NACOR EXAM ACTUAL EXAM QUESTIONS AND CORRECT ANSWERS (VERIFIED ANSWERS) PLUS
RATIONALES 2026 Q&A | LATEST EXAM UPDATE 2026/2027
SECTION ONE: QUESTIONS 1–100
Question 1
What is the correct formula for calculating the effective diameter (ED) of a lens blank?
A. A + DBL
B. 2 x the longest radius
C. A - B
D. (A + DBL) - Near PD
🟢 B. 2 x the longest radius
🔴 RATIONALE: The effective diameter is defined as twice the longest radius of the lens shape. This
measurement is crucial for determining the minimum blank size needed for a lens.
Question 2
A patient presents with symptoms of photophobia, redness, and tearing after wearing their contact lenses all
day. Slit lamp examination with fluorescein reveals staining around the limbus and engorged conjunctival blood
vessels, with very little lens movement. What is the most likely diagnosis and initial management?
A. Corneal abrasion; refer to an ophthalmologist immediately
B. Giant papillary conjunctivitis; cease lens wear and refit
C. Tight lens syndrome; cease wear and refit the lens
D. Contact lens-induced dry eye; recommend artificial tears
🟢 C. Tight lens syndrome; cease wear and refit the lens
🔴 RATIONALE: The symptoms and clinical signs—photophobia, limbal staining, vascular engagement, and
,restricted lens movement—are classic indicators of a tight-fitting lens causing corneal hypoxia and mechanical
trauma. The appropriate action is to discontinue the current lens and refit the patient .
Question 3
In the context of NACOR examinations, what is the primary purpose of the national competency examinations?
A. To ensure candidates can successfully complete the PLAR program
B. To verify a candidate's readiness to become a licensed optician by evaluating their ability to safely and
effectively meet public needs
C. To assess the candidate's ability to memorize formulas and optical calculations
D. To determine the candidate's eligibility for provincial regulatory bodies
🟢 B. To verify a candidate's readiness to become a licensed optician by evaluating their ability to safely and
effectively meet public needs
🔴 RATIONALE: According to NACOR, the objective of the examinations is to evaluate a candidate's readiness
to provide safe and effective optical dispensing services to the public, a foundational principle of licensure .
Question 4
What is the "B" measurement in a frame, and what does it represent?
A. The distance between the centers of the lenses, representing the frame's width.
B. The horizontal measurement across the lens, representing the lens width.
C. The vertical measurement of the frame's lens opening, representing the lens depth.
D. The distance between the lens centers, representing the frame's bridge size.
🟢 C. The vertical measurement of the frame's lens opening, representing the lens depth.
🔴 RATIONALE: In ophthalmic frame measurements, the "B" measurement refers to the vertical depth of the
lens opening. This is a fundamental concept in optical dispensing for fitting lenses .
Question 5
A patient who has worn contact lenses for years with no problems now complains of itchy, red eyes and a gritty
,sensation. Slit lamp examination reveals a "cobblestone" appearance on the upper palpebral conjunctiva. What
is the most likely diagnosis?
A. Blepharitis
B. Meibomian gland dysfunction
C. Corneal abrasion
D. Giant papillary conjunctivitis (GPC)
🟢 D. Giant papillary conjunctivitis (GPC)
🔴 RATIONALE: The "cobblestone" appearance on the upper tarsal conjunctiva is a pathognomonic sign of GPC,
a condition often associated with chronic soft contact lens wear, deposits, and mechanical irritation .
Question 6
What is the formula for calculating the minimum blank size (MBS) needed for a lens?
A. MBS = ED + (2 x per-lens decentration) + 2mm
B. MBS = ED - (2 x per-lens decentration)
C. MBS = (A + DBL) + 2mm
D. MBS = 2 x (A + DBL)
🟢 A. MBS = ED + (2 x per-lens decentration) + 2mm
🔴 RATIONALE: The minimum blank size ensures the lens can be cut to fit the frame with the optical center
correctly positioned. The formula accounts for the effective diameter, decentration, and a standard 2mm edge
allowance .
Question 7
A patient recently switched to a cheaper brand of contact lens solution and now reports redness, mild
discomfort, and slight changes in their keratometry readings. Slit lamp exam reveals superficial punctate
keratitis. What is the most likely cause?
A. Contamination of the contact lens case
, B. Tight lens syndrome
C. Toxic reaction to the new solution
D. Blepharitis
🟢 C. Toxic reaction to the new solution
🔴 RATIONALE: Switching solutions can cause a toxic or allergic reaction. The clinical picture of redness,
discomfort, and superficial punctate keratitis is consistent with a solution-induced reaction. The management is
to discontinue the new solution and return to the previous one .
Question 8
The formula for the Prentice Rule is ∆ = cF. What does the variable 'c' represent in this formula?
A. The power of the lens in diopters
B. The distance from the optical center in centimeters
C. The radius of curvature of the lens
D. The index of refraction of the lens material
🟢 B. The distance from the optical center in centimeters
🔴 RATIONALE: The Prentice Rule calculates the induced prismatic effect. 'c' represents the distance in
centimeters from the optical center of the lens to the point of measurement .
Question 9
A patient complains of seeing halos around lights and blurry vision for a few hours after removing their contact
lenses. Slit lamp exam shows central pooling under the lens and folds in Descemet's membrane. Keratometry
readings show significant steepening. What is the diagnosis?
A. Corneal abrasion
B. Tight/steep fitting lens causing corneal edema
C. Contact lens-induced dry eye
D. Giant papillary conjunctivitis
RATIONALES 2026 Q&A | LATEST EXAM UPDATE 2026/2027
SECTION ONE: QUESTIONS 1–100
Question 1
What is the correct formula for calculating the effective diameter (ED) of a lens blank?
A. A + DBL
B. 2 x the longest radius
C. A - B
D. (A + DBL) - Near PD
🟢 B. 2 x the longest radius
🔴 RATIONALE: The effective diameter is defined as twice the longest radius of the lens shape. This
measurement is crucial for determining the minimum blank size needed for a lens.
Question 2
A patient presents with symptoms of photophobia, redness, and tearing after wearing their contact lenses all
day. Slit lamp examination with fluorescein reveals staining around the limbus and engorged conjunctival blood
vessels, with very little lens movement. What is the most likely diagnosis and initial management?
A. Corneal abrasion; refer to an ophthalmologist immediately
B. Giant papillary conjunctivitis; cease lens wear and refit
C. Tight lens syndrome; cease wear and refit the lens
D. Contact lens-induced dry eye; recommend artificial tears
🟢 C. Tight lens syndrome; cease wear and refit the lens
🔴 RATIONALE: The symptoms and clinical signs—photophobia, limbal staining, vascular engagement, and
,restricted lens movement—are classic indicators of a tight-fitting lens causing corneal hypoxia and mechanical
trauma. The appropriate action is to discontinue the current lens and refit the patient .
Question 3
In the context of NACOR examinations, what is the primary purpose of the national competency examinations?
A. To ensure candidates can successfully complete the PLAR program
B. To verify a candidate's readiness to become a licensed optician by evaluating their ability to safely and
effectively meet public needs
C. To assess the candidate's ability to memorize formulas and optical calculations
D. To determine the candidate's eligibility for provincial regulatory bodies
🟢 B. To verify a candidate's readiness to become a licensed optician by evaluating their ability to safely and
effectively meet public needs
🔴 RATIONALE: According to NACOR, the objective of the examinations is to evaluate a candidate's readiness
to provide safe and effective optical dispensing services to the public, a foundational principle of licensure .
Question 4
What is the "B" measurement in a frame, and what does it represent?
A. The distance between the centers of the lenses, representing the frame's width.
B. The horizontal measurement across the lens, representing the lens width.
C. The vertical measurement of the frame's lens opening, representing the lens depth.
D. The distance between the lens centers, representing the frame's bridge size.
🟢 C. The vertical measurement of the frame's lens opening, representing the lens depth.
🔴 RATIONALE: In ophthalmic frame measurements, the "B" measurement refers to the vertical depth of the
lens opening. This is a fundamental concept in optical dispensing for fitting lenses .
Question 5
A patient who has worn contact lenses for years with no problems now complains of itchy, red eyes and a gritty
,sensation. Slit lamp examination reveals a "cobblestone" appearance on the upper palpebral conjunctiva. What
is the most likely diagnosis?
A. Blepharitis
B. Meibomian gland dysfunction
C. Corneal abrasion
D. Giant papillary conjunctivitis (GPC)
🟢 D. Giant papillary conjunctivitis (GPC)
🔴 RATIONALE: The "cobblestone" appearance on the upper tarsal conjunctiva is a pathognomonic sign of GPC,
a condition often associated with chronic soft contact lens wear, deposits, and mechanical irritation .
Question 6
What is the formula for calculating the minimum blank size (MBS) needed for a lens?
A. MBS = ED + (2 x per-lens decentration) + 2mm
B. MBS = ED - (2 x per-lens decentration)
C. MBS = (A + DBL) + 2mm
D. MBS = 2 x (A + DBL)
🟢 A. MBS = ED + (2 x per-lens decentration) + 2mm
🔴 RATIONALE: The minimum blank size ensures the lens can be cut to fit the frame with the optical center
correctly positioned. The formula accounts for the effective diameter, decentration, and a standard 2mm edge
allowance .
Question 7
A patient recently switched to a cheaper brand of contact lens solution and now reports redness, mild
discomfort, and slight changes in their keratometry readings. Slit lamp exam reveals superficial punctate
keratitis. What is the most likely cause?
A. Contamination of the contact lens case
, B. Tight lens syndrome
C. Toxic reaction to the new solution
D. Blepharitis
🟢 C. Toxic reaction to the new solution
🔴 RATIONALE: Switching solutions can cause a toxic or allergic reaction. The clinical picture of redness,
discomfort, and superficial punctate keratitis is consistent with a solution-induced reaction. The management is
to discontinue the new solution and return to the previous one .
Question 8
The formula for the Prentice Rule is ∆ = cF. What does the variable 'c' represent in this formula?
A. The power of the lens in diopters
B. The distance from the optical center in centimeters
C. The radius of curvature of the lens
D. The index of refraction of the lens material
🟢 B. The distance from the optical center in centimeters
🔴 RATIONALE: The Prentice Rule calculates the induced prismatic effect. 'c' represents the distance in
centimeters from the optical center of the lens to the point of measurement .
Question 9
A patient complains of seeing halos around lights and blurry vision for a few hours after removing their contact
lenses. Slit lamp exam shows central pooling under the lens and folds in Descemet's membrane. Keratometry
readings show significant steepening. What is the diagnosis?
A. Corneal abrasion
B. Tight/steep fitting lens causing corneal edema
C. Contact lens-induced dry eye
D. Giant papillary conjunctivitis
