Eyeworld

EW RESIDENTS 108 March 2016 by Tiffany Liu, MD, and Alexander Nguyen, MD, Yale School of Medicine F or evaluating patients with complaints of decreased vision, a demonstrable change in best corrected visual acuity (BCVA) is a simple and widely recognized means of quantifying visual deterioration. As we have developed the means to characterize and quantify high- er-order aberrations (HOAs), our assessment of visual function has become increasingly sophisticated. When we consider how higher-or- der spherical aberrations, coma and trefoil may impact a patient's vision, we may be able to appreciate how someone who demonstrates a largely unremarkable change in Snellen acuity can truly have poor vision quality. Such issues reinforce the What diagnostic tests better assess the loss of visual quality with milder cataract or secondary membrane, which is often underestimated by Snellen acuity? This month, I invited the Yale residents to review 2 related papers on this topic from the current JCRS issue. –David F. Chang, MD, EyeWorld journal club editor need for objective methods that can estimate visual deterioration. For reasons pertaining to reproducibility, such methods would be minimally dependent on patient and clinician interpretation. Faria-Correia et al. discuss in their recent article how quantifying lens opacities with densitometry and higher-order aberrations may aid in the evaluation of mild nuclear sclerotic cataracts. Currently, the most widely recognized lens grading system is the Lens Opacities Clas- sification III (LOCS III), which was last updated in 1993. 1 It comprises a series of exemplary photographs demonstrating cataracts of varying grades. Despite its longstanding utility, this grading system relies on clinician interpretation, which can be expected to have some amount of inter-rater variability. Being able to objectively quantify lens opaci- fication is an attractive goal that is being increasingly explored by various authors. But merely quanti- fying lens opacification is, of course, not as preferable as being able to discern if the opacities are of visual significance, which is the aim of the foregoing article. In their retrospective study, Faria-Correia et al sought to compare lens opacities graded by the LOCS III correlated with lens densitome- try measurements and aberrations obtained from wavefront analyses. They used a Scheimpflug- based de- vice (Pentacam HR, Oculus, Wetzlar, Germany) to estimate the densitom- etry of the crystalline lens. Wave- front analyses were accomplished using the i-Trace (Tracey Technolo- gies, Houston), which integrates an aberrometer with corneal topog- raphy. The machine can estimate aberrations produced by the entire eye; by subtracting the aberrations that may be attributed to the cornea (from topographic data), the inter- nal aberrations can be calculated. The authors specifically investigated lenses with mild nuclear sclerosis, excluding eyes with a LOCS III nu- clear grade of 4.0 and above. The study analysis included 40 eyes of 30 patients. The Pentacam can be equipped with software that, based on lens densitometry measurements, can assign a grade of nuclear sclerosis (Pentacam Nu- clear Staging or PNS) on a scale of 1–5. The authors found that BCVA correlated well with the LOCS III grade (rho=0.339, P=0.34) and the PNS score (rho=0.453, P=0.005). This validates the concept that an auto- mated estimate of nuclear sclerosis can provide comparable information to a clinician's evaluation of the lens. 2 Of the various lens densito- metric parameters measured, BCVA was more strongly correlated with average density (r=0.744, P<0.001) than maximum density (r=0.408, P=0.003). When the wavefront analyses were compared to densitometry measurements, the internal root mean square (RMS) HOAs were pos- itively correlated with both average lens density (rho=0.661, P<0.001) and maximum density (rho=0.570, P<0.001). Regarding individual HOAs, only trefoil was noted to have a significant correlation with average density (r=0.657, P<0.001). On the other hand, both trefoil and coma were positively correlated with max- imum density (r=0.649, P<0.001; r=0.536, P=0.001). Data from the wavefront analyses corroborate pre- vious works that associate nuclear sclerosis with an increase in HOAs. 3,4 Specifically, coma and trefoil were the predominant HOAs that appear to be increased in this setting. Importantly, Faria-Correia et al were the first to demonstrate that nuclear sclerosis as measured by densitometry is correlated with HOAs. The utility of such a relation- ship would be most apparent in the evaluation of a patient with a mild but visually significant nuclear scle- rotic cataract. In this circumstance, the definition of "visually signifi- cant" becomes key. The patient may demonstrate a Snellen visual acuity of 20/25 or 20/30 but insist that his or her vision is poor. If we were to perhaps quantify their HOAs with an aberrometer, the cause of poor vision may be more evident. As of now, patients with mild cataracts who complain of poor vision represent a growing popula- tion with an unmet need. These are the patients that, by conventional standards, may not technically meet the criteria of having a "visually Review of "Scheimpflug lens densitometry and ocular wavefront aberrations in patients Scheimpflug lens densitometry and ocular wavefront aberrations in patients with mild nuclear cataract Fernando Faria-Correia, MD, Bernardo Lopes, MD, Tiago Monteiro, MD, Nuno Franqueira, MD, Renato Ambrósio Jr., MD, PhD J Cataract Refract Surg (March) 2016;42. Article in press Purpose: To test correlations between Scheimpflug optical densitometry and ocular high-order aberrations (HOAs) in patients with mild nuclear cataract. Setting: Cornea and Refractive Surgery Department, Hospital de Braga, Braga, Portugal. Design: Retrospective single-center study. Methods: Forty eyes of 30 patients with mild nuclear cataract were included in this study. Lens densitometry was evaluated by Scheimpflug imaging (Pentacam HR, Oculus, Wetzlar, Germany), which provided an objective quantification (average density and maximum density) and grading (Pentacam Nuclear Staging score) of the crystalline lens. A visual function analyzer (i-Trace, Tracey Technologies, Houston) that combines ray tracing aberrometry and Placido disk-based topography was used to evaluate the total ocular and internal HOAs. Results: The mean average density of the lens nucleus was 8.99%±0.76 (range 7.5 to 10.8) and the mean maximum density was 27.96%±6.97 (range 16.9 to 56.1). Regarding the Pentacam Nuclear Staging (PNS) score, 28 eyes had level 0 and 12 eyes had level 1. Significant positive correlations were found between the average density and maximum density parameters and the internal HOAs (rho=0.661, P<.001; rho=0.570, P<.001, respectively). Conclusions: There are significant correlations between the quantification parameters derived from Scheimpflug lens densitometry and ocular HOAs. The integration of these technologies can be helpful in clinical decision-making and in understanding the subjective symptoms of patients with mild nuclear cataracts. Jessica Chow, MD, residency program director, Yale School of Medicine EyeWorld journal club

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