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Central disruption of fusion refers to a subject's inability to fuse images, resulting in constant diplopia. Severely reduced vergences, or vergence anomalies, producing markedly decreased fusional amplitudes resembling fusional disruption have not been reported previously with convergence insufficiency. We report 3 patients with severe vergence anomalies in the setting of convergence insufficiency.

Editor,—Asthenopia is characterised by ocular fatigue, frontal headache, and blurred vision, particularly during periods of sustained close work.1 It can be caused by accommodative insufficiency, a condition in which the effort required to maintain accommodation for near objects produces troublesome symptoms. This may be associated with a low accommodative convergence: accommodation (AC:A) ratio, which the patient has to overcome using positive fusional reserves. When fusion is insufficient symptoms of asthenopia can occur. In contrast, a high AC:A ratio would not normally be associated with asthenopia, but rather with overconvergence, potentially resulting in a convergence excess type of esotropia.2 We report two cases in which “pseudo-accommodative insufficiency” was identified as the cause of asthenopia and paradoxically associated with a high …

AIMS/BACKGROUND—The basis of binocular single vision in microtropia remains a matter of contention. This paper discusses the implications of recovery, in a group of primary microtropes following treatment, in relation to current concepts on the aetiology of the condition and proposed retinocortical correspondence. METHODS—Nine previously untreated primary microtropes whose condition resolved, were reviewed in detail to assess the patterns of change in retinal correspondence, uniocular fixation, stereoacuity, and visual acuity in response to treatment. RESULTS—Anomalous retinal correspondence (ARC), a central scotoma, reduced or absent stereoacuity, amblyopia, and uniocular eccentric fixation were present in all patients before treatment. Following treatment, all cases attained normal retinal correspondence (NRC), elimination of the central scotoma, stereo acuity levels of between 20 and 40 seconds of arc, 6/5 Snellen visual acuity in both eyes, and foveal fixation in both eyes. CONCLUSION—A hypothesis is put forward that for the patients described, a period of normal development is likely to have preceded the onset of microtropia, during which the retinocortical "foundations" for NRC were established. Precise pairing of foveo-foveal receptive fields was not abolished by the presence of amblyopia and a central scotoma, but this relation was temporarily suspended and binocular single vision was sustained via the neural substrate of paired receptive fields over a wide retinocortical area. Keywords: anomalous retinal correspondence; stereoacuity; retinocortical connections

BACKGROUND/AIMS—Microtropia is believed to be a static condition, in which accepted achievable levels of vision are those of 6/12-6/9 maximum, with the inability to achieve "normal" levels of stereopsis. The aim of this paper was to present the results of treatment of 30 consecutively presenting primary microtropes, and assess their outcomes using a more active treatment strategy than that conventionally used. METHODS—Visual acuity, stereoacuity, fixation, and the presence of a central suppression scotoma were assessed in all patients before, during, and after treatment, which comprised wearing maximum refractive correction, and an occlusion strategy aiming for equal visual acuity. RESULTS—Equal visual acuity of 6/5 Snellen was achieved in 43% of the 30 patients, while 87% achieved 6/9 Snellen or better visual acuity in the microtropic eye. Stereoacuity of better than 60" of arc was attained in 37%, and foveal fixation on visuscopy in 55%. The treatment outcome was not affected by the patient's age, initial visual acuity, or the amount of anisometropia. A change in the patient's diagnosis was noted in 50%, with nine patients recovering completely. CONCLUSIONS—The results show that microtropia is not static. Equal 6/5 vision is attainable, as is high grade stereoacuity. The pattern of fixation may change during treatment and elimination of the microtropia is possible in some cases. There is a requirement for management protocols to be changed in order to treat this condition more effectively. Keywords: microtropia; amblyopia; eccentric fixation