Refractive error generally occurs either for near or for far but not simultaneously.
If the vision is deteriorated for near and far both then there are multiple causes but the most common being :
- Corneal opacity;
- Cataract (opacification of lens)
- Amblyopia (desensitization of retina)
- Optic neuritis (inflammation of optic nerve)
- Any Retinal pathology
Firstly we have to check to what extent is the vision deteriorated; there are different attributes for this
- Visual Acuity (far and near)
- Visual Field
- Contrast sensitivity
- Colour Vision
All these need to be checked before coming to a certain diagnosis
You will have to consult an Ophthalmologist
Feel free to follow up so we can come close to diagnosis.
Hope it helps :)