Clinically relevant biometry

Abstract

Purpose of review Obtaining precise post-operative target refraction is of utmost importance in today’s modern cataract and refractive surgery. Given the growing number of patients undergoing premium intraocular lens implantations, patient expectation continues to rise. In order to meet heightened patient expectations, it is crucial to pay utmost attention to patient selection, accurate keratometry and biometry readings, as well as to the application of correct intraocular lens power formula with optimized lens constants. This article reviews recent advances in the field of clinical biometry and intraocular lens power calculations. Recent findings Recently developed low-coherence reflectometry optical biometry is comparable to older ultrasonic biometric and keratometric techniques. In addition, the new IOL Master software upgrade has improved reproducibility and enhanced signal acquisition. Further, the modern lens power formulas currently determine the effective lens position and the shape of the intraocular lens power prediction curve more accurately. Summary In order to reach target refraction, precise biometric measurements are imperative. Understanding the strengths and limitations of the currently available biometry devices, allows prevention of high variability and inaccuracy, ultimately determining the refractive outcomes.

Kataraktos chirurginio gydymo efektyvumo įvertinimas: pooperacinis regos aštrumas, refrakcija ir astigmatizmas

“…Akies ašies ilgiui apskaičiuoti gali būti naudojama ir optinė biometrija, pagrįsta daline koherentine lazerine interferometrija. Skaičiavimai atliekami bekontakčiu prietaisu, pacientas fiksuoja žvilgsnį nurodyta kryptimi, automatiškai ties regos ašimi atliekamas matavimas [5].…”

“…Akies ašies ilgiui apskaičiuoti gali būti naudojama ir optinė biometrija, pagrįsta daline koherentine lazerine interferometrija. Skaičiavimai atliekami bekontakčiu prietaisu, pacientas fiksuoja žvilgsnį nurodyta kryptimi, automatiškai ties regos ašimi atliekamas matavimas [5].Ragenos laužiamoji galia nustatoma atliekant keratometriją. Išmatuojamas ragenos gaubtumo spindulys (mm), kuris perskaičiuojamas į ragenos laužiamąją galią dioptrijomis (D).…”

Optimising biometry for best outcomes in cataract surgery

“…Non-contact optical biometry has become the gold-standard because of its ease of use, accuracy, and reproducibility. 9 The main disadvantage of the optical methods is their inability to obtain axial length measurements in approximately 10% of eyes, typically those with dense posterior subcapsular cataracts. 7,14 For these eyes ultrasonic axial length measurement is required, and in the UK contact ultrasound is the method of choice with immersion methods rarely used.…”

“…8 There is presently no single formula that is suitable for all eyes. 9 There are many studies comparing the performance of various formulas in different patient groups, but often the number of eyes analysed is small. The most authoritative comparison to date is that of Aristodemou et al, which evaluated the performance of the Hoffer Q, Holladay 1, and SRK/T formulas in 8108 eyes.…”

“…9 Gale et al found that with appropriate formula selection, optical axial length measurement, and optimisation of IOL constants 87% of patients achieved an outcome within ± 1 D of target. 10 The Royal College of Ophthalmologists, in its most recent Cataract Surgery Guidelines, 11 has adopted a standard of 85% within ± 1 D of target and 55% within ± 0.5 D of target.…”