Lens subluxation in retinoblastoma – Where does it fit in the classification of retinoblastoma

Dear Editor, Lens involvement is unusual in retinoblastoma (RB). Lens subluxation can rarely be an associated presenting feature in advanced retinoblastoma.[1,2] Here, we highlight possible pathomechanisms of lens subluxation in eyes with histopathology (HPE) evidence. A 2-year-old child had bilateral retinoblastoma with group E[3] RB in the right eye (OD) with 270 degrees of superior ciliary staphyloma and subluxation of clear lens [Fig. 1a-c]. OD was enucleated after three cycles of systemic chemotherapy, and HPE showed lens subluxation [Fig. 1d] with no high-risk features (HRFs). The mechanism of lens subluxation is postulated to be secondary to disproportionate equatorial expansion corresponding to the staphyloma, causing zonular stretching and disruption, possibly a mechanical phenomenon. Another child, 2 months old, with bilateral retinoblastoma [Fig. 2], had features of orbital cellulitis, high intraocular pressure, hyphema, and inferiorly subluxated lens in OD [Fig. 2a and c]. Magnetic resonance imaging (MRI) ruled out orbital extension and confirmed lens subluxation [Fig. 2e and f]. After a short course of oral steroids and three cycles of systemic chemotherapy, OD appeared phthisical and was enucleated. HPE showed no HRF and confirmed the lens subluxation [Fig. 2g and h]. In this case, the lens subluxation appeared to be a consequence of orbital cellulitis and inflammatory reaction to necrotic tumor products that may cause degradation of zonules.[4,5] Orbital cellulitis in RB resolves with phthisis, which can possibly cause atrophy of zonules and secondary lens subluxation (not in our case). In both our cases, the tumor did not cause a mass effect in the area of zonules, as confirmed on HPE, and therefore, the abovediscussed hypotheses are most likely.Figure 1: (a) External photograph of right eye showing superior 270 degrees of ciliary staphyloma. (b) Right eye showing lens subluxation. (c) MRI showing ciliary staphyloma and lens subluxation in the right eye. (d) Histopathology of enucleated specimen of right eye showing subluxated lens with stretched out zonules superiorlyFigure 2: (a and b) External photograph of right eye at presentation and after 3 cycles of chemotherapy, respectively, showing inferonasal lens subluxation and hyphema. (c and d) Lens subluxation in the right eye at presentation and after 3 cycles of chemotherapy, respectively, with underlying tumor and vitreous hemorrhage. (e and f) MRI images at presentation showing inferonasal lens subluxation. (g and h) Histopathology of enucleated specimen of right eye showing subluxated lens with absent zonulesTumors arising anteriorly like ciliary body melanoma and medulloepithelioma may indent and result in subluxation of lens. Lens involvement in retinoblastoma is rare and has been reported in the form of tumor invasion into the lens or absent lens.[6,7] Unexplained anterior segment findings should raise suspicion, and mass lesions must be ruled out before any planned interventions. In our clinical experience, many of group E features often coexist. Lens subluxation may also coexist with any of these features, and in fact, the lens subluxation may be a consequence of these. The often-neglected anterior chamber findings seldom find their way into the standardized classifications.[3] Lens subluxation or dislocation denotes a structurally damaged anatomy and possible disruption of normal physiology. Eye salvage may not be possible in these cases, and enucleation is often performed. We therefore propose that lens subluxation, or lens involvement of any sort, denotes an advanced disease and should be considered as a feature of group E of retinoblastoma classification.[3]