Refractive surgery and diplopia

Binocular vision alterations after refractive and cataract surgery: a review

To review binocular and accommodative disorders documented after corneal or intraocular refractive surgery, in normal healthy prepresbyopic patients. A bibliographic revision was performed; it included works published before 1st July 2017 where accommodation and/or binocularity was assessed following any type of refractive surgical procedure. The search in Pubmed yielded 1273 papers, 95 of which fulfilled the inclusion criteria. Few publications reporting binocular vision and/or accommodative changes after refractive surgery in normal subjects were found. The reduction in fusional vergence is the most frequently reported alteration. Anisometropia is an important risk factor for postoperative binocular vision-related complaints. Most diplopia-related visual complaints, irrespective of the surgical procedure, were in fact misdiagnosed preoperative disorders. The preoperative evaluation of patients seeking spectacle/contact lens independence should include a complete binocular and accommodation assessment where parameters such as the phoric posture, accommodative amplitude and facility, near point of convergence, fusional reserves and accommodative convergence/accommodation coefficient are measured. This would allow the identification of risk factors that could compromise the success of the refractive surgery and cause clinical symptoms.

Strabismus After Ocular Surgery

Many types of ocular surgery can cause diplopia, including eyelid, conjunctival, cataract, refractive, glaucoma, retinal, and orbital surgery. Mechanisms include direct injury to the extraocular muscles from surgery or anesthesia, scarring of the muscle complex and/or conjunctiva, alteration of the muscle pulley system, mass effects from implants, and muscle displacement. Diplopia can also result from a loss of fusion secondary to long-standing poor vision in one eye or from a decompensation of preexisting strabismus that was not recognized preoperatively. Treatment, which typically begins with prisms and is followed by surgery when necessary, can be challenging. In this review, the incidence, mechanisms, and treatments involved in diplopia after various ocular surgeries are discussed. [J Pediatr Ophthalmol Strabismus. 2017;54(5):272-281.].

Interocular evaluation of axial length and retinal thickness in people with myopic anisometropia

PURPOSE

To investigate the changes in axial length and retinal thickness and their relationships with myopia in highly myopic anisometropia.

METHODS

A total of 87 Chinese subjects (25.28±11.98 years, mean±SD) were divided into two groups: anisometropia (n=38) and nonanisometropia (n=49). All eyes were measured for axial length, refractive status, and macular thickness (optical coherence tomography). Ocular biometric results were compared between eyes of subgroups. Linear correlation between refractive error and other biometric results was performed.

RESULTS

In the anisometropic group, the inner ring macula and part of the outer ring macula (nasal and inferior quadrants) in the higher myopic eyes were significantly thinner than in the fellow eyes (P≤0.007), but the foveal thickness (minimum and average) was similar (P≥0.050) between the two eyes. However, the minimum and average foveal thicknesses were found to be significantly thicker in the highly myopic eyes than those in the emmetropic to moderate myopic eyes (P≤0.016) in the nonanisometropic group. Among the eyes ranging from emmetropia to high myopia, the refractive error was negatively correlated to the axial length of the eye (P<0.001) and the thinning of inner ring macula is consistent with the increase in both myopia and axial length. There was a negative correlation in refractive error and axial length but no correlation in parafoveal thickness between eyes of the same subjects (P<0.001) in the anisometropic group.

CONCLUSIONS

In people with myopic anisometropia, the higher myopic eye has a longer axial length but a thinner parafoveal region than its fellow eye. The axial growth in the development of high myopia seems to be centrally regulated; however, the changes in parafoveal thickness are likely manipulated by local mechanisms within the eye.

Strabismus following implantable anterior intraocular lens surgery

Strabismus in adults is increasing and has recently become an important focus of attention due to the development of refractive surgery techniques. In this case, permanent strabismus developed in a woman with previous high myopia after implantable anterior intraocular lens surgery. An ophthalmologic examination revealed the presence of a lens which was placed slightly downward in relation to the center of visual axis in the anterior chambers and up-drawn pupils in both eyes. The prismatic effect due to lens decentration may be the main cause of strabismus. Therefore, we suggest precise intraocular lens insertion and placement technique during surgery as well as careful ophthalmologic assessment including cover/uncover tests in all candidates for refractive surgery and full ocular motility evaluation if there is any doubt about binocular issues.

[Strabismus and diplopia after refractive surgery]

OBJECTIVE

To evaluate factors that may decompensate a strabismus or lead to diplopia after refractive surgery.

METHODS

Retrospective study of 19 patients, who presented with binocular decompensation after refractive surgery. Mean age at surgery was 38.89 SD 10.26 (27-63) years. Fourteen patients were myopic, 5 hyperopic, and 5 of them had a marked anisometropia. The photo-refractive keratectomy procedure was used in 3 cases, laser-assisted in situ keratomileusis (LASIK) in 13, posterior chamber-IOL)+LASIK in one of them, and bilateral IOL in 2 cases.

RESULTS

There was a prevalence of strabismus of 0.12%. All of our patients had a binocular pathology previous to the refractive surgery. After surgery, 11 patients had an esophoria or esotropia, 3 exophoria or exotropia, 2 vertical deviations, and 3 horizontal and vertical deviations. Several factors often worked simultaneously in the same patient, such as: residual accommodation, refractive overcorrection (hyperopia), visual instability or anisoacuity, high myopia and phoria decompensation, elimination of suppression, dominance change, and a presbyopic age.

CONCLUSIONS

All of our patients had a previous binocular pathology. Binocularity may decompensate by several factors but mostly by myopic overcorrection, accommodation and visual factors, particularly in patients close to or in presbyopic age, in anisometropia and high myopia.

Diplopia associated with refractive surgery

When diplopia occurs after refractive surgery, a systematized approach to diagnosis and treatment is useful. First, determine if the problem is monocular or binocular. Monocular diplopia usually is caused by anterior segment complications and should be referred to an anterior segment surgeon. If the problem is binocular, determine if there is iatrogenic monovision. If monovision was created by the refractive surgery, determine if the double vision is due to fixation switch diplopia. If so, the monovision state needs to be reversed. If fixation switch is not the cause of the symptoms, try "optical rescue". If monovision is not present, check old refraction and motility records, and correct any residual refractive error. Strabismus may need to be treated with surgery, orthoptic exercises, or prisms.

Visual outcomes of LASIK-induced monovision in myopic patients with presbyopia

PURPOSE

To evaluate binocular visual acuity (VA), contrast sensitivity, and stereopsis in myopic patients after laser in situ keratomileusis (LASIK)-induced monovision.

DESIGN

Prospective, observational study.

METHODS

We performed a prospective study of 37 consecutive patients older than 45 years who underwent bilateral myopic LASIK with planned monovision. At the 6-month postoperative visit, we evaluated distance and near binocular visual acuity, contrast sensitivity, and stereopsis. Binocular tests were done without spectacles (in monovision condition) and compared with the results obtained by repeating the same binocular tests with the same patients (serving as a control group) after spectacle correction of the residual myopic defect in the nondominant eye for distance tests (reverting monovision) and after spectacle correction of the presbyopia bilaterally for near tests (near best spectacle-corrected VA).

RESULTS

By inducing a mean residual spherical equivalent defect of -0.97 diopter in the nondominant eye, the patients achieved a mean near binocular uncorrected visual acuity (UCVA) of 0.74, a mean reading test binocular UCVA of 0.88 using an acceptable spontaneous reading distance (48 cm), and a mean distance binocular UCVA of 1.08. A slight decrease in contrast sensitivity and stereopsis was observed in monovision compared to full distance correction.

CONCLUSIONS

Monovision is a valid option for myopic patients with presbyopia who are considering LASIK. Good distance and near UCVAs can be obtained with this procedure.

Effect of refractive surgery on binocular vision and ocular alignment in patients with manifest or intermittent strabismus

OBJECTIVE

To evaluate the effect of refractive surgery on binocular vision and ocular alignment in patients with manifest or intermittent strabismus, with or without vertical component.

SETTING

University Hospital Antwerp, Edegem, Belgium.

PATIENTS AND METHODS

13 patients (22 eyes) with strabismus underwent refractive surgery. Five of these patients presented with an esotropia and four of them with a small vertical deviation. Five patients had a manifest exotropia, of whom two presented with a small vertical deviation. Two patients had an intermittent exotropia with binocular vision, of whom one patient had a vertical deviation. One patient had a hypertropia with a dissociated vertical deviation.

RESULTS

Ocular alignment and binocular function remained unchanged postoperatively in all except two patients with high anisometropia who experienced an improvement in binocular function. In these patients, the preoperative manifest deviation became intermittent or latent after surgery, allowing fusion and stereopsis. Vertical deviation was found preoperatively in 8 of the 13 patients. This vertical deviation remained unchanged postoperatively, but improved in one patient with anisometropia.

CONCLUSION

Preoperative intermittent or manifest strabismus is not a contraindication for refractive surgery provided some specific recommendations are taken into account, such as an adequate preoperative orthoptic examination and aiming at emmetropia for both eyes.

Refractive Surgery in Patients With High Myopic Anisometropia

PURPOSE

To assess the efficacy and safety of LASIK in patients with high myopic anisometropia and to provide specific screening guidelines for anisometropic patients undergoing refractive surgery.

METHODS

Twenty-six eyes of 16 patients with high myopic anisometropia (>3.0 diopters) were enrolled in this study. Complete pre- and postoperative ophthalmologic and orthoptic examinations were performed. The preoperative orthoptic examination was done with glasses and contact lenses. Twenty-two eyes of 13 patients underwent uncomplicated LASIK; the second eye was treated 2 weeks after the first eye. Patients were examined 1 day, 7 days, and 1, 3, 6, and 12 months after surgery.

RESULTS

Thirteen patients obtaining good results at red glass bar test (RGB) underwent LASIK without postoperative diplopia; four showed an improvement of the sensorial assessment. Three patients were excluded from surgery because of diplopia with RGB values <4 to 5. LASIK temporarily induced diplopia in the suppressed eye of one patient; however, the diplopia disappeared after surgery of the fixating eye.

CONCLUSIONS

Patients with high myopic anisometropia and a weak sensorial state who undergo refractive surgery may be at risk for postoperative diplopia. We suggest clinical guidelines to reduce the occurrence of this complication.

Refractive surgery and strabismus

This review discusses the potential for strabismic complications after refractive surgery for hyperopia, myopia, anisomyopia, astigmatism and monovision, and how to avoid these complications. Guidelines are given for assessing patients with strabismus seeking refractive surgery. Screening tests are suggested that lead to stratification of refractive surgery patients into different risk groups each warranting a different intensity of evaluation.

Binocular vision impairment after refractive surgery

PURPOSE

To illustrate the need for an accurate preoperative orthoptic examination to prevent postoperative changes in binocular vision.

SETTING

Department of Ophthalmology, University Hospital Antwerp, Edegem, Belgium.

METHODS

Five patients presenting major subjective complaints after refractive surgery were analyzed.

RESULTS

In 1 patient, a latent N IV palsy decompensated after laser in situ keratomileusis (LASIK) in the more myopic eye to achieve monovision. A second patient, operated on for N IV palsy 10 years earlier, presented a recurrence of the palsy after bilateral LASIK for myopia. The third patient complained of discomfort in binocular vision caused by aggravation of a preexisting intermittent esotropia that worsened after LASIK for hyperopia. The fourth patient complained of diplopia after LASIK in the highly anisometropic and exotropic eye. The fifth patient experienced a decrease in fusion and stereopsis at the time he became anisometropic after bilateral LASIK.

CONCLUSIONS

Special care should be taken of patients who have a preoperative history of strabismus surgery, an overcorrection or undercorrection in 1 or both eyes, or anisometropia and of those who are unhappy with contact lenses. An orthoptic examination should be done with and without spectacle correction to detect underlying vertical phorias. Intended monovision should be examined initially using contact lenses.