![]() ![]() We have found that the BESSt 2, a second iteration of the formula, results in greater prediction accuracy and less risk of refractive surprise after hyperopic treatments (unpublished data). BESSt starts from the true net corneal power as calculated with the Gaussian optics formula, but then it makes crucial adjustments based on the actual measured postoperative corneal radii and the altered anterior/posterior radius relationship. This can therefore yield inaccurate results, especially in postrefractive surgery eyes where the relationship between the anterior and posterior corneal radii is no longer constant. It is not possible to use values obtained from the Gaussian optics formula in most current IOL power formulas because they are calibrated using a standard keratometric index of 1.3375, which does not take true posterior corneal curvature into account. BESSt AND BESSt 2īased on direct anterior and posterior corneal curvature and corneal thickness measurements using the Pentacam and a modified Gaussian optics formula, the BESSt algorithm estimates corneal power in eyes after laser refractive surgery for myopia or hyperopia. These formulas can be used for eyes that have previously undergone myopic or hyperopic excimer laser treatments, even if there is a lack of prerefractive surgery information. 1 The second approach, the more recently developed Borasio Myopic Regression and Borasio Hyperopic Regression (BMR-BHR) formula, requires direct measurements from the IOLMaster (Carl Zeiss Meditec). I use two approaches to calculate IOL power following laser refractive surgery, the first of which, the Borasio Edmondo Smith and Stevens formulas (BESSt and BESSt 2), is based on direct anterior and posterior corneal surface measurements and requires the Pentacam (Oculus Optikgeräte GmbH). In these cases, instead of using a pseudophakic IOL power calculation that incorporates preoperative data, which can result in refractive surprises, I prefer to use direct corneal measurements. Using standard keratometry and raw data taken from corneal topography to calculate refractive corneal power in postrefractive surgery eyes can result in an inaccurate representation of the true corneal power. These formulas are useful for eyes that have previously undergone myopic or hyperopic laser treatments. ![]() Intraoperative Aberrometry for Postrefractive Surgery IOL Calculationsĥ Questions With Elisabeth Patsoura, MD, MRCOphth The Creator’s Forum: IOL Power Calculations for Postrefractive Surgery EyesĪchieving Better Outcomes Using Free Online Post-LASIK IOL CalculatorsĪppropriate IOL Calculations in Postrefractive Surgery Patients Pearls for Improving Standard Cataract Outcomes and Workflowīasic Error Sources in IOL Calculation AfterRefractiveSurgery Intrastromal Astigmatic Keratotomy Using a Femtosecond Laser ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |