Refractive changes in silicone filled eyes

Silicone oil insulation effects on flash electroretinogram and visual evoked potential in patients with retinal detachment

BACKGROUND

Silicone oil is used as endotamponade following vitreoretinal surgery to maintain the retina reattached when indicated. This study investigates the hypothesis that silicone oil causes insulation effects on the retina by affecting its response to light.

METHODS

Electrophysiological responses to a flash stimulus were recorded using full-field electroretinography (ERG) and visual evoked potentials (VEP). Recordings were performed in 9 patients who underwent surgery for retinal detachment, before (1-2 days) and after (2-3 weeks) silicone oil removal (SOR) in both the study and the control eye. Flash ERG and VEP recordings were performed according to the ISCEV standard protocol.

RESULTS

Statistically significant differences were found in the study eye in the amplitudes of the ERG responses and their corresponding ratios, i.e. the amplitude after SOR over the amplitude before SOR, in all conditions tested. No differences were observed in the control eye. The mean ratio of photopic ERG response was 3.4 ± 2.4 for the study and 1.0 ± 0.3 for the control eye (p<0.001). The mean ratio of ERG flicker response was 3.1 ± 2.4 and 1.0 ± 0.3, respectively (p = 0.003). Scotopic flash ERG ratio was 5.0 ± 4.4 for the study and 1.3 ± 0.6 for the control eye (p = 0.012). No differences were observed for the amplitude and latency of flash VEP response after SOR.

CONCLUSIONS

Silicone oil causes a reduction in flash ERG responses; no effect was found on flash VEP responses. ERGs in eyes filled with silicone oil should not be considered representative of retinal functionality, in contrast to VEPs, which are not affected by silicone oil presence.

In vivo evaluation of a Nano-enabled therapeutic vitreous substitute for the precise delivery of triamcinolone to the posterior segment of the eye

This study focused on the design of a thermoresponsive, nano-enabled vitreous substitute for the treatment of retinal diseases. Synthesis of a hydrogel composed of hyaluronic acid and a poloxamer blend was undertaken. Poly(D,L-lactide-co-glycolide) acid nanoparticles encapsulating triamcinolone acetonide (TA) were synthesised with a spherical morphology and mean diameter of ~ 153 nm. Hydrogel fabrication and nanoparticle loading within the hydrogel was confirmed via physicochemical analysis. Gelation studies indicated that hydrogels formed in nine minutes and 10 min for the unloaded and nanoparticle-loaded hydrogels, respectively. The hydrogels displayed in situ gel formation properties, and rheometric viscoelastic studies indicated the unloaded and loaded hydrogels to have modulus values similar to those of the natural vitreous at 37 °C. Administration of the hydrogels was possible via 26G needles allowing for clinical application and drug release of triamcinolone acetonide from the nanoparticle-loaded hydrogel, which provided sustained in vitro drug release over nine weeks. The hydrogels displayed minimal swelling, reaching equilibrium swelling within 12 h for the unloaded hydrogel, and eight hours for the nanoparticle-loaded hydrogel. Biodegradation in simulated vitreous humour with lysozyme showed < 20% degradation within nine weeks. Biocompatibility of both unloaded and loaded hydrogels was shown with mouse fibroblast and human retinal pigment epithelium cell lines. Lastly, a pilot in vivo study in a New Zealand White rabbit model displayed minimal toxicity with precise, localised drug release behaviour, and ocular TA levels maintained within the therapeutic window for the 28-day investigation period, which supports the potential applicability of the unloaded and nanoparticle-loaded hydrogels as vitreous substitutes that function as drug delivery systems following vitrectomy surgery.

Refractive outcomes following silicone oil tamponade in vitreoretinal surgery

PURPOSE

To evaluate the factors influencing the refractive outcomes following silicone oil tamponade (SOT) and silicone oil removal (SOR) in different lens statuses post-vitreoretinal surgery.

DESIGN

Retrospective analysis of three different lens statuses.

MATERIALS AND METHODS

This was a descriptive study that included 150 eyes of 147 patients who had undergone pars plana vitrectomy with SOT and SOR between January 2017 and June 2021. Demographic profile, spherical equivalent refraction (SER), and its association with clinical features were evaluated with SOT and post-SOR.

RESULTS

The mean (±standard deviation [SD]) age was 47 ± 17.8 years, including all three groups. SER was represented in diopters (D). The mean ± SD refraction with SOT in phakic, pseudophakic, and aphakic was 4.28 ± 2.59 D, 2.94 ± 2.58 D, and 3.98 ± 4.82 D. The mean SER post-SOR in phakic, pseudophakic, and aphakic was -2.72 ± 2.03 D, -1.12 ± 1.41 D, and 8.22 ± 3.70 D. The diagnosis of rhegmatogenous retinal detachment (RRD) among 96 eyes (64%) is the common indicator to perform vitreoretinal (VR) surgery. A minority of subjects were managed with retinal lasers before VR surgery (14%). The macula was attached in 100 eyes (67.6%), the belt buckle was done in 37 eyes (24.7%), and the silicone oil viscosity with 1000 centistoke was chosen in 129 eyes (86%).

CONCLUSION

SOT was used as a tamponade in VR surgeries irrespective of lens status. The significant predictor for post-SOR refraction in phakic and aphakic is post-SOT refraction. In pseudophakic, gender and diagnosis of RRD are the predictors of SOR refraction.

Use of Dichlorodimethylsilane to Produce Polydimethylsiloxane as a Substitute for Vitreous Humour: Characteristics and In Vitro Toxicity

Polydimethylsiloxane (PDMS) is a substitute for vitreous humour in vitreoretinal surgery and is usually produced from octamethylcyclotetrasiloxane (D4). In Indonesia, both commercial PDMS and D4 are limited and expensive. Dichlorodimethylsilane (DCMS) can be an alternative to produce PDMS. DCMS is cheaper and easier to obtain than D4. However, more extra effort is needed in order to produce PDMS from DCMS. Therefore, this study aimed to produce PDMS from DCMS by varying the ratio of DCMS precursor to dichloromethane (DCM) solvent at ratios of 1:1 and 1:4 through the hydrolysis-condensation method under neutral conditions. The PDMS produced had medium- (2.06 Pa·s) and high viscosity (3.59 Pa·s), with densities ranging from 0.96 to 0.99 g/mL. The refractive index was 1.4034-1.4036 and surface tension was 21 × 10-3 N/m, while they were able to transmit ~100% visible light, which were similar values to the commercial PDMS characteristics. PDMS samples were characterized using IR and NMR spectroscopy, which confirmed they were of PDMS type. The most optimum DCMS:DCM ratio was 1:1 due to the medium-viscosity PDMS type that could be produced. The in vitro HET-CAM toxicity test showed that samples were non-irritant, similar to PDMS produced from D4. PDMS from DCMS was non-toxic and ready to be used as a vitreous humuor substitution.

Vitreous Substitutes from Bench to the Operating Room in a Translational Approach: Review and Future Endeavors in Vitreoretinal Surgery

Vitreous substitutes are indispensable tools in vitreoretinal surgery. The two crucial functions of these substitutes are their ability to displace intravitreal fluid from the retinal surface and to allow the retina to adhere to the retinal pigment epithelium. Today, vitreoretinal surgeons can choose among a plethora of vitreous tamponades, and the tamponade of choice might be difficult to determine in the ever-expanding range of possibilities for a favorable outcome. The currently available vitreous substitutes have disadvantages that need to be addressed to improve the surgical outcome achievable today. Herein, the fundamental physical and chemical proprieties of all vitreous substitutes are reported, and their use and clinical applications are described alongside some surgical techniques of intra-operative manipulation. The major upcoming developments in vitreous substitutes are extensively discussed, keeping a translational perspective throughout. Conclusions on future perspectives are derived through an in-depth analysis of what is lacking today in terms of desired outcomes and biomaterials technology.

Intraocular accommodative movements in monkeys; relationship to presbyopia

Our goal was to quantify the age-related changes in the dynamic accommodative movements of the vitreous and aqueous humor in iridic, aniridic, phakic and aphakic primate eyes. Six bilaterally iridic and four bilaterally iridectomized rhesus monkeys, ranging in age from 6 to 25 years, received a stimulating electrode in the midbrain Edinger-Westphal nucleus to induce accommodation, measured by a Hartinger coincidence refractometer. One of the four iridectomized monkeys underwent unilateral extracapsular and another monkey underwent intracapsular lens extraction. Eyes were imaged utilizing specialized techniques and contrast agents to resolve intraocular structures. During accommodation the anterior hyaloid membrane and the posterior lens capsule bowed backward. Central vitreous fluid and structures/strands moved posteriorly toward the optic nerve region as peripheral vitreous, attached to the vitreous zonule, was pulled forward by ciliary muscle contraction. Triamcinolone particles injected intravitreally were also observed in the anterior chamber and moved from the anterior chamber toward the cleft of the anterior hyaloid membrane and then further posteriorly into the vitreous-filled cleft between the vitreous zonule and the ciliary body pars plana. These accommodative movements occurred in all eyes, and declined with age. There are statistically significant accommodative movements of various intravitreal structures. The posterior/anterior fluid flow between the anterior chamber and the vitreous compartments during accommodation/disaccommodation represents fluid displacement to allow/facilitate lens thickening. The posterior accommodative movement of central vitreous fluid may result from centripetal compression of the anterior tips of the cistern-like structure attached to the vitreous zonule, and posterior displacement of the central trunk of the cistern during ciliary muscle contraction and centripetal muscle movement. The findings may have implications for presbyopia.

Changes of retinal ganglion cell complex after vitrectomy in rhegmatogenous retinal detachment patients and its correlation with inflammatory blood biomarkers

Purpose

To compare retinal ganglion cell complex (GCC) parameters between rhegmatogenous retinal detachment (RRD) eyes and normal contralateral eyes after vitrectomy and to evaluate their correlation with inflammatory blood markers.

Methods

We investigated 25 eyes that underwent vitrectomy due to RRD. Venous blood samples were collected from all participants before 08:00 a.m. on the second day of admission after a 12-hour fast for blood counts. The differences of retinal structure between RRD and contralateral eyes were compared 1 week postoperatively.

Results

Focal loss volume (FLV) (2.009 ± 1.286)% was significantly increased compared with the contralateral eyes (p <  0.001). Monocyte-to-high-density lipoprotein was significantly positively correlated with GCC thickness parameters, and negatively correlated with FLV and global loss volume (GLV). Postoperative best-corrected visual acuity was negatively correlated with GLV (p = 0.039, R² = 0.172).

Conclusion

Retinal ganglion cells (RGCs) loss might present early postoperatively in RRD eyes, and was associated with systemic inflammation. RGCs loss might affect postoperative vision.

Complications in Retinal Surgery: A Review of Corneal Changes Following Vitreoretinal Procedures

Purpose:

The purpose of this article is to discuss the early- and late-onset corneal complications that can occur following vitreoretinal surgery.

Methods:

A systematic review of the literature was conducted using PubMed and Google Scholar databases. Articles detailing the clinical findings and the associations between surgical techniques, irrigating solutions, and microsurgical instruments used for vitreoretinal surgery and postoperative corneal complications were included in this review.

Results:

Vitreoretinal surgery can be associated with corneal complications such as persistent corneal epithelial defects, neurotrophic keratopathy, band keratopathy, ocular surface disruption, and endothelial cell damage. Risk factors for the development of cornea complications after posterior segment surgery include history of uncontrolled diabetes mellitus, aphakia or pseudophakia, disrupted anterior lens capsule integrity, use of irrigating solutions without appropriate buffers, use of contact viewing lenses intraoperatively, intraocular gases or silicone oil after vitrectomy, and prolonged duration of surgery.

Conclusions:

Corneal complications secondary to vitreoretinal surgery are multifactorial, but more commonly arise in diabetic patients, those with preexisting ocular comorbidities, and under certain surgical-related conditions. Special pre-, peri-, and postoperative considerations, with a focus on early identification and management of risk factors, are required to help decrease the incidence of corneal complications.

Silicone oil versus gas tamponade for primary rhegmatogenous retinal detachment treated successfully with a propensity score analysis: Japan Retinal Detachment Registry

Background/aims

To compare the effects of silicone oil tamponade (SOT) to that of gas tamponade (GT) on the best-corrected visual acuity (BCVA) after successful vitrectomy for retinal detachment (RD).

Methods

A retrospective, multicentre, nationwide study with RD who were registered in the Japan-RD Registry. All cases with RD treated with successful vitrectomy between February 2016 and March 2017 were studied. A propensity score matching was performed using the preoperative findings as covariates to adjust the relevant confounders. The primary outcome was the estimated mean difference of the postoperative BCVA in 6 months between eyes treated with SOT to those treated with GT.

Results

Of the 3446 cases registered, 2097 cases met the entry criteria. There were 2042 eyes that had GT and 55 eyes that had SOT. Primary success was defined as a reattached retina with no tamponade at 6 months. After propensity score matching, each group contained 40 cases. The preoperative BCVA was 0.966±0.738 logMAR units in the GT group and 1.270±0.945 logMAR units in the SOT group (p=0.177). Six months postoperatively, the BCVA in the GT group was significantly better at 0.309 logMAR units in the GT group than the 0.671 logMAR units in the SOT group (p=0.002).

Conclusions

Even after successful surgery for RD, eyes that experienced SOT had poorer BCVA than eyes treated with GOT. SOT should be considered cautiously.

Precis

Propensity score analysis of eyes with rhegmatogenous RD showed that postoperative vision was worse in eyes treated once with silicone oil than with gas even after completely successful surgery.

Changes in ocular biometric measurements after vitrectomy with silicone oil tamponade for rhegmatogenous retinal detachment repair

Background

To observe the changes in ocular biometric measurements after vitrectomy with silicone oil tamponade for rhegmatogenous retinal detachment (RRD) repair.

Methods

Sixty-three phakic, macula-off RRD eyes underwent vitrectomy with silicone oil tamponade but not lens extraction were included in this retrospective study. Measurements of axial length (AL), anterior chamber depth (ACD), lens thickness (LT) using the new Zeiss IOLMaster 700 and derivative lens position (LP), relative lens position (RLP) and lens-retina distance (LRD) were compared and analyzed between preoperative and postoperative in phakic, macula-off eyes with RRD.

Results

Preoperative AL, ACD, LT, LP, RLP and LRD were 24.94 ± 1.82 mm, 3.45 ± 0.42 mm, 4.34 ± 0.16 mm, 5.55 ± 0.41 mm, 0.22 ± 0.01 and 19.52 ± 1.82 mm. After a mean 4.85-month duration of silicone oil tamponade, postoperative AL, ACD, LT, LP, RLP and LRD were 25.42 ± 2.20 mm, 3.30 ± 0.41 mm, 4.43 ± 0.21 mm, 5.46 ± 0.40 mm, 0.22 ± 0.02 and 20.17 ± 2.36 mm, respectively. The differences in all measurements are significant (all P < 0.05). Preoperative AL and LRD are positively while RLP is negatively correlated with change in LRD. Change in AL but not in LT or LP is correlated with change in LRD. Biometric measurements except LT between preoperative and postoperative were in close agreement.

Conclusion

The underestimation of AL and anterior shifting of lens in phakic, macula-off eyes with RRD after vitrectomy with silicone oil tamponade.

Ability of Nonswelling Polyethylene Glycol-Based Vitreous Hydrogel to Maintain Transparency in the Presence of Vitreous Hemorrhage

Purpose

Postoperative vitreous hemorrhage is a vision-impacting complication of vitrectomy. This preclinical in vitro study assessed the potential ability of a nonswelling polyethylene glycol-based artificial vitreous hydrogel to maintain transparency in the vitreous cavity in the presence of vitreous hemorrhage.

Methods

Samples (1 mL) of diluted blood at concentrations of 0.1%, 0.25%, 0.5%, and 1.25% were added to 1 mL samples of polymerized hydrogel in cuvettes (gel + blood group); 2 mL samples of diluted blood at the same concentrations were prepared as controls (blood only group). Spectral transmission curves for the hydrogel (gel + blood group) and diluted blood (blood only group) were obtained before and on days 1, 2, 5, 7, 14, and 28 of the experiment. Between-group comparisons were made using the Student's t-test. The percentage of transmittance in the visible light spectrum (400–700 nm) was measured at each time point.

Results

Mean light transmittance was maintained at >90% until day 7 in the gel + blood group and was significantly greater in the gel + blood than in the blood only groups in samples containing blood diluted to 0.25%, 0.5%, and 1.25% during the 28-day study period (P < 0.05).

Conclusions

A nonswelling polyethylene glycol-based artificial vitreous hydrogel maintained high optical transparency in the presence of blood through the study period. Injection of this hydrogel into the vitreous cavity at the end of surgery might help to prevent or mitigate vitreous hemorrhage-associated postoperative visual loss.

Translational Relevance

The hydrogel may prevent visual loss due to postoperative vitreous hemorrhage.

Behavioural responses to a photovoltaic subretinal prosthesis implanted in non-human primates

Retinal dystrophies and age-related macular degeneration related to photoreceptor degeneration can cause blindness. In blind patients, although the electrical activation of the residual retinal circuit can provide useful artificial visual perception, the resolutions of current retinal prostheses have been limited either by large electrodes or small numbers of pixels. Here we report the evaluation, in three awake non-human primates, of a previously reported near-infrared-light-sensitive photovoltaic subretinal prosthesis. We show that multipixel stimulation of the prosthesis within radiation safety limits enabled eye tracking in the animals, that they responded to stimulations directed at the implant with repeated saccades and that the implant-induced responses were present two years after device implantation. Our findings pave the way for the clinical evaluation of the prosthesis in patients affected by dry atrophic age-related macular degeneration.

SILICONE OIL TAMPONADE EFFECT ON MACULAR LAYER THICKNESS AND VISUAL ACUITY

PURPOSE

To evaluate the influence of silicone oil (SO) tamponade on retinal layers thickness and visual acuity in patients who underwent pars plana vitrectomy for rhegmatogenous retinal detachment.

METHODS

This is a retrospective case series of consecutive patients who underwent pars plana vitrectomy for rhegmatogenous retinal detachment with SO tamponade. Visual acuity and central macular thickness were measured with SO and at least a month after SO removal (SOR). Patients with insufficient or poor-quality images or macular pathologies such as macular edema or epiretinal membranes were excluded.

RESULTS

Forty-one patients with an average age of 56.1 ± 15.2 years were included, and 54% presented with fovea ON. Average tamponade duration was 151 ± 54 days. Central macular thickness of the operated eye increased from 249 ± 50 µm before to 279 ± 48 µm after SOR (P < 0.001), compared with 281 ± 21 µm of the fellow eye (P < 0.001). A mean change of 26 µm was found in the internal layers (P < 0.001). Visual acuity improved from 0.85 ± 0.97 logarithm of the minimal angle of resolution (logMAR; Snellen 20/140) with SO tamponade to 0.34 ± 0.28 logMAR (Snellen 20/43) after SOR (P < 0.001). For patients with fovea ON and without significant cataract, visual acuity was 0.19 ± 0.16 logMAR (Snellen 20/30) at presentation, 0.59 ± 0.41 logMAR (Snellen 20/80) with SO (P = 0.005), and 0.18 ± 0.15 logMAR (Snellen 20/30) after SOR (P = 0.003).

CONCLUSION

Silicone oil tamponade causes a transient decrease in central macular thickness, mainly in the inner layers. After SOR, central macular thickness resembles to the fellow eyes. The mechanism for this effect is unclear, but apparently has no influence on final visual acuity.

HIGHER-ORDER ABERRATIONS IN EYES WITH SILICONE OIL TAMPONADE

PURPOSE

To investigate the changes in higher-order aberrations (HOAs) after silicone oil removal and to evaluate their associations with visual acuity.

METHODS

Fifty-nine eyes of 58 patients who underwent SO removal were included. Total, corneal, and internal optic HOAs, and best-corrected visual acuity were measured before and 1 month after SO removal, and changes were compared between phakic and pseudophakic eyes.

RESULTS

Total ocular and internal optic HOAs decreased significantly after SO removal both in pseudophakic (n = 40, all P < 0.001) and phakic eyes (n = 19, P = 0.017, P = 0.004). Preoperative HOAs (P < 0.001) and changes in HOAs (P = 0.006) were greater in pseudophakic eyes than in phakic eyes. Best-corrected visual acuity was significantly improved after SO removal, from 20/105 to 20/78 (P < 0.001) in pseudophakic eyes, whereas there was no difference in phakic eyes (P = 0.714). Preoperative HOAs and the reduction in HOAs after SO removal were greater in best-corrected visual acuity-improved eyes than best-corrected visual acuity-unchanged eyes (P < 0.001).

CONCLUSION

Silicone oil tamponade induced an increase in HOAs, and these increases were greater in pseudophakic eyes than in phakic eyes. Silicone oil may cause additional visual impairments because of HOAs, beyond those caused by retinal diseases, particularly in pseudophakic eyes.

ARTEFACTUALLY DAMPENED FLASH STIMULUS VISUAL EVOKED RESPONSES IN A SILICONE OIL-FILLED EYE

PURPOSE

To report a case of falsely dampened visual evoked responses in a patient of Usher syndrome after retinal detachment surgery secondary to probable intraocular silicone oil.

METHODS

Retrospective observational case report.

CASE DESCRIPTION

A 16-year-old boy with Usher syndrome developed rhegmatogenous retinal detachment in the left eye. He underwent a successful retinal detachment surgery with silicone oil tamponade. On his postoperative follow-up visit, poor vision was noted by our optometrist. A flash stimulus visual evoked response was done, which showed marked delayed latency and reduced amplitude. Marked improvement in the flash stimulus visual evoked response potentials and waveforms was noted after silicone oil removal.

CONCLUSION

Intraocular silicone oil could be responsible for this false delay in the latency and reduction in flash stimulus visual evoked response amplitudes. Assessment of flash stimulus visual evoked responses in the presence of silicone oil after vitreoretinal surgery may produce unreliable responses.

Refractive outcomes of combined phacovitrectomy and delayed cataract surgery in retinal detachment

OBJECTIVE

To compare the accuracy of refractive outcomes between combined pars plana vitrectomy (PPV) and cataract surgery and delayed cataract surgery after PPV in cases with rhegmatogenous retinal detachment (RD).

DESIGN

Retrospective case series.

PARTICIPANTS

Thirty-eight eyes underwent combined phacovitrectomy (combined group) and 25 eyes underwent delayed cataract surgery after PPV (delayed group).

METHODS

RD height was measured using optical coherence tomography. Refractive outcomes were evaluated using mean absolute error (MAE; the difference between final refractive error and target refractive error).

RESULTS

Combined group showed significant myopic shift (mean error; -0.40 ± 1.07 vs 0.07 ± 0.56 D, p = 0.028) and large MAE (0.81 ± 0.81 vs 0.48 ± 0.29 D, p = 0.028) compared with delayed group. Multiple logistic regression analysis revealed that only RD height was significantly associated with MAE greater than 2 D after combined surgery (in 100-µm unit, odds ratio 3.23, 95% CI 1.04-10.02, p = 0.042). RD height was also significantly correlated with the difference in axial length (AL) between 2 eyes of the patients (p = 0.006, r = 0.406) and the difference in AL measured at pre- versus post-RD repair in the delayed group (p < 0.001, r = 0.774).

CONCLUSIONS

Combined phacovitrectomy in patients with rhegmatogenous RD induced significant myopic shift because of underestimation of AL, especially in patients with high RD height. Thus, in cases with high temporal RD or large AL differences between eyes, either delayed cataract surgery or combined cataract surgery using the contralateral AL is recommended.

Novel approach for phacoemulsification during combined phacovitrectomy

Purpose

To evaluate the safety and efficacy of surgeon’s superior sitting position during temporal clear corneal incision (TCCI) phacoemulsification, with a 90° working angle, during combined phacovitrectomy.

Methods

Prospective interventional case series were performed on 65 eyes of 63 patients. TCCI phacoemulsification was done in all cases (whether right or left eyes), while the surgeon was sitting superiorly to the operating table.

Outcome measures included

Shift in sitting position, keratometric astigmatism, surgically induced astigmatism, posterior capsule integrity, and intraocular lens centration.

Results

Phacoemulsification was performed completely in all cases (100%). Shift in position to temporal sitting position happened in two cases (3%). The keratometric astigmatism showed mean changes of 1.09 D (0.25–3.75 D) to 0.84 D (0.00–3.25 D) at 1 month, which remained stable at 6 months; 0.84 D (0.16–3.21 D). The surgically induced astigmatism was 0.25 DC (−0.50 to 1.0 DC) at 1 month, which stayed stable at 6 months; 0.25 D (−0.63 D to 0.98 D). Posterior capsular rupture occurred in one case (the second case) (1.5%). The intraocular lens was centered in all cases (100%).

Conclusion

Superior sitting TCCI phacoemulsification, with a wide working angle, during combined phacovitrectomy proved safe and easy, without the burden of changing and disrupting the operative setting. The anatomical and optical outcomes were acceptable.

Accommodative movements of the vitreous membrane, choroid, and sclera in young and presbyopic human and nonhuman primate eyes

PURPOSE

We report, for the first time to our knowledge, dynamic movements of the vitreous membrane and peripheral choroid during accommodation, and age-related changes in the anterior sclera.

METHODS

We studied 11 rhesus monkeys (ages 6-27 years) and 12 human subjects (ages 19-65 years). Accommodation was induced pharmacologically in human subjects and by central electrical stimulation in the monkeys. Ultrasound biomicroscopy, endoscopy, and contrast agents were used to image various intraocular structures.

RESULTS

In the monkey, the anterior hyaloid membrane bows backward during accommodation in proportion to accommodative amplitude and lens thickening. A cleft exists between the pars plicata region and the anterior hyaloid membrane, and the cleft width increases during accommodation from 0.79 ± 0.01 mm to 1.01 ± 0.02 mm in young eyes (n = 2, P < 0.005), as fluid from the anterior chamber flows around the lens equator toward the cleft. In the older eyes the cleft width was 0.30 ± 0.19 mm, which during accommodation increased to 0.45 ± 0.20 mm (n = 2). During accommodation the ciliary muscle moved forward by approximately 1.0 mm, pulling forward the choroid, retina, vitreous zonule, and the neighboring vitreous interconnected with the vitreous zonule. Among the humans, in the older eyes the scleral contour bowed inward in the region of the limbus, compared to the young eyes.

CONCLUSIONS

The monkey anterior hyaloid bends posteriorly during accommodation in proportion to accommodative amplitude and the sclera bows inward with increasing age in both species. Future descriptions of the accommodative mechanism, and approaches to presbyopia therapy, may need to incorporate these findings.

Refractive state following retinal reattachment and silicone oil tamponade in dogs

OBJECTIVE

To evaluate the refractive error induced by intraocular administration of silicone oil (SiO) in dogs.

ANIMALS

47 client-owned dogs evaluated for blindness secondary to retinal detachment.

PROCEDURES

-3-port pars plana vitrectomy with perfluoro-octane and SiO exchange (1,000- or 5,000-centistoke SiO) was performed in 1 or both eyes for all dogs (n = 63 eyes), depending on which eye or eyes were affected. Dogs were normotensive, had complete oil filling of the eyes, and were examined in a standing position for retinoscopic examination of both eyes (including healthy eyes).

RESULTS

The mean refractive error for SiO-filled phakic and pseudophakic eyes was 2.67 and 3.24 D, respectively. The mean refractive error for SiO-filled aphakic eyes was 6.50 D. Dogs in which 5,000-centistoke SiO was used had consistently greater positive refractive errors (mean, 3.45 D), compared with dogs in which 1,000-centistoke SiO was used (mean, 2.10 D); however, the difference was nonsignificant. There was no significant linear relationship between refractive error and the number of days between surgery and retinoscopy.

CONCLUSIONS AND CLINICAL RELEVANCE

Hyperopia was observed in all dogs that underwent SiO tamponade, regardless of lens status (phakic, pseudophakic, or aphakic). Aphakic eyes underwent a myopic shift when filled with SiO. Pseudophakic eyes appeared to be more hyperopic than phakic eyes when filled with SiO; however, additional investigation is needed to confirm the study findings.

Refractive status and visual acuity changes after oil removal in eyes following phacovitrectomy, intraocular lens implantation, and silicone oil tamponade

OBJECTIVE

To examine the refractive changes in pseudophakic eyes with silicone oil tamponade (SOT) and removal.

DESIGN

Retrospective review.

PARTICIPANTS

Twenty-six consecutive eyes (23 patients) that had undergone phacovitrectomy, posterior chamber intraocular lens (IOL) implantation, and SOT by a single surgeon.

METHODS

Phacoemulsification and biconvex-type foldable acrylic IOLs were implanted. A standard 3-port pars plana vitrectomy was performed using a 20-gauge vitrectomy system. Following fluid-air exchange, 1300 centistokes silicone oil (SO) was injected. Manifest refractions with SOT and after SO removal were performed using best-spectacle correction based on retinoscopy results at least 1 month after each surgery.

RESULTS

A mean spherical equivalent of 3.85 (SD 1.63) diopters (D) and logMAR best-corrected visual acuity (BCVA) of 0.77 (SD 0.50) were observed with SOT. After SO removal, a myopic shift of -4.51 (SD 1.79) D was observed, resulting in -0.66 (SD 1.40) D, which concurred with the preoperative target of -0.47 (SD 0.50) D (p = 0.465, paired t test) and logMAR BCVA of 0.65 (SD 0.52) (p = 0.131, paired t test). Multivariate linear regression analysis demonstrated that the axial length and refractive index of the IOL were significant factors in determining refraction in oil-filled pseudophakia (p = 0.000).

CONCLUSIONS

Phacovitrectomy, IOL implantation, and SOT resulted in a tolerable range of hyperopia and visual acuity comparable to that after SO removal.

Refractive change caused silicone oil adhesion to the intraocular lens following Nd:YAG posterior capsulotomy

A 32-year-old female who had undergone the silicone oil removal procedure presented with visual disturbance in her left eye. Several months previous, she had cataract surgery in a private clinic, and a month later she had a Nd:YAG laser procedure for posterior capsulotomy. The slit-lamp examination revealed silicone oil droplets that had adhered to the intraocular lens where the posterior capsulotomy was performed. She had experienced high myopia as a manifestation of the resulting refractive changes. We replaced the previous intraocular lens with a new acrylic intraocular lens with resulting improvement to her vision. Here we report the case of a female patient with a history of silicone oil removal surgery where the resulting silicone bubbles had not been removed thoroughly and remained in the vitreous cavity. These bubbles subsequently adhered to the intraocular lens following YAG laser posterior capsulotomy, resulting in refractive changes. We recommend that implanting a silicone intraocular lens in anyone with a history of the silicone oil removal procedure or who has a possible history of silicone oil use should be avoided.

Biometry and refractive outcome of eyes filled with silicone oil by standardized echography and partial coherence interferometry

BACKGROUND

We evaluated the validity of calculations for refractive outcome in cataract surgery in silicone oil-filled eyes. The retrosilicone space (RSS) was included in these calculations.

METHODS

In a prospective study the axial length (AL) of silicone oil-filled eyes was measured. with standardized A-scan echography (SAE) and partial coherence interferometry (PCI). Meldrum's formula was used to transform the velocity of ultrasound within the vitreous cavity. To investigate whether refractive outcome can be calculated accurately, we assessed the difference between precalculated and final refractive outcome. Furthermore, we determined the advantages and disadvantages of SAE and PCI. A minor aim was to assess whether the AL of the two eyes differed significantly.

RESULTS

In 85% of 117 eyes the difference between precalculated and postsurgical refraction was smaller than 1 diopter spherical and statistically not significant (p>0.2). The mean AL was 24.1 mm (range 20.0-31.4 mm). The difference in outcome between the two methods was without statistical significance: the AL difference was 0.4 (+/-2.6) mm on measurement with SAE and 0.04 (+/-0.46) mm with PCI. PCI has the advantage that it can be performed more easily, without contact, while echography is advantageous in the presence of advanced cataracts. In supine position an oil-free fluid space behind the silicone oil was detected with echography. The mean dimension of this space was 1.9 (+/-0.67) mm and it was taken into consideration for IOL calculation. The mean AL difference between the two eyes was 0.4 mm, but the difference was greater than 1 mm in 26% of the patients.

CONCLUSION

The AL of eyes filled with silicone oil can be measured reliably with SAE and PCI. In supine position the RSS has to be considered to obtain more accurate IOL calculations.

Refractive changes in silicone oil-filled pseudophakic eyes

PURPOSE

We examined the refractive changes in pseudophakic eyes of patients with idiopathic macular hole treated with silicone oil injection.

METHODS

Twenty consecutive eyes of 19 patients with idiopathic macular hole who had undergone successful pars plana vitrectomy using silicone oil tamponade were studied retrospectively. Lensectomy with intraocular lens (IOL) implantation was performed on each patient before vitreous surgery. Five biconvex type IOL models were used. After pars plana vitrectomy and fluid-air exchange, silicone oil was injected to replace the air completely. Macular hole closure was confirmed by optical coherence tomography, and silicone oil removal was performed. Manifest refractions before silicone oil filling, with silicone oil filling, and after silicone oil removal were determined.

RESULTS

A mean hyperopic shift +/- SD in spherical equivalents of +5.69 +/- 1.71 diopters (P < 0.0001) was observed with silicone oil instillation. In contrast, a mean myopic shift +/- SD of -5.63 +/- 1.33 diopters was observed after silicone oil removal (P < 0.0001). The absolute value of the refractive shift showed a strong correlation with the posterior radius of the IOL (r = 0.699, P < 0.0001).

CONCLUSION

IOL models with steeper posterior convex curvature result in larger refractive deviations in patients scheduled for silicone oil instillation.

Clear lens extraction with intraocular lens implantation during retinal detachment repair in patients with Acquired Immune Deficiency Syndrome (AIDS) [correction of autoimmune deficiency syndrome] and cytomegalovirus retinitis

OBJECTIVE

To assess the outcomes of clear lens extraction with intraocular lens (IOL) implantation during repair of retinal detachment by vitrectomy with silicone oil tamponade in patients with acquired immunodeficiency syndrome (AIDS) and cytomegalovirus (CMV) retinitis.

DESIGN

Retrospective, noncomparative case series.

PARTICIPANTS

Twelve eyes of 10 patients with AIDS, CMV retinitis, and retinal detachment.

INTERVENTION

All patients underwent phacoemulsification with posterior chamber IOL placement at the time of vitrectomy with silicone oil tamponade for repair of retinal detachment. A targeted postoperative refractive error of -5.00 diopters (D) to -3.00 D was chosen in an attempt to counteract the hyperopic effect of silicone oil.

MAIN OUTCOME MEASURES

The following factors were evaluated: postoperative visual acuity, refractive error, and intraoperative and postoperative complications.

RESULTS

Median follow-up was 7 months (range, 1-46 months). For patients without macular necrosis, median best-corrected preoperative visual acuity was 20/75 (range, 20/20-20/800), and median best postoperative visual acuity was 20/50 (range, 20/20-20/400). Median final visual acuity was 20/140 (range, 20/25 to count fingers at 1 foot). The median postoperative refractive error (spherical equivalent) was -1.00 D (range, -4.00 D to +7.88 D). Reoperation was required in 3 of 12 eyes for recurrent macular detachment (1 with silicone oil underfill; 2 with proliferative vitreoretinopathy). The macula was attached in all eyes at last follow-up. Reattachment of the peripheral retina was achieved in 10 of 12 eyes. There were no anterior segment complications.

CONCLUSIONS

Clear lens extraction with IOL placement during repair of retinal detachment with silicone oil tamponade does not seem to increase complications and may improve long-term visual rehabilitation, improve retinitis management by allowing better posterior segment visualization throughout the postoperative course, and decrease overall cost and morbidity associated with cataract extraction as a second procedure.

Perfluorocarbons and semifluorinated alkanes

The introduction of perfluorocarbons (PFCs) and, more recently, semifluorinated alkanes (SFAs) has greatly facilitated vitreoretinal surgery. A distinction is made between the use of these substances as intraoperative tools and internal tamponade agents. This article reviews the physical and chemical properties of PFCs and SFAs and discusses the indications, results, and complications. The effectiveness of these substances as internal tamponade agents is discussed with reference to the specific gravity, contact angle, viscosity and ability to fill model eye chambers and the vitreous cavity. The evidence for the toxicity in animal and human is examined.

Predicted and actual refraction after intraocular lens implantation in eyes with silicone oil

OBJECTIVE

To determine the difference between the predicted and postoperative refraction in eyes with silicone oil that had extracapsular cataract extraction (ECCE), and intraocular lens (IOL) implantation.

SETTING

Ophthalmology department providing primary, secondary, and tertiary care in central Israel.

METHODS

Eight patients with silicone-oil-filled eyes following vitreoretinal procedures had ECCE and IOL implantation. The IOL power calculation was performed with the modified SRK II, the SRK/T, and the Holladay emmetropia/ametropia formulas, using the axial length of the eye, measured prior to the silicone oil injection, and the keratometric readings. The predicted and postoperative refractions were compared.

RESULTS

The postoperative refraction was more hyperopic than predicted by an average of 4.08 diopters (D) for the SRK II formula, 3.91 D for the SRK/T formula, and 4.01 D for the Holladay emmetropia/ametropia formula. Removing the silicone oil from two eyes several months after cataract extraction reduced the deviation from the predicted refraction to 0.25 and 0.80 D.

CONCLUSION

The presence of silicone oil in the vitreous space induces a hyperopic shift in eyes having ECCE and IOL implantation. This hyperopic shift should be considered when calculating the IOL power if a long-term tamponade with the oil is planned. If the silicone oil is to be removed shortly after the cataract extraction, the IOL power should be calculated solely from the formula.