Vol. 114, No. 6

Letters to The Journal

intraocular pressure decreased to 13 mm Hg in the right eye and 12 mm Hg in the left eye while the patient was instilling timolol 0.5% twice a day in both eyes. Both twins always had a higher intraocular pressure in the eye with the splinter hemorrhage and visual field defect when a difference between the two eyes existed. Recent results of static threshold perimetry in the parents were normal. The theories regarding the origin of lowtension glaucoma may be primarily grouped into vascular or structural theories. The occur­ rence of low-tension glaucoma in identical twins may be evidence for an inherited struc­ tural abnormality, perhaps in the collagen of the lamina cribrosa, with secondary axonal dys­ function contributing to the origin of this dis­ ease. Our patients are particularly interesting because their fellow eyes were the ones that developed optic disk splinter hemorrhages and visual field defects. Some investigators have suggested that the large size of the optic cups in the normal fellow eyes of patients with unilat­ eral low-tension glaucoma suggests that intra­ ocular pressure increase was not the major reason for their large optic cups. Our patients, likewise, had large cupping in the fellow eye. We suggest this as further evidence for a struc­ tural abnormality in the optic nerve, as some investigators have suggested for glaucoma. Other investigators have suggested a vascular origin for this disease. More likely, this is a disease with an origin associated with many factors of varying importance. Our case sug­ gests a congenital structural defect as another factor.

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5. Bennett, S. R., Alward, W. L. M., and Folberg, R.: An autosomal dominant form of low-tension glaucoma. Am. J. Ophthalmol. 108:238, 1989.

Impending Macular Hole Associated With Topical Pilocarpine William L. Benedict, M.D., and Michel Shami, M.D. Department of Ophthalmology and Visual Sciences, Texas Tech University Health Sciences Center. Inquiries to Michel J. Shami, M.D., Department of Ophthalmology, Texas Tech University Health Sciences Center, Lubbock, TX 79430. Rhegmatogenous retinal detachments and peripheral retinal tears have been associated with miotic therapy. 1 We treated a patient who developed a stage I-A macular hole (foveolar detachment) coincident with the initiation of pilocarpine therapy for glaucoma. The impend­ ing hole resolved after the pilocarpine was stopped. The patient was a 69-year-old white woman. Results of her initial macular examination by her referring ophthalmologist were normal. She was noted to have early glaucoma, and pilocarpine 2% in each eye, four times per day was started. One month later the patient re­ turned with complaints of blurred vision in the right eye. Her visual acuity was 20/20 bilateral­ ly. An impending macular hole was noted in the right eye and she was referred to us for further examination.

References 1. Rasmussen, D. H., and Ellis, P. P.: Congenital glaucoma in identical twins. Arch. Ophthalmol. 84:827, 1970. 2. Teikari, J. M., Airaksinen, P. J., Kaprio, J., and Koskenvuo, M.: Primary open-angle glaucoma in two monozygotic twin pairs. Acta Ophthalmol. 65:607, 1987. 3. Teikari, J. M.: Genetic factors in open-angle glaucoma. A population-based twin study. Acta Ophthalmol. 65:715, 1987. 4. Terkari, J. M., Kaprio, J., Koskenvuo, M., and Vannas, A.: Ophthalmic disease in twins. A nation­ wide record linkage study of hospital discharges and free medications for 1,667 twin pairs. Acta Genet. Med. Gemellol. (Roma) 36:523, 1987.

Fig. 1 (Benedict and Shami). Stage I-A macular hole one month after the initiation of topical pilocarpine. Note the absent foveal reflex and the small yellow spot centered in the fovea.

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AMERICAN JOURNAL OF OPHTHALMOLOGY

Our examination disclosed narrow chamber angles bilaterally and moderate nuclear sclerot­ ic lens changes. There was loss of the foveal reflex and a small yellow spot located centrally in the fovea of her right eye (Fig. 1). No associ­ ated posterior vitreal detachment was found. An epiretinal membrane was present at the surface of the left macula, and both retinas were peripherally unremarkable. The patient returned seven days later com­ plaining of intermittent halos surrounding lights. Her intraocular pressure was 20 mm Hg bilaterally and gonioscopy disclosed significant peripheral iridocorneal apposition in the right eye. A laser peripheral iridectomy was per­ formed. Ophthalmoscopy repeated three weeks later (one month after discontinuation of the pilocar­ pine) disclosed complete resolution of the im­ pending macular hole (Fig. 2). The posterior vitreous was still attached to the macula. Miotics have been associated with retinal tears, secondary retinal detachments, and mac­ ular hole formation. 2 The postulated mecha­ nism is that miotic-induced accommodation, which has been shown to result in an anterior shift of the posterior lens surface, 3 causes ante­ rior displacement of the vitreous. This results in anteroposterior vitreofoveal traction. Our patient developed a stage I-A macular hole (foveolar detachment) within one month after initiation of pilocarpine for glaucoma. One month after the miotic was stopped, in the absence of a posterior vitreous detachment, the impending hole resolved. The association of

the impending hole with the miotic therapy suggests a causal relationship. We believe that miotic-induced forward displacement of the vitreous placed traction on the fovea and caused a small foveal detachment. Removal of the miotic, and the resultant ciliary body relax­ ation, then relieved the vitreofoveal traction and allowed the retina to settle. The observation that impending macular holes are usually aborted if a posterior vitreal detachment occurs before the development of a full-thickness hole 4 supports this proposed mechanism for miotic-induced macular hole formation.

References 1. Kraushar, M. F., and Steinberg, J. A.: Miotics and retinal detachment. Upgrading the community standard. Surv. Ophthalmol. 35:311, 1991. 2. Garlikov, R. S., and Chenoweth, R. G.: Macular hole following topical pilocarpine. Ann. Ophthal­ mol. 10:1313, 1975. 3. Abramson, D. H., Coleman, D. J., Forbes, M., and Franzen, L. A.: Pilocarpine. Effect on the ante­ rior chamber and lens thickness. Arch. Ophthalmol. 87:615, 1972. 4. Gass, J. D. M.: Idiopathic senile macular hole. Its early stages and pathogenesis. Arch. Ophthalmol. 106:629, 1988.

The Association of Iridoschisis and Angle-recession Glaucoma John F. S a l m o n , F.C.Ophth. Department of Ophthalmology, University of Cape Town and Groote Schuur Hospital. Inquiries to John F. Salmon, F.C.Ophth., Department of Ophthalmology, Medical School, University of Cape Town, Observatory 7925, Cape Town, South Africa. The term iridoschisis describes a localized cleavage of the iris into two layers, with subse­ quent disintegration of the anterior leaf.1 Iri­ doschisis has been associated mainly with pri­ mary angle-closure glaucoma, but has also been described as an idiopathic iris atrophy of old age. 13 In three cases, iridoschisis was re­ ported secondary to ocular trauma and in one case in association with angle recession. 35

Fig. 2 (Benedict and Shami). Aborted macular hole in the same patient one month after the discontinua­ tion of pilocarpine. Note the resolution of the central yellow spot.

Case 1 A 54-year-old man had painful eyes and a history of gradual visual loss. He had had recurrent facial and ocular trauma as a young

Impending macular hole associated with topical pilocarpine.

Vol. 114, No. 6 Letters to The Journal intraocular pressure decreased to 13 mm Hg in the right eye and 12 mm Hg in the left eye while the patient wa...
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