The Effect Of Tear Film Stability On Variability Of Posterior Corneal Curvature Readings Obtained With An Ss-Biometer In Cataract Patients.

To investigate the IOLMaster 700 variability of posterior curvature readings (PR) in relation to ocular surface parameters.

Clinical Ophthalmology Center SPEKTRUM, Wroclaw, Poland

Eligible cataract patients underwent two consecutive IOLMaster700 exams and ocular surface assessments by means of  SPEED questionnaire, non-invasive tear film break-up time (NIK-BUT first and average), fluorescein break-up time (FBUT), Oxford ocular surface staining, LIPCOFF and ocular hyperemia evaluation during one preoperative visit. Only quality check green indicator exams were included. The outcome measures were anterior (ΔK) and posterior astigmatism (ΔPK) in D and IOLMaster 700 composite SD in μm for mean, flat and steep corneal radii readings for anterior and posterior corneal surface (R_SD, R1_SD, R2_SD, PR_SD, PR1_SD, PR2_SD). Subgroup analysis evaluated the effect of BUT on repeatability of trimmed-mean ΔK and ΔPK vectors.

100 eyes of 67 patients were evaluated. The mean composite SD values were 2.55 μm, 3.82 μm, 3.96 μm for R SD, R1 SD and R2 SD, and 34.49 μm, 47.00 μm and 45.32 μm for PR SD, PR1 SD and PR2 SD, respectively (p<.001, t-test). The mean PR_SD showed no correlation with ocular surface assessments, but it was positively correlated with patient’s age (ρ=0.26, p=.007). The mean ΔK_SD was negatively correlated with NIKBUT average (ρ=-0.26, p<.008), the mean R_SD was negatively correlated with FBUT (ρ=-0.29, p<.003). No statistically significant differences for repeat measurements were noted for trimmed vectors ΔPK and ΔK in eyes with long or short BUT.

The OCT-based posterior curvature readings exhibit greater variability than the telecentric anterior keratometry. Unlike anterior corneal measurements, posterior corneal readings variability was not correlated with tear film parameters but increased with the patient’s age.