Bilateral spontaneous dislocation of posterior chamber intraocular lens in a patient with gyrate atrophy.

We report a patient with gyrate atrophy, a rare metabolic disease, who had bilateral late spontaneous posterior dislocation of in-the-bag posterior chamber intraocular lens (PCIOL). He underwent pars plana vitrectomy, PCIOL retrieval and anterior chamber intraocular lens implantation in both eyes. This report may imply that patients with gyrate atrophy are at risk for spontaneous dislocation of intraocular lenses.

Posterior dislocation of in-the-bag posterior chamber intraocular lens (PCIOL) is a rare complication in pseudophakic patients in the absence of ocular trauma, particularly if it occurs years after uneventful cataract surgery. Gyrate atrophy, which is a rare metabolic disease with an autosomal recessive inheritance, is even rarer in the Indian population but has been reported previously in two female siblings.[1] The metabolic defect is the result of a mutation in the gene encoding the main ornithine degradation enzyme, Ornithine Amino-Transferase (OAT). This mutation leads to an elevated ornithine level in body fluids. The ocular phenotype includes axial myopia, reduction in peripheral vision and nyctalopia. The typical fundoscopic finding of areas of chorioretinal atrophy accompanied by elevated serum ornithine levels confirm the diagnosis. Treatment for gyrate atrophy is directed towards lowering plasma and urine ornithine levels by either arginine-restricted diets[2] or ingestion of vitamin B6 (Pyridoxine).[3] Here we describe a case of bilateral late spontaneous posterior dislocation of PCIOL in a patient with gyrate atrophy.

Case Report

A healthy 68-year-old patient presented in July 2005 with spontaneous dislocation of an in-the-bag PCIOL in his right eye, which was lying on the retina. He denied any trauma to the eye. His ophthalmic history was remarkable for axial myopia (right eye 27.13 mm, left eye 26.32 mm) and previous bilateral uneventful phacoemulsification and implantation of a plate haptic silicone intraocular lens (IOL, STAAR ® design), performed nine years earlier. Neodynium-YAG capsulotomy was performed in either eye. His visual acuity was 20/400 (uncorrected) in his right eye (20/50 with +7.0 D), and 20/60 (uncorrected) in his left eye. The IOL in the left eye was in-the-bag with pseudophacodonesis. Fundus findings in both eyes included pale optic discs, extensive chorioretinal atrophy with scalloped borders and sparing of the mid periphery, consistent with the diagnosis of gyrate atrophy [Fig. 1]. There was a central atrophic area involving the macula in both eyes. Blood and urine samples were taken for ornithine levels. Serum ornithine levels were 758 mmol/ml (normal range 48-195 mmol/ml) and hyperornithuria was also detected, confirming the diagnosis of gyrate atrophy.

Figure 1

Right eye showing typical retinal changes of gyrate atrophy

He underwent pars plana vitrectomy (PPV) in the right eye, the PCIOL was retrieved from the vitreous cavity and explanted, and an anterior chamber IOL (ACIOL) was implanted. The visual acuity improved to 20/50 (uncorrected) and remained stable until the end of follow-up. In March 2008 he presented with full dislocation of the in-the-bag PCIOL into the vitreous in the left eye. Again, The IOL was lying on the retina. His visual acuity declined to 20/400 in that eye. Again, there was no history of ocular trauma. He underwent PPV with retrieval of the PCIOL from the vitreous [Fig. 2] and ACIOL implantation. During a follow-up of 18 months the ACIOL was stable, and visual acuity returned to 20/50 without correction.

Figure 2

Intraoperative picture showing “in-the-bag” dislocation of the intraocular lens in the left eye into the vitreous space

Discussion

Late bilateral dislocation of a PCIOL in a patient with gyrate atrophy has been previously described.[4] The dislocations however, were into the anterior chamber. The IOL in the right eye returned to its original location after supine positioning and pupil dilation, and the left eye required surgical repositioning. The cause of spontaneous dislocation of the IOLs in that patient, as well as in our patient, is unknown. It should be noted that posterior dislocation of a silicone plate haptic IOL, similar to the lens implanted in our patient, is a well-known complication after YAG capsulotomy or traumatic cataract surgery due to lack of adherence between the silicone IOL and the lens capsule. Capsular fibrosis along the capsulorrhexis rim exerts a centripetal force on the plate haptic that forces the posterior lens surface against the elastic posterior capsule, indenting and stretching it. Defects in the capsular integrity thus provide potential means for release of stress on the “spring-loaded” IOL and may result in sudden expulsion of the IOL into the vitreous cavity.[5] However, in our patient the posterior capsules were intact. Moreover, the IOL dislocated with the bag, pointing to a different mechanism than the one described above. In our case, and in the previously reported one,[4] there was no evidence of known risk factors for in-the-bag PCIOL dislocation such as ocular trauma,[6] pseudoexfoliation[7] or uveitis.[8] This may imply that patients with gyrate atrophy are at risk for spontaneous dislocation of in-the-bag IOLs, most probably resulting from zonular disruption, as has been described in some connective tissue disorders (e.g. Marfan syndrome, homocystinuria, Ehlers-Danlos syndrome, hyperlysinemia and Weill Marchesani syndrome). We suggest that patients with gyrate atrophy should have their cataract surgery performed only by experienced surgeons, with emphasis on exerting only minimal traction on the zonules in order to reduce the likelihood of tearing or disrupting them, thus reducing the likelihood of late subluxation or dislocation of in-the-bag PCIOL. Furthermore, such patients should be instructed to have regular eye examinations in order to detect the subluxation of the IOL in its initial phase. Early detection may allow surgical fixation of the IOL prior to its dislocation.