Abstract
Purpose :
The A constant of the CZ70BD lens was calculated for an in-the-bag location; however, this lens is only placed when there is no capsular support. The standard technique involves 4-point fixation at 1.5mm and 3mm posterior to the limbus with an average lens distance of 2.25mm posterior to the limbus. The resultant lens location is 0.75mm anterior to where an intraocular lens would be placed in-the-bag. This poses lens calculation difficulties with the IOL Master because the lens is sutured to a location other than where the A constant was developed. The purpose of the study is to determine average refractive error of a sutured CZ70BD lens to discover methods of improving refractive outcome.
Methods :
A retrospective review of 54 cases involving CZ70BD lenses was completed. All lenses were sutured by a single surgeon using identical technique, which included 4-point fixation at 1.5mm and 3mm posterior to the limbus at the 3 and 9 o’clock position. Analysis involved calculating average and standard deviation of the difference between the IOL Master generated pre-operative refractive goal and the post-operative refractive error calculated as a spherical equivalent. All refractions were completed in the primary ophthalmologist’s or optometrist’s office.
Results :
The mean difference between the pre-operative goal and post-operative outcome was -0.420±1.26D and with a cutoff of differences ≥2.5D, it was -0.317±0.87D. Comparison of goal versus post-operative refraction revealed hyperopic (27.7%), myopic (59.2%), and plano (11.1%) results. Conditions that may have increased standard deviation include retinal disease, traumatic changes, and subjective refraction. Results were reliant on subjective refraction at the primary ophthalmologist’s or optometrist’s office. Analysis excluded subjects with severe corneal disease due to limited assessment of proper refractive error.
Conclusions :
The current standard practice of 4-point fixation of a CZ70BD lens at 1.5mm and 3mm is satisfactory, yet it results in a more myopic refraction than anticipated. This is likely because the A constant was developed for in-the-bag placement, but the lens is sutured in a more anterior location. Three approaches to the discrepancy include reducing the suggested lens power by 0.4D, suturing the lens 0.12mm posterior to its current location, and operating with anticipation of location-induced myopia.
This is a 2020 ARVO Annual Meeting abstract.