Optics and Refraction Practice Questions

Q: This instrument is used for :

Refinement of cylindrical prescription. ***Cross-cylinder (Jackson Cross Cylinder)*** - This tool is specifically designed for the **refinement of axis and power** of the cylindrical component of a patient's refraction. - It consists of an **equal power minus and plus cylinder** mounted with their axes at 90 degrees to each other, allowing for rapid comparison during subjective refraction. *Measurement of corneal curvature* - This is performed using a **keratometer** (or ophthalmometer), which measures the reflection of light from the corneal surface. - It is crucial for **contact lens fitting** and calculating intraocular lens power, not for determining refractive cylinder. *Visual acuity testing* - This is conducted using **Snellen charts** or **LogMAR charts** to quantify the patient's clarity of vision. - While it establishes the need for correction, it does not refine the specific astigmatic prescription. *Measurement of intraocular pressure* - This task is accomplished using a **tonometer**, such as the Goldmann applanation tonometer or Non-Contact Tonometer (NCT). - Measuring ocular tension is a critical step in diagnosing **glaucoma** and is unrelated to refractive lens correction.

Q: What is the expected amplitude of accommodation in a healthy child?

14D. ***14D*** - In a healthy child, the **amplitude of accommodation** is approximately **14 diopters (D)**, reflecting the high elasticity of the **crystalline lens**. - As individuals age, this amplitude gradually decreases due to **presbyopia**, which is related to the loss of lens flexibility. *2D* - An amplitude of **2D** is typically seen in individuals around the age of **50 to 55 years**. - This level suggests significant **presbyopia**, requiring reading aids for near vision. *5D* - An amplitude of **5D** is generally expected in adults around the age of **40 years**. - This indicates the early stages of **presbyopia** where near vision task efficiency begins to decline. *25D* - An amplitude of **25D** is physiologically implausible for the human eye, as the maximum accommodation in an infant is typically around **16-18D**. - Such a high value would far exceed the known anatomical and optical limits of the **accommodation reflex**.

Q: A 58-year-old male presents with gradual painless visual field loss over several years. His intraocular pressure is 26 mmHg in both eyes. He has no history of ocular trauma or steroid use. Visual field testing reveals an arcuate scotoma in the superior field of the right eye. The optic disc of the right eye is shown in Image 2. Which structural finding visible in this image best explains the superior arcuate scotoma?

A. Inferior neuroretinal rim thinning with notching. ***A. Inferior neuroretinal rim thinning with notching*** - In glaucoma, visual field defects occur in the opposite hemisphere to the structural nerve damage; therefore, a **superior arcuate scotoma** is caused by damage to the **inferior neuroretinal rim**. - Localized **notching** and thinning of the neuroretinal rim at the inferior pole indicate focal loss of **retinal nerve fiber layer (RNFL)** axons. *B. Superior neuroretinal rim thinning with notching* - Damage to the superior rim would lead to an **inferior arcuate scotoma** because nerve fibers are arranged in an inverted fashion relative to the visual field. - While superior thinning is common in glaucoma, it does not correlate with the **superior field loss** described in this patient's clinical presentation. *C. Nasal rim thinning with peripapillary atrophy* - **Peripapillary atrophy** is a frequent finding in glaucoma but is not the primary diagnostic structural change that explains a specific **arcuate scotoma**. - According to the **ISNT rule**, the nasal rim is typically the last to thin; damage here would result in temporal field defects rather than superior ones. *D. Diffuse concentric rim thinning with disc pallor* - Diffuse thinning generally causes a **generalized depression** of the visual field rather than a localized, nerve-fiber-bundle-specific **arcuate defect**. - **Optic disc pallor** that exceeds the degree of cupping is more characteristic of **neurological optic neuropathies** than primary open-angle glaucoma.

Q: A 28-year-old man presents with a 3-day history of unilateral red eye, photophobia, and foreign body sensation. He had a similar episode 18 months ago that resolved with topical treatment. His visual acuity is 6/12 in the affected eye. The slit-lamp appearance under cobalt-blue light after fluorescein instillation is shown (Image 2). Which of the following is the most appropriate first-line topical treatment?

A. Topical acyclovir 3% ointment five times daily. ***Topical acyclovir 3% ointment five times daily*** - The clinical presentation and description of cobalt-blue light findings after fluorescein staining indicate a **dendritic ulcer** with **terminal bulbs**, which is pathognomonic for **Herpes Simplex Virus (HSV)** epithelial keratitis. - Topical **acyclovir 3%** is the gold-standard first-line treatment for active viral replication in epithelial disease to prevent further corneal damage. *Topical natamycin 5% suspension hourly* - **Natamycin** is an antifungal agent primarily used for the treatment of **fungal keratitis**, often associated with vegetable matter trauma. - Fungal infections typically present with **feathery borders** and **satellite lesions**, rather than the branching dendritic pattern seen in HSV. *Topical prednisolone 1% four times daily* - **Topical corticosteroids** are strictly **contraindicated** in active epithelial HSV keratitis because they promote viral replication. - Use of steroids in this setting can lead to the rapid expansion of the ulcer into a **geographic ulcer** and potential corneal perforation. *Topical ciprofloxacin 0.3% four times daily* - **Ciprofloxacin** is a fluoroquinolone antibiotic used for **bacterial keratitis**, which usually presents with a dense supportive **stromal infiltrate** or hypopyon. - While prophylactic antibiotics may sometimes be used to prevent secondary infection, they do not treat the underlying **viral etiology** of a dendritic ulcer.

Question 1

This instrument is used for :

Accepted Answer

Refinement of cylindrical prescription

Answer

Measurement of corneal curvature

Answer

Visual acuity testing

Answer

Measurement of intraocular pressure

Question 2

What is the expected amplitude of accommodation in a healthy child?

Accepted Answer

14D

Answer

2D

Answer

5D

Answer

25D

Question 3

A 58-year-old male presents with gradual painless visual field loss over several years. His intraocular pressure is 26 mmHg in both eyes. He has no history of ocular trauma or steroid use. Visual field testing reveals an arcuate scotoma in the superior field of the right eye. The optic disc of the right eye is shown in Image 2. Which structural finding visible in this image best explains the superior arcuate scotoma?

Accepted Answer

A. Inferior neuroretinal rim thinning with notching

Answer

B. Superior neuroretinal rim thinning with notching

Answer

C. Nasal rim thinning with peripapillary atrophy

Answer

D. Diffuse concentric rim thinning with disc pallor

Question 4

A 28-year-old man presents with a 3-day history of unilateral red eye, photophobia, and foreign body sensation. He had a similar episode 18 months ago that resolved with topical treatment. His visual acuity is 6/12 in the affected eye. The slit-lamp appearance under cobalt-blue light after fluorescein instillation is shown (Image 2). Which of the following is the most appropriate first-line topical treatment?

Accepted Answer

A. Topical acyclovir 3% ointment five times daily

Answer

B. Topical natamycin 5% suspension hourly

Answer

C. Topical prednisolone 1% four times daily

Answer

D. Topical ciprofloxacin 0.3% four times daily

Question 5

For refraction in a hypermetropic child, which is the best drug?

Accepted Answer

Atropine ointment

Answer

Phenylephrine

Answer

Atropine drops

Answer

Homatropine

Optics and Refraction — MCQs

Optics and Refraction — MCQs

On this page

Practice by Chapter

Want unlimited practice?