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Ocular Manifestations of Ehlers-Danlos Syndrome
By:Dr. Diana Driscoll
Therapeutic Optometrist
Optometric Glaucoma Specialist
There is an amazing amount of collagen in
the eye (80% of ocular structures), but relatively, a surprising
lack of vision threatening Ehlers-Danlos Syndrome (EDS) related effects.
EDS patients often
manifest numerous ocular symptoms. It is important to
understand which symptoms may be indicative of an urgent condition
and which are merely annoying.
Additionally, it can be difficult to know when a symptom is
EDS related, or is an indication of a non-EDS condition.
This summary should help to guide both
patient and doctor with many pieces of the ocular puzzle, guiding
both toward conservative, but not unnecessary treatment and testing.1
An incredible 27 different genes are responsible for making the collagen in the structures of the eye.2 The category of EDS that most greatly affects the eye is the rare Type VI- Kyphoscoliosis Type. In this type, there is a lack of Lysyl Hydroxylase, making the eye structure weak.3 Thus, the eye can perforate with very little trauma. Fortunately there are only about 60 reported cases of the Kyphoscoliosis Type VI worldwide.4
The following are common ocular signs, characteristics and symptoms for EDS patients. Some patients will show many of these signs and symptoms and some will show few, if any.
Dr. Diana Driscoll
High Myopia
Also known as near-sightedness, myopia causes the patient to have more difficulty seeing objects at a distance than objects up close. Myopia is common in EDS and non-EDS patients. Myopia is typically due to a slightly elongated eye or a very steep cornea, or both.5 In EDS, however, the corneas are often found to be fairly flat, meaning that the near-sightedness is due primarily to elongation of the eye.6
Retinal Detachments
EDS patients are prone to myopia and elongated eyes due to the stretching of the collagenous sclera. The retina (neural tissue) doesn’t stretch with the sclera but rather gets “pulled along for the ride” and can become thin resulting in retinal holes, tears, staphylomas, retinal degenerations and detachments. Dilation of the eyes is recommended annually, or any time the patient notices a sudden increase in floaters, flashes of light (usually out to the side of the vision), or immediately if it seems as if a curtain is coming up over one eye. These can be symptoms of a retinal detachment and may need to be treated on an urgent basis.7
Keratoconus
In this condition, the cornea (on the front part of the eye) bulges outward in a cone shape, and gravity pulls the cone downward, blurring the vision and making it difficult to see well with glasses or soft contact lenses. Rigid contact lenses are usually tolerable for many years, but about 40% of keratoconic patients will eventually need a corneal transplant as their rigid contact lenses become less comfortable with progression of their keratoconus. Some new research (discussed below) may radically reduce this percentage soon.
Early symptoms of keratoconus include vision that just doesn’t seem as clear to the patient as it should be – even with use of new glasses or soft contact lenses. It is usually worse in one eye than the other.
Corneal topography will indicate steepened corneal curvature, especially on the inferior cornea. If topography indicates keratoconus this is a prime opportunity to screen the patient for EDS. This screening need not be extensive, but a quick Beighton scale, understanding that hypermobility is more common in the metacarpo-phalngeal and wrist joints with keratoconic patients, is a great place to start.8
In keratoconic patients, one eye is usually able to “cover for the other eye” for months to years, thus no treatment beyond glasses or contacts may be necessary during this time. When both eyes are involved to the point that the patient is unable to see what he/she needs to see, then other options are explored. This usually begins with gas permeable lenses, which may remain comfortable for the patient for many years.
Treatment of Keratoconus
If the gas permeable lenses designed for keratoconus are not comfortable for the patient, one of the new generations of contact lenses with a soft skirt and a rigid center are becoming increasingly popular as manufacturers are learning how to avoid the previously common splitting of the contact lens between the rigid portion and the soft portion. Synergeyes™ lenses are one of the most popular brands. Scleral lenses (rigid lenses that cover the entire cornea and overlap onto the sclera) are making an impressive comeback with increased comfort for the patient, as opposed to the first scleral lenses from decades ago.
If these lenses are not tolerable, or if their comfort is unacceptable at any time, other options can be considered, including:
- Intra-corneal ring segment inserts, such as “Intacs™”. These are small semi-circles that are inserted into the middle layer of the cornea, usually on the inferior portion of the cornea and can often return the patient to acceptable vision with glasses or contact lenses. They are also removable should the need arise.
- Corneal transplantation (or grafting): This may involve a penetrating keratoplasty (a full thickness transplantation or graft) or a lamellar keratoplasty (a partial thickness transplantation or graft). These transplants are generally successful (over 90%) primarily because the cornea does not have a vascular system which would normally transport the cells to reject a transplant. It is possible to see a graft begin to develop keratoconus, but this generally doesn’t begin to occur until at least 18 years after surgery.9
- There is an exciting new discovery that could change the prognosis and lives of keratoconic patients everywhere. Researchers have learned that by rinsing the cornea with riboflavin drops for about 30 minutes, then shining UV-A rays on the cornea for about 30 minutes (CR3) the collagen fibrils of the cornea develop stronger cross-links, strengthening the cornea. This corneal strengthening is resulting in the halt and even the reversal of keratoconic progression. The implications for the treatment of Type VI EDS, and the use of riboflavin and UV-A on the skin is also enticing for most researchers, and we eagerly await testing.10
- Please be aware that patients with EDS, and especially those with signs of keratoconus, are not candidates for radial keratotomy or LASIK refractive correction. Because of the abnormal structure of the collagen in the cornea, the patients are more prone to poor healing, corneal ectasias (bulging of the corneas after surgery), and a disappointing result. Orbscan and pachymetry results usually indicate areas of corneal thinning (prior to surgery).
Although previous studies have indicated that the population of EDS patients rarely shows keratoconus, the corollary indicates the opposite – approximately 40% of keratoconus patients have been shown to have EDS.11—Next: Continue to dry eye syndrome, angoid streaks, lens subluxation