Retinal hemorrhages and damages from tractional forces associated with infantile abusive head trauma evaluated by wide-field fundus photography.

We evaluated the distribution and types of retinal hemorrhages (RHs) and other damages in eyes with abusive head trauma (AHT). This retrospective, consecutive case series of AHT and non-AHT conditions involved 54 children with AHT, 43 children with head bruises, and 49 children with blunt eye trauma, each of non-AHT supported by reliable witness accounts. RHs and other damage were evaluated using ophthalmoscopy and wide-field fundus photography. A variety of RH types and other damage were identified in the AHT group but not in the non-AHT group. RHs in AHT extended from the posterior pole to the far periphery in 77% of eyes and on/near the veins in 86% and arteries in 85%, most of which were in the far periphery. Retinoschisis, white-dot lesions, and retinal folds were seen even in the far periphery. RHs on/near the veins and arteries, retinoschisis, and retinal folds suggest a traumatic mechanism of the tractional force of the vitreous that is attached to the entire retinal surface. Identifying the distribution and arterio and venous origins of RHs is a key factor in determining the association with trauma. Thus, wide-field fundus photography is useful to record and evaluate the origin of the RHs and other retinal damage.

Ten-year outcomes of congenital cataract surgery performed within the first 6 months of life.

PURPOSE: In the spectrum of pediatric cataract, genuine congenital cataract poses challenges and has a poorer prognosis than developmental cataract. We investigated the long-term outcomes of congenital cataract surgery performed within the first 6 months of life. SETTING: Eleven ophthalmic surgical sites in Japan. METHODS: Medical charts were retrospectively reviewed for 216 eyes of 121 patients. The age at surgery was 2.9 ± 1.7 months, with follow-up duration 13.0 ± 2.3 years. The cohort consisted of 83 cases with bilateral aphakia, 12 with bilateral pseudophakia, 20 with unilateral aphakia, and 6 with unilateral pseudophakia. RESULTS: Surgical intervention within the critical period of visual system development (10 weeks for bilateral and 6 weeks for unilateral cases) led to significantly better final visual acuity than surgery conducted after this timeframe. The incidence of secondary glaucoma was similar between groups, while the occurrence of visual axis opacification was more frequent with earlier surgery. A forward stepwise multiple regression analysis revealed that the final visual acuity was significantly associated with laterality of cataract (better outcomes in bilateral cases), phakic status (with pseudophakia outperforming aphakia), presence of systemic and ocular comorbidities, and development of secondary glaucoma. Secondary glaucoma was significantly more prevalent in aphakic eyes than pseudophakic eyes. CONCLUSIONS: In patients with genuine congenital cataract, surgery within the critical period of visual development results in better final visual acuity, albeit with an increased risk of visual axis opacification. The use of intraocular lens with sophisticated surgical techniques shows promise even in congenital cataract surgery.

Modeling of Retina and Optic Nerve Ischemia-Reperfusion Injury through Hypoxia-Reoxygenation in Human Induced Pluripotent Stem Cell-Derived Retinal Ganglion Cells.

Retinal ganglion cells (RGCs) are specialized projection neurons that constitute part of the retina, and the death of RGCs causes various eye diseases, but the mechanism of RGC death is still unclear. Here, we induced cell death in human induced pluripotent stem cell (hiPSC)-derived RGC-rich retinal tissues using hypoxia-reoxygenation in vitro. Flow cytometry, immunochemistry, and Western blotting showed the apoptosis and necrosis of RGCs under hypoxia-reoxygenation, and they were rescued by an apoptosis inhibitor but not by a necrosis inhibitor. This revealed that the cell death induced in our model was mainly due to apoptosis. To our knowledge, this is the first model to reproduce ischemia-reperfusion in hiPSC-derived RGCs. Thus, the efficacy of apoptosis inhibitors and neuroprotective agents can be evaluated using this model, bringing us closer to clinical applications.

Long-term surgical outcomes of pediatric cataract-multivariate analysis of prognostic factors.

We assessed the 10-year postoperative outcomes of pediatric cataract patients who underwent surgery at the age of 6 years or younger. A retrospective review of medical charts was conducted for 457 eyes of 277 patients, with the age at surgery averaging 1.3 ± 1.5 years (mean ± SD) and the follow-up duration averaging 12.8 ± 2.4 years (ranging from 10 to 17 years). The cohort included 250 eyes of 125 cases with bilateral aphakia (age at surgery 0.5 ± 0.8 years), 110 eyes of 55 cases with bilateral pseudophakia (1.9 ± 1.6 years), 42 cases with unilateral aphakia (1.1 ± 1.3 years), and 55 cases with unilateral pseudophakia (2.6 ± 1.7). A forward stepwise multiple regression analysis revealed that the best-corrected visual acuity at the final visit was significantly associated with laterality of cataract (with bilateral cases showing better results compared to unilateral cases), presence of systemic comorbidities, presence of ocular comorbidities, development of glaucoma, and phakic status (with better results in the pseudophakia group than the aphakia group). The age at surgery did not significantly affect visual acuity outcomes. A multiple logistic regression analysis demonstrated that the incidence of secondary glaucoma was significantly linked to younger age at surgery, phakic status (higher in aphakic than pseudophakic eyes), and presence of systemic comorbidities. In conclusion, after pediatric cataract surgery, final visual acuity was better in patients with bilateral cataracts, those treated with an intraocular lens, and cases without systemic or ocular comorbidities and secondary glaucoma. The development of secondary glaucoma was linked to younger age at surgery, aphakic status, and presence of systemic comorbidities.

The Structural Abnormalities Are Deeply Involved in the Cause of RPGRIP1-Related Retinal Dystrophy in Japanese Patients.

Leber congenital amaurosis (LCA) is the most severe form of inherited retinal dystrophy. RPGRIP1-related LCA accounts for 5-6% of LCA. We performed whole-exome sequencing and whole-genome sequencing (WGS) on 29 patients with clinically suspected LCA and examined ophthalmic findings in patients with biallelic pathogenic variants of RPGRIP1. In addition to five previously reported cases, we identified five cases from four families with compound heterozygous RPGRIP1 variants using WGS. Five patients had null variants comprising frameshift variants, an Alu insertion, and microdeletions. A previously reported 1339 bp deletion involving exon 18 was found in four cases, and the deletion was relatively prevalent in the Japanese population (allele frequency: 0.002). Microdeletions involving exon 1 were detected in four cases. In patients with RPGRIP1 variants, visual acuity remained low, ranging from light perception to 0.2, and showed no correlation with age. In optical coherence tomography images, the ellipsoid zone (EZ) length decreased with age in all but one case of unimpaired EZ. The retinal structure was relatively preserved in all cases; however, there were cases with great differences in visual function compared to their siblings and a 56-year-old patient who still had a faint EZ line. Structural abnormalities may be important genetic causes of RPGRIP1-related retinal dystrophy in Japanese patients, and WGS was useful for detecting them.

Clinical presentations of acquired comitant esotropia in 5-35 years old Japanese and digital device usage: a multicenter registry data analysis study.

PURPOSE: To describe clinical presentations of acquired comitant esotropia and digital device use in children, adolescents, and young adults without neurological problems. STUDY DESIGN: Multicenter prospective observational study. METHODS: Patients with acquired comitant esotropia, without intracranial diseases aged 5-35 years at the time of visit, who were seen at pre-registered facilities within 1 year of onset were enrolled. The duration from the onset of symptoms and the time of digital device usage approximately 1 month before onset and their lifestyles were surveyed. Visual acuity, cycloplegic refraction, and strabismus angles were measured. Data were analyzed in three age groups (Child: 5-12 years, Adolescent: 13-18 years, and Young adult: 19-35 years). RESULTS: Between November 2019 and December 2021, 218 patients were enrolled from 55 facilities, and 194 patients (including 62 children, 69 adolescents, and 63 young adults) were analyzed. The child group spent the least amount of time using digital devices (children: 159; adolescents: 210; young adults: 267 min/work day, p < 0.05; (mean time in the same order below) 229, 338, 314 min/holiday, p < 0.05) and had the largest strabismus angle (mean strabismus angle at near: 30, 22, 18 PD, p < 0.01; at far: 28, 26, 21 PD, p<0.05). CONCLUSION: The clinical features of acquired comitant esotropia and hand-held digital device usage differed between children aged ≤ 12 years and older patients. This report gives the current clinical characteristics of young patients with acquired esotropia and digital device usage.

A pediatric case of congenital stromal corneal dystrophy caused by the novel variant c.953del of the DCN gene.

We report a 1-year-old girl with congenital stromal corneal dystrophy confirmed by genetic analysis. The ocular phenotype included diffuse opacity over the corneal stroma bilaterally. We performed a genetic analysis to provide counseling to the parents regarding the recurrence rate. Whole exome sequencing was performed on her and her parents, and a novel de novo variant, NM_001920.5: c.953del, p.(Asn318Thrfs*10), in the DCN gene was identified in the patient.

Integrator complex subunit 15 controls mRNA splicing and is critical for eye development.

The eye and brain are composed of elaborately organized tissues, development of which is supported by spatiotemporally precise expression of a number of transcription factors and developmental regulators. Here we report the molecular and genetic characterization of Integrator complex subunit 15 (INTS15). INTS15 was identified in search for the causative gene(s) for an autosomal-dominant eye disease with variable individual manifestation found in a large pedigree. While homozygous Ints15 knockout mice are embryonic lethal, mutant mice lacking a small C-terminal region of Ints15 show ocular malformations similar to the human patients. INTS15 is highly expressed in the eye and brain during embryogenesis and stably interacts with the Integrator complex to support small nuclear RNA 3' end processing. Its knockdown resulted in missplicing of a large number of genes, probably as a secondary consequence, and substantially affected genes associated with eye and brain development. Moreover, studies using human iPS cells-derived neural progenitor cells showed that INTS15 is critical for axonal outgrowth in retinal ganglion cells. This study suggests a new link between general transcription machinery and a highly specific hereditary disease.

National survey of amblyopia treatment in Japan: comparison with amblyopia treatment study results of the pediatric eye disease investigator group.

PURPOSE: To investigate the treatment policy for amblyopia in Japan as of 2017 through a survey of multiple facilities and to compare the findings with those obtained by the Amblyopia Treatment Study (ATS) of the Pediatric Eye Disease Investigator Group. STUDY DESIGN: Questionnaire survey study. SUBJECTS AND METHODS: A questionnaire was sent to 181 facilities where patients with amblyopia are being treated. The outcomes of the present survey were compared with the results of the ATS study, and the coincidence rates were evaluated. RESULTS: The questionnaire response rate was 68.0%. The treatment plan that showed the highest agreement between the outcomes of the ATS study and the present study was whether or not treatment was to be given to patients aged 10-15 years who had received no previous treatment; 90% of the facilities answered that they would provide treatment to such patients as well. The next highest agreement was the future treatment of amblyopia with stable visual acuity in the affected eye; 82.6% of the facilities responded that they would reduce the occlusion time. On the other hand, the lowest agreement rate was the follow-up period of the refractive correction for moderate anisometropic amblyopia. The ATS showed "4 months," whereas most of the facilities in the present survey replied "3 months." The agreement rate was 10.8%. CONCLUSION: The amblyopia treatment in Japan survey did not always agree with the research results of the ATS. Japanese ophthalmologists tend to make treatment plans for amblyopia according to their clinical experience.

Maternal Uniparental Isodisomy of Chromosome 4 and 8 in Patients with Retinal Dystrophy: SRD5A3-Congenital Disorders of Glycosylation and RP1-Related Retinitis Pigmentosa.

PURPOSE: Uniparental disomy (UPD) is a rare chromosomal abnormality. We performed whole-exosome sequencing (WES) in cases of early-onset retinal dystrophy and identified two cases likely caused by UPD. Herein, we report these two cases and attempt to clarify the clinical picture of retinal dystrophies caused by UPD. METHODS: WES analysis was performed for two patients and their parents, who were not consanguineous. Functional analysis was performed in cases suspected of congenital disorders of glycosylation (CDG). We obtained clinical case data and reviewed the literature. RESULTS: In case 1, a novel c.57G>C, p.(Trp19Cys) variant in SRD5A3 was detected homozygously. Genetic analysis suggested a maternal UPD on chromosome 4, and functional analysis confirmed CDG. Clinical findings showed early-onset retinal dystrophy, intellectual disability, and epilepsy. In case 2, an Alu insertion (c.4052_4053ins328, p.[Tyr1352Alafs]) in RP1 was detected homozygously. Maternal UPD on chromosome 8 was suspected. The clinical picture was consistent with RP1-related retinitis pigmentosa. Although the clinical features of retinal dystrophy by UPD may vary, most cases present with childhood onset. CONCLUSIONS: There have been limited reports of retinal dystrophy caused by UPD, suggesting that it is rare. Genetic counseling may be encouraged in pediatric cases of retinal dystrophy.

Effectiveness of the Spot Vision Screener in screening 3-year-old children with potential amblyopia in Japan.

PURPOSE: The purpose of this study was to compare the efficiency of conventional screening and of the Spot™ Vision Screener (SVS)-based screening in detecting potential cases of amblyopia during the Visual examination in Three-Year-Old Health Screening Program (VTYOS), that need to be referred for comprehensive examination. STUDY DESIGN: Population-based cross-sectional study METHODS: This study introduced the SVS-based test to the VTYOS (which includes primary, secondary, and comprehensive examinations) of Sagae, Yamagata Prefecture, Japan. Children aged 3 years 6 months scheduled to undergo the secondary examination were subjected to both the SVS-based (evaluation of refractive error and eye alignment) and conventional screening test (questionnaire and visual acuity evaluation). Success rates, proportion of children who needed a comprehensive examination, rates of actual comprehensive examinations, and positive predictive value were determined and compared between conventional screening and SVS-based screening. RESULTS: There were 294 participants; the rate of success of SVS-based screening (99.7%) was higher than conventional screening (89.5%, p < 0.01). The proportion of participants found to need a comprehensive examination according to SVS-based findings (7.5%) was lower than that according to conventional screening-based findings (23.5%, p < 0.01). The positive predictive value of the SVS-based screening test (75.0%) was higher than that of the conventional screening test (31.6%, p < 0.01). SVS-based screening detected 2 cases of amblyopia in 225 cases that passed conventional screening. CONCLUSION: The VTYOS should ideally add SVS-based screening to conventional screening.

Biallelic CDK9 variants as a cause of a new multiple-malformation syndrome with retinal dystrophy mimicking the CHARGE syndrome.

CDK9 has been considered a candidate gene involved in the CHARGE-like syndrome in a pair of cousins. We report an 8-year-old boy with a strikingly similar phenotype including facial asymmetry, microtia with preauricular tags and bilateral hearing loss, cleft lip and palate, cardiac dysrhythmia, and undescended testes. Joint contracture, no finger flexion creases, and large halluces were the same as those of a previously reported patient with homozygous CDK9 variants. The ocular phenotype included blepharophimosis, lacrimal duct obstruction, eyelid dermoids, Duane syndrome-like abduction deficit, and congenital cataracts. Optical coherence tomography and electroretinography evaluations revealed severe retinal dystrophy had developed at an early age. Trio-based whole-exome sequencing identified compound heterozygous variants in CDK9 [p.(A288T) of maternal origin and p.(R303C) of paternal origin] in the patient. Variants' kinase activities were reduced compared with wild type. We concluded that CDK9 biallelic variants cause a CHARGE-like malformation syndrome with retinal dystrophy as a distinguishing feature.

SEVERE RECURRENT FIBROVASCULAR PROLIFERATION AFTER COMBINED INTRAVITREAL BEVACIZUMAB INJECTION AND LASER PHOTOCOAGULATION FOR AGGRESSIVE POSTERIOR RETINOPATHY OF PREMATURITY.

PURPOSE: To describe the clinical features of severe recurrent fibrovascular proliferation after intravitreal bevacizumab injections and laser photocoagulation for aggressive posterior retinopathy of prematurity. METHODS: This retrospective, nonrandomized case series reviewed the medical and ophthalmic records in the referral hospital and our hospital. PATIENTS: Four patients (seven eyes) with aggressive posterior retinopathy of prematurity. RESULTS: The patients were referred for vitrectomy with/without lensectomy for recurrent fibrovascular proliferation with a tractional retinal detachment after combined intravitreal bevacizumab injections and laser photocoagulation. Three patients were born at 22 weeks or 23 weeks' gestational age and one patient at 29 weeks' gestational age. Preoperatively, fluorescein angiography images showed all eyes had tractional retinal detachment from regrowth of fibrovascular proliferation 3 months to 5 months after the intravitreal bevacizumab injection and abnormal retinal vasculature; four eyes had a broad ischemic retina. Postoperatively, four eyes had retinal attachment and three eyes a total retinal detachment. Neovascular glaucoma developed in five of the seven eyes during the clinical course. CONCLUSION: Severe fibrovascular proliferation may recur due to widespread retinal ischemia with capillary dropout and abnormal vasculature after failed combined intravitreal bevacizumab and laser photocoagulation therapy as the initial treatment for aggressive posterior retinopathy of prematurity. Careful follow-up is important especially after anti-vascular endothelial growth factor treatment, with recognition that severe reactivation is possible.

Analysis of IKBKG/NEMO gene in five Japanese cases of incontinentia pigmenti with retinopathy: fine genomic assay of a rare male case with mosaicism.

Incontinentia pigmenti (IP) is an X-linked dominant genodermatosis that is usually lethal in utero in males, though exceptionally they survive very rarely either with Klinefelter syndrome or a somatic mosaicism. We performed genomic analysis of five Japanese IP patients including a rare boy case, all of whom were definite cases with retinopathy. Four patients including the boy revealed the recurrent exon 4-10 deletion in the sole known causative gene IKBKG/NEMO, which was confirmed by various specific PCR techniques. The boy's saliva DNA showed a mosaicism consisting of the deletion and intact alleles, but his blood DNA did not. Relative quantification analysis of the real-time PCR data by ∆∆CT method estimated the mosaicism ratio of the boy's saliva as 45:55 (deletion:intact). A genomic analysis for the recurrent deletion at the nucleotide sequence level has been performed directly using patient's DNA and it has been clarified that the breakpoints are within two MER67B repeats in the intron 3 and downstream of exon 10. This is the first report of the assay for the mosaicism ratio of a male IP case with a recurrent exon 4-10 deletion of IKBKG/NEMO and the sequencing analysis of the breakpoints of the recurrent deletion directly using patient's sample.

Structure of the Retinal Margin and Presumed Mechanism of Retinal Detachment in Choroidal Coloboma.

PURPOSE: To describe the vitreoretinal structure at the margin of the choroidal coloboma in infants and older patients using swept-source (SS) OCT. DESIGN: Retrospective case series. PARTICIPANTS: Nineteen eyes of 16 patients with choroidal coloboma (7 males, 9 females; average age, 12.3 ± 7.1 years). METHODS: The patients were classified into 2 groups: infants 1 year of age or younger (3 eyes) and older patients (16 eyes). Each finding on SS OCT was documented according to previously defined histopathologic findings. MAIN OUTCOME MEASURES: Description of the SS OCT features of choroidal colobomas. RESULTS: Swept-source OCT showed that the extracolobomatous retina centrally traversed the margin to continue as the marginal intercalary membrane (MICM), whereas the outer layers of the MICM were reversed at the point (point of reversal [POR]). The expected duplication was seen in all infant eyes, but in none of the older eyes whose outer layers of the MICM were ambiguous. However, at the boundary between the layered MICM and monolayered central intercalary membrane (CICM), the POR was detectable in all patients. Further SS OCT analysis showed that the MICM schisis and CICM schisis occurred simultaneously with vitreous traction. Retinal detachments (RDs) seen in 4 eyes were connected to the only MICM schisis, and a MICM break was identified in 1 eye. Swept-source OCT showed that retinal pigment epithelial hyperplasia adhered tightly to the retina and that the glial triangle was adhered tightly to the sclera, indicating barriers to the development of RD after MICM schisis. CONCLUSIONS: Swept-source OCT first visualized the POR in infant eyes and showed that the POR was identifiable despite the atrophic changes in the outer layer of the MICM in the older eyes. Based on the POR location, we confirmed that the intercalary membranes reported in previous OCT studies were clearly differentiated between the MICM and CICM. We also showed that the presence of MICM and CICM schisis resulted from vitreous traction at the coloboma margin and that MICM breaks induced RD only if the barrier that prevented the development of RD was broken.

Early laser photocoagulation for extensive retinal avascularity in infants with incontinentia pigmenti.

PURPOSE: To describe the clinical features and treatment outcomes of severe retinopathy in eyes with incontinentia pigmenti (IP) of infants within a few months of birth. STUDY DESIGN: Retrospective clinical study. METHODS: Six eyes of three patients (6-day-old girl, 5-month-old girl, and 14-day-old boy) with IP were examined and treated under general anesthesia. Ophthalmologic examinations were performed including images from wide-angle fluorescein angiography (FA), swept-source optical coherence tomography (OCT), and OCT angiography (OCTA). RESULTS: Ophthalmoscopy showed prominent vascular tortuosity in five eyes, retinal hemorrhages in four eyes, and incomplete vascular development in two eyes. FA showed extensive avascularity including the posterior pole of the retina in all cases except one eye. Prompt and intensive laser photocoagulation stabilized the pre-proliferative severe retinopathy in five eyes; however, foveal structure and vessel anomalies were detected in three of six eyes by OCT and two of five eyes by OCTA. CONCLUSION: Severe retinopathy in the neonatal period and infancy was present not only in the periphery but also in the posterior pole including the fovea, which might be related to retinal vascular maldevelopment. It is, therefore, recommended that wide-angle fundus FA examination be performed in the early postnatal period to detect early signs of severe retinopathy in infants with IP.

Retinal structure in Leber's congenital amaurosis caused by RPGRIP1 mutations.

This study aimed to evaluate retinal structure in the early stage of Leber's congenital amaurosis (LCA) caused by RPGRIP1 mutations. Four patients from two families were included. Case 1 was a 13-year-old girl, cases 2 and 3 were 7-year-old monozygotic twin brothers of case 1, and case 4 was a 17-year-old boy. Comprehensive ophthalmic examinations were performed, including visual acuity measurements, perimetry, electroretinography (ERG), and optical coherence tomography (OCT). To identify potential pathogenic mutations, 74 genes known to cause retinitis pigmentosa or LCA were assessed using targeted next-generation sequencing. OCT showed photoreceptor outer nuclear layer (ONL) thinning in all patients. The lamellar structure was retained in all patients, whereas the ellipsoid zone was extinguished in cases 1, 2, and 3. In case 4, the ellipsoid zone was maintained at 9 years of age but became blurred at 17 years of age. In case 1, OCT indicated slight photoreceptor ONL thinning during the period between 7 and 11 years of age. Mutation analysis revealed RPGRIP1 mutations as the cause for autosomal recessive LCA in all patients. Photoreceptor ONL on OCT is relatively well preserved in the early stage of LCA caused by RPGRIP1 mutations.

X-linked Retinitis Pigmentosa in Japan: Clinical and Genetic Findings in Male Patients and Female Carriers.

X-linked retinitis pigmentosa (XLRP) is a type of severe retinal dystrophy, and female carriers of XLRP demonstrate markedly variable clinical severity. In this study, we aimed to elucidate the clinical findings of male patients with and female carriers of XLRP in a Japanese cohort and demonstrate the genetic contribution. Twelve unrelated families (13 male patients, 15 female carriers) harboring pathogenic mutations in RPGR or RP2 were included, and comprehensive ophthalmic examinations were performed. To identify potential pathogenic mutations, targeted next-generation sequencing was employed. Consequently, we identified 11 pathogenic mutations, of which five were novel. Six and five mutations were detected in RPGR and RP2, respectively. Only one mutation was detected in ORF15. Affected male patients with RP2 mutations tended to have lower visual function than those with RPGR mutations. Female carriers demonstrated varying visual acuities and visual fields. Among the female carriers, 92% had electroretinographical abnormalities and 63% had a radial autofluorescent pattern, and the carriers who had higher myopia showed worse visual acuity and more severe retinal degeneration. Our results expand the knowledge of the clinical phenotypes of male patients with and female carriers of XLRP and suggest the possibility that RP2 mutations are relatively highly prevalent in Japan.

The clock components Period2, Cryptochrome1a, and Cryptochrome2a function in establishing light-dependent behavioral rhythms and/or total activity levels in zebrafish.

The circadian clock generates behavioral rhythms to maximize an organism's physiological efficiency. Light induces the formation of these rhythms by synchronizing cellular clocks. In zebrafish, the circadian clock components Period2 (zPER2) and Cryptochrome1a (zCRY1a) are light-inducible, however their physiological functions are unclear. Here, we investigated the roles of zPER2 and zCRY1a in regulating locomotor activity and behavioral rhythms. zPer2/zCry1a double knockout (DKO) zebrafish displayed defects in total locomotor activity and in forming behavioral rhythms when briefly exposed to light for 3-h. Exposing DKO zebrafish to 12-h light improved behavioral rhythm formation, but not total activity. Our data suggest that the light-inducible circadian clock regulator zCRY2a supports rhythmicity in DKO animals exposed to 12-h light. Single cell imaging analysis revealed that zPER2, zCRY1a, and zCRY2a function in synchronizing cellular clocks. Furthermore, microarray analysis of DKO zebrafish showed aberrant expression of genes involved regulating cellular metabolism, including ATP production. Overall, our results suggest that zPER2, zCRY1a and zCRY2a help to synchronize cellular clocks in a light-dependent manner, thus contributing to behavioral rhythm formation in zebrafish. Further, zPER2 and zCRY1a regulate total physical activity, likely via regulating cellular energy metabolism. Therefore, these circadian clock components regulate the rhythmicity and amount of locomotor behavior.