* Please note that this information is for illustrative purposes only, providing a general overview on the topics listed. For any specific questions or concerns regarding your condition, please contact our office so that you can consult with the appropriate person or department to address your needs.
Disease Overview
Myopic degeneration is a type of macular degeneration that can occur when an eye is highly near sighted (high myopia). High myopia is defined as refractive error of at least -6.00D or the actual length of the eye is 26.5mm or more. Vision loss related to myopic degeneration is significant since it can be progressive, irreversible and affects individuals during their most productive years.
Thinning of the various layers of the retina can slowly occur in myopic degeneration. When this thinning occurs to the area directly behind the pupil, or the macula, patients may begin to notice symptoms. Initially, patients may not have symptoms when the macula is not involved. Patients may start to develop symptoms of visual loss when the retinal pigment epithelium thins centrally at the macula. Other areas of the retina can typically show thinning such as the optic disc around the nerve. Changes around the nerve, called peripapillary atrophy, is usually asymptomatic. The optic disc itself also can appear tilted. Depending on the degree of the tilt, a patient may elicit visual field defects on visual field testing. Another type of thinning retina characteristic of myopic degeneration occurs at one of the deep layers called Bruch's membrane. These lacquer cracks which can occur in 4.2% of patients with high myopia (axial length of 26.5 or greater) and can be focal points where abnormal vessels start to grow. These vessels are called choroidal neovascularaization (CNV) and require treatment. Fuch's spots are areas of hyperpigmentation at another level of the retina called the retinal pigment epithelium. Staphyloma development is characterized by outpouching of scleral tissue, typically involving the optic disc or the macula, is a common occurrence. This finding is evident on Optical Coherence Tomography (OCT) or B scan ophthalmic ultrasound. With the use of OCT, physicians are able to detect any serious secondary effects of the staphyloma including epiretinal membrane and macular or foveal schisis. Schisis is a latin word for "splitting". Often macular schisis requires treatment in the form of vitrectomy or scleral buckle surgery. (Please see retinal detachment section for explanation of these procedures)
Incidence
The overall global prevalence is estimated to be 0.9-3.1% depending on the demographic area.
Sequelae (consequence of a previous disease or injury)
Complications associated with visual morbidity in pathologic myopia include progressive thinning and atrophy resulting in photoreceptor loss, development of choroidal neovascular membranes, pigment epithelial detachments and macular or foveal detachments. Ninety-percent of patients with CNV are expected to have atrophy surrounding any previously regressed CNV. Peripheral retinal detachment is another complication.Progressive visual decline in the form of progressive chorioretinal thinning, atrophy and stretching of existing scars is expected in about 40% of patients with pathologic myopia.
Diagnosis
Assessment of visual acuity, intraocular pressure, pupillary reaction and dilated fundus exam are essential. In the hands of a retina trained ophthalmologist, a thorough macular examination and peripheral scleral depressed examination are key to detecting serious developments such as, lacquer cracks, myopic schisis, or choroidal neovascularization in the macula area and holes or tears in the periphery of the retina. Assessment of visual fields and Amsler grid testing may be beneficial especially when ruling out optic disc tilt syndrome and cnv or epiretinal membrane respectively. Fluorescein Angiography is useful for evaluating myopic patients for development of CNV. More recently, OCT- Angiography ( available at all our offices) is essential to detect cnv at its earliest stages, perhaps before bleeding is evident. The physical nature of the staphyloma is detected by thorough dilated fundus examination along with OCT. A-scan is a method of precisely measuring the axial (front to back) length of the eye in order to assess risk of pathologic changes in high myopia. Sometimes B-scan ultrasonography is utilized to visualize the overall appearance of the staphyloma.
Treatment
Patients with stable high myopia may be followed annually for visual acuity, refraction and general ophthalmic health. In the case of development of CNV or other complication patients are followed more closely, as directed by their treatment regimen. There is no medical nor surgical treatment that is known to alter the changes that occur in myopic degeneration as described above. There are, however, treatments available for the aforementioned CNV, a major complication of laquer cracks or retinal pigment epithelial thinning.
Anti-VEGF (vascular endothelial growth factor) therapy is the first line intervention in patients with myopic CNV. The initial evidence was based primarily on retrospective studies and clinician experience. A growing number of prospective and randomized trials have been published or are currently underway. One such trial was RADIANCE (A Randomized Controlled Study of Ranibizumab in Patients with Choroidal Neovascularization Secondary to Pathologic Myopia), a multi-center, randomized controlled trial comparing intravitreal ranibizumab to cold laser (Photodynamic Therapy) in the treatment of myopic CNV. This study reported improved visual acuity at 12 months in the ranibizumab treatment arm.
Patients with decreased vision in the setting of central schisis may benefit from vitrectomy to relieve traction on the fovea and prevent formation of macular holes or macular retinal detachment. Gas or silicone tamponade at the time of surgery is essential in cases of macular hole with or without detachment as this encourages re-apposition of retinal layers. Internal limiting membrane peeling, likewise, is seen as an important asset for relief of traction and improved macular hole closure rates. Retinal detachments may develop however if confined to the area of staphyloma these may be monitored without intervention. Prompt surgery is indicated if any progression is identified.
* Please note that this information is for illustrative purposes only, providing a general overview on the topics listed. For any specific questions or concerns regarding your condition, please contact our office so that you can consult with the appropriate person or department to address your needs.