Pellucid marginal degeneration (PMD) is a non-inflammatory ectatic corneal disease characterized by a narrow band of corneal thinning separated from the limbus by a relatively uninvolved area 1-2 mm in width. It is a rare corneal disorder that shares many clinical characteristics with other corneal ectasias, such as keratoconus, keratoglobus or Terrien marginal degeneration. PMD usually starts later in life than keratoconus and progresses slower than keratoconus. Slit-lamp examination is very useful to distinguish PMD from other corneal ectatic disorders with inflammatory nature. Corneal topographic indices and the classical crab-claw topographic pattern cannot be used as the main tool to distinguish between PMD and keratoconus. New Scheimpflug imaging-based devices have shown the importance and usefulness of the pachymetric map for an appropriate diagnosis of PMD. In addition, biomechanical and densitometric properties have been studied as complementary techniques to help in the diagnosis of PMD.

We report the case of a 3-year-old boy presenting with bilateral keratoglobus and blue sclera in addition to hallux valgus, arachnodactyly, small joint hypermobility, mitral valve dysfunction and a history of generalized muscular hypotonia in early infancy. Molecular genetics provided evidence of two pathogenic mutations in the ZNF469 gene (compound heterozygosity) leading to the diagnosis of brittle cornea syndrome type 1. In addition to neuropediatric care, spectacles were prescribed to correct refractive error and for ocular protection. Owing to the thin cornea and sclera, eye injuries are the main cause for irreversible visual loss in this disease.

Anterior megalophthalmos and keratoglobus are characterised by corneal thinning and deep anterior chamber. They are clinically distinguished on the basis of normal to slightly decreased corneal thickness with a large corneal diameter (>13 mm) in case of anterior megalophthalmos, and marked limbus-to-limbus corneal thinning with globular protrusion in keratoglobus. To achieve and maintain a centred and stable intraocular lens (IOL) position in the bag is often difficult in cases of anterior megalophthalmos due to a too large diameter of the capsular bag and ciliary ring. We report a case of a 40-year-old man with features of anterior megalophthalmos with extremely thin cornea. He had spontaneous posterior dislocation of IOL and capsular tension ring (CTR) within the bag after initial successful cataract surgery. The dislocated complex could neither have been repositioned with scleral fixation due to large diameter of ciliary ring nor could it have been explanted through a clear corneal incision due to associated very thin cornea. We performed pars plana vitrectomy and separated the IOL-CTR complex inside the eye and explanted them separately through the sclerotomy, as is done for removal of intraocular foreign body. This avoided incision on the thin cornea. We conclude that this method can be very useful in a similar clinical situation but is complex enough to justify its use in routine cases.