Toric Contact Lenses: A Consumer Guide. Toric contact lenses correct astigmatism They can be made from HEMA (soft), silicone hydrogel, or gas permeable materials. Unlike spherical lenses, toric lenses have two different powers in the lens. This characteristic means that the toric lens must remain in one position for the best visual acuity.
The Preamble to the US Constitution, the Pledge of Allegiance, and the Declaration of Independence. Unit Objective. This unit is part of Gilder Lehrmanâs series of Common Core State Standardsâbased teaching resources. These units were developed to enable students to understand, summarize, and analyze original texts of historical significance.
The Pledge of Allegiance of the United States is an expression of allegiance to the Flag of the United States and the republic of the United States of America, originally composed by Colonel George Balch in 1887, later revised by Francis Bellamy in 1892 and formally adopted by Congress as the pledge in 1942.