Retinal tissue parameters of pediatric patients with vitamin D deficiency will be evaluated in this prospective case-control study. The patients will be divided into 2 groups according to the vitamin D level. Retinal vessel diameters, retinal nerve fiber evaluation, choroidal thickness will be evaluated. Choroidal thinning decrease in retinal artery diameter and increase in retinal vein diameter will be detected in the vitamin D deficiency group.

The study of the relationship between vitamin D status and retinal diseases is a new concept, and there is a large gap in research focusing on the pediatric population in the literature. The importance of vitamin D in retinal maturation and its role in the development of retinal diseases at a young age is being investigated. In this sense, as far as known, it is the first study investigating retinal structure parameters in pediatric patients with vitamin D deficiency.

Inclusion Criteria:(Group 1):

1. age <18 years old
2. serum vitamin D [(25(OH) D), calcitriol] level <20 ngr/mL in previous two weeks
3. visual acuity >20/20
4. manifest refraction spherical equivalent <3D
5. normal biomicroscopic and fundus examination.

Exclusion Criteria:

1. history of any chronic ocular diseases, except for refractive error (e.g., uveitis, glaucoma, retinopathy of prematurity)
2. history of ocular surgery (e.g., cataract, strabismus, open globe injury, laser photocoagulation)
3. having an ocular abnormality (e.g., persistent fetal vasculature, optic disc hypoplasia, fovea plana)
4. history of systemic diseases that have the potential to affect ocular tissues (e.g., diabetes mellitus, Graves' disease, albinism, Down syndrome, Fabry diseases, Wilson syndrome)
5. history of any systemic diseases that can affect the serum vitamin D level (e.g., parathormone or calcium metabolism disorders)
6. already receiving vitamin D treatment.

Pediatrics population

Participants will be told what the plan provided and how it worked. Information will be given about when he will participate in the study and the measurements to be taken for the study.

It will be emphasized that there was nothing that harmed the participants in the examinations.

Participants will be examined at same times of the day in order not to affect the measurement results.

Participants will be divided into groups according to their vitamin D levels

Patients will be examined without knowing their vitamin D level. The OCT evaluations will be performed by a highly trained ophthalmic technician, and the compatibility of the results will be confirmed by two experienced retinal specialists.