Ординатура / Офтальмология / Английские материалы / The Art of Phacoemulsification_Mehta, Alpar_2001
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THE ART OF PHACOEMULSIFICATION
Fig. 26.11: The lens is held and ready for implantation. Excessive pressure is not necessary to keep folding the lens. The loop should not be folded inside the optic (tucking)
Fig. 26.14: Once the leading haptic is placed beneath the capsulorrhexis margin, the implantation forceps is rotated clockwise
Fig. 26.12: By pronating (rotating counterclockwise) the hand and implantation forceps, the leading haptic is placed into the tunnel and implanted into the anterior chamber. The closed part of the optic is on the left side
Fig. 26.13: As the optic enters the tunnel, the implantation forceps is redirected posteriorly so that the distal haptic is inserted beneath the opposite anterior capsule margin and into the capsular bag. It is very important to guide the distal haptic into the capsular bag before the whole optic enters and opens in the anterior chamber
Fig. 26.15: Opening the forceps allows the optic to slowly unfold and be disengaged from the forceps
nature of the acrylic foldable optic facilitates this procedure. Instead of the forceps, a lens hook may be used for the implantation of trailing haptic.
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Fig. 26.16: The optic is depressed and rotated by the implantation forceps
Fig. 26.17: The proximal haptic is implanted into the capsular bag
Fig. 26.18: Adequate positioning of the optic within the implantation forceps is crucial for smooth insertion procedure (A). If the forceps grasp too peripheral portion of the optic (too low down, B), a second instrument is needed to release the lens which had been caught between the forceps. If it is too central (too high, C), a stressful force will be exerted on the folded portion of the optic, which may possibly result in the cracking or fracturing of the lens
Adequate positioning of the optic within the implantation forceps is crucial for the smooth insertion procedure. If the forceps grasp too peripheral portion of the optic (Fig. 26.18), the lens may be caught between the forceps (Fig. 26.19) and a second instrument is needed to disengage the lens (Fig. 26.20). If it is
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Fig. 26.19: Left : standard unfolding. Right: the lens is engaged between the forceps due to inadequate grasping location
Fig. 26.20: A second instrument is needed to release the lens which had been caught between the forceps
Fig. 26.21: Since the forceps does not cover the optic sufficiently, the leading edge of the optic forms “fish mouth”, preventing smooth entry through a small incision
too central (Fig. 26.18), a stressful force will be exerted on the folded portion of the optic, which may possibly result in the cracking or major damaging of the lens.
As for the horizontal positioning of the forceps, forceps is supposed to cover just the entire width of the optic. If the tip of forceps remains far inside the lens edge, the leading edge of the optic will form “fish mouth”, preventing the smooth entry through a small incision (Fig. 26.21). On the other hand, when the forceps exceed the edge too much, the tip of the forceps may be unnecessarily captured by the tissue within the scleral tunnel.
Several other instruments are available for implantation of acrylic foldable IOL. The folding forceps shown in Figure 26.22 engages both edges of the optic by
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Fig. 26.22: Paddle-type folding forceps
Fig. 26.24: By closing the forceps, the lens is folded into halves
the groove made on the inner wall of the jaw (Fig. 26.23). By closing the forceps, the lens is folded into halves (Fig. 26.24).
The lens may be folded using two straight or curved forceps (Fig. 26.25) without any specially designed folders.
Curved type implantation forceps (Fig. 26.26) may facilitate the disengagement of the lens from the forceps within the eye, since they will produce a wider space between the jaws (Fig. 26.27), making the lens capture less likely. However, a wider
incision is needed for the passage of this
forceps due to its configuration, and intraocular maneuverability (i.e. rotating the lens) is not as good as the straight forceps. Cross-action forceps will produce
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Fig. 26.27: Curved type forceps facilitates the disengagement of the lens from the forceps within the eye, since they produce a wider space between the jaws. However, a wider incision is needed for the passage of this forceps due to its configuration, and intraocular maneuverability (i.e. rotating the lens) is not as good as the straight forceps
Fig. 26.28: Implantation with cross-action forceps
even wider space between the jaws (Figs 26.28 and 29).
There is a report that MA30BA can be implanted with an injector designed for silicone IOLs.6 At the present writing, a new injector system for acrylic foldable IOL is being developed (Figs 26.30 to 35).
INTRAOPERATIVE COMPLICATIONS
In cases of posterior capsule rupture, acrylic foldable IOL can be implanted out of the capsular bag. When capsulorrhexis margin is intact, it is easy to place the IOL on the anterior capsule. If the remaining capsular and zonular supports are insufficient, trans-scleral suture fixation will be considered, for which acrylic foldable IOL can also be used.
Since the optic of acrylic foldable lens is more fragile than other foldable IOLs
Fig. 26.29: Cross-action forceps produce wider space between the jaws
including silicone lens,7 tight incision, prolonged and/or repeated folding, and extremely firm grasping sometime result in scratch formation7,8 or cracking/fracturing of the optics (Figs 26.36 and 37).9-11 Incorrect instrumentation can be the causative factor of this phenomenon in some cases.12,13
Except for a rare case in which extremely severe damage occurred,11 ordinary crack formation does not necessitate explantation of the acrylic foldable IOL. This is because mild to moderate linear cracks are not likely to affect the optical quality of the lens.14 An experimental study indicated that the modulation transfer function
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Fig. 26.30: An injector system for acrylic foldable IOL (MonarchTM IOL Delivery System). The system consists of two parts: an autoclavable, reusable titanium handpiece and a sterile, singleuse cartridge
Fig. 26.31: The cartridge is filled with viscoelastic, immediately prior to loading the lens into the cartridge
Fig. 26.32: The optic edge of the lens is grasped with the holding forceps and the lens is placed anterior side up into the back of the cartridge
(MTF) and resolving power of acrylic foldable IOL were not affected by a few linear cracks created on the optic (Fig. 26.38).14 Likewise, prolonged folding had little influence on the optical quality of the lens (Fig. 26.39).
E X P L A N T A T I O N
Explantation of acrylic foldable IOL might be necessary in some cases, possibly due to inadequate power calculation, severe damage of the lens, malpositioning of the lens, and so on. There are two ways to explant the acrylic foldable lens
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Fig. 26.33: The lens should be inserted until it is centered with the outline etched into the top of the cartridge. The trailing haptic will extend from the proximal end of the cartridge. With forceps closed and both blades extending across the optic, press down gently and evenly on the top optic surface, ensuring the lens is positioned on the bottom surface of the cartridge. Accurate positioning of the lens will decrease the potential for optic and haptic damage
Fig. 26.34: The cartridge is inserted into the handpiece (1) and the cartridge is fully slid forward into the handpiece slot (2)
Fig. 26.35: Advance the plunger in one slow motion, ensuring that the plunger goes either above or below the trailing haptic. The plunger should make initial contact with the cartridge at the ramp
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Fig. 26.36: A linear crack formed on the optic. Patient’s vision is not affected
Fig. 26.37: A linear fracture of the optic developed during repeated foldings and attempts to insert the lens through a very tight incision
Fig. 26.38: Modulation transfer function (MTF) with linear cracks created at the central 3 mm zone of the optic surface using a cutter. With cracks up to 10 lines per 3 mm, there were no noticeable changes in MTF. When 10 or more cracks were created, MTF worsened significantly at all spatial frequencies
through the original unenlarged small incision; intraocular bisection15 and re-folding in the anterior chamber.16
The acrylic foldable IOL can be easily cut with conjunctival or Vannas scissors. The procedures are as follows:
First, the anterior chamber is filled with viscoelastic material, and the lens is rotated out of the capsular bag into the anterior chamber. Two Sinskey hooks may be used, one of which is inserted underneath the optic to lift the lens. Then additional viscoelastic material is injected under and over the IOL. While the
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Fig. 26.39: Modulation transfer function (MTF) measured after prolonged folding of the acrylic foldable IOL. Measurements were taken 30 minutes after unfolding. MTF was not affected significantly by any procedures
Fig. 26.40: While the distal edge of the optic is supported by the hook inserted through the side port, the scissors are introduced to bisect the optic
Fig. 26.41: Care should be taken not to damage the posterior capsule and corneal endothelium
distal edge of the optic is supported by the hook inserted through the side port (Fig. 26.40), the scissors are introduced to bisect the optic (Fig. 26.41). Care should be taken not to damage the posterior capsule and corneal endothelium. The two pieces of the divided lens is now grasped with toothed forceps and removed from the anterior chamber through the original small incision (Figs 26.42 and 43).
There is another way to cut the optic. If a quarter is removed (Fig. 26.44), the remaining three quarters will be explanted through the unenlarged incision by rotation around the wound.
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Fig. 26.42: The lens is completely divided into halves
Fig. 26.43: The two pieces of the divided lens is grasped with toothed forceps and removed from the anterior chamber through the original small incision
Fig. 26.44: A quarter has been cut and removed
A technique has been reported to refold the acrylic foldable IOL in the anterior chamber.16 Although this technique also enables the explantation of acrylic foldable IOL through the original or slightly enlarged incision, IOL bisection seems less complicated and traumatic.
Acrylic foldable IOL strongly adheres to the lens capsules.17 Adhesion force is significantly higher than PMMA and silicone IOLs. When extensive adhesion between the IOL and the surrounding ocular structures exists, the explantation surgery will be more complicated and difficult.16 Therefore, the explantation or exchange surgery of acrylic foldable IOL, if necessary, should be performed before a long interval from the primary surgery. It is supposed that the critical time point is 2 to 3 months after the implantation surgery.
CLINICAL DATA
As reported previously, postoperative courses are highly satisfactory.18 Postoperative visual acuity data were analyzed in 200 eyes of 200 patients who underwent phacoemulsification and implantation of acrylic foldable IOL. As shown in Figure 26.45, more than 95 percent of patients achieved best-corrected visual acuity (BCVA) of 20/40 or better, and more than 80 percent attained the level of 20/20. The results of uncorrected visual acuity (UCVA) were excellent likewise.
Interestingly and importantly, the incidence of posterior capsule opacification (PCO) is extremely low with acrylic foldable IOL. Our analysis of posterior