Article

Options continue for refining IOL power calculations

Depending on what tools and historic data are available, there are a number of methods to choose from in order to compensate for corneal power errors in these cases.

Speaking at the refractive surgery subspecialty day meeting sponsored by the International Society of Refractive Surgery of the American Academy of Ophthalmology, Dr. Hoffer provided an update on techniques for optimizing refractive outcomes after cataract surgery in these potentially troublesome eyes.

"Be aware, however, that none of these approaches has been proven in a large prospective series," said Dr. Hoffer, clinical professor of ophthalmology, Jules Stein Eye Institute, UCLA School of Medicine, Los Angeles.

"If the preoperative K is unknown, it is better to use a value of 43.5 D as the standard," said Dr. Hoffer.

Clinical history method. The clinical history method is one of the oldest techniques that has been used to compensate for errors in keratometry measurement in post-LASIK eyes. It was first described by Jack Holladay, MD, and uses the pre-LASIK K reading (Kpre) and refractive error (Rpre) along with the post-LASIK refractive error (Rpo) to estimate K as follows: K = Kpre + (Rpre – Rpo). As an example, for a patient with –9.0 D myopia and an Rpo of +1.0 D and Kpre of 43 D, K = 43 + (–9 – 1) = 33 D.

The Masket variation first uses "as is" biometry to calculate the IOL power needed for an emmetropic outcome (PEm). Dr. Masket recommends using the SRK/T formula to calculate PEm in long eyes and the Hoffer Q formula in short eyes. Then, implant power (P) is derived by an adjustment of the PEm using the change in refraction (Rx) and constants. According to this formula, P = PEm – 0.323(Rx) + 0.138.

Newsletter

Don’t miss out—get Ophthalmology Times updates on the latest clinical advancements and expert interviews, straight to your inbox.

Related Videos
(Image credit: Ophthalmology Times) ASCRS 2025: Parag Majmudar, MD, on bridging the gap between residency and real-world practice
Brett Bielory, MD, discusses his poster at the ASCRS annual meeting, which focuses on an under-diagnosed corneal pathology: neurotrophic keratitis.
ASCRS 2025: Eva Kim, MD, discusses implantable collamer lenses and high myopia.
Abby Markward, MBA, and Hattie Hayes, editor of Ophthalmology Times Europe, discuss the ASCRS and ASOA meetings
Abby Markward discusses the ASCRS Foundation and the ASCRS Annual Meeting
(Image credit: Ophthalmology Times) Inside ASCRS 2025: Francis S. Mah, MD, takes the helm with a vision for research, education, and advocacy
(Image credit: Ophthalmology Times) NeuroOp Guru: Cranial nerve six palsy with chemosis is a critical clue to cavernous carotid fistula
© 2025 MJH Life Sciences

All rights reserved.