Risk Factors For Extrusion After Manual Intracorneal Ring Implantation For Keratoconus In Guatemala

To assess extrusion associated factors after manual intracorneal ring segment (ICRS) implantation for keratoconus. To propose a predictive index for extrusion, based on clinical characteristics of the patients studied

National Ophthalmology Unit-Roosevelt Hospital, Guatemala City, Central America

Retrospective chart review of patients who underwent manual ICRS implantation from Jan 2018 to July 2021 with at least 6 months of follow-up. Charts reviewed for demographic data, ICRS characteristics (thickness, arc of length and depth of implantation), anterior maximum keratometry (Kmax) and thinnest pachymetry were measured by Pentacam® in patients who had extrusion. Chi-square test and variance analysis were used with significance defined as p<0.10. Best-corrected visual acuity (BCVA) improvement at final consult and extrusion rate was calculated. To construct an extrusion predictive index (EPI), multiplication of pachymetry by keratometry was used. EPI sensitivity, specificity, positive and negative predictive value were obtained

One hundred fifteen eyes of eighty-four patients were analyzed (mean age 23.15, 63% males). Mean follow-up was 3.22 years. BCVA improved or remained the same in 87% of eyes. Extrusion rate was 10.43% and occurred in two-thirds of cases after one year of ICRS implantation. Thinnest pachymetry ≤460µm (ADEVA p=0.04888) and anterior maximum keratometry ≥60D (Kruscal-Wallis, p=0.04375) were associated with extrusion. Eye rubbing, ICRS characteristics (thickness, arc of length and depth of implantation) were not associated with extrusion (p >0.10). EPI had 83.3% sensitivity, 50.5% specificity, positive predictive value 16.4% and 96.3% negative predictive value for extrusion

Demographic characteristics as age, sex, eye rubbing and ICRS characteristics (thickness, arc of length, and depth of implantation) were not associated with extrusion in the population studied. Thinnest pachymetry ≤460µm and anterior maximum keratometry ≥60D were associated with extrusion. The proposed extrusion predictive index (EPI) might be useful, having an important negative predictive value. More patient data and prospective trials are needed to validate it.