Intraocular Pressure Reduction after Phacoemulsification

Clinical Question

Previous studies have showed that phacoemulsification can lead to a reduction in intraocular pressure, but with a wide range of change. How much reduction in intraocular pressure does phacoemulsification cause, based on diagnosis of glaucoma, ocular hypertension, glaucoma suspect, and anatomical narrow angles?

Bottom Line

Phacoemulsification was associated with a reduction in intraocular pressure ranging from 0.7 to 1.9 mmHg based on the patient diagnosis (glaucoma, ocular hypertension, glaucoma suspect, and anatomical narrow angles), but this average is lower than reported in several previous studies.

Major Points

Several prior studies suggested that the intraocular pressure reduction due to phacoemulsification was greater than seen in this study from Kaiser Permanente. This study demonstrated that the reduction in intraocular pressure was approximately 0.7 to 1.9 mm Hg based on glaucoma subtype and that reductions in pressure were lower for lower preoperative baseline intraocular pressure (<20 mm Hg).

Design

• Retrospective Cohort Study
• N=16,169 matched pairs
• Setting: Kaiser Permanente Northern California
• Enrollment: June 2010 through May 2015
• Mean follow-up: 36 months post index
• Analysis: Intention-to-treat
• Primary outcome: Change in intraocular pressure

Population

Inclusion Criteria

• Adult Kaiser Permanente members
• Less than 89 years old
• Enrolled between 6/2010 – 5/2015 with 1 year of baseline enrollment
• Inpatient or outpatient diagnosis of glaucoma

Exclusion Criteria

• Glaucoma related to congenital anomaly
• Glaucoma associated with ocular disorders
• History of cataract surgery prior to the start of study
• Did not have preoperative measurement of IOP prior to cataract surgery
• Underwent previous SLT or glaucoma surgery either inpatient or outpatient
  • Glaucoma surgery includes SLT, Baerveldt shunt, Ahmed shunt, trabeculectomy

Baseline Characteristics

Based on All IOP Measurements group

• Patients and controls were matched on age, gender, type of glaucoma, baseline IOP, and number and type of glaucoma medications.

• Age: 32.5% less than 69 years, 44.6% between 70-79, 22.9% greater than 80 in non-surgical group. 32.0% less than 69 years, 43.6% between 70-79, 24.5% greater than 80 in surgical group.
• Gender: 58.8% Female 41.2% Male
• Charlson Comorbidity Index for non-surgical group: 47.6% score of 0, 19.0% score of 1, 13.8% score of 2, 19.5% score of greater than 3.
• Charlson Comorbidity Index for surgical group: 40.4% score of 0, 19.6% score of 1, 16.1% score of 2, 23.9% score of greater than 3.
• Ocular Comorbidities for non-surgical group: AMD 8.6%, Corneal disorders 2.5%, ERM 3.2%, Diabetic retinopathy 5.5%
• Ocular Comorbidities for surgical group: AMD 11.3%, Corneal disorders 3.9%, ERM 5.1%, Diabetic retinopathy 8.4%

Interventions

• This was a retrospective study that looked at matched individuals with a glaucoma diagnosis for those that received cataract surgery and those that did not.
• Patients were either labeled as surgical, meaning they underwent cataract surgery during the study period, or non-surgical, meaning they did not undergo cataract surgery.
• The day of cataract surgery is referred to the index date.

Outcomes

Comparisons are surgical group vs. non-surgical group.

Primary Outcomes

Difference in Intraocular Pressure

Increase by 0.22 mm Hg from baseline to post-index in non-surgical group vs decrease by 0.99 mm Hg in surgical group.

Difference-in-difference of 1.21 (95% CI 1.20 - 1.12)

Secondary Outcomes

Proportion of Patient Receiving a Dispensing of Ophthalmic Medication

5% lower in surgical patients vs. non-surgical patients (95% CI 3-6%)

Rate of Selective Laser Trabeculoplasty in Glaucoma Suspects

n=87 nonsurgical vs. n=27 surgical

Rate of Glaucoma Surgery in POAG

2.0%, N=68 non-surgical and 3.0% N=101 surgical patients; OR, 1.48; 95% CI 1.08-2.01

Subgroup Analysis

Difference in Intraocular Pressure using Goldmann Applanation Only

Difference-in-difference of 1.19 (95% CI 1.06 - 1.32) between non-surgical and surgical group

Criticisms

• Use of IOP measurement techinques other than Goldmann applanation, hwoever a subgroup analysis was conducted as part of this study.
• Use of only a single baseline IOP measurement
• Inclusion of patients with a history of vitrectomy or complications during surgery, but this proportion was fewer than 2% of patients
• Lack of information on severity of glaucoma

Funding

Funded by the National Eye Institute R01 EY027329. The project also used products developed under earlier research grants provided by NEI R21 EY022989, Kaiser Permanente’s Community Benefit program, and the Garfield Memorial Fund, Kaiser Permanente.

Further Reading

1. Weinreb RN, Aung T, Medeiros FA. The pathophysiology and treatment of glaucoma: a review. JAMA. 2014;311:1901–11. [PubMed: 24825645]

2. Armstrong JJ, Wasiuta T, Kiatos E, et al. The Effects of Phacoemulsification on Intraocular Pressure and Topical Medication Use in Patients With Glaucoma: A Systematic Review and Meta-analysis of 3-Year Data. J Glaucoma. 2017;26:511–522. [PubMed: 28333892]

3. Azuara-Blanco A, Burr J, Ramsay C, et al. Effectiveness of early lens extraction for the treatment of primary angle closure glaucoma (EAGLE): a randomised controlled trial. Lancet. 2016;388:1389– 1397. [PubMed: 27707497]

4. Chen PP, Lin SC, Junk AK, et al. The Effect of Phacoemulsification on Intraocular Pressure in Glaucoma Patients: A Report by the American Academy of Ophthalmology. Ophthalmology. 2015;122:1294–307. [PubMed: 25943711]

5. Mansberger SL, Gordon MO, Jampel H, et al. Reduction in intraocular pressure after cataract extraction: the Ocular Hypertension Treatment Study. Ophthalmology. 2012;119:1826–31. [PubMed: 22608478]

6. Baek SU, Kwon S, Park IW, Suh W. Effect of Phacoemulsification on Intraocular Pressure in Healthy Subjects and Glaucoma Patients. J Korean Med Sci. 2019;34:e47. [PubMed: 30787680]

7. Chen HY, Lin CL, Kao CH. Changes in glaucoma medication numbers after cataract and glaucoma surgery: A nationwide population: 10.1097/MD.0-based study. Medicine (Baltimore). 2019;98:e14128. [PubMed: 30681574]

8. Yoo C, Amoozgar B, Yang KS, et al. Glaucoma severity and intraocular pressure reduction after cataract surgery in eyes with medically controlled glaucoma. Medicine (Baltimore). 2018;97:e12881. [PubMed: 30335009]

9. Jimenez-Roman J, Lazcano-Gomez G, Martínez-Baez K, et al. Effect of phacoemulsification on intraocular pressure in patients with primary open angle glaucoma and pseudoexfoliation glaucoma. Int J Ophthalmol. 2017;10:1374–1378. [PubMed: 28944195]

10. Shoji T, Tanito M, Takahashi H, et al. Phacoviscocanalostomy versus cataract surgery only in patients with coexisting normal-tension glaucoma: midterm outcomes. J Cataract Refract Surg. 2007;33:1209–16. [PubMed: 17586377]

11. Vinod K, Gedde SJ, Feuer WJ, et al. Practice Preferences for Glaucoma Surgery: A Survey of the American Glaucoma Society. J Glaucoma. 2017;26:687–693. [PubMed: 28692597]

12. Liu L, Herrinton LJ, Alexeeff S, et al. Visual outcomes after cataract surgery in patients with type 2 diabetes. J Cataract Refract Surg. 2019;45:404–413. doi: 10.1016/j.jcrs.2018.11.002. [PubMed: 30638823]

13. Liu L, Shorstein NH, Amsden LB, Herrinton LJ. Natural language processing to ascertain two key variables from operative reports in ophthalmology. Pharmacoepidemiol Drug Saf. 2017 ;26:378– 385. doi: 10.1002/pds.4149. [PubMed: 28052483]

14. Deyo RA, Cherkin DC, Ciol MA, Adapting a clinical comorbidity index for use with ICD-9-CM administrative databases. J Clin Epidemiol 1992;45:613–19. [PubMed: 1607900]

15. Bojikian KD, Chen PP. Intraocular Pressure After Phacoemulsification in Open-angle Glaucoma Patients With Uncontrolled or Marginally Controlled Glaucoma and/or With Severe Visual Field Loss. J Glaucoma. 2018;27(2):108–114. [PubMed: 29303878]

16. Kim JI, Rabiolo A, Morales E, et al. Cataract Surgery and Rate of Visual Field Progression in Primary Open Angle Glaucoma. Am J Ophthalmol 2019;201:19–30. [PubMed: 30703355]

17. Samuelson TW, Chang DF, Marquis R, et al. A Schlemm Canal Microstent for Intraocular Pressure Reduction in Primary Open-Angle Glaucoma and Cataract. Ophthalmology. 2019;126 (1):29–37. [PubMed: 29945799]