Biomicroscopy Flashcards

Question

What is the primary form of illumination used by the contact lens fitter?

Answer 1

Direct Illumination; it is called this because the beam of light and microscope are both focused directly on the image being examined. The types of direct illumination and what they are used for depend primarily on the width of the beam.

Answer 2

1.Light directed at the cornea at 45 degree angle 2. Narrow beam 1mm or less 3. High magnification 4. Used to see corneal thickness and layers, scars, neovascularization, lens opacity, the shape of the tear layer under a RGP to identify the lens/cornea relationship.

Answer 3

1. The smallest circular beam 2. Light directed at the pupil at a 45-60 degree angle 3. High illumination and magnification 16-25X 4. Used to see inflammation, flares, cells, metabolic waste

Answer 4

1. Slit width about 2-4m 2. Obliquely focused on the cornea 3. Most common form of illumination used in fitting. 4. Magnification approx 10x 5. Used to see corneal surface and stroma, contact lens surface, lacrimal layer and lens/cornea relationship with the help of fluorescein.

Answer 5

1. Uses the principles of the angle of reflection 2. If the cornea is healthy and smooth, or if the contact lens is clean, the light source will be mirrored. 3. Small imperfections diffuse the light 4. High magnification of 40x 5. Angle of 50 degrees is ideal 6. Used to see endothelial cells

Answer 6

Assess lens dehydration, surface quality, detects improper fits because it highlights bubbles trapped under the limbal area of the lens. Small bubbles=too tight, large bubbles=too loose.

Answer 7

Structural abnormalities of the lens itself, fitting relationships, and the shape of the lacrimal lens.

Answer 8

When a portion of the eye is observed through reflected light. This light can surround the object being observed or it can be reflected off of another structure within the eye.

Answer 9

1. Light is reflected off of the fundus of the iris but the microscope is focused on the cornea. 2. Light comes in from behind the image being observed 3. Used to see epithelial cysts, small scars and blood vessels, contact lens edge quality, edema, and contact lens markings

Answer 10

Direct retroillumination is looking at an area against a light background - the most common Indirect retroillumination is looking at an area against a dark background.

Answer 11

1. Light is offset and focused on the limbus so it will "scatter" across the surface of the cornea 2. Wide illumination at a 45-60 degree angle 3. Magnification 10x 4. Used to see opacities of the cornea; normal cornea appears dark and opacities show grey.

Answer 12

Enhances the fluorescein making it appear yellow so that it is easily seen by the fitter. Ideal for use in fitting and in observing movement.

Answer 13

A red free filter so that it makes the red areas appear black increasing the contrast. This means hemorrhages, blood vessels, and Fleischer's ring are more visible

Answer 14

A yellow filter removes blue from the observed area and makes the fluorescein appear bright green. This makes the positive areas of fluorescein appear very bright.

Answer 15

An ideal pattern reveals that the fitter has taken into account the surface of the cornea through topography or K readings, and fit the contact to align with the corneal surface.

Answer 16

(Spherical lens, Spherical Cornea), When a technician observes a dark center and a bright outer ring, this indicates that the cornea is touching the contact and there is no apical clearance. The smaller the dark area, the less corneal touch.

Answer 17

(Spherical lens, Spherical cornea), Because the lens is steeper than "K", the fluro will pool under the contact resulting in a 3 ring pattern in which the center and the edges are bright green with a fainter green band in the center.

Answer 18

(Spherical lens, toric cornea), when a cornea presents with a with the rule corneal astigmatism (axis within 30 degrees of 180), and a spherical lens is placed on it, the fluro will pool at the top and the bottom portion of the lens with a dark line in the middle. The result is a dark pattern that runs horizontally.

Answer 19

(Spherical lens, toric cornea), when the cornea presents with against the rule corneal astigmatism (axis within 30 degrees of 90), and a spherical lens is placed on it, the pattern looks more like a vertical hourglass.

Answer 20

If there is a break or dent in the corneal epithelium, the fluorecein will pool within those areas of defects creating a bright green pattern. This staining pattern is a clue to issues the patient may be experiencing.

Answer 21

A central abrasion is erosion of the central corneal epithelium that can be caused by long term edema or foreign body trapped under the contact.

Answer 22

Improper removal of a contact will result in an abrasion at the bottom or 6 o clock position of the cornea

Answer 23

If the bend of the posterior curves of the contact is incorrect, it can cause an arc like dent in the corneal epithelium

Answer 24

Dents in the cornea that, if they are in the apical zone, are caused by bubbles trapped under the contact lens from a steep lens. If the dimple veil is in the limbal area, then the lens is too flat.

Answer 25

Scratches in the epithelium are created by dirt or foreign substances trapped under the lens.

Answer 26

Caused by epithelial injury, these are breaks in the cornea with stippling being fine breaks and punctate being larger, more irregular breaks. These breaks are caused by any particulates that are on the contact, poorly fitted contacts, or chemical toxicity.

Answer 27

Stippling type of staining at these areas of the lens are caused by dryness and overexposure from thick contact lens edges, overwearing, inadequate blinking, or from peripheral curves that are too flat.