Strabismus precipitated by monovision

Femtosecond LASER-Assisted Double Intraocular Lens Exchange in Nanophthalmic Eyes

Introduction

Though patients with nanophthalmos frequently endure decreased quality of vision with contact lenses or spectacles, refractive surgery is generally an inadequate alternative due to the associated high refractive error. A refractive lens exchange (RLE) is an alternative option but is technically challenging, requiring accuracy in biometry measurements and procedures.

Case Presentation

This case discusses a 27-year-old female with nanophthalmos (axial lengths 17.6 mm and 17.4 mm, right and left eyes, respectively) who underwent a femtosecond laser-assisted (FLA) RLE with simultaneous implantation of a monofocal and a Sulcoflex trifocal (Rayner, Britain) lens in each eye. Preoperative cycloplegic refraction was +11.50/-0.75 × 145 and +12.00/-1.00 × 35 in the RE and LE, respectively. Best-corrected visual acuity (BCVA) at distance and near in the RE and LE was 6/7.5 and J1, 6/8.5 and J2, respectively. Uncorrected visual acuity (UCVA) was >6/120 and >J14 for each eye. FLA RLE was performed in the RE, then in the LE 2 weeks later. In each eye, a monofocal (44.0 D, RE, and LE) and a Sulcoflex trifocal lens (both implants, Rayner, Britain) were implanted in one procedure. Distance and near UCVA measured 6 weeks post-op RE and 1-month post-op LE at 6/8.5 and J1 in the RE, 6/10 and J1 in the LE. The RE and LE refraction and BCVA were +0.50/-1.00 × 115, 6/7.5, and plano/-1.00 × 55, 6/8.5, respectively. The post-op outcomes were uneventful.

Conclusion

A single procedure concurrently implanting a monofocal and Sulcoflex trifocal intraocular lens in nanophthalmic eyes resulted in an excellent UCVA. This procedure can be considered esthetic and reconstructive as it significantly improves patient appearance and function.

Frequency and Etiologies of Visual Disturbance After Cataract Surgery Identified in Neuro-Ophthalmology Clinics

BACKGROUND

To identify the frequency and etiologies of visual disturbances after cataract surgery in patients referred to Neuro-ophthalmology.

METHODS

This study is a retrospective chart review. Records of patients 18 years and older referred to neuro-ophthalmology clinics for new-onset visual disturbances within 6 months of cataract surgery were reviewed. Those with pre-existing neuro-ophthalmic disorders, combined intraocular procedures with cataract surgery, or inadequate follow-up were excluded. The main outcome measures were frequency and etiologies of visual disturbances after cataract surgery. Secondary analyses of a cohort of patients who had cataract surgery at our institution were performed to determine the frequency and etiology of visual disturbances after uneventful cataract surgery.

RESULTS

One hundred seventy-three patients met the inclusion criteria (internal referral: 36/173, from outside surgeons: 137/173). Sixty-one percent (106/173) were newly diagnosed with neuro-ophthalmic etiologies, including 21% (36/173) with afferent and 40% (70/173) with efferent disorders. Thirty-six percent (62/173) of patients had non neuro-ophthalmic causes and 3% (5/173) had systemic conditions responsible for visual disturbances postoperatively. Decompensated strabismus causing diplopia was the most common neuro-ophthalmic diagnosis after cataract surgery (50%, 53/106). Of the 13,715 patients who had cataract surgery performed at our institution over a 9-year period, 20 of 36 patients referred for visual disturbances were identified with neuro-ophthalmic etiologies of which 85% (17/20) had postoperative diplopia.

CONCLUSIONS

In our study, decompensated strabismus causing diplopia was the most common neuro-ophthalmic visual disturbance after cataract surgery. Detailed history and ocular alignment should be assessed before cataract surgery to identify patients with the risk.

Correcting Presbyopia With Autofocusing Liquid-Lens Eyeglasses

OBJECTIVE

Presbyopia, an age-related ocular disorder, is characterized by the loss in the accommodative abilities of the human eye. Conventional methods of correcting presbyopia divide the field of view, thereby resulting in significant vision impairment. We demonstrate the design, assembly and evaluation of autofocusing eyeglasses for restoration of accommodation without dividing the field of view.

METHODS

The adaptive optics eyeglasses comprise of two variable-focus liquid lenses, a time-of-flight range sensor and low-power, dual microprocessor control electronics, housed within an ergonomic frame. Subject-specific accommodation deficiency models were utilized to demonstrate high-fidelity accommodative correction. The abilities of this system to reduce accommodation deficiency, its power consumption, response time, optical performance and MTF were evaluated.

RESULTS

Average corrected accommodation deficiencies for 5 subjects ranged from -0.021 D to 0.016 D. Each accommodation correction calculation was performed in ∼67 ms which consumed 4.86 mJ of energy. The optical resolution of the system was 10.5 cycles/degree, and featured a restorative accommodative range of 4.3 D. This system was capable of running for up to 19 hours between charge cycles and weighed ∼132 g.

CONCLUSION

The design, assembly and performance of an autofocusing eyeglasses system to restore accommodation in presbyopes has been demonstrated.

SIGNIFICANCE

The new autofocusing eyeglasses system presented in this article has the potential to restore pre-presbyopic levels of accommodation in subjects diagnosed with presbyopia.

Evaluation of Eye Alignment before and after Cataract Surgery

Purpose: To assess changes in eye alignment before and after cataract surgery.Subjects and methods: The medical records of 786 cataract patients without eye movement limitation who underwent bilateral cataract surgery under topical anesthesia with monofocal IOL placement were retrospectively reviewed at the Eye Center of Sanno Hospital in Japan.Results: Before cataract surgery, 121 of the 786 patients (15.4%) had constant strabismus, 263 (33.5%) had intermittent strabismus, and 402 (51.1%) had phoria. Among the 121 patients with constant strabismus on the preoperative exam, 64 (52.9%) had exotropia without vertical strabismus, 7 (5.8%) had esotropia without vertical strabismus, and 6 (5.0%) had vertical strabismus without a horizontal component. After surgery, 98 of the 786 patients (12.5%) had constant strabismus, 126 (16.0%) had intermittent strabismus, 562 (71.5%) had phoria. The rate of eye alignment agreement before and after surgery was 72.3% overall. We found that 17 patients (2.2%) who did not have constant strabismus preoperatively developed constant strabismus postoperatively, and all of these patients experienced binocular diplopia. Characteristics of patients at risk for constant strabismus and diplopia postoperatively included patients with vertical deviation preoperatively (intermittent or phoria).Conclusions: Uncomplicated cataract surgery under topical anesthesia did not influence eye alignment classification in 72.3% of patients; however, patients with vertical deviation preoperatively were more likely to transition to constant strabismus after surgery.

Impact of monovision on dynamic accommodation of early presbyopes

PURPOSE

To examine the impact of monovision on dynamic changes in accommodation, pupil responses, spherical aberration and resultant image quality in early presbyopes.

METHODS

Refractive state, pupil size and spherical aberration levels were monitored in nine early presbyopes who exhibited some accommodation (40-50 years, mean = 42 ± 2.37 years) using a Shack-Hartmann aberrometer as a binocularly viewed stimulus stepped closer (from 2 m to 40 cm), or farther (from 40 cm to 2 m). Comparison data from two fully presbyopic (i.e. non-accommodating) subjects (ages 46 and 61 years) and two young adults (ages 26 and 29 years) were also collected. Each subject was fit with four different refractive strategies: (1) both eyes corrected for 2 m, (2) both eyes corrected for 40 cm, (3) monovision with the measured right eye corrected for 2 m and, (4) monovision with the right eye corrected for 40 cm. Monochromatic image quality was quantified using the AreaMTF metric.

RESULTS

When fit with monovision, the largest number of early presbyopes produce an accommodative response dominated by the right eye correction (distance or near) as the stimulus is abruptly changed from the retinal conjugate plane of one eye to that of the other eye. However, the accommodative responses in some early presbyopes were always dominated by the distance corrected eye, the near corrected eye, or by convergence. When the stimulus approached, the near corrected eye experienced high image quality only if there was no accommodative response. However, reduced image quality was observed if an accommodative response was initiated. Neither accommodation nor pupil response latencies were longer with monovision corrections compared with bilateral distance corrections (p > 0.05). In the early presbyopes, spherical aberration was reduced during near viewing, but primarily due to pupil miosis and not lens shape changes.

CONCLUSION

As the stimulus was abruptly changed from the retinal conjugate plane of the distance corrected eye to that of the near corrected eye, most early presbyopes fit with monovision accommodated, which resulted in a decline, not an increase in image quality in the near corrected eye. These results reveal a non-optimal accommodative strategy in early presbyopes fit with monovision.

Correction of presbyopia: old problems with old (and new) solutions

We live in a three-dimensional world and the human eye can focus images from a wide range of distances by adjusting the power of the eye's lens (accommodation). Progressive senescent changes in the lens ultimately lead to a complete loss of this ability by about age 50, which then requires alternative strategies to generate high-quality retinal images for far and close viewing distances. This review paper highlights the biomimetic properties and underlying optical mechanisms of induced anisometropia, small apertures, dynamic lenses, and multi-optic lenses in ameliorating the visual consequences of presbyopia. Specifically, the advantages and consequences of non-liner neural summation leveraged in monovision treatments are reviewed. Additionally, the value of a small pupil is quantified, and the impact of pinhole pupil location and their effects on neural sensitivity are examined. Different strategies of generating multifocal optics are also examined, and specifically the interaction between ocular and contact or intraocular lens aberrations and their effect on resulting image quality are simulated. Interestingly, most of the novel strategies for aiding presbyopic and pseudophakic eyes (for example, monovision, multifocality, pinhole pupils) have emerged naturally via evolution in a range of species.

The Importance of the Interaction Between Ocular Motor Function and Vision During Human Infancy

Numerous studies have demonstrated the impact of imposed abnormal visual experience on the postnatal development of the visual system. These studies have provided fundamental insights into the mechanisms underlying neuroplasticity and its role in clinical care. However, the ocular motor responses of postnatal human infants largely define their visual experience in dynamic three-dimensional environments. Thus, the immature visual system needs to control its own visual experience. This review explores the interaction between the developing motor and sensory/perceptual visual systems, together with its importance in both typical development and the development of forms of strabismus and amblyopia.

Accommodation in Early Presbyopes Fit with Bilateral or Unilateral Near Add

SIGNIFICANCE

When fit with monovision, most early presbyopes (aged 40 to 50 years) accommodated to near objects by focusing the distance corrected eye, leaving the near corrected eye myopically defocused with reduced image quality. A few were able to switch focus to the near corrected eye retaining a consistently focused image in one eye over a wider range of distances.

PURPOSE

The aim of this study was to examine accommodation behavior, pupil responses, and resultant image quality of early presbyopes fit with either bilateral or unilateral (monovision) near adds.

METHODS

Accommodative response and pupil size of 19 subjects (27 to 60 years), including 13 early presbyopes (40 to 50 years), were measured using an aberrometer as a binocularly viewed 20/40 letter E was moved from 2 m to 20 cm. Each subject was fit with different refractive strategies: bilateral distance correction, bilateral +2 diopters (D) near add, and unilateral +2 D near add placed over the measured right eye or unmeasured left eye. Monochromatic image quality was quantified using the Visual Strehl ratio metric.

RESULTS

With bilateral +2 D near add, all early presbyopes mostly refrained from accommodating (gain = 0.22 D/D) until the target approached closer than the 50-cm far point, and they then accommodated accurately until their maximum accommodative amplitude was reached. With monovision, most (10 of 13 early presbyopes) accommodated to focus the distance corrected eye, leaving the near corrected eye myopically defocused with reduced image quality. As stimulus distance became closer than their distance corrected eye's near point, they continued to exert maximum accommodation. Only two early presbyopes relaxed their accommodation to "switch" focus to the near corrected eye as target distance was reduced, and these two did not experience bilateral drop in image quality as stimulus distance became closer than the near point of the distance corrected eye.

CONCLUSIONS

Our data suggest that many early presbyopes will not initially adopt an accommodation strategy that optimizes image quality with monovision, but consistently accommodate to focus the distance corrected eye.

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.].

Nonsurgical management of diplopia

Diplopia is a potential undesirable outcome of nearly any ocular surgery. In some cases, the unexpected strabismus and diplopia resolve quickly without intervention, especially if due to swelling or minor insult from the surgical procedure. When double vision persists, effective treatment may be more elusive in patients in which the strabismus is the result of a restrictive process. The sudden onset of strabismus makes treatment more challenging. Frequently these patients will require surgical intervention. Where possible, patients may be managed with nonsurgical treatments until the time of surgery or indefinitely if successful and acceptable to the patient. Diplopia has been documented as a result of restrictive strabismus following vitreoretinal surgery, glaucoma surgery, orbital decompression surgery, strabismus surgery, orbital surgery, conjunctival surgery, cataract surgery, blepharoplasty, and others. The treatment of diplopia after ocular surgery is complicated by the incomitance and torsion that may be associated with restrictive strabismus as well as the variability of the deviation during healing. Nonsurgical treatment options include prisms or occlusion. Fresnel prisms are used primarily, but occasionally the prism is ground into the spectacles. Occlusion of the involved eye may be partial or complete, using a "pirate" patch, adhesive patch, Bangerter foil, tape, or related method.