Early Stage Keratoconus Characterized by Posterior Segment Alterations

Early-stage keratoconus (KC) may be characterized by a bowing of the lamina cribrosa (LC), subtle peripapillary retinal nerve fiber layer (RNFL) thinning and vascular impairment, according to a study published in the American Journal of Ophthalmology.

Researchers included 64 participants in an observational, cross-sectional analysis consisting of individuals with KC (n=32; 69% men; mean age, 26.92 years) and age- and sex-matched control individuals (n=32; 69% men; mean age, 26.66 years). Similar mean axial length, intraocular pressure (IOP) and best-corrected visual acuity (BCVA) were noted between the groups at baseline.

All participants underwent anterior segment optical coherence tomography (OCT) imaging, peripapillary RNFL thickness measurements, macular and optic nerve head swept-source (SS)-OCT radial scans and SS-OCT angiography 3×3 mm cube scans.

Patients with KC had thinner peripapillary RNFL thicknesses (104.8 vs 110.7 μm; P = 0.039) and reduced nerve radial peripapillary capillary plexus vessel densities (46.31% vs 43.82%; P =.006) compared with individuals in the control group. 

The differences were more pronounced in the temporal sector and were associated with a higher lamina cribrosa curvature index (KC group, 9.9% vs control group, 8.48%; P =.012). The mean macular superficial capillary plexus vessel density was reduced by 2.74% in patients with KC compared with control group participants (P <.001). Central macular thickness and central corneal thickness were similar among the 2 groups (both P >.05).

“These results seem to suggest a similar optic nerve head impairment between KC and early glaucoma, with the only difference of a primarily altered structure, rather than elevated IOP, as the cause of LC deformation that ultimately leads to the damage of nerve fibers in KC,” according to the study authors. 

Study limitations include a small sample size, failure to assess corneal biomechanical properties, and the potential introduction of errors due to the manual collection of LC measurements. 

Disclosure: One study author declared affiliations with biotech, pharmaceutical, and/or clinical research organizations. Please see the original reference for a full list of authors’ disclosures.