|Year : 2014 | Volume
| Issue : 3 | Page : 152-154
Atoll sign in posterior lenticonus: A case report of bilateral posterior lenticonus with review of literature
Pratyush Ranjan, Deepak Mishra, Madhu Bhadauria
Department of Ophthalmology, Regional Institute of Ophthalmology and Sitapur eye Hospital, Sitapur, Uttar Pradesh, India
|Date of Submission||03-Aug-2013|
|Date of Acceptance||10-Mar-2014|
|Date of Web Publication||16-Aug-2014|
Dr. Pratyush Ranjan
Regional Institute of Ophthalmology and Sitapur Eye Hospital, Sitapur, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
Posterior lenticonus is a rare progressive disease characterized by protrusion of posterior lens capsule along with lens cortex into the vitreous cavity. Posterior lenticonus is more common but present unilaterally unlike anterior lenticonus, which presents bilaterally. Posterior lenticonus is a common cause of unilateral infantile cataract but is a very rare cause of bilateral cataract. Diagnosis is mainly clinical but can be difficult in asymptomatic patients; oil drop sign (in mild posterior lenticonus) and fish tail sign (lenticular cortex hanging in vitreous cavity after posterior capsular dehiscence) are described in posterior lenticonus. We are proposing an atoll sign in advanced case of posterior lenticonus with intact posterior capsule on slit lamp examination. The positive atoll sign will have more favorable prognosis since posterior capsule is intact, hence posterior chamber intraocular lens implantation will be more feasible with better visual prognosis as was the case with our patient.
Keywords: Activating Signal Cointegrator (ASC) 2, atoll sign, cataract, crystalline lens, Lowe syndrome, phacoemulsification, posterior lenticonus
|How to cite this article:|
Ranjan P, Mishra D, Bhadauria M. Atoll sign in posterior lenticonus: A case report of bilateral posterior lenticonus with review of literature. J Clin Ophthalmol Res 2014;2:152-4
|How to cite this URL:|
Ranjan P, Mishra D, Bhadauria M. Atoll sign in posterior lenticonus: A case report of bilateral posterior lenticonus with review of literature. J Clin Ophthalmol Res [serial online] 2014 [cited 2020 Jul 11];2:152-4. Available from: http://www.jcor.in/text.asp?2014/2/3/152/138861
Posterior lenticonus is a rare progressive disease characterized by protrusion of posterior lens capsule along with lens cortex into the vitreous cavity. It may be associated with local thinning or absence of posterior lens capsule. It was first reported by Meyer in 1888.  It generally occurs sporadically, but familial cases have also been reported. Out of the two lenticonuses, anterior and posterior, posterior is more common but present unilaterally unlike anterior lenticonus, which presents bilaterally and is mostly associated with systemic disorders like Alport syndrome. Posterior lenticonus is a common cause of unilateral infantile cataract but is a very rare cause of bilateral cataract. 
We report a rare case of bilateral posterior lenticonus and propose an atoll sign for it, which is considered positive in advanced case of posterior lenticonus with intact posterior capsule on slit lamp examination.
| Case Report|| |
A 22-year-old male presented with diminution of vision in both eyes; left more than right since childhood but has worsened more since last six months. There were no associated systemic or metabolic findings. On retinoscopy, a scissoring reflex was observed in right eye, and his best corrected visual acuity was 5/60 in right eye and 2/60 in left eye. Intraocular pressure by applanation tonometer was 16 and 14 mm of Hg in right and left eye, respectively. Gonioscopy and fundus examination revealed normal findings. Slit lamp examination revealed a posterior lenticonus with cataractous changes in the lens in right eye [Figure 1]a; left eye showed an advanced cataractous change with a collapsed cone [Figure 1]b. Rest of the anterior and posterior segment examination did not reveal any abnormality. Ultrasound biomicroscopy (UBM) confirmed the diagnosis [Figure 2]a and b. Patient was operated on right eye with phacoemulsification and three piece intraocular lens placement in the bag with uneventful outcome; his best corrected visual acuity after one month was 6/6. Left eye was operated one month later, and single piece foldable intraocular lens was placed in sulcus. Left eye didn't improve beyond 6/24 probably due to amblyopia.
| Discussion|| |
The lens is surrounded by a lens capsule, which is a basement membrane secreted by the capsular epithelial cells and is mainly composed of type IV collagen. Lenticonus is localized bulging of the lens capsule and the underlying cortex that can reach a diameter of 2 to 7 mm; the conus may occur anteriorly or posteriorly. Lenticonus is differentiated by lentiglobus, in which the bulging involves the entire lens surface. On slit lamp, lenticonus is characterized by a transparent, localized, sharply demarcated conical projection of the lens capsule and cortex usually in axial section. In early stage, retro-illumination shows an oil drop configuration. In more advanced stages, associated sub capsular and cortical opacities also appear.
The pathogenesis of posterior lenticonus remains elusive, though various hypotheses have been postulated like rupture of the posterior lens capsule resulting from hyaloid artery traction or trauma, congenital weakness of posterior capsule, aberrant hyperplasia of the sub capsular epithelium overlying the cone, disturbances in the tunica vasculosa lentis, vitritis or an overgrowth of posterior lens fibers that produce a phakoma of the lens. 
In bilateral cases, genetically determined congenital weakness of the posterior lens capsule is likely, which is usually X-linked and autosomal-dominant. Its association with Lowe's syndrome can be explained by Lyon's hypothesis of deactivation of X chromosome.  Recent discovery of a transcriptional co-activator molecule, ASC-2, has shown various developmental anomalies including posterior lenticonus with cataract in mouse models. 
The prevalence of posterior lenticonus is 1 to 4 of every 100,000 children and most cases are diagnosed between 3 to 15 years. There is no sex predilection for posterior lenticonus.  The presentation may be varied from asymptomatic to complex astigmatism leading to amblyopia and strabismus. All patients develop cataractous changes with time at the level of the lenticonus which can spread to the adjacent sub-capsular cortex.
Posterior lenticonus is reported to be associated with other ocular and systemic congenital anomalies. Duane retraction syndrome, microphthalmos, microcornea, keratoconus, iris, retinal pigment epithelial and lens colobomas, anterior chamber angle anomalies, anterior lenticonus, persistent hyaloid artery remnants, axial myopia, morning glory syndrome, and retinoblastoma are reported ocular associations, whereas Alport, Down and Lowe syndrome are reported systemic associations. , A new MPPC syndrome having bilateral Microcornea, Posterior megalolenticonus, Persistent fetal vasculature, and chorioretinal Colobomas has also been described. 
Diagnosis is mainly clinical but can be difficult in asymptomatic patients; oil drop sign (in mild posterior lenticonus) and fish tail sign (lenticular cortex hanging in vitreous cavity after posterior capsular dehiscence) are described in posterior lenticonus.  We are proposing an atoll sign [Figure 3]a in advanced case of posterior lenticonus with intact posterior capsule on slit lamp examination. The positive atoll sign will have more favorable prognosis since posterior capsule is intact, hence posterior chamber intraocular lens implantation will be more feasible with better visual prognosis. Atolls are annular mid ocean geographic formations [Figure 3]b. Where a water body (lagoon) is surrounded by rocks/sand/gravel, similarly in advance posterior lenticonus with intact posterior capsule, appear like atoll, with central posterior cone, which is clear (appear as lagoon) surrounded by lens material showing cataractous changes. The term "atoll" is derived from a Maldivian (divehi) word "atolu." 
Treatment consists of clear or cataractous lens extraction, optical correction along with prompt amblyopia therapy.  In patients with positive atoll sign, phacoemulsification with posterior chamber intraocular lens should be attempted and generally the prognosis is good.
| References|| |
|1.||Meyer F. Ein Fall von. Lenticonus posterior. Zentralbl Prakt Augenheilkd 1888;12:41. |
|2.||Jacobs K, Meire FM. Lenticonus. Bull Soc Belge Ophtalmol 2000;277:65-70. |
|3.||Kilty LA, Hiles DA. Unilateral posterior lenticonus with persistent hyaloid artery remnant. Am J Ophthalmol 1993;116:104-6. |
|4.||Russell-Eggitt IM. Non-syndromic posterior lenticonus a cause of childhood cataract: Evidence for X-Linked inheritance. Eye (Lond) 2000;14:861-3. |
|5.||Kim SW, Cheong C, Sohn YC, Goo YH, Oh WJ, Park JH, et al. Multiple development defects derived from impaired recruitment of ASC-2 To nuclear receptors in mice: Implication for posterior lenticonus with cataract. Mol Cell Biol 2002;22:8409-14. |
|6.||Kralich RG, Boyce PJ. Treatment options for concurrent ocular disease presenting with posterior lenticonus. Optom Vis Sci 1998;75:468-75. |
|7.||Cao XG, Li XX, Bao YZ. Morning glory syndrome associated with posterior lenticonus. Open Neurol J 2009;3:45-7. |
|8.||Ranchod TM, Quiram PA, Hathaway N, Ho LY, Glasgow BJ, Trese MT. Microcornea, posterior megalolenticonus, persistent fetal vasculature, and coloboma: A new syndrome. Ophthalmology 2010;117:1843-7. |
|9.||Woodroffe CD, Biribo N. Atolls. In: Hopley D, editor. Encyclopedia Of Modern Coral Reefs: Structure, Form And Process. Dordrecht The Netherlands: Springer; 2011. p. 51. |
|10.||Mistr SK, Trivedi RH, Wilson ME. Preoperative considerations and outcomes of primary intraocular lens implantation in children with posterior polar and posterior lentiglobus cataract. J AAPOS 2008;12:58-61. |
[Figure 1], [Figure 2], [Figure 3]