Keratoconus and Visual Performance with Different Contact Lenses

Figures & data

Table 1 Demographic Data

	RGPCL (n = 67)	HCL (n = 17)	HGCL (n = 12)	p-value
Age, years (mean±SD)	42.2±12.7	40.7±14.9	47.1±9.3	0.382
Gender (%)
Male	61.2% (41/67)	88.2% (15/17)	50.0% (6/12)	0.875
Female	38.8% (26/67)	11.8% (2/17)	50.0% (6/12)
Previous ocular surgery (%)
ICRS	14.9% (10/67)	11.8% (2/17)	25% (3/12)	0.002
PK	7.5% (5/67)	17.6% (3/17)	25% (3/12)
DALK	0% (0/67)	0% (0/17)	16.7% (2/12)
Time of CL wear* (%)
≤5 years	46.3% (31/67)	41.2% (7/17)	58.3% (7/12)	0.382
5–10 years	16.4% (11/67)	11.8% (2/17)	33.3% (4/12)
≥10 years	37.3% (25/67)	47.1% (8/17)	8.3% (1/12)
SE, diopters (mean±SD)	−6.4±4.8	−3.7±3.0	−5.9±3.4	0.078

Notes: *Refers to the current CL fitted in this study. Bold number represents a statistically significant p-value.

Abbreviations: CL, contact lens; DALK, deep anterior lamellar keratoplasty; HCL, hybrid contact lens; HGCL, silicone hydrogel/hydrogel contact lens; ICRS, intra-stromal corneal ring segments; PK, penetrating keratoplasty; RGPCL, rigid gas permeable contact lens; SE, spherical equivalent.

Table 2 Functional and Structural Outcomes

		RGPCL (n = 67)	HCL (n = 17)	HGCL (n = 12)	p-value
Functional Analysis	BCVA
	BCVA-S, decimal	0.4±0.2	0.4±0.3	0.5±0.2	0.199
	BCVA-CL,decimal	0.9±0.2	0.9±0.2	0.8±0.1	0.618
	Contrast sensitivity
	Mean PCS, dB	19.3±2.6	20.6±2.8	17.3±2.7	0.006
	Mean MCS, dB	13.9±3.7	15.4±2.8	12.8±2.7	0.121
	Analysis of light scattering in the retina
	OSI	3.7±2.9	3.8±2.7	5.8±3.4	0.134
	PVA100, decimal	0.6±0.3	0.5±0.2	0.4±0.3	0.131
	PVA20, decimal	0.4±0.2	0.3±0.2	0.3±0.2	0.120
	PVA9, decimal	0.2±0.1	0.2±0.1	0.2±0.1	0.054
	MTF, c/deg	17.1±8.6	14.3±6.8	12.0±8.4	0.105
	Pupil size, mm	4.3±2.1	3.2±2.3	4.4±2.5	0.161
	Impact of tear film on dynamic optical quality
	VBUT, sec	2.1±2.6	2.1±2.5	2.9±2.0	0.227
	dOSI	4.8±3.1	5.5±2.8	8.3±4.3	0.024
	maxOSI	6.6±4.2	8.1±5.1	10.1±4.8	0.040
	minOSI	3.7±2.9	3.9±2.3	6.5±3.7	0.037
	ampOSI	2.9±2.7	4.1±4.6	3.6±2.0	0.165
STRUCTURAL ANALYSIS	Corneal tomographic parameters
	minK, dioptre	48.6±6.1	46.2±3.9	43.8±5.2	0.034
	maxK, dioptre	52.4±5.5	51.6±3.7	49.1±4.8	0.294
	meanK, dioptre	50.4±5.7	48.6±3.6	44.0±7.6	0.020
	TP, µm	423.5±74.0	489.7±77.1	484.4±76.6	0.011
	BAD-D	11.7±5.4	7.1±3.9	7.7±4.5	0.013
	RMS-HOA, µm	3.7±1.6	3.2±1.7	3.0±1.7	0.372
	RMS-TOTAL, µm	11.6±4.3	11.0±3.8	10.0±5.8	0.601
	Posterior pole tomographic parameters
	CMT, µm	286.4±26.4	283.8±22.0	293.2±29.3	0.617
	SCT, µm	284.0±115.2	284.4±120.0	261.4±124.1	0.822
	OD-NFL, µm	98.6±13.2	96.2±18.0	98.4±10.5	0.818

Notes: Bold number represents a statistically significant p-value. Values represent mean ± standard deviation.

Abbreviations: ampOSI, OSI amplitude; BAD-D, Belin-Ambrósio deviation index; BCVA, best-corrected visual acuity, BCVA-CL, best-corrected visual acuity with contact lens, BCVA-S, best-corrected visual acuity with spectacles; CMT, central macular thickness; dOSI, OSI dynamically measured 40 times in a 20 second period as a surrogate of tear film stability; HCL, hybrid contact lens; HGCL, silicone hydrogel/hydrogel contact lens; MCS, contrast sensitivity under mesopic conditions; maxOSI, OSI maximum; minOSI, OSI minimum; MTF, modular transfer function; OD-NFL, optic disc nerve fiber layer thickness; OSI, objective scatter index; PCS, contrast sensitivity under photopic conditions; PVA100, predicted visual acuities (decimal) within the 100% contrast level; PVA20, predicted visual acuities (decimal) within the 20% contrast level; PVA9, predicted visual acuities (decimal) within the 9% contrast level; RGPCL, rigid gas permeable contact lens; RMS-HOA, root mean square higher-order aberration; RMS-TOTAL, root mean square total; SCT, subfoveal choroidal thickness; TP, corneal thickness at the thinnest point; VBUT, vision break-up time.

Table 3 OSI Correlations

		R value	p value
Demographic Parameters
Age		0.429	<0.001
Time of contact lens wear		0.249	0.017
Spherical equivalent		−0.392	<0.001
Strutural Parameters
Anterior	Maximum K	0.237	0.063
	BAD-D	0.164	0.207
	TP	−0.069	0.592
Posterior	CMT	0.161	0.121
	SCT	−0.470	<0.001
	OD-NFL	−0.185	0.074

Note: Bold number represents a statistically significant p-value.

Abbreviations: BAD-D, Belin-Ambrósio deviation index; CMT, central macular thickness; OD-NFL, optic disc nerve fiber layer thickness; SCT, subfoveal choroidal thickness; TP, corneal thickness at the thinnest point.

Figure 1 The variation of some variables according to different patients groups: rigid gas permeable contact lens (RGPCL), hybrid contact lens (HCL) and silicone hydrogel/hydrogel contact lens (HGCL). (A) Mean best-corrected visual acuity with spectacles (BCVA-S) (p = 0.199) and with contact lens (BCVA-CL) (p = 0.618). (B) Mean contrast sensitivity under photopic conditions (PCS) (p = 0.006) and mesopic conditions (MCS) (p = 0.121). (C) Mean predicted visual acuities within the 100% contrast level (PVA100) (p = 0.131), within the 20% contrast level (PVA20) (p = 0.120) and within the 9% contrast level (PVA9) (p = 0.054). (D) Mean dynamically measured OSI: minimum (MinOSI) (p = 0.037), mean (p = 0.024) and maximum (MaxOSI) (p = 0.040). (E) Mean k minimum (mink) (p = 0.034), mean (p = 0.020) and maximum (maxK) (p = 0.294). (F) Mean central macular thickness (CMT) (p = 0.617), subfoveal choroidal thickness (SCT) (p = 0.822) and optic disc nerve fiber layer thickness (OD-NFL) (p = 0.818).

Figure 2 Three clinical examples. They were chosen because they have a similar age, gender, and spherical equivalent, fitted with 3 different contact lenses. (A) Patient fitted with a rigid gas permeable contact lens (RGPCL). (B) Patient fitted with a hybrid contact lens (HCL). (C) Patient fitted with a silicone hydrogel/hydrogel contact lens (HGCL). In all these cases, it was an increased best-corrected visual acuity with contact lens, but the other visual quality parameters differed among groups. Along with the cases (A–C), objective scatter index, vision break-up time, and contrast sensitivity worsened, despite better corneal tomographic parameters.