Diseases and Disorders of the Cornea: Part I

By Diana Chu, OD

The cornea is vulnerable to a range of diseases that can compromise both vision and comfort. Those most commonly seen by optometrists in clinic are keratoconus; Fuchs endothelial dystrophy; Herpes simplex virus and Herpes zoster; dry eye disease (DED); myopia; neurotrophic keratitis; and corneal abrasions, corneal foreign bodies, and recurrent corneal erosions. Most of these conditions are progressive; therefore, if left untreated, they can result in some form of scarring, nerve damage, or even changes in vision. Thus, we need to have more medical vigilance about the disease state of the cornea. This means paying attention to the health of the cornea, not just managing a patient’s sight and vision. Part one of this article by Diana Chu, OD, reviews keratoconus; Fuchs endothelial dystrophy; and Herpes simplex virus and Herpes zoster, including any noteworthy points about their signs, symptoms, differentials, and treatment options.

KERATOCONUS
This condition is identified by progressive thinning and steepening of the cornea, which causes distortion and irregular astigmatism.¹ Corneal topography or tomography is a diagnostic tool for identifying keratoconus (Figure) and the subclinical form of keratoconus called forme fruste, which may never progress to clinical disease.

Figure. A Holladay report from a Pentacam (Oculus) image of a patient with keratoconus.

Rigid gas permeable (RGP) or scleral lenses are popular options for the refractive correction of keratoconus. Corneal crosslinking (CXL) used to be reserved for more advanced cases, but more recently, depending on the age of the patient and other risk factors, it is being used to slow progression in mild cases. CXL essentially freezes the progression of keratoconus; it, unfortunately, cannot reverse it, which is why it’s important to diagnose and identify this condition in younger patient populations, so that, if indicated, they can receive CXL and not have scarring that’s detrimental to their visual development. You want to watch kids all the way up into their 20s and maybe their 30s for the progression of keratoconus because it can develop quite rapidly.

FUCHS ENDOTHELIAL DYSTROPHY
Fuchs endothelial dystrophy is a hereditary condition that primarily affects individuals 40 years of age and older.² It involves the gradual deterioration of the corneal endothelial cells, leading to fluid accumulation and swelling of the cornea. Many treatments for Fuchs endothelial dystrophy involve hypertonic saline drops, but in advanced stages, most clinicians opt for Descemet membrane endothelial keratoplasty or a corneal transplant.

It’s important to monitor and identify patients with Fuchs endothelial dystrophy because as patients age and need cataract or other ocular surgery, it can potentially contribute to complications postoperatively. Or, if they have Fuchs endothelial dystrophy in addition to other corneal conditions and need an RGP or scleral lens, it’s a risk for additional complications and is thus something a more experienced practitioner needs to be aware of in order to ensure the patient’s needs are met.

HERPES SIMPLEX VIRUS AND HERPES ZOSTER
Herpes simplex virus and Herpes zoster can be identified at the slit lamp and are more common in older patients. Both are masquerading conditions, so you’ll want to monitor patients considering specialty lens wear or any type of ocular surgery and ask about a history of these diseases because they can look like a corneal abrasion, or a patient can have prodromes before developing an actual manifestation. These are important differentials to keep in mind because these conditions can permanently scar the cornea and lead to decreased vision.

SETTING PATIENTS ON A BETTER COURSE
Patients with corneal disease who also want refractive vision correction beyond eyeglasses have options (eg, specialty lenses). For some patients, vision correction isn’t so much the goal as is halting the progression of their disease, in which case CXL may be the best choice. Lifestyle modifications, such as limiting exposure to ultraviolet light, staying hydrated, maintaining proper lid hygiene, and not smoking, can help keep the cornea and ocular surface healthy.

References:

1. Nuzbrokh Y, Rosenberg E, Nattis A. Diagnosis and management of keratoconus. American Academy of Ophthalmology. September 1, 2020. Accessed February 19, 2025. www.aao.org/eyenet/article/diagnosis-and-management-of-keratoconus
2. Matthaei M, Hribek A, Clahsen T, Bachmann B, Cursiefen C, Jun AS. Fuchs endothelial corneal dystrophy: clinical, genetic, pathophysiologic, and therapeutic aspects. Ann Rev Vis Sci. 2019;5:151-175.

• Optometrist, Washington Eye Institute, Washington, DC
• dianachuod@gmail.com
• Financial disclosure: None

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