Acute clouding of hydrophilic acrylic copolymer intraocular lenses:four cases report

Background: Intraoperative acrylic intraocular lenses (IOLs) transient clouding of several kinds of hydrophilic IOLs have been reported due to temperature changes. However, we ignored the particularity of its material and the handling methods. Case presentation: We present four cases of acute clouding of hydrophilic acrylic intraocular lenses (IOLs). Four patients underwent phacoemulsification cataract surgery with implantation of L-312, 809M, and 839M IOLs, respectively. The IOLs became opaque in varying degrees during surgery. Lens replacement was performed immediately in one case, while the cloudy IOLs were remained in the other three cases. Postoperatively, all IOLs recovered transparency. Conclusions Temperature fluctuation was the cause of the acute opacification of these IOLs made of hydrophilic acrylic copolymers, which reminds us of attaching importance to the temperature of IOL storage and delivery in winter months.


Background
Opacity of acrylic intraocular lenses (IOLs) is an uncommon complication during cataract surgery. In the past decade, intraoperative transient clouding of a few kinds of acrylic IOLs has been reported due to temperature changes in winter. [1][2][3][4] In our practice, we encountered four cases of IOL opacification during implantation and evaluated the possible causes. The aim of this report was to emphasize the importance of storage and delivery in an appropriate temperature for hydrophilic acrylic copolymer IOLs and recommend proper handling for such IOL clouding.

Case 1
A 64-year-old woman with a cortex cataract in the right eye received phacoemulsification with implantation of the LENTIS L-312 lens (Oculentis; +21.0 D, SN: 91306104022). It had taken over one hour for the supplyer to deliver the IOL at an outdoor temperature of around −3 °C. After kept in the theater (21 °C) for about 2 hours, the IOL was implanted into the eye, but the lens optic became cloudy immediately (Fig. 1A). This was the first time that we encountered such a situation. The surgeon replaced the IOL with another LENTIS L-312 lens at once, and the same phenomenon was observed (Fig. 1B). The second IOL was not removed, and the surgery was completed. Under a slit-lamp microscope, the opacification was found to be alleviated after 2 hours (Fig. 1C). On postoperative day 1, the IOL became transparent (Fig. 1D). Best corrected visual acuity (BCVA) was improved from preoperative 20/40 to 20/25.

Case 2
Uneventful cataract surgery was performed on the left eye of a 54-year-old man with a cortex cataract, and a +19.5 D acrylic IOL (AL LISA tri 809M; Carl Zeiss, SN 1S1710870057) was implanted. His preoperative BCVA was 20/50. Before implantation, the lens had been stored at room temperature for 1.5 hours following 1-hour transportation at an outside temperature of -8 °C. A few seconds after the IOL was placed into the capsular bag, clouding occurred ( Fig. 2A) and failed to clear after 5 minutes. The surgery was completed. On the following day, the lens was detected to be clear without any abnormality (Fig. 2B), and BCVA was measured to be 20/20.

Case 3
A 62-year-old woman with cortex cataracts in both eyes was scheduled to undergo phacoemulsification. A +21.5 D acrylic IOL (AL LISA tri 809M; Carl Zeiss, SN 1S1713970329) was first implanted into the left eye after 1-hour delivery when the 4 temperature outside was −8 °C and 2-hour placement in the theater. The IOL was transparent prior to implantation (Fig. 3A). As the IOL was implanted into the capsular bag, it became cloudy immediately (Fig. 3B). The opacification disappeared spontaneously on the following day (Fig. 3C). Three days later, another +22.0 D IOL (AL LISA tri 809M; Carl Zeiss, SN 1S1715830258), which had been stored in the theater for 3 days, was inserted into the right eye after cataract extraction, and no opacification occurred.

Case 4
Cataract surgery was uneventfully performed on the left eye of a 46-year-old man with a cortex cataract, and a +19.0 D acrylic IOL (AL LISA tri 839M; Carl Zeiss, SN 1S1706750238) was implanted to correct his vision, which was finger counting before the eye. The IOL was delivered to the theater at an outdoor temperature of −4 °C and 3 hours ahead of the implantation. As the IOL was placed into the eye, it became opacified (Fig.   4A). After irrigation, the IOL started to clear (Fig. 4B).

Discussion
Temperature changes can impact on the biological characteristics of crystals and thus cause IOL opacification. [5][6][7] Acrylics and many other polymers show viscous flows at temperatures above Tg, from their rigid glassy state to soft rubbery state. [8] Lower the Tg of the material, more deformable and easily foldable the lens is. [9] When the environment temperature is low, an unfolded hydrophobic lens becomes hard. [7,8]It was also reported that the change in the equilibrium water content caused by temperature fluctuation between 30 °C and 40 °C is an important factor in glistening formation. [10] Temporary turbidity of acrylic IOLs related to temperature difference is not common, but once it occurs, panic may be generated by both the surgeon and the patient. [1][2][3][4] Replacement of the clouded IOL was performed sometimes. In one report, [3] the patient waited for the substitutional IOL for more than an hour on the operating table. This should be avoided for 5 the increased risk of intraoperative infection.
All our cases occurred in winter, when the outdoor temperatures were below zero Table   1 . We noted that the lower the outdoor temperature, and the shorter the indoor placement time, more seriously the IOLs were affected. In Case 4, the IOL was stored in the room for a comparatively long time, and the turbidity was light and disappeared during surgery. We also found that the clouded IOLs were all hydrophilic acrylate lenses with a hydrophobic surface. Such materials seem to be liable to suffer temporary clouding.
The IOLs of a single material, such as a completely hydrophobic or hydrophilic material (Softec HD, AO, and iSert251), however, were not found to have any acute clouding because of the sudden temperature changes in our institution. Another factor may be the pure water in the sterile bottle which could not rise to the room temperature in a short period of time and was imbibed by the composite lens material from the anterior chamber because of temperature gradient. As a matter of fact, the instructions to the IOLs remind us of the possibility of clouding. For the L-312 lens, it is suggested to be transported at an environment temperature between 5 °C and 50 °C and stored at room temperature for at least 1 hour before use. For the AT LISA 809M crystal, room temperature is indicated at the time of surgery to avoid temporary clouding of the lens optic after implantation.
Fortunately, no permanent structural or mechanical change of the IOLs occurred in our cases. We should attach importance to the manufacturers' recommendation and particularly to the correct storage of IOLs.

Conclusions
In conclusion, this IOL clouding phenomenon, which is rarely encountered clinically, may take place in cold winter months. Hydrophilic acrylic copolymers are more likely to form this temporary turbidity. In light of this knowledge, it is usually unnecessary to replace the IOL. Moreover, the suppliers need to keep a correct warm temperature in the process 6 of transportation and deliver the IOLs in advance in very cold days. It is favorable to store the artificial crystal in the operating room for at least 1 day to avoid any sudden temperature fluctuation in its surrounding environment.