Anatomy and Physiology of Sclera — MCQs
Type I collagen is present in all EXCEPT:
An example of a scleroprotein is
Normal intraocular pressure is typically in the range of:
Blue sclera is associated with:
A patient presents with a nodular swelling near the limbus, which does not blanch with topical vasoconstrictors and recurs after treatment. Based on the image and clinical presentation, what is the most probable diagnosis?
A 22-year-old Air-force test pilot presents after flying a sortie. He reports no pain or vision changes. Eye examination reveals a localized red patch on the sclera. What is the most likely diagnosis?
Blue sclera is seen in all of the following conditions except:
Evisceration is removal of which layer of eyeball?
Shortening of 2 mm of axial length of the eyeball causes?
Which of the following conditions is associated with posterior staphyloma?
Anatomy and Physiology of Sclera Indian Medical PG Practice Questions and MCQs
Question 1: Type I collagen is present in all EXCEPT:
- A. Ligament
- B. Aponeurosis
- C. Cartilage (Correct Answer)
- D. Bone
Explanation: Cartilage - **Type II collagen** is the predominant collagen found in hyaline and elastic cartilage (the typical forms of cartilage), providing their characteristic tensile strength and resilience [2]. - Type I collagen is NOT the primary collagen in cartilage, making this the correct answer. - Note: Fibrocartilage is a specialized form that does contain Type I collagen, but standard cartilage refers to hyaline and elastic types. *Ligament* - **Type I collagen** is the primary structural component of ligaments, providing high tensile strength to connect bones and stabilize joints. - Its presence allows ligaments to withstand significant pulling forces without stretching excessively. *Aponeurosis* - **Type I collagen** is abundant in aponeuroses, which are flat sheet-like tendons that connect muscles to bones or other muscles. - This type of collagen provides the necessary tensile strength for these broad connective tissues. *Bone* - **Type I collagen** is the most abundant collagen in bone matrix, accounting for approximately 90% of its organic content [1]. - It forms a robust scaffold that gives bone its flexibility and tensile strength, working in conjunction with mineralized components like hydroxyapatite [1].
Question 2: An example of a scleroprotein is
- A. Zein
- B. Glutenin
- C. Ovoglobulin
- D. Keratin (Correct Answer)
Explanation: ***Keratin*** - **Keratin** is a fibrous, structural protein and is a prime example of a **scleroprotein** (also known as a **fibrous protein**). - It provides strength and structural integrity to tissues like hair, nails, and the outer layer of skin. *Zein* - **Zein** is a prolamine protein found in corn. - It is an **alcohol-soluble protein** and is not classified as a scleroprotein. *Glutenin* - **Glutenin** is a major storage protein found in wheat. - It is classified as a **globulin** and contributes to the elasticity of dough, but is not a scleroprotein. *Ovoglobulin* - **Ovoglobulin** refers to a group of globular proteins found in egg white. - These are typically **soluble in water** or dilute salt solutions and do not share the fibrous, structural characteristics of scleroproteins.
Question 3: Normal intraocular pressure is typically in the range of:
- A. 2.1-6 mm Hg
- B. 7-14 mm Hg
- C. 10-21 mm Hg (Correct Answer)
- D. 16-32 mm Hg
Explanation: ***10-21 mm Hg*** - This range is widely accepted as the **normal intraocular pressure (IOP)** in healthy individuals. - Maintaining IOP within this range is crucial for preventing damage to the **optic nerve** and conditions like **glaucoma**. *2.1-6 mm Hg* - This range is significantly **lower** than the normal physiological IOP. - Pressures in this range could indicate conditions like **hypotony**, which can lead to vision problems. *7-14 mm Hg* - While closer to the normal range, this range is still generally considered to be at the **lower end of normal** or slightly below. - Many individuals would fall within 10-21 mm Hg, making this a less accurate representation of the typical normal range. *16-32 mm Hg* - The upper part of this range (above 21 mm Hg) is considered **elevated IOP**, a significant risk factor for **glaucoma**. - Pressures above 21 mm Hg require closer monitoring and potentially treatment to prevent **optic nerve damage**.
Question 4: Blue sclera is associated with:
- A. Ehlers-Danlos syndrome
- B. Buphthalmos
- C. Marfan's syndrome
- D. Osteogenesis imperfecta (Correct Answer)
Explanation: ***Osteogenesis imperfecta*** - **Osteogenesis imperfecta** (brittle bone disease) is the **MOST CLASSIC** condition associated with blue sclera. - Caused by a defect in **Type I collagen synthesis**, which is a major structural component of the sclera. - The deficiency in functional collagen leads to an **abnormally thin and translucent sclera**, allowing the underlying **choroidal pigment** to show through, giving it a characteristic blue appearance. - Blue sclera is seen in **80-90% of patients** with Type I osteogenesis imperfecta. *Buphthalmos* - **Buphthalmos** (congenital glaucoma) can occasionally show bluish sclera due to scleral thinning from increased intraocular pressure. - However, the primary findings are **corneal enlargement, corneal edema**, and increased eye size, not blue sclera as a defining feature. *Marfan's syndrome* - **Marfan's syndrome** is a connective tissue disorder caused by **fibrillin-1** defects. - Classic ocular features include **ectopia lentis** (lens dislocation), high myopia, and retinal detachment risk. - Blue sclera is **NOT a recognized clinical feature** of Marfan's syndrome. *Ehlers-Danlos syndrome* - This connective tissue disorder can present with blue sclera due to collagen abnormalities. - However, it is **less common** than osteogenesis imperfecta as a cause of blue sclera.
Question 5: A patient presents with a nodular swelling near the limbus, which does not blanch with topical vasoconstrictors and recurs after treatment. Based on the image and clinical presentation, what is the most probable diagnosis?
- A. Scleritis with rheumatoid arthritis (Correct Answer)
- B. Episcleritis with rheumatoid arthritis
- C. Pinguecula
- D. Dry eye
Explanation: ***Scleritis with rheumatoid arthritis*** - The image shows **deep, violaceous conjunctival injection** with surrounding edema and a nodular appearance near the limbus, consistent with **nodular scleritis**. Scleritis is inflammation of the sclera, often characterized by severe pain and association with systemic autoimmune diseases like **rheumatoid arthritis**, which can cause destructive lesions and recurrence. - The characteristic **deep vessel engorgement that does not blanch with phenylephrine** and the history of recurrence further support scleritis. *Episcleritis with rheumatoid arthritis* - Episcleritis presents with a **more superficial, bright red injection** involving the episclera, which generally **blanches with topical phenylephrine** and is less painful than scleritis. - While episcleritis can be associated with rheumatoid arthritis, the clinical features described (nodular swelling, deep injection) are more typical of scleritis. *Pinguecula* - A pinguecula is a **yellowish patch or bump** on the conjunctiva, typically on the nasal side of the eye, that is **not inflamed** unless irritated. - It consists of **degenerated collagen fibers** and elastic tissue, and does not present with the diffuse, deep vascular injection seen in the image. *Dry eye* - Dry eye is characterized by **ocular dryness, irritation, and sometimes a foreign body sensation**, but it typically causes **diffuse conjunctival hyperemia** rather than a localized, nodular, deep inflammation with surrounding edema as shown. - While dry eye can be associated with autoimmune diseases, its appearance is not consistent with the depicted nodular lesion.
Question 6: A 22-year-old Air-force test pilot presents after flying a sortie. He reports no pain or vision changes. Eye examination reveals a localized red patch on the sclera. What is the most likely diagnosis?
- A. Hyphema
- B. Subconjunctival hemorrhage (Correct Answer)
- C. Keratitis
- D. Allergic conjunctivitis
Explanation: ***Subconjunctival hemorrhage*** - A **localized red patch on the sclera** with no pain or vision changes, especially after activities that can increase venous pressure (like flying a sortie or straining), is characteristic of a **subconjunctival hemorrhage**. - It results from the rupture of small blood vessels beneath the conjunctiva, causing blood to pool. *Hyphema* - This involves blood in the **anterior chamber of the eye**, usually visible as a fluid level and often causing pain or blurred vision. - It typically results from **trauma** and is not described as a localized red patch on the sclera. *Keratitis* - **Keratitis** is inflammation of the cornea, causing pain, redness, photophobia, and often blurred vision. - The patient has no pain or vision changes, and the presentation is a localized scleral patch, not diffuse corneal involvement. *Allergic conjunctivitis* - Presents with **redness**, itching, tearing, and often bilateral involvement, sometimes with discharge. - The description of a solitary, localized red patch without other allergic symptoms makes this diagnosis unlikely.
Question 7: Blue sclera is seen in all of the following conditions except:
- A. Marfan's syndrome
- B. Osteogenesis imperfecta
- C. Keratoconus (Correct Answer)
- D. Rheumatoid arthritis
Explanation: ***Keratoconus*** - Keratoconus is a progressive eye disease in which the normally round cornea thins and begins to bulge into a cone-like shape, leading to **vision distortion**. - Blue sclera is **not a feature** of keratoconus. This is a **corneal condition** that does not affect the sclera. - Blue sclera, seen in the other conditions listed, occurs due to thinning of the sclera, making the underlying choroidal pigment visible. *Marfan's syndrome* - Patients with Marfan's syndrome can have blue sclera due to the **thinning of collagen** in the scleral tissue, allowing the underlying choroid to show through. - This connective tissue disorder affects multiple body systems, including the skeletal, cardiovascular, and ocular systems, with features like **arachnodactyly** and **aortic root dilation**. *Osteogenesis imperfecta* - Often referred to as **brittle bone disease**, osteogenesis imperfecta is characterized by defective **type I collagen synthesis**, which also affects the sclera. - The sclera becomes thin and translucent, revealing the underlying choroidal pigment, thus appearing **blue**. *Rheumatoid arthritis* - In rheumatoid arthritis, particularly with severe or long-standing disease, the sclera can become thinned due to **scleritis** or **scleromalacia perforans**. - This thinning can lead to a **blue discoloration** of the sclera, making the underlying choroid visible.
Question 8: Evisceration is removal of which layer of eyeball?
- A. Middle and inner (Correct Answer)
- B. All the layers of eyeball
- C. Outer and inner
- D. Outer and middle
Explanation: ***Middle and inner*** - **Evisceration** involves the surgical removal of the internal contents of the eyeball, which include components derived from the **middle (uveal) and inner (retinal) layers**. - The **sclera** (outermost layer) and **extraocular muscles** are preserved, allowing for a more natural prosthetic eye fit. *All the layers of eyeball* - This describes **enucleation**, where the entire eyeball is removed including all three layers (sclera, choroid/ciliary body/iris, and retina). - Enucleation is a more extensive procedure than evisceration, typically performed for intraocular tumors or severe trauma where preservation of the sclera isn't possible. *Outer and inner* - This option is incorrect because the **outer layer (sclera)** is specifically preserved in evisceration. - Removing the outer layer would lead to a more destructive procedure, inconsistent with the definition of evisceration. *Outer and middle* - This option is incorrect because the **outer layer (sclera)** is preserved during evisceration, while the entire **inner layer (retina)** is removed. - The middle layer (uvea) is removed, but this option inaccurately states the fate of the outer and inner layers.
Question 9: Shortening of 2 mm of axial length of the eyeball causes?
- A. 3D myopia
- B. 2D myopia
- C. 6D hypermetropia (Correct Answer)
- D. 1D hypermetropia
Explanation: ***6D hypermetropia*** - A 1 mm shortening of the **axial length** of the eyeball typically results in approximately **3 diopters** of hypermetropia. - Therefore, a 2 mm shortening would cause **6 diopters** (2 mm x 3 D/mm) of hypermetropia. *3D myopia* - Myopia (nearsightedness) is caused by an **eyeball that is too long** or a cornea that is too steeply curved, not by a shortened axial length. - A 2 mm shortening would cause **hypermetropia** (farsightedness), not myopia. *2D myopia* - This option incorrectly identifies both the **type of refractive error** (myopia instead of hypermetropia) and the magnitude of the change. - Shortening of the axial length makes the eye effectively **farsighted**, not nearsighted. *1D hypermetropia* - While reflecting the correct type of refractive error (hypermetropia), the **magnitude is incorrect**. - A 1 mm change in axial length results in about 3 diopters, so 2 mm would be **6 diopters**, not 1 diopter.
Question 10: Which of the following conditions is associated with posterior staphyloma?
- A. Pathological myopia (Correct Answer)
- B. Uveoscleritis
- C. Pseudocornea
- D. Angle closure glaucoma
Explanation: **Explanation:** **Posterior staphyloma** is a localized bulging of the weak, thinned sclera lined by uveal tissue, occurring posterior to the equator of the eye. 1. **Why Pathological Myopia is correct:** Pathological (high) myopia is the most common cause of posterior staphyloma. Progressive elongation of the anteroposterior axis of the eyeball leads to excessive stretching and thinning of the posterior pole. This results in an ectasia (bulging) of the sclera, typically at the macula or around the optic nerve head. It is a hallmark feature used to differentiate pathological myopia from simple myopia. 2. **Why the other options are incorrect:** * **Uveoscleritis:** While inflammation can weaken the sclera, it more commonly leads to **ciliary or anterior staphyloma** due to the weakening of the sclera in the limbal or ciliary body region. * **Pseudocornea:** This is a clinical feature of a **total corneal staphyloma**, where a perforated cornea is replaced by organized iris tissue and fibrous tissue, not a posterior scleral bulge. * **Angle closure glaucoma:** Chronic or absolute glaucoma is associated with **equatorial staphyloma** (where the sclera is perforated by vortex veins) or ciliary staphyloma, but not typically posterior staphyloma. **High-Yield Pearls for NEET-PG:** * **Types of Staphyloma:** * **Anterior (Corneal):** Due to corneal perforation/sloughing. * **Ciliary:** Occurs in the ciliary zone (2–3 mm behind limbus). Common in absolute glaucoma. * **Equatorial:** Occurs at the equator where vortex veins exit. * **Posterior:** Occurs at the posterior pole. * **Diagnosis:** Posterior staphyloma is best visualized using **B-scan ultrasonography** or optical coherence tomography (OCT). * **Complication:** It is a major risk factor for myopic macular degeneration and retinal detachment.
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free