Eyeworld

DECEMBER 2019 | EYEWORLD | 21 to translate into clinically relevant benefits at one month postop. One limitation of the study is the overall short duration of follow up, making it unclear whether the initial findings might translate into long-term differences in visual outcomes or complications. Also, we found ourselves inter- ested in a few additional pieces of information in order to better interpret the overall findings. First, it would be helpful to have the data from the preoperative animal and clinical measured corneal parameters to determine whether there was a statistically significant difference between the groups prior to phacoemulsification. While the paper indicates this data was collected, it is not made available. This would enhance the analysis of whether the postoperative results were significant by comparing pre- and post- operative values within and across each of the test groups. Additionally, it would help us better interpret how the statistically significant endo- thelial cell count difference between the 4°C and 24°C groups reported at postoperative day 1 changed by postoperative day 7, at which time there was no longer a statistically significant difference between the groups. This possibly suggests a delayed cell dropout in the 4°C group but would be better understood in the setting of the preoperative data. Second, when analyzing the temperature differences seen in a figure in the study, it is unclear why the authors are demonstrating the data as a linear progres- sion when comparing AC temperatures before and during phacoemulsification to incision temperature during surgery. The data for inci- sion temperatures prior to surgery is also not included. This data may be better represented as a table with the addition of the incision tem- perature before phacoemulsification. There are a few technical aspects of lens insertion and phacoemulsification in these cases that should be considered as well. From a surgeon's perspective it may be important to account for differences in acrylic IOL unfolding due to changes in fluid temperature. 7 The rate of lens unfolding could impact the final lens incision. The animal study evaluated intraocular perfusion temperature of 4˚C, 10˚C, and 24˚C while the randomized trial evaluated intraocular perfusion temperatures of 4˚C and 24˚C. Postoperative ophthalmic evaluation in- cluded the patient's best-corrected visual acuity (BCVA), slit-lamp examination of the anterior and posterior segments, intraocular pressure (IOP), and a dilated fundus examination. Ad- ditionally, anterior segment OCT, fundus OCT, corneal endothelial cell count, central corneal thickness (CCT), and AC inflammatory cell count were obtained on the 1st and 7th postop- erative day. Subjects were followed for 30 days after surgery. Results In both the animal and clinical studies, the au- thors found a statistically significant difference between the 4°C and 24°C groups at postoper- ative day 1 with regard to CCT and AC inflam- mation, with the 4°C group having a lower CCT and grade of AC inflammation. In the animal trial, there was no difference between the 4°C and the 10°C groups. The clinical trial also found the 4°C group had a higher endothelial cell density and hexagonal morphology when compared to the 24°C group at postoperative day 1, which was statistically significant. Interestingly, none of the statistically significant differences seen at day 1 remained significant at postoperative day 7 or 30 in either the animal or clinical model. The differenc- es between the 4°C and 24°C group did not translate into clinically or statistically significant differences in postoperative visual acuity or surgical complications, such as transient IOP elevation or macular edema. Analysis The findings of this study suggest that perfu- sion with a 4°C fluid may be safe and protective against inflammation in the early postoperative period. Cooling perfusion fluid appears to blunt the overall fluctuation in temperature changes in the AC that can be associated with phacoemul- sification in hard cataracts. However, this reduc- tion in temperature variability does not appear Perfusion on Phacoemulsification a Randomised Trial" References 1. Cataract Data and Statistics 2010. National Eye Institute 2019. 2. Lindstrom R. Thoughts on cataract surgery. Review of Ophthalmology. 2015. 3. Zeng M, et al. Torsional ultra- sound modality for hard nucleus phacoemulsification cataract extraction. Br J Ophthalmol. 2008;92(8):1092–1096. 4. Bissen-Miyajima H, et al. Ther- mal effect on corneal incisions with different phacoemulsification ultrasonic tips. J Cataract Refract Surg. 1999;25:60–64. 5. Joussen A, et al. Effect of irrigating solution and irrigation temperature on the cornea and pupil during phacoemulsifica- tion. J Cataract Refract Surg. 2000;26(3):392–397. continued on page 22

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