Differences in central and non-central keratoconus, and their effect on the objective screening thresholds for keratoconus

被引:15
作者
Prakash, Gaurav [1 ]
Srivastava, Dhruv [1 ]
Choudhuri, Sounak [1 ]
Thirumalai, Sandeep Mark [1 ]
Bacero, Ruthchel [1 ]
机构
[1] New Med Ctr Specialty Hosp, NMC Eye Care, Dept Cornea & Refract Surg, Elect St,POB 6222, Abu Dhabi, U Arab Emirates
关键词
keratconus; pachymetry; referral guidelines; senstivity; topography; wavefront; COLLAGEN CROSS-LINKING; QUALITY-OF-LIFE; PHOTOREFRACTIVE KERATECTOMY; CONE LOCATION; CORNEAL; VIDEOKERATOGRAPHY; ABERRATIONS; TOMOGRAPHY; OUTCOMES; SIZE;
D O I
10.1111/aos.12899
中图分类号
R77 [眼科学];
学科分类号
100212 ;
摘要
Purpose: To evaluate the differences in central and non-central keratoconus (based on cone location), and their effect on the objective screening thresholds for keratoconus. Methods: This comparative case series was performed at tertiary care cornea and refractive surgery service. Three groups were made: KC apex within central 2 mm (central keratoconus, n = 50), apex outside central 2mm (non-central keratoconus, n = 50) and normal controls (n = 100, with 50 cases each with apex within and outside central 2 mm). All cases underwent clinical evaluation and corneal topography (CSO, Sirius, Italy). Apex keratometry (ApexK), simulated keratometry at 3 mm (SimK), central corneal thickness (CCT) and minimum corneal thickness (MCT), anterior corneal higher-order aberrations root mean square (HOARMS), and Zernike's coefficients up to fourth order at different zones were measured. Results: In spite of the keratoconic groups having comparable ApexK (p > 0.05), central keratoconus had higher SimK and thinner CCT and MCT (p < 0.001). HOARMS was significantly more for central keratoconus at 3 mm zones. These findings had moderate to large effect size (Cohen's d). Receiver operating curve analysis was carried out to compare central keratoconus and non-central keratoconus with control group. ApexK and HOARMS had best discriminative parameters. Using single parametric suspicion cut-offs of 'either SimK steep > 47.2 D or CCT < 491.6 mu' had a good sensitivity (0.98) for central keratoconus, but not for non-central keratoconus (0.80). Changing this cut-off to 'either SimK steep K >= 45.8 D or CCT <= 503 mu' gave a sensitivity and specificity of 0.95 and 0.87 for non-central keratoconus and 0.99 and 0.87 for central keratoconus. Conclusion: Non-central keratoconus has lesser effect on SimK, pachymetry and smaller-aperture HOARMS. Using 'SimK steep > 47.2 D or CCT < 491.6 mu' may miss timely referral for topography in many of these cases. Using more stringent criteria of SimK steep K >= 45.8 D or CCT <= 503 mu to get a corneal topography done to rule out keratoconus is recommended, especially in cohorts with higher risk.
引用
收藏
页码:E118 / E129
页数:12
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