Densitometry Details Subjective Corneal Haze Following Corneal Crosslinking

Subjective corneal haze — as assessed with slit lamp examination (SLE) — following accelerated corneal crosslinking (aCXL) significantly associated with objective corneal haze measured with densitometry, according to research published in Acta Ophthalmologica. Greater densitometry following aCXL is associated with a decrease in corrected distance visual acuity (CDVA), according to the report. 

The retrospective analysis included 483 eyes from 283 patients (mean age, 27.86 years; 71.7% men) with progressive keratoconus or other corneal ectasias who underwent aCXL between June 2013 and March 2015. Preoperatively and up to 1 year following aCXL, the researchers measured Scheimpflug-derived corneal densitometry, CDVA, maximum keratometry (K_max), and central corneal thickness and they estimated postoperative haze with SLE.  

Among the study cohort, 464 eyes (96.1%) had progressive keratoconus, 10 eyes (2.1%) had LASIK-induced ectasia, and 9 eyes (1.9%) had pellucid marginal degeneration (PMD). 

The researchers report that subjective haze with SLE is significantly associated with densitometry (P <.001). CDVA is significantly associated with densitometry in the 0 to 2 mm zone, where for every 10 grey scale units (GSUs) increase in densitometry, CDVA decreased by approximately half a Snellen line (P <.001).

Significant predictors of densitometry include age and preoperative K_max, according to the researchers.

For every 10 years of age, densitometry in the 0 to 2 mm zone increased by 0.68 GSUs (95% CI [0.27 to 1.07], P <.001) and densitometry in the 2 to 6 mm zone increased by 0.79 GSUs (95% CI [0.48 to 1.08], P <.001). For every 10 diopters of increased preoperative K_max, densitometry in the 0–2 mm zone increased by 0.69 GSUs (95% CI [0.41 to 0.98], P <.001) and in the 2–6 mm zone, preoperative K_max was not a significant predictor of densitometry (0.17 GSUs, 95% CI [−0.06 to 0.38], P =.158).

“In conclusion, this is the first study to quantify the relationship between subjective haze assessed with SLE to objective haze measured with corneal densitometry after aCXL. This strong association between the two techniques provides new information for clinicians who wish to objectively document haze in their aCXL patients,” according to the researchers. “As it may take more than a year for corneal densitometry values to return to preoperative values, clinicians should counsel their patients that the haze they experience initially will likely decrease over time, and that any reduced vision resulting from haze may take over a year to improve as corneal haze dissipates.”

Study limitations include the overrepresentation of patients with progressive keratoconus in the study population and the relatively short follow-up period (1 year).