NCLE Contact Lens Knowledge Review

NCLE Test review Question This Test Measures Quality of the Tears What is the O2 Permeability What are the Disadvantages of Soft Lenses For succesful contact lens wear, EOP should be at least This test Measures the Quantity of the Tears Neovascularization is mainly due to what the Radii and Power of an average Cornea what are the Layers of the Cornea The Main Disadvantage of Soft contact lenses What is it when we use Contact Lenses to Correct high Myopia A Contact Lens with diameter that is larger than the Cornea is a Hydrophobic or Hydrophilic Which of the following Curves, indicates the flattest Base Curve 7.50mm, 37.50 D, 8.60mm, 49.00 D A CTL was ordered with a BC of 7.85mm but was received from the lab with a BC of 7.80mm. The BC of the actual lens is a CTL with BC of 7.42mm is fitting too loose, a tighter fit may be achieved by changing the base curve to: 7.46mm , 7.85mm , 8.04mm , None of these A CTL has a BC of 7.50mm, what would the PPC most likely be? 7.45mm , 42.50D , 7.35mm , 30.00D What does the Term Haptic Lens refer to? The Secondary Curve of a RGP CTL is Generally Flatter or Steeper than the CPC and by How much? When the Power of a curve changes by 0.50D , the radius of the Curvature Changes by approximately how much? The CPC of a CTL measures 7.5mm Radius, how much is the Power in Diopters? A soft CTL demonstrates excessive movement. This can be fixed with a Lens that has a ______________ Diameter? HEMA is an Abbreviation commonly used to describe what Lens? what is the main reason to utilize a Ballasted CTL? The Central portion of the Back surface of the CTL is called? The Distance between a Flat Surface and the Back surface of the Central Portion of a Lens is called the................ A loose fitting CTL can be made to fit tighter by ___________ the Radius of the CPC. what is an example of a Hydrophilic Lens Material? A Contact Lens in which the anterior surface contains 2 different radii of Curvature and the Posterior surface is Spherical curve is called a ................... The Central Portion of a CTL which contains the refractive power of the CTL is the ...... A CTL which contains 2 curves, One BC and One Secondary Curve. The Smoothing of the junction zones by removing the sharp line between the zones is...... Answer B.U.T TEST (Break Up Time) DK Value of a lens Doesn't correct Irregular Astigmatism Favors Deposit formation 7% The Schirmer Test Good result is 15mm in 5 minutes Dry eye is 5 to 10mm in 5 minutes Hypoxia, Corneal Edema, Tight Contact lens Fit 7.85 mm or +43.00D Epithelium, Bowmans' Layer, Stroma, Descemet's Membrane, Endothelium Protein Deposits Orthokeratology (Ortho-K) Hydrophilic 37.50 D 0.25D steeper than the ordered CTL None of these.... S.S.S Rule 30.00D = 11.25mm / S.S.S Rule A Scleral CTL Size Flatter by 2 to 4 Diopters 0.10mm 45.00D Larger Diameter. (Larger Diameter = Steeper Fit = Tighter Fit) the Chemical name for Soft CTL to have less Rotation of the CTL (usually used in bifocal CTL's) CPC (Central Posterior Curve) or the Base Curve (BC) or the Optic Zone Sagital Depth ( Vault, height) Shortening the radius of the CPC. S.S.S Rule HEMA Front surface Toric Optic Zone (OZ) Bicurve CTL Blending of the curves The measurement from one edge of the lens to the opposite edge is........ A lens which has been cut off to form a horizontal base which improves stabilazations....... the effective power of a lens when measured from the back surface....... wetting angle means..... A lens in which the anterior surface has two different radii and the posterior surface is spherical.... A Lens in which both the posterior surface has two different radii and the anterior surface has two different radii is........ A lens design generallly used in higher plus powers which consists of a central optic zone and a surrounding non-optic peripheral or carreir portion is.... a method of manufacturing soft contact lenses whereby a liquid material is revolved in a mold at a controlled speed and temperature which produces the desired curvature, design, and power....... When we add 50% of the Cylinder to the sphere and determine a Spherical Prescription it's called...... The Tear Film Layers from inside out are.... This Tear Film layer will change the corneal surface from an Hydrophobic surface to a Hydrophilic Surface..... The Lipid Layer has a Primary function of..... what age group has the best prognosis for successful Contact Lens Fitting........ When moved 5mm from it's original position the effective power of a 10.00 D lens will change by........... when do we consider vertex distance compensation for Spectacles and for CTL's? Spectacle Lens is Prescribed at -10.00D, if the lens fit is at a vertex distance of 10mm, an RGP ctl fit on K will require a power of how much? RX -4.00+1.00x90 K: 42.50@180/43.50@90 RGP CTL fit on K has a power of......... +11.00+1.00x20 VD = 12mm K: 46.25/47.25 What's the power of RGP lens fitted on K -3.00-0.50x90 VD = 11 What's the RGP CTL power fit 0.50D steeper than the flattest corneal merridian? -2.50+0.25x90 VD = 12mm power of CTL if fit 0.75 steeper than K.... The CPC of a trial CTL is 44.00D and contains a power equal to +14.87D. The over refraction is equal to -1.62D. What is the Final CTL Rx if the CPC to be ordred is 43.62D.... A -3.50D Lens with a base curve of 44.50D provides excellent visual acuity. if the CPC were changed to 45.00D what power would be needed? a Dry Eye condition can be evaluated with a test called........ RX -3.25D-1.00x180 K = 44.25@180 / 45.25@90 Vertex Distance 12mm what is the power of RGP CTL fitting 0.50D Flatter than K How do you assess the quality of the peripheral curves of a RGP lens? Patient is wearing a RGP lens in the right eye, it has a power of +3.00D and a base curve of 43.25. if the Dr Refracts -0.50D sphere over this lens and a new lens is to be ordered with a BC of 43.00, what will the new power need to be? the optic zone of a RGP lens can be measured with ....... An Enzyme contained in the precorneal tear film that protects the cornea from infections is.......... The layer of the precorneal tear film responsible for exchange of materials across the corneal surface is the Chord Diameter Truncated Lens BVP Back vertex power... the angle that the edge of bead of water makes with the surface of the plastic... the smaller the angle, the greater the wetting ability Front Surface Toric Lenses Bi-Toric Lenticular Bowl Spin-Cast lenses Spherical Equivelant Mucin, Aqueous, Lipid Mucin Layer Preventing Evaporation of the Tears 13-38 0.50D Spectacles 7.00D CTL's 4.00D -9.00D Minus Lens Coming Closer Gains Power -3.00DS +13.00D +13.25D +13.50D all are correct... NCLE will say +13.00D -3.50D VD doesn't matter since rx is less than 4.00D -3.00D +13.63D (LLP= +0.38D) -3.00D (LLP = -0.50D) Schirmer Test -2.75D using a Shadowgraph +2.75D Radiouscope Lysozyme Aqueous Layer how many layers does the cornea have? The average central thickness of the Cornea is....... the corneal epithelium obtains oxygen from the ....... The thickest layer of the cornea is the...... the corneal layer primarily responsible for maintaining the Cornea in a partially hydrated state..... the Descemet's membrane of the cornea is produced by which layer of the cornea..... Sever damage to the corneal endothelium results in what. A tightly fitted soft contact lens can cause....... The Sclera of the eye is covered by what.... New blood vessels that grow into the cornea originate from blood vessels that are located in ......... Obstruction of the flow of aqueous humor out of the anterior chamber results in... a condition where the Iris or portions of the Iris in absent is called the curvature of the central portion of the back surface of a contact lens is the...... the central zone of a contact lens that contains the refractive power of the contact lens is the..... The measurement from one edge of a contact lens to the opposite edge is the..... The base curve of a contact lens is also known as the ..... The Peripheral Posterior Curve of a bicurve Contact Lens is Steeper or Flatter than the CPC what happens to the sagital vault of the contact lens when a contact lens is steepened...? shortening the base curve radius of a contact lens makes the lens steeper of flatter? the problem of a loosely fitting contact lens can be solved by ordering a new contact lens having a ....................... Base Curve Increasing the overall Diameter of a contact lens makes the lens steeper of flatter? The Effective power of a contact lens measured from the back surface is the............... This Contact lens has 2 different Radii on the anterior surface and a Spheric Posterior curve. It's used to correct Residual Astigmatism..... When correcting Large amounts of Corneal Astigmatism a Toric lens must be used that is a ................. Toric. (Front/Back) A contact lens that is used to correct both Corneal and Residual Astigmatism is ................ A Contact lens with a thickened inferior edge that stabilizes the contact lens is called a............ A CTL that is Cut off inferiorly so the lower eyelid can help to stabilize the contact lens is called a ........... A CTL that has a low wetting Angle has ............ Wettability Decreasing the overall diameter of a CTL will loosen or tighten the fit A CTL having a BC radius of 7.94 mm fits too loosely, a tighter fitting CTL will have which one of the following BC.... (7.99 / 7.85) a CTL having an overall diameter of 9.5mm fits too tightly, a looser ctl will have which diameter....... (9.6 / 9.3) an instrument that's used to measure Corneal Astigmatism is..... When the Vertical Corneal meridian is steeper than the Horizontal Corneal Meridian, the corneal astigmatism is...... Concerning measurements of Corneal Curvatures, the longer the mm of Radius the Larger of Smaller the Diopter value....? a CTL material having a large wetting angle is Hydrophobic or Hydrophilic? 5 Layers 0.56mm Precorneal Tear Film Stroma Endothelium Endothelium Corneal Edema Corneal Edema Limbal Compression Bulbar Conjunctiva the Limbus Elevated Intra Ocular Pressure (Glaucoma) Aniridia Base Curve Optic Zone Chord Diameter CPC (Central Posterior Curve) Flatter it increases steeper Shorter (SSS) Steeper Back Vertex Power Front Toric Contact Lens Back Toric Bi-Toric Prism Ballasted Contact Lens Truncated CTL Good Wettability Loosen the fit 7.85 mm 9.3 mm Keratometer WTR With the Rule Astigmatism Smaller (SSS Rule) Hydrophobic A Lab Measurement of the Oxygen permeability of a RGP CTL is DK Value called...... A measurement of the Oxygen Transmissibility of a RGP CTL is called DK/L ........ The Greater the Central Thickness of a CTL the more of less Oxygen Less transmissibility?..... Equivalent Oxygen Performance or Percentage Measures how much Oxygen What is EOP? actually reaches the Cornea while wearing CTL A CTL designed with a peripheral carrier or Flange having no power Lenticular Design and a Central Power Zone is called a ................ CTL Is the Following K reading With the rule or against the rule With The Rule (more at 90) astigmatism?.... 43.00@180/44.00@90 The K-reading of the horizontal meridian of a cornea is 48.00, this is 7.03 mm (337.5 Rule) what mm of radius? Vertex Distance must be considered in determining CTL power if the +/- 4.00D Spectacle Rx is over................ D the BC of a rigid CTL sitting on a cornea is flatter than the corneal Minus curvature. Therefore the Lacrimal Lens power is....... (plus/Minus) the best type of slit lamp illumination to use for detecting gross Sclerotic Scatter corneal edema is called...... the type of slit lamp illumination that is used primarily for a general Diffuse Illumination survey of the external eye is called...... the type of slit lamp illumination that is useful for inspecting the Direct Focal Illumination anterior surface of a contact lens is called the....... refer them to the prescribing Doctor any if a person wanting CTLs has Blepharitis, you should do what? type of "ITIS" has to go back to the DR. on the Tarsal Plate of the Upper eyelid where is the Giant Papillary Conjunctivitis Located?.... margin a test used to assess the quality of the precorneal tear film is called BUT test ( Break Up Time) the...... Polymegathism of the corneal endothelium is thought to be due to ....... Corneal Hypoxia the type of slit lamp illumination used to observe Cells and flare in the Conical Beam Illumination anterior chamber of the eye is......... the type of slit lamp illumination that is the method of choice for examination of microcystic epithelial edema of the cornea is called.... Retro Illumination The best type of Slit Lamp illumination for studying the corneal Specular Reflection endothelium is ...... the Slit lamp light that passes through a cobalt blue filter can be used Corneal Staining the Fit of the Contact to observe.......... Lens Corneal Dry spots a Soft CTL case should be thoroughly cleaned at least........ once per week a Person with Scleral Show requires a (large/small) Diameter soft CTL? Large Diameter Soft CTL Photophobia Corneal Staining Excess Preservatives in Contact Lens Solutions can cause .......... Tearing Itching Conjunctival Redness Conjunctival What can occur during an allergic reaction to a CTL solution..... Chemosis (Swelling) True/False Corneal Sensation is reduced in an Aphakic Eye. True Giant Papillary Conjunctivitis occurs more frequently in people who Soft Hydrogel lenses wear what type of lenses.... An increase in the steepening of the wearing standard thickness soft CTL's longer than 12 hours per day cornea Development of irregular for a prolonged period of time can cause............ astigmatism Permanent form of acquired Keratoconus Limbal Compression is a sign of (loose - tight) fitted ctl Tightly fitting CTL an eye has a Spectacle Rx of -3.00-0.25X180. This eye should be fit -3.00 D (1/3 Rule) with a soft CTL having a power of................ an eye has a spectacle rx of -3.25-0.50X180. This eye should be fit -3.25 D (1/3 Rule) with a hydrogel CTL having a power of........... an eye has a spectacle Rx of -4.00+1.00X180. this eye should be fit -3.50 D (1/3 Rule) with a hydrogel CTL having a power of........... An eye has a spectacle Rx of -6.50+1.00X090. the K readings are 42.00@180/43.00@90. The Vertex Distance is 12mm. This eye should -5.25 D (1/3 Rule + 10.10.1 Rule) be fit with Soft CTL RX of,,,,,,,,,,,,,,,,,,,,,, Good Stability Good Optics Acceptable what are characteristics of PMMA CTL's...... Wettability which of the following CTL materials has the highest Oxygen Silicone Permeability.. (HEMA, PMMA, ACRYLATE, SILICONE) The water content of hydrogel contact lenses varies from.......... 25% to 85% The higher the Water Content of a Hydrogel CTL the.................... the Greater Oxygen Transmissibility. Hydrogel CTL are made of what material. HEMA Tears drain into the ........... Punctum During a blink the lower eyelid moves primarily towards the...... Nose The Muscle responsible for elevation of the upper eyelid is the........ Levator Palpebrae the PH of the Pre-corneal tear Film is...... 7.35 the layer of the pre corneal tear film that is responsible for exchange Aqueous Layer of materials across the corneal surface is the........ Limit the amount of light entering the eye Protect the eye from external irritation The Function of the Eyelids are......... Distribute Tears over the surface of the eye. The opening of the Meibomian glands are found on the...... Eyelid Margin the Meibomian Glands are located in the......... Tarsal Plate. an Acute infection of the Meibomian Glands is called..... an internal Hordeolum with spontaneous blinking, the normal blinking rate is...... 12-18 per minute the pre-corneal tear film is composed of how many layers....... 3 Lipid, Aqueous, Mucus with basic tear secretion, the aqueous tear film layer is secreted by Glands of Wolfring and Krause the.............. the pre-corneal tear film layer that changes the hydrophobic surface Mucous Layer... of the cornea to a hydrophilic surface is the .............. the pre-corneal tear film layer that reduces the rate of tear Lipid layer (oily) evaporation is the.......... The mucous layer of the pre corneal tear film is secreted by the..... Conjuntival Goblet Cells. The Lipid Layer of the Precorneal tear film is secreted from......... the Meibomian Glands A spherical PMMA CTL should be fit so that there is a slight............... Apical Clearance When fitting PMMA CTL, the CTL diameter can be calculated by Pupilary Diameter adding 4 mm to the A high minus RGP CTL should have .........(+/-) Carrier Lenticular Lenses. Plus Carrier Lenticular Lens. Hyperflange the quality of fit of a RGP CTL can be assessed with the use of........ Fluorescein Rigid CTL's can be modified in the office to become Steeper. (trueFalse. False) what solution improves the wettability of Rigid CTL's..... Wetting Solution if a rigid CTL on an eye is too steep the fluorescein pattern will Central Pooling show....... if a rigid CTL on an eye is too flat the fluorescein pattern will show....... Central Touch the size of the entire corneal cap can be measured with the.... Topogometer