Terms
These terms cover the handbook "Optics: from light to the lens" (the guide), published under the name OPSIDOR, and this website, which is operated by Zero Opti LTD, Bulgaria.
What the guide is
The guide is a digital educational handbook of 134 pages with worked problems for opticians and optometry students.
Buying the guide
The guide is not sold on this website. It is sold through a third-party sales platform. The price, payment, delivery, taxes and refund rules for each order are set by that platform's terms, which apply when you buy. If you have not received your guide, or the file will not open, contact the platform first, or write to info@opsidor.com and we will help. This does not limit any rights you have under mandatory consumer law.
Using the guide
- You may use the guide for your own study and work.
- You may not copy, share, resell or publish the guide, in whole or in part, without our written permission.
- The guide and this site are protected by copyright. © 2026 OPSIDOR. All rights reserved.
Educational material only
The guide is a study companion. It does not replace your official textbook, your instructor, or professional eye care. Where it differs from your course, follow your course. The practice modules are for education. Contact lenses should only be fitted by a qualified eye care professional. Formulas and numerical examples were checked, but we cannot guarantee the guide is free of errors. If you find one, please tell us.
Liability
To the extent the law allows, we are not liable for decisions made only on the basis of the guide. This does not limit liability that cannot be limited by law.
Contact
Questions about these terms: info@opsidor.com.