the absence of significant CCT differences between the operated and fellow eyes with unilateral cataracts indicates that unilateral congenital cataracts do not cause specific changes in corneal thickness.

Notably, preoperative CCT was significantly higher in the others group when comparing different cataract morphologies in this study, raising questions about the underlying causes. Both the crystalline lens and cornea follow a similar course of development during embryogenesis; the epithelial cells of the cornea and crystalline lens are derived from the epidermal ectoderm. The lens vesicle separates from the surface ectoderm during the fifth week of gestation, the primitive corneal epithelium develops by the sixth week, and the migration of the neural crest cell-derived mesenchyme forms the corneal endothelium and stroma in the seventh week [15]. Lens opacity develops after the separation of the lens vesicle. While cataracts with anterior, posterior, and nuclear morphology result from some etiological effect on the lens during its development, this factor may not have a great effect on the development of the cornea. In this study, the others group, which included lamellar, cortical, and pulverulent cataracts, had greater CCT than did the control group. We suspect that these other cataracts had some effects on both the cornea and crystalline lens during the lens vesicle separation. Given the limited sample size within each subtype of the others category, we were unable to determine whether a particular morphology drove the overall increase in CCT; larger studies are required to clarify this point. The CCT in children has been reported to gradually increase with age, reaching adult levels by 5–6 years of age [16]. However, our study revealed that the CCT in pediatric patients with congenital cataracts was inversely proportional to age. This finding suggests that the corneas of children with congenital cataracts may not undergo normal developmental processes. In other words, although the precise reasons and mechanisms remain unclear, it may be suggested that the development of cataracts may influence corneal development. Considering that congenital cataracts are associated with complications such as glaucoma, it can be hypothesized that congenital cataracts affect the development of the anterior chamber angle and, by extension, the overall development of the eye. Additionally, when compared to the control group, the cataract groups tended to have thicker corneas, which is likely due to the younger age of the patients (Table 1). However, in a subset of cataract eyes within the same age range as the control group (51–96 months, n = 24), the mean CCT was 509 ± 50.2 (range, 327–570) µm, showing a tendency to be thinner compared to the control group (P = 0.070, t-test). Further research is necessary to elucidate the exact mechanisms underlying these observations. Although the others morphology group showed a significantly thicker cornea than the control group on univariate analysis, the multivariable model revealed only a non-significant tendency toward increased thickness after adjustment for age and other covariates (+ 26 µm, P = 0.108). This attenuation suggests that part of the unadjusted difference may be attributable to the younger age distribution of this subgroup. Nevertheless, the persistent upward trend keeps open the possibility that specific others-type variants influence corneal development. The clinical relevance of such a difference remains uncertain, and larger, age-matched studies are required to clarify whether any specific subtype within the others category exerts a meaningful effect on corneal thickness.

As in our study, previous reports have consistently found increased postoperative CCT compared with preoperative measurements [10,11,12]. In our study, the mean postoperative CCT increase was 9.5 µm overall (Table 5); when stratified by cataract morphology, a significant change was detected only in the others group, whereas anterior and posterior types showed a tendency toward increase that was not statistically significant. Given that postoperative CCT was measured, on average, 64 months after surgery, part of this thickening may reflect normal age-related corneal growth rather than a purely surgical effect. However, a prospective cohort study with a larger sample size has confirmed this trend [17], further supporting the generalizability of our findings. Possible explanations for this increase include surgical trauma, postoperative inflammation, and changes in endothelial cell function, but the etiology is still unclear [18,19,20]. Although we found that CECD reduced after cataract surgery, this is considered to be within the range of age-related decrease in CECD [21, 22], and an increase in corneal thickness due to changes in endothelial cell function can be ruled out. The surgical intervention itself, including the implantation of intraocular lenses and the potential for corneal edema, likely contributed to the observed thickening [23]. Monitoring CCT postoperatively is critical for managing potential complications, such as elevated intraocular pressure, and for achieving visual outcomes.

Our study has some limitations. First, the retrospective nature of this study might have introduced selection bias, and the sample size, although sufficient for initial observations, may limit the generalizability of the findings. Second, the use of different instruments (specular microscope and ultrasound pachymeter) for CCT measurements, depending on patient cooperation, might have introduced measurement variability. A specular microscope and an ultrasound pachymeter were used to measure the distance between the anterior and posterior corneal surfaces. Unlike the optical reflex used by the specular microscope, ultrasound pachymetry relies on an acoustic reflection, and the exact posterior reflex point may lie between Descemet’s membrane and the anterior chamber [24, 25]. Some variability in the measurements was observed due to body movement in children [26], but this was considered to be within an acceptable margin of error. Additionally, while excluding patients with coexisting ocular conditions is necessary to isolate the effects of congenital cataracts, it may not allow the application of the findings to a broader patient population with multiple comorbidities. Future studies should include larger cohorts and prospective designs to confirm these findings and explore the mechanisms underlying the observed CCT variations. In addition, the relationship between corneal thickness and corneal diameter should be investigated as it could provide additional insights into the structural characteristics of the cornea in congenital cataracts.

In conclusion, this study showed that congenital cataracts of specific types such as lamellar, cortical, and pulverulent, affect CCT. Notably, preoperative CCT decreased with age. Additionally, the postoperative increase in CCT was not correlated with a decrease in CECD. These findings could help comprehensively understand congenital cataracts. Continued research in this area is essential to further elucidate the factors affecting CCT.