The Normal Accommodative Convergence/Accommodation (AC/A) Ratio

The etiology, diagnostics, and treatment of the spasm of the near reflex - a narrative review

Physiological adaptation of the eye to the visual perception of near objects consists of the "near triad": convergence, accommodation, and pupil miosis. Normally, these tend to revert when one stops fixating on a near object. Spasm of the near reflex (SNR) is a pathological phenomenon, which manifests itself by the persistence of the above-mentioned adjustments, which prevents the eye from returning to its relaxed state. In this narrative review, we aim to summarize the etiology, diagnostics, treatment, and prevention of SNR. The literature review was performed by searching online databases. The clinical presentation of SNR is diverse; it presents as isolated accommodative spasm more frequently than impairment of all three components of the near triad. Patients usually present with fluctuations in visual acuity, blurred vision, diplopia, and asthenopia. The etiology is not fully understood. Potential causes include neuroanatomic, organic, and psychogenic disorders. The diagnosis is clinical, based on the constellation of symptoms and assessment of the near triad. The diagnostic golden standard is a cycloplegic examination of refraction, preferably using cyclopentolate hydrochloride (1%, 0.5%, or 0.1% solution). The first-line treatment requires the administration of a cycloplegic drug in combination with plus lenses, flipper lenses, optical fogging, or miotics. For secondary cases, causal treatment should be implemented. Prevention of SNR should be based on eliminating modifiable risk factors. We propose including screening for SNR symptoms in every ophthalmic examination, especially among patients with psychogenic or neural disorders, after brain trauma, or young adults spending much time in front of computer screens.

A comparison of visual discomfort experienced by surgeons in wireless versus conventional endoscopy in laparoscopic surgery

Background

This study was performed to introduce a new wireless endoscopic system. Research and development were based on fifth-generation transmission technology. Eye symptoms and visual discomfort induced by the novel endoscopic system were compared with those induced by the conventional endoscopic system before and during laparoscopic pelvic surgery.

Materials and methods

Twenty surgeons successfully conducted laparoscopic pelvic surgeries using a conventional endoscopic system and a wireless endoscopic system. Subjective and objective data were measured to evaluate visual discomfort before and 2 hours after surgery.

Results

In the conventional endoscopic and wireless endoscopic system groups, no significant differences were found in the presurgical or postsurgical questionnaires. In both groups, tear film breakup times significantly decreased after surgery. However, after comparing the 2 groups, no statistically significant difference was found.

Conclusions

Compared with the conventional endoscopic system, the novel wireless endoscopic system does not cause additional visual discomfort for experienced surgeons.

Changes in Accommodative and Binocular Function following Phakic Intraocular Lens for High and Low-to-Moderate Myopia

The aim was to evaluate accommodative and binocular function of phakic intraocular lens implantable collamer lens (ICL) in high and low-to-moderate myopia. Prospective comparative cohort study with 38 myopic patients who underwent ICL implantation were divided into two groups of 19 patients, each one based on the spherical equivalent (SE): high-power (SE ≤ −6 D) and low-to-moderate (SE > −6 D). The push-up amplitude of accommodation (AA), monocular accommodative facility (MAF), distance and near ocular deviation, near convergence amplitude, near point convergence (NPC), stereopsis, and accommodative convergence/accommodation (AC/A) ratio were assessed before surgery and 1 week and 1 month postoperatively. The mean residual refractive error at 1 month after surgery improved in both groups, 0.18 ± 0.34 D and 0.09 ± 0.26 D, respectively (p < 0.001). There was a significant decrease in AA in both groups between preoperatively and at 1-week (p = 0.001; p = 0.008, respectively) and 1-month follow-up (p = 0.001; p = 0.008). For the rest of the binocular measurements, no statistically significant postoperative changes were found in any group. This finding suggests follow-up studies on amplitude of accommodation in phakic intraocular lens ICL implantation.

Refractive correction regulated gradient AC/A ratio with low-to-moderate myopia in children and adolescents

Abnormal accommodative convergence per diopter of accommodative response (AC/A ratio) ratio is an important factor leading to myopia. This study aimed to examine the effect of refractive correction on the gradient of AC/A ratio with low-to-moderate myopia in children and adolescents. Children and adolescents aged 8-18 years, with low and moderate myopia, were divided into groups of myopia with no refractive correction and myopic continuous refractive correction of more than half a year. Then, in accordance with the myopia gradient, they were further divided into 0.00 to - 1.50, - 1.75 to - 3.00, - 3.25 to - 4.50, and - 4.75 to - 6.00 groups. Results showed that the AC/A ratio of the myopic group without refractive correction history was significantly higher than that with refractive correction history for more than half a year. The AC/A ratio increased with the deepening of myopia in the group without refractive history of myopia. However, it decreased significantly in the group with refractive history of myopia for more than half a year. Therefore, the AC/A ratio is related to the degree of uncorrected myopia, and it increases with the degree of uncorrected myopia.

Young patients with divergence insufficiency related to excessive near work

The purpose of this study is to explore the relationships between excessive near work and divergence insufficiency esotropia in young adults. A prospective study described a series of young patients with divergence insufficiency esotropia related to excessive near work between 2012 and 2017. The medical records of twelve young patients with divergence insufficiency esotropia and a history of excessive near work were reviewed, and the duration of near work, angle of primary position deviations at distance and at near, and angle of primary position deviations after refraining from near work for 3 months were analyzed. All patients with divergence insufficiency esotropia (age range: 21-35 years) showed an initial esodeviation ranging from 18 to 35 prism diopters for distance fixation and ranging from 8 to 20 prism diopters for near. Neurological evaluation in all cases was normal. Myopic refractive errors were detected in twelve patients. Every patient persisted near work for more than 6 h a day over a period of several months (minimum 4 months). Reductions in esodeviation were noted in twelve patients after refraining from near work for more than 3 months. Only one patient was diplopia free in all positions of gaze. The remaining eleven patients were treated successfully, six with prisms and five with surgery. They were all orthophoric and demonstrated restored binocularity at the post-treatment examinations. Our findings suggested that excessive near work might influence the development of divergence insufficiency esotropia in young adults. Refraining from excessive near work could decrease the degree of esodeviation in these patients.