Prescribing glasses is one of the basic tasks ophthalmologists perform. We begin with a refraction to determine the patient’s refractive error and then hand the patient the final prescription. However, the process is subjective and errors can occur at many steps. Therefore, some patients inevitably return to our offices upset with their new lenses. Here are some basic guidelines for prescribing glasses and dealing with unhappy patients:
Prescribing Glasses:
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Be careful not to over-minus.
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Try not to change the sphere or cylinder by more than 0.50D and the axis by more than 5 degrees, particularly in patients with high refractive errors. If a large change is prescribed, warn the patient that it may take time to adapt.
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Perform a cycloplegic refraction in hyperopes and children to uncover the full refractive error. Children can be given the full cycloplegic refraction; adults should return for a second manifest refraction pushing plus with a trial frame adaptation.
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Beware of changing the patient’s type of bifocal segment.
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Measure near/intermediate vision at the patient’s preferred reading/computer distance accurately when determining the add power.
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Measure vertex distance for high refractive errors.
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Do not change the base curve.
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Be careful with anisometropia. Most people cannot tolerate the aniseikonia induced by more than 3D of anisometropia. If 3D or more of anisometropia is found, consider single vision reading glasses or slab-off lenses for bifocals.
Managing Unhappy Patients:
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Measure the patient’s new lenses to determine if the prescription was made correctly.
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Check the alignment of the patient’s pupils with the optical centers of the lenses.
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Check the bifocal segment height and alignment.
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Check the patient’s preferred reading/computer distance.
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Check the base curve of the lenses (a change results in distortion and feeling of motion sickness when looking off-center).
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Re-refract the patient, and consider a cycloplegic refraction.