Effect of posterior capsular opacification removal on automated perimetry

Does Posterior Capsule Opacification Affect the Results of Diagnostic Technologies to Evaluate the Retina and the Optic Disc?

The visual outcome obtained after cataract removal may progressively decline because of posterior capsular opacification (PCO). This condition can be treated by creating an opening in the posterior lens capsule by Nd:YAG laser capsulotomy. PCO optical imperfections cause several light reflection, refraction, and diffraction phenomena, which may interfere with the functional and structural tests performed in different ocular locations for the diagnosis and follow-up of ocular disease, like macular and optic nerve diseases. Some parameters measured by visual field examinations, scanning laser polarimetry, and optical coherence tomography (OCT) have changed after PCO removal. Imaging quality also changes following capsulotomy. Consequently, the results of ancillary tests in pseudophakic eyes for studying ocular diseases like glaucoma or maculopathies should be correlated with other clinical examinations, for example, slit-lamp biomicroscopy or funduscopy. If PCO is clinically significant, a new baseline should be set for future comparisons following capsulotomy when using automated perimetry and scanning laser polarimetry. To perform OCT in the presence of PCO, reliable examinations (considering signal strength) apparently guarantee that measurements are not influenced by PCO.

Effect of posterior capsular opacification removal on macular optical coherence tomography

PURPOSE

To evaluate the influence of posterior capsular opacification (PCO) on macular optical coherence tomography (OCT) imaging quality and measurements of macular retinal thickness.

METHODS

In this prospective interventional case series, 32 eyes of 23 patients with PCO were recruited. Best-corrected visual acuity (BCVA), a complete ophthalmologic assessment, and macular OCT scans (OCT Stratus 3000) before and after Nd:YAG capsulotomy were performed. Two parameters for image quality (signal strength (SS) and number of tomographic messages) and 10 macular retinal thickness measurements were compared. Spearman correlations between BCVA and SS and macular retinal thickness measurements before and after capsulotomy were also performed.

RESULTS

PCO removal was associated with an increase of best-corrected visual acuity (p<0.0001). The mean SS (n=32) went from 3.34+/-2.31 to 6.38+/-1.93 (p<0.0001) after Nd:YAG capsulotomy. The SS improved in 26 of 32 eyes. No significant difference between mean preoperative and postoperative macular retinal thickness measurements was observed (p<0.05) in valuable scans. Before capsulotomy, a correlation existed between BCVA and SS. After capsulotomy this correlation was no longer found.

CONCLUSIONS

OCT image quality is influenced by PCO. Nd:YAG capsulotomy results in a measurable improvement in SS and improvement in the number of valuable examinations. Valuable OCT scans in patients with PCO seem to yield reliable measurements of macular retinal thickness even in the presence of severe PCO. The correlation between BCVA and SS before capsulotomy suggests that the SS could be considered an objective indicator of the degree of PCO.

Effect of posterior capsular opacification removal on scanning laser polarimetry measurements

PURPOSE

To evaluate the effect of posterior capsular opacification (PCO) on retinal nerve fiber layer (RNFL) retardation measurements obtained during scanning laser polarimetry (SLP). We are unaware of previous studies undertaken in this sense.

METHODS

SLP was performed using GDx variable corneal compensation (VCC) on 28 eyes of 28 non-glaucomatous patients with clinically significant PCO, previous uneventful cataract surgery and no other ocular pathology, both before and after Nd:YAG capsulotomy. Best-corrected visual acuity (BCVA), intraocular pressure (IOP) and SLP examination parameters prior and following PCO removal were compared using the Student t-test and Wilcoxon's test. Spearman correlations between BCVA and SLP measurements before and after capsulotomy were also performed.

RESULTS

PCO removal was associated with an increase of BCVA (P<0.0001), nerve fiber indicator (NFI) (P<0.0001) and typical scan score (TSS) (P<0.0001). In parallel, significant decreases of all absolute parameters were observed after capsulotomy. IOP, symmetry, superior ratio, inferior ratio and temporal-superior-nasal-inferior-temporal (TSNIT) standard deviation (SD) revealed no changes. Before capsulotomy, marked correlation existed between the BCVA and some SLP measurements such as nasal average (r= -0.703; P<0.0001) or NFI (r= 0.564; P=0.0017). After PCO removal these correlations were no longer found.

CONCLUSIONS

PCO removal changes SLP measurements. Therefore, new measurements to serve as a baseline for future comparisons should be obtained after Nd:YAG capsulotomy. Furthermore, some SLP measurements were significantly associated with BCVA before capsulotomy, suggesting that this technology may be useful to quantify PCO degree in non-glaucomatous patients.