Diagnosis
The diagnosis is made by x-ray/MRI appearance and has five juxta-articular classifications and forehead, neck, and shaft classifications indicating early radiological signs.Early on there is flattening of articular surfaces, thinning of cartilage with osteophyte (spur) formation. In juxta-articular lesions without symptoms, there is dead bone and marrow separated from living bone by a line of dense collagen. Microscopic cysts form, fill with necrotic material and there is massive necrosis with replacement by cancellous bone with collapse of the lesions.The following staging system is sometimes useful when managing lesions. Stage 0 - Intravascular coagulation
Stage 1 - Dead bone without repair
Stage 2 - Dead bone with repair but without collapse
Stage 3 - Dead bone with repair and with collapse
Stage 4 - Secondary degenerative arthritisIn a study of bone lesions in 281 compressed air workers done by Walder in 1969, 29% of the lesions were in the humeral head (shoulder), 16% in the femoral head (hip), 40% in the lower end of the femur (lower thigh at the knee) and 15% in the upper tibia (knee below the knee cap). Worsening of the condition from continued decompression in an asymptomatic x-ray finding may occur. Prevention
Prevention is a more successful strategy than treatment. By using the most conservative decompression schedule reasonably practicable, and by minimizing the number of major decompression exposures, the risk of DON may be reduced. Prompt treatment of any symptoms of decompression sickness (DCS) with recompression and hyperbaric oxygen also reduce the risk of subsequent DON. Treatment
Treatment is difficult, often requiring a joint replacement.
In difficult cases, "cycloplegic agents are highly favored to break spasm quickly and may be more economical compared to other conventional therapies"Cyclopentolate, Atropine, Tropicamide, and Homatropine are the typical cycloplegic eye drops used once daily to treat spasm of accommodation by relaxing the ciliary muscle. One side effect is blurred vision since these induce dilation. Vision Training
Vision therapy administered by a trained optometrist has shown a success rate of over 70%. Surgery
Multifocal intraocular lens implantation is a new possible treatment involving clear lens extraction and multifocal intraocular lens implantation but it may not be appropriate for patients who have had resistant spasm of accommodation for a long period of time. Research
Experimental Nitroglycerin and Nitric Oxide
Animal studies have found nitroglycerin, a vasodilator used to treat angina, relaxes the ciliary muscle and may hold hope for those suffering from spasm of accommodation. Nitroglycerin is currently being investigated as a treatment for glaucoma, and has shown to decrease intraocular pressure and relax the ciliary muscle. According to Investigative Ophthalmology & Visual Science Journal. "In a nonhuman primate study, topical administration of nitroglycerin at a dose of 0.1% significantly decreased IOP in normotensive animals after 90 minutes". Further, according to Wiederholt, Sturm, and Lepple-Wienhues, "The data indicate (indicates [sic]) that an increase of intracellular cGMP by application of cGMP and organic nitrate or non-nitrate vasodilators induces relaxation of the bovine trabecular meshwork and ciliary muscle". Experimental Perilla frutescens
Since spasm of accommodation is a result of contraction of the ciliary muscle, the goal would be to relax the ciliary muscle.