Diseases and Disorders of the Cornea

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 (NK); 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. This article reviews the aforementioned corneal diseases and disorders, 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, but it’s still an important factor to monitor.

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. (Hopefully this helps to decrease the number of corneal transplants necessary for people later in life). 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 be watching 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 condition in which the endothelial cells of the cornea slowly deteriorate, and fluid builds up. It is typically hereditary, predominantly affecting patients 40 years of age and older.² 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.

DRY EYE DISEASE

Every optometrist should know that DED is a multifactorial condition involving a loss of tear film homeostasis and ocular symptoms, and that it can be caused by inadequate tear production, excessive evaporation, or inflammation.³ All doctors should be screening patients for DED because it’s a big contributor to vision fluctuation.

MYOPIA

Myopia occurs when the eye is too long or the cornea is too curved, causing light entering the eye to focus incorrectly and make distant objects look blurry. Individuals with several myopia-prone genes have a higher risk of becoming nearsighted, as do children with one or both parents who are myopic.⁴ Myopia management strategies might include lifestyle and environmental factors, whereas myopia control focuses more on methods to slow down the progression of the condition. Depending on patient age, treatments include the use of myopia control contact lenses (eg, orthokeratology lenses, multifocal contact lenses, soft contact lenses), eyeglasses, laser procedures (eg, LASIK or photorefractive keratectomy), and vision therapy.

ABRASIONS, FOREIGN BODIES, AND RECURRENT CORNEAL EROSIONS

When treating corneal abrasions, corneal foreign bodies, and recurrent corneal erosions, it’s important to know the scope of the legislative law in your state, because although all optometrists are trained to remove corneal foreign bodies, some are not permitted by law to remove them.

NEUROTROPHIC KERATITIS

NK is a reduction or loss of corneal sensation. This type of damage could also be related to Herpes zoster, Herpes simplex, recurrent corneal abrasions, or DED.^5,6 If the fundamental reason for the loss of corneal sensation is NK, the presentation in early stages (stage 1 and stage 2) can look just like any of the aforementioned conditions.

The best way to differentiate NK from the others is to perform corneal sensitivity testing.

KEEPING BUSY WITH CORNEAL DISEASE

Managing the patients in my clinic, we have a strong working knowledge of medical conditions that affect the cornea (See Factors That Can Threaten Corneal Health). For example, patients with diabetes are at higher risk of developing corneal problems such as neuropathic dry eye,⁷ and they are slower to heal after injury and surgery.

Many times, when we identify a corneal condition, it raises suspicion about an autoimmune disease, and if a patient is unaware they have an autoimmune disease, we encourage them to see a rheumatologist. If the patient does know they have an autoimmune condition, then it’s important to monitor their cornea and educate them on how their condition or disease can affect it. We can’t forget about these other systemic and autoimmune conditions, such as rheumatoid arthritis or lupus, which can cause inflammation of the cornea and conditions such as scleritis or keratitis.

SETTING PATIENTS ON A BETTER COURSE

Patients with corneal disease who also want refractive vision correction beyond eyeglasses have options (eg, specialty lenses), and for others, 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.

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.

3. The definition and classification of dry eye disease: report of the Definition and Classification Subcommittee of the International Dry Eye Workshop (2007). Ocul Surf. 2007;5(2):75-92.

4. Myopia (nearsightedness). American Optometric Association. Accessed February 24, 2025. www.aoa.org/healthy-eyes/eye-and-vision-conditions/myopia?sso=y

5. Meyer JJ, Liu K, McGhee CNJ, Danesh-Meyer HV, Niederer RL. Neurotrophic keratopathy after Herpes Zoster ophthalmicus. Cornea. 2022;41(11):1433-1436.

6. Feroze KB, Patel BC. Neurotrophic keratitis. StatPearls [Internet]. August 8, 2023. Accessed March 7, 2025. www.ncbi.nlm.nih.gov/books/NBK431106/

7. Richdale K, Chao C, Hamilton M. Eye care providers’ emerging roles in early detection of diabetes and management of diabetic changes to the ocular surface: a review. BMC Open Diabetes Research & Care. 2020;8:e001094.