Phakic posterior chamber intraocular lens for unilateral high myopic amblyopia in Chinese pediatric patients

Myopia: Mechanisms and Strategies to Slow Down Its Progression

This topical review aimed to update and clarify the behavioral, pharmacological, surgical, and optical strategies that are currently available to prevent and reduce myopia progression. Myopia is the commonest ocular abnormality; reinstated interest is associated with high and increasing prevalence, especially but not, in the Asian population and progressive nature in children. The growing global prevalence seems to be associated with both genetic and environmental factors such as spending more time indoor and using digital devices, particularly during the coronavirus disease 2019 pandemic. Various options have been assessed to prevent or reduce myopia progression in children. In this review, we assess the effects of several types of measures, including spending more time outdoor, optical interventions such as the bifocal/progressive spectacle lenses, soft bifocal/multifocal/extended depth of focus/orthokeratology contact lenses, refractive surgery, and pharmacological treatments. All these options for controlling myopia progression in children have various degrees of efficacy. Atropine, orthokeratology/peripheral defocus contact and spectacle lenses, bifocal or progressive addition spectacles, and increased outdoor activities have been associated with the highest, moderate, and lower efficacies, respectively.

Evaluation of the efficacy, safety, and stability of posterior chamber phakic intraocular lenses for correcting intractable myopic anisometropic amblyopia in a pediatric cohort

BACKGROUND

Myopic anisometropic amblyopia in pediatrics is one of the most challenging clinical situations that can face an ophthalmologist. Conventional correction modalities for myopic anisometropia, using spectacles, contact lenses, and/or occlusion therapy, may not be suitable for some pediatric patients or for some ocular conditions. This may lead to the development of anisometropic amblyopia. The aim of the present study was to evaluate the visual and the refractive efficacy, safety, and stability of Posterior Chamber Phakic Intraocular Lenses (PC-pIOLs) for correcting myopic anisometropic amblyopia in a pediatric cohort.

METHODS

This case series, prospective, interventional study was conducted at Watany Eye Hospital, Cairo, Egypt. It comprised children and teenagers with myopic anisometropic amblyopia and unsuccessful conventional therapy. After implantation of Intraocular Collamer Lenses "ICLs" (Visian ICL, Model V4c, STAAR Surgical, Monrovia, California, USA), postoperative follow-up visits were scheduled, with automated refraction and Pentacam imaging performed.

RESULTS

The study enrolled 42 eyes of 42 patients. The age range was 3 to 18 years (mean ± SD = 10.74 years ±4.16). The mean preoperative spherical equivalent (SE) was - 12.85 D ± 2.74. The results declared a significant improvement in the postoperative Corrected Distance Visual Acuity "CDVA" (P value < 0.01) and SE (P value < 0.01). The efficacy index had a value of 1.18 ± 0.3 and the safety index was 1.09 ± 0.24. The follow-up visits had a mean ± SD of 14.67 months ±16.56 (range of 1 to 54 months). The results showed a refractive stability, with statistically insignificant improvements in the patients' visual acuity and refractive status on evaluating the enrolled pediatrics during the follow-up visits compared to the first postoperative visits. No postoperative complications were encountered. Worthy of mention is that there was a significant (80%) non-compliance with the prescribed postoperative occlusion therapy.

CONCLUSIONS

The present study, with the longest reported follow-up range, declared the long-term efficacy, safety, and stability of Visian ICLs for correcting myopic anisometropic amblyopia in pediatrics. The reported non-compliance with occlusion therapy validates the early implantation of Visian ICLs in cases with failed conventional therapy to guard against anisometropic amblyopia.

Threshold Values of Myopic Anisometropia Causing Loss of Stereopsis

Purpose

The aim of the study was to determine the threshold values of myopic anisometropia that lead to the loss of stereoacuity in most of patients.

Materials and Methods

Forty healthy subjects were included in the study. The inclusion criteria were as follows: lack of any functional or morphological ophthalmological disorders, or detectable damage to the visual system, anisometropia equal or less than 0.25 D in a spherical equivalent, and full stereoscopic vision for near and for distance. Myopic anisometropia was evoked by placing different focusing lenses in front of the right eye of the subject in the trial frame. Stereoscopic vision was assessed with the use of the Titmus test (dots) (Stereo Fly Test Stereo Optical Co. Inc.) for near and the Randot test for distance (Distance Randot Stereotest Stereo Optical Co. Inc.).

Results

The threshold values for different types of myopic anisometropia for the loss of stereopsis in more than 50% of patients were determined. For near, this value was 3 D for sphere and “against the rule astigmatism” and 4 D for “with the rule astigmatism”. For distance, the values were 2 D for sphere and “against the rule astigmatism” and 3 D for “with the rule astigmatism.” Conclusions. Myopic anisometropia of more than 2 D can cause a significant impairment of binocular vision. Stereoacuity at distance is more sensitive to myopic anisometropia than stereoacuity at near. Myopic anisometropia involving “against the rule” astigmatism potentially affects binocularity more than anisometropia with regular astigmatism. A prompt correction of anisometropia of more than 2 D is needed in children to prevent the development of amblyopia.

Posterior chamber phakic intraocular lens for the correction of high myopic anisometropic amblyopia in adults

This study aims to evaluate the clinical results of posterior chamber implantable collamer lens (ICL) implantation in adults with high myopic anisometropic amblyopia. Thirteen patients aged 27.04±7.24y (range 19.2 to 42.5) were studied. ICL implantation was performed in 13 amblyopic eyes. The mean myopic anisometropia was significantly dropped from -10.70±3.02 D preoperatively to +0.09±1.67 D at 1mo postoperatively. The logMAR CDVA at 3d, 1, 3 and mean 9mo postoperatively improved by a mean of 1.69, 2.50, 3.01 and 3.00 lines and gained more than 2 lines accounted for 23.08% (3 eyes), 41.67% (5 eyes), 63.63% (7 eyes) and 55.56% (5 eyes), respectively. The contrast sensitivity of amblyopic eyes was significantly increased after surgery. Four patients partially recovered near stereopsis (400″ to 100″). There was no severe complications were observed. ICL implantation alone can improve vision, contrast sensitivity, and partial restoration of binocular vision in adult patients with high myopic anisometropia.