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100+ Free ICO Part B (ORI) Practice Questions

Pass your ICO Optics, Refraction, and Instruments Examination (Part B) exam on the first try — instant access, no signup required.

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Key Facts: ICO Part B (ORI) Exam

60 questions

ICO Part B is 60 single-best-answer questions, each with four options

ICO - Optics, Refraction, and Instruments (Part B)

90 minutes

The Optics, Refraction, and Instruments examination lasts one and a half hours

ICO - Optics, Refraction, and Instruments (Part B)

3 subjects

Part B covers optics, refraction and instruments

ICO - Optics, Refraction, and Instruments (Part B)

No negative marking

Correct answers score a positive mark; wrong or blank answers score zero

ICO - Optics, Refraction, and Instruments (Part B)

380 CHF

The Part B examination fee is 380 Swiss Francs, reduced in collaborating countries

ICO Examination

Standard Examination

Part B is one of three ICO Standard Examinations on the path to FICO

ICO Examination

Prerequisite for Part C

Passing Part A and Part B is required before sitting Clinical Ophthalmology

ICO Examination

100

Free original practice questions in this bank

OpenExamPrep

The ICO Optics, Refraction, and Instruments Examination (Part B) is a 90-minute paper of 60 single-best-answer multiple-choice questions, each with four options. It is administered by the International Council of Ophthalmology and is usually taken early in residency. Marking is positive only, with no penalty for wrong or blank answers, and there is no published fixed pass percentage. The fee is 380 Swiss Francs, reduced for candidates in collaborating-society countries. The three subject areas are optics, refraction and instruments. This 100-question bank provides original practice across all three areas with detailed explanations.

Sample ICO Part B (ORI) Practice Questions

Try these sample questions to test your ICO Part B (ORI) exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1A thin lens has a power of +5.00 D. What is its focal length in air?
A.+0.20 m
B.+5.00 m
C.+0.50 m
D.+2.00 m
Explanation: Power in dioptres is the reciprocal of the focal length in metres (P = 1/f). For a +5.00 D lens, f = 1/5 = 0.20 m, or 20 cm. The lens is converging, so the focal length is positive.
2Light travelling in glass (refractive index 1.5) meets a glass-air interface. What is the approximate critical angle beyond which total internal reflection occurs?
A.About 42 degrees
B.About 30 degrees
C.About 49 degrees
D.About 60 degrees
Explanation: The critical angle is given by sin(theta_c) = n2/n1 = 1.0/1.5 = 0.667, so theta_c = arcsin(0.667), which is about 42 degrees. Beyond this angle, light is totally internally reflected at the glass-air boundary.
3According to Snell's law, when light passes from a less dense to a more dense medium, the refracted ray:
A.Bends away from the normal
B.Bends toward the normal
C.Continues without bending
D.Is totally reflected
Explanation: Snell's law states n1 sin(theta1) = n2 sin(theta2). Moving into a denser medium (higher n) means the light slows and bends toward the normal, reducing the angle of refraction relative to the angle of incidence.
4An object is placed 50 cm in front of a +4.00 D thin lens. Where is the image formed?
A.50 cm behind the lens
B.25 cm behind the lens
C.At infinity
D.12.5 cm behind the lens
Explanation: Using vergence: incident vergence L = 1/(-0.50) = -2.00 D. Image vergence L' = L + P = -2.00 + 4.00 = +2.00 D. Image distance = 1/2.00 = +0.50 m, so the image is 50 cm behind the lens, real and inverted.
5A prism deviates light toward its base. In which direction does the image of an object seen through the prism appear to shift?
A.Toward the apex
B.Toward the base
C.It does not shift
D.Vertically only
Explanation: A prism bends light rays toward its base, but the image of an object appears displaced toward the apex. This is the fundamental rule used when prescribing prisms to correct ocular deviations.
6One prism dioptre (1 PD) deviates a ray of light by how much at a distance of 1 metre?
A.1 cm
B.1 mm
C.10 cm
D.1 degree
Explanation: One prism dioptre produces a 1 cm displacement of a light ray measured at a distance of 1 metre. Prism dioptres therefore describe a tangent-based linear deviation, not an angular one in degrees.
7Prentice's rule states that the prismatic effect at a point on a lens equals:
A.Power (D) multiplied by decentration (cm)
B.Power (D) divided by decentration (cm)
C.Decentration (cm) divided by power (D)
D.Power (D) multiplied by vertex distance (mm)
Explanation: Prentice's rule is P (prism dioptres) = F (lens power in dioptres) x d (decentration from optical centre in cm). It quantifies the induced prism when a patient looks through a point away from the lens's optical centre.
8A patient looks through a point 5 mm below the optical centre of a +6.00 D lens. What prismatic effect is induced?
A.3 prism dioptres base up
B.3 prism dioptres base down
C.30 prism dioptres base up
D.0.3 prism dioptres base up
Explanation: By Prentice's rule, P = F x d = 6.00 x 0.5 cm = 3 prism dioptres. Looking below the optical centre of a plus lens, the prism base is up (base toward the optical centre for a plus lens), giving 3 PD base up.
9The lensmaker's equation relates a lens's power to its refractive index and:
A.The radii of curvature of its surfaces
B.Its weight
C.The wavelength of room light only
D.The distance to the object
Explanation: The lensmaker's equation, P = (n-1)(1/r1 - 1/r2), gives the power of a thin lens from the refractive index of the material and the radii of curvature of its two surfaces. It does not depend on object distance.
10Spherical aberration in an optical system causes:
A.Peripheral rays to focus closer to the lens than paraxial rays
B.Different colours to focus at different points
C.A straight line to appear curved
D.Loss of image brightness only
Explanation: Spherical aberration occurs because peripheral (marginal) rays passing through the edge of a spherical lens are refracted more strongly and focus closer to the lens than central paraxial rays. This blurs the focal point and reduces image quality.

About the ICO Part B (ORI) Exam

The ICO Optics, Refraction, and Instruments Examination (Part B) is one of the three ICO Standard Examinations and is usually taken early in ophthalmology residency. It is a 90-minute paper of 60 single-best-answer multiple-choice questions, each with four options and a single correct answer, marked positively with no penalty for wrong or blank answers. The paper covers three subject areas: optics (geometric and physical optics, lenses, prisms, vergence and the schematic eye), refraction (refractive errors, retinoscopy, subjective refraction, spectacle and contact lens optics, accommodation and low vision) and instruments (the optical principles behind the slit lamp, ophthalmoscopes, retinoscope, keratometer, lensmeter, tonometer, OCT, biometry and perimetry). Passing the Visual Sciences and Optics, Refraction, and Instruments examinations is a prerequisite for the Clinical Ophthalmology examination, and completing all three Standard Examinations plus the Advanced Examination leads to the FICO designation.

Assessment

A single paper of 60 single-best-answer multiple-choice questions, each with four options and one correct answer, covering optics, refraction and the optics of ophthalmic instruments.

Time Limit

One and a half hours (90 minutes).

Passing Score

A positive mark is awarded for each correct answer; no mark is deducted for incorrect or blank answers. The ICO sets the pass standard centrally and does not publish a fixed percentage; candidates are told whether they passed and receive a score breakdown.

Exam Fee

380 Swiss Francs, with lower fees in countries whose ophthalmology societies collaborate with the ICO. (International Council of Ophthalmology (ICO))

ICO Part B (ORI) Exam Content Outline

35%

Optics

Geometric and physical optics: nature of light, reflection and refraction, Snell's law and critical angle, prisms and Prentice's rule, thin and thick lenses, vergence and the lensmaker's equation, the reduced and schematic eye, spherical and chromatic aberration, magnification, polarization, interference, diffraction and the basic physics of lasers.

40%

Refraction

Refractive errors and their correction: myopia, hyperopia, regular and irregular astigmatism, presbyopia and anisometropia; retinoscopy, the cross-cylinder and subjective refraction; spectacle lens optics, vertex distance, prism, decentration and aniseikonia; contact lens optics including tear-lens power; accommodation and the near point; and low vision magnification aids.

25%

Instruments

Optical principles of ophthalmic instruments: the slit lamp and its Galilean telescope, direct and indirect ophthalmoscopy, the retinoscope, keratometer and corneal topographer, the lensmeter (focimeter), Goldmann applanation tonometer, fundus camera, optical coherence tomography, A- and B-scan ultrasound biometry and IOL power calculation, perimetry, gonioscopy mirrors and the operating microscope.

How to Pass the ICO Part B (ORI) Exam

What You Need to Know

  • Passing score: A positive mark is awarded for each correct answer; no mark is deducted for incorrect or blank answers. The ICO sets the pass standard centrally and does not publish a fixed percentage; candidates are told whether they passed and receive a score breakdown.
  • Assessment: A single paper of 60 single-best-answer multiple-choice questions, each with four options and one correct answer, covering optics, refraction and the optics of ophthalmic instruments.
  • Time limit: One and a half hours (90 minutes).
  • Exam fee: 380 Swiss Francs, with lower fees in countries whose ophthalmology societies collaborate with the ICO.

Keys to Passing

  • Complete 500+ practice questions
  • Score 80%+ consistently before scheduling
  • Focus on highest-weighted sections
  • Use our AI tutor for tough concepts

ICO Part B (ORI) Study Tips from Top Performers

1Master vergence and the basic optics formulas first: light vergence (L' = L + P), the thin-lens and lensmaker's equations, Prentice's rule and transverse magnification underpin most Part B questions.
2Drill retinoscopy logic until it is automatic: know how 'with' and 'against' movement relate to the far point, when to add or subtract working-distance dioptres, and how to neutralise each meridian.
3Use power-cross diagrams for astigmatism so you can convert between plus and minus cylinder, find the spherical equivalent and read keratometry readings without confusion.
4Learn the optical principle behind each instrument, not just its name: for example the slit lamp is a Galilean telescope, the Goldmann tonometer applies the Imbert-Fick principle, and the indirect ophthalmoscope gives a real, inverted, magnified aerial image.
5Practise spectacle and contact lens problems involving vertex distance, effectivity, prism by decentration and the tear-lens, since these account for a large share of refraction questions.
6Use a clinical optics resource such as the AAO BCSC Section 3 and work through past-style questions; because there is no negative marking, always make your best attempt at every item.

Frequently Asked Questions

How many questions are on the ICO Optics, Refraction, and Instruments examination?

The Part B examination consists of 60 single-best-answer multiple-choice questions, each with four options and one correct answer, taken over one and a half hours.

Is there negative marking on ICO Part B?

No. A positive mark is awarded for each correct answer, and no mark is deducted for an incorrect answer or a question left blank, so candidates should attempt every question.

What subjects does the ICO Part B examination cover?

Three subject areas: optics (geometric and physical optics), refraction (refractive errors, retinoscopy, subjective refraction, spectacle and contact lens optics) and instruments (the optical principles of ophthalmic devices).

How much does the ICO Part B examination cost?

The fee is 380 Swiss Francs. Fees vary by country, and lower fees are offered to candidates in countries whose ophthalmology societies collaborate with the ICO.

When is the ICO Part B examination usually taken?

It is one of the three ICO Standard Examinations and is frequently taken early in residency. Passing the Visual Sciences and the Optics, Refraction, and Instruments examinations is required before sitting Clinical Ophthalmology (Part C).

Are these official ICO examination questions?

No. These are original OpenExamPrep practice questions written to the ICO Part B standard for study purposes. They are not copied from official ICO examination papers.