CPO FREE CPO Keratometry and Corneal Topography Questions and Answers 2

Question 1

A patient with a history of myopic LASIK now requires cataract surgery. Standard keratometry is performed. Which of the following issues is MOST likely to cause an error in the IOL calculation?

Accepted Answer

Traditional keratometry assumes a normal prolate shape and measures a flattened central zone, leading to an underestimation of corneal power.

Answer

The keratometer will overestimate corneal power, leading to a myopic surprise.

Answer

The posterior corneal curvature, which is unchanged by LASIK, will be the primary source of error.

Answer

The standard refractive index used by the keratometer is invalid for post-ablation corneas, causing a hyperopic surprise.

Question 2

A corneal topography map displays a classic 'crab claw' or 'butterfly' pattern of inferior steepening. This pattern is most characteristic of which ectatic condition?

Accepted Answer

Pellucid Marginal Degeneration (PMD)

Answer

Keratoconus

Answer

Corneal scarring

Answer

Post-keratoplasty astigmatism

Question 3

When reviewing a corneal topography map for a potential orthokeratology (Ortho-K) patient, you notice a 'smiley face' pattern on the differential map after the initial fitting. What does this indicate?

Accepted Answer

The lens is decentered superiorly ('high rider').

Answer

A perfectly centered treatment zone.

Answer

The lens is riding too low ('frowny face').

Answer

The treatment effect is too strong.

Question 4

A patient presents with what appears to be irregular astigmatism on corneal topography. Before assuming a corneal dystrophy, what common and treatable condition should be ruled out first?

Accepted Answer

Severe ocular surface disease or dry eye

Answer

Lens subluxation

Answer

Early-stage glaucoma

Answer

Retinal detachment

Question 5

During keratometry on a patient with advanced, irregular astigmatism from keratoconus, the mires appear distorted and difficult to align. Which of the following statements is the most accurate description of this situation?

Accepted Answer

The findings are expected; keratometry is unreliable for quantifying highly irregular corneal surfaces.

Answer

The keratometer is malfunctioning and requires recalibration.

Answer

This indicates the patient is not a good candidate for any contact lenses.

Answer

Manual keratometry should be repeated with a larger mire pattern to obtain an accurate reading.

Question 6

A patient who has undergone a penetrating keratoplasty (corneal transplant) has significant astigmatism. How is corneal topography most useful in the post-operative management of this patient?

Accepted Answer

To guide the selective removal of sutures to reduce astigmatism.

Answer

To determine the final spectacle prescription immediately.

Answer

To decide if the corneal transplant needs to be repeated.

Answer

To measure the intraocular pressure without touching the graft.