Effect of Corneal Cone Location on Corneal Curvature Changes and Uncorrected Distance Visual Acuity after Corneal Collagen Cross-Linking for Progressive Keratoconus: A one-year Survey

Sattar Rajabi^1*, Seyyed Mehdi Tabatabaee², Mohammad Aghazadeh Amiri³, Ahmad Salamat Rad⁴ and Mohammad Yavari⁵

1Master of Optometry, Melli Bank Hospital, Tehran, Iran. ²PhD in Biostatistics, faculty member of Rehabilitation Sciences College, Shahid Beheshti University of Medical Sciences, Tehran, Iran. ³OD of Optometry, head of optometry group and faculty member of Rehabilitation Sciences College, Shahid Beheshti University of Medical Sciences, Tehran, Iran. ⁴Ophthalmologist, Farabi Hospital, Tehran University of Medical Sciences, Tehran, Iran. ⁵Ophthalmologist, Melli Bank Hospital, Tehran, Iran.

DOI : http://dx.doi.org/10.13005/bbra/1990

ABSTRACT: To assess the effect of corneal cone location on”corneal curvature Changes and Uncorrected Distance Visual Acuity (UDVA) after corneal collagen cross-linking for progressive keratoconus. This was a descriptive and analytical study conducted on 38 eyes of 27 patients aged 15-25 years, who underwent corneal cross-linking (CXL) on progressive keratoconus. Based on the location of preoperative maximum keratometry (Kmax) set by pentacam device, the patients were divided into two groups: The central and paracentral cone groups with corneal cone location of d” 3 mm and > 3 mm, respectively. The levels of uncorrected distance visual acuity and front surface curvature of the cornea of the patients were determined before and one year after surgery using a sagittal pentacam map and then compared. The UDVA significantly improved in the central cone group (-0.14 ± 0.26Log MAR (P=0.009). Similarly, the mean differences of Ks, Kf, and Kmean were statistically significant in this group (0.83±1.14D, 0.82±1.15D, and 0.84± 1.07D) (P=0.001). However, the Kmax did not show a significant difference (0.30± 1.85D (P=0.382). However, none of the variables showed a significant change in the paracentral cone group. The changes of UDVA, Ks, Kf, Kmean, and Kmax were respectively 0.001 ± 0.19 LogMAR (P = 0.001), 0.50 ± 0.92D (P=0.143), 0.67 ± 1.54D (P=0.225), 0.79 ± 1.10D (P=0.167), and -0.06 ±0.67D (P=775) in the paracentral group. None of the variables showed significant difference between the two groups. After performing CXL for progressive keratoconus, more corneal curvature flattening and improvement in UDVA occurred in eyes with centrally located cones.

KEYWORDS: Cone location; Corneal Curvature; Progressive Keratoconus; Corneal Cross-linking; Uncorrected Distance Visual Acuity

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