Ophthalmic Surgery — MCQs

Ophthalmic Surgery Indian Medical PG Practice Questions and MCQs

Question 21: Epilation is not indicated in which of the following conditions?

A. Ulcerative blepharitis
B. Phthiriasis
C. Trichiasis
D. Madarosis (Correct Answer)

Explanation: **Explanation:** The core concept tested here is the definition of clinical terms related to eyelashes. **Epilation** is the process of manual removal of eyelashes using forceps. It is a therapeutic procedure used when eyelashes are misdirected, infected, or infested. **Why Madarosis is the correct answer:** **Madarosis** refers to the **partial or complete loss of eyelashes** (or eyebrows). Since the eyelashes are already missing in this condition, epilation is logically impossible and clinically contraindicated. Madarosis is commonly associated with leprosy, hypothyroidism, and chronic blepharitis. **Analysis of incorrect options:** * **Trichiasis:** This is the inward misdirection of eyelashes from their normal site of origin. Epilation is the primary temporary treatment to prevent these lashes from rubbing against the cornea and causing abrasions or ulcers. * **Ulcerative Blepharitis:** This is a staphylococcal infection of the lash follicles. Epilation of the lashes involved in the small pustules helps in drainage and faster resolution of the infection. * **Phthiriasis (Phthiriasis Palpebrarum):** This is an infestation of the lashes by the pubic louse (*Pthirus pubis*). Mechanical epilation of the lashes containing nits (eggs) and adult lice is a recognized part of the management. **High-Yield Clinical Pearls for NEET-PG:** * **Distinction:** Do not confuse **Trichiasis** (misdirected lashes) with **Distichiasis** (extra row of lashes from Meibomian gland openings). * **Treatment of choice:** While epilation is a temporary measure for Trichiasis (recurrence in 4–6 weeks), **electrolysis** or **cryotherapy** are used for permanent destruction of the follicles. * **Madarosis Differential:** If a question mentions "loss of lateral 1/3rd of eyebrows," think **Hypothyroidism** or **Leprosy** (Hertoghe's sign).

Question 22: In human corneal transplantation, what is the typical source of donor tissue?

A. Synthetic polymer
B. Donated human cadaver eyes (Correct Answer)
C. Donated eyes from live human beings
D. Monkey eyes

Explanation: **Explanation:** **Corneal transplantation (Keratoplasty)** is the replacement of a damaged or diseased cornea with healthy donor corneal tissue. 1. **Why Option B is correct:** The standard source for corneal grafts is **donated human cadaver eyes**. The cornea is an avascular tissue, which makes it uniquely "immunologically privileged." This allows for successful transplantation from deceased donors without the need for strict HLA matching in routine cases. Donor tissue is typically harvested within 6–12 hours of death and can be stored in media like **McCarey-Kaufman (MK)** or **Optisol-GS**. 2. **Why other options are incorrect:** * **Option A:** Synthetic polymers are used in **Keratoprosthesis** (e.g., Boston Kpro), but these are reserved for cases where human donor grafts have repeatedly failed or are contraindicated (e.g., severe chemical burns). * **Option C:** Living donation is not practiced because harvesting a cornea would result in permanent blindness and surgical trauma for the donor, which is ethically prohibited. * **Option D:** Xenotransplantation (using animal tissue like monkey eyes) is not used in humans due to the high risk of hyperacute rejection and potential transmission of zoonotic infections. **High-Yield Clinical Pearls for NEET-PG:** * **Storage:** MK medium (4°C) preserves the cornea for 4 days; Optisol-GS preserves it for up to 14 days. * **Contraindications for Donor:** Death from unknown cause, rabies, HIV, Hepatitis B/C, Creutzfeldt-Jakob disease, and leukemia/lymphoma. * **Age Limit:** Ideally, donors should be between 2 and 70 years old to ensure adequate **endothelial cell count** (the most critical factor for graft survival). * **Pre-requisite:** The most important layer to preserve during storage is the **endothelium**, as these cells do not regenerate.

Question 23: Vitrectomy approach is most commonly via which anatomical location?

A. Pars plana (Correct Answer)
B. Cornea
C. Equator of the eye
D. None of the above

Explanation: **Explanation:** **Pars Plana Vitrectomy (PPV)** is the gold standard approach for posterior segment surgeries. The **pars plana** is a part of the ciliary body located approximately 3.5 mm to 4 mm posterior to the limbus. It is considered the "surgical gateway" to the vitreous cavity because it is **relatively avascular** and, most importantly, it is located behind the lens and anterior to the functional retina (ora serrata). Entering through this zone minimizes the risk of causing a retinal detachment or damaging the crystalline lens. **Analysis of Options:** * **Cornea (Option B):** The corneal approach is used for anterior segment surgeries (e.g., cataract surgery or keratoplasty). While an "anterior vitrectomy" can be performed via a limbal incision during complicated cataract surgery, it is not the standard approach for a formal vitrectomy. * **Equator of the eye (Option C):** The equator is located much further posterior (approximately 12-14 mm from the limbus). Attempting to enter here would result in immediate **retinal perforation and hemorrhage**, as the functional sensory retina is firmly attached at this location. **High-Yield Clinical Pearls for NEET-PG:** * **Anatomical Landmarks:** In phakic eyes (natural lens present), the incision is made **4 mm** from the limbus. In aphakic/pseudophakic eyes, it is made **3.5 mm** from the limbus. * **Indications for PPV:** Retinal detachment, vitreous hemorrhage (most common cause: Diabetic Retinopathy), endophthalmitis, and dropped lens fragments. * **Infusion Port:** During PPV, a constant infusion of fluid is required to maintain intraocular pressure; this port is always placed first.

Question 24: What is the safe size of a corneal graft with the least chances of failure?

A. 7.5 mm (Correct Answer)
B. 6.5 mm
C. 5.5 mm
D. 4.5 mm

Explanation: In Penetrating Keratoplasty (PKP), the size of the donor corneal graft is critical for visual recovery and graft survival. **Why 7.5 mm is the Correct Answer:** The standard "safe" range for a corneal graft is **7.0 mm to 8.5 mm**, with **7.5 mm** being the most common and ideal size. * **Optical Zone:** A graft of this size is large enough to cover the pupillary area, ensuring a clear visual axis and minimizing postoperative astigmatism. * **Immunological Safety:** It remains far enough from the **limbus** (the peripheral vascularized zone). The limbus contains blood vessels and lymphatics; the closer a graft is to the limbus, the higher the risk of graft rejection due to increased exposure to the host’s immune system. **Explanation of Incorrect Options:** * **6.5 mm (Option B):** While sometimes used in specific pediatric cases, a 6.5 mm graft is generally considered too small. It often results in significant **high irregular astigmatism** and may not sufficiently cover the optical zone if the graft decenters slightly. * **5.5 mm and 4.5 mm (Options C & D):** These are far too small for standard keratoplasty. Very small grafts lead to severe optical distortion and "taco-shelling" of the cornea. Furthermore, they provide an insufficient number of healthy donor endothelial cells to maintain long-term corneal clarity. **NEET-PG High-Yield Pearls:** * **The "Oversizing" Rule:** The donor button is typically cut **0.25 mm to 0.50 mm larger** than the host bed (e.g., a 7.5 mm host bed receives a 7.75 mm donor graft) to ensure a watertight closure and reduce postoperative flattening/glaucoma. * **Large Grafts (>8.5 mm):** These are associated with a very high risk of vascularization, rejection, and secondary glaucoma (due to peripheral anterior synechiae). * **Small Grafts (<7.0 mm):** These are associated with high astigmatism and poor optical quality.

Question 25: Which of the following is not of prognostic significance to choroidal melanoma?

A. Presence of retinal detachment (Correct Answer)
B. Size of the tumour
C. Cytology of the tumor cells
D. Presence of extraocular extension

Explanation: **Explanation:** Choroidal melanoma is the most common primary intraocular malignancy in adults. Its prognosis is determined by factors that correlate with the risk of metastasis (primarily to the liver) and local recurrence. **Why Retinal Detachment is the Correct Answer:** Exudative retinal detachment is a very common **clinical presentation** of choroidal melanoma, occurring as the tumor pushes against the retina or leaks fluid. While it is a significant finding for diagnosis and surgical planning, it does **not** correlate with the biological aggressiveness of the tumor or the long-term survival of the patient. Therefore, it lacks prognostic significance. **Analysis of Other Options:** * **Size of the Tumor (B):** This is one of the most important prognostic factors. The COMS (Collaborative Ocular Melanoma Study) classifies tumors by size; larger tumors (especially those with a diameter >15mm or height >10mm) have a significantly higher risk of metastasis. * **Cytology (C):** The Callender classification identifies cell types. **Spindle A** cells have the best prognosis, while **Epithelioid** cells (large, pleomorphic) have the worst prognosis. * **Extraocular Extension (D):** Extension through the sclera into the orbit significantly worsens the prognosis and increases the likelihood of systemic spread. **High-Yield Clinical Pearls for NEET-PG:** * **Most common site of metastasis:** Liver (90% of cases). * **Genetic Marker:** Monosomy 3 is the most significant genetic indicator of poor prognosis. * **Pathological feature of poor prognosis:** Presence of "closed vascular loops" (extracellular matrix patterns). * **Treatment:** Plaque radiotherapy (Brachytherapy) is the standard for medium-sized tumors; Enucleation is reserved for large or complicated tumors.

Question 26: What is the standard incision size for sutureless cataract surgery performed with phacoemulsification and foldable IOL?

A. 1-1.5mm
B. 2-2.5mm
C. 3-3.5mm (Correct Answer)
D. 3.5-4.5mm

Explanation: **Explanation:** In modern cataract surgery, the goal is to achieve a **self-sealing, astigmatically neutral incision**. The standard incision for Phacoemulsification with a foldable Intraocular Lens (IOL) is typically **3.0 to 3.2 mm** (falling within the **3–3.5 mm** range). This size is ideal because it is large enough to accommodate the phacoemulsification probe and the cartridge of a foldable IOL injector, yet small enough to remain "sutureless" due to the architecture of the clear corneal tunnel, which uses intraocular pressure to maintain a watertight seal. **Analysis of Options:** * **A (1–1.5 mm):** This is the size used for **side-port incisions** (paracentesis) to introduce secondary instruments, but it is too small for the main phaco probe or IOL delivery. * **B (2–2.5 mm):** This corresponds to **Micro-Incision Cataract Surgery (MICS)**. While increasingly popular, it requires specialized ultra-thin injectors and sub-2mm phaco tips. It is not yet considered the "standard" general range for conventional foldable IOL surgery. * **C (3–3.5 mm):** **Correct.** This is the standard "clear corneal incision" (CCI) size that balances surgical ease with rapid wound healing and minimal induced astigmatism. * **D (3.5–4.5 mm):** This size is typically required for **non-foldable (rigid) PMMA lenses** or older phaco techniques. Incisions larger than 3.5 mm often lose their self-sealing property and may require sutures. **High-Yield Clinical Pearls for NEET-PG:** * **Self-sealing mechanism:** Depends on the **square-shaped** architecture (length of the tunnel should be equal to or greater than the width). * **SIA (Surgically Induced Astigmatism):** Larger incisions cause more flattening along the meridian of the incision. Moving from 5.5 mm (SICS) to 3.0 mm (Phaco) significantly reduces SIA. * **SICS (Small Incision Cataract Surgery):** Uses a **5.5–7 mm** sclerocorneal tunnel; it is sutureless but much larger than phacoemulsification incisions.

Question 27: What is the advantage of an intraocular lens over glasses?

A. Better field of vision
B. Better accommodation
C. Better underwater vision for swimmers
D. All of the above (Correct Answer)

Explanation: The correct answer is **D. All of the above**. ### **Explanation** The primary advantage of an **Intraocular Lens (IOL)** over aphakic spectacles (glasses) lies in its ability to restore the eye’s optics to a near-physiological state. 1. **Better Field of Vision:** Aphakic glasses (usually +10D or more) cause significant peripheral distortion and a "ring scotoma" (Jack-in-the-box phenomenon) due to the prismatic effect of thick lenses. An IOL is placed at or near the nodal point of the eye, eliminating these distortions and providing a full, natural peripheral field. 2. **Better Accommodation:** While standard monofocal IOLs do not accommodate, modern **pseudo-accommodative or multifocal IOLs** provide better functional range than glasses. Furthermore, even a monofocal IOL allows for a degree of "pseudo-accommodation" through pupillary miosis and the Stiles-Crawford effect, which is superior to the fixed focal distance of heavy spectacles. 3. **Better Underwater Vision:** For swimmers, glasses are impractical and lose their refractive power underwater. An IOL remains stable and functional within the eye, allowing the patient to use standard swimming goggles without the magnification issues associated with high-plus spectacles. ### **Clinical Pearls for NEET-PG** * **Image Magnification:** Aphakic glasses magnify images by **25–33%**, leading to false orientation. IOLs produce only **0–2%** magnification, making them the gold standard for unilateral aphakia to avoid **aniseikonia** (unequal image sizes). * **Anisometropia:** IOLs are the treatment of choice to prevent binocular diplopia in patients with a large refractive difference between eyes. * **Positioning:** The **"Bag-in-the-lens"** or posterior chamber IOL (PCIOL) is the most physiological placement.

Question 28: What is the wavelength of the Nd:YAG laser?

A. 1064 nm (Correct Answer)
B. 532 nm
C. 1040 nm
D. 1064 pm

Explanation: **Explanation:** The **Nd:YAG (Neodymium-doped Yttrium Aluminum Garnet)** laser is a solid-state laser widely used in ophthalmology [1]. It operates in the **infrared spectrum** with a characteristic wavelength of **1064 nm** [1]. **1. Why 1064 nm is correct:** The Nd:YAG laser works on the principle of **photodisruption**. It creates a high-energy plasma shield that causes a "micro-explosion," mechanically cutting ocular tissues regardless of pigmentation. This makes it ideal for procedures like **Posterior Capsulotomy** (for Posterior Capsular Opacification) and **Peripheral Iridotomy** (for Angle-Closure Glaucoma). **2. Analysis of Incorrect Options:** * **532 nm (Option B):** This is the wavelength of the **Frequency-doubled Nd:YAG** (also known as the Green Laser). It is used for **photocoagulation** in retinal diseases like Diabetic Retinopathy. * **1040 nm (Option C):** This is close to the wavelength used in some **Femtosecond lasers** (typically around 1030–1050 nm), which are used for LASIK flaps and laser-assisted cataract surgery. * **1064 pm (Option D):** This is a distractor involving units. "pm" stands for picometers; the laser operates in the nanometer (nm) range. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Photodisruption (Non-thermal). * **Common Uses:** Posterior Capsulotomy, Peripheral Iridotomy, and YAG Vitreolysis. * **Key Contraindication:** Do not perform YAG capsulotomy if there is active intraocular inflammation or corneal edema. * **Complication:** A common side effect of YAG capsulotomy is a transient rise in Intraocular Pressure (IOP) and potential IOL pitting.

Question 29: Modern intraocular lenses (IOLs) are primarily made up of which of the following materials?

A. Acrylic
B. PMMA (Polymethyl methacrylate) (Correct Answer)
C. PML
D. Silicone

Explanation: **Explanation:** The correct answer is **PMMA (Polymethyl methacrylate)**. **Why PMMA is the correct answer:** PMMA is a rigid, hydrophobic, and highly biocompatible polymer that has been the "gold standard" material for intraocular lenses since Sir Harold Ridley implanted the first IOL in 1949. It is non-biodegradable, optically clear, and exceptionally stable within the aqueous humor. While modern surgery often utilizes foldable lenses, PMMA remains the primary material for non-foldable (rigid) IOLs used in conventional Extracapsular Cataract Extraction (ECCE). **Analysis of Incorrect Options:** * **Acrylic (Option A):** While foldable acrylic (hydrophilic or hydrophobic) is the most common material used in modern **Phacoemulsification**, PMMA is historically and fundamentally the primary material defined in standard ophthalmic textbooks for IOL composition. * **PML (Option C):** This is a distractor and not a standard material used in the manufacturing of intraocular lenses. * **Silicone (Option D):** Silicone was the first foldable IOL material. However, it is used less frequently today due to its association with higher rates of posterior capsular opacification (PCO) and interference with vitreoretinal surgeries (silicone oil adherence). **High-Yield Clinical Pearls for NEET-PG:** * **Historical Fact:** Sir Harold Ridley used PMMA based on observations of Spitfire pilots who had shards of Perspex (PMMA) in their eyes without significant inflammation. * **Foldable vs. Rigid:** PMMA lenses require a larger incision (5-6mm), whereas Acrylic/Silicone lenses are foldable and can be inserted through micro-incisions (2.2–2.8mm). * **Square Edge Design:** Modern IOLs (especially Acrylic) use a "square edge" to prevent the migration of lens epithelial cells, thereby reducing the incidence of **Posterior Capsular Opacification (PCO)**. * **UV Protection:** Modern PMMA lenses are treated with UV-absorbing compounds to protect the retina.

Question 30: What are the potential complications of a peribulbar block?

A. Retrobulbar hemorrhage
B. Globe rupture
C. Optic neuritis
D. All of the above (Correct Answer)

Explanation: **Explanation:** A **peribulbar block** is a regional anesthesia technique where anesthetic is injected into the extraconal space (outside the muscle cone). While it is generally considered safer than a retrobulbar block (intraconal), it still carries significant risks due to the proximity of the needle to vital ocular structures. **Why "All of the Above" is correct:** 1. **Retrobulbar Hemorrhage (Option A):** This is the most common serious complication. It occurs when the needle punctures a vessel (usually the ophthalmic artery or its branches), leading to a rapid increase in intraorbital pressure, proptosis, and potential vision loss. 2. **Globe Rupture (Option B):** Accidental globe perforation is a devastating complication. It is more common in patients with high axial myopia (staphyloma) where the eyeball is longer and the sclera is thinner. 3. **Optic Nerve Injury/Neuritis (Option C):** Direct trauma to the optic nerve by the needle or toxicity from the anesthetic agent can lead to optic nerve dysfunction, often presenting as traumatic optic neuropathy or an inflammatory response (neuritis). **Other potential complications include:** * **Brainstem Anesthesia:** Occurs if the anesthetic enters the optic nerve sheath and tracks back to the CNS, leading to respiratory depression. * **Oculocardiac Reflex:** Bradycardia triggered by increased intraorbital pressure. **High-Yield Clinical Pearls for NEET-PG:** * **Peribulbar vs. Retrobulbar:** Peribulbar blocks require a larger volume of anesthetic (6–10 mL) compared to retrobulbar blocks (3–5 mL) but have a lower risk of intradural injection. * **Contraindication:** Avoid these blocks in patients with a "bleeding diathesis" or those on anticoagulants. * **Safety Tip:** Always ask the patient to look in the **primary position** (straight ahead) during the block to minimize the risk of optic nerve injury; the "up and in" position (Atkinson’s position) is now discouraged as it puts the optic nerve in the path of the needle.

Practice by Chapter

Surgical Anatomy of Eye

Practice Questions

Asepsis and Sterilization in Eye Surgery

Practice Questions

Anesthesia in Ophthalmic Surgery

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Cataract Surgery Techniques

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Corneal Surgeries

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Glaucoma Surgeries

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Oculoplastic Surgeries

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Vitreoretinal Surgeries

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Strabismus Surgery

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Refractive Surgery

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Ocular Oncology Surgeries

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Management of Surgical Complications

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