Extremely Steep Keratoconic Cornea without Corneal Hydrops; How Far Can Corneal Thinning Progress?

We report a 51‑year old male patient with advanced keratoconus who presented to our clinic. He was diagnosed with keratoconus in 1986 and registered severely sight‑impaired in 2006. His medical history included hay fever and asthma. He had no family history of keratoconus and rubbed his eyes excessively for many years. The patient was wearing scleral contact lenses and managing well. His contact lens‑corrected visual acuity was 6/30 in the right eye (OD) and 6/30 in the left eye (OS). On slit‑lamp examination, we observed advanced keratoconus (OD>>OS) with extreme corneal thinning and marked Munson’s sign OD [Figure 1]. Corneal topography found advanced keratoconus bilaterally with a maximum keratometry of 112.7 diopters OD and 70.9 diopters OS [Figure 2a]. The thinnest point corneal thickness was 184 microns OD and 280 microns OS, as measured using ocular coherence tomography‑assisted corneal pachymetry [Figure 2b]. Despite the extremely advanced keratoconus, particularly OD, there was no evident corneal scarring and the patient had no episodes of acute corneal hydrops (ACH). The patient refused corneal transplantation because he was managing well with his scleral contact lenses.