Corneal Densitometry to Assess the Corneal Cystine Deposits in Patients With Cystinosis

Abstract

Purpose:The purpose of this study was to assess the suitability of corneal densitometry measurements obtained with Scheimpflug imaging in estimating the corneal changes caused by cystine deposits in the cornea in patients with cystinosis.Methods:Scheimpflug imaging (Pentacam) was performed for 14 patients with cystinosis and 16 age-matched controls. Pentacam data were used for analysis of the corneal densitometry at different zones in the cornea for patients with cystinosis and controls. Densitometry measurements were compared with the corneal crystal scores obtained from the slitlamp images for patients with cystinosis.Results:There was no statistically significant difference in keratometry measurements between the 2 groups (P > 0.05). Corneal thickness was found to be significantly higher in the control group when compared with the cystinosis group (P = 0.0004). The mean corneal densitometry was significantly higher in patients with cystinosis when compared with controls at most of the corneal layers and zones. The corneal densitometry readings for the right and left eyes showed moderate positive correlation with the corneal crystal score with a ceiling effect being reached at the maximum corneal crystal score of 3.Conclusions:Corneal densitometry obtained through Pentacam can be used as an objective estimate of the level of cystine crystals present in patients with cystinosis. The clinical estimate of corneal crystal score, although effective at low levels of crystal deposition, does not allow for accurate estimates of change when the level of crystal deposition is high leading to limited utility when assessing treatment effects. Hence, densitometry measurements can potentially be used to assess treatment efficacy of cystinosis treatments in clinical settings.

Comparison of Scheimpflug Corneal Tomography and Anterior Segment Optical Coherence Tomography Measurements in Corneal Cystinosis: A Case Series

“…17,33,34 Furthermore, the average CD in healthy eyes, measured using AS-OCT, is documented to be 33.4 GSU (converted of a 256-level scale to a 100-level scale). 25 Consistent with expectations and findings of Biswas et al, 18 the CD values of the patients in the current work were higher than the normative mean. However, as shown in Table 2, the obtained CD readings from Pentacam HR in the current work are not of sufficient quality, and corresponding results need to be taken with caution.…”

“…Accurate biometric measurements of the anterior segment, including depth of crystal deposition (DCD) and CCT, are essential for the diagnosis of patients with cystinosis and can be used as a parameter for the disease progression and response to treatment. 18 However, the clinician depends on reliable and reproducible measurements for these corneal tomographic parameters. Some previous studies have analyzed CCT and/or DCD using AS-OCT. 30,31 Labbé et al 10 compared these parameters in patients with nephropathic cystinosis, measured by AS-OCT and IVCM.…”

“…Densitometry measurements acquired through ST offer an objective assessment of cystine crystal levels in corneal cystinosis patients. 18 Anterior segment optical coherence tomography (AS-OCT) (CASIA2; Tomey Corporation, Japan) is a new swept-source OCT designed for high-resolution imaging of the anterior eye segment. Using a wavelength of 1,310 nm, AS-OCT achieves a rapid A-scan speed of 50,000 scans per second, producing up to 128 radial images within 0.3 s 19 This efficiency makes AS-OCT suitable for obtaining clear images in pediatric patients.…”

“…Densitometry measurements acquired through ST offer an objective assessment of cystine crystal levels in corneal cystinosis patients. 18…”

“…16,20 In addition, AS-OCT can identify and quantify corneal cystine crystal deposition through a semiautomated image segmentation algorithm. 21 It is important to acknowledge that most of the prior investigations concerning CD have used ST for corneal analysis, 18 while the utilization of AS-OCT remains limited. [22][23][24] One study found a mean CD value of 85.6 GSU (mean of anterior central 2 mm in diameter and full corneal thickness), expressed as GSU range from 0 to 255.…”