Pseudo-Lenticonus Sign In Keratoconus: A Diagnostic Pitfall

Posterior lenticonus is traditionally regarded as a primary lenticular pathology diagnosed on slit-lamp biomicroscopy. However, in advanced keratoconus, severe corneal ectasia generates profound optical aberrations that convincingly simulate this sign, suggesting that pseudo-lenticonus may itself serve as a novel clinical hallmark of advanced ectasia. General ophthalmologists may misdiagnosis & unnecessary surgical intervention can be carried out without further imaging. This study aims to establish pseudo-lenticonus as a potential indicator of advanced disease and demonstrate how AS-OCT, offers a high-resolution imaging independent of corneal distortion, serves as a tool in confirming this distinctive association.

This study was conducted over a period of 30 days at Dr. RP Centre for Ophthalmic Sciences, New Delhi. Ten patients referred with a provisional diagnosis of posterior lenticonus underwent detailed slit-lamp biomicroscopy followed by AS-OCT imaging to objectively evaluate the posterior lens contour and accurately differentiate true lenticonus from pseudo-lenticonus secondary to advanced keratoconus.

This observational study enrolled 10 advanced keratoconus patients over 35 days at Dr. RP Centre for Ophthalmic Sciences, New Delhi. Each patient underwent assessment of uncorrected and best corrected visual acuity using LogMAR notation. Scheimpflug imaging with Pentacam HR (Oculus) was performed to obtain corneal topographic parameters including K1, K2, Kmax, central corneal thickness, anterior and posterior elevation maps, confirming disease severity. AS-OCT (TOMEY Cornea, Casia 2) was subsequently performed to directly image the posterior lens contour and objectively measure anterior curvature, posterior curvature, and lens thickness, enabling accurate differentiation of true posterior lenticonus from pseudo-lenticonus.

A study of 10 advanced keratoconus patients with a mean age of 28.55 ± 6.37 years was conducted over 35 days. Mean uncorrected visual acuity was LogMAR 1.36± 0.33 and best corrected visual acuity was LogMAR 1.32± 0.04, reflecting significant visual compromise. Pentacam imaging revealed severely ectatic corneas with mean K1 of 60.24 ± 4.05 D, K2 of 80.72 ± 4.18 D, and Kmax of 93.44 ± 3.24 D, confirming advanced disease. Mean central corneal thickness was markedly reduced at 408 ± 4.58 μm. AS-OCT evaluation demonstrated a mean anterior corneal curvature of 9.71 ± 0.22 mm, posterior curvature of 6.25 ± 0.26 mm, and lens thickness of 3.53 ± 0.04 mm, with no evidence of true posterior lenticonus in any case.

Advanced keratoconus can produce a convincing pseudo-lenticonus sign on slit-lamp examination & we propose that this finding may in fact serve as a novel clinical indicator of advanced corneal ectasia. Rather than representing true lenticular pathology, this deceptive optical phenomenon is generated by extreme corneal curvature and profound aberrations inherent to advanced disease. AS-OCT plays a pivotal role in confirming the absence of true posterior lenticonus by objectively imaging the posterior lens contour independent of corneal distortion. Recognizing pseudo-lenticonus as a potential hallmark sign of advanced keratoconus can aid in earlier disease recognition, preventing misdiagnosis and avoiding unnecessary surgical intervention.