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Lattice Degeneration
Overview
Lattice degeneration is an area of thinning of the peripheral retina that occurs in myopes (near-sighted people) but has been known to occur in non-myopes. Its incidence in the general population is 6 to 10%.
It is the most important visible retinal lesion predisposing to retinal tears and detachment. Lattice degeneration is typically characterized by sharply demarcated oval or round areas that are oriented circumferentially and associated with liquefaction (degeneration) of the overlying vitreous gel. These areas of lattice degeneration represent thin sections of retina that can be prone to holes or tears. Traction of the vitreous on these areas after posterior vitreous detachment is often responsible for retinal holes, tears and/or detachment.
Lattice degeneration is not symptomatic independently, but if a patient begins to develop traction from the vitreous pulling on the areas of lattice degeneration causing symptoms of flashes and floaters, the area of lattice degeneration may need to be treated if holes, tears or a localized detachment develops.
When symptoms of flashes and floaters develop, this is often an indication that the vitreous gel in the back of the eye is beginning to separate from the retina. This process is called liquefaction of the vitreous. As the vitreous continues its separation, the thinning retina within these patches of lattice can tear.
Incidence
Lattice degeneration is correlated with an above average overall size and length of the eye, which usually means the patient is near-sighted or has myopia. It has been observed in about 15% of eyes with axial lengths of 30 mm or more, where as it was present in less than 7% of eyes with axial lengths of 27 mm or less. Other reports have found an incidence of 19% of myopic eyes and in 5% of emmetropic patients (no refractive error). Studies have shown that about 25% of eyes with lattice degeneration are emmetropic or hyperopic (far-sighted).
Lattice degeneration is not correlated with patient age. Subtle lesions can occur in elderly patients, and prominent lesions are sometimes seen in young individuals. In patients who have lattice degeneration, its maximum prevalence occurs early in the second decade of life. New patches of lattice degeneration occur infrequently thereafter. Changes in the status of lattice lesions occur slowly whereas the more acute changes would represent a vitreous separation with traction on the areas of lattice degeneration leading to a new hole, tear or detachment.
Posterior Vitreous Detachment (separation of the vitreous from the retina) typically occurs between age 55-65 and is associated with a 5% risk of developing retinal holes, tears or detachment.
Sequelae
Retinal breaks, holes and retinal detachments are the important sequelae of lattice degeneration.
Retinal tears along the posterior and lateral edges of areas of lattice degeneration may occur at the time of an acute posterior vitreous detachment and would necessitate treatment to prevent worsening of a retinal detachment.
Round, atrophic holes within areas of lattice degeneration may exist but only require treatment if symptomatic, such as symptoms of flashes or floaters, if associated with a localized accumulation of sub-retinal fluid (localized retinal detachment) or in patients with personal or family history of retinal detachment from atrophic holes (in the patients’ other eye). Most round holes are solitary, although multiple holes may be present within a lattice lesion. Round holes have been reported in 6 to 18% of lattice lesions in clinical studies.
Diagnosis
Lattice degeneration is diagnosed using special equipment including an indirect ophthalmoscope, a 20-diopter lens and a metal instrument (to push on the eye) called a scleral depressor.
A procedure called scleral depression is utilized in order to best visualize the peripheral retina while performing indirect ophthalmoscopy. The pupil of the eye must be adequately dilated with phenylephrine hydrochloride ophthalmic solution 2.5% or 10%, Tropicamide 1% and sometimes Cyclogyl 1% or 2% (for surgical procedures) for best visualization of the peripheral retina.
Treatment
Lattice degeneration alone does not need specific treatment unless there occur holes (with associated sub-retinal fluid or symptoms such as flashes of lights or floaters), retinal tears or retinal detachment.
Treatment involves direct or indirect laser treatment to the area surrounding the lattice or the retinal hole, tear or detachment. Circumferential laser treatment assures a reduced risk of progression of the retinal detachment.
There is no treatment to reverse lattice degeneration. In addition, the correction of myopia with refractive surgery (LASIK, PRK, etc.) or cataract surgery will NOT reverse or reduce a patient's risk of progression of lattice degeneration in forming retinal holes, tears or detachment.