Objective Quantification of Image Quality and Optical Scatter Before and After Nd:YAG Capsulotomy Using a Double-Pass Technique

Figures & data

Figure 1 The Visiometrics HD Analyzer (image courtesy of Keeler; Malvern, PA) measures the retinal point spread function via a double-pass method, providing an objective measure of forward light scatter and other metrics of visual quality.

Figure 2 The HD Analyzer uses an infrared laser and a double-pass image through asymmetric entrance and exit apertures captured with a charge-coupled device camera, allowing inference of the complete optical transfer function of the eye as well as the shape of the retinal point spread function.

Table 1 Visual Acuity Parameters with YAG Capsulotomy (1 Line Improvement in Acuity = −0.10 log MAR)

Visual Acuity (log MAR)	Pre-YAG	Post-YAG	Change (Post−Pre)	p value
HC-UCVA	+0.22 ± 0.23	+0.16 ± 0.20	−0.07 ± 0.17	0.049
HC-BCVA	+0.01 ± 0.15	−0.04 ± 0.07	−0.06 ± 0.11	0.021
LC-BCVA	+0.35 ± 0.17	+0.23 ± 0.11	−0.12 ± 0.18	0.001

Abbreviations: HC, high contrast; LC, low contrast; UCVA, uncorrected visual acuity; BCVA, best spectacle-corrected visual acuity.

Table 2 HD Analyzer Parameters Pre- and Post-YAG Capsulotomy

HD Analyzer Parameter	Pre-YAG	Post-YAG	Change (Post−Pre)	p value	Pearson of ∆parameter to ∆HC-BCVA	Pearson of ∆parameter to ∆LC-BCVA	Pearson of ∆parameter to PCO Grade
OSI	2.23 ± 2.64	0.88 ± 0.40	−1.35 ± 2.49	0.007	+0.78	+0.71	−0.44
MTF Cutoff	26.44 ± 11.92	37.25 ± 7.68	+10.81 ± 13.55	<0.001	−0.34	−0.54	+0.15
Strehl	0.14 ± 0.04	0.18 ± 0.04	+0.05 ± 0.05	<0.001	−0.29	−0.42	+0.18
Width @ 50%	6.09 ± 4.62	3.37 ± 0.85	−2.72 ± 4.67	0.004	+0.64	+0.54	−0.25
Width @ 10%	17.53 ± 10.96	12.33 ± 3.82	−5.20 ± 11.02	0.024	−0.08	−0.01	−0.10

Notes: Width, point spread function profile width at 10% (arc min) and 50% (arc min) of the maximum height; ∆, change (post−pre).

Abbreviations: PCO, posterior capsular opacity; OSI, Objective Scatter Index; MTF, Modulation TransferFunction.

Figure 3 Preoperative OSI for each subjective PCO grading. Preoperative OSI values were significantly lower for Grade 1 than for both Grade 2 (p=0.0392) and Grade 3 (p=0.0184) and approached statistical significance when comparing values between Group 2 and 3 (p=0.0782).

Table 3 Correlations (R²) Between Change in High and Low Contrast Visual Acuity and Objective and Subjective Metrics

	R^2 to ∆HC-BCVA	R^2 to ∆LC-BCVA
Pre-YAG OSI	0.61	0.49
∆OSI	0.60	0.49
Grade	0.19	0.16

Note: Δ, change (post−pre).

Abbreviations: HC-BCVA, high contrast best-corrected visual acuity; LC-BCVA, low contrast best-corrected visual acuity; OSI, Objective Scatter Index.