33 Questions
What should be done if only one minus sign is visible in the keratometric mires?
The occluder is in the way.
How can the power range of a keratometer be extended?
By using loose lenses over the opening of the keratometer barrel.
In keratometry, what should be done if patient gaze is unsteady?
Ensure that fellow eye is occluded.
What could be a reason for H&V mires not being measureable concurrently in keratometry?
Irregular astigmatism in the patient.
When should a +1.25D loose lens be used in keratometry?
To increase the diopter range.
What action should be taken if mire focus is transient when performing keratometry?
Ensure patient’s forehead is secure against the headrest.
What is the primary purpose of a keratometer?
To assess the curvature of the cornea
In keratometry, what is the significance of mire distortion?
Suggests irregular form of mires which can help with keratoconus diagnosis
How does corneal astigmatism differ from refractive astigmatism?
Corneal and refractive astigmatism may not coincide due to differences in measurement methods
What is a possible reason for corneal and refractive astigmatism not coinciding?
~25% increase in astigmatism when moving from corneal plane to spectacle plane
Which component of a keratometer determines the axis and power of astigmatism?
Axis scale of the 2 meridians
How does the design of a keratometer aid in determining corneal surface curvature?
By reflecting images in the cornea and measuring their size
What should be done if irregular astigmatism is present during keratometry?
First do the horizontal meridian, then the vertical meridian
Which type of astigmatism has more power in the vertical meridian?
With-the-rule (WTR) Astigmatism
In which case should patients with dry eyes be asked to blink or use artificial tears before keratometry?
Before starting the procedure
What should you do if you observe distorted mires during keratometry?
Adjust and re-center as necessary
How are the principal meridians positioned in Oblique Astigmatism?
Between 30-60 degrees and 120-150 degrees
What should be done if the two principal meridians are not 90 degrees apart during keratometry?
First do the horizontal meridian, then readjust and do the vertical meridian
What should be done if CC axis is ATR according to Javal's Rule when applying it practically?
Subtract
In the practice example 43.00@180/46.00@090, what would be the total refractive astigmatism using Javal's Rule?
-3.00@090
When CC axis is WTR as per Javal's Rule in practical application, what should be done to the total refractive astigmatism?
Add
If the Simplified Form of Javal’s Rule gives a result of -1.50x180 for a specific case, what was the initial Keratometric astigmatism?
-1.00x180
In a practical scenario where the CC is -2.00@090, according to Javal's Rule, what would be the total refractive astigmatism?
-2.50@090
What is the purpose of applying a +1.25D lens in front of the barrel in keratometry when the K reading is over 52.00D?
To correct the K drum reading to the true value
In recording keratometric measurements, what does 'MCAR' stand for?
Mires can be recorded as: Clear And Regular
When initial K readings are less than 36.00D, what type of lens should be added in front of the barrel in keratometry?
-1.00D lens
What is the average range of K readings expected in keratometry practice according to the provided text?
Between 43.00 to 44.00
What does Javal's Rule help determine in the context of keratometry?
Relationship between corneal astigmatism and refractive astigmatism
What should be done if irregular astigmatism is detected during keratometry?
Proceed with the horizontal meridian first, then readjust the barrel and proceed with the vertical meridian
What is the recommended approach for observing corneal integrity in patients with dry eyes during keratometry?
Ask the patient to blink or use artificial tears before the procedure
If a patient has ATR astigmatism, what can be expected about the curvature of their principal meridians?
Horizontal meridian is flatter than the vertical meridian
What should be recorded in addition to the amount of corneal astigmatism during keratometry?
Flatter K's/ Steeper K's
What distinguishes between regular astigmatism and irregular astigmatism in keratometry?
Regular astigmatism has principal meridians perpendicular, irregular does not
Learn how to troubleshoot issues related to keratometric mires in a medical instrument. From alignment problems to focusing issues, this guide covers common solutions to ensure accurate measurements during eye exams.
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