Free Board Certified Ophthalmologist Cornea and External Disease Questions and Answers — Questions and Answers
Question 1: A 28-year-old daily soft contact lens wearer presents with severe eye pain that is disproportionate to the clinical signs. Slit-lamp examination reveals a faint ring infiltrate and radial keratoneuritis. The corneal epithelium is largely intact. What is the most likely causative organism?
- Pseudomonas aeruginosa
- Fusarium solani
- Acanthamoeba species (Correct answer)
- Herpes Simplex Virus
Correct answer: Acanthamoeba species
The classic triad of severe pain out of proportion to clinical signs, a ring infiltrate, and radial keratoneuritis (inflammation along corneal nerves) in a contact lens wearer is highly pathognomonic for Acanthamoeba keratitis. [15, 17, 31, 33] While Pseudomonas can cause severe keratitis in contact lens wearers, radial keratoneuritis is less common. Fungal keratitis typically has feathery infiltrates, and herpetic keratitis often presents with dendritic ulcers and decreased corneal sensation.
Question 2: Which of the following corneal dystrophies is NOT associated with a mutation in the Transforming Growth Factor Beta Induced (TGFB1) gene?
- Reis-Bücklers Corneal Dystrophy
- Macular Corneal Dystrophy (Correct answer)
- Granular Corneal Dystrophy, Type I
- Lattice Corneal Dystrophy, Type I
Correct answer: Macular Corneal Dystrophy
Macular Corneal Dystrophy is an autosomal recessive disorder caused by mutations in the Carbohydrate Sulfotransferase 6 (CHST6) gene, which leads to abnormal synthesis of keratan sulfate. [6, 7, 9, 13] In contrast, Granular, Lattice, Reis-Bücklers, and Avellino dystrophies are all autosomal dominant conditions associated with various mutations in the TGFB1 gene on chromosome 5q31. [25, 27, 35]
Question 3: A 55-year-old woman with a history of hyperthyroidism presents with chronic irritation, redness, and a foreign body sensation in both eyes. Examination reveals papillary hypertrophy of the superior tarsal conjunctiva, inflammation and redundancy of the superior bulbar conjunctiva, and fine punctate staining of the superior cornea. What is the most likely diagnosis?
- Vernal keratoconjunctivitis
- Superior Limbic Keratoconjunctivitis (SLK) (Correct answer)
- Trachoma
- Ocular Cicatricial Pemphigoid
Correct answer: Superior Limbic Keratoconjunctivitis (SLK)
Superior Limbic Keratoconjunctivitis (SLK) is characterized by inflammation specifically affecting the superior bulbar and tarsal conjunctiva. The constellation of findings described is classic for SLK, which has a strong association with thyroid eye disease, particularly hyperthyroidism. [3, 19, 26, 29, 30] The other conditions have different characteristic signs and locations of involvement.
Question 4: A construction worker presents to the emergency department immediately after a large splash of wet cement (an alkali substance) to his right eye. Which of the following is the most critical and immediate step in management?
- Measure the intraocular pressure
- Commence copious irrigation of the ocular surface (Correct answer)
- Perform a detailed slit-lamp examination to grade the injury
- Instill a cycloplegic agent to reduce pain
Correct answer: Commence copious irrigation of the ocular surface
For any ocular chemical injury, especially an alkali burn which causes liquefactive necrosis and penetrates tissue rapidly, the single most important and immediate action is copious irrigation. [4, 8, 14, 20, 22] This must be done prior to other examinations to dilute and wash away the offending chemical, thereby minimizing the extent of the damage. All other assessments and treatments are secondary to immediate and prolonged irrigation.
Question 5: When comparing Descemet's Membrane Endothelial Keratoplasty (DMEK) to Descemet's Stripping Automated Endothelial Keratoplasty (DSAEK) for the treatment of Fuchs' Endothelial Dystrophy, DMEK is generally associated with which of the following outcomes?
- A technically less challenging surgical procedure
- Slower visual recovery
- Higher rates of primary graft failure
- Lower rates of allograft rejection (Correct answer)
Correct answer: Lower rates of allograft rejection
DMEK involves transplanting only Descemet's membrane and endothelium, a thinner graft with less donor tissue than DSAEK (which includes posterior stroma). This is associated with faster visual recovery, better final visual acuity, and a significantly lower rate of immunologic graft rejection. [21, 24, 28, 32] However, DMEK is considered more technically challenging than DSAEK, with a higher rate of complications like graft detachment requiring rebubbling.
Question 6: A 64-year-old female presents with gradually decreasing vision and foreign body sensation in her right eye. Examination reveals elevated, gray-white, fibrous-appearing nodules in the mid-peripheral cornea, just anterior to Bowman's layer. After a trial of conservative management with lubrication fails, what is the most appropriate next step in management?
- Penetrating keratoplasty (PKP)
- Systemic immunosuppression
- Superficial keratectomy (Correct answer)
- Amniotic membrane transplantation
Correct answer: Superficial keratectomy
The clinical description is classic for Salzmann's Nodular Degeneration. When these nodules become symptomatic or visually significant, the standard and most effective treatment is superficial keratectomy. [1, 2, 5, 12] This procedure involves surgically removing the nodules from the corneal surface, which directly addresses the pathology. A PKP is excessively invasive for this condition, and systemic immunosuppression or amniotic membrane alone would not remove the nodules.
Free Board Certified Ophthalmologist Cornea and External Disease Questions and Answers
A 28-year-old daily soft contact lens wearer presents with severe eye pain that is disproportionate to the clinical signs.
Slit-lamp examination reveals a faint ring infiltrate and radial keratoneuritis.
The corneal epithelium is largely intact.
What is the most likely causative organism?