Do the anatomical features of the eyelids, conjunctiva and cornea matter for contact lenses?
Eyelids
They play an important role in the position and movement of contact lenses. The shape and size of the eyelid opening are important. It is assumed that the vertical dimension of the eyelid opening should be from 9 to 11 mm.
Spontaneous blinking movements normally have a frequency of 15-17 per minute. They depend on gender. It is interesting to know that women blink 1.6 times less often than men. Age, climatic conditions, condition of the eyes and working with a computer, etc., are important.
Blinking is mainly done by the upper eyelid.
Конюнктива Тя се дели на три части:
- Eyelid
It covers the inside of the eyelids and supplies oxygen to the cornea through the tear film. The tear film creates a smooth optical surface by smoothing out irregularities on the cornea, regulating its hydration, supplying it with oxygen and acting as a lubricant between the cornea and the eyelids. It consists of three layers - outer (lipid layer), middle (aqueous), inner (mucin layer).
The tear film is unstable and often breaks, which in turn affects adaptation when wearing contact lenses.
- Fornix conjunctiva
It contains part of the accessory lacrimal glands.
- Bulbous (scleral)
The normal conjunctiva is transparent. In the case of improperly selected contact lenses, it reacts first by turning red, in addition, changes in its structure may occur. But you will find more about the wrong choice in the questions we asked Dr. Galatea Tsvetkova.
Cornea
Роговицата е много чувствителна, това включва усещане за болка, дразнене и допир. С възрастта чувствителността намалява. Намалената такава, осигурява по-лесна адаптация към контактните лещи. Повече за структурата на The Cornea можете да откриете в статията посветена на нея.