Refractive Accuracy of Toric Intraocular Lens Implantation Using Digital Marking Compared to Conventional Marking
Conditions: Cataract, Astigmatism
Sponsor: Colvard Kandavel Eye Center

 
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APPROVED BY SALUS IRB: 07 MAY 2024 
 
 
 
 
TITLE: 
Comparative Study of the DMM and Conventional Toric Marker 
 
PROTOCOL NO: 
IIT# 92162521 
 
AMENDMENT NO: 
Version 1.0 
 
IRB:  
Salus IRB 
  
 
 
 
2111 West Braker Lane, Suite 400 
Austin, TX 78758 
 
SPONSOR:  
Ganesha Ramana ‘Rom’ Kandavel, MD 
 
INVESTIGATOR: 
Ganesha Ramana ‘Rom’ Kandavel MD 
 
5363 Balboa Blvd Suite 540 
 
Encino, CA 91316 
 
United States 
 
STUDY-RELATED 
818-906-2929 (During business hours) 
PHONE NUMBER: 
818-446-2312 (24-Hour line) 
 
 
 
 
 
 
 
 
 
 
 
 

 
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1. Executive Summary 
 
NEED 
There is currently a paucity of data comparing ARGOS combined with the Digital Marker Microscope and 
other Conventional Marking Modalities for Toric IOL alignment during cataract surgery. 
 
STUDY OBJECTIVE 
To evaluate the postoperative refractive accuracy of the common toric Intraoperative marking method of 
Toric CAM and Mendez marking when compared to ARGOS combined with the Digital Marker Microscope 
(DMM)/Vision Suite. 
 
STUDY HYPOTHESIS 
The DMM linked to Argos preoperative measurements with limbal registration determines the angle for 
toric IOL alignment intraoperatively more accurately than the manual Mendez marker. 
 
SUPPORTS CLINICAL MESSAGE 
The use of ARGOS with intraoperative image guidance improves the toric alignment error significantly and 
allows for more % of eyes within 0.5D residual CYL (20% more eyes) as compared to manual marking. 
 
STUDY DESIGN 
Sample size  
 
35 eyes 
 
Endpoints 
 
 
Primary: 
Difference in intraoperative axis marks with Mendez marker, in 
 
 
 
 
 
 
degrees and direction, when compared to the DMM as viewed 
 
 
 
 
 
 
in the intraoperative heads-up display 
Secondary:  % of eyes less than 0.25, 0.5, 0.75, 1.00 and 1.25 D of residual 
 
 
 
refractive cylinder (CYL) in each group at 1 month  
 
 
 
 
postoperatively 
 
Design: 
 
 
Single-site, head to head, prospective, interventional (all eyes will be 
planned/implanted using ARGOS with image guidance axis; and the manual 
 
marker results will be back calculated utilizing IOL position and post-operative 
 
refraction) 
 
DURATION/FOLLOW-UP: Preoperative to 1 month postoperative 
 
 
This study will be registered with clinicaltrials.gov. The study will be conducted in compliance with the 
protocol, GCP, and applicable regulatory requirements.  
 

 
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2. Study Background 
 
Toric IOLs offer patients with corneal astigmatism, increased spectacle independence after 
cataract surgery. Toric marking aims at improving the accuracy of incision location and IOL 
alignment. Conventional markers rely on a reference mark tied to gravitational alignment 
and the accuracy in manual marking methods is affected by head position, errors on 
marking and smearing of ink. Digital marking methods aim to reduce intraoperative IOL 
misalignment using images captured in the sitting position which are used as overlay for 
IOL alignment intraoperatively¹. The DMM linked to ARGOS preoperative measurements 
with limbal registration determines the exact angle for toric IOL alignment intraoperatively. 
 
The purpose of this study is to compare the outcome of toric IOL implantation guided by 
manual or digital marking techniques. The intrinsic difference in the toric axis alignment 
may lead to a significant difference in the marked alignment axis intraoperatively resulting 
in superior refractive outcomes and less residual astigmatism using intraoperative 
alignment from the ARGOS Vision planner and DMM. 
 
3. Study Design 
• A single site, interventional study comparing the ARGOS/ DMM axis to the Mendez 
toric marker paired with the toriCAM smart phone app.  
• There will be 35 eyes total that meet the inclusion criteria. Patient’s refraction will be 
evaluated 4 weeks after cataract surgery with a monofocal toric IOL (Clareon Toric). 
• Intraoperative difference in toric marks will be recorded in degrees and direction of 
marking difference (clockwise and counterclockwise). 
• Post operative refraction will be obtained at 4 weeks after surgery using standard 
Snellen acuity chart and phoropter. IOL position will be verified with slit lamp 
photography aligned with preoperative Argos toric imaging to ensure that IOL position 
is NOT a source of refractive error.  
• We will perform back calculation of theoretical refraction, as if the IOL was positioned 
at Mendez marking axis rather than the Argos axis. This will be calculated using the 
IOL position and post operative refraction with Astigmatismfix.com calculator or 
equivalent calculator 
 

 
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4. Study Inclusion and Exclusion Criteria 
4.1 Inclusion Criteria 
Subjects are eligible for the study if they meet the following criteria: 
 
• Subjects willing and able to participate in this study. 
• Subjects that have signed a consent to participate in the study. 
• Subjects that are 50-80 years of age that have had uncomplicated femto-second 
assisted cataract surgery 
• Subjects will have been implanted with the toric Alcon Clareon Toric monofocal IOL 
• Subjects with IOLs implanted based on digital marking performed using ARGOS DMM 
• Subjects will have BCDVA of LogMar 0.20 (20/32) or better in both eyes 
• Subjects able to perform a post-op refraction. 
 
4.2 Exclusion Criteria 
 
If any of the following exclusion criteria are applicable to the subject, the subject should not 
be included in the study: 
 
• History of amblyopia, macular disease, glaucoma, corneal disease, prior corneal 
surgery, or diabetes 
• IOL final position greater than 2 degrees from intended axis. 
• Ocular comorbidity that might hamper post operative visual acuity 
• Previous ocular or refractive surgery 
• Expected post-op VA worse than 20/25 (Snellen) 
• Irregular corneal astigmatism and keratoconus 
• Difficulties comprehending written or spoken English language 
• Patients that are unable to fixate due to physical or intellectual disability (e.g. Down’s 
Syndrome, Parkinson’s Disease) 
• Severe/uncontrolled Ocular surface disease/Dry Eye Disease 
• Intraoperative complications during procedure 
 
 

 
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5. Study Procedures 
5.1 Preoperative 
At the preoperative exam, subjects will undergo all routine, usual standard-of-care 
procedures, including a medical history, demographics, ARGOS biometry, and a slit-lamp 
and dilated fundus examination. Subjects will then be consented for the study, and a review 
of inclusion and exclusion criteria will be done prior to the surgery. 
5.2 Operative (Day of Surgery) 
All subjects will undergo femto-second assisted cataract surgery with implantation of the 
Clareon monofocal toric IOL. 
The toriCAM smartphone app will be used to mark the horizontal axis as a reference 
preoperatively in a sitting position. The target axis of the IOL, as calculated by the Argos, will 
be marked intraoperatively with a Mendez marker based on the horizontal reference marker 
from the Toric Cam. 
After phacoemulsification, the Digital Marker Microscope (DMM) will be used to determine 
the target axis by using an image overlay  
 
The difference in the final marked IOL axis and the DMM axis will be measured using the 
DMM degree overlay intraoperatively. The difference in degrees and the direction will be 
recorded. 
5.3 Postoperative Visits 
Subjects will undergo all routine, usual standard-of-care postoperative procedures and follow 
up appointments.  
In addition, 4 weeks following cataract surgery, the final position of the IOL will be confirmed 
using a slit lamp photograph compared to the ORIGINAL Argos reference image. The 
surgeon will confirm that the IOL is within 2 degrees of the final intended axis as calculated 
by the Alcon Vision Planner. 
Then the postoperative subjective refraction shall be measured by Snellen and Phoropter 
method and the theoretical refraction shall be back calculated using the double vector 
method to arrive with the refraction that would have been obtained by the Mendez marking 

 
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method. This will be calculated using the IOL position and post operative refraction with 
Astigmatismfix.com calculator or equivalent calculation. 
6. Statistical Analysis 
A summary of the data will be prepared for all measurements. For variables measured on a 
continuous scale, these summaries will include the sample size, as well as the mean, 
standard deviation, median, minimum, and maximum. For variables measured on a 
categorical scale, summaries will provide the number and percentage of eyes in each 
category. These summaries will be provided for all eyes completing the study.  
The statistical analyses will be performed using R, version 4.2.2 or higher. Any statistical 
tests of hypotheses will employ a level of significance of alpha=0.05.  
The primary endpoint will be compared using the paired t-Test. Secondary endpoints will be 
compared using McNemar’s test. Analysis will follow a step down approach:  
• Difference in intraoperative axis marks with Mendez marker, in degrees and direction, 
when compared to the DMM viewed in the intraoperative HUD  
•  % of eyes less than 0.5D CYL in each group 
•  % of eyes less than 0.25D CYL in each group  
•  % of eyes less than 0.75D CYL in each group  
•  % of eyes less than 1.0D CYL in each group  
•  % of eyes less than 1.25D CYL in each group 
 
 

 
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7. Sample Size Justification 
Based on the primary endpoint, the study would require a sample size of 21 pairs (to achieve 
a power of 80% and a level of significance of 5% (two sided), for detecting a mean of the 
differences of 4.4 between pairs, assuming the standard deviation of the differences to be 
6.5.1  
However, in order to achieve a sample size that allows for statistical analysis of the 
secondary endpoints, we estimate the sample size required for detecting a difference of 0.20 
between the percentage of with postoperative residual astigmatism 0.5 D or less (85% 
compared to 65%), power of 85%, correlation between paired observations 0.80, and a two-
sided significance of 5% is 30.2  
To account for dropout, the sample size will be increased to 35 eyes.  
 
 
References  
1. Lipsky L, et al. Comparison of toric intraocular lens alignment error with different toric 
markers. J Cataract Refract Surg. 2019; 45:1597–1601.  
2. Webers VSC, Bauer NJC, Visser N, Berendschot T, van den Biggelaar F, Nuijts R. 
Image-guided system versus manual marking for toric intraocular lens alignment in 
cataract surgery. J Cataract Refract Surg. 2017; 43: 781-788.