Refractive error after triple and non‐simultaneous procedures: is the application of a standard constant keratometry value in IOL power calculation advisable?

Abstract

ABSTRACT.Purpose: The purpose of this investigation was to determine whether or not the use of a standard constant keratometry value in cases of preoperative abnormal keratometry values in biometry for triple procedures is advisable. Methods: Cataract surgery and penetrating keratoplasty were performed in 82 eyes; 53 eyes underwent triple procedures and 29 eyes underwent non-simultaneous procedures. A standard constant keratometry value of 42.50 D was applied in 18 triple-procedure eyes because the preoperative measured keratometry values were outwith the normal range (41)47 D). The spherical equivalent and expected values were compared after a mean follow-up of 20.5 months. Results: Cases in the triple-procedure group that achieved spherical equivalent within ± 2.0 D of expected values included nine of 18 eyes (50%) in which a standard constant keratometry value of 42.50 D was applied, three of 17 eyes (18%) in which keratometry values outwith the normal range were applied (p ¼ 0.044), and eight of 18 eyes (45%) in which keratometry values within the normal range were applied (p ¼ 0.862). Cases in the non-simultaneous procedure group that achieved spherical equivalent within ± 2.0 D of expected values included 22 of 24 eyes (92%) in which keratometry values within the normal range were applied (p ¼ 0.0025), and five of five eyes (100%) in which a standard constant keratometry value was applied. Conclusions: The application of a standard constant keratometry value of 42.50 D for intraocular lens power calculation in triple procedures can be recommended if abnormal keratometry values were measured previously. If possible, non-simultaneous procedures should take priority.

The visual and refractive outcomes of combined and sequential penetrating keratoplasty, cataract extraction, and intraocular lens insertion

“…34,35,45,[48][49][50][51] However, improved surgical techniques and the use of intraocular viscoelastic agents may mean that secondary surgery can be performed with greater safety as suggested by a lower failure rate of 0-16% in more recent studies. 13,29,30,34,35,43,[49][50][51][52] Other authors have found no higher risk of graft failure from sequential surgery over triple procedure surgery, 13,28,35,46 with no significant difference in the percentage of endothelial cell loss 27,28 or increase in graft rejection episodes. 31 …”

“…Other comparative studies (Table 4) have demonstrated 48-96% of eyes to be within ± 2 D of emmetropia. [27][28][29][30][31] Geggel 34 reported 95% of eyes within ± 2 D of emmetropia; but 59% of eyes in this series received astigmatic correction at the time of secondary surgery, and all graft corneal sutures had been removed in 86% of eyes. Corneal curvature has been shown to change in an unpredictable manner after suture removal, 39 and, if possible, it is preferable to remove all graft sutures before IOL power calculation for sequential surgery.…”

“…The 5-year graft survival was 85% for both groups, which compares well with published triple procedure survival rates of 69-100% over variable follow-up periods. 5,[8][9][10][11]16,18,22,23,[29][30][31][32][33]42,46 The 2007 Australian Corneal Graft Registry 47 reported 1-and 5-year graft survivals of 89 and 78%, respectively, for triple procedure. Sequential surgery has been associated with increased graft endothelial cell count loss, and graft failure as high as 13-21%.…”

“…This compares favourably with other studies where 39-47% of eyes attained ±2 D of emmetropia. [27][28][29][30][31] The majority of studies evaluating triple surgery alone have shown approximately 50% of eyes achieve ±2 D of emmetropia, although the range of 26-95% within ± 2 D of emmetropia is rather wide. [3][4][5]9,10,13,[15][16][17][18][19][20][21][22]24,32,36 Supporters of sequential surgery highlight the potential for large ametropic errors with triple procedure surgery, arguing that IOL power can be calculated with greater accuracy when biometry is performed on a stable graft.…”

“…25,26 Small comparative studies have reported superior visual and refractive outcomes with sequential surgery owing to better IOL power calculation from stable post-PK keratometry readings. [26][27][28][29][30] Our aim was to compare triple procedure and sequential surgery, in terms of visual and refractive outcomes at 1 and 2 years after PK, using data collected routinely through the UK Transplant (UKT).…”