Table 1. Descriptive statistics and results of paired t-test conducted on mean±standard deviation (range) values obtained from 21 eyes with low-grade-moderate keratoconus pre-operatively (baseline), post-intracorneal ring segment implantation (1st step), and subsequent same-day topography-guided photorefractive keratectomy & corneal collagen cross linking (2nd step).
| Outcomes | Baseline | Post-1st step | 1P | Pre-2nd step | Post-2nd step | 2P | 3P |
| UDVA (logMAR) | 0.66±0.41 (0.05 to 1.30) | 0.31±0.18 (0.00 to 0.70) | 0.01 | 0.28±0.37 (0.00 to 1.00) | 0.20±0.25 (0.00 to 1.00) | 0.17 | 0.01 |
| CDVA (logMAR) | 0.21±0.22 (-0.10 to 0.70) | 0.28±0.73 (0.00 to 1.00) | >0.05 | 0.28±0.73 (0.00 to 1.00) | 0.03±0.04 (0.00 to 0.15) | 0.10 | 0.03 |
| Ksteep (D) | 48.44±3.66 (42.40 to 54.42) | 45.98±2.53 (43.42 to 51.30) | <0.0001 | 44.18±2.90 (40.66 to 50.58) | 43.71±1.95 (39.59 to 46.68) | 0.0007 | <0.05 |
| Kflat (D) | 45.61±2.40 (41.74 to 50.27) | 44.18±2.90 (40.66 to 50.58) | 0.0003 | 45.98±2.50 (43.54 to 51.30) | 41.56±2.05 (37.90 to 45.90) | 0.0005 | <0.05 |
| Kaverage (D) | 47.00±2.66 (41.57 to 52.35) | 45.01±2.34 (42.21 to 50.80) | 0.0001 | 47.00±2.66 (41.57 to 52.35) | 42.42±2.07 (39.18 to 46.29) | 0.0001 | <0.05 |
| Sphere (D) | -3.10±2.99 (-9 to +3) | -1.33±1.51 (-3.25 to +0.5) | 0.004 | -1.67±1.97 (-5.75 to +1.50) | -0.11±0.93 (-2.75 to 1.50) | 0.02 | <0.05 |
| Cylinder (D) | -3.68±1.53 (-6.0 to -1.25) | -1.81±1.49 (-0.5 to -6.0) | <0.0001 | -2.10±1.45 (-6.0 to -0.50) | -1.11±0.75 (-3.00 to 0.00) | 0.02 | <0.05 |
| Coma (µm) | 2.13±1.25 (1.40 to 4.54) | 1.65±0.97 (0.50 to 3.86) | >0.05 | 1.57±0.68 (0.70 to 2.90) | 1.58±0.75 (0.68 to 2.97) | >0.14 | >0.05 |
| CCT (µm) | 496.94±31.39 (443 to 565) | 492.90±15.02 (477 to 521) | 0.38 | 492.90±15.02 (477 to 521) | 469.82±33.60 (425 to 526) | 0.29 | 0.27 |
1,2,3P values of post-hoc analysis 1st step versus baseline, 1st step versus 2nd step, baseline versus 2nd step respectively. UDVA: Uncorrected distance visual acuity in logMAR; CDVA: Corrected distance visual acuity in logMAR; CCT: Central corneal thickness; D: Diopter; 1st step: Intrastromal corneal ring implantation; 2nd step: Topography-guided photorefractive keratectomy and collagen cross linking.