Corneal Ectasia Risk And Percentage Tissue Altered In Myopic Patients Presenting For Refractive Surgery

Figures & data

Table 1 Pre-Operative Patient Demographics Of All Eyes In Study Who Subsequently Underwent Small Incision Lenticule Extraction (SMILE) Or Laser-assisted sub-epithelial keratectomy (LASEK)

Variables	Total Eyes	SMILE*	LASEK	p-value^II
Number (%)	114 (100%) of 66 patients	94 (82.5%) of 56 patients	20 (17.5%) of 10 patients
Age (years) (mean [M] ± standard deviation [SD], range [R])	30.0 ± 7.0	30.7 ± 7.3	27.1 ± 4.2	0.278^†‡
	21.0 to 53.1	21.0 to 53.1	22.4 to 33.4
Male gender (n, %)	35 (53.0%)	28 (50.0%)	7 (70.0%)	0.226^†§
Central corneal thickness (M ± SD, R)	541.1 ± 39.1,	553.6 ± 28.9,	482.25 ± 24.4,	<0.0001^†‡
	437 to 646	504 to 646	467 to 528
Sphere (D) (M ± SD, R)	−5.42 ± 2.06,	−5.47 ± 2.15,	−5.20 ± 1.55,	0.748^†‡
	0.00 to −9.50	0.00 to −9.50	−3.00 to −7.75
Cylinder (D) (M ± SD, R)	1.00 ± 0.65,	1.00 ± 0.69,	0.99 ± 0.46,	0.467^†‡
	0.00 to 3.50	0.00 to 3.50	0.00 to 2.00
Spherical equivalent (D) (M ± SD, R)	−5.71 ± 2.07,	−5.76 ± 2.17,	−5.47 ± 1.52,	0.883^†‡
	−1.25 to −10.00	−0.75 to −9.75	−3.00 to −7.63
Percentage tissue altered (PTA)
LASIK-100 (M ± SD, R)	33.7 ± 6.0,	32.7 ± 5.8,	38.1 ± 5.4,	<0.0001^‡
	17.2 to 46.9	17.2 to 44.2	30.3 to 46.9
LASIK-110 (M ± SD, R)	35.5 ± 6.1,	34.5 ± 5.8,	40.1 ± 5.5,	<0.0001^‡
	18.7 to 49.2	18.7 to 46.1	32.2 to 49.2
LASIK-120 (M ± SD, R)	37.4 ± 6.2,	36.3 ± 5.8,	42.2 ± 5.5,	<0.0001^‡
	20.3 to 51.5	20.3 to 47.9	34.1 to 51.5

Notes: *31 eyes had 3-year followup data. ^IIComparing SMILE and LASEK eyes. ^†Comparing SMILE and LASEK eyes with 3-year follow-up data. ^‡Paired sample t-test. ^§Chi-square test.

Abbreviations: D, dioptres; LASIK-100, PTA based on flap thicknesses of 100 μm; LASIK-110, PTA based on flap thicknesses of 110 μm; LASIK-120, PTA based on flap thicknesses of 120 μm.

Table 2 Pre-Operative And 3 Months Post-Operative Patient Demographics In Eyes Undergoing SMILE Procedures (n = 94) And LASEK Procedures (n = 20) For Treatment Of Myopia

	SMILE			LASEK
Variables	Pre-Operative	3 Months Post-Operative	p-value	Pre-Operative	3 Months Post-Operative	p-value
Sphere (D)
Mean ± SD	−5.47 ± 2.15	0.243 ± 0.45	<0.0001*	−5.20 ± 1.55	0.38 ± 0.30	<0.0001*
Range	0.00 to −9.50	−1.25 to 1.00		−3.0 to −7.75	0.00 to 1.00
Cylinder (D)
Mean ± SD	1.00 ± 0.69	0.30 ± 0.27	<0.0001*	0.99 ± 0.46	0.19 ± 0.23	0.001*
Range	0.00 to 3.50	0.00 to 1.00		0.00 to −2.00	0.00 to −0.50
Spherical equivalent (D)
Mean ± SD	−5.76 ± 2.17	0.08 ± 0.47	<0.0001*	−5.47 ± 1.52	0.28 ± 0.34	<0.0001*
Range	−0.75 to −9.75	−1.50 to 0.75		−3.00 to −7.63	−0.25 to 1.00
UDVA (LogMAR)
Mean ± SD	1.57 ± 0.37	0.04 ± 0.10	<0.0001*	1.45 ± 0.42	0.02 ± 0.40	<0.0001*
Range	0.40 to 1.85	−0.15 to 0.40		0.54 to 1.85	0.00 to 0.10
CDVA (LogMAR)
Mean ± SD	−0.01 ± 0.03	−0.04 ± 0.07	0.001*	0.0± 0.00	−0.25 ± 0.05	0.168*
Range	−0.15 to 0.10	−0.15 to 0.10		0.00 to 0.00	−0.12 to 0.00

Note: *Paired sample t-test (corrected for correlation between eyes from same subjects).

Abbreviations: SD, standard deviation; D, dioptres; UDVA, uncorrected distance visual acuity; CDVA, corrected distance visual acuity.

Figure 1 Percentage tissue altered (PTA) of eyes in study had laser in-situ keratomileusis (LASIK) been performed; these eyes subsequently underwent small incision lenticule extraction (SMILE) or laser-assisted sub-epithelial keratectomy (LASEK) procedures. (A) Scatter plot of PTA based on a LASIK flap thickness of 120μm highlighting patients with 36 months follow-up showing a significant proportion of eyes having PTA ≥40%; (B) bar chart showing the proportion of patients in the study with PTA above fixed thresholds of 30%, 40%, and 45% assuming different LASIK flap thicknesses.

Figure 2 Refractive outcomes of eyes that underwent SMILE procedures. (A) Cumulative percentage of eyes in which the target refraction was zero that attained the specified levels of uncorrected distance visual acuity (UDVA) 3 months after surgery. CDVA = corrected distance visual acuity; (B) cumulative percentage of eyes in which the target refraction was zero that attained the specified levels of UDVA 3 years after surgery; (C) percentage of eyes with post-operative spherical equivalent refractions within intended target spherical equivalent refraction; (D) scatter plot and linear regression analysis of the attempted spherical equivalent refractive change versus the achieved spherical equivalent refractive change at 3 months after surgery; (E) stability of post-operative spherical equivalent at 3 years after surgery; (F) percentage of eyes in which there was a gain or loss of lines in CDVA 3 months and 3 years after surgery.