For purpose of the Finnish guideline on the treatment of open angle glaucoma a literature search was conducted to identify significant articles of the effect of phacoemulsification to the intraocular pressure (IOP). Many studies have noted that cataract extraction could also have a clinically significant role in the control of glaucoma «Masis M, Mineault PJ, Phan E ym. The role of phaco...»18, «Young CEC, Seibold LK, Kahook MY. Cataract surgery...»34.
In a recent review and meta-analysis article by Masis et al. total of 32 previous articles were analyzed. Patients in those studies were subdivided in to four groups: acute angle-closure glaucoma, chronic angle-closure glaucoma, open angle glaucoma and pseudoexfoliation glaucoma. The focus of this Finnish guideline is on the latter two groups. Both groups consisted of patients with glaucomatous defects and ocular hypertension only «Masis M, Mineault PJ, Phan E ym. The role of phaco...»18.
Patients with no exfoliation
A total of 754 eyes were included in the open angle glaucoma group. The mean preoperative IOP was 19.1 mmHg. When including data from all the studies a mean reduction of -2.7 mmHg was observed after phacoemulsification. If only prospective data was analyzed the reduction in IOP was -3.3 mmHg respectively. Minimum follow-up time was 12 months (12-44) «Masis M, Mineault PJ, Phan E ym. The role of phaco...»18.
In the Ocular Hypertension Treatment Study 63 cataract operated eyes were compared to a control group of 743 eyes which were not operated. In the phacoemulsification group, a -4.1 mmHg postoperative reduction in the IOP was reported. The postoperative IOP remained lower than the preoperative IOP for at least 36 months. The average decrease in postoperative IOP from preoperative IOP was 16.5%. Moreover, in almost 40% of the operated eyes the decrease in IOP was 20%. A greater reduction in postoperative IOP occurred in the eyes with the highest preoperative IOP «Mansberger SL, Gordon MO, Jampel H ym. Reduction i...»19. A small study conducted in Finland reported a -3 mmHg decrease in IOP at 12 month and 48 months after phacoemulsification in healthy eyes with cataract and baseline IOP of 6-25 mmHg «Falck A, Hautala N, Turunen N ym. A four-year pros...»35.
A recent matched cohort study compared eyes that underwent phacoemulsification to matched eyes that did not (nonsurgical group). Patients were matched with age, gender, type of glaucoma, baseline IOP and number of glaucoma medications. However, severity of disease was not assessed before or during the study. Mean IOP at study baseline was 16.5 mmHg. Overall a mean reduction of IOP postoperatively was reported at -1.2mmHg, in patients with baseline IOP 20 mmHg a decrease of -2.5 mmHg was reported compared to nonsurgical group «Carolan JA, Liu L, Alexeeff SE ym. Intraocular Pre...»36.
Patients with pseudoexfoliation
Total of 125 eyes were included in the pseudoexfoliation group of the review article. The mean preoperative IOP was 22.7 mmHg. A reduction of -5.8 mmHg was found when looking at all data, if only prospective data was included reduction in IOP was -8.4 mmHg. Minimum follow-up time was 13 months (13-60). An additional -0.84 mmHg decrease was observed for every 1 mmHg in preoperative IOP «Masis M, Mineault PJ, Phan E ym. The role of phaco...»18.
A study of 169 eyes a decrease of -4.0 mmHg was reported in non-exfoliative group and -3.5 mmHg in pseudoexfoliation group «Pohjalainen T, Vesti E, Uusitalo RJ ym. Intraocula...»26. In another study of initial 1122 patients reported -1.9 mmHg reduction at 12 months and -1.3 mmHg at 36 months. It is noteworthy, however, that loss to follow up was significant at 12 months (remaining population n = 422) and more drastic at 36 months (n = 246) «Shingleton BJ, Laul A, Nagao K ym. Effect of phaco...»30.
Intraocular pressure rise after phacoemulsification
Several studies have reported that IOP may rise even after uncomplicated cataract extraction. This IOP spike is more common in glaucomatous eyes than in non-glaucomatous eyes and in patients with pseudoexfoliation «Awai-Kasaoka N, Inoue T, Takihara Y ym. Impact of ...»1, «Chen PP, Lin SC, Junk AK ym. The Effect of Phacoem...»4, «Gedde SJ, Herndon LW, Brandt JD ym. Postoperative ...»8, «Guedes RA, Guedes VM, Chaoubah A. Does phacoemulsi...»9. Incidence of IOP spike in eyes with primary open angle glaucoma patients has been reported between 3–27% and between 11–35% of pseudoexfoliation patients «Chen PP, Lin SC, Junk AK ym. The Effect of Phacoem...»4.
Suggested risk factors for a postoperative IOP spike are longer axial length, deeper anterior chamber, higher number of preoperative medications and history of previous laser trabeculoplasty «Shingleton BJ, O'Donoghue MW, Hall PE. Results of ...»31. Patients with lower starting IOP and more severe glaucoma may also be at greater risk «Poley BJ, Lindstrom RL, Samuelson TW ym. Intraocul...»25.
Typically, when an IOP rise occurs it is a transient phenomenon attributed to i.e. retained viscoelastic or a topical steroid-induced IOP rise «Shingleton BJ, Rosenberg RB, Teixeira R ym. Evalua...»29, «Slabaugh MA, Bojikian KD, Moore DB ym. Risk factor...»32. Though usually transient, the risk of a postoperative IOP elevation cannot be ignored, especially in patients with severe glaucoma. In these instances, extra care should be taken to remove all viscoelastic and patients should be monitored for postoperative IOP spikes. Prophylactic treatment with oral carbonic anhydrase inhibitors or topical antihypertensives should also be considered for immediate postoperative IOP control «Hayashi K, Yoshida M, Manabe SI ym. Prophylactic E...»11, «Holm JL, Bach-Holm D, Holm LM ym. Prophylactic tre...»12, «Levkovitch-Verbin H, Habot-Wilner Z, Burla N ym. I...»16
Timing of phacoemulsification in relation to glaucoma surgery
Trabeculectomy
Cataract surgery can affect the function of the filtering bleb «Inal A, Bayraktar S, Inal B ym. Intraocular pressu...»14. Studies report that phacoemulsification done after trabeculectomy may induce an increase of IOP, with need of additional IOP-lowering medication or additional surgery «Derbolav A, Vass C, Menapace R ym. Long-term effec...»5, «Ehrnrooth P, Lehto I, Puska P ym. Phacoemulsificat...»6, «Klink J, Schmitz B, Lieb WE ym. Filtering bleb fun...»15, «Nguyen DQ, Niyadurupola N, Tapp RJ ym. Effect of p...»22, «Patel HY, Danesh-Meyer HV. Incidence and managemen...»24, «Rebolleda G, Muñoz-Negrete FJ. Phacoemulsification...»27. However, a study showed that the rate of failure of trabeculectomy after phacoemulsification is not different from the natural course of trabeculectomy «Inal A, Bayraktar S, Inal B ym. Intraocular pressu...»14.
In patients with a history of filtering surgery, an increase of approximately 2 mmHg has been reported after uncomplicated phacoemulsification «Klink J, Schmitz B, Lieb WE ym. Filtering bleb fun...»15, «Shingleton BJ, O'Donoghue MW, Hall PE. Results of ...»31
The use of antimetabolites during surgery reduced the failure rate; «Awai-Kasaoka N, Inoue T, Takihara Y ym. Impact of ...»1, «Casson R, Rahman R, Salmon JF. Phacoemulsification...»3, «Longo A, Uva MG, Reibaldi A ym. Long-term effect o...»17, «Swamynathan K, Capistrano AP, Cantor LB ym. Effect...»33. Shorter time between trabeculectomy and cataract surgery «Awai-Kasaoka N, Inoue T, Takihara Y ym. Impact of ...»1, «Husain R, Liang S, Foster PJ ym. Cataract surgery ...»13 and higher baseline IOP «Erie JC, Baratz KH, Mahr MA ym. Phacoemulsificatio...»7 have been identified as risk factors for filtration failure.
Most of the studies reported medium-term results (2–3 years follow-up); in two long-term studies, one reported no effect on IOP «Longo A, Uva MG, Reibaldi A ym. Long-term effect o...»17 and other one reported increase in IOP levels «Park HJ, Kwon YH, Weitzman M ym. Temporal corneal ...»23
Deep sclerectomy
A study with eyes previously gone through deep sclerectomy by Merciece et al. reported the mean IOP had increased from 11 mmHg to 15 mmHg in the first 3 months and remained higher up to a year (p < 0.001) after phacoemulsification. At 12 months the IOP was 1-2 mmHg higher than before phacoemulsification. There was no difference in the probability of maintaining an IOP < 16 mmHg without additional medications or needle revision «Guedes RA, Guedes VM, Chaoubah A. Does phacoemulsi...»9, «Mercieca K, Perumal D, Darcy K ym. Cataract extrac...»21.
A combined phacoemulsification deep sclerectomy procedure seems to provide similar IOP lowering results as deep sclerectomy alone «Mercieca K, Shevade B, Anand N. Outcomes of combin...»20.
Shunt surgery
Studies indicate that in most cases, phacoemulsification in glaucomatous eyes with a functioning tube shunt device improves vision and does not have a significant effect on IOP «Bhattacharyya CA, WuDunn D, Lakhani V ym. Cataract...»2, «Erie JC, Baratz KH, Mahr MA ym. Phacoemulsificatio...»7, «Gujral S, Nouri-Mahdavi K, Caprioli J. Outcomes of...»10, «Sa HS, Kee C. Effect of temporal clear corneal pha...»28. Some patients, however, may need additional IOP-lowering medications to maintain desired level of IOP «Sa HS, Kee C. Effect of temporal clear corneal pha...»28.
Summary
The scientific evidence suggests that IOP has a decreasing tendency of 2-4 mmHg after phacoemulsification and an IOL implantation in non-exfoliative eyes and 4-6 mmHg decrease in eyes with pseudoexfoliation present.
Majority of studies report that reduction of IOP after phacoemulsification is greater in patients with higher pre-operative IOP.
If trabeculectomy or deep sclerectomy has been done before phacoemulsification there is a risk of permanent IOP rise even after a routine cataract extraction. One has to bear in mind that studies reporting results after glaucoma surgery and phacoemulsification are done with small sample sizes. Additionally, reports suggest that risk for IOP rise is smaller if phacoemulsification is performed minimum of 12 months after initial glaucoma surgery.