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Optimizing IOL selection: Focus on IOL calculations in “difficult” eyes

  • Downloads including slides are available for this activity in the Toolkit
Learning Objectives

After watching this activity, participants should be better able to:

  • Describe the preoperative assessment of ocular health in patients scheduled for cataract surgery
  • Discuss biometry and IOL calculations to achieve optimum postoperative refractive outcomes in cataract patients
  • Recognize how previous refractive surgeries and corneal pathologies in cataract patients impact biometry, IOL calculations and lens selection

In this activity, experts in ophthalmology, Prof. Sumit Garg and Dr Karolinne Rocha, respond to questions from the ophthalmology community on intraocular lens (IOL) selection in cataract patients, focusing on the preoperative assessment of ocular health, optimizing IOL calculations and the impact of previous surgeries on lens selection.

This activity is funded by an independent medical education grant from Alcon Vision, LLC and Johnson & Johnson Surgical Vision, Inc., and is jointly provided by USF Health and touchIME. read more

Target Audience

Ophthalmologists, including cataract and refractive surgeons.


USF Health adheres to the Standards for Integrity and Independence in Accredited Continuing Education. All individuals in a position to influence content have disclosed to USF Health any financial relationship with an ineligible organization. USF Health has reviewed and mitigated all relevant financial relationships related to the content of the activity. The relevant relationships are listed below. All individuals not listed have no relevant financial relationships.


Prof. Sumit Garg discloses: Consultancy fees from Aldeyra Therapeutics, Allergan, Avellino, Centricity Vision, CorneaGen, Dompé Farmaceutici, ForSight Robotics, Glaukos, Johnson & Johnson Vision, Kala Pharmaceuticals, LensGen, Novartis (relationship terminated), New World Medical, Oyster Point Pharma, Sight Sciences, Samara Pharmaceuticals, SpyGlass Pharma, Tarsus Pharmaceuticals, Trefoil Therapeutics, Verana Health, Visus Therapeutics, Zeiss Pharmaceuticals.

Dr Karolinne Rocha discloses: Consultancy fees from Bausch & Lomb, Hoya Surgical Optics (cataract), Johnson & Johnson Vision, Rayner, Zeiss Pharmaceuticals.

Content Reviewer

John Steven Jarstad, M.D., FAAO, FRSM-UK has no financial interests/relationships or affiliations in relation to this activity.

Touch Medical Contributors

Samantha Waite has no financial interests/relationships or affiliations in relation to this activity.

Anne Nunn discloses: Employee or independent contractor relationship from Envision Pharma Group (relationship terminated).

USF Health Office of Continuing Professional Development and touchIME staff have no financial interests/relationships or affiliations in relation to this activity.

Requirements for Successful Completion

In order to receive credit for this activity, participants must review the content and complete the post-test and evaluation form. Statements of credit are awarded upon successful completion of the post-test and evaluation form.

If you have questions regarding credit please contact



This activity has been planned and implemented in accordance with the accreditation requirements and policies of the Accreditation Council for Continuing Medical Education (ACCME) through a joint providership of USF Health and touchIME. USF Health is accredited by the ACCME to provide continuing medical education for physicians.

USF Health designates this enduring material for a maximum of 0.75 AMA PRA Category 1 CreditTM.  Physicians should claim only the credit commensurate with the extent of their participation in the activity.

The European Union of Medical Specialists (UEMS) – European Accreditation Council for Continuing Medical Education (EACCME) has an agreement of mutual recognition of continuing medical education (CME) credit with the American Medical Association (AMA). European physicians interested in converting AMA PRA Category 1 CreditTM into European CME credit (ECMEC) should contact the UEMS (

Advanced Practice Providers

Physician Assistants may claim a maximum of 0.75 Category 1 credits for completing this activity. NCCPA accepts AMA PRA Category 1 CreditTM from organizations accredited by ACCME or a recognized state medical society.

The AANPCP accepts certificates of participation for educational activities approved for AMA PRA Category 1 CreditTM by ACCME-accredited providers. APRNs who participate will receive a certificate of completion commensurate with the extent of their participation.

Date of original release: 11 September 2023. Date credits expire: 11 September 2024.

If you have any questions regarding credit please contact

This activity is CE/CME accredited

To obtain the CE/CME credit(s) from this activity, please complete this post-activity test.

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  • Downloads including slides are available for this activity in the Toolkit

Topics covered in this activity

Cataract Surgery / Anterior Segment / Refractive Surgery
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Optimizing IOL selection: Focus on IOL calculations in “difficult” eyes
0.75 CE/CME credit

Question 1/5
What is best practice when selecting the right IOL for cataract surgery?

IOL, intraocular lens.

With continuing advances in technologies and techniques in cataract surgery, patient expectations are high. While full preoperative evaluation including a full medical history, examination and testing is essential, it is also important to listen carefully to patients and address any concerns they may have prior to surgery. Results from this evaluation should be used to effectively counsel patients and achieve good results.


Israelsen P, Garg S. Ophthalmology Management. 2020;24:38–41.

Question 2/5
During a preoperative assessment for cataract surgery, your 64-year-old patient tells you they want spectacle independence following surgery. Upon examination, astigmatism measurements are inconsistent, suggesting presence of DED. How do you advise this patient during their preoperative consultation?

DED, dry eye disease.

Prevalence of DED in patients needing cataract surgery is 3.5–33.7%.1 In these patients, cataract surgery requires careful pre, intra and postoperative planning, but is associated with good visual outcomes, with no significant complications when managed effectively.2,3 Multifocal IOLs will give the best chance of spectacle independence, but increase the risk of the patient experiencing visual disturbances such as glare and halos compared with monovision IOLs.4


DED, dry eye disease; IOL, intraocular lens.


  1. Trattler WB. Clin Ophthalmol. 2017;11:1423–30.
  2. Naderi K, et al. Eur J Ophthalmol. 2020;30:840–55.
  3. Donthineni PR, et al. Front Med (Lausanne). 2020;7:575834.
  4. De Silva SR, et al. Cochrane Database Syst Rev. 2016;12:CD003169.
Question 3/5
You would like to use the Olsen formula for your patient with myopia. What preoperative measurements do you need to obtain?

The Olsen formula is based on studying axial and paraxial ray tracings of light through the eye, including the specific optics of a particular IOL. It has a C constant, which relates the centre of the IOL to the preoperative anterior chamber depth and lens thickness. The C constant does not depend upon the axial length and corneal curvature.


IOL, intraocular lens.


Xia T, et al. Asia Pac J Ophthalmol (Phila). 2020;9:186–93.

Question 4/5
A Wang-Koch adjustment can be applied to some third- and fourth-generation IOL formulae to optimize the calculation of AL in certain eyes. When would you consider using the Wang-Koch adjustment?

AL, axial length; IOL, intraocular lens.

Outliers in AL measurement may result in refractive surprises unless an adjustment is made to the IOL formula. Long eyes have been a challenge and often end up hyperopic with standard calculations. This may be due to an overestimation of the length of the posterior segment, thus selecting an IOL of insufficient power. Long eyes are likely to have a longer posterior segment that has a different index of refraction compared with the anterior chamber and cornea.1 The Wang-Koch formula for optimizing AL fully compensates for this problem and has shown improved outcomes in long eyes with AL >25.0 mm.1,2


AL, axial length; IOL, intraocular lens.


  1. Khandelwal SS, Koch DD. Ophthalmology Management. 2016;20:28–30.
  2. Wang L, et al. J Cataract Refract Surg. 2011;37:2018–27.
Question 5/5
Your 78-year-old patient, who underwent hyperopic LASIK surgery 18 years ago, now requires cataract surgery and IOL implantation. What IOL would you consider for this patient?

EDOF, extended depth of focus; IOL, intraocular lens; LASIK, laser assisted in situ keratomileusis.

Prior hyperopic LASIK tends to induce negative spherical aberration in the cornea; however, it is more common for the anterior corneal aberration value to be reduced to a near-zero value, making an aberration-neutral IOL more appropriate.1,2 A traditional monofocal IOL with positive spherical aberration helps to offset the negative spherical aberration that may occur after LASIK correction for large amounts of hyperopia.1


IOL, intraocular lens; LASIK, laser assisted in situ keratomileusis.


  1. Stonecipher KG, et al. Previous Hyperopic LASIK. Cataract & Refractive Surgery Today. 2019. Available at: (accessed 15 August 2023).
  2. Wang L, Koch DD. Ophthalmology. 2021;128:e121-31.
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