Soft contact lenses that correct astigmatism are called “Toric” lenses. “Toric” comes from the root word “Toroid”. A toroidal surface in geometry is a surface with two curves at 90° angles to each other.
Toric soft contact lenses have two curves and two powers at right angles to each other. These powers must be rotationally stable on the eye for optimal vision. If the bottom of the contact lens rotates nasally (towards the nose) or temporally (away from the nose), your vision will be compromised. Rotational stability is of paramount importance with toric contact lenses.
Accordingly, soft toric lenses have multiple design features to create rotational stability. The most common design element to encourage this is prism ballasting (or peri-ballasting). Essentially, the bottom of the lens is thicker than the top. This causes the thicker bottom of the lens to ride down. Gravity may play a small role in stabilizing a prism ballast lens, but the main reason the thicker bottom of the lens rides down because the upper eyelid presses harder on the eye during a blink than the lower lid. This causes the thicker part of the lens to move away from the greater force of the upper lid. This is sometimes referred to as the “pumpkin seed effect”.
Often in patients with higher eyelids, standard prism ballast lenses are unstable rotationally. These patients often do better in regards to both vision and comfort with what I call a “double slab-off” toric contact lens. These lenses are thinner on the top and bottom, and are thicker in the middle. Thus the opposing forces of the upper and lower lids stabilize the lens on the eye.
During a contact lens fitting for patients with astigmatism, I usually place both a prism ballast contact lens design and a double slab-off design lens on the patient’s eye. Usually I will prescribe the lens that looks the most rotationally stable on the eye. Often “uptight” lids do best with double slab-off designs, and patients who have loose eyelids or eyes where the upper and lower lids are far apart (large apertures) tend to do better with a prism ballast design.
Steven Lutz, OD
Serving Ann Arbor, Saline, Ypsilanti, Pinckney, Milan, Dexter, Chelsea, Brighton, Howell, Whitmore Lake and surrounding areas since 1988.
Wednesday, February 24, 2010
Wednesday, February 17, 2010
All Aboard For Sharing
Several years ago, when I would babysit for my granddaughter, Savannah, she used to force me to watch Barney videotapes for hours on end. Her favorite tape was “All Aboard For Sharing”. I thought about this recently when I sat down to write my blog about multifocal (bifocal) contact lenses.
Soft multifocal contact lenses are all about sharing pupil space. A soft multifocal contact lens has a reading zone, a distance zone, and usually an intermediate zone, all centered within the pupil of the eye.
This is fundamentally different from a bifocal (lined) lens or a progressive (no-line) lens for your glasses. With glasses, by looking straight ahead, you fill both pupils of the eyes with far (distance) vision rays of light. To fill both pupils with near (reading) rays of light, you need to look down with your eyes and look through the lower portion of the glasses.
By having two independent areas of the lens, glasses are therefore better visually than multifocal contact lenses, which must place both far and near rays of light in the pupil simultaneously.
Glasses, of course, are not perfect. They are literally a “pain in the neck” if you are trying to view a computer screen placed straight ahead of you. You have to tilt your head back to adjust your line of sight so you are looking through a lower point in your lenses to get the proper corrective power in front of your pupil!
Multifocal contact lenses are much better in this situation. By looking straight ahead, the contact lens places the near vision correction on the retina. No head tilting needed!
When my patients come in for their eye exam, I always ask what situations they find themselves in on a daily basis. Glasses are a bit better for certain tasks, such as prolonged reading or long distance night driving, but most patients find (myself included!) they prefer multifocal contact lenses for most everyday tasks.
The next time you go to see your optometrist for your eye care, ask about the possibility of having a contact lens fitting for a multifocal contact lens, and see for yourself why a multifocal contact lens will have you “all aboard for sharing”.
Steven Lutz, OD
Serving Ann Arbor, Saline, Ypsilanti, Pinckney, Milan, Dexter, Chelsea, Brighton, Howell, Whitmore Lake and surrounding areas since 1988.
Soft multifocal contact lenses are all about sharing pupil space. A soft multifocal contact lens has a reading zone, a distance zone, and usually an intermediate zone, all centered within the pupil of the eye.
This is fundamentally different from a bifocal (lined) lens or a progressive (no-line) lens for your glasses. With glasses, by looking straight ahead, you fill both pupils of the eyes with far (distance) vision rays of light. To fill both pupils with near (reading) rays of light, you need to look down with your eyes and look through the lower portion of the glasses.
By having two independent areas of the lens, glasses are therefore better visually than multifocal contact lenses, which must place both far and near rays of light in the pupil simultaneously.
Glasses, of course, are not perfect. They are literally a “pain in the neck” if you are trying to view a computer screen placed straight ahead of you. You have to tilt your head back to adjust your line of sight so you are looking through a lower point in your lenses to get the proper corrective power in front of your pupil!
Multifocal contact lenses are much better in this situation. By looking straight ahead, the contact lens places the near vision correction on the retina. No head tilting needed!
When my patients come in for their eye exam, I always ask what situations they find themselves in on a daily basis. Glasses are a bit better for certain tasks, such as prolonged reading or long distance night driving, but most patients find (myself included!) they prefer multifocal contact lenses for most everyday tasks.
The next time you go to see your optometrist for your eye care, ask about the possibility of having a contact lens fitting for a multifocal contact lens, and see for yourself why a multifocal contact lens will have you “all aboard for sharing”.
Steven Lutz, OD
Serving Ann Arbor, Saline, Ypsilanti, Pinckney, Milan, Dexter, Chelsea, Brighton, Howell, Whitmore Lake and surrounding areas since 1988.
Wednesday, February 10, 2010
One Day (Single Use) Contact Lenses
My name is Dr. Steven Lutz. I am an optometrist in Ann Arbor, MI along with Dr. Lesley Beebe. My office is located inside the Lenscrafters at the Briarwood Mall.
I have a very large contact lens practice. During routine eye exams, I fit many patients with complex prescriptions, including patients that have astigmatism or presbyopia (the need for help with their reading, mostly in patients over the age of 40).
Of course, we also do contact lens fittings for many patients that have straightforward prescriptions for myopia (near-sightedness) and hyperopia (far-sightedness). Many more of these patients are being fit with one day contact lenses, as opposed to the traditional two week or monthly contact lens. These lenses are worn once and then thrown away - no cleaning, no storage, fresh lenses every day!
There are many advantages to these one day contact lenses:
1: No contact lens solution hassle or cost. This is a supremely easy way to wear contact lenses. Solution will cost a patient about $75 / year. This cost is eliminated with one day contacts.
2: Brand new lenses are very comfortable. As a contact lens ages, often the comfort and wettability goes downhill. Discuss the comfort of your current lenses with your doctor during your eye exam. A one day contact lens patient has new lens comfort every day.
3: Time-released artificial tears & advanced polymers. Many one day lenses have time-released artificial tears built in that deal with dry eye problems very well. Other one day designs have technology that binds water tightly to the contact lens polymer, keeping the lens moist all day long.
It is true that most one day contact lenses may cost a bit more for your year supply than traditional disposable contact lenses. However, when you factor in the savings gained by eliminating contact lens solution and the hefty rebates available from the manufacturers (most are between $80 to $100!), as well as the health benefits of a new lens every day, the cost of one day contact lenses is usually only $3 to $5 more a month! You may find the health benefits of a daily disposable lens outweigh the extra $3-$5 per month.
When talking with your eye doctor about your eye care, be sure to discuss all the benefits of one day contact lenses to see if these lenses are the right fit for you!
I have a very large contact lens practice. During routine eye exams, I fit many patients with complex prescriptions, including patients that have astigmatism or presbyopia (the need for help with their reading, mostly in patients over the age of 40).
Of course, we also do contact lens fittings for many patients that have straightforward prescriptions for myopia (near-sightedness) and hyperopia (far-sightedness). Many more of these patients are being fit with one day contact lenses, as opposed to the traditional two week or monthly contact lens. These lenses are worn once and then thrown away - no cleaning, no storage, fresh lenses every day!
There are many advantages to these one day contact lenses:
1: No contact lens solution hassle or cost. This is a supremely easy way to wear contact lenses. Solution will cost a patient about $75 / year. This cost is eliminated with one day contacts.
2: Brand new lenses are very comfortable. As a contact lens ages, often the comfort and wettability goes downhill. Discuss the comfort of your current lenses with your doctor during your eye exam. A one day contact lens patient has new lens comfort every day.
3: Time-released artificial tears & advanced polymers. Many one day lenses have time-released artificial tears built in that deal with dry eye problems very well. Other one day designs have technology that binds water tightly to the contact lens polymer, keeping the lens moist all day long.
It is true that most one day contact lenses may cost a bit more for your year supply than traditional disposable contact lenses. However, when you factor in the savings gained by eliminating contact lens solution and the hefty rebates available from the manufacturers (most are between $80 to $100!), as well as the health benefits of a new lens every day, the cost of one day contact lenses is usually only $3 to $5 more a month! You may find the health benefits of a daily disposable lens outweigh the extra $3-$5 per month.
When talking with your eye doctor about your eye care, be sure to discuss all the benefits of one day contact lenses to see if these lenses are the right fit for you!
Wednesday, February 3, 2010
Naturally Wettable Comfort - Lens Provides Astigmatic Patients with Comfort and Corneal Stability
Toric contact lens wearers demand two things from their contact lenses - great comfort and great vision. Contact lens practitioners demand a lens that can be predictably fit with a minimum of chair time. A wearing schedule that encourages patient compliance is a big plus also. Biofinity Toric, the latest new silicone hydrogel from CooperVision, meets all of these demands. It combines a great soft lens material, comfilcon A, with an excellent toric design.
I have been using Biofinity Toric in my office since early January 2009. I have fit more than 40 patients with this product, and I have been very impressed with this lens. I feel the Biofinity Toric is the best toric contact lens that has ever entered the marketplace.
Comfort
Biofinity Toric is made with the polymer comfilcon A. Comfilcon A is naturally wettable, has a low modulus, offers a high Dk (128), and it is approved for extended wear for up to six nights/seven days.
The polymer is inherently very wettable. Biofinity Toric has a low wetting angle, allowing water to spread out evenly on the lens surface. It does not require a wetting agent or surface treatment (plasma) to be hydrophilic and wet properly. CooperVision's Aquaform Comfort Science creates a naturally hydrophilic contact lens that retains water within the lens, which minimizes dehydration. Biofinity Toric, being naturally wetable, offers exceptional deposit resistance and comfort.
The low modulus means that Biofinity Toric is not stiff, but rather is quite soft and "spongy," also helping to deliver great comfort. The massive oxygen flow (DK = 128) ensures great end-of-day comfort for those extra-long wearing times that many patients experience.
Vision
Biofinity Toric is made with a toric design that provides remarkably crisp vision. CooperVision started with its tried-and-true horizontal iso-thickness design, found in Biomedics Toric, and fine-tuned it to perform with the newer material.
I've always had great success with the Biomedics Toric design, finding it very stable rotationally, but wished that I could have more oxygen delivered to the cornea. Obviously, the oxygen issue has been addressed, but I've found the Optimized Ballast Design of Biofinity Toric to be even more stable than the Biomedics lens, which produces improved visual acuity.
Quick fit/patient compliance
CooperVision also got the little things right with Biofinity Toric. The lens has a single orientation mark at 6 o'clock, and it is very easy to see. This sounds very basic, and it is, but its ease of visibility is a great time saver when fitting the patient. Also, the lens handles well, and it's easy to tell when the Biofinity Toric is inside-out.
I also like the fact that the lens is designed for monthly replacement. In my office, the best compliance, by far, is seen with one-day and one-month replacement products.
Biofinity Toric is currently available in plano to -6.00; cylinders of -0.75, -1.25, and -1.75; and axis of 10 to 180. Plus powers and a -2.25 cylinder will be available August 1.
Biofinity Toric has quickly become the "workhorse" soft toric contact lens in my office. Both the lens material and lens design are excellent. I encourage you to try Biofinity Toric in your practice. I think you will be very pleased with the results.
I have been using Biofinity Toric in my office since early January 2009. I have fit more than 40 patients with this product, and I have been very impressed with this lens. I feel the Biofinity Toric is the best toric contact lens that has ever entered the marketplace.
Comfort
Biofinity Toric is made with the polymer comfilcon A. Comfilcon A is naturally wettable, has a low modulus, offers a high Dk (128), and it is approved for extended wear for up to six nights/seven days.
The polymer is inherently very wettable. Biofinity Toric has a low wetting angle, allowing water to spread out evenly on the lens surface. It does not require a wetting agent or surface treatment (plasma) to be hydrophilic and wet properly. CooperVision's Aquaform Comfort Science creates a naturally hydrophilic contact lens that retains water within the lens, which minimizes dehydration. Biofinity Toric, being naturally wetable, offers exceptional deposit resistance and comfort.
The low modulus means that Biofinity Toric is not stiff, but rather is quite soft and "spongy," also helping to deliver great comfort. The massive oxygen flow (DK = 128) ensures great end-of-day comfort for those extra-long wearing times that many patients experience.
Vision
Biofinity Toric is made with a toric design that provides remarkably crisp vision. CooperVision started with its tried-and-true horizontal iso-thickness design, found in Biomedics Toric, and fine-tuned it to perform with the newer material.
I've always had great success with the Biomedics Toric design, finding it very stable rotationally, but wished that I could have more oxygen delivered to the cornea. Obviously, the oxygen issue has been addressed, but I've found the Optimized Ballast Design of Biofinity Toric to be even more stable than the Biomedics lens, which produces improved visual acuity.
Quick fit/patient compliance
CooperVision also got the little things right with Biofinity Toric. The lens has a single orientation mark at 6 o'clock, and it is very easy to see. This sounds very basic, and it is, but its ease of visibility is a great time saver when fitting the patient. Also, the lens handles well, and it's easy to tell when the Biofinity Toric is inside-out.
I also like the fact that the lens is designed for monthly replacement. In my office, the best compliance, by far, is seen with one-day and one-month replacement products.
Biofinity Toric is currently available in plano to -6.00; cylinders of -0.75, -1.25, and -1.75; and axis of 10 to 180. Plus powers and a -2.25 cylinder will be available August 1.
Biofinity Toric has quickly become the "workhorse" soft toric contact lens in my office. Both the lens material and lens design are excellent. I encourage you to try Biofinity Toric in your practice. I think you will be very pleased with the results.
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