Advanced Presbyopia: Simultaneous Vision Bitoric Multifocal: Derek J. Louie, OD, MSc, FAAO
A 46 year old female presented with an interest in multifocal contact lenses. The patient has a history of high refractive astigmatism and stable distance spectacle prescription.
Test Procedures, Fitting/Refitting, Design and Ordering
Current spectacle prescription/visual acuity (VA):
OD: -4.25 – 3.75 x 166 20/25 -2
OS: -4.75 – 3.75 x 004 20/20
Add: +2.25D OU
Type: Progressive addition lens
OD: -4.00 – 3.75 x 170 20/20, J1+
OS: -5.00 – 2.75 x 003 20/20, J1+
Add: +2/00D OU
OD: 41.50 @ 170; 44.87 @ 080
OS: 41.87 @ 008; 45.12 @ 098
Dominant eye: OS
Horizontal Visible Iris Diameter (HVID): 11 mm OU
Middle of pupil: 5 mm from lower lid OU
Patient Consultation and Education
The key factor with this patient is to select a lens which will hopefully allow good distance and near vision. Certainly there are many good multifocal GP lens designs, both translating and simultaneous vision. A soft toric multifocal may also be an option. Cost may also be a factor as a soft toric multifocal lens – over the lifespan of a GP multifocal – will likely cost more money; after the first 12-24 months as soft toric lenses are replaced more frequently than a multifocal GP lens. Durability and quality of vision will likely be better with a GP multifocal rather than a soft toric lens.
Follow-Up Care/Final Outcome
It was decided to fit this patient into the PlatinumEyes multifocal GP lens design from Valley Contax (Springfield, OR, USA). This is an aspheric front and back surface design. The final prescription ordered for this patient was as follows:
|Base Curve Radius||Back Vertex Powers||Add||Central Optical Zone||Overall Diameter||Material|
OD: 20/25, J2
OS: 20/20, J1+
OU: 20/15, J1
Slit Lamp Evaluation:
Both lenses exhibited apical clearance with no sign of an astigmatic pattern. Average edge clearance and good centration and movement with the blink were also observed.
Discussion/Alternative Management Options
To be successful in contact lens practice and meet every patient’s individual needs it is important to have many tools. A toric multifocal GP lens design is one such tool. This patient’s lens has +1.75D add power on the back surface with 2.5 mm (OD) and 2.0 mm (OS) center and +0.50D front surface with 4.5 mm zone (OU). The peripheral curves are both toric and aspheric. The overall add limit for this lens design is +3.75D, with +1.75D add back surface limit. The reason for the slightly larger central central distance zone in the right lens is the larger overall diameter and to reduce possible glare symptoms.
The primary benefit of a simultaneous vision design multifocal GP lens on a highly toric cornea is centration. Centration of this lens is key to achieving both good distance and near vision.
While a translating design may also be successful, as the result of the nature of a toric back surface contact lens, and its tendency (by design) to stay centered, translation into the add portion of the lens may be limited.
Gromacki, SJ. Monovision and bifocal contact lenses. In Hom, MM, Bruce, AS. Manual of Contact Lens Prescribing and Fitting with CD-ROM (3rd.Ed.) Butterworth-Heinemann, Woburn, MA, 2006:471-497.
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