EXPLAIN THE CAUSES, AND HASTEN VISUAL RECOVERY

HAVING A cataract patient tell you at his one-day post-op appointment that he’s unhappy with his vision and is concerned as to why it isn’t any better — or maybe even worse — than before surgery is not a welcomed surprise.

Often, these patients have pseudophakic corneal edema. It is our role to counsel them on the condition’s risk factors prior to sending them for surgery, explain the specific etiology after surgery and help to hasten their recovery with topical drop therapy and clear communication with their surgeon.

Here, I review the common causes and treatments of pseudophakic corneal edema.

COMMON CAUSES

1. Endothelial cell loss. During cataract surgery, most patients will have temporary trauma to the endothelial cells, secondary to heat from the phaco tip, actual physical trauma during the surgery or residual viscoelastic left on the endothelium. The aftermath is a decrease in the normal osmotic function of the endothelial cells that results in temporary corneal edema.
   In advanced cases of endothelial disease, or an especially traumatic surgery, some of these endothelial cells will be lost, and this may contribute to a longer term corneal edema issue.
2. Mature cataracts. Patients who have dense cataracts will likely need increased phacoemulsification time and ultrasound energy to break up the cataract. Excessive ultrasound energy can be associated with lens fragments or air bubbles contacting the endothelium, local rises in temperature causing thermal damage to the endothelium and the production of free radicals associated with oxidative stress to the endothelial cells.¹
3. Shallow anterior chamber. Patients who have a shallow anterior chamber pre-surgery are more likely to have post-operative corneal edema.² This is because phacoemulsification energy will be closer to their endothelium. Also, endothelial defects in these patients can occur secondary to mechanical trauma from surgical instruments.
4. Retained viscoelastic or lens fragments. Corneal edema can also result from increased IOP secondary to retained viscoelastic in the anterior chamber angle. This, in turn, creates an osmotic imbalance and results in corneal edema. As noted earlier, the viscoelastic can also disrupt the normal osmotic gradient and result in corneal edema.
   Inflammation secondary to retained cortex or nuclear fragments can also create corneal edema due to either increased IOP or actual trauma to the endothelial cells, but this edema usually presents two to seven days after the surgery and is not usually seen at the one-day post-op.
   In cases in which only a small amount of residual cortex is left, surgical intervention may not be necessary.
   In situations where a more significant amount of cortex is left, the surgeon may need to bring the patient back to surgery for aspiration/removal of the remaining cortex. Therefore, be diligent in looking closely in the anterior chamber for any obvious debris, and notify the surgeon of your findings.
5. Anterior chamber (AC) IOL placement. If the surgeon had to switch gears to an ACIOL, secondary to a posterior capsular tear or instability, the proximity of the lens to the cornea may increase the risk for corneal edema.

TREATMENT

• Mild edema (sans IOP spike or excessive inflammation). Apply topical 5% sodium chloride hypertonic ophthalmic ointment and solution to resolve symptoms, such as discomfort, photophobia and reduced or blurry vision. The reason: These medications create a hypertonic tear film, which helps to draw fluid out of the cornea. Since edema tends to be worse after sleeping, have the patient apply hypertonic ointment to the conjunctival cul-de-sac at bedtime and hypertonic solution three to four times throughout the morning to help speed the clearing of the cornea during the peak of the patient’s symptoms.
• Corneal edema with increased anterior chamber reaction (3-4+ cell). Have the patient increase the frequency of post-op topical steroids. The reason: Edema is often a consequence of inflammation; targeting the inflammatory cascade with topical steroids will help to hasten corneal edema. Each surgical group has their preferred topical steroid (prednisolone acetate 1%, difluprednate 0.05%, or combination drops with a steroid, NSAID and antibiotic) to gain greater control of the inflammation, so the increase is relative to what the patient was prescribed for his post-op drop regimen.
  If the patient has corneal edema and an increased AC reaction secondary to retained cortical fragments, have him increase prednisolone acetate 1% q.2.h. or difluprednate 0.05% to q.i.d. or more in the affected eye, depending on the extent of inflammation, and notify the surgeon of your findings. Small cortical fragments will typically resolve with topical treatment, but larger cortical fragments or residual nuclear fragments may require a trip back to the operating room for the surgeon to remove.
• Corneal edema with increased IOP. Have the one-day post-op patient with an IOP of between 25mmHg and 35mmHg use a topical beta blocker or alpha adrenergic agonist b.i.d. Recheck the IOP at the patient’s one-week follow up.
  If the patient’s IOP is higher than 35mmHg, consider “burping the wound” (applying pressure with your chosen sterile instrument peripheral to the incision site) — something that should only be tried by a doctor who is educated, trained and comfortable in how to appropriately do so.
• Corneal edema with bullae. Employ a bandage contact lens to reduce pain. Specifically, fit a flat lens approved for overnight wear, and recheck the patient in one week or less. Tighter bandage lenses may increase corneal edema, so close observation is recommended. A topical, broad spectrum antibiotic is also recommended while bandage lenses are in place.
• Unresolving corneal edema. In the extremely rare circumstance that corneal edema does not resolve by one-month post-op, consider referral to a corneal specialist to consider a partial corneal transplant, such as Descemet’s Stripping Endothelial Keratoplasty or a Descemet’s Membrane Endothelial Keratoplasty, to replace non-functioning endothelium and, ultimately, restore corneal clarity.

OFFER REASSURANCE

Luckily, in the case of the one-day post-op cataract surgery patient, you can reassure him that with a few changes to his post-op drop regimen and a little bit of patience, he can typically expect resolution of his corneal edema and, thus, clearer vision within a week or two. OM

REFERENCES

1. Igarashi T, Ohsawa I, Kobayashi M, et al. Hydrogen prevents corneal endothelial damage in phacoemulsification cataract surgery. Scientific Reports. 2016 6: 31190.
2. Hyung BW, Byul L, Hye BY and Na Young L. Endothelial cell loss after phacoemulsification according to different anterior chamber depths. Journal of Ophthalmology. 2015: 210716.

DR. BRUNT practices at Insight Vision Group in Denver, where she treats glaucoma, dry eye disease and ocular surface disease. She completed residency training in ocular disease at Bascom Palmer Eye Institute. Email her at savannah.brunt@gmail.com.