Getting it right: There is no miracle or magic for IOL Computations

No one formula must be exclusively used for IOL estimations to ensure precision, according to an ophthalmologist.
“There has actually been a big explosion in brand-new solutions and new technologies to make our lives much easier and much more intricate at the same time,” stated the doctor.  “We have to keep on top of this due to the fact that it is a rapidly expanding area and we should be ‘in the know’ of developments and innovations in this sphere.”


Doctor has actually observed that when ophthalmology residents are presently asked the question about which IOL calculator to use, the default solution is the Barrett IOL calculator.
“When I started residency, IOL selection depended upon conventional wisdom, without bothering too much about varied methods or too many numbers and measurements” he stated.

Room for improvement
Although the Barrett IOL calculator is accurate, there is still scope for change, according to the  doctor.
“What have we accomplished?” he asked. “No, we have not. Also in that research (with the Barrett IOL calculator), the Barrett (IOL calculator) while being the best-performing formula, was within 0.05 D of the intended target, 80% of the time.”
He noted that despite the Barrett, 20% of eyes are still falling 0.05 D beyond the envisioned  target.
“That is significant for many of our patients , especially if we are attempting to prevent refractive errors, which we are, in order to provide the best postoperative satisfaction to the patients” he stated.
The very same researchers took a look at the updated Olsen formula, which uses anterior chamber depth, keratometry, lens density, as well as axial length to predict effective lens setting.
“It was more exact than Barrett in regards to being within 0.05 D of the designated target, and therefore more suited or right, even if not as widely used” the doctor stated.
Among the new IOL power formulas is the Kane formula, which a group of investigators measured against 3 new or upgraded IOL power solutions consisting of the Hill-RBF (radial basis function calculator) Version 2.0 and the Holladay 2 with axial size adjustment compared with existing solutions such as Haigis, Barrett Universal 2, Hoffer Q, Olsen, SRK/T and also Holladay 1, noted the doctor.

A retrospective examination was done where the predicted refractive end result for each formula was calculated for each patient and also compared to the real refractive result to provide the prediction error, the end result to measure efficacy of the formulae.
The investigators organized eyes according to the axial size or the distance from the anterior corneal surface to the retinal pigment epithelium: short, medium, or long.

The Kane formula produced the lowest absolute error in the medium axial length range, as well as over the entire axial length range, this formula produced the lowest mean absolute prediction error (P <.001) of all the formulae.

It was concluded that using 3 procedures including axial size, keratometry readings, and also anterior chamber depth, the Kane formula was one of the most exact and accurate predictors of real postoperative refraction than various other formulae that were studied.
“The next time a person asks a resident about biometry, possibly the solution must be ‘Kane’,” the doctor concluded.

Still another research that consisted of 10,930 eyes of 10,930 patients concluded that the Kane formula had the lowest mean as well as median absolute prediction error for short, medium, and long axial size subgroups and also for every IOL.
Scientists additionally observed that upgraded versions of the Holladay 2 and also Hill 2.0 solutions have actually resulted in improved accuracy.”

 The Kane (formula) was the best-performing formula for short eyes, average eyes, and also long eyes,” the doctor mentioned. “It was the best of the lot (of solutions)”.


Study various other solutions.
Although these 2 examinations supported using the Kane formula, still various other solutions need to be studied for their capacity to supply very accurate IOL calculations, according to the ophthalmologist.
“We require to take a look at what is on the horizon,” the ophthalmologist stated. “We need to keep pushing and also considering other ways (formulas). It is not as basic as making use of Kane for all or Barrett for all”.
A team of ophthalmologists have actually conducted their own retrospective study and also have discovered that intraoperative aberrometry had the greatest portion of eyes within 0.05 D of the designated target.
“A constraint of the research is that we did not include the Kane (formula),” they claimed.

Among the newer IOL calculators is the Hill-RBF calculator, established by another ophthalmologist and cataract doctor. That calculator, a type of artificial neural network, can be accessed on the internet.
“This (calculator) has a boundary feature, as well as it informs you when the eye you are inputting data from is outside of the data set that this formula makes use of,” the doctor noted. “I do not think this is a downside of the Hill-RBF calculator. I think this is an attribute because it helps me to recognize if this patient will be in the 20% of patients that are falling 0.05 D beyond the designated target”.

Planning surgical procedures.
The eye doctor clarified that surgeons can prepare their surgeries suitably.


“You may intend to advise these patients regarding specialty IOLs,” he stated. “You can show the patient preoperatively that the biometry is not normal in which case we might have to do more interventions to accomplish the patient’s intended target”.


Patient expectations are also pushing clinicians to take a look at optimum levels to get to the most effective IOLs, noted the doctor. “It is good to be able to compare across new-generation formulas,” he stated.

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