Features of our IOL models - OptoVet IOL design
FEATURES OF OUR IOL MODELS- OptoVet IOL DESIGN
OptoVet company, Moscow, Russia
An Intraocular Lens (IOL) structurally has two parts: an Optical part or "optics" (actually, the lens is an optical element that provides image focusing) and a Haptic part or "haptics" (support part of the lens) (Fig.1).
With the optical part of the IOL, everything is clear. The lens should correspond (in diameter) to the size of the pupil and its refractive power (refraction) should correspond (or as close as possible) to the refraction of the natural lens. Optics, almost all IOLs-the same (round lens).
The haptic part of the IOL is of great importance for successful implantation in animals and good postoperative functioning. In our IOL models, the haptic part is closed, and has, practically, the shape of a ring. Other veterinary models of IOL have either an open haptics or rectangular haptics (Fig. 2).
What does it matter – now we will explain:
Fact 1. The more the shape of the haptics approaches the circle, the more points of contact between the haptic-supporting elements of the IOL and the lens capsule, and the stronger and more reliable the IOL will hold after implantation. Do you think a dog or cat will take care of the operated eye after the operation? Yes, nothing like that! The animal will run, jump, shake its head, possibly scratch the operated eye, etc. Whether an IOL with a rectangular or open haptics can shift or even fall out of the capsule bag on impact – YES, it can easily. Whether our IOL (OptoVet IOL) with a closed haptics can shift or fall out – NO, it can't, because it is very firmly and reliably held. In order to displace our IOL from its normal position, you need to destroy the eye completely – and this is a completely different story…
Fact 2. In order for the animal to see clearly after implantation of the IOL, the optical part of the IOL must be located exactly in the center of the capsule bag and, accordingly, exactly in the center of the pupil. However, not all operations go smoothly… During surgery, blood or fibrin may enter the capsule bag; the capsule itself may be wrinkled, uneven, degenerated, fibrosed, or even torn. In such cases (and they are not so rare), our IOL (OptoVet IOL) with a round closed haptics, in any case, will automatically position the lens optics in the center of the capsule bag. Even if the capsule bag is uneven or torn, even if the pupil and iris are initially deformed (for example, in trauma), the optical part of our IOL will still stand exactly in the center.
IOL with a different form of haptics will stand, as it will put the doctor on the operation: put straight – to stand up straight, put crooked – will be askew. And if, for example, the capsule bag is initially uneven (see above)? And if intraocular bleeding started (even a small one), after the implantation and the end of the operation? And if the animal shakes its head violently and the IOL shifts due to vibration? And if, in the end, the doctor is not very experienced and the IOL is not placed in the center? In all these situations, the IOL will stand crooked. If the IOL is crooked – the zonular fibers will be overloaded, stretching the capsule bag more and more, deforming the pupil, which, in the end, can lead to secondary luxation of the already implanted lens along with the capsule bag. And we have seen this in our practice (it is good that after someone else's operations, but it is still sad).
Fact 3. Ideally, capsulorexis (the opening in the front capsule through which we remove the lens) should be flat, located exactly in the center, and, in diameter, be slightly smaller than the diameter of the optical part of the IOL. In this case, the IOL after implantation will rest the edges of its optical part on the edge of the capsulorexis and will not tend to exit (fall out) from the capsule bag (Fig. 3-capsulorexis is drawn in red).
For the situation shown in Figure 3 (see above), all IOLs, regardless of the shape of the haptics, will stand normally. But if the capsulorexis is uneven or too large, or if a part of the anterior capsule is torn off (the doctor is inept, or the capsule is initially torn, or just "something went wrong"..), how will IOL behave in this case?
Our IOL (OptoVet IOL), as they say," does not matter " what capsulorexis. It has a very large contact area of haptic elements and will still stand flat and solid, as long as there is at least a little capsule for which the haptics can "catch"... (Figure 4 - capsulorexis is drawn in red). Even if at least two of the four supporting haptic "petals" are securely standing, the IOL will not fall out anywhere.
However, IOLs with a different form of haptics may fall out. The IOL with rectangular haptics can easily fall out if it is at least slightly shifted (scrolled) in the capsule bag. IOL with closed haptics will fall out very easily with a large diameter of capsulorexis (Figure 5-capsulorexis is drawn in red).
Fact 4. In complex cataracts (traumatic, uveal, morganic, etc.), a significant part or even the entire anterior capsule may be optically opaque, or contain inflammatory elements, fragments of fibrin and blood, or degenerated remnants of the lens substance. In such cases, the larger the volume of the anterior capsule we remove, the better the visual functions will be, and fewer complications will occur in the operated animal. However, the design of conventional IOLs does not allow you to remove a large volume of the front capsule, because they simply will not hold. And only the design of our IOLs (OptoVet IOLs) allows you to remove most of the clouded front capsule, without compromising the reliability of holding the IOL (Figure 6-capsulorexis is drawn in red).
Remember: an operated dog or cat will NOT take care of or protect the operated eye. The reliability of IOL fixation in the capsule bag is one of the most important factors determining success after surgery, and the most important factor in operations on severe traumatic cataracts. Thus, the design of our IOL (OptoVet IOL) models provides tremendous advantages in animal operations.
In addition, uniform stretching of the capsule bag in all directions after implantation of IOL (the so-called capsule-ring effect), according to some data (medical), prevents or slows down the formation of secondary cataracts (fibrosis of the posterior capsule in the long postoperative period).