Posterior lenticonus was first described by Meyer in 1988 is a conical bulge of the posterior lens surface into the vitreous cavity associated with local thinning or absence of posterior capsule.1 Most cases are unilateral, not associated with any systemic or ocular abnormality, seem to occur sporadically, and present in infancy or early childhood.2 Presence of a preexisting posterior capsular defect (PCD) in these cases might complicate the surgery. Thus, any clinical sign or imaging modality, which can preoperatively predict the presence of a PCD, might lead to better surgical outcomes in such situations.
Previously, Ranjan et al. described the atoll sign for advanced posterior lenticonus with intact posterior capsule on slitlamp examination.3 According to the authors, a positive atoll sign had a central clear zone with intact posterior capsule surrounded by an area of cataractous changes, and its presence was associated with favorable outcomes. An atoll is a ring-shaped coral reef including a coral rim that encircles a clear lagoon. We describe an inverse atoll sign in cases with posterior lenticonus having cataract and a PCD. The inverse atoll can be described as the presence of central lens opacification surrounded by a clear space or halo and then a concentric opaque rim, which is the volte-face of a typical atoll reef. The presence of PCD in our patients was supported by swept-source optical coherence tomography (SS-OCT) preoperatively and confirmed intraoperatively.
A 7-year-old boy presented with a white reflex in the right eye along with diminution of vision, which was noticed by his parents for the previous 3 months. Ocular examination revealed a corrected distance visual acuity (CDVA) of 20/400 with no manifest refractive error in the right eye and 20/30 with +1.50+0.75 × 90 in the left eye. On slitlamp examination, the right eye had posterior polar cataract along with the posterior coning of the lens. The dense white central lenticular opacity corresponded with the apex of the cone. This central opaque zone was surrounded by a clearer zone or halo, which was further surrounded by a concentric rim of opacification (Figure 1, a). The nomenclature inverse atoll sign was proposed because the appearance described here is inverse of the appearance of an atoll reef. The left eye showed early posterior subcapsular cataract (PSC) with a normal contour of the posterior lens capsule (Figure 1, b).
Bilateral anterior segment imaging was done using SS-OCT (CASIA 2, Tomey Corp.). The OCT images showed a conical contour of the posterior surface of the lens in the right eye, with lens thickness of 7.2 mm measured using lens analysis function on the SS-OCT (Figure 1, c). The posterior lens capsule, normally seen as a thin hyperreflective membrane at the posterior lens surface, showed discontinuity along with herniation of the cortical matter from the zone of capsular deficit. The edges of the posterior capsule at the margins of the defect showed a subtle outward angulation, which clinically could translate into the smooth, well-delineated appearance of the outer rim of the inverse atoll reef mentioned earlier. SS-OCT of the left eye showed a normal lens contour with intact posterior capsule and early cataractous changes corresponding to the PSC seen clinically (Figure 1, d).
A diagnosis of right eye posterior lenticonus with cataract was made, and thorough systemic evaluation was performed, which was unremarkable. Cataract surgery of the right eye was performed keeping the existence of a PCD in mind. A 5 mm continuous curvilinear capsulorhexis (CCC) was performed to maintain adequate sulcus support and no abnormal changes were noted in the anterior capsule. Hydrodissection was avoided, and lens matter aspiration was done using a bimanual irrigation/aspiration cannula under low flow parameters. A preexisting large oval PCD of approximately 5.5 mm in its greatest dimension as measured on CALLISTO eye rhexis guide (Carl Zeiss Meditec AG) was noted.
The configuration of the PCD was comparable with the outermost oval opaque ring of the inverse atoll noted on preoperative examination. It was hypothesized that the central opaque zone seen preoperatively was indicative of the cataractous herniating lens matter, the halo represented the lens matter around the PCD, which was still noncataractous and not herniating, and the peripheral rim of the inverse atoll reef was formed by the opacified edges of the PCD. Limited anterior vitrectomy was performed, and a 3-piece posterior chamber intraocular lens (IOL) was implanted into the sulcus with posterior optic capture to ensure IOL stability and centration. The patient attained a postoperative CDVA of 20/40 (with −1.50−1.50 × 50), and amblyopia therapy was initiated.
A 9-year-old girl presented with complaints of decreased vision in both eyes since birth. CDVA in the right eye was 20/40, and hand motion in her left eye. The left eye had a cataractous lens with posterior coning. Similar to case 1, in this patient also the central opaque zone was surrounded by a relatively clear area that was further encircled by an opaque rim along the posterior lens surface, forming an inverse atoll reef (Figure 2, a).
Anterior segment OCT of the left eye showed the posterior lens capsule as a hyperreflective membrane that was deficient centrally, signifying a PCD in that area and a globular herniation of the lens matter into the vitreous cavity (Figure 2, b). A relatively hyporeflective area was seen on either side of the globular protrusion, the outer limits being defined by the edges of the posterior capsule, which in this case also demonstrated an outward angulation. These hyporeflective zones would correspond to the intermediate clear zone or halo seen clinically.
Keeping in mind the possibility of a large PCD as suggested by clinical picture and supported by SS-OCT, a slow controlled lens matter aspiration using a Simcoe cannula was planned to ensure minimal turbulence in the anterior chamber. A circular anterior CCC of 5 mm was created, hydrodissection was avoided, gentle viscodissection was performed, and lens matter was aspirated. A large PCD, the configuration of which corresponded to the concentric opaque rim noted preoperatively, was detected intraoperatively, with dimensions of approximately 5.8 mm as measured on CALLISTO eye rhexis guide. The edges of the PCD extended beyond the borders of anterior CCC at 5 and 11 o'clock (Figure 2, c). Limited anterior vitrectomy was performed using a vitreous cutter, and a 3-piece posterior chamber IOL was implanted into the sulcus with optic capture.
Postoperative CDVA at 4 weeks was 20/60 with a refractive error of 1.0+1.75 × 80. The patient was prescribed spectacles and started on amblyopia therapy. The right eye of this patient had a PSC that accounted for the suboptimal vision. Figure 2, d shows the OCT of the right eye with a central hyperreflectivity arising from the posterior capsule and extending centrally (corresponding to the cataractous changes seen clinically), a normal contour of the posterior lens surface, and an intact posterior capsule.
Although extension of the PCD did not occur in either of the cases, the posterior capsule surrounding the PCD demonstrated excessive fluttering movements intraoperatively, suggestive of enhanced fragility. Considering the large size of the preexisting PCD combined with posterior capsular fragility, IOL implantation in the bag was not attempted in either case.
Many theories have been given to explain the pathogenesis of posterior lenticonus, including posterior traction caused by the hyaloid artery, an inherently weak posterior capsule, overgrowth of the posterior lens epithelium, and cortex producing lens phakoma.4–7 Although most cases of posterior lenticonus occurs sporadically, association has been found with Lowe syndrome, which is an X-linked disorder characterized by intellectual and developmental disabilities, renal dysfunction, corneal keloids, and glaucoma.8 Diagnosis of posterior lenticonus is mainly clinical. Some clinical signs have been described previously including the oil droplet sign on retroillumination and fish tail sign (lenticular cortex hanging in vitreous cavity after posterior capsular dehiscence).9
The 2 cases in this study had preexisting PCD, with anatomical picture exactly reverse of a typical atoll reef. To the authors' knowledge, the central opaque zone corresponds to the herniating cataractous lens matter in the vitreous cavity, the outermost opaque rim represents the borders of PCD, and some lens matter that is not herniating into the vitreous cavity and is as yet noncataractous (probably supported by the anterior vitreous face) forms the halo between the central opaque zone and the peripheral opaque rim. This clinical impression was supported by the SS-OCT findings preoperatively and confirmed intraoperatively. Other recommended modalities for imaging the posterior lens capsule are 20 MHz echography, ultrasound biomicroscopy, and Scheimpflug imaging.10 Echography and ultrasound biomicroscopy are contact-based imaging devices for which young children might not cooperate. Imaging using Scheimpflug-based devices, although noncontact and fast to acquire, fails to provide a precise view of the posterior lens surface. The swept-source anterior segment OCT (CASIA 2) used in our cases, uses a longer wavelength (1 310 nm), has a deeper scanning depth (10 mm), and gives excellent visualization of the anterior segment structures including the posterior lens surface. Because of its rapid image acquisition (50 000 A-scans/s), it is an excellent imaging tool for young children.
In conclusion, the awareness of the operating surgeons about the possibility of a preexisting capsular defect in cases of posterior lenticonus and recognition of clinical signs that reflect the status of the posterior capsule aided by appropriate imaging can help in safe execution of cataract surgery in these patients.
WHAT WAS KNOWN
- Various clinical signs, such as fish tail sign and atoll sign, to describe the posterior capsular integrity help surgeons anticipate intraoperative complications while managing cases of posterior lenticonus with cataract.
- Modalities such as ultrasound biomicroscopy (UBM) and Scheimpflug imaging are helpful in supporting the diagnosis because none of the clinical signs are definitive indicators of posterior capsular integrity.
WHAT THIS ARTICLE ADDS
- A new inverse atoll sign for preoperative detection of a posterior capsular defect (PCD) in cases of posterior lenticonus can serve as a reliable predictor of PCD even in the absence of other diagnostic modalities. Longer-wavelength swept-source optical coherence tomography to assess the integrity of posterior capsule was more advantageous than other conventional imaging modalities, such as UBM and Scheimpflug imaging.
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