Keratometry

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What should be done if only one minus sign is visible in the keratometric mires?

Ensure the patient’s forehead is secure against the headrest.

Ensure that fellow eye is occluded.

The occluder is in the way. (correct)

Patient's eyelid is drooping, have them open wide.

How can the power range of a keratometer be extended?

By using loose lenses over the opening of the keratometer barrel. (correct)

By increasing the distance between the patient's forehead and the headrest.

By adjusting the mire clarity setting.

By using a +2.00D loose lens.

In keratometry, what should be done if patient gaze is unsteady?

Remind the patient to blink frequently.

Adjust the chinrest position.

Use a loose lens to stabilize the gaze.

Ensure that fellow eye is occluded. (correct)

What could be a reason for H&V mires not being measureable concurrently in keratometry?

Irregular astigmatism in the patient. Signup and view all the answers

When should a +1.25D loose lens be used in keratometry?

To increase the diopter range. Signup and view all the answers

What action should be taken if mire focus is transient when performing keratometry?

Ensure patient’s forehead is secure against the headrest. Signup and view all the answers

What is the primary purpose of a keratometer?

To assess the curvature of the cornea Signup and view all the answers

In keratometry, what is the significance of mire distortion?

Suggests irregular form of mires which can help with keratoconus diagnosis Signup and view all the answers

How does corneal astigmatism differ from refractive astigmatism?

Corneal and refractive astigmatism may not coincide due to differences in measurement methods Signup and view all the answers

What is a possible reason for corneal and refractive astigmatism not coinciding?

~25% increase in astigmatism when moving from corneal plane to spectacle plane Signup and view all the answers

Which component of a keratometer determines the axis and power of astigmatism?

Axis scale of the 2 meridians Signup and view all the answers

How does the design of a keratometer aid in determining corneal surface curvature?

By reflecting images in the cornea and measuring their size Signup and view all the answers

What should be done if irregular astigmatism is present during keratometry?

First do the horizontal meridian, then the vertical meridian Signup and view all the answers

Which type of astigmatism has more power in the vertical meridian?

With-the-rule (WTR) Astigmatism Signup and view all the answers

In which case should patients with dry eyes be asked to blink or use artificial tears before keratometry?

Before starting the procedure Signup and view all the answers

What should you do if you observe distorted mires during keratometry?

Adjust and re-center as necessary Signup and view all the answers

How are the principal meridians positioned in Oblique Astigmatism?

Between 30-60 degrees and 120-150 degrees Signup and view all the answers

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 Signup and view all the answers

What should be done if CC axis is ATR according to Javal's Rule when applying it practically?

Subtract Signup and view all the answers

In the practice example 43.00@180/46.00@090, what would be the total refractive astigmatism using Javal's Rule?

-3.00@090 Signup and view all the answers

When CC axis is WTR as per Javal's Rule in practical application, what should be done to the total refractive astigmatism?

Add Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

In recording keratometric measurements, what does 'MCAR' stand for?

Mires can be recorded as: Clear And Regular Signup and view all the answers

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 Signup and view all the answers

What is the average range of K readings expected in keratometry practice according to the provided text?

Between 43.00 to 44.00 Signup and view all the answers

What does Javal's Rule help determine in the context of keratometry?

Relationship between corneal astigmatism and refractive astigmatism Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

What should be recorded in addition to the amount of corneal astigmatism during keratometry?

Flatter K's/ Steeper K's Signup and view all the answers

What distinguishes between regular astigmatism and irregular astigmatism in keratometry?

Regular astigmatism has principal meridians perpendicular, irregular does not Signup and view all the answers