Behavior of Generated Gas during Femtosecond Laser Lens Irradiation in Porcine Cadaver Eyes
, Kotaro Oki 2, Akira Watanabe 1, Makiko Ohkido 3, Hisaharu Iwaki 4, Takuya Shiba 5 and Tadashi Nakano 1Round 1
Reviewer 1 Report
- Materials and Methods
What was the rationale for using Porcine eyes rather than using human cadaver eyes?
That is more appropriate for translating into clinical settings of this study results….
Line 79: How long after was the measurements taken post irradiation? Indicate the duration and time-points.
Line 106: Was lens capsule removed or intact for lens equatorial perimeter measurement?
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors present a study on the behavior of gas generated during irradiation of the eye lens by femtosecond pulsed laser, its relation to the total delivered energy and its influence on the lens capsule. Although it is a limited study, as properly acknowledged by the authors on the Discussion section, the study is interesting and may deserve publication. However, there are several aspects that must be improved on the manuscript.
The authors should state clearly what is the originality of their study. This must be supported by a more detailed presentation of the current state of the art regarding gas formation on the lens during femtosecond laser irradiation. This is essential to evaluate the innovation of the study presented on the paper. The Introduction section only cites 4 references, some of them do not concern gas formation on the lens and the paper fails to provide an adequate overview of the current knowledge on the subject of the study. And without this, the reader cannot assess adequately the novelty of the paper.
It is stated that “since the thickness of the porcine lens made it impossible to detect the posterior capsule when using the installed OCT, the tentative PCP was manually set so that the lens thickness was 6.5 mm”. Is there an estimate of the error introduced by this approximation? Does it influence the results? Could it be possible to measure the PCP by ultrasound pachymetry? These questions should be addressed on the Discussion section.
The authors must be more rigorous on the description of the statistical methods used to analyze the data. On line 79, the authors state that “ACD correlations between the pre and post laser irradiation were statistically analyzed by a Wilcoxon signed-rank”. On line 112, it is said that “Correlation of the equatorial perimeter between the control and the laser irradiated lenses were statistically analyzed by a Mann-Whitney U test”. Both the Wilcoxon and the Mann-Whitney test are not correlation tests. Instead, they test whether two samples are likely to derive from the same population. In simple terms they are equivalence tests for comparison between groups. Equivalence is different from correlation. The tests are well selected and adequate, but the manuscript must be corrected.
It is difficult to understand how many and what eyes were used on the different tests: 26 eyes of which 16 were irradiated (Table 1); 5 eyes were measured by OCT; Endoscopic imaging was performed on 6 eyes; Of these (?) 5 eyes did not rupture; equatorial perimeter of the crystalline lens was measured in 10 eyes. It is difficult to follow. The authors may consider adding a table indicating which eyes were submitted to the different procedures.
On line 60, it is necessary to identify what was the ethics committee that was consulted.
How was measured the energy delivered to the lens? I suppose that the authors used the energy values given by the CATALYS system. However, this should be clearly stated.
The study did not find a correlation between the laser irradiation energy and the ACD change ratio. The value p obtained (p = 0.054) and the graphical representation of the data (Figure 2 b) suggest that this was due to a lack of statistical power caused by the small size of the sample (5 eyes). It would be interesting to discuss this result. Considering what is known on the mechanisms leading to gas formation on the lens by laser irradiation, was it expected to find a correlation? Are there any previous studies concerning the relation between total irradiation energy and the variation of the anterior chamber depth?
In more general terms, the Discussion should be improved. The obtained results should be compared to what is expected when considering the mechanisms leading to gas formation and to published studies on this subject (in case there are such studies)
I recommend an English review by an expert. There are some errors (for example on line 45 it should be “has yet” instead of “have yet”) and weak English usage (line 35: “laser can be irradiated with a variety of designs” – it is the eye, not the laser, that is irradiated; abstract: … which may cause complications caused…) that degrade the readability of the manuscript.
Minor issues
There is a typo on the manuscript title: “Cadver” instead of “Cadaver”.
On the Abstract, Results section, the same idea is repeated: line 18 – “Femtosecond laser generated gas in the porcine lens was dependent on the laser irradiation energy”; line 21 – “The amount of gas produced was dependent on the amount of laser irradiation energy”.
On line 153, “error bar” should be replaced by “scale bar”.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
