The Retina Reference

Congenital Optic Nerve Head Pits

What You Should Know About Congenital Optic Nerve Head Pits By David J. Browning, MD, PhD An optic pit is a congenital abnormality of the optic nerve, which connects the eye to the brain. The optic nerve inserts into the back of the eyeball as shown in the anatomic diagram in figure 1. The insertion of the nerve into the back of the eye is called the optic disk. This disk usually has a small indentation called the optic cup. An optic pit is an excessively deep, excavated area in the optic nerve. During embryonic life, the normal migration and modeling of tissues fails to occur, although the reasons why are not known. In some cases a family history of optic pits is evident, and there is an association of mutations in the PAX2 and PAX6 genes in some cases. Below, figure 2 shows a normal optic nerve, while figure 3 shows an optic pit. Optic pits occur in approximately one in 11,000 births. Eighty-five percent are unilateral. The optic pit alone does not cause any visual disturbances. Rather, blurred vision develops when fluid from the vitreous cavity flows through the pit and splits the layers of the macula, the central part of the retina that enables reading vision. Such a splitting of the retina is called a retinoschisis, and over time the fluid may dissect outward and collect under the retina as a retinal detachment. It is estimated that 50% of eyes with optic pits will eventually develop macular detachment in this way. What Can Be Done for Optic Pits? For patients with optic pits and no visual symptoms, nothing needs to be done other than periodic monitoring. When vision decreases because of subretinal fluid, there are various treatment alternatives. The first alternative is a period of observation. Up to 25% of cases have spontaneous reabsorption of subretinal fluid, which may occur when the vitreous attachment to optic disk releases, a change that occurs naturally with aging.(1) More aggressive interventions include laser treatment at the edge of the optic nerve head to block passage of fluid from the pit to the macula. This works perhaps half the time. Failures can be treated with injection of gas into the eye or an operation called vitrectomy in which the vitreous humor is removed and replaced with a temporary gas bubble.(2) In both of these treatments the patient must keep the face down for a period of time to allow the gas to press against the pit and block fluid flow through the pit into the subretinal space. Some patients fail all treatments and end up with scarring of the macula. Poor vision may be the final outcome of these severe cases, but not blindness. If you are interesting in finding more information on your own, about this and other medical conditions, we recommend the excellent database of the National Library of Medicine, accessible at Reference List (1) Patton N, Aslam SA, Aylward GW. Visual improvement after long-standing central serous macula detachment associated with an optic disk pit. Graefes Arch Clin Exp Ophthalmol 2009; 246:1083-1085. (2) Akiyama H, Shimoda Y, Fukuchi M, Kashima T, Mayuzumi H, Shinohara Y et al. Intravitreal gas injection without vitrectomy for macular detachment associated with an optic disc pit. Retina 2014; 34:222-227. By David J. Browning, MD, PhD