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15 years of outcomes and complications of angle-supported phakic intraocular lens model (ZB5M) for high myopia

Poster Details

First Author: A.Abbouda SPAIN

Co Author(s):    J. Alio   P. Peña-Garcia   S. Huseynli        

Abstract Details



Purpose:

The aim of this study was to evaluate the potential long term risk associated to ZB5m PIOL implantation. Several studies have reported the refractive predictability and safety for these models, the longest reported follow-up was of 7 and 12 years However, as available data concerning the long-term follow-up of eyes implanted with PIOLs remains limited, the stability in terms of efficacy, safety, and predictability has not yet been demonstrated for a period of over 15 years. In this study, we report the results of a large, retrospective, non-randomized, cumulative clinical study performed in a consecutive group of patients implanted with the ZB5M angle-supported PIOL. We describe the refractive status and the main parameters related to ocular safety evaluated 15 years and more after implantation.

Setting:

Patients who were implanted with Baikoff ZB (Domilens, Lyon, France) at VISSUM Corporacion Oftalmológica de Alicante between 1990 to 1996 were identified through surgical records (n=123; 208 eyes). From these, 44 patients could not be contacted by phone, 3 had died; 26 refused to be involved in the study, therefore from the original group, 50 patients (97 eyes) had follow-up data available of over 15 years.Inclusion criteria were age > 20 years at the date of implantation, ZB5m PIOLs implanted, anterior chamber depth at the period of implantation ? 3 mm from the corneal endothelium to the anterior capsule of the lens, endothelial cell density ?2000 cells/mm2 in patients aged ?25 years and 2500 cells/mm2 for younger patients. Exclusion criteria were different models of PIOLs implanted, uveitis, cataract, glaucoma at the presentation, anatomical alteration and previous surgery of the anterior chamber and angle, follow up of less than 15 years. For each patient we considered the age at the first visit, the age of implantation, the age of explantation, the date of onset of each complication (cornea decompensation, pupil ovalization, glaucoma, cataract, uveitis, retinal detachment)

Methods:

To analyze the corneal endothelial we used the Konan 5500 analyzer (Konan Camera Research Institute Inc, Hyogo, Japan). For follow-up performed after July 2000, a noncontact Topcon SP-2000P analyzer (Topcon, Tokyo, Japan) was used. To evaluate the amount of endothelial cell loss (ECL), we used this formula: ECDi = ECD0 (1 - % of loss/100)*n where ECDi is the current cell density estimated at any moment, ECD0 is the cell density at the first visit and n follow up /years. Best correct visual acuity (BCVA), slit-lamp microscopy, IOP, and fundus examinations were performed at all follow-up visits. A significant number of patients failed to attend some of the postoperative visits. All data were tabulated and analyzed using the statistical package SPSS 17 for Windows (SPSS, Chicago, Ill). Incidence rates were calculated as the number of events or complications divided by the number of eyes at risk during the year (EY).

Results:

The mean BCVA at the preoperative visit was 0.35ḟ0.20d (0.05-0.8) at the end 0.56ḟ0.30d (0.01-1).( p<0.01). 30% of eyes lost lines of BCVA during the follow up. 70% of eyes gained lines of BCVA. The median improvement was 0.4 (0.1-0.7). Mean endothelial cell density preoperatively and at the end of the follow-up was 2783±787 cells/mm2 and 1921ḟ672 cells/mm2, respectively (p<0.01). The median coefficient of ECL was 17.5% (min 5.2- max 72.7).The incidence of cataract during the follow-up was 0.010 eye-year (EY) among eyes with ZB5M implanted and free of cataract at the first visit. Cornea decompensation 0.001 EY, ocular hypertension was 0.008 EY, pupil ovalization 0.020 EY uveitis 0.001EY, retinal detachment 0.002 EY and IOL decentration 0.002. The median time of elevetad IOP onset during a follow up was 18.8+/-0.5 years (95% CI, 17.6-20.4). The median onset of cataract was 20.5 +/-0.5 years (95% CI, 16.7-18.7). The median onset of pupil ovalization was 16.5+/-0.6 years (95% CI, 15.2-17.8) . Corneal decompensation was found only in 1 eye at 19 years of follow up. During the follow up 29 eyes (29.8%) were explanted. The median time of explantation was 12.3ḟ0.5 years (95% IC 11.2-13.3).

Conclusions:

Pupil ovalization is the most frequent complication, and occurs as a consequence of PIOL oversizing causing compression and ischemia of the iris root. This complication is one of the most difficult to avoid. The long term risk of developing cataracts after PIOLs is still controversial. The average age of diagnosis of cataract was 47.3ḟ5.3 (35.5-61.8). Fifteen of the 97 eyes with follow-up of over 15-years had IOP >21 mmHg in the absence of treatment. Thirteen of these patients also had a nuclear cataract. The high IOP would be more related to cataract and angle dimension change than PIOL. Furthemore, the median time of onset of elevated IOP was observed to be quite similar to the age of onset of cataract. Another potential risk is ECL. The relationship between ECL and age has been described. We found this rate about 0.97% every year .Two different mechanisms have been proposed to explain the deterioration of endothelial cell density: the excessive proximity of the PIOL parts to the corneal endothelium, which may intermittently or permanently be in contact with the posterior part of the cornea or the presence of inflammatory mediators in the aqueous humor produced by any kind of trauma to uveal structures. The relative long term safety is confirmed especially regarding the lack of severe complications. The ZB5M design resulted to be safe and stable over a long period of time. Furthermore age changes related to crystalline size suggest postoperative follow up examinations on a yearly basis are necessary in patients older than 40, analyzing anterior chamber and angle depth modifications and recommending PIOL explantation when the safety zone between the PIOL and endothelium is affected.

Financial Disclosure:

NONE

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