November 2019

ASCRS NEWS

Managing irregular corneas prior to cataract surgery


Clara Chan, MD, FRCSC, FACS EyeWorld Cornea Section Editor

In this month’s EyeWorld, we explore clinical scenarios of abnormal corneas that can often be found in patients presenting for cataract surgery consultations. It is important that the ophthalmologist recognize and manage these irregular corneas prior to intraocular lens calculations and cataract surgery.
Keratoconus is usually the first disease that comes to mind when we think of irregular astigmatism. It has a wide range in prevalence, depending on geography, but can be found on average in 1 in 2,000 patients. Topography-guided PRK and intrastromal ring segments may help to improve irregular corneal astigmatism such that a patient may become a candidate for a toric intraocular lens after treatment. Crosslinking is another consideration and a scleral contact lens trial is important to discuss with the keratoconus patient.
Dry eye changes on the corneal surface can also induce irregular astigmatism. A paper published by the ASCRS Cornea Clinical Committee in May 2019 presented an algorithm for the preoperative diagnosis and treatment of ocular surface disorders.1 The take-home message is to address dry eye signs or symptoms with patients prior to cataract or refractive surgery. Mention to your patient that eye surgery may worsen dry eye symptoms in the informed consent process so that you do not get blamed postoperatively.
Lumps and bumps on the surface of the cornea caused by Salzmann’s nodules, epithelial basement membrane dystrophy, and pterygia may cause abnormal MMP-9 testing and irregular corneal astigmatism. The best way to identify visually significant disease is to examine the quality of the placido disk mires on topography; they will be distorted due to surface abnormalities. Studies have shown that these surface conditions can alter keratometry data, thus appropriate management before cataract surgery can yield more reliable biometric data for surgical planning.2,3
Fuchs’ dystrophy we typically consider to be primarily an endothelial cell disorder. However, the associated subclinical or frank corneal edema present can also be a source of irregular astigmatism as the corneal epithelium and Bowman’s membrane is secondarily affected. Some cornea surgeons are advocating for DMEK surgery prior to cataract surgery and one of our feature articles will include some great discussion on this topic.
I hope you enjoy this month’s cornea articles in EyeWorld magazine and remember to look for any abnormal corneas in your next patient being seen for a cataract consultation.

References

1. Starr CE, et al. An algorithm for the preoperative diagnosis and treatment of ocular surface disorders. J Cataract Refract Surg 2019; 45:669–684.
2. Bae SS, Chan CC. Superficial keratectomy: indications and outcomes. Can J Ophthalmol 2018; 53:553–559.
3. Goerlitz-Jessen MF, Gupta PK, Kim T. Impact of epithelial basement membrane dystrophy and Salzmann nodular degeneration on biometry measurements. J Cataract Refract Surg 2019; 45:1119–1123.

Managing irregular corneas prior to cataract surgery Managing irregular corneas prior to cataract surgery
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