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National Certification Organization
for Opticians
The National Contact Lens Examiners
(NCLE) ABO American Board of Opticianry
CLRE Contact Lens Registry Examination
Course Title and Number: ABO NOCE Competency Exam Exam Title: Registry Exam Exam Date: Exam 2025- 2026 Instructor: [Insert Instructor’s Name] Student Name: [Insert Student’s Name] Student ID: [Insert Student ID]
Examination
180 minutes
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ABO - NCLE Basic and Practical Exam Review Questions and Answers | 100% Pass Guaranteed | Graded A+ | 2025- The National Contact Lens Examiners NCLE ABO American Board of Opticianry CLRE Contact Lens Registry Examination
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Questions Correctly Good Luck: -
When moving a plus lens closer to the eye, it will ____ effective power.
- =Answer>> Decrease When moving a plus lens further from the eye, it will ____ effective power. - =Answer>> Increase When moving a minus lens closer to the eye, it will ____ effective power. - =Answer>> Increase When moving a minus lens further from the eye, it will ____ effective power. - =Answer>> Decrease Vertex distance should be compensated for if power is over ____. - =Answer>> +/-7.00D for glasses +/-4.00D for contacts Simple formula for vertex distance - =Answer>> per mm of change = D²/
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🤔 Hybridgrades101@gmail.com Flatter BC = ____ sag = ___ fit - =Answer>> Steeper BC = Larger sag = Steeper fit Flatter BC = Smaller sag = Flatter fit Peripheral curve width is measured... - =Answer>> -Using a hand measuring magnifier or a shadowscope -Tolerance is +/-0.05 mm for a light blend; +/-0.10 mm for a heavy blend Tolerance for sphere powers up to +/-10D - =Answer>> +/-0.25D Tolerance for sphere powers over +/-10D - =Answer>> +/-0.50D Tolerance for cylinder powers less than 2D - =Answer>> +/-0.25D Tolerance for cylinder powers between 2D and 4D - =Answer>> +/-0.37D Tolerance for cylinder powers greater than 4D - =Answer>> +/-0.50D The axis should be within ____º - =Answer>> 5 The add power should be within +/-____D - =Answer>> 0. The power of a given lens is usually expressed in ____ vertex power. - =Answer>> Back (BVP) When measuring back vertex power, the lens should be read with the ____ surface facing the examiner. - =Answer>> Anterior The center of a GP CL is measured with a _____ - =Answer>> -Thickness gauge/lens gauge/lens thickness gauge -Measured in 10ths of mm -Tolerance is +/-0.02 mm
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🤔 Hybridgrades101@gmail.com Central Posterior Curve (CPC) - =Answer>> -The Posterior radius of curvature designed to conform to the apical zone of the cornea -Must be highly polished and of definite optical quality -Referred to in terms of the surface power of the cornea to which it is related -Should be expressed in diopters, followed with its radius in mm enclosed in parenthesis. -AKA base curve or radius Intermediate Posterior Curve (IPC) - =Answer>> -Section of curvature that lies between the CPC and the peripheral posterior curve -There may be one or more of these curvatures, which can be designated as IPC1, IPC2, etc. -Can be expressed in mm, but most often described in diopters -Also notated by its width of curvature in mm **example: IPC 37.00D (9-12 mm) width 0.2 mm Peripheral Posterior Curve (PPC) - =Answer>> -Outermost curve of a lens -Designed to yield a smooth transition from the IPC to the edge of the lens -In combination with the IPC, it allows tear exchange beneath the lens -Was once referred to as the secondary curve, bevel, or inner edge -Also expressed in diopters, followed by a mm value and width **example: PPC 26.00D (13.00 mm) width 0.4 mm Central Anterior Curves (CAC) - =Answer>> -Radius of curvature of the anterior portion of the lens -Determines power of the finished lens -Varies from lens to lens -Must compute with the CPC to yield the pre-determined power -Not relative to the fitting of the lens, only to its manufacture -Does not have to relate to the surface power of the cornea -Expressed in mm of radius of curvature -Manufacturers have slide rules/charts available to relate the CAC to a required power from a given CPC and thickness
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🤔 Hybridgrades101@gmail.com -If a lenticular type lens is used, the flange thickness is measured at the junction of the CAC and IAC -Measured in hundredths of millimeters Optical Zone (OZ) - =Answer>> -Area on the posterior lens surface -The linear diameter of the CPC -Determined by subtracting TWICE the widths of the PPC and various IPC from the overall diameter -HINT: Peripheral and intermediate curves are on BOTH sides of the lens Find the Optical Zone: PPC: 0.4mm IPC1: 0.2mm IPC2: 0.2mm Lens Diameter: 9.5mm - =Answer>> Optical Zone: 7.9mm 0.8mm x 2 = 1.6mm 9.5mm - 1.6mm = 7.9mm Lacrimal Lens - =Answer>> -AKA tear lens -Layer of tears between the back surface of the lens and the front surface of the cornea -If a lens is fit directly on the cornea, the lacrimal lens on zero -If a lens is fit steeper than the cornea, then a plus lacrimal lens is created and must be compensated for: steeper add minus (SAM) -If a lens is fit flatter than the cornea, then a minus lacrimal lens is created and must be compensated for: flatter add plus (FAP) -Will take on the properties of a lens when in contact between the cornea and contact lens A lens with a steep CPC that vaults the corneal apex and touches the cornea at its peripheries is considered a ____ fittinglens. This lens will not ride freely over the cornea and will generally cause corneal edema and subsequent spectical blur. - =Answer>> tight
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🤔 Hybridgrades101@gmail.com A ____ fitting lens is fitted flatter than K and will touch at the corneal apex with excessive movement over the cornea. It is not uncommon for this lens to fall off the eye or become easily decentered. Such a lens may cause abrasions at the corneal apex and may also cause corneal edema. - =Answer>> loose If the lens is too flat, the fitter will generally ____ the fit by going ____.
- =Answer>> tighten, steeper 4 refractive mediums - =Answer>> -Cornea -Aqueous -Crystalline Lens -Vitreous Index of refraction of the cornea - =Answer>> 1.37(6) (Avg. dioptric power: 43D) Index of refraction of the aqueous - =Answer>> 1. Index of refraction of the Crystalline lens - =Answer>> 1.42 (Avg. dioptric power: 17D) Index of refraction of the vitreous - =Answer>> 1. Index of refraction of the tear film - =Answer>> 1. Index of refraction of the lens material - =Answer>> Varies depending on the material, but generally close to 1. The lacrimal lens will have a refractive power ____ ____ to the dioptric value of the steepness or flatness in relationship to the cornea. - =Answer>> proportionally equal -Example: a lens fit 0.50D steeper than K will have a lacrimal lens of +0.50D
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🤔 Hybridgrades101@gmail.com Delta K (∆K) - =Answer>> -Difference in the powers in the two principal meridians on the cornea -True corneal astigmatism is when ∆K equals the manifest cylinder, both in power and in axis If corneal astigmatism falls between 0 and 1.75D, you would start by going ___ ___ than K. - =Answer>> +0.50 steeper example: flattest meridian is 42.50. Going steeper by +0.50 brings it to 43.00, which would be the starting BC Diffused Illumination - =Answer>> -Uses widest slit, longest aperture -Light source positioned at an angle of 40º-50º -Used to view overall areas, to observe the ocular adnexa, cornea, sclera, lids, conjunctiva, lens surface, and CL fitting characteristics Direct Illumination - =Answer>> -Most important/useful illumination -Light source positioned at an angle of 40º-50º to oculars -Light beam and oculars are focused in coincidence on area being evaluated -The difference in the illumination is not the angle used, but where the beam is directed or focused and the width -Varying width and aperture creates different illuminations Optic(al) Section - =Answer>> -Type of direct illumination that uses a narrow beam to create a cross-section of the cornea -Used to illuminate and observe individual layers of the cornea and tear film -Used to evaluate corneal thickness, thinning, distortions, or depth of a foreign body -Shows corneal-lens relationship Parallelepiped - =Answer>> -Type of direct illumination -Uses a 0.5-3.0 mm beam and a 40º-50º angle to create a 3-D cube
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🤔 Hybridgrades101@gmail.com -Used to assess width, depth, and height of an object within the cornea -Useful in observing scars, infiltrates, staining, and the corneal-lens relationship Indirect Illumination - =Answer>> -Light source is moved out-of-click, the beam is 2-3 mm wide and is positioned next to the area being studied -Illuminated area is translucent or opaque, allowing for observation adjacent to illumination -Used to observe foreign bodies, corneal nerves, and opacities -Oscillation of light accentuates details Retroillumination - =Answer>> -Light source is out-of-click, moved to the side of the area being observed -Using a 1-3 mm beam, the light is reflected off the iris and used to back-light the area studied -Useful in examining corneal scars, debris, microcysts, scratches on the lens, sub-epithelial changes, corneal vascularization, diffuse edema, and surface deposits Sclerotic Scatter - =Answer>> -Uses a focused parellelepiped placed out- of-click directed at the limbus -Oculars are not used -The light is dispersed at the limbus, reflected through the cornea, creating a circumcorneal halo -Used to observe edema, stromal folds, lens deposits, bubbles under the lens, lens defects, and scratches Corneal Topography - Axial Map - =Answer>> -Most widely understood map of the cornea for many CL fitters -Overall shape of the cornea -Colors relate to steepness/flatness -Sagittal reading measures the curvature of the cornea in diopters and is called the axial power map -Calculates curvature rather than power
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🤔 Hybridgrades101@gmail.com -This view helps the practitioner to quickly determine if corneal astigmatism is symmetrical Corneal Topography - Profile Views - =Answer>> -Graphically represent the individual axes of the cornea to help depict the 3-D nature of the cornea Radiuscope - =Answer>> -AKA optic spherometer -Used to verify base curves, including both spherical and toric curves -Also used to detect warped CLs -Tolerance for BC is +/-0.025 mm Lensometer - =Answer>> -AKA vertometer, lensmeter, focimeter -Used to verify power of the lens, optics evaluation, cylinder power, axis location, and prism -When documenting power, the user should identify whether the reading is in front vertex vs. back vertex V-Channel; Hand Measuring Magnifier; or Shadowscope - =Answer>> - Used to measure the overall diameter of a GP lens -Measurement should be taken across the middle part of the lens -Tolerance is +/-0.05 mm in all meridians Shadowscope - =Answer>> -Used to view lens edges, surface, blends, overall diameter, and optical zone diameter The optical zone diameter can be measured with what instruments? - =Answer>> -Hand Measuring Magnifier or Shadowscope -Tolerance is +/-0.10 mm for a mild blend -Tolerance is +/-0.20 for a medium/heavy blend The blend on a GP lens should be... - =Answer>> -Light Blend: 0.10 mm -Medium Blend: 0.20 mm -Heavy Blend: 0.30 mm -Light blends are easier to see than heavy blends
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🤔 Hybridgrades101@gmail.com Steep Fluorescein Pattern - =Answer>> Bright green pooling center, very faint green pooling on diameter of lens Flat Fluorescein Pattern - =Answer>> Bright green pooling on diameter of lens, very faint green in center Against-the-rule Astigmatism Pattern - =Answer>> Bright green pooling horizontally, faint green pooling vertically With-the-rule Astigmatism Pattern - =Answer>> Bright green pooling vertically, faint green pooling horizontally Prism Ballast - =Answer>> Common technique to stabilize lens from rotating. Added thickness will position lens inferiorly (bottom of cornea) Truncation - =Answer>> Cutting off .50mm to 1.50mm of bottom edge of lens to provide stability. Reduces diameter, making a looser fit. Double Slab-off - =Answer>> Lens is thicker centrally and thinner at top and bottom of lens. Provides comfort to wearer, but may cause some stability issues. Aspheric Lens Design - =Answer>> Hyperflange - =Answer>> Used to correct high riding minus lenses. Myoflange - =Answer>> Used to correct low riding plus lenses. Monovision - =Answer>> Corrects presbyopia in contact wearers. One eye uses distance (dominant) and the other eye uses reading (resessive) Segment Bifocal - =Answer>> Same concept as spectacle bifocal. Must be prism ballast. Often crescent shaped.
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🤔 Hybridgrades101@gmail.com A bi-toric rigid lens will show - =Answer>> Two base curves on the radiuscope, sphero-cylindrical rx on the lensometer The ANSI tolerance for a soft lens diameter is - =Answer>> ±0. The ANSI tolerance for a soft lens refractive power on a Rx 5.12D to 10.00D - =Answer>> ±0. The ANSI tolerance for RGP Base Curve is - =Answer>> ±0.05mm The ANSI tolerance for RGP lens diameter is - =Answer>> ±0.05mm Which instrument allows simultaneous verification of lens diameter, optic zone width, and peripheral curve - =Answer>> Radiuscope Which instrument is best to observe the blends of rigid contact lens - =Answer>> Profile Analyzer If a toric lens rotates to the fitters left - =Answer>> Add the degrees of rotation to the prescribed axis If a toric lens rotates to the fitters right - =Answer>> Subtract (minus) the degrees of rotation to the prescribed axis Increasing the sagittal depth of a rigid lens will - =Answer>> Not change the effective power of the lens How would you stop rotation in a bifocal lens - =Answer>> Truncate the lens Change the base curve Increase prism The DK value of a lens is - =Answer>> Oxygen permeability of that material
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🤔 Hybridgrades101@gmail.com The original rigid material used in contact lens manufacturing - =Answer>> Polymethylmethacrylate (PMMA) Orthokeratology may be defined as - =Answer>> Reduction of refractive errors by corneal molding with the contact lens applications What can be used to evaluate a dry eye patient - =Answer>> Sodium Flourscein Schirmer Strips Rose Bengal An advantage of a flourocarbon lens is its - =Answer>> High DK value Given an Rx of -4.00 + 0.75 x 90 K readings of 43.50@180/44.25@ a lens designed on K would have an effective sphere power of - =Answer>> -3.25 (always remember to transpose to minus format) A protein found in the tear film that is a potent germ killer - =Answer>> Lysozyme When trial lens fitting a soft lens patient, after placing the lens on the eye, you should - =Answer>> Allow the lens to settle twenty minutes before evaluating Corneal epithelial edema will appear as - =Answer>> A grey haze, using a slit lamp with sclerotic scatter and the unaided eye Apical flourescein pooling under a rigid lens indicates - =Answer>> A tight fit A dynamic flourescein pattern is best illuminated by - =Answer>> Cobalt blue light An "ideal" flouorescein pattern for a spherical lens on a spherical cornea would show - =Answer>> An even distribution of flourescein with added thickness under the peripheral curves
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🤔 Hybridgrades101@gmail.com Diameter of a contact lens can be reduced by: a. razor blade b. cut down stone c. file technique d. all the above - =Answer>> d. all the above Good example of a bifocal contact lens which may rotate without vision impairment is - =Answer>> An aspheric lens In aspheric lens design, the change in curvature that occurs from the center to the edge of the aspheric zone is - =Answer>> Eccentricity What is the easiest in-office modification to perform on RGPs? - =Answer>> Adding minus power When rigid lenses are manufactured, which parameter is cut first? - =Answer>> Central Posterior Curve/CPC/Base Curve Removal of plastic from the bottom of a lens to produce a flat edge that will control rotation - =Answer>> Truncation Mounting the lens blank in the lathe so that the face of the button is perpendicular to the spindle is necessary to avoid - =Answer>> Unwanted prism "Haptic" lens is used in reference to - =Answer>> Scleral lens A finished contact lens will have the following properties - =Answer>> 1. Diameter cut to size both sides surfaced
- Peripheral curves have been added
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- Edge has been finished. What contact lens offers the best comfort and easiest adaptation? - =Answer>> Soft Which of the following has the flattest curve? a. 7.50mm b. 7.90mm c. 8.10mm d. 7.20mm - =Answer>> c. 8.10mm Which of the following has the steepest curve? a. 43.00D b. 47.50D c. 49.00D d. 39.00D - =Answer>> C. 49.00D The rate at which oxygen passes through a specific contact lens of a given thickness - =Answer>> Oxygen transmissibility At a 36.00D curve on the keratometer measures approximately ____mm chord of the cornea. a. 4mm b. 8mm c. 3mm d. 1mm - =Answer>> a. 4mm The keratometer measure a point within the cornea called the - =Answer>> Visual center The major drawback of contact lens materials containing silicone is - =Answer>> Wettability
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