Eyeworld

EW GLAUCOMA 76 February 2016 by Matt Young and Gloria D. Gamat EyeWorld Contributing Writers they used percent IOP change as the outcome in univariate and multivar- iate analyses. "However, LP showed the great- est predictive value … compared to preoperative IOP, ACD, and PD ratio," they reported. "Although there was no statistically significant difference between the predictive coefficients of the predictors using Fisher's z transformation test, LP was thought to be a potentially stronger predic- tor in this group of patients," they explained. The researchers emphasized, however, that further studies with large sample sizes are needed to assess this relationship. The use of lens position (LP) as a predictor of IOP reduction after cataract surgery in non-glaucoma- tous patients with open angles poses several advantages, explained the investigating team: LP demonstrates great predictive value; in the ab- sence of AS-OCT scanning, LP may be a superior predictive parameter compared to other predictors such as angle opening distance, anterior chamber area, and lens vault, which can be measured only by AS-OCT; and to calculate IOL power, ocular biometry measurement is a require- ment pre-cataract surgery, and LP is a simple and convenient parameter that can easily be calculated. cataract surgery with IOL implan- tation lowers IOP by an average of 2.03 mm Hg, resulting in a 12.74% decrease from preoperative IOP in non-glaucomatous patients with open angles," reported Shan C. Lin, MD, director of the glaucoma ser- vice, Department of Ophthalmology, University of California, San Fran- cisco, and the study's corresponding investigator. "Lens position, computed by ACD and LT, is a parameter with predictive value for the amount of IOP reduction among non-glauco- matous patients with open angles," the investigators added. In this study, the investigators emphasized, preoperative IOP, axial length (AXL), ACD, and lens thick- ness (LT) were found to be associat- ed with percent IOP reduction after phacoemulsification, and the results were comparable to previous studies. "PD ratio was also shown to be an index with good predictive value for both absolute IOP change (fol- lowing previous studies) and percent IOP change as outcomes. We also found that the predictive value of LP for IOP reduction after phacoemul- sification cataract surgery was very useful in non-glaucomatous patients with open angles," they reported. The researchers found that pre- operative IOP, ACD, PD ratio, and LP are parameters with good predict- ability (all with P values <0.05), but surgery, the procedure is currently not usually included in the treat- ment armamentarium for open-an- gle glaucoma. Over the years, experts on this subject matter have done a consid- erable amount of work in order to determine preoperative factors that would predict the level of IOP reduc- tion after cataract surgery. Various parameters have already been investigated, including preop- erative IOP, anterior chamber depth (ACD), the ratio of preoperative IOP and ACD (pressure-to-depth ratio or PD ratio), and even measurements from anterior segment optical coher- ence tomography (AS-OCT). However, even though the lens is one of the few factors that can be modified to secondarily influence the anterior chamber (and hence the IOP), not much research work has been carried out to look into the re- lationship of lens parameters to IOP change post-cataract surgery. In an attempt to address this gap, Hsu and colleagues evaluated lens position (LP), relative lens posi- tion (RLP), and other variables that would predict IOP level reduction after cataract surgery in non-glau- comatous eyes with open angles. Their findings were reported in the December 2015 issue of Investigative Ophthalmology & Visual Science. "In this prospective study, we observed that phacoemulsification It may even help to reduce the impact of diurnal variation in IOP research and analysis R outine cataract surgery comes with various pres- sure-related implications. For example, in eyes with and without ocular hypertension or glaucomatous dis- ease, sustained intraocular pressure (IOP) reduction has been observed after routine phacoemulsification. In addition, compared to those with primary open-angle disease, there is a greater level of IOP low- ering effect after cataract surgery in patients with secondary and narrow- angle glaucoma. In eyes with narrow-angle glau- coma, the level of IOP lowering after cataract surgery is proportional to the resultant widening of the angle, making experts believe that patients with the narrowest angles before the surgery may benefit most from cata- ract extraction as a single procedure. Further, although the mecha- nism remains unclear and the mag- nitude of the effect is highly variable and unpredictable, an IOP lowering effect has been found in patients with open-angle glaucoma. How- ever, because it is still difficult to determine exactly which open-angle patients will benefit from cataract Cataractous lens position may predict IOP reduction levels after cataract surgery A glaucoma patient post laser peripheral iridotomy who presents for a cataract evaluation with a very narrow angle and severe posterior synechiae 360 degrees A patient with anterior segment dysgenesis syndrome Source: Robert Weinstock, MD

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