Asteroid hyalosis (AH), first described by Benson in 1894, is a degenerative vitreous condition that leads to small yellow-white spherical asteroid bodies that fill the vitreous cavity of the eye.1 The precipitates are composed of calcium phosphate crystals and generally have a minor impact on vision.2 However, if visual disturbances are severe, although uncommon, vitrectomy may be considered even in unilateral AH.3 The most common complaint reported in AH is decreased vision. It is interesting to note that even in severe cases of AH that make fundus examination very challenging, vision is often minimally affected.4 Of interest, in a recent case series of 195 cases of vision-degrading floaters treated by limited vitrectomy, only 6.7% had AH.5
IOL explantation for dystrophic calcification has been reported with several IOL materials in patients with AH. In the past, silicone IOLs were believed to be resistant to secondary calcification in patients with AH; however, several articles have reported calcification with different silicone IOL designs and manufacturers. However, none have been reported in an accommodating silicone IOL (Crystalens AO, Bausch & Lomb, Inc.) in the context of AH. We describe a case below. In addition, we review the available literature on dystrophic calcification of silicone IOLs and comment on suggested management for improving visual symptoms in these patients.
A 57-year-old nondiabetic, hypertensive man with reduced vision presented to an academic center in Boston, Massachusetts, USA. He had a history of AH in the left eye more than in the right eye and had undergone cataract surgery 14 years earlier with an accommodating silicone IOL implant (Crystalens AO) in both eyes at an outside facility. He subsequently developed deposits on the posterior surface of both IOLs, left eye more than right eye, and was treated with a YAG capsulotomy bilaterally in 2016 with no reported visual improvement. Owing to persistent visual symptoms, he underwent a pars plana vitrectomy (PPV) with posterior IOL polishing in the left eye 1 year later. This was followed by repeated YAG treatment and IOL repositioning in the left eye 1 year later with no resolution of his symptoms. He presented to our institution with the above-mentioned chief complaint for the evaluation of possible IOL exchange in the left eye. He stated his visual complaints had been stable for 2 years and described a blob obscuring his central vision in the left eye.
On examination, his visual acuity at presentation was 20/30 in the right eye and 20/80 in the left eye with pressures of 21 mm Hg and 15 mm Hg by Tono-Pen XL (Reichert Technologies), respectively. On confrontational field, a left peripheral inferonasal defect was noted. Slitlamp examination revealed a Crystalens AO IOL in the capsular bag with dense diffuse deposits on the posterior IOL surfaces bilaterally with open posterior capsules. Fundus examination revealed AH in the right eye and the left eye was consistent with status post-PPV without AH. In addition, there was an epiretinal membrane (right eye) and bilateral blunted foveal reflexes. After reviewing the findings with the patient and discussing the risks of the procedure, the patient elected to proceed with surgery. Photographs were taken at the time of the examination (Figure 1).
At surgery, an opacified Crystalens AO IOL was explanted from the left eye along with the capsular bag and exchanged through a 6 mm short scleral tunnel incision. A 3-piece hydrophobic acrylic IOL (CT Lucia 602, Carl Zeiss Metich AG) was placed using the Yamane technique (intrascleral fixation).A The explanted IOL was sent to pathology for H&E and von Kossa staining.
There were no complications during the postoperative follow-up visits through 6 months, and vision had improved to 20/40 by 1 week. His vision remained stable; however, he has been followed by a retina specialist for macular edema, which may contribute to his limited improvement of vision. In addition, the medical literature was reviewed for reports of silicone IOL opacification in the context of AH.
Grossly, the lens deposits were largely confined to the posterior surface of the Crystalens AO IOL (Figure 2). The pathology report on the explanted IOL confirmed the presence of calcium deposits; however, images were not available. The IOL was bisected, and one half was embedded in paraffin and sectioned. The H&E sections show that the IOL failed to take up stain. Separately, one half of the lens prosthesis was embedded in Epon resin (epoxy). However, the processing turned the IOL black, making it unsuitable for electron microscopy.
Silicone IOLs are polymers of silicone and oxygen and are considered to be very stable and inert in vivo. Unlike other materials, they rarely adhere to either tissues or foreign bodies.6 In our review, the first reported case of silicone IOL deposits in AH was documented in 2004.7 Since then, there have been 37 other reported cases with various IOL designs by various manufacturers. Table 1 summarizes the characteristics of all cases reported in order of publication. Of the 37 cases reported, none included an accommodating silicone IOL implant.
Twenty-four of the 34 cases underwent lens explantation with analysis of the IOL deposits, all of which were proven to be composed of phosphorus and calcium, strengthening the link to AH. Two cases had no further information on the management of the lens deposits,8,9 and 3 eyes had undergone a PPV.4,10,11 In patients with a PPV, the condition did not seem to regress, and only a minority of cases were visually satisfied with the results. Most eventually required an IOL exchange to improve vision. All cases reported the deposits were limited to the posterior surface of the IOL, which is consistent with the clinical findings in our patient. It has previously been suggested that direct contact of the vitreous with the silicone IOL after Nd:YAG capsulotomy in a patient with AH hastens the dystrophic calcification of the IOL.8 Indeed, of the 22 cases reported with documented status of the posterior capsule, 19 had undergone a previous capsulotomy and only 3 eyes had not (Table 1). As such, this condition has been described in most cases after Nd:YAG capsulotomy, although several reports with intact capsules exist. Recently, a report on managing a patient's IOLs with PPV plus a silicone tipped cannula used to polish the posterior lens surface was published.12 This patient failed to improve after YAG capsulotomy and PPV, even with high vacuum. An IOL exchange was deferred because of Fuchs endothelial dystrophy. As such, microforceps and a silicone tipped flute were used to polish the IOL deposits. Although a significant amount of calcification seemed to have been removed, the results were disappointing with limited improvement of vision (20/60 preoperatively to 20/40 in the immediate postoperative period) because of the smearing of the deposits that were described to have a putty-like consistency.
Another new surgical technique has been described by Schachar and Leng by using a standard 25-gauge sutureless PPV and a nitinol loop to create repeated passes across the posterior lens surface of calcified silicone IOLs.13 A total of 7 eyes have been reported in the literature.13,14 All patients had improvement of corrected distance visual acuity with no recurrence of calcification and improvement of glare with a mean of 7.5 months of follow-up (Table 2). No scratches were found on the posterior lens, but the mean follow-up was limited to 7.5 months with only 7 eyes described. In addition, all eyes had a relatively good CDVA preoperatively. Although these results are promising, longer follow-up and a larger sample size are required to determine the adequacy of treatment. This technique seems to be an adequate alternative to IOL exchange and could be considered in cases in which other conditions render an IOL exchange high risk.
Of interest, in another report, a patient with bilateral AH received a different IOL in each eye composed of different materials. Deposits developed on the posterior surface of the silicone IOL but not on the hydrophobic acrylic IOL after a follow-up of 6 years.8 This finding is consistent with the concept that a silicone IOL may not be the best choice for a patient with AH.
Consistent with the above-mentioned findings, a recent literature review of IOL opacification in different IOL materials showed that the rate of opacification for acrylic hydrophobic IOLs was less compared with poly(methyl methacrylate) and acrylic hydrophilic IOLs.15 The rate of opacification in hydrophilic acrylic IOLs was recorded to be 7% in a follow-up study of 102 patients over 4 years.16 Based on these findings, a hydrophobic acrylic IOL should be considered as the primary IOL material for patients with AH or as the material of choice if an IOL exchange is required in the future, as with our patient.
Although the performance of cataract surgery is usually not influenced by AH, the selection of IOL materials can be impacted by the presence of vitreous asteroid bodies because silicone material has the highest correlation with opacification in the literature. We suggest using the IOL material with the lowest rate of documented opacification in AH, a hydrophobic acrylic IOL. For the management of secondary deposits on IOLs, explantation and lens exchange remains the best option for improving visual symptoms. Nonetheless, some new management approaches have been reported with promising results, especially in high-risk cornea cases. However, these techniques need a longer follow-up period and larger number of cases. Finally, the literature suggests that YAG laser capsulotomy may hasten silicone IOL opacification, and we recommend against capsulotomy unless absolutely necessary because this seems to accelerate calcification of the IOL posterior surface and renders IOL exchange more challenging.
WHAT WAS KNOWN
- In asteroid hyalosis, dystrophic calcification of the intraocular lens (IOL) may occur with several materials.
WHAT THIS PAPER ADDS
- Silicone IOLs are at risk for opacification in the presence of asteroid hyalosis, including those designed for accommodation.
- Explantation and lens exchange seem to remain the best option for improving visual symptoms.
- YAG laser capsulotomy might hasten silicone IOL opacification.
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OTHER CITED MATERIAL
A. Yamane S, Inoue M, Arakawal A, Kadonosono K. “Yamane technique: Sutureless 27-Gauge Needle–Guided Intrascleral Intraocular Lens Implantation with Lamellar Scleral Dissection”, presented at the American Academy of Ophthalmology Annual Meeting, Chicago, Illinois, USA, November 2012