Decompensated strabismus after laser in situ keratomileusis

Diplopia and Strabismus After Corneal Refractive Surgery

INTRODUCTION

Diplopia and strabismus are known complications after corneal refractive surgery (CRS). Within the U.S. Armed Forces, refractive surgery is used to improve the operational readiness of the service member, and these complications could cause significant degradation to their capability. This study was performed in order to identify the incidence of strabismus and diplopia following CRS within the U.S. Military Health System.

METHODS

A retrospective review of all patients who underwent photorefractive keratectomy (PRK) or laser-assisted in situ keratomileusis (LASIK) in the Department of Defense from January 2006 through September 2013 was designed and approved by the Naval Medical Center Portsmouth Institutional Review Board. The military health system data mart was queried for all patients who underwent one of these procedures and subsequently had an International Classification of Disease-9 code for any strabismus or diplopia through 2014 allowing at least 1 year of follow-up. We then calculated the incidence of both diplopia and strabismus for these procedures as the primary measure and the overall prevalence as a secondary measure.

RESULTS

A total of 108,157 patients underwent PRK or LASIK during our study period with 41 of these patients subsequently having a diagnosis of diplopia or strabismus. After chart review, 16 of these patients were excluded resulting in 25 patients for inclusion in either the strabismus (23 patients, 0.02%) or diplopia (3 patients, 0.003%) cohorts with one patient having both. Of the 23 patients with postoperative strabismus, 4 were new cases giving an incidence of 0.004% and 2 new cases of diplopia for an incidence of 0.002%.

CONCLUSION

Diplopia and strabismus are rare complications after CRS in the U.S. military population. These procedures continue to increase the operational readiness of our service members with minimal risk of these potentially debilitating complications. Overall, this study provides support for the continued use of PRK and LASIK despite study limitations related to the use of large databases for retrospective review. Future prospective studies using delineated preoperative and postoperative examinations with sensorimotor testing included may be able to resolve the limitations of this study.

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.].

Impact of laser refractive surgery on ocular alignment in myopic patients

PURPOSE

To evaluate the impact of myopic keratorefractive surgery on ocular alignment.

METHODS

This prospective study included 194 eyes of 97 myopic patients undergoing laser refractive surgery. All patients received a complete ophthalmic examination with particular attention to ocular alignment before and 3 months after surgery.

RESULTS

Patients with a mean age of 26.6 years and a mean refractive error of -4.83 diopters (D) myopia were treated. Asymptomatic ocular misalignment was present preoperatively in 46 (47%) patients: a small-angle heterophoria (1-8 prism diopters, PD) in 36%; and a large-angle heterophoria (>8 PD)/heterotropia in 11%. Postoperatively, the change in angles of 10 PD or greater occurred in 3% for distance and 6% for near fixation: in 7% of the patients with orthophoria, in 3% of those with a small-angle heterophoria, and in 18% of those with a large-angle heterophoria/heterotropia. No patient developed diplopia. The preoperative magnitude of myopia or postoperative refractive status was not related to the change in ocular alignment. The higher anisometropia was associated with a decrease in deviation (P=0.041 for distance and P=0.002 for near fixation), whereas the further near point of convergence tended to be related with an increase in near deviation (P=0.055).

CONCLUSIONS

Myopic refractive surgery may cause a change in ocular alignment, especially in cases with a large-angle heterophoria/heterotropia. There is also a chance of improvement of misalignment in patients with anisometropia.

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.

Diplopia after laser in situ keratomileusis (LASIK) in a patient with a history of strabismus

In patients with a history of strabismus, refractive surgery can result in decompensation of ocular alignment, with subsequent diplopia. Refractive surgery in the management of strabismus has been described, although it remains controversial. We present a young adult with past history of strabismus surgery and new-onset diplopia after refractive surgery. Binocular diplopia was treated surgically with laser in situ keratomileusis.

[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.

Strabismus precipitated by monovision

PURPOSE

To present patients who had the onset of strabismus or the recurrence of strabismus after converting to a monovision system of seeing.

DESIGN

Retrospective interventional case series.

METHODS

Clinical records of 12 patients from the private practice of the corresponding author of this paper (Z.F.P.) were reviewed. Patients obtaining monovision via contact lenses, LASIK, and cataract surgery with posterior chamber intraocular lenses were studied if their monovision produced a new strabismus or was related to the recurrence of a previous strabismus.

RESULTS

All patients were first treated by converting the monofixing near eye to distance vision and then using reading glasses for near work. Of the 12 patients, 7 regained their fusion by doing away with monovision and 5 required surgery to reestablish motor or sensory control. All of the surgery patients obtained an excellent alignment but 1 did not regain sensory fusion.

CONCLUSION

Monovision is successful for the far majority of patients who try it. However, in patients with a previous history of strabismus or those with significant phorias, caution should be used in recommending monovision, and if monovision is elected, keeping the anisometropia to small levels such as 1.25 to 1.50 diopters (D) might lessen the chance of producing strabismus post monovision. The majority of our patients developed strabismus after 2 years of monovision, telling us that while a trial of monovision with a contact lens prior to surgery may suggest that the patient could tolerate monovision, it is not a guarantee.

Refractive surgery: a treatment for and a cause of strabismus

PURPOSE OF REVIEW

The purpose of this article is to review refractive surgery as a means of treatment for strabismus and as a potential cause of strabismus and binocular diplopia.

RECENT FINDINGS

Numerous studies have reported that refractive surgery is effective in correcting certain types of strabismus such as accommodative and partially accommodative esotropia. Studies on the treatment of exotropia related to anisometropia have demonstrated less favorable outcomes. In patients without manifest strabismus preoperatively, recent studies have shown that strabismus and diplopia can occur after refractive surgery. Appropriate clinical testing and risk stratification are essential to determine whether a patient is at increased risk for postoperative strabismus and diplopia.

SUMMARY

Refractive surgery can be useful in patients with accommodative and partially accommodative esotropia. A thorough history and clinical examination is extremely important to expose potential risk factors in all patients undergoing refractive surgery. Based on the designated risk level, more advanced testing may be warranted.

Diplopia in adult patients following cataract extraction and refractive surgery

PURPOSE OF REVIEW

The purpose of this article is to report the incidence and cause of diplopia following cataract surgery and laser in-situ keratomileusis (LASIK).

RECENT FINDINGS

Ocular misalignment following cataract extraction with retrobulbar anesthesia has an incidence of approximately 7%. Diplopia ranges in this group of patients from 0.23 to 0.98%. The incidence of ocular misalignment decreases with topical anesthesia for cataract extraction to 5%, and diplopia occurs with an incidence of 0.21-0%. Although there are small case series, the incidence of diplopia following LASIK has not been reported. The causes of diplopia following cataract extraction and LASIK include decompensation of pre-existing strabismus, new-onset accommodative esotropia, concurrent onset of systemic disease, disruption of central fusion, and monocular diplopia. The leading cause for diplopia following retrobulbar anesthesia for cataract extraction is extraocular muscle paresis/restriction and is unique to this type of procedure. In cases of topical anesthesia for cataract extraction and for LASIK procedures, the leading cause of diplopia is decompensation of pre-existing strabismus.

SUMMARY

Detailed history and evaluation for pre-existing strabismus can dramatically decrease the incidence of unexpected diplopia following refractive procedures.

Diplopia and strabismus following ocular surgeries

Postoperative diplopia and strabismus may result from a variety of ocular surgical procedures. Common underlying mechanisms include sensory disturbance, scarring, direct extraocular muscle injury, myotoxicity from injections of local anesthesia or antibiotics, and malpositioning of extraocular muscles by implant materials. The most common patterns are vertical and horizontal motility disturbance. Treatment options include prisms, botulinum, occlusion, or surgery.

Monovision: a review

In presbyopia, patients can no longer obtain clear vision at distance and near. Monovision is a method of correcting presbyopia where one eye is focussed for distance vision and the other for near. Monovision is a fairly common method of correcting presbyopia with contact lenses and has received renewed interest with the increase in refractive surgery. The present paper is a review of the literature on monovision. The success rate of monovision in adapted contact lens wearers is 59-67%. The main limitations are problems with suppressing the blurred image when driving at night and the need for a third focal length, for example with computer screens at intermediate distances. Stereopsis is impaired in monovision, but most patients do not seem to notice this. These limitations highlight the need to take account of occupational factors. Monovision could cause a binocular vision anomaly to decompensate, so the pre-fitting screening should include an assessment of orthoptic function. Various methods have been used to determine which eye should be given the distance vision contact lens and the literature on tests of ocular dominance is reviewed. It is concluded that tests of blur suppression are most likely to be relevant, but that ocular dominance is not fixed but is rather a fluid, adaptive, phenomenon in most patients. Suitable patients can often be given trial lenses that allow them to experiment with monovision in real world situations and this can be a useful way of revealing the preferred eye for each distance. Of course, no patient should drive or operate machinery until successfully adapted to monovision. Surgically induced monovision is less easily reversed than contact lens-induced monovision, and is only appropriate after a successful trial of monovision with contact lenses.

Binocular vision and refractive surgery

Binocular status can have an effect on the outcome of refractive surgery. Some accommodative deviations and anisometropia can be managed effectively. Fully accommodative esotropia has been successfully treated in young patients but the outcome can be less predictable in older patients. High anisometropes are usually unaffected by the change in aniseikonia following refractive surgery but there are exceptions. Failure to recognise and appropriately classify a binocular vision anomaly pre-surgically can result in symptoms that are difficult to manage post-operatively. Refractive surgery producing a binocular vision anomaly where there was none pre-operatively is less common. I present a review of the literature discussing the relationship between binocular vision anomalies and refractive surgery, illustrating the findings with published reports of successful and unsuccessful binocular postoperative outcomes. I argue that predicting the binocular outcome should be considered pre-operatively for every refractive surgery patient.

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.

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.

Exodeviation following monocular myopic regression after laser in situ keratomileusis

We report a 44-year-old woman with intermittent left exotropia of 35 prism diopters at distance who initially exhibited alignment of both eyes after bilateral laser in situ keratomileusis (LASIK). The exophoria was not preserved due to myopic regression in the dominant eye. An uneventful LASIK treatment was performed to correct -11.00 -0.50 x 130 in the right eye and -13.50 -1.50 x 145 in the left eye. The aim was to achieve emmetropia in both eyes. Although an examination revealed exophoria at near and distance during the 6 months following refractive surgery, the tropic aspect of the divergent deviation appeared in the right eye following the myopic regression. Laser in situ keratomileusis is an effective option to achieve binocular visual quality in myopic anisometropic patients. However, myopic regression after LASIK may disrupt the binocular visual quality.

Laser in situ keratomileusis for myopia and astigmatism: safety and efficacy: a report by the American Academy of Ophthalmology

OBJECTIVE

This document describes laser in situ keratomileusis (LASIK) for myopia and astigmatism and examines the evidence to answer key questions about the efficacy and safety of the procedure.

METHODS

A literature search conducted for the years 1968 to 2000 retrieved 486 citations and an update search conducted in June 2001 yielded an additional 243 articles. The panel members reviewed 160 of these articles and selected 47 for the panel methodologist to review and rate according to the strength of evidence. A Level I rating is assigned to properly conducted, well-designed, randomized clinical trials; a Level II rating is assigned to well-designed cohort and case-control studies; and a Level III rating is assigned to case series and poorly designed prospective and retrospective studies, including case-control studies.

RESULTS

The assessment describes randomized controlled trials published in 1997 or later (Level I evidence) and more recent comparative and noncomparative case series (Level II and Level III evidence), focusing on results for safety and effectiveness. It is difficult to extrapolate results from these studies that are comparable to current practices with the most recent generation lasers because of the rapid evolution of LASIK technology and techniques. It is also difficult to compare studies because of variations in the range of preoperative myopia, follow-up periods, lasers, nomograms, microkeratomes and techniques, the time frame of the study, and the investigators' experience.

CONCLUSIONS

For low to moderate myopia, results from studies in the literature have shown that LASIK is effective and predictable in terms of obtaining very good to excellent uncorrected visual acuity and that it is safe in terms of minimal loss of visual acuity. For moderate to high myopia (>6.0 D), the results are more variable, given the wide range of preoperative myopia. The results are similar for treated eyes with mild to moderate degrees of astigmatism (<2.0 D). Serious adverse complications leading to significant permanent visual loss such as infections and corneal ectasia probably occur rarely in LASIK procedures; however, side effects such as dry eyes, night time starbursts, and reduced contrast sensitivity occur relatively frequently. There were insufficient data in prospective, comparative trials to describe the relative advantages and disadvantages of different lasers or nomograms.