Success demands an optimized cornea

How to prepare and maintain it during and after cataract surgery.

By Deepinder K. Dhaliwal, MD, L.Ac

Modern cataract surgery has morphed into refractive surgery. Patient expectations are now extremely high, and the surgery will be deemed a “failure” if the postoperative reality does not meet or exceed the preoperative expectations. The cornea’s surface smoothness, clarity and thickness all impact vision and surgery outcomes, so it is crucial to optimize the cornea before, during and after phacoemulsification.

Preoperative optimization of the corneal surface can minimize postoperative complications. Below, we examine common adverse conditions affecting the cornea that, if left untreated, will negatively impact an otherwise successful cataract surgery.¹

Figure. Negative staining pattern seen with EBMD.

PRESURGERY: DRY EYE

Assessment

Dry eye, also called dysfunctional tear syndrome, is extremely common in cataract patients. If dry eye is not treated pre-operatively, keratometry readings could be altered enough to lead to the improper choice of IOL. This is especially critical if a toric or multifocal IOL is selected. Also, effective healing of the corneal surface is more difficult if the tear film is suboptimal. We have even seen postoperative melting of the cornea in patients with severe dry eye (secondary to Sjögren’s syndrome).

Subjective assessment using a patient questionnaire, such as OSDI (Ocular Surface Disease Index), can help screen cataract patients for dry eye. Also, a careful slit lamp exam and tear osmolarity test can help identify patients who will require preoperative treatment.

To assess for dry eye:

• Assess conjunctival and corneal staining.

• Evaluate tear film stability (tear breakup time).

• Examine the lid margin.

• Apply digital pressure to the lid margin/meibomian glands to see the quality and quantity of meibum.

Treatments

Dry eye treatments include anti-inflammatory agents such as Avenova (hypochlorous acid 0.01%, NovaBay), Restasis (cyclosporine 0.05%, Allergan) BID, and/or mild steroids BID or QID. When using hypochlorous acid, I instruct my patients to spray it directly onto their closed eyelids. Then, I tell them with eyes open, to rub the sprayed product along the lower lid margin and let it air dry. Patients apply one spray to the lids twice daily. Also, patients should use warm compresses and heat the eyelids for 15 minutes, followed by a lid massage. Also, recommend oral omega 3/gamma-linolenic acid (GLA) supplementation for most patients and a lid scrub with a tea tree oil product if Demodex is present. If necessary, insert punctal plugs only after controlling the ocular surface inflammation.

PRESURGERY: VIRUSES AND ASTIGMATISM

Herpes simplex virus (HSV)

Any patient with a history of HSV keratitis or “cold sores” has a risk of HSV reactivation after cataract surgery due to surgical stress and steroid use. Antiviral prophylaxis is essential in these cases. We use oral antivirals, such as valacyclovir (Valtrex, GlaxoSmithKline), typically 500 mg BID, starting two days prior to surgery and continuing as long as topical steroids are used. In patients who do not want to take oral prophylaxis, use topical ganciclovir gel (Zirgan, Bausch + Lomb). Remember that herpes simplex viral reactivation in the presence of steroids can cause severe infection and corneal perforation. Therefore, antiviral prophylaxis is essential as long as the patient is on topical steroids.

Herpes zoster keratitis

Unlike patients with herpes simplex, patients with a history of herpes zoster keratitis do not need antiviral prophylaxis. Assess corneal sensation in these patients, and optimize healing since they are often neurotrophic. During surgery, take care to prevent corneal epithelial defects. Minimal use of toxic preservatives (such as BAK) is important.

Epithelial basement membrane dystrophy (EBMD)

EBMD is an under-recognized cause of decreased visual quality due to central irregular astigmatism. To diagnose, simply apply fluorescein in the eye using a moistened fluorescein strip (not a bottled combination product). Use a diffuse blue light to detect areas of negative staining. If significant pathology affects the central visual axis, you could perform epithelial debridement followed by diamond burr polishing or phototherapeutic keratectomy. Keratometry should be repeated after six to eight weeks for proper IOL calculation.

If you do not treat the central EBMD before cataract surgery, counsel patients that the pathology is still present and may affect final visual outcome. Don’t use toric or multifocal IOLs if there is significant central, untreated corneal irregularity, as reliable keratometry cannot be obtained.

DURING SURGERY

Fuchs’ dystrophy

To protect the delicate endothelial cells, use dispersive viscoelastic during cataract surgery. Reapplication of the viscoelastic is indicated in cases with dense nuclei where the viscoelastic may dissipate during the case. Remember to clear a “working space” over the lens prior to entering foot position 3 if the anterior chamber is full of viscoelastic. If the viscoelastic blocks flow of the BSS and the phacoemulsification tip heats up, a thermal corneal burn could result. Do not proceed to phacoemulsification until it is confirmed that “the bottle is dripping.”

If visualization is difficult intraoperatively due to the diffuse guttae or mild edema, trypan blue can be used prior to the capsulorhexis, but the anterior capsule should be painted with the trypan blue underneath the viscoelastic. Otherwise, trypan blue staining of the guttae, which are Descemet’s membrane (DM) excrescences, could make the visualization even harder. Irrigating solution, such as BSS plus (which has added glutathione), can help scavenge free radicals and aid in endothelial cell recovery.

Endocapsular phacoemulsification techniques (such as “stop and chop” or “divide and conquer”) keep most of the phacoemulsification energy away from the corneal endothelium, and therefore cause less damage to these cells. This is especially important in patients with compromised endothelium.

Corneal haze/irregularity

If corneal stromal scars, epithelial compromise or irregularity are present, apply a layer of viscoelastic over the corneal surface. This creates a magnified, improved view of the lens capsule.

Meibomian secretions

If copious meibomian secretions obscure the view, squirting BSS over the cornea often just temporarily displaces the secretions. For a more effective technique, hold the phacoemulsification handpiece over the cornea and go to position 3. This will create a shower of tiny water droplets that are extremely effective in “power-washing” the secretions away.

POSTSURGERY

Edema

Postoperative edema in the central cornea diminishes vision. If the edema is limited to the central cornea, this is typically from localized endothlial trauma/dysfunction. It should clear over time with the aid of high-dose steroids (every one to two hours while awake). We find difluprednate (Durezol, Alcon) most effective in treating postoperative corneal edema or inflammation.

EYE ON THE ODD
A good eye is worth its weight in gold

The popular image of a pirate is as deep-seated as Davey Jones’ Locker, with depictions including accessories like peg legs, parrots and gold earrings. But that bit of jewelry may have been more than just maritime fashion sense.

According to Nic Compton, a writer specializing in boats and nautical history, gold was actually thought to have healing powers by those living in the age of pirates. In Compton’s book “Sailors Can’t Swim and Other Marvellous Maritime Curiosities,” he writes that pinning gold to one’s ear was thought “to improve eyesight — which sounds a bit mad until you find out there’s an acupuncture point in the ear that relates to vision.”

Other reasons for the gold earrings, writes Mr. Compton, were to pay for funerals should the unfortunate sailor meet an untimely end, to mark a successful trip around Cape Horn, or simply because they liked it.

If the edema involves the entire cornea (limbus to limbus), the patient may have toxic anterior segment syndrome. In this case, the corneal edema takes much longer to improve and might not resolve completely.

In cases with severe segmental edema, consider a localized DM detachment. It usually starts from either the main corneal wound or a paracentesis. Place an air bubble in the anterior chamber to reappose DM and hasten resolution of the edema.

Punctate keratopathy

In patients with severe ocular dryness or a neurotrophic cornea, we limit use of drops with toxic preservatives (such as BAK, or benzalkonium chloride) and may not use topical NSAIDs. We follow these patients very carefully and recommend use of nonpreserved artificial tears four times daily (two hours after using the topical antibiotic and steroid). These patients may need a nighttime gel or ointment to help heal the cornea overnight.

HSV

For patients with a known history of HSV keratitis, iritis or “cold sores,” continue oral antiviral prophylaxis as long as they use topical steroids. Initially, use valacyclovir 500 mg BID and steroid drops QID. As the steroid is tapered, decrease the valacyclovir to once daily after two weeks and continue at this dose for another two weeks.

Conclusion

To get optimal results after cataract surgery, surgeons need to take time to understand the patient’s underlying corneal pathology, and to modify the patient’s typical peri-operative routine to optimize each patient’s outcome. Careful pre-operative assessment, meticulous surgical technique and close postoperative follow-up will maximize outcomes. OM

REFERENCE

About the Author

Deepinder K. Dhaliwal, MD, L.Ac is a professor of ophthalmology at the University of Pittsburgh School of Medicine. She serves as the director of both the Cornea Service and the Refractive Surgery Service, and is associate director of the Charles T. Campbell Ocular Microbiology Laboratory. She is medical director of the UPMC Laser Vision/Aesthetics Center and is the founder and director of the Center for Integrative Eye Care.