1) The authors ask the original study authors to clarify whether gas-forced infusion was used during surgery, as it prevents endothelial cell loss by decreasing intraoperative surges. 2) In their own previous study, the authors found lower endothelial cell loss with gas-forced infusion compared to without it. 3) Several techniques can maintain stability during biaxial phacoemulsification, and gas-forced infusion is one successful method to prevent surges.

1. LETTERS
Gas-forced infusion prevents endothelial cell Amar Agarwal, MS, FRCS, FRCOphth
loss in phacoemulsification Dhivya Ashok Kumar, MD
Athiya Agarwal, MD, DO
In their recent study comparing endothelial cell Chennai, India
loss in longitudinal and torsional biaxial small-
incision phacoemulsification techniques, Gonen et al.1
found no significant difference between the 2 REFERENCES
techniques. In this context, we would like the authors 1. Gonen T, Sever O, Horozoglu F, Yasar M, Keskinbora KH.
Endothelial cell loss: biaxial small-incision torsional phacoemulsi-
to clarify whether gas-forced infusion (air pump)2 fication versus biaxial small-incision longitudinal phacoemulsifi-
was an option in any of these eyes during surgery. cation. J Cataract Refract Surg 2012; 38:1918–1924
The use of gas-forced infusion prevents endothelial 2. Agarwal A, Agarwal S, Agarwal A. Antichamber collapse.
cell loss by decreasing the intraoperative surge.2 A J Cataract Refract Surg 2002; 28:1085–1086
gas-forced infusion system is connected through 3. Chaudhry P, Prakash G, Jacob S, Narasimhan S, Agarwal S,
Agarwal A. Safety and efficacy of gas-forced infusion
a nitrocellulose membrane air filter to the infusion (air pump) in coaxial phacoemulsification. J Cataract Refract
fluid bottle. The air filter prevents contaminants in Surg 2010; 36:2139–2145
the operating room air from entering the eye. The 4. Agarwal A, Agarwal A, Agarwal S, Narang P, Narang S. Phakonit:
air pump produces a positive pressure head above phacoemulsification through a 0.9 mm corneal incision.
the fluid in the bottle, significantly increasing the J Cataract Refract Surg 2001; 27:1548–1552
5. Agarwal A, Kumar DA, Jacob S, Agarwal A. In vivo analysis of
amount of fluid entering the eye and balancing the wound architecture in 700 mm microphakonit cataract surgery.
excess outflow occurring when the occlusion is J Cataract Refract Surg 2008; 34:1554–1560
broken. It also blunts the fluctuations in intraocular
6. Perez-Arteaga A. Anterior vented gas forced infusion system of
pressure. In our prospective study of gas-forced the Accurus surgical system in phakonit. J Cataract Refract
infusion in longitudinal phacoemulsification,3 we Surg 2004; 30:933–935
noted that the mean endothelial cell loss was lower
in the infusion group than in the control group Reply : Surge is one of the important factors that
(6.98% G 8.46% [SD] versus 10.54% G 11.24%, cause endothelial cell loss during phacoemulsifica-
PZ.045). tion.1 Currently, especially with the coaxial method,
Gonen et al. used a 19-gauge irrigating chopper for the intraoperative surge rate has decreased signifi-
irrigation and a 20-gauge phaco tip for aspiration. cantly thanks to enhanced phacoemulsification
The intraoperative vacuum was set at 250 mm Hg systems.2 However, it can be a problem with the biax-
and the flow rate at 30 mL/min. However, despite ial method. Several techniques to maintain anterior
the claimed anterior chamber stability, the endothe- chamber stability during biaxial phacoemulsification
lial cell loss exceeded 35% in both groups.1 In our have been described. Gas-forced infusion (air pump)
study, the cell loss was 6.98% G 8.46% in eyes that is one that is successfully used to prevent surge.3 In
had phacoemulsification with gas-forced infusion our study, we did not need this technique to maintain
but 10.54% G 11.24% in eyes without gas-forced in- anterior chamber stability. Our preferred phacoemul-
fusion. Gonen et al.1 should have calculated the inci- sification parameters (vacuum, 250 mm Hg; aspiration
dence of intraoperative surge, which can affect the flow rate, 30 mL/min; bottle height, 110 cm) and
endothelial loss. From our experience with phakonit,4 instruments (20-gauge sleeveless phaco tip and
we noted that an air pump deepens the anterior 19-gauge irrigating chopper) successfully prevented
chamber, increasing the surgical space available for the intraoperative surge.
maneuvering, and thus prevents complications such As is well known, high ultrasound power, long
as posterior capsule tears and corneal endothelial ultrasound time, and high total balanced salt solution
damage. The phenomenon of surge is neutralized volumes are the most important intraoperative
by rapid inflow of fluid at the time of occlusion machine-related factors in excessive endothelial cell
break. The irrigating chopper and the bimanual irri- loss after phacoemulsification in healthy eyes with no
gation/aspiration of a 22-gauge will provide better history of intraocular surgery, pseudoexfoliation, or
chamber stability. In our analysis of wound architec- corneal dystrophy.4 High-density nuclear cataract,
ture, we noted that good endothelial alignment was increased infusion volume, and a large nucleus are
seen in eyes with microphakonit (with gas-forced independent predictors of endothelial cell loss in
infusion) as early as 3 days postoperatively.5 We coaxial torsional phacoemulsification.5 In our study,
would like to recommend the use of air-forced infu- there was a significant positive linear correlation be-
sion during phacoemulsification. A built-in device tween endothelial cell loss and total ultrasound time,
for pressurized infusion has been adapted in various cumulative dissipated energy, and balanced salt solu-
phacoemulsification systems.3,6 tion volume. Another important cause of excessive
Q 2013 ASCRS and ESCRS 0886-3350/$ - see front matter 481
Published by Elsevier Inc. http://dx.doi.org/10.1016/j.jcrs.2013.01.004