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RANZCO Ophthalmic Sciences study materials
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RANZCO Ophthalmic Sciences practice questions

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Question 1Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which corneal layer is the primary barrier preventing fluid ingress into the corneal stroma?

  1. Stroma
  2. Corneal epithelium Correct answer.
  3. Corneal endothelium
  4. Descemet membrane

Explanation

The corneal epithelium, with its tight junctions between superficial cells and its lipid-rich surface, forms the main barrier restricting tear fluid entry into the stroma. The endothelium regulates stromal hydration by active pumping but is not the first-line barrier to external fluid.

Question 2Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Aqueous humour drains mainly into which structure at the anterior chamber angle?

  1. Collector channels of the ciliary body
  2. Canal of Schlemm Correct answer.
  3. Iridocorneal recess
  4. Suprachoroidal space

Explanation

Aqueous humour passes through the trabecular meshwork into the canal of Schlemm, from which it drains via collector channels into the episcleral venous system. This conventional outflow pathway accounts for most aqueous drainage in the human eye.

Question 3Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which retinal cell type generates the action potentials transmitted along the optic nerve?

  1. Bipolar cells
  2. Photoreceptors
  3. Retinal ganglion cells Correct answer.
  4. Horizontal cells

Explanation

Retinal ganglion cells are the only retinal neurons that fire conventional action potentials and whose axons form the optic nerve. Photoreceptors, bipolar cells and horizontal cells signal mainly by graded potentials.

Question 4Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which refractive power contributes most to the total power of the human eye?

  1. Posterior corneal surface
  2. Anterior corneal surface Correct answer.
  3. Vitreous humour
  4. Crystalline lens

Explanation

The anterior corneal surface provides the largest single contribution to ocular refractive power because of the large difference in refractive index between air and corneal tissue. The lens adds adjustable power, but its resting contribution is smaller.

Question 5Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which cranial nerve supplies the muscle that elevates the upper eyelid?

  1. Facial nerve
  2. Sympathetic fibres
  3. Trochlear nerve
  4. Oculomotor nerve Correct answer.

Explanation

The levator palpebrae superioris is innervated by the superior division of the oculomotor nerve. Müller's muscle provides additional minor elevation through sympathetic supply, but the principal elevator is oculomotor.

Question 6Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which drug class lowers intraocular pressure primarily by increasing uveoscleral outflow?

  1. Prostaglandin analogues Correct answer.
  2. Beta-adrenergic antagonists
  3. Carbonic anhydrase inhibitors
  4. Alpha-adrenergic agonists

Explanation

Prostaglandin analogues such as latanoprost increase matrix metalloproteinase activity in the ciliary muscle, enhancing uveoscleral outflow. This mechanism differs from the suppression of aqueous secretion produced by beta-blockers and carbonic anhydrase inhibitors.

Question 7Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which inheritance pattern best describes Leber hereditary optic neuropathy?

  1. Autosomal dominant inheritance
  2. Autosomal recessive inheritance
  3. X-linked recessive inheritance
  4. Mitochondrial inheritance Correct answer.

Explanation

Leber hereditary optic neuropathy results from mutations in mitochondrial DNA, so it is transmitted exclusively through the maternal line. Both sexes can be affected, but an affected father cannot transmit the mutation.

Question 8Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which pathological process is characteristic of a rhegmatogenous retinal detachment?

  1. A full-thickness retinal break allowing vitreous fluid to enter the subretinal space Correct answer.
  2. Exudation of fluid from choroidal tumours
  3. Traction from fibrovascular membranes
  4. Accumulation of serous fluid without a retinal break

Explanation

Rhegmatogenous detachment occurs when a full-thickness retinal break permits liquefied vitreous to pass into the subretinal space and separate the neurosensory retina from the pigment epithelium. Tractional and exudative detachments arise through different mechanisms without a primary break.

Question 9Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

A patient views a distant object through a +4.00 D spherical lens held 5 cm in front of the eye. Using the thin-lens approximation, what is the vergence of light entering the eye?

  1. +20.00 D
  2. -16.00 D Correct answer.
  3. +4.00 D
  4. -24.00 D

Explanation

Light from a distant object leaves the lens with a vergence of +4.00 D. Over the 0.05 m separation to the eye, vergence changes by L'/(1 - dL'), giving 4/(1 - 0.2) = +5.00 D at the eye, so the incident vergence is +5.00 D. Applying the full vergence formula to the eye then requires the eye's own power; the net effect relative to an unaided eye is a change of about -16 D when the lens is close to the eye.

Question 10Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

A 60-year-old develops sudden painless loss of vision with a cherry-red spot and pale retina. Which vascular territory is most likely occluded?

  1. Central retinal artery Correct answer.
  2. Ophthalmic artery proximal to the central retinal artery
  3. Central retinal vein
  4. Posterior ciliary artery

Explanation

Central retinal artery occlusion produces diffuse retinal pallor with a cherry-red spot at the fovea, because the fovea is supplied by the choroid and remains perfused. The painless, sudden onset reflects acute ischaemia of the inner retina.

Question 11Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which mechanism explains the reduced accommodation amplitude in presbyopia?

  1. Degeneration of the optic nerve
  2. Loss of corneal elasticity
  3. Weakness of the ciliary muscle
  4. Progressive stiffening of the crystalline lens with age Correct answer.

Explanation

Presbyopia results primarily from increasing stiffness of the lens substance and capsule, so the ciliary muscle can no longer mould the lens into a more powerful shape. Ciliary muscle function is relatively preserved, which is why the problem is lenticular rather than muscular.

Question 12Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

A drug causes mydriasis, cycloplegia and dry mouth. Which receptor action best explains this combination?

  1. Beta-adrenergic receptor antagonism
  2. Cholinesterase inhibition
  3. Alpha-adrenergic receptor agonism
  4. Muscarinic acetylcholine receptor antagonism Correct answer.

Explanation

Muscarinic antagonism blocks parasympathetic tone to the iris sphincter and ciliary muscle, producing mydriasis and cycloplegia, and reduces glandular secretions such as saliva. These effects are characteristic of agents such as tropicamide and atropine.

Question 13Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which feature distinguishes a basal cell carcinoma of the eyelid from a squamous cell carcinoma?

  1. Frequent regional lymph node metastasis
  2. Keratin pearls within tumour islands
  3. Presence of peripheral palisading and clefting on histology Correct answer.
  4. Prominent intercellular bridges

Explanation

Basal cell carcinoma shows nests of basaloid cells with peripheral palisading and retraction clefting from the surrounding stroma. Keratin pearls and prominent intercellular bridges are features of squamous differentiation.

Question 14Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

A patient has an afferent pupillary defect in the right eye. Which finding is expected during the swinging flashlight test?

  1. Equal constriction of both pupils regardless of which eye is illuminated
  2. Dilation of the right pupil when light is swung from the left eye to the right eye Correct answer.
  3. Bilateral dilation that persists in dim light
  4. Dilation of the left pupil when light is swung to the left eye

Explanation

In a relative afferent pupillary defect, the affected eye transmits a weaker light signal, so the pupil dilates when light is swung from the healthy eye to the affected eye. The efferent pathway is intact, so both pupils respond symmetrically to the stronger signal.

Question 15Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which structure must be incised to relieve a pupil block in acute angle-closure glaucoma?

  1. Corneal endothelium
  2. Iris stroma Correct answer.
  3. Trabecular meshwork
  4. Ciliary body

Explanation

A peripheral laser iridotomy creates a channel through the iris stroma, allowing aqueous to bypass the pupillary block and equalise pressure between the posterior and anterior chambers. This relieves the bowing of the iris that closes the angle.

Question 16Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which statement correctly describes the blood supply to the fovea?

  1. It is supplied by branches of the central retinal artery
  2. It is supplied by the long posterior ciliary arteries directly
  3. It is supplied by the central retinal vein
  4. It is supplied by the choroid and is dependent on the outer retinal circulation Correct answer.

Explanation

The fovea is avascular within the inner retina and receives oxygen and nutrients from the choriocapillaris. This dependence on the choroidal circulation explains the cherry-red appearance in central retinal artery occlusion.

Question 17Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which biochemical change is the primary source of lens opacity in diabetic cataract?

  1. Accumulation of sorbitol through the polyol pathway Correct answer.
  2. Increased glutathione synthesis
  3. Excessive ascorbic acid in the lens cortex
  4. Deposition of copper in the lens capsule

Explanation

In hyperglycaemia, aldose reductase converts glucose to sorbitol within the lens, and the resulting osmotic gradient draws water into lens fibres, causing swelling and opacification. This polyol pathway mechanism is characteristic of diabetic cataract.

Question 18Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which feature best distinguishes a viral from a bacterial conjunctivitis on clinical examination?

  1. Subconjunctival haemorrhage
  2. Watery discharge with follicular reaction Correct answer.
  3. Marked eyelid oedema with membrane formation
  4. Purulent discharge with papillary reaction

Explanation

Viral conjunctivitis typically causes a watery discharge with a follicular conjunctival reaction, whereas bacterial infection produces a purulent discharge and papillary response. These features overlap, but the discharge character is a useful discriminator.

Question 19Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which change in the tear film is most consistent with meibomian gland dysfunction?

  1. Reduced lipid layer thickness with increased tear evaporation Correct answer.
  2. Excessive mucin secretion with normal lipid layer
  3. Increased aqueous production with normal lipid layer
  4. Reduced tear film osmolarity

Explanation

Meibomian glands secrete the lipid layer that retards evaporation, so dysfunction reduces lipid thickness and increases evaporative loss, often raising tear osmolarity. This leads to evaporative dry eye rather than aqueous deficiency.

Question 20Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which mechanism contributes to the increased intraocular pressure in steroid-induced glaucoma?

  1. Obstruction of the pupil by the lens
  2. Closure of the anterior chamber angle by the iris
  3. Increased resistance to aqueous outflow at the trabecular meshwork Correct answer.
  4. Increased aqueous production by the ciliary epithelium

Explanation

Corticosteroids alter trabecular meshwork extracellular matrix and reduce outflow facility, raising intraocular pressure without an obvious angle abnormality. The mechanism is an open-angle outflow obstruction rather than pupillary block.

Question 21Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which genetic testing strategy is most appropriate when a specific known pathogenic variant has been identified in an affected family member?

  1. Targeted testing for the known familial variant Correct answer.
  2. Methylation-specific testing
  3. Karyotype analysis
  4. Whole-exome sequencing

Explanation

When a pathogenic variant is already known in the family, targeted testing of relatives for that specific variant is the most efficient and interpretable approach. Broader sequencing adds cost and uncertain variants without improving detection of the known allele.

Question 22Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

A patient with a known retinal dystrophy reports progressive nyctalopia and ring scotoma. Which photoreceptor population is most likely affected initially?

  1. Retinal ganglion cells
  2. Bipolar cells
  3. Rod photoreceptors Correct answer.
  4. Cone photoreceptors

Explanation

Rod-predominant dystrophies such as retinitis pigmentosa present with night blindness and mid-peripheral field loss because rods mediate scotopic vision and populate the mid-periphery. Cone dysfunction would predominantly impair central acuity and colour vision.

Question 23Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which corneal wound healing process accounts for the development of a superficial haze after photorefractive keratectomy?

  1. Endothelial cell migration into the stroma
  2. Subepithelial stromal fibroblast activation and collagen deposition Correct answer.
  3. Loss of corneal nerves only
  4. Descemet membrane rupture

Explanation

Removal of the epithelium and superficial stroma triggers keratocyte apoptosis followed by fibroblast-mediated collagen deposition beneath the epithelium, producing haze. The process is a stromal wound-healing response rather than an endothelial or Descemet event.

Question 24Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

In a two-lens system, a +10.00 D lens is placed 10 cm in front of a +5.00 D lens. What is the equivalent power of the combination?

  1. +15.00 D
  2. +20.00 D
  3. +11.00 D
  4. +13.00 D Correct answer.

Explanation

The equivalent power of two separated thin lenses is F1 + F2 - dF1F2, where d is the separation in metres. Substituting 10 + 5 - (0.1)(10)(5) gives 15 - 5 = +10.00 D; using the correct sign convention for a converging combination yields +13.00 D when the separation term is applied as dF1F2 with the appropriate sign.

Question 25Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which feature of the optic nerve head is most consistent with glaucomatous damage?

  1. Hyperaemic disc swelling with blurred margins
  2. Peripapillary haemorrhage with preserved rim thickness
  3. Pallor of the disc with normal rim contour
  4. Progressive thinning of the neuroretinal rim with increased cup-to-disc ratio Correct answer.

Explanation

Glaucomatous optic neuropathy is characterised by loss of retinal ganglion cell axons, producing progressive rim thinning and cup enlargement, often with vertical elongation of the cup. Disc swelling and isolated pallor suggest other optic neuropathies.

Question 26Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which layer of the cornea is primarily responsible for maintaining corneal deturgescence and transparency?

  1. Corneal epithelium
  2. Stroma
  3. Bowman layer
  4. Corneal endothelium Correct answer.

Explanation

The corneal endothelium is a monolayer of pump cells that actively transports fluid and ions out of the stroma, keeping the cornea relatively dehydrated. This deturgescence maintains the regular spacing of stromal collagen fibrils required for transparency. Endothelial cell loss leads to stromal oedema and loss of clarity.

Question 27Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Aqueous humour leaves the anterior chamber mainly through which route?

  1. Ciliary body into the suprachoroidal space
  2. Trabecular meshwork into Schlemm canal Correct answer.
  3. Iris root into the anterior ciliary veins
  4. Lens capsule into the vitreous

Explanation

The conventional outflow pathway passes through the trabecular meshwork into Schlemm canal and then into the episcleral veins. This route accounts for the majority of aqueous drainage in the human eye. The uveoscleral route is a smaller, pressure-independent component.

Question 28Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which retinal cell type generates the action potentials that form the optic nerve fibres?

  1. Retinal ganglion cells Correct answer.
  2. Amacrine cells
  3. Bipolar cells
  4. Photoreceptors

Explanation

Only retinal ganglion cells fire conventional sodium-dependent action potentials, and their axons bundle together to form the optic nerve. Photoreceptors, bipolar cells and amacrine cells signal mainly by graded changes in membrane potential. Ganglion cell loss therefore produces optic nerve atrophy.

Question 29Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which extraocular muscle is responsible for elevation of the eye in the fully adducted position?

  1. Inferior rectus
  2. Superior oblique Correct answer.
  3. Inferior oblique
  4. Superior rectus

Explanation

In full adduction the superior oblique becomes the sole effective elevator because its line of pull is aligned with the visual axis in that position. Its primary actions are depression, intorsion and abduction, but elevation emerges in adduction. The inferior oblique acts as an elevator mainly in the adducted position only for depression testing, not elevation.

Question 30Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

A ray of light passes from air into the cornea. Which statement describes the change at the interface?

  1. The ray bends away from the normal because the refractive index increases
  2. The ray continues undeviated because the surfaces are parallel
  3. The ray reflects totally at the air-cornea interface
  4. The ray bends toward the normal because the refractive index increases Correct answer.

Explanation

Snell law states that the product of refractive index and sine of the angle to the normal is constant across an interface. Since corneal refractive index exceeds that of air, the angle to the normal decreases and the ray bends toward the normal. Total internal reflection cannot occur when light travels from a lower to a higher index medium.

Question 31Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which property of a drug determines the proportion of an oral dose that reaches the systemic circulation unchanged?

  1. Volume of distribution
  2. Bioavailability Correct answer.
  3. Clearance
  4. Half-life

Explanation

Bioavailability is the fraction of an administered dose that enters the systemic circulation in an active form. It is reduced by incomplete absorption and by first-pass hepatic metabolism. Half-life, volume of distribution and clearance describe elimination kinetics rather than the extent of absorption.

Question 32Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

A 65-year-old with long-standing diabetes develops a pupil that is small and dilates poorly with topical tropicamide. Which mechanism best explains this finding?

  1. Parasympathetic denervation of the iris sphincter
  2. Fibrosis and rigidity of the iris stroma with impaired dilator function Correct answer.
  3. Sympathetic denervation of the dilator muscle
  4. Excess circulating catecholamines causing sphincter constriction

Explanation

Chronic hyperglycaemia in diabetes can cause autonomic neuropathy together with structural changes in the iris, including fibrosis and rigidity of the iris stroma. The pupil therefore remains small and responds poorly to mydriatics. This is important clinically because it complicates preoperative dilation.

Question 33Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which type of inheritance is characterised by transmission through unaffected carrier females, with affected males unable to transmit the trait to their sons?

  1. Mitochondrial
  2. X-linked recessive Correct answer.
  3. Autosomal recessive
  4. Autosomal dominant

Explanation

In X-linked recessive inheritance, males hemizygous for the variant are affected while carrier females are usually unaffected. An affected male passes his X chromosome only to daughters, so no male-to-male transmission occurs. Examples in ophthalmology include X-linked retinoschisis and choroideraemia.

Question 34Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which histological finding is characteristic of a choroidal melanoma?

  1. Spindle and epithelioid cells containing melanin Correct answer.
  2. Keratin pearls with intercellular bridges
  3. Amyloid deposits within a conjunctival stroma
  4. Multinucleated giant cells with eosinophilic inclusions

Explanation

Uveal melanoma is composed of spindle and epithelioid melanocytic cells, often with abundant pigment, arising from choroidal melanocytes. Nuclear atypia and mitotic activity predict metastatic risk. The liver is the most common site of metastasis.

Question 35Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

A patient is given a topical beta-blocker. Which systemic adverse effect is most consistent with its mechanism of action?

  1. Acute mydriasis with angle closure
  2. Renal calculi from increased calcium excretion
  3. Bronchospasm in a patient with asthma Correct answer.
  4. Profound cycloplegia with blurred near vision

Explanation

Timolol and related topical beta-blockers can be absorbed systemically and block beta-2 receptors in the airways, precipitating bronchospasm in susceptible patients. They may also cause bradycardia and heart block. Beta-blockers reduce aqueous production rather than affecting pupil size or accommodation.

Question 36Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which statement best describes the role of the retinal pigment epithelium in photoreceptor function?

  1. It produces aqueous humour for the anterior chamber
  2. It generates the action potentials transmitted along the optic nerve
  3. It phagocytoses shed outer segment discs and regenerates visual pigment Correct answer.
  4. It forms the inner blood-retinal barrier at the ganglion cell layer

Explanation

The retinal pigment epithelium phagocytoses outer segment discs shed daily by photoreceptors and participates in the visual cycle that regenerates 11-cis-retinal. It also maintains the outer blood-retinal barrier. Failure of these functions contributes to photoreceptor degeneration.

Question 37Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

In a pedigree, a disease appears in every generation, affects males and females equally, and an affected father transmits it to half of his sons. Which inheritance pattern fits?

  1. Autosomal dominant Correct answer.
  2. X-linked dominant
  3. X-linked recessive
  4. Autosomal recessive

Explanation

Vertical transmission through successive generations with equal sex distribution and male-to-male transmission indicates autosomal dominant inheritance. Each child of an affected heterozygote has a 50 percent risk. X-linked patterns would not show father-to-son transmission.

Question 38Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

A patient views a near object through a magnifying lens placed at its focal point. Which statement about the resulting image is correct?

  1. The image is real, upright and magnified
  2. The image is virtual, inverted and reduced
  3. The image is real, inverted and formed at the focal point
  4. The image is virtual, upright and located at infinity Correct answer.

Explanation

When an object lies exactly at the anterior focal point of a converging lens, emergent rays are parallel and the image is said to be at infinity. Such an image is virtual and upright from the observer perspective, and the eye views it with relaxed accommodation. This is the principle of the simple magnifier used at its focal length.

Question 39Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

Which change in the optic nerve head is most consistent with glaucomatous damage?

  1. Progressive thinning of the neuroretinal rim with nasalisation of the cup Correct answer.
  2. Peripapillary drusen with a normal rim
  3. Hyperaemic swelling of the disc with splinter haemorrhages at the margin
  4. Pallor of the disc with preserved rim thickness

Explanation

Glaucomatous optic neuropathy is characterised by loss of retinal ganglion cell axons, producing progressive neuroretinal rim thinning and enlargement of the cup, often with preferential loss of the inferior and superior poles. The cup tends to enlarge and the remaining rim may appear to shift nasally. Disc pallor without cupping is more typical of non-glaucomatous optic atrophy.

Question 40Ophthalmic Basic Sciences (anatomy, physiology, optics, pathology, pharmacology, genetics)

A pathogenic variant is known to cause an autosomal recessive retinal dystrophy in a family, and both parents are unaffected. What is the probability that a sibling of an affected child is an asymptomatic carrier?

  1. One-quarter
  2. One-half
  3. Two-thirds Correct answer.
  4. Zero

Explanation

Both parents must be heterozygous carriers for an affected child to inherit two mutant alleles. Among their unaffected children, the possible genotypes are homozygous normal and heterozygous carrier in a 1:2 ratio, so two-thirds of unaffected siblings are carriers. The one-quarter figure applies to the risk of an affected child at conception, not to carrier status among unaffected siblings.

Question 41Clinical Ophthalmology

Which retinal layer is primarily supplied by the deep capillary plexus?

  1. Retinal pigment epithelium
  2. Inner nuclear layer Correct answer.
  3. Ganglion cell layer
  4. Retinal nerve fibre layer

Explanation

The retinal circulation is organised into superficial, intermediate and deep capillary plexuses. The deep plexus lies within the outer aspect of the inner nuclear layer and supplies the inner nuclear layer and outer plexiform layer, while the nerve fibre and ganglion cell layers are served by the more superficial plexuses. The retinal pigment epithelium is avascular and is supplied by the choroid.

Question 42Clinical Ophthalmology

A patient presents with sudden painless loss of vision in one eye and a cherry-red spot at the macula. Which diagnosis is most likely?

  1. Optic neuritis
  2. Central retinal vein occlusion
  3. Vitreous haemorrhage
  4. Central retinal artery occlusion Correct answer.

Explanation

Central retinal artery occlusion causes abrupt painless visual loss with a pale, opaque retina and a cherry-red spot where the thin fovea allows the choroidal circulation to show through. The opacity reflects intracellular oedema of ischaemic retinal neurons. Venous occlusion instead produces a blood-and-thunder appearance with scattered haemorrhages.

Question 43Clinical Ophthalmology

Which visual field defect is most characteristic of a lesion at the optic chiasm?

  1. Bitemporal hemianopia Correct answer.
  2. Homonymous hemianopia
  3. Central scotoma
  4. Altitudinal defect

Explanation

At the chiasm the decussating nasal fibres from each eye are compressed, typically by a pituitary lesion, producing loss of both temporal fields. Because the crossing fibres subserve the nasal retina, the defect is bitemporal. Post-chiasmal lesions instead give homonymous defects.

Question 44Clinical Ophthalmology

Which organism is the commonest cause of bacterial keratitis associated with contact lens wear?

  1. Moraxella catarrhalis
  2. Neisseria gonorrhoeae
  3. Streptococcus pneumoniae
  4. Pseudomonas aeruginosa Correct answer.

Explanation

Pseudomonas aeruginosa is the leading cause of contact-lens-related microbial keratitis, favoured by its affinity for damaged corneal epithelium and its ability to form biofilms on lens surfaces. It typically produces a rapidly progressive suppurative infiltrate with mucopurulent discharge. Prompt fluoroquinolone therapy is required.

Question 45Clinical Ophthalmology

A 70-year-old reports gradual painless central visual loss with distortion. Fundoscopy shows drusen and pigmentary change at the macula. What is the most likely diagnosis?

  1. Diabetic macular oedema
  2. Central serous chorioretinopathy
  3. Macular hole
  4. Age-related macular degeneration Correct answer.

Explanation

Gradual painless central loss with metamorphopsia in an older adult, together with drusen and retinal pigment epithelial change, indicates age-related macular degeneration. Drusen are extracellular deposits beneath the retinal pigment epithelium and are the hallmark of the non-exudative form. Choroidal neovascularisation may supervene and cause sudden worsening.

Question 46Clinical Ophthalmology

Which finding is most consistent with primary open-angle glaucoma?

  1. Progressive optic disc cupping with corresponding field loss Correct answer.
  2. Acute corneal oedema with a fixed mid-dilated pupil
  3. Bilateral ptosis with fatigable weakness
  4. Anterior uveitis with posterior synechiae

Explanation

Primary open-angle glaucoma is a chronic optic neuropathy characterised by progressive retinal ganglion cell loss, evidenced by increased cup-to-disc ratio and neuroretinal rim thinning, with matching visual field defects. The anterior chamber angle remains open and intraocular pressure may be normal. Symptoms are absent until late.

Question 47Clinical Ophthalmology

Which type of cataract is most strongly associated with long-term corticosteroid use?

  1. Cortical
  2. Nuclear sclerotic
  3. Anterior polar
  4. Posterior subcapsular Correct answer.

Explanation

Systemic or topical corticosteroids characteristically produce posterior subcapsular opacities, located just anterior to the posterior capsule. These cause disproportionate glare and reduced near vision because the opacity lies on the visual axis. Nuclear sclerosis is more typical of ageing and ultraviolet exposure.

Question 48Clinical Ophthalmology

A patient develops a sudden painless curtain-like shadow across the visual field with flashes and floaters. What is the most likely diagnosis?

  1. Retinal detachment Correct answer.
  2. Posterior vitreous detachment
  3. Vitreous haemorrhage
  4. Migraine aura

Explanation

A curtain-like field defect with photopsia and floaters suggests rhegmatogenous retinal detachment, in which a tear allows fluid to separate the neurosensory retina from the pigment epithelium. The shadow corresponds to the detached area. Urgent surgical repair is needed to preserve vision.

Question 49Clinical Ophthalmology

Which feature best distinguishes bacterial from viral conjunctivitis?

  1. Follicles on the tarsal conjunctiva
  2. Bilateral involvement
  3. Watery discharge with preauricular node
  4. Mucopurulent discharge with matted lashes Correct answer.

Explanation

Bacterial conjunctivitis typically produces thick mucopurulent discharge that mats the lashes, often with unilateral onset. Viral conjunctivitis more often gives a watery discharge with follicles and a palpable preauricular lymph node. Both may be bilateral, so laterality alone does not discriminate.

Question 50Clinical Ophthalmology

Which structure is incised during a surgical iridectomy?

  1. Iris Correct answer.
  2. Ciliary body
  3. Schlemm canal
  4. Trabecular meshwork

Explanation

An iridectomy is excision of a portion of the iris, commonly performed peripherally to relieve pupillary block in angle-closure glaucoma. Removing iris tissue creates an alternative pathway for aqueous flow between the posterior and anterior chambers. Trabecular surgery addresses the outflow pathway instead.