Phakic IOLs — MCQs
An 80-year-old patient complains of pain, redness, and diminished vision in the left eye. On examination, the intraocular pressure (IOP) in the right eye is 16 mmHg, while the left eye shows 50 mmHg. The left eye also exhibits deep anterior chamber flare and a white cataract. What is the most likely diagnosis?
In which of the following conditions does IOL implantation after cataract surgery require the greatest caution and specialized management?
On measuring 3.5 to 4 mm posterior to the limbus in a phakic eye and plunging a 30 gauge needle perpendicular to sclera, you pass through
Constantly changing refractive error is seen in:
Which keratometry reading is most accurate in post-LASIK eyes for IOL power calculation?
In which of the following conditions is the intraocular pressure very high, and inflammation is minimal?
Phacoemulsification incision is at what location?
Which condition is associated with pseudoproptosis?
The image shows a funnel shaped anterior chamber (deeper in the center and narrow in the periphery), which is seen in angle closure glaucoma. This is caused by:
Which of the following statements about congenital glaucoma is incorrect?
Phakic IOLs Indian Medical PG Practice Questions and MCQs
Question 1: An 80-year-old patient complains of pain, redness, and diminished vision in the left eye. On examination, the intraocular pressure (IOP) in the right eye is 16 mmHg, while the left eye shows 50 mmHg. The left eye also exhibits deep anterior chamber flare and a white cataract. What is the most likely diagnosis?
- A. Central retinal artery occlusion (CRAO)
- B. Fuchs' heterochromic iridocyclitis
- C. Malignant glaucoma
- D. Phacolytic glaucoma (Correct Answer)
Explanation: ***Phacolytic glaucoma*** - The combination of **extremely high intraocular pressure** (50 mmHg) in the left eye, along with a **mature (white) cataract** and **deep anterior chamber flare**, is highly suggestive of phacolytic glaucoma. - This condition occurs when **lens proteins leak** from a hypermature cataract, triggering a macrophagic inflammatory response that **clogs the trabecular meshwork**, leading to an acute rise in IOP. *Central retinal artery occlusion (CRAO)* - While CRAO causes acute, profound **vision loss** in one eye, it is generally associated with a **normal or low IOP**, not the extremely high pressure seen in the left eye. - Fundoscopic examination would typically reveal a **cherry-red spot** and **pale retina**, which are not described. *Fuchs' heterochromic iridocyclitis* - This condition is characterized by **chronic, low-grade anterior uveitis** and often leads to **heterochromia** (different colored irises) and **secondary glaucoma**. - However, it typically presents with **mild IOP elevation** (if at all) and not the acute, markedly high pressure and visible white cataract with flare described here. *Malignant glaucoma* - Malignant glaucoma (also known as aqueous misdirection) presents with an **elevated IOP** and is characterized by a **shallow or flat anterior chamber**, often in the presence of a pupillary block mechanism. - The patient's left eye is described as having a **deep anterior chamber** with flare, which contradicts the typical findings of malignant glaucoma.
Question 2: In which of the following conditions does IOL implantation after cataract surgery require the greatest caution and specialized management?
- A. Fuchs' heterochromic iridocyclitis
- B. Psoriatic arthritis
- C. Reiter's syndrome
- D. Juvenile rheumatoid arthritis (Correct Answer)
Explanation: ***Juvenile rheumatoid arthritis*** - Patients with **juvenile rheumatoid arthritis (JRA)**, particularly those with **pauciarticular JRA** and **ANA positivity**, are at high risk for developing chronic uveitis, which can lead to significant cataract formation and severe postoperative complications. - Due to the high risk of severe postoperative inflammation, glaucoma, and vision loss, IOL implantation in JRA patients requires extensive preoperative optimization of inflammation and careful intraoperative/postoperative management. *Fuchs' heterochromic iridocyclitis* - This condition presents with chronic, low-grade, **non-granulomatous anterior uveitis** and often leads to cataract formation. - While IOL implantation in these patients is generally well-tolerated, it does not pose the same high risk of severe postoperative inflammation and complications as seen in JRA-associated uveitis. *Psoriatic arthritis* - Psoriatic arthritis can be associated with acute anterior uveitis, but it typically presents as an acute, intermittent inflammation. - The risk of chronic, severe uveitis leading to complex cataract surgery and significant postoperative complications is not as consistently high or as severe as in JRA. *Reiter's syndrome* - Reiter's syndrome (now part of **reactive arthritis**) is another seronegative spondyloarthropathy that can cause acute anterior uveitis. - Similar to psoriatic arthritis, the uveitis is usually acute and self-limiting, and while ocular inflammation needs to be controlled, the risk profile for IOL implantation is not as challenging as in JRA.
Question 3: On measuring 3.5 to 4 mm posterior to the limbus in a phakic eye and plunging a 30 gauge needle perpendicular to sclera, you pass through
- A. Tenon's capsule
- B. Ora serrata
- C. Zonules
- D. Pars plana (Correct Answer)
Explanation: ***Pars plana*** - A 3.5 to 4 mm distance posterior to the limbus in a phakic eye precisely targets the **pars plana**, the safest region for intraocular injections and surgeries to avoid lens damage. - Plunging a needle perpendicular to the sclera at this specific distance allows direct access to the vitreous cavity through the **pars plana**, bypassing critical structures. *Tenon's capsule* - **Tenon's capsule** is a fibrous sheath that envelops the eyeball, and it would be the first layer pierced, but not the final structure accessed for an intraocular procedure at this depth. - While the needle would pass through Tenon's capsule, it is an **extraocular structure** and not the target for safe intraocular access when aiming 3.5-4 mm posterior to the limbus. *Ora serrata* - The **ora serrata** is the jagged anterior termination of the retina and is located approximately 6-8 mm posterior to the limbus in the superior aspect and 5-6 mm inferiorly. - A needle plunged 3.5-4 mm from the limbus would **not reach** the ora serrata and would be positioned anterior to it. *Zonules* - The **zonules of Zinn** are suspensory ligaments that hold the lens in place, originating from the ciliary body and attaching to the lens capsule. - These structures are located more anteriorly within the anterior chamber and behind the iris, and plunging a needle 3.5-4 mm posterior to the limbus would **bypass the zonules entirely**.
Question 4: Constantly changing refractive error is seen in:
- A. Morgagnian cataract
- B. Intumescent cataract
- C. Traumatic cataract
- D. Diabetic cataract (Correct Answer)
Explanation: ***Diabetic cataract*** - Fluctuating blood glucose levels in diabetes can cause changes in the **osmolarity of the aqueous humor**, which in turn affects the hydration of the lens and its refractive power. - This leads to a **constantly changing refractive error**, where a person's prescription might change rapidly over short periods of time. *Morgagnian cataract* - This is a type of **hypermature cataract** where the cortex has liquefied, allowing the nucleus to sink within the capsular bag. - While vision is severely impaired, it doesn't typically present with a constantly changing refractive error, but rather a stable, significant vision loss. *Intumescent cataract* - An **intumescent cataract** is a mature or hypermature cataract where the lens has become significantly swollen due to water absorption. - This swelling causes the anterior capsule to stretch, but it results in a fixed and profound vision loss, not a fluctuating refractive error. *Traumatic cataract* - A **traumatic cataract** develops as a result of blunt or penetrating ocular injury, causing damage to the lens fibers. - While the specific type of refractive error can vary depending on the trauma, it typically presents as a stable visual impairment rather than a constantly changing refractive error.
Question 5: Which keratometry reading is most accurate in post-LASIK eyes for IOL power calculation?
- A. Topography-derived K
- B. Total corneal power (Correct Answer)
- C. Manual keratometry
- D. Automated keratometry
Explanation: ***Total corneal power*** * After LASIK, the **anterior and posterior corneal curvatures** are altered, leading to discrepancies in standard keratometry readings. * **Total corneal power** methods, such as those derived from **corneal tomography** or **anterior segment OCT**, account for both surfaces, providing a more accurate estimation of the true refractive power. * *Topography-derived K* * While corneal topography is valuable for assessing the anterior corneal surface and identifying **irregular astigmatism**, it traditionally focuses on the anterior curvature and may not fully account for the altered **posterior corneal surface** after LASIK. * Standard topography-derived K values often rely on assumptions about the posterior-to-anterior corneal curvature ratio, which are invalid after refractive surgery. * *Manual keratometry* * Manual keratometry measures the **anterior corneal curvature** at a few discrete points and is highly susceptible to inaccuracies due to the post-LASIK changes in corneal shape. * It tends to **overestimate the corneal power** in eyes that have undergone myopic LASIK and **underestimate it** in hyperopic LASIK, leading to significant IOL power calculation errors. * *Automated keratometry* * Similar to manual keratometry, automated keratometry primarily measures the **anterior corneal surface** and relies on a fixed refractive index ratio that is no longer valid after corneal reshaping. * These devices generally provide **inaccurate keratometry readings** in post-refractive surgery eyes, contributing to refractive surprises after cataract surgery.
Question 6: In which of the following conditions is the intraocular pressure very high, and inflammation is minimal?
- A. Glaucomatocyclic crises (Correct Answer)
- B. Angle closure glaucoma
- C. Acute iridocyclitis
- D. Hypertensive uveitis
Explanation: ***Glaucomatocyclic crises*** - This condition is characterized by recurrent, self-limiting episodes of markedly **elevated intraocular pressure (IOP)** with minimal or no overt signs of inflammation in the anterior chamber. - The elevated IOP is thought to result from **altered humor outflow** due to subtle inflammation of the trabecular meshwork. *Acute iridocyclitis* - Presents with significant signs of **intraocular inflammation**, including **cells and flare** in the anterior chamber, typically with pain and photophobia. - While IOP can be elevated, it's a direct result of inflammation reducing outflow, and the inflammation itself is prominent. *Angle closure glaucoma* - This condition involves a sudden and severe rise in **IOP** due to blockage of the aqueous humor outflow pathway by the peripheral iris, but it's not primarily an inflammatory process. - While the eye can appear red and painful, this is due to ischemia and corneal edema, not marked **intraocular inflammation** like that seen in uveitis. *Hypertensive uveitis* - Refers to any **uveitis** that causes a rise in **intraocular pressure**, meaning significant inflammation is present. - The high IOP is secondary to the inflammation, which can obstruct the trabecular meshwork or stimulate prostaglandin release, both causing reduced outflow.
Question 7: Phacoemulsification incision is at what location?
- A. Sclera
- B. Sclero-corneal junction
- C. Cornea (Correct Answer)
- D. None of the options
Explanation: ***Correct: Cornea*** - The standard incision for **modern phacoemulsification** is a small (2.2-2.8mm), self-sealing **clear corneal incision**. - This incision is typically placed **1-2mm anterior to the limbus** in the temporal quadrant. - **Advantages:** Quicker healing, minimal induced astigmatism, reduced bleeding, sutureless technique, and excellent visualization. - Clear corneal incisions have become the **gold standard** for phacoemulsification since the 1990s. *Incorrect: Sclero-corneal junction* - While historically used for **limbal incisions** in traditional extracapsular cataract extraction (ECCE), this location is less common for modern phacoemulsification. - **Disadvantages:** Increased risk of bleeding from limbal vessels, potentially higher induced astigmatism, and longer healing time. - Some surgeons still use limbal or near-limbal approaches, but clear corneal incisions are preferred. *Incorrect: Sclera* - A primary incision through the **sclera alone** is not standard for phacoemulsification. - Scleral incisions may be used as **secondary port incisions** for instrument access or in specific surgical situations (e.g., combined procedures). - **Disadvantages:** Increased bleeding risk, poor visualization (non-transparent tissue), and typically requires suturing. *Incorrect: None of the options* - This is incorrect as **cornea** is definitively the correct location for standard phacoemulsification incisions in modern cataract surgery.
Question 8: Which condition is associated with pseudoproptosis?
- A. Elongation of the eyeball (High myopia) (Correct Answer)
- B. Hyperthyroidism (Thyrotoxicosis)
- C. True exophthalmos (Orbital proptosis)
- D. Orbital mass (Deep orbital tumour)
Explanation: ***Elongation of the eyeball (High myopia)*** - **Pseudoproptosis** refers to the appearance of prominent eyes without actual forward displacement of the globe, often seen in conditions like **high myopia** due to the elongated eyeball. - In high myopia, the **axial length of the eye** is significantly increased, which can make the eye appear to protrude more anteriorly. *Hyperthyroidism (Thyrotoxicosis)* - While hyperthyroidism can cause **exophthalmos** (true proptosis), it is due to orbital inflammation and fat expansion, not pseudoproptosis. - **Thyroid eye disease** involves immune-mediated changes in the orbital tissues, leading to actual forward displacement of the eye. *True exophthalmos (Orbital proptosis)* - **True exophthalmos** denotes actual anterior displacement of the eyeball from the orbit, which is distinct from pseudoproptosis where the eye only appears prominent. - It results from increased orbital content pushing the globe forward, rather than the eye's shape or size. *Orbital mass (Deep orbital tumour)* - An **orbital mass** can cause **true proptosis** by occupying space within the orbit and physically pushing the globe forward. - This is a structural cause of actual globe displacement, unlike the appearance of prominence in pseudoproptosis.
Question 9: The image shows a funnel shaped anterior chamber (deeper in the center and narrow in the periphery), which is seen in angle closure glaucoma. This is caused by:
- A. Anterior synechiae
- B. Posterior synechiae
- C. Iris bombe (Correct Answer)
- D. Pupillary block
Explanation: ***Iris bombe*** - **Iris bombe** occurs when there is a 360-degree adhesion between the iris and the lens (or anterior vitreous in aphakic/pseudophakic eyes), preventing aqueous humor from flowing from the posterior chamber to the anterior chamber. - This build-up of aqueous humor in the posterior chamber pushes the entire iris anteriorly, creating a **funnel-shaped anterior chamber** that is deeper centrally and shallow peripherally, leading to angle closure. *Anterior synechiae* - **Anterior synechiae** are adhesions between the iris and the cornea or trabecular meshwork, directly closing the angle. - While they cause **angle closure**, they are a consequence of the iris being pushed forward rather than the primary cause of the iris bowing shown. *Posterior synechiae* - **Posterior synechiae** are adhesions between the iris and the lens, specifically at the pupillary margin. - When these adhesions are 360 degrees, they precisely lead to **iris bombe** by blocking aqueous flow from the posterior to the anterior chamber. *Pupillary block* - **Pupillary block** is the mechanism by which aqueous flow is obstructed at the pupil. - It describes the functional blockage and is the underlying cause for the anatomical manifestation of **iris bombe**.
Question 10: Which of the following statements about congenital glaucoma is incorrect?
- A. Thin and blue sclera seen
- B. Anterior chamber is shallow (Correct Answer)
- C. Photophobia is most common symptom
- D. Haab's Striae may be seen
Explanation: ***Anterior chamber is shallow*** - In congenital glaucoma, the **anterior chamber depth is typically normal or deep**, not shallow. - A shallow anterior chamber is more characteristic of **angle-closure glaucoma**, which is mechanistically different. - This makes the statement incorrect, as congenital glaucoma is associated with a **deep anterior chamber** due to globe enlargement. *Photophobia is most common symptom* - **Photophobia** (sensitivity to light) is indeed one of the classic presenting symptoms in congenital glaucoma. - It forms part of the classic triad: **photophobia, epiphora (tearing), and blepharospasm**. - This occurs due to **increased intraocular pressure** causing corneal edema and irritation. *Thin and blue sclera seen* - The **sclera** can appear thin and blue due to **buphthalmos** (enlargement of the eye) and stretching of the globe. - The stretching allows the underlying **uveal tissue** to show through, giving the characteristic blue appearance. - This is a direct consequence of elevated intraocular pressure in a developing eye. *Haab's Striae may be seen* - **Haab's striae** are **Descemet's membrane tears** that are pathognomonic of congenital glaucoma. - These horizontal or curvilinear breaks occur due to stretching of the cornea from **elevated intraocular pressure**. - They appear as visible linear opacities on corneal examination.
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