When documenting extended keratometer readings, what should be added or subtracted based based on new readings?

In the context of documenting extended keratometer readings, it is essential to adjust the recorded values based on physiological and measurement parameters when new readings are taken. The practice of adding or subtracting specific diopter values helps in ensuring the accuracy and suitability of the keratometric data for clinical purposes, such as fitting contact lenses or planning surgical interventions.

Adding 9 diopters or subtracting 6 diopters is supported by clinical guidelines that indicate these adjustments are necessary to reflect changes in corneal curvature or refractive status effectively. This variability in keratometry readings can occur due to a variety of factors such as changes in the patient's eye condition or the technique used in measurement, and these adjustments help clinicians maintain consistent and reliable data across different assessment periods.

The other options present adjustments that are either too minor or insufficiently aligned with clinical standards, which can undermine the accuracy needed for patient care. Therefore, understanding and applying the appropriate adjustments in keratometer readings is crucial for accurate documentation and effective patient management.