Near sightedness and The Retina

Even though you might not have diabetes or macular degeneration, if you are near sighted you might need normal exams with a retinal specialist.

What is Myopia?

Myopia is the eye condition where one has the ability to see well at near but without correction objects in the distance are blurred.  This is normally called near sightedness. In the United States, 10 to 20% of the population suffers from myopia.  Patients are classified as being mildly myopic if their correction is less the -3.00 diopters, moderate if the correction is between -3.00 and -6.00 diopters, and high if the correction is -6.00 diopters or above.  Mild and moderate myopes generally have no retinal problems and their vision can be corrected with glasses.  High myopes, which make up 30% of those with myopia, can also have corrected vision with glasses but frequently, have retinal problems.

Why are People Myopic?

Myopia occurs when the image being observed is not focused exactly on the surface of the center of vision, i.e. the macula. There are three reasons this occurs.  A refractive cause occurs when the curvature of the cornea and/or the lens result in the focal point being in front of the macula.  The second cause is due to a long axial length of the eye (which means the eye is longer then normal from front to back), and the third cause is metabolic, due to either a systemic disease like diabetes or a drug side effect.  Of these causes, the first is by far the most common.

What Retinal Problems Are Associated With High Myopia?

High myopes with long axial length eyes are those who have the most risk of retinal problems.  The cause results from either an unusually large eye or a bulge in the back of the eye, i.e. staphyloma.  In both cases all layers of the eye are stretched.  Stretching of retina in the back of the eye leads to not only thinning of the retina, but may also result in a splitting of the retina tissue called “macular schisis”, which results in decreased vision.  Thinning of the retina peripherally manifests itself as lattice degeneration, atrophic holes and retinal tears, which increase the risk of retinal detachments.  The latter condition is an ocular emergency and may occur suddenly, particularly after trauma.

Thinning of the inner lining of the eye, particularly under the macula, results in breaks in the continuity of the involved tissue.  This leads to decreased vision and may also result in the ingrowth of abnormal blood vessels under the retinal.  In turn, these abnormal blood vessels can rupture causing subretinal hemorrhaging similar to that found in wet age-related macular degeneration.

If the sclera, the thick outer wall of the eye, is thinned, it presents a potential complicating condition should there be a retinal detachment.  Since retinal detachments are not uncommonly treated with a scleral buckle, the creation of scleral tunnels or the placement of sutures through the sclera used to secure the buckle in place, become risky.  Either of these maneuvers could result in further thinning of the sclera and/or uncontrolled perforation of the inner lining of the eye.  Should the latter occur there would be uncontrolled drainage of subretinal fluid resulting in incarceration of retina in the perforation site and/or, since the inner layer is also vascular, bleeding into the subretinal space.

 What Precautions Should a High Myope Take?

Patients who have high myopia should get regular check-ups, which should include a careful evaluation of the macula and the peripheral retina.  This would best be performed by a retinal specialist who would be looking for peripheral retina pathology, which would increase the risks of a retinal tear and/or detachment.  If significant pathology is noted a recommendation for prophylactic treatment may be made.  If macular schisis is present, it is possible to repair the condition with a vitrectomy and injection of gas.

If you are very near sighted (a high myopia) and would like your eyes evaluated by our retinal specialist, Dr. Chen or Dr. Torres, please call 941-921-5335 to make and appointment.

 

Mel Chen, MD

Vitreo-retinal surgeon

Sarasota Retina Institute

Sarasota, Florida  

 

Jody Abrams, MD, FACS
Oculoplastics/Neuro-ophthalmology
Sarasota Retina Institute
Sarasota, Florida 34239