Over-refracting Techniques for the Presbyopic Patient
BY MARY JO STIEGEMEIER, OD, FAAO
Streamlining over-refraction can decrease chair time when fitting presbyopes. I modify techniques for presbyopic contact lens patients and adapt them even further for a monovision approach, a standard binocular bifocal approach, or a modified bifocal approach. approach, a standard binocular bifocal approach or a modified bifocal approach.
When the option is monovision, first do a good manifest refraction with balance. Note the most plus, least minus correction for the distance and least amount of add for acceptable near. Select the dominant eye as the distance eye and insert the most plus, least minus correction. On the nondominant, or near eye, select the least plus that will achieve adequate near acuity to begin.
Over-refract binocularly and record binocular vision using this modified technique. Show the patient the Snellen chart with both eyes open. Over the distance eye, show +0.50D and then –0.75D. If your distance sphere is correct, both of those will be rejected; if accepted, demonstrate the change by only 0.25D. Then over that lens, again show +0.50D and then –0.75D. Again, when both are rejected you'll be at your final sphere.
With the best distance sphere in place, present the reading chart at the appropriate distance for that patient. Begin the over-refraction at near by showing –0.75D over the reading eye. If the vision is good and –0.75D makes it worse, stop. If vision isn't adequate and –0 .75D doesn't improve it, add plus in 0.25D steps until you achieve adequate vision. Changes for distance and near should be small and infrequent with an excellent manifest refraction.
When over-refracting with the standard bifocal approach, it's helpful to consider whether the patient is wearing a distance-center or near-center design.
For distance-center designs, on both eyes apply the most plus, least minus correction for distance with the least amount of add acceptable for near. Again, take binocular acuities and use your retinoscope to see if you scope plus or minus. If you scope any plus, show that to the patient in +0.25D intervals binocularly to see if he'll accept it. You should need to adjust the distance power by only 0.25D either way with a correct manifest refraction.
Once you establish the distance power, take binocular near acuities. If the acuity is acceptable for near, stop there. If it's not acceptable, show small amounts of plus on the non-dominant eye initially and adjust either the add power or distance power accordingly. Again, make changes in as small an increment as possible and in only one eye to help maintain maximum acuity and binocularity. Recheck distance acuity if changes are made for near. You may need to repeat the process.
If the design is near center, again apply on both eyes the most plus, least minus correction for distance with the minimal add. Use the retinoscope and the ophthalmoscope to view the add in the pupil and to evaluate the retinoscopy reflex in the periphery of the pupil. Next, over-refract the patient, keeping in mind that the patient may take a lot more minus than necessary for distance. The patient will "eat minus" to negate his add if he is looking through the wrong zone of the lens.
Modified Bifocal Approach
When prescribing a modified bifocal approach, make changes based on binocular vision and the over-refraction technique described in the monovision approach. Over-refract the dominant eye for distance and the non-dominant eye for near in 0.25D steps.
Dr. Stiegemeier is in private practice in Beachwood, Ohio. She lectures throughout the country on the subject of contact lenses and performs clinical research.