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LDO Review Contacts
| Question | Answer |
|---|---|
| The central posterior curve is also known as what? | Base curve and optical zone |
| The back surface of the lens that has the base curve ground into it and is used for the fitting and power is called what? | Optical Zone |
| What lies between the base curve and the peripheral curve on the posterior lens surface? | Secondary curve or intermediate curve |
| What is the outermost curve on the posterior lens surface? | Peripheral curve |
| What is the treatment given to the sharp junctions between the base curve, secondary curve, and peripheral curve? | Blending |
| the overall width of the lens from one edge to the other and is measured in mm is called what? | Diameter |
| what is the measurement taken from the anterior surface to the posterior surface of the lens at its geometric center? | Center thickness |
| What is the curvature that determines the lens power? | Anterior optical zone radius |
| The difference between the radii of the anterior and posterior lens surfaces creates what? | Lens power |
| What does lenticular flange do to a contact lens? | Aid in lens positioning by increasing or decreasing edge thickness |
| When a contact lens sits low on the cornea would you increase or decrease the edge thickness? | Increase |
| When angulation is placed on the front surface of a lens to reduce edge thickness and decrease lid sensation its called what? | CN Bevel or hyper flange |
| Would you do a CN bevel for a high minus or high plus lens. | High minus |
| What is designated to limit lid irritation and keeps the posterior surface away from the cornea? | Lens edge |
| The edge of a lens has 3 zones, what are they? | Anterior, posterior, and edge apex. |
| What is the addition of plastic to the base of the anterior lens surface? | Prism Ballast |
| What is the purpose of prism ballast? | Aids in proper orientation of astigmatic and bifocal lenses |
| Removal of the inferior and/or superior portions of the lens to aid in orientation and stabilization is called? | Trunction |
| In a _________ lens design, the radius of curvature is the same in all meridians. | Spherical lens design |
| What lens design has a spherical posterior surface curvature with a toric anterior curve? | Front surface toric design |
| What lens design has a toric posterior curvature with two principle meridians 90 degrees apart and the anterior lens surface is spherical? | Back surface toric design |
| What lens design has toric curvatures on both the anterior and posterior surfaces, with principle meridians 90 degrees apart? | Bitoric lens design |
| The distance between the posterior surface of the central area of the lens and the flat surface is called what? | Sagittal depth |
| What are the movable folds that protect the eye from injury, light, and keep the eye moist by spreading tear film? | Eyelids |
| What is the space between the two open eyelids called? | Palpebral fissure |
| What is the main support structure of the eyelids? | the tarsal plates |
| What does the lacrimal gland do? | produce tears |
| Where do the tears drain from the eye? | upper and lower punctums |
| What is attached to the punctum that the tears drain into? | the lacrimal sac |
| What are the layers of the tear film? | lipid, aqueous, and mucous |
| What are 2 functions of the tear film? | forms a smooth refractive surface on the cornea and carries oxygen to the eye |
| How would increasing the diameter change the fit of the lens? | tighten the fit |
| How would decreasing the diameter change the fit of the lens? | loosen and flatten the lens |
| The ability of the contact lens surface to wet can be described by it what? | Wetting angle |
| The amount of oxygen that the lens will allow through is measured by its what? | DK Value |
| What was the first hydrogel lens polymer used for contacts? | HEMA |
| What is the transitional zone from the cornea to the sclera called? | Limbus |
| Why would you use a prism ballast on a contacts lens? | to prevent rotation |
| what is the reciprocal of the focal length of an optical surface, lens, or system? | Vertex power |
| How long does it take a rigid lens wearer to adapt to the way their contacts feel? | 2 weeks |
| When doing keratometry, what is the first thing you need to do? | focus the eyepiece |
| Is the tear break-up time test included in the pre-fitting evaluation? | Yes |
| What instrument is used to evaluate the fit of the contact lens? | Slit-Lamp |
| What dye is used to evaluate corneal stains? | Fluorescein |
| What type of slit-lamp illumination is it when the beam of light is opened to its widest point? | Diffuse illumination |
| When do you use a diffuse illumination? | used for a general survey of the eye and for evaluating corneal staining under the blue light with fluorescein dye. |
| what type of slit-lamp illumination is it when the examiner looks directly at the beam of light and adjusts it to 1-3mm wide? | Direct illumination |
| When do you use direct illumination? | used for judging the fit of the contact lenses |
| What filter is used to verify fluorescein patterns? | cobalt blue filter |
| What is the ideal fluorescein staining pattern? | where the center of the lens is faint green and the peripheral is bright green |
| what would a steep fluorescein pattern look like? | fluorescein pooling in the center of the lens and faint green in the mid periphery |
| What would a flat fluorescein pattern look like? | Very faint green in apex of the lens and pooling in the periphery |
| What modification would be needed for a lens that has central pooling? | decrease the diameter for a looser fit or use a flatter base curve |
| What modification would be needed for a lens that has peripheral pooling? | increase the diameter for a tighter fit or use a steeper base curve |
| What is the biggest advantage soft lenses have over rigid lenses? | Initial comfort |
| If a patient has Irregular Astigmatism, what type of contact lens material would you fit them in? | RGP |
| What is it called when a patient develops an allergic reaction to deposits on the lenses, resulting in inflammation and bumps on the upper lid? | GPC |
| What is the benign yellowish nodule found within the palpebral fissure, just outside the limbus on the conjunctiva called? | Pinguecula |
| What are some disadvantages of high water content lenses? | decreased optics and attracts more deposits |
| What are some advantages of high water content lenses? | Softer and better initial comfort |
| What does the FDA classify material by? | Water content and electronic charge |
| What 2 characteristics affect oxygen transmission? | Water content and thickness |
| What are some advantages of thicker lenses? | easier handling, durability, and visual stability |
| What is a disadvantage of thicker lenses? | Comfort |
| What is the main factor in lens comfort? | edge design |
| What is the draping effect? | the ability of the lens to conform to the shape of the eye |
| In soft lens fitting, the perfect relationship is described as what? | the three point touch |
| What is the three point touch? | the lens touches the center and the two opposite edges from the center in any given direction |
| The curvature of the lens is dictated by the curvature of the what? | Cornea |
| The average corneal curvature is between _____ and _____? | 42.00D and 45.00D |
| Is it recommended to start with flat or steep fitting lenses first? | Flat |
| For a spherical prescription when do you need to compensate for vertex distance? | +or -4.00D or greater |
| If the spectacle prescription is -2.50D, what is the contacts lens prescription going to be? | -2.50D |
| If the spectacle prescription is +1.00D, what is the contacts lens prescription going to be? | +1.00D |
| When is it necessary to use a toric contact lens? | when the cyl is 1.00 or more |
| Starting at 4.00D, for every 2D of power change how much does the vertex factor change? | +0.25D |
| From the spectacle Rx -6.00D, what would the contact lens Rx be? | -5.50D |
| From the spectacle Rx +8.25D, what would the contact lens Rx be? | +9.00D |
| From the spectacle Rx -1.00D, what would the contact lens Rx be? | -1.00D |
| From the spectacle Rx -10.00D, what would the contact lens Rx be? | -9.00D |
| From the spectacle Rx -3.00-0.50x090, what would the contact lens Rx be? | -3.25D |
| Which BC is flatter 8.4 or 8.6? | 8.6 |
| A certain brand of contacts are available in 8.0, 8.4, and 8.7 BC with a 14.0 diameter. Which base curve should be selected first? | 8.7 |
| After lens insertion, how long should you let the lenses settle? | 20 minutes |
| For any soft lens fit to be considered successful what five criteria must be met? | complete corneal coverage, adequate movement, three point touch, good visual acuity, and patient comfort? |
| How far should the contact extend onto the sclera? | 1mm |
| How much lens movement is recommended upon blinking? | .5mm to 1mm |
| How do you evaluate the lag of a contact lens? | In the slit lamp, instruct the patient to look up, down, left, and right evaluating how much the contact lags behind. |
| What parameters must be included when ordering a soft lens? | Base curve, power, diameter, and tint |
| What are the 2 most adverse affects to wearing soft lenses? | lens dryness and surface deposits |
| When not using fluorescein dye, what instrument is best used to verify the three point touch? | Kerotometer |
| What machine is used to verify base curve and optical quality of a lens? | Radiuscope |
| What is the flattest curve on a contact lens? | Posterior peripheral curve |
| What is the ideal finished edge thickness? | between .08mm and .12mm, measured from .5mm in form the lens edge |
| What do you use to verify the lens diameter? | A diameter gauge or measuring magnifier |
| A lens surface that gets progressively flatter from center to edge is called what? | Aspheric |
| What hydrogel lens material has a polymer made up of repeating hydroxyethyl methacrylate monomer units? | HEMA |
| What polymer absorbs and binds water into its molecular structure? | Hydrogel |
| What does hydrophilic mean? | Water loving |
| What is another name for a lens blank? | a button |
| Any curve that is applied outside of the optical zones of the lens posterior or anterior surfaces is called what ? | peripheral curve |
| What rigid, non-permeable contact lens material has a polymer made up of polymethyl methacrylate? | PMMA |
| What is a small chemical unit, or monomer, linked together to form a repeating chemical chain of high molecular weight? | a polymer |
| What is the central anterior curve of a contact lens? | power curve |
| What is an oxygen permeable contact lens plastic whose main ingredients are silicone(for permeability) and methyl methacrylate(for durability and stability)? | silicone acrylate |
| What is the first thing that should be covered on the dispensing visit? | proper lens care and handling |
| How many hours should a new soft lens wearer wear the contacts on the first day? | 4 hours |
| How many hours of wearing time should a new soft lens wearer increase each day? | 2 hours |
| What are some of the adaptive symptoms in soft lens wear? | tearing upon insertion, mild foreign body sensation, mild photophobia, and sometimes a slight headache. |
| What are some abnormal symptoms in soft and rigid lens wear? | persistent pain, burning and excess tearing, redness that does not clear up, hazy vision, and sensitivity to light |
| If a patient accidentally sleeps in their contacts what should be the first thing they do upon awakening? | lens lubricant to loosen the lens |
| How many hours should a new rigid lens wearer wear the contacts on the first day? | 3 hours |
| How many hours of wearing time a should a new rigid lens wearer increase each day? | 1 hour |
| What are some adaptive symptoms in rigid lens wear? | tearing upon insertion, lid irritation, excessive blinking, and difficulty looking up |
| What does the subjective examination include at the follow up exam? | taking the patient history. what they liked and didn't like about the contacts |
| What should the objective examination include? | Visual acuity, overrefraction, slit-lamp examination, and keratometry |
| How long should the patient wear the lenses before their follow up check? | 6 hours |
| At the follow up check, what should be examined during the slit-lamp evaluation? | lens centration, movement, lens surface, and the lens/corneal relationship |
| when doing follow-up K Readings, how much change is acceptable? | 0.50D |
| All extended wear contact lenses are designed to be continuously worn for how long? | 1 week |
| In extended wear contacts how often should you take them out to clean and disinfect, and how long should you leave the out? | once a week they should be taken out and left out over night |
| When should the first follow up visit be with an extended wear patient? | the following morning with in 2 hours of awakening |
| what is the typical follow-up schedule of a new extended wear patient? | one day, three days, one week, and 1 month |
| What is the subjective symptom of corneal edema? | hazy or foggy vision |
| What is another name for a keratometer? | ophthalmometer |
| What is rose bengal used for? | A red dye used to stain dead epithelial cells |
| What type of corneal stain has pinpoint breaks in the epithelium? | Stippling or punctate staining |
| What does a 3 and 9 o'clock stain look like? | stippling on the outside edges of the cornea at 3 and 9 o'clock |
| A curved corneal stain in the periphery of the cornea is what type of stain? | Arcuate stain |
| What are the points where the top and bottom eyelids meet? | Canthi |
| What is the bit of skin that holds sweat and sebaceous glads and is located on the medial canthus? | Caruncle |
| What is the average pH of the tear film? | 7.4 |
| What is Keratitis Sicca? | dry eye syndrome, corneal inflammation due to tear deficiencies |
| What is Dacryocystitis? | inflammation of the lacrimal sac |
| What is Epiphoria? | faulty drainage causing the tears to spill over the lid margin onto the cheek |
| Where is the lipid layer in the tear film produced? | meibomian glands and glands of zeis |
| What are the accessory glands that secrete the aqueous layer in the tear film? | glands of wolfring and krause |
| Where is the mucin layer in the tear film produced? | goblet cells |
| What is the outer tunic made up of? | Sclera and cornea |
| Lack of oxygen to the cornea is called what? | Hypoxia |
| What does the middle tunic consist of? | iris, ciliary body, and choroid |
| What is aniridia? | congenital absence of the iris |
| What is it called when someone has unequal pupil sizes? | Anisocoria |
| What is rubeosis? | neovascularization of the iris |
| What does the inner tunic of the eye consist of? | the retina |
| what are the layer of the crystalline lens? | capsule, cortex, and nucleus |
| What are the fibers that attach the crystalline lens to the ciliary body? | zonules of zinn |
| in contact lenses, where is the base curve measured? | the back surface of the lens |
| What curve on the lens in used to create a tear reservoir to help facilitate the flushing effect blinking has on the tears under the contact lens? | the peripheral curves |
| The lens diameter should be ______ mm smaller than the horizontal visible iris diameter(HVID) | 2mm |
| what is the formula to convert keratometry readings? | 337.5/diopters or 337.5/mm |
| What is the fitting curve? | the back surface of the contact lens |
| What is the power curve? | the front surface of the contact lens |
| When the cornea has more curve on the vertical meridian than the horizontal, it is called what? | with the rule astigmatism |
| When the cornea has more curve on the horizontal meridian than the vertical meridian, is called what? | against the rule astigmatism |
| A lens that is centered between the top and bottom lids so that the top lid has nothing to do with where the lens is fitted is called what? | intrapalpebral fit |
| An increase in peripheral lens edge thickness to aid in raising a low riding contact lens is called what? | myo flange design |
| An increase or decrease in the anterior edge thickness to aid in lens positioning is called what? | lenticular flange |
| What is the power range of a keratometer? | 36.00D-52.00D |
| What is an extra lens added to an instrument for the purpose of supplementary power? | Auxiliary lens |
| What illumination is it when the light is right beside the [art of the eye being examined? | indirect illumination |
| What illumination is it when the light is behind the part of the eye that is being looked at? | retro illumination |
| What slit lamp illumination is it when you shine a 2-3mm light at the limbus at a 90 degree angle? | sclerotic scatter |
| Why type of stain is an arc shaped corneal abrasion caused by the edge of a contact lens? | Arcuate Stain |
| indentations in the corneal epithelium caused by air bubbles getting between the back of the lens and the front of the cornea is an example of what stain pattern? | dimple veiling |
| What RGP lens has no lenticular carrier and is usually spherical? | Single cut lens |
| What is residual astigmatism? | The amount of astigmatism left after subtracting the refractive cylinder and the corneal cylinder |
| What is a tangent streak RGP? | a traditional executive bifocal design |
| What is another name for scleral contact lenses? | Haptic lenses |
| What is the profile analyzer? | a tool used to examine the edge design of a RGP |
| How do you assess the quality of the peripheral curves? | using a shadowgraph |
| The CPC of a rigid lens was ordered 7.84 mm and was received measuring 7.94 mm. This lens is _______ than ordered. | 0.50 flatter |
| an excellent material for a keratoconus patient would be? | Silicone acrylate |
| What ophthalmic instrument is used to assess the shape of the anterior surface of the cornea? | Keratoscope or placido's disk |
| the normal cornea is in a state of what? | deturgesence |
| Using a 2-3mm beam, directed at the cornea and a ring of light appears around the cornea to observe opacities, is what type of illumination? | Sclerotic scatter |
| Using a 2-3mm beam to see behind the observed area and is used for seeing corneal vascularization, edge design and edema, is what type of illumination? | retro illumination |
| What illumination is best to view neovascularization? | Indirect Illumination |
| Using a small circular beam of light to view flare and cells in the anterior chamber, is what type of illumination? | Conical beam |
| What illumination is accomplished by aligning the microscope along the angle of reflection of the light and is used to detect minute imperfections on the contact lens surface? | Specular reflection |
| A form of direct illumination that uses the narrowest beam to see the layers of the cornea and the check angles, is what type of illumination? | optic section |
| What is the most common form of direct illumination used to evaluate the fit of contact lenses? | Parallelpiped Illumination |
Created by:
Kayla Carpenter
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