1.
(a) Indications
-The stenopaic slit refraction is useful for confirming the results of other refraction techniques for patients with irregular astigmatism or reduced visual acuity. - It is helpful for patients who have difficulty understanding the complex instructions associated with other subjective techniques. -It is important to note that, like the pinhole, the stenopaic slit may be used diagnostically to determine a patient's potential visual acuity. -The astigmatism present in the patient’s old spectacles should be considered -The small amount of cylindrical power is of little consequences, in that the subjective end point can quickly be rechecked after the stenopaic slit is removed (b) Techniques

Axis determination
i. remove cylinder power from retinoscopy and
ii. identify BVS or MPTMV, VA
iii. fogged the patient (F=1/2 CYL + 0.50 DS) and watch the acuity chart iv. put the stenopaic slit at any position
v. the slit is rotated until acuity is maximized. The slit now lies along the minus cylinder axis. Spherical power
vi. with the slit in this position, the fog is reduced to best acuity. vii. the lens in place is the sphere power of the patient’s lens formula (pt’s final sphere) viii. the slit is rotated 90 degrees. This will fog the patient again viiii. the fog is again reduced to best acuity. The algebraic difference between the power of the lens in place at the end of this operation and the lens power in place at the end of step one is the minus cylinder power (c) Advantages

- recommended for refracting patients with significant optical anomalies, including keratoconus and lenticular distortion - recommended for patients that have irregular astigmatism
- can be done on patients that have difficulty in understanding the instructions on other subjective techniques (d) Disadvantages
- this technique is crude
- should be only be used for cylinders > 1.00 DC
- advisable to favour objective measures of astigmatism from autorefraction,...

...Chapter 13_Graphing the ConicSections
Ellipses
In this study guide we will focus on graphing ellipses but be sure to read and understand
the definition in your text.
Equation of an Ellipse (standard form)
Area of an Ellipse
( x − h) 2 ( y − k ) 2
+
=1
a2
b2
with a horizontal axis that measures 2a units, vertical axis
measures 2b units, and (h, k) is the center.
The long axis of an ellipse is called the major axis and the short
axis is called the minor axis. These axes terminate at points that
we will call vertices. The vertices along the horizontal axis will be
( h ± a, k ) and the vertices along the vertical axes will be ( h, k ± b) .
These points, along with the center, will provide us with a method
to sketch an ellipse given standard form.
A = π ab
Graph
( x − 5) 2 ( y − 8) 2
+
=1
9
25
First plot the center.
Then use a = 3 and
plot a point 3 units to
the left and 3 units to
the right of the
center.
Use standard form to
identify a, b, and the
center (h, k).
Next, use b = 5 and
plot a point 5 units up
and 5 units down
from the center.
Label at least 4
points on the ellipse.
In this example the major axis is the vertical axis and the minor axis is the horizontal
axis. The major axis measures 2b = 10 units in length and the minor axis measures
2a = 6 units in length. There are no x- and y- intercepts in this example.
Problems Solved!
13.4 - 1
Chapter 13_Graphing the...

...Conics are surprisingly easy! There are four types of conicsections, circles, parabolas, ellipses, and hyperbolas. The first type of conic, and easiest to spot and solve, is the circle. The standard form for the circle is (x-h)^2 + (y-k)^2 = r^2. The x-axis and y-axis radius are the same, which makes sense because it is a circle, and from
In order to graph an ellipse in standard form, the center is first plotted (the (h, k)). Then, the x-radius is plotted on both sides of the center, and the y-radius is plotted both up and down. Finally, you connect the dots in an oval shape. Finally, the foci can be calculated in an ellipse. The foci is found in the following formula, a^2 b^2 = c^2. A is the radius of the major axis and b is the radius of the minor axis. Once this is found, plot the points along the major axis starting from the center and counting c amount both directions.
In order to determine if an equation is an ellipse, the following three criteria must be met. There must be an x^2 and a y^2 just like in a circle. However, the coefficients of the x^2 and y^2 must be different. Finally, the signs must be the same. For example, equation 4 is an ellipse. 49x^2 + 25y^2 +294x 50y 759 = 0 has an x^2 and a y^2. It also has different coefficients in front of them, and finally, both have the same sign! There you have it, an ellipse!HyperbolasBoy, now it is starting to get tough! But dont worry, hyperbolas are not...

...Chapter 10 : Quadratic Relations and ConicSections
History of ConicSections
History of ConicSections
Apollonius of Perga (about 262-200 B.C.) was the last of the great mathematicians of the golden age of Greek mathematics. Apollonius, known as "the great geometer," arrived at the properties of the conicsections purely by geometry. His descriptions were so complete that he would have had little to learn about conicsections from our modern analytical geometry except for the improved modern notation. He did not, however, describe the properties of conicsections algebraically as we do today. It would take almost 2000 years before mathematicians would make great advances in the understanding of conicsections by combining both geometric and algebraic techniques.
Apollonius defined the conicsections as sections of a cone standing on a circular base. The cone did not have to be a right cone, but could be slanted, or oblique. Apollonius noticed that all sections cut through such a cone parallel to its base were circles. He then extended the properties that he observed from these circles to ellipses and the other conicsections. He even solved the difficult problem of finding the shortest...

...see that everyone just called ellipses circles because they were both round. After they circle was defined, the ellipse did not fit in the description, and scientists began to study them. It wasn’t until the early 1600s when the focus was discovered by Kepler. Scientists first started thinking about the ellipse while studying the orbit shape of the planets. After years of research, they decided to make a new conic shape instead of calling all of the ellipses circles. They knew the seasons which helped them consider that the earth is not revolving in a circle, but rather in an oval.
The length of an ellipse wasn’t discovered until 1914 by Ramanujan. According to Kepler's First Law of Planetary Motion, the orbit of each planet is an ellipse, with one focus of that ellipse at the center of the Sun. Newton's reconsideration of this law states that the orbit of each planet is a conicsection, with one focus of that conicsection at the center of the Sun. To properly understand planetary orbits, we therefore need some understanding of ellipses in particular and conicsections in general.
Ellipses are used in our everyday lives. It is important to know where they came from and how far they date back (Even though they have been here since the earth was created).
Since you see them everywhere, why not try and learn more about them?
Source:...

...A conic or conicsection is a plane curve that can be obtained by intersecting a cone with a plane that does not go through the vertex of the cone. There are three possibilities, depending on the relative position of the cone and the plane. If no line of the cone is parallel to the plane, the intersection is a closed curve, called an ellipse. If one line of the cone is parallel to the plane, the intersection is an open curve whose two ends are asymptotically parallel; this is called a parabola. Finally, there may be two lines in the cone parallel to the plane; the curve in this case has two open pieces, and is a hyperbola.
In mathematics, parametric equations bear slight similarity to functions: they allow one to use arbitrary values, called parameters, in place of independent variables in equations, which in turn provide values for dependent variables. A simple kinematical example is when one uses a time parameter to determine the position, velocity, and other information about a body in motion. Abstractly, a relation is given in the form of an equation, and it is shown also to be the image of functions from items such as R. It is therefore somewhat more accurately defined as a parametric representation. It is part of regular parametric representation.
Converting a set of parametric equations to a single equation involves solving one of the equations usually the simplest of the two for the parameter. Then the solution of the...

...The Ethics of Refusing a Caesarean Section
April 2004
e -Cases in Ethics
* In January of 2004, Melissa Ann Rowland—a young woman with a long history of mental illness—refused to undergo a Caesarean section that doctors said was necessary to protect the lives of her unborn twins. Doctors told her that low amniotic fluid and poor growth placed the twins in danger, but she refused the surgery until too late, reportedly on cosmetic grounds—she is alleged not to have wanted the resulting vertical scar.
* In 1987, Angela Carter, who was dying of cancer, also refused a C-section. She sought to remain pregnant until the 28th week of pregnancy, the point at which doctors had once told her her baby would have the best chance to survive. At 26 weeks, however, physicians felt that the child had a 50% chance of surviving outside Angela’s dying body, and virtually none if the surgery was not performed. Angela’s condition had deteriorated to the point that her understanding of the implications of refusing the surgery was unclear, but she seemed to refuse the operation. Her distraught husband and mother would not consent to the surgery.
It is hard to imagine anyone reading either of these stories and not having a strong reaction. Reactions are radically different, however, depending on the ethical principles on which they are grounded. For example, there are those whose arguments stem from the belief that there is an ethical...

...Section 8 Housing Pros and Cons
Section 8 Housing Pros and Cons
Gary Hage
Composition II
Mr. Ryan
May 16, 2010
.
Section 8 Housing Pros and Cons
Pros
Section 8 is government assistance to help low-income families obtain safe, decent, and affordable housing. A perspective section 8 tenant must apply to a local Public Housing Agency. When an eligible tenant comes to the top of the Public Housing Agency’s housing choice voucher waiting list, the Public Housing Agency issues a housing choice voucher to the tenant. Tenants who receive Section 8 vouchers are responsible for finding their own rental housing. The vouchers they receive from their housing agency are to help pay the rent.
This is good for both the renter and the landlord; the amount of money section 8 pays for rent varies based on the voucher holder's qualifications. Once a voucher holder locates a property and is approved by the property manager, there is a string of events that take place. The voucher holder fills out a form that the property manager signs. The voucher holder submits this form to his/her case worker at the Public Housing Agency. The case worker executes a contract with the property manager. This contract authorizes the Public Housing Agency to make subsidy payments on behalf of the tenant. If the tenant...

...Over the years birthing methods have changed a great deal. When technology wasn't so advanced there was only one method of giving birth, vaginally non-medicated. However, in today's society there are now more than one method of giving birth. In fact, there are three methods: Non-medicated vaginal delivery, medicated vaginal delivery and cesarean delivery, also known as c-section. In the cesarean delivery there is not much to prepare for before the operation, except maybe the procedure of the operation. A few things that will be discussed are: the process of cesarean delivery, reasons for this birthing method and a few reasons for why this birthing method is used. Also a question that many women have is whether or not they can vaginally deliver after a cesarean delivery, as well as the risks and benefits if it. Delivering a child by a c-section also has a few advantages and disadvantages for both the mother and child; this will also be discussed in more depth a bit later.
Unlike vaginal birth delivery, the process of a cesarean delivery is quite different, but just as safe as giving vaginal birth (Taylor, 1). When delivering a baby using the cesarean method, there are two ways anesthetic can be used. The women can be put into an unconscious state using the anesthetic, therefore she will be asleep during the entire operation and her coach may not be present. The other way for the anesthetic to be used would be in an epidural or spinal block to...