Segment Height, also known as Seg Height or SH, is the vertical measurement in millimeters from the bottom of the lens in your frames, to the beginning of the progressive addition on a progressive lens. Segment height does not apply to Single Vision lenses. The determined Segment Height is specific to each frame and wearer.
Development of round glasses History of round glasses One of the earliest etchings of eyeglasses, dating back to the 13th century, shows some studious clergyman in some ancient monastery squinting at his parchment from behind a pair of round-framed specs. Later, in the early 1600s, a portrait of that well-known cardinal, Fernando Niño de Guevara, shows him sporting yet another pair of circular frames. Of course, these early varieties wouldn’t exactly fly off the shelves today. They often lacked temples, needed to be held by a hand, and were either made of leather or weighty metals like lead and iron. It could be said that the glasses of yesteryear weren’t the best lookers, but they didn’t need to be. They were purely functional, the reserve of a studious and god-fearing elite.
The best time for an eye examination and glasses fitting is typically in the morning. This is because after a full night's rest, the eye muscles, especially the ciliary muscles responsible for focusing, are thoroughly relaxed. This allows for more accurate results during the eye examination. If the examination is conducted in the afternoon or evening, after a day of eye strain, such as prolonged computer use, the ciliary muscles may be fatigued. This can potentially lead to deviations in the eye examination results and subsequently affect the comfort and effectiveness of the glasses prescribed. Symptoms like dizziness and dry eyes may arise a few days after wearing glasses fitted in the late afternoon or evening.
Taking care of your eyes and maintaining regular visits to an eye doctor are essential for good eye health. There are various types of eye exams available, each serving a specific purpose. In this article, we will explore the different types of eye exams and their significance. Comprehensive Eye Exam: Routine Eye Exam: Contact Lens Exam: