One of the most common causes of poor vision after cataract surgery is swelling in the back of the eye[1],[2]. When the center of the retina (called the “macula”) becomes swollen this condition is called “macular edema”. Macular edema commonly limits central vision and can last for months. There are both eye drop and injectable treatments available but they do not always work. Rarely the swelling persists and permanent limitation of vision results.
What is Macular Edema?
“Edema” is just a clinical term that means “swelling”. The macula is made up of very organized and tightly packed cylindrical cells. You can imagine them as being lined up like the pile of newly installed carpet. This arrangement of cells is critical to maintaining crisp vision.
Swelling results in fluid collecting between these cells. This pushes them out of their neatly organized arrangement. If you think about what pile carpet looks like after it’s been walked on you’ll have an idea of what a swollen macula looks like under the microscope. With the retinal cells so disorganized they can no longer detect light as efficiently or accurately. This results in limited vision.
[EyeSmart — American Academy of Ophthalmology. Macular Edema and Ischemia [Internet]. 2009 [cited 2016 Jan 18]. Available from: https://youtu.be/vnE_SyX8xpc]
What Causes Macular Edema after Cataract Surgery?
Edema is a product of inflammation which is a natural result of the body’s attempt to heal tissue after any trauma or surgery. When certain eye tissues are manipulated they release chemicals that act as messengers telling the body to start the healing process. These chemicals go by names such as cytokines and prostaglandins. Elevated levels of prostaglandins are associated with macular edema[3].
Inflammation After Laser-Assisted or Ultrasound-only Cataract Surgery
When Femtosecond laser-assisted cataract surgery (also called “FLACS”) first appeared it was (and still is) marketed as “gentler” and “safer”. This was largely because it resulted in the need for less ultrasound energy. Prior to the introduction of FLACS all cataract surgeries were performed using ultrasound. This is called “Phacoemulsification”. Ultrasound energy was known to be associated with swelling of the cornea so it was assumed that anything that reduced ultrasound energy would be good for the eye.
The problem with assumptions, however, is that they are essentially guesses and are often wrong. Light, as with ultrasound, transmits energy. The body, it seems, doesn’t much care whether energy is mechanical (from a blade), vibrational (ultrasound), or electromagnetic (laser). All forms of energy can result in trauma to tissue which then releases pro-inflammatory chemicals such as prostaglandins. Thus, there’s no logical reason to believe that laser-assisted cataract surgery would produce less inflammation than would ultrasound-only cataract surgery. Indeed, at least one study has demonstrated that the concentration of prostaglandins was shown to be higher after laser-assisted cataract surgery compared to ultrasound-only cataract surgery[4].
Macular Edema After Laser-Assisted or Ultrasound-only Cataract Surgery
Because swelling of the macula can limit vision it is critically important to answer the question, “Does laser-assisted cataract surgery cause more, less, or the same amount of edema than ultrasound-only cataract surgery?”
Alas, the definitive answer is not known. However, the results of a study published in late 2015 would suggest that laser-assisted cataract surgery may not be so “gentle” after all[5]. This study compared rates of clinically significant macular edema between patients who underwent FLACS or ultrasound-only cataract surgery. What the study found was a four-fold increase in macular edema in the laser-assisted cataract surgery group (0.8%) versus the ultrasound-only group (0.2%).
These results suggest that femto laser-assisted cataract surgery results in an increased risk of the vision-limiting complication of macular edema. However, this trend was not statistically significant. Nonetheless, even if FLACS does not cause more inflammation than ultrasound-only cataract surgery this study places great doubt on the supposed FLACS benefits of “gentler” and “safer” commonly touted in advertisements, websites, and office brochures.
Of note is that the patients in this study who chose to have laser-assisted cataract surgery each paid $750 for the “benefit” of having FLACS. As of this writing, that’s the equivalent of $525USD. It’s doubtful that anyone in the USA would get such a “deal” as that’s about what the femto laser companies charge surgery centers just to use the laser. In order to avoid losing money on the laser most surgery centers in the USA charge the doctor or patient at least $800 per use. Even at just over $500, however, one must ask the question, “What am I getting for this price?”
If the study described above is to be believed, those who pay extra for femto laser-assisted cataract surgery may be getting nothing other than added risk. And even if the above study is discounted as it was not “statistically significant” all that means is that FLACS is not inferior to ultrasound-only cataract surgery with regard to incidence of macular edema.
But who pays extra for something that is just “not worse” than something that could be had for less expense?
Who, indeed?
Want to learn more about Laser-Assisted Cataract Surgery? Click here.
References
[1] Benitah NR, Arroyo JG . Pseudophakic cystoid macular edema. Int Ophthalmol Clin 2010; 50:139–153.
[2] Yonekawa Y, Kim IK. Pseudophakic cystoid macular edema. Curr Opin Ophthalmol 2012; 23:26–32.
[3] Miyake K, Ibaraki N. Prostaglandins and cystoid macular edema. Surv Ophthalmol 2002; 47(suppl 1):S203–S 218
[4] Schultz T, Joachim S C, Kuehn M, Dick HB. Changes in prostaglandin levels in patients undergoing femtosecond laser-assisted cataract surgery. J Refract Surg 2013;29:742–747
[5] Ewe SYP, Oakley CL, Abell RG, Allen PL, Vote BJ. Cystoid macular edema after femtosecond laser-assisted versus phacoemulsification cataract surgery. J Cataract Refract Surg 2015;41:2373–2378.
About the Author:
Dr. David Richardson has performed thousands of cataract surgeries without the need for laser assistance. Although he finds Femto technology to be interesting he is far from convinced that there is any real benefit to his patients. As such, he has chosen not to recommend this technology to his patients who need cataract surgery.
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