Astigmatism Management in Modern Cataract Surgery

Round 1

Reviewer 1 Report

Astigmatism Management in Modern Cataract Surgery

The purpose of this review article is to investigate the importance of astigmatic correction and seek 10 to uncover the critical components of preoperative evaluation.

A few comments should be noted:

1.  The review article is well-written and successful in achieving a sensible review regarding astigmatism management. Nonetheless, I would appreciate a more in-depth consideration of keratometry measurement, including SimK, TCRP, and TK, and their relation to the IOL power calculation formulas available.

2.   Also, a description of the most effective toric IOL calculators online would provide a good guide to those who struggle with which online calculators to use, and what formulas are more suited for them.

Author Response

1. The review article is well-written and successful in achieving a sensible review regarding astigmatism management. Nonetheless, I would appreciate a more in-depth consideration of keratometry measurement, including SimK, TCRP, and TK, and their relation to the IOL power calculation formulas available.

Thank you for your comment. We have defined these indices and discussed their relation to each other and to IOL calculation formulas. We have also clarified their relation to the IOL power calculation formulas available in our description of these calculators.

Lines 192-205, Page 5-6, Section 2.6. Posterior Corneal Astigmatism

Corneal indices such as total corneal refractive power (TCRP), true net power (TNP), sim-ulated keratometry (sim-K), and total keratometry (TK) can be utilized as variables in toric IOL measurements. The anterior and posterior curvature along with the refractive indices of the cornea and aqueous humor are incorporated with Snell’s law to calculate the TCRP using Scheimpflug technology.[30] TNP is based on a Gaussian formula involving the same variables and Scheimpflug technology. Simulated keratometry is based on the anterior corneal curvature and refractive index to estimate the total corneal power, assuming the cornea as a single refractive surface (constant corneal thickness and anterior to posterior curvature ratio) also using Scheimpflug technology.[30,31] TK is derived with measurement of both the anterior and posterior corneal curvatures using swept-source optical coherence tomography.[31] Studies have exhibited higher accuracy and reliability with TCRP as compared to TNP or sim-K[30]. By contrast, Shajari et al.’s[31] work demonstrated no significant difference between total keratometry compared to K-sim, TNP, and TCRP.

2. Also, a description of the most effective toric IOL calculators online would provide a good guide to those who struggle with which online calculators to use, and what formulas are more suited for them.

Thank you for this insightful feedback. We have included a brief summary of six different available toric IOL calculators in addition to referencing comparison studies of toric calculators in the adjacent paragraphs.

Lines 89-98, Page 2-3, Section 2.1. Calculation methods/formulas

A variety of recently developed toric IOL calculators are now available. The Barrett toric formula utilizes the Barrett Universal 2 formula to compute the effective lens position (ELP) and the posterior corneal astigmatism directly or as a predicted value.[17] The Abu-lafia-Koch (AK) formula uses the Holladay 1 formula and the measured anterior corneal astigmatism to calculate the predicted refraction in each meridian.[17] The Naeser-Savini formula produces similar calculations using a combination of third-generation formulas. EVO 2.0 analyzes ELP and predicted posterior corneal astigmatism to calculate the total corneal power. The Holladay 2 formula includes correction for surgically induced astig-matism. And the Kane toric formula calculates ELP and uses theoretical optics and artifi-cial intelligence to estimate total corneal astigmatism.[17]

Reviewer 2 Report

The paper is well built and adequately describe the main methods to plan  pre-operative astigmatism correction and to avoid post-operative refractive errors, especially if due to astigmatism. On my opinion, only two minor considerations have to be considered by the Authors in their very good paper. The first is that, at a first glance, are difficult to understand and have to be better explained the last four lines of paragraph n. 1-4, where the higher contribution of P.C.A. in W.T.R.-A.C.A. is described. The other minor observation is due to the not ordered distribution of the references in the text, but this is probaby correlated to the paper plan, that, on the other side, is clear and well designed.

The quality of the English language is adequate

Author Response

1. The first is that, at a first glance, are difficult to understand and have to be better explained the last four lines of paragraph n. 1-4, where the higher contribution of P.C.A. in W.T.R.-A.C.A. is described.

We appreciate this request for clarification. We have modified this section accordingly by addition of the following:

Lines 65-67, Page 2, Section 1.4. Anterior and Posterior Corneal Astigmatism

Essentially, the posterior cornea is typically steeper along the vertical meridian in the grand majority of eyes, such that there is a greater impact to with-the-rule astigmatism.[12]

2. The other minor observation is due to the not ordered distribution of the references in the text, but this is probably correlated to the paper plan, that, on the other side, is clear and well designed.

Thank you for this comment and attention to detail. The references are listed in the order that they are cited in the text. However, a few articles are referenced multiple times throughout the entire body of the text, thereby infrequently disrupting the order of the references.

Reviewer 3 Report

1.       I think figure 1 should be WTR

2.       Did you discuss OCCI? https://pubmed.ncbi.nlm.nih.gov/10889422/

Author Response

1. I think figure 1 should be WTR

Thank you for bringing our attention this oversight. The correction has been made.

Line 135, Page 4, Section 2.4. Corneal Tomography

Figure 1. Corneal tomography printout indicating symmetric with-the-rule astigmatism.

2. Did you discuss OCCI? https://pubmed.ncbi.nlm.nih.gov/10889422/

We appreciate directing our attention toward this publication. Given its relevance to our section of correction of low astigmatism, we have added this technique and cited the reference you listed.

Line 230-233, Page 6, Section 3.1. Steepest Meridian Clear Corneal Incisions

Opposite clear corneal incisions (OCCIs) have been described as a treatment for astigmatism in patients undergoing cataract surgery requiring up to 2D of astigmatism.[35] A second identical, paired, and opposite incision to the cataract CCI is made to enhance the flattening effect on the cornea.

Reviewer 4 Report

Astigmatism is a very common refractive error both in young and old individuals. This review addressed a very important concern in clinics. Preoperative measurements, intaoperative corrections, and postoperative managments were all mentioned and discussed, providing very useful information and guidance  to the readers. I would like to recommend the author adding a table that summarize the mechamism, advantages and disadvantages of the instruments. Diagrms for different correction methods (e.g. relaxing incision) should also been illustrated for a better understanding.

In general, this is a well writen manuscript. However, some expression is quite difficult to be understood. 

Author Response

1. Preoperative measurements, intraoperative corrections, and postoperative management were all mentioned and discussed, providing very useful information and guidance to the readers. I would like to recommend the author adding a table that summarize the mechanism, advantages and disadvantages of the instruments.

Thank you for this suggestion. We have added the following table.

Line 162-169, Page 5, Section 2.5. Swept Source OCT

PCI – partial coherence intereferometry; OLCI – optical low coherence interferometry; OLCR – optical low coherence reflectometry; SS-OCT – swept source optical coherence tomography; IOLMaster 500 (Carl Zeiss Meditec, Dublin, California, USA); AL-Scan (Nidek Co. Ltd., Gamagori, Japan); OA-1000 (Tomey, Nagoya, Japan); Lenstar LS900 (Haag-Streit, Koniz, Switzerland); Aladdin (Topcon Europe, Visia Imaging, San Giovanni Valdarno, Arezzo, Italy); Pentacam HR (Oculus, Wetzlar, Germany); Galilei G4 (Ziemer Ophthalmic Systems AG, Port, Switzerland); IOLMaster 700 (Carl Zeiss Meditec, Dublin, California, USA); Argos (Movu, Santa Clara, CA); OA-2000 (Tomey, Nagoya, Japan); ANTERION (Heidelberg Engineering GmbH, Heidelberg, Germany)

Table 1. IOL biometers categorized by technology.

2. Diagrams for different correction methods (e.g. relaxing incision) should also been illustrated for a better understanding.

Thank you for your insightful suggestion. We hope that the intraoperative photograph in Figure 2 can convey the appearance and details of an arcuate incision (i.e. location, length, contour). We do agree that a single illustration inclusive of different types of clear corneal incisions (e.g. limbal relaxing incisions and arcuate keratotomies) may more accurately delineate the nuanced differences between each. However, at this time we are unable to produce a schematic illustration due to resource limitations. We have modified the caption for Figure 2.

Line 252-254, Page 7, Section 3.3. Femtosecond laser-assisted arcuate keratotomy

Figure 2. Intraoperative photograph demonstrating the opening of a femtosecond laser-assisted arcuate keratotomy. Note the location, length, and contour of this clear corneal arcuate incision nasally.