prism reference point Taken from from http://www.zeiss.com web site: For a progressive power lens or semifinished lens blank, that point on the front surface stipulated by the manufacturer at which the prismatic effect of the finished lens is determinde. NOTE: The prism measured is the resultant of prescribed prism and prism thinning. The following excerpt…

In 1621, a Dutch physicist named Willebrord Snell (1591-1626), derived the relationship between the different angles of light as it passes from one transperent medium to another. When light passes from one transparent medium to another, it bends according to Snell’s law which states: that the angle of refraction is related to the angle of…

Children can have any one of a range of eye conditions. All of them affect children in different ways and require individual treatment and/or support. The most common eye conditions affecting children are: 1. Myopia (short sight) Children with myopia tend to concentrate on near work and are less aware of the wider environment (or…

Depending on the individual’s vision and type of work, there are several options the type of lenses for computer glasses. Single vision, bifocal, trifocals, and progressive lenses are the main types of lenses prescribed for computer glasses. Most often, a separate pair of glasses is needed for computer work, in addition to the patient’s dress…

Properly used contact lenses can be very safe and convenient. However, many wearers take big risks by avoiding yearly eye exams and over wearing their lenses. Both practices can result in serious damage to your eyes. Having contacts fitted by an eye care professional is very important because the cornea (clear outer layer of the…

Progressive lenses are by far one of the most complex lenses on the market. This often leaves the patient begging to know what the difference is between brands and designs. What all progressive lenses have in common is a distance section towards the top of the lens, a reading section towards the bottom nasal area…

Transposing a Rx prescription is simply converting the prescription from minus cylinder notation to plus cylinder notation. The optical properties of the prescription remain the same. Procedure: 1) Add the cylinder power to the sphere power to arrive at the new sphere power. 2) Change the sign of the cylinder power. 3) Add or subtract…

There is high demand for sunwear in wrap form; it is estimated that as many as 25% of the prescription market is dispensed in highly curved lenses. Besides looking cool, wrap sunwear also provides better wind, dust, and sun protection than other lenses since they fit close and reduce light leak. However, the lens position…

Picture this: A young, female patient/customer is sitting at a dispensing table, awaiting delivery of her eyeglasses. The dispenser brings the glasses to the table, hands them to the customer, who places them on her head. The “optician” seems to ask a question of the customer, who smiles, shakes her head yes, stands up and…

Amblyopia (pronounced am-blee-oh’-pee-ah) – also called lazy eye – is reduced visual acuity in one eye due to an interruption of the normal development of eyesight in that eye early in childhood. It can be mild (e.g. 20/40) to severe (20/200 or worse). Amblyopia is usually not correctable with lenses alone. But if it is…