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.
One side effect of cycloplegic drops is that they often have BAK as a preservative ingredient, which, with daily use, can erode the tear shield:

At each administration of an eye drop containing benzalkonium chloride, its detergent effect disrupts the lipid layer of the tear film. This cannot be regenerated and can no longer protect the aqueous layer of the tear film, which evaporates easily. In these circumstances, the cornea is exposed and eye dryness occurs. In addition, benzalkonium chloride has a cellular toxicity on caliciform cells, entailing a reduction in the amount of mucin, an additional reason for disrupting the tear film. In fact, none of the cycloplegic drops used to treat Spasm of Accommodation in the United States are available without BAK. This unfortunately makes treatment much more difficult as the side effect of dry eyes and corneal damage can occur. France, Australia, Canada, and the United Kingdom do have limited availability of BAK-free eye drops available in unidose, and they must be imported to the United States with a physicians letter to the FDA enclosed with the imported prescription. Due to the high potential of tear shield damage with long-term use and the associated dry eye condition caused by cycloplegic eye drops with BAK (preservative), many physicians do not recommend cycloplegic eye drops.