The Contact Lens Manufacturers Association utilizes the hostage bubble technique to test wettability, which is the ISO standard; in any case, this strategy was intended to be utilized with inflexible gas-penetrable contact lens angles, and there is no current ISO standard for investigating delicate lens angles. Accordingly, specialists utilize an assortment of strategies and information translation techniques, making it hard to look at the information.
The contact lens angle is the angle shaped between a drop of fluid and the outer layer of the lens angles. Little contact angles are identified with an extended limit of the tears to spread out over the external layer of contact lenses and lead to an all the more consistent tear film. A wettable surface has a contact angle of 0˚, more noteworthy than 0˚ to 90˚ is viewed as to some degree wettable, between 90˚ to 180˚ is to some extent nonwetting and more prominent than 180˚ is nonwetting.
The three main examination techniques used to check the contact angles of contact lenses are the sessile drop, captive bubble, and Wilhelmy plate methods. All night and day contacts lenses are made with the same techniques.
The Sessile Drop Technique:
The sessile drop procedure includes utilizing a needle to put a drop of fluid on the outer layer of a contact lens. The contact angle is the angle made between the outer layer of the contact lens and the drop. Pictures or recordings of the investigation are recorded and dissected with the instrument’s program to decide the contact angle. The sessile drop method is quick and simple to perform. The sessile drop procedure can likewise quantify static and dynamic contact angles, which can help separate between different contact lens materials.
The captive bubble technique:
In the captive bubble procedure, a contact lens is lowered in fluid (generally water). A needle is utilized to put either a little air bubble or one more fluid with a lower thickness on the outer layer of the lens. The contact angle is point-shaped between the outer layer of the contact lens and the air bubble. Likewise, with the sessile drop strategy, the captive bubble method just requires a modest quantity of the test fluid, insignificant example arrangement and the information is gathered by the instrument’s program. Carrying out the captive bubble technique takes longer than the sessile drop system because changing the air pocket to the lens surface is monotonous.
The Wilhelmy plate technique includes embedding and eliminating a contact lens from a fluid. A rectangular example of a contact lens is appended to an equilibrium situated over the liquid. The power of the example is set to zero toward the start of the examination when the lens is practically in touch with the arrangement. The example is then submerged into the arrangement, then, at that angle, removed back to the underlying position. This cycle is rehashed a couple of times. The power that the example goes through when it is brought down and eliminated from the fluid is recorded and used to compute the contact angle.