Reader and Industry Forum
Reader and Industry Forum
A Look at Modified Monovision
BY NATALIE E. COREY, OD, FAAO
Eyecare practitioners may have noticed that, on average, their patients are getting older. In fact, the first generation of soft contact lens wearers are entering into advanced presbyopia. Manufacturers of soft contact lenses have risen to the demand.
While monovision has been the prevailing choice for contact lens correction of presbyopia, more practitioners every year are choosing to fit even emerging presbyopes into multifocal systems. Advantages of multifocal contact lenses over monovision include better binocularity and stereopsis as well as easier adaptation. Monovision may eliminate problems with ghosting or fluctuating vision that can occur with multifocal contact lenses. Monovision contact lenses also allow for crisp, clear vision at one distance in either eye.
While a vast majority of presbyopic patients can be fit with either, there are a select few who will require the benefits of both. In these cases, we use an approach called modified monovision.
What Is Modified Monovision?
Modified monovision generally uses a single vision lens in one eye and a multifocal lens in the other to accommodate a specific visual need for a patient that isn’t met with another presbyopic contact lens system. The single vision lens can be for either distance or near vision.
Modified monovision is rarely considered as a first choice for the contact lens correction of presbyopes. Often, these patients failed out of multifocal lenses because they found their vision lacking at one focal distance or another. Conversely, patients who have been satisfied in monovision in the past may find that they now struggle at intermediate, but do not want to sacrifice crisp vision at another focal distance. It can also be useful for correcting patients who have astigmatism in one eye and rely on a toric lens to see clearly at one distance or another.
Fitting Modified Monovision
First, evaluate why a patient has failed out of other contact lens options. Did the patient struggle with distance or near vision? Is the patient happy at distance, but lacking intermediate vision? If the patient struggles at distance, but finds his near to be acceptable, consider a single vision lens for distance over the dominant eye. If the opposite is true, consider a single vision lens for near over the nondominant eye.
The next step is to manage proper patient expectations. As with every contact lens patient over 40 years old, the goal of contact lens fitting is to provide a balance of acceptable vision at all distances, even though no one distance may be perfect. During each follow-up visit, it is critical to reaffirm the importance of balance between these three focal distances and to ask patients to prioritize which focal distance matters most to them. Throughout the fitting process, use trial lenses outside of the phoropter to demonstrate how changes made to the Rx will affect the patient at all distances.
Modified monovision is only successful if the visual system is treated as a binocular one. Because the visual system will be using information from both eyes, avoid testing patients monocularly in the office and advise patients to avoid covering one eye to assess vision through the other. The cases below demonstrate how the application of modified monovision solved patient’s complaints in other lens systems.
At her annual exam, a 46-year-old daycare operator complained about distance and near blur in her current multifocal contact lenses. She wore Air Optix Multifocal (Alcon) lenses and liked the comfort, but was unsure of her actual prescription. She read 20/25 OD, 20/20 OS, and 20/32 OU through her habitual prescription. She refracted to –2.00 –1.25 x 100 OD and –2.75 –0.75 x 070 OS with a +1.50D add. She had tried toric lenses in the past, but noted no significant improvement in visual acuity (VA).
The initial lenses selected were Air Optix Multifocal –2.50/Med OD and –3.00/High OS. At her first follow up, she noted that her distance vision was “OK,” but her near could use some improvement. Because an over-refraction of +0.25D sph OS helped her near vision, a –2.75/High lens was dispensed for OS. However, at her second follow up, she described her distance vision as poor, despite the improvement in her near vision. Her acuities measured 20/30 OD, 20/25– OS, and 20/20 near OU.
At this time, I switched the patient to modified monovision with an Air Optix Aqua (Alcon) –2.50D sph lens dispensed OD. At her third follow up, she noted that she was much happier with both her distance and her near vision than she had been in any previous lenses. VA OD improved to 20/20, and 20/20 OU acuity was preserved at near.
A 47-year-old sales manager presented wearing spectacles, but stated that he wanted to return to contact lenses for overnight wear. He refracted to –1.50 –1.25 x 090 OD and –1.50 –0.50 x 175 OS with a +1.75D add. His distance vision was best corrected with a toric contact lens in the past.
The lenses dispensed were Air Optix for Astigmatism (Alcon) –1.50 –1.25 x 090 OD and Air Optix Multifocal –1.50/Med OS. A trial of –1.75/Med OS in the office that day did not provide adequate near vision to read text messages and was not dispensed. At the first follow up, the patient noted that he had no usable subjective near vision. He read 20/20 OU at distance but 20/63 OU at near.
I chose a different lens design because no over-refraction OS yielded acceptable near vision. The patient was switched to Biofinity Toric (CooperVision) –1.50 –1.25 x 080 OD and –1.50/1.50 N OS. At his second follow up, he noted a little blur at both distances, but remarked that these lenses provided better vision compared to the Air Optix lenses. A toric over-refraction OD yielded 20/20 vision in that eye, and an over-refraction of +1.00DS OS improved subjective near vision without disrupting his distance vision. The lenses dispensed at this visit were –1.50 –1.25 x 110 OD and –0.50/1.50 N OS.
At his final follow up, the patient noted great vision at distance and near. He read 20/20 OU and 20/32 OU at near and was finalized in these lenses.
A 46-year-old teacher, who was a new patient to our office, wore single vision distance contact lenses with readers because “no one can fit me in contact lenses.” Her habitual brand and Rx were unknown. She was tired of having to depend on readers, because it made looking between her desk work and her students an inconvenience. She refracted to +4.50 –0.50 x 015 OD and +7.25 –1.25 x 025 OS with a +1.75D add. She did not demonstrate amblyopia.
The trial lenses that I initially selected were Proclear Multifocal (CooperVision) +4.50/2.00D OD and Proclear Toric XR +10.00 –1.25 x 025 OS lenses. At her first follow up, she noted that her distance and near vision were great, but wondered whether her vision at intermediate could be improved. She read 20/20– OU at distance and 20/32 OU at near.
I changed the left eye to +9.50 –1.25 x 025; the right eye was maintained. At her second follow up, she reported that the intermediate vision was now fantastic but the near had suffered. She read 20/20– OU at distance and 20/40 at near.
The right eye was changed to +4.50/1.50D, and the left eye was changed back to the previous lens. I explained to the patient that further changes would not improve either near or intermediate without being at the expense of the other. At her third follow up, she reported that she liked the second lens combination the best because it provided the most acceptable vision at all three distances.
The patient’ final lenses were Proclear Multifocal +4.50/2.00D and Proclear Toric XR +9.50 –1.25 x 025. At her annual exam the following year, the only change that needed to be made was to adjust the distance Rx in the right eye only.
A 51-year-old math teacher, who pilots as a hobby, habitually wore ComfortFlow (Essilor) GPs for distance only. He was starting to notice some blur at near with his contact lenses. Because of his critical distance demand while piloting, he wanted to retain as much distance vision and stereopsis as possible; thus, standard monovision was ruled out as an option. He stated that the comfort and fit in his current lenses was satisfactory, and he did not want to be refit if possible.
The ComfortFlow lens has a diameter of 10.3mm, so it was necessary to find a GP multifocal available in a larger diameter. I ordered a new habitual right lens. For the left eye, I ordered a Dyna Z Multifocal (Lens Dynamics) with parameters of 7.26mm base curve, 10.4mm overall diameter, –6.00D power with a +2.00D add. At his first follow up, he read 20/20 at distance OU, but 20/50 OU at near. He remarked that his distance vision was still perfect, but his near needed work. An over-refraction of +0.25DS OS at distance improved the subjective near vision without much compromise to his distance vision, so we changed the lens to a –5.75DS with a +2.00D add.
At his second follow up, he read 20/20 OU at distance and 20/32 OU at near. He said his distance vision wasn’t as great as with his habitual lenses, but the improvement in his near made up for it, and he was satisfied.
Modified monovision offers a few more options for hard-to-please presbyopic contact lens patients by managing patients’ expectations and uncovering their visual needs. It is important to note that one patient’s version of satisfied will vary from another’s. Thus, when fitting modified monovision, treat every patient and his needs individually. CLS
Contact Lens Spectrum, Volume: 29 , Issue: June 2014, page(s): 55, 56, 58