Dr. Orwa Nasser MD MPH - Fitting lenses in patients with nystagmus

Fitting lenses in patients with nystagmus

As mentioned, nystagmus is a condition in which the eyes move involuntarily and without control. Nystagmus appears in both eyes and can vary in frequency and range of motion depending on the cause of the phenomenon. Nystagmus is usually accompanied by poor and poor quality vision. It is important to remember that nystagmus is the result of a certain disease or condition in the eyes and it appears, in the form of eye tremors, as a secondary result of a primary injury to the eyes or brain. This injury causes poor vision, loss of coordination between the two eyes, resulting in involuntary and continuous eye twitching.
 

Adjusting contact lenses and improving vision in nystagmus:
In many cases, people who have nystagmus also suffer from refractive problems in high degrees, such as nearsightedness (myopia) in high numbers, farsightedness (hyperopia) in high numbers, astigmatism (cylinder) in high numbers. Nystagmus patients with high cylinder can benefit from fitting special lenses to treat high cylinder. The best method to improve vision and eliminate the cylinder in the cornea with high astigmatism (cylinder) is a contact lens. There are different types of contact lenses, each of which has its own advantages and disadvantages: Soft contact lenses with a cylinder (Toric soft contact lenses): these lenses are soft lenses but at the same time they are toric lenses that aim to correct a corneal cylinder. These lenses are suitable for cases of nystagmus with a cornea with a cylinder that visually affects but relatively a straight and not distorted cylinder.

- Soft-K lenses: These lenses are soft lenses but thick in the center. They are suitable for cases of corneal nystagmus with a twisted cylinder and a small to medium degree and myopia/hyperopia of a small to medium degree.

- Rigid lenses (RGP): These lenses are hard and relatively small lenses, 5-6 mm in size. These lenses are suitable for cases of nystagmus with a cornea with a distorted/non-distorted cylinder and a small to moderate degree and myopia/hyperopia in a small to moderate degree.

- Semi-scleral contact lenses: These lenses are hard lenses but with a size of 13-15 mm. These lenses are suitable for cases of nystagmus with a distorted/non-distorted cylinder cornea and medium to high degree and myopia/hyperopia of medium to high degree.

- Scleral contact lenses: These lenses are hard lenses but with a size of 15-20 mm and sometimes more. These lenses are suitable for cases of nystagmus with a distorted/undistorted cylinder cornea and a high to very high degree and myopia/hyperopia of a high to very high degree .

- Hybrid contact lenses: These lenses are hard in their center but soft in their periphery. These lenses are suitable for cases of nystagmus with a cornea with a distorted/non-distorted cylinder and a small to medium degree and myopia. hyperopia of a small to medium degree.
 

How is the process of fitting contact lenses for keratoconus carried out?
The matching process takes at least an hour and sometimes even more. During the adjustment, a repeated eye test is performed. Repeated corneal mapping and measurements of corneal curvature and corneal diameter are performed. In accordance with the above, and as a start a lens will be selected empirically and a compatibility test for this type of lens is performed.
If the lens is not comfortable for the patient and does not sit well and is not well centered on the cornea, switch to another type of lenses for adjustment. Keep repeating this process until you find a lens that fits and is comfortable for the patient.
If the lens is comfortable for the patient and gets along well with it, and it sits and is well centered on the cornea, a repeat refraction test is performed and the amount of residual refractive error is checked. Keep doing this until you get the best evidence available.
According to the above, the number and type of the lens are ordered.