EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/78710
May 2012 EW RESIDENTS "Long-term effect of phacoemulsification on fellow eye as control" Study* Ge, 2001 Poley, 2009 Euswas, 2005 Hayashi, 2000 Poley, 2009 Hayashi, 2000 Lai, 2006 Poley, 2009 Shingleton, 1999, 2006 Chang, 20121 Mathalone, 2005 Tham, 2008 Poley, 2009 Chang, 20122 Chang, 20123 Poley, 2009 Glaucoma type ACG Adult CACG ACG Adult OAG PACG Adult OAG OAG/OHT OAG ACG Adult OAG/OHT OAG/OHT Adult Eyes (n) 47 17 48 73 23 73 21 28 55 15 58 25 33 29 14 23 Pre-op IOP (mm Hg) Final IOP (mm Hg) IOP change (mm Hg) 25.5 24.4 22.0 21.4 20.7 20.5 19.7 18.5 18.4 18.2 17.0 16.3 16.0 15.7 13.0 11.6 12.0 16.3 17.1 15.0 16.0 16.4 15.5 15.2 16.6 15.0 15.1 14.5 14.9 14.7 14.3 13.5 *First author and year of publication, complete information in citation list 1. Current study group with IOP above and including cohort median 2. Current study group cumulative result 3. Current study group with IOP below cohort median The methodology of IOP meas- urement and forms of tonometry employed for the different sites was not detailed. Understandably, read- ings would not have been masked or standardized in a retrospective study. In our own clinic, we have been disappointed to find that tonometers can be miscalibrated, observer bias exists, and IOP read- ings by different physicians during the same patient visit may differ by 1-2 mm Hg. The authors importantly identi- fied a potential problem with previ- ous studies in which very few IOP measurements were recorded. Specif- ically, for studies in which the num- ber of pre-op measurements was limited, they noted that regression to the mean might explain the de- creases in IOP following cataract ex- traction. They attempted to mitigate this phenomenon by including only patients with at least two pre-op IOP measurements. Despite their best efforts, they were hampered by the retrospective nature of the study. It is unclear how many patients had more than two pre-op IOP measure- ments or if two measurements could eliminate the problem of regression. The greater the variance in IOP read- ings, the greater the number of necessary measurements. With diurnal variation in IOP measurement, it is unlikely that two data points would be sufficient with- out controlling for time of recording and instillation of pressure-lowering drops; prospectively designed glau- coma studies typically require a min- imum of three recordings, measured at different times of day on separate occasions (Bhorade 2008, Shaarawy 2008). Despite these potential limi- tations, the current study results fit well with previously published data in which the magnitude of IOP-low- ering following phacoemulsification is proportional to the pre-op IOP level (see table). Specifically, the results demonstrate a trend toward greater IOP reduction in patients with higher initial IOP and minimal reduction, or even IOP increase, in patients with lower to normal initial IOP. In summary, the authors have highlighted the current uncertainty regarding the effect of cataract ex- traction on IOP. They uniquely uti- lized the fellow eye as the untreated control. The results may be consis- tent with previously published trends but underscore the need for further investigation. A similar, prospective study using the fellow eye as the control would suffer from the same limits to enrollment. Their findings reinforce the need for large, prospective studies with multiple, standardized IOP measurements, clearly defined patient populations, and planned IOP stratification. Such studies, coupled with an improved understanding of the pathophysiol- ogy of IOP-lowering after pha- coemulsification, are necessary to identify the subsets of patients best served by either simple cataract extraction or a combined cataract and glaucoma surgical procedure. EW References Bhorade AM, Gordon MO, Wilson B, Kass MA. Variability of intraocular pressure measure- ments in observation participants in the ocular hypertension treatment study. Ophthalmology 2009; 116(4): 717-724. Chang TC, Budenz, BL, Liu A, Kim WI, Dang T, Li C, Iwach AG, Radhadkrishnan S, Singh K. Long-term effect of phacoemulsification on in- traocular pressure using phakic fellow eye as control. J Cataract Refract Surg 2012; 38:866- 870. Euswas A, Warrasak S. Intraocular pressure control following phacoemulsification in pa- tients with chronic angle closure glaucoma. J Med Assoc Thai 2005; 88(suppl 9):S121- S125. Friedman DS, Jampel HD, Lubomski LH, Kempen JH, Quigley H, Congdon N, Levkovitch-Verbin H, Robinson KA, Bass EB. Surgical strategies for coexisting glaucoma and cataract; an evidence-based update. Ophthalmology 2002; 109:1902-1913. Ge J, Guo Y, Lui Y. Preliminary clinical study on the management of angle closure glaucoma by phacoemulsification with foldable posterior chamber intraocular lens implantation. [Chi- nese] Zonghua Yan Ke Za Zhi. 2001; 355-358. Hayashi K, Hayashi H, Nakao F, Hayashi F. Changes in anterior chamber angle width and –13.5 –8.4 –4.9 –6.4 –4.6 –4.4 –4.2 –3.5 –1.8 –3.2 –1.9 –1.8 –1.1 –1.0 +1.3 +1.9 ACG=angle-closure glaucoma; CACG=chronic angle-closure glaucoma; IOP=intraocular pressure; OAG=open-angle glaucoma; OHT=ocular hypertension; PACG=primary angle-closure glaucoma depth after intraocular lens implantation in eyes with glaucoma. Ophthalmology 2000; 107:698-703. Lai JSM, Tham CCY, Chan JCH. The clinical outcomes of cataract extraction by phacoemulsification in eyes with primary angle-closure glaucoma (PACG) and coexisting cataract; a prospective case series. J Glaucoma 2006; 15: 47-52. Lam DSC, Leung DYL, Tham CCY, Li FCH, Kwong YYY, Chiu TYH, Fan DSP. Randomized trial of early phacoemulsification versus peripheral iridotomy to prevent intraocular pressure rise after acute primary angle clo- sure. Ophthalmology 2008; 115:1134-1140. Mathalone N, Hyams M, Neiman S, Buckman G, Hod Y, Geyer O. Long-term intraocular pres- sure control after clear corneal phacoemulsifi- cation in glaucoma patients. J Cataract Refract Surg 2005; 31:479-483. Nonaka A, Kondo T, Kikuchi M, Yamashiro K, Fujihara M, Iwawaki T, Yamamoto K, Kurimoto Y. Cataract surgery for residual angle closure after peripheral laser iridotomy. Ophthalmol- ogy 2005; 112:974-97. Nonaka A, Kondo T, Kikuchi M, Yamashiro K, Fujihara M, Iwawaki T, Yamamoto K, Kurimoto Y. Angle widening and alteration of ciliary process configuration after cataract surgery for primary angle closure. Ophthalmology 2006; 113:437-441. Poley BJ, Lindstrom RL, Samuelson TW, Schulze R Jr. Intraocular pressure reduction after phacoemulsification with intraocular lens implantation in glaucomatous and nonglauco- matous eyes; evaluation of a causal relation- ship between the natural lens and open-angle glaucoma. J Cataract Refract Surg 2009; 35:1946-1955. Shaarawy TM, Sherwood MB, Grehn F, eds. Guidelines on Design and Reporting of Glaucoma Surgical Trials. Amsterdam: Kugler Publications; 2008. Shingleton BJ, Gamell LS, O'Donoghue MW, Baylus SL, King R. Long-term changes in intraocular pressure after clear corneal phacoemulsification: normal patients versus glaucoma suspect and glaucoma patients. J Cataract Refract Surg 1999; 25:885-890. Shingleton BJ, Pasternack JJ, Hung, JW, O'- Donoghue MW. Three and five year changes in intraocular pressures after clear corneal pha- coemulsification in open angle glaucoma pa- tients, glaucoma suspects, and normal patients. J Glaucoma 2006; 15:494-498. Tham CCY, Kwong YYY, Leung DYL, Lam SW, Li FCH, Chiu TYH, Chan JCH, Chan CHY, Poon ASY, Yick DWF, Chi CC, Lam DSC, Lai JSM. Phacoemulsification versus combined phaco- trabeculectomy in medically controlled chronic angle closure glaucoma with cataract. Ophthalmology 2008; 115:2167-2173. Contact information Uhler: tuhler@willseye.org 57