NCLE ExamJanuary 10, 202516 min read
NCLE Study Guide 2025: Everything You Need to Know
Your comprehensive guide to contact lens fitting, care, and troubleshooting. Master every NCLE exam topic.
What This Guide Covers
- Contact lens types, materials, and parameters
- Fitting procedures for soft and RGP lenses
- Care systems and patient education
- Troubleshooting and complications
NCLE Exam Overview
Format
Computer-based, multiple choice
Questions
150 (125 scored + 25 pretest)
Time Limit
3 hours
Passing Score
Scaled score of 300+
Topic 1: Contact Lens Fitting (~35%)
The largest section focuses on proper lens selection and fitting procedures.
Pre-Fitting Evaluation
- • Patient history and lifestyle assessment
- • Corneal measurements (K readings)
- • HVID (horizontal visible iris diameter)
- • Pupil size in different lighting
- • Tear film evaluation
- • Lid anatomy and tension
Soft Lens Fitting
- • Base curve selection (typically 8.3-8.9mm)
- • Diameter selection (typically 13.8-14.5mm)
- • Coverage should extend 1-2mm beyond limbus
- • Adequate movement (0.25-0.5mm on blink)
- • Good centration over cornea
RGP Lens Fitting
- • Base curve selection based on K readings
- • Diameter typically 9.0-9.6mm
- • Fluorescein pattern evaluation
- • Alignment fit vs. slight apical clearance
- • Edge lift assessment
- • Adequate movement (1-2mm on blink)
Toric Lens Fitting
- • When to prescribe: cylinder ≥ 0.75D
- • Stabilization methods: prism ballast, thin zones
- • LARS rule for axis adjustment
- • Rotation assessment and compensation
Multifocal Contact Lenses
- • Simultaneous vision designs (center-near, center-distance)
- • Alternating/translating designs
- • Monovision as an alternative
- • Managing patient expectations
Key Formulas & Rules
- • LARS Rule: Left Add, Right Subtract (for toric axis adjustment)
- • Flat K + 0.50mm = Initial RGP base curve (general guideline)
- • SAM-FAP: Steeper Add Minus, Flatter Add Plus (for over-refraction)
- • Vertex Distance: Compensate Rx for powers over ±4.00D
Topic 2: Contact Lens Materials & Design (~30%)
Soft Lens Materials
| Material | Dk | Water Content | Notes |
|---|---|---|---|
| HEMA (Hydrogel) | 8-20 | 38-55% | Traditional, affordable |
| High Water Hydrogel | 20-35 | 55-75% | More oxygen, may dehydrate |
| Silicone Hydrogel | 60-175 | 24-48% | Highest Dk, extended wear |
RGP Materials
- • PMMA: Original material, no oxygen permeability (rarely used)
- • Silicone Acrylate: Dk 12-50, good wettability
- • Fluorosilicone Acrylate: Dk 50-200, best oxygen transmission
Understanding Dk and Dk/t
- • Dk: Oxygen permeability of the material
- • Dk/t: Oxygen transmissibility (accounts for lens thickness)
- • Daily wear minimum: Dk/t of 24
- • Extended wear minimum: Dk/t of 87
- • Higher Dk/t = healthier cornea
Lens Parameters
- • Base Curve (BC): Radius of curvature, measured in mm
- • Diameter (DIA): Overall lens size in mm
- • Power: Sphere, cylinder, axis
- • Center Thickness (CT): Affects Dk/t and comfort
- • Optical Zone (OZ): Area containing the Rx
Topic 3: Care & Maintenance (~20%)
Care System Types
- • Multi-Purpose Solution (MPS): Clean, rinse, disinfect, store in one
- • Hydrogen Peroxide: Powerful disinfection, requires neutralization
- • Saline: Rinsing only, no disinfection
- • Daily Cleaners: Surfactant cleaners for deposits
- • Enzymatic Cleaners: Protein removal (weekly)
Disinfection Agents
- • PHMB (Polyhexamethylene biguanide): Most common in MPS
- • Polyquad: Gentle, good for sensitive eyes
- • Hydrogen Peroxide 3%: Most effective, requires neutralization
- • Povidone Iodine: Older system, rarely used now
Patient Education Topics
- • Proper insertion and removal technique
- • Hand washing before handling lenses
- • Never use tap water with contacts
- • Replacement schedule compliance
- • Case cleaning and replacement (every 3 months)
- • When to remove lenses (redness, pain, blur)
Critical Safety Points
- • Never use tap water—risk of Acanthamoeba
- • Never "top off" solution—always use fresh
- • Never sleep in lenses not approved for overnight wear
- • Never share contact lenses
Topic 4: Anatomy & Pathology (~15%)
Corneal Anatomy
- • Epithelium: Outermost layer, 5-6 cell layers, regenerates quickly
- • Bowman's Layer: Acellular, doesn't regenerate
- • Stroma: 90% of corneal thickness, collagen fibers
- • Descemet's Membrane: Basement membrane of endothelium
- • Endothelium: Single layer, pumps fluid, doesn't regenerate
Contact Lens Complications
- • Corneal Neovascularization: Blood vessel growth from hypoxia
- • Giant Papillary Conjunctivitis (GPC): Large bumps under upper lid
- • Corneal Ulcer: Serious infection, immediate referral
- • CLARE: Contact Lens Acute Red Eye
- • Corneal Edema: Swelling from lack of oxygen
- • Dry Eye: Reduced tear production or stability
Tear Film
- • Lipid Layer: Outermost, from meibomian glands, prevents evaporation
- • Aqueous Layer: Middle, from lacrimal gland, provides nutrients
- • Mucin Layer: Innermost, from goblet cells, helps tear spread
- • TBUT (Tear Break-Up Time): Normal is 10+ seconds
Troubleshooting Guide
Common Problems & Solutions
"Lens feels dry"
→ Check Dk/t, water content, rewetting drops, wear time
"Vision fluctuates with blinking"
→ Poor fit, excess movement, dry lens, deposits
"Lens rotates (toric)"
→ Check fit, may need different stabilization design
"Red eyes after wear"
→ Hypoxia, solution sensitivity, overwear, infection
"Can't see up close (multifocal)"
→ Increase add power, try different design, check centration
Master the NCLE Exam
Our comprehensive course covers every NCLE topic with interactive lessons and contact lens case studies.
Start Free ChapterStudy Tips for Success
Know your materials: Understand Dk, Dk/t, and when to use different materials.
Master LARS: Toric rotation compensation is heavily tested.
Study complications: Know signs, symptoms, and when to refer.
Understand care systems: Know which solutions work with which lenses.