Takashi Fujikado

Wavefront Analysis in Eyes With Nuclear or Cortical Cataract

PURPOSEnTo compare the higher-order aberrations of the oculus (whole eye) and cornea in eyes with mild cortical or nuclear cataract and to estimate the effect of ocular higher-order aberrations on the loss of contrast sensitivity using wavefront analysis.nnnDESIGNnObservational case series.nnnMETHODSnSix eyes of four patients with mild nuclear cataract, 18 eyes of 14 patients with mild cortical cataract, and nine eyes of nine normal patients were examined. Wavefront aberrations of the oculus and cornea for central 6 mm diameter were measured using the Hartmann-Shack (HS) aberrometer. Higher-order aberrations were calculated with Zernike polynomials up to sixth order. The relationship between average lens density (ALD) measured by the Scheimpflug camera and the ocular total higher-order aberration (OTHA) was investigated. The relationship between contrast sensitivity (CS) and the OTHA or ALD was also examined.nnnRESULTSnThe OTHA was significantly larger in cataracts compared with normal subjects, while corneal total higher-order aberration did not differ between cataracts and normal subjects. The polarity of spherical aberration was negative in all eyes with nuclear cataract while positive in all eyes with cortical cataract. The correlation between ALD and OTHA was not significant in eyes with cataracts. The CS highly correlated with OTHA while it moderately correlated with ALD.nnnCONCLUSIONSnThe HS aberrometer is useful to objectively evaluate the deterioration of images in eyes with mild cataract and it revealed that the polarity of spherical aberration was different between nuclear and cortical cataract. It was also suggested that in mild nuclear or cortical cataract, not only light scattering, but also optical aberration of the lens contributes to the loss of contrast sensitivity.

Evaluation of phosphenes elicited by extraocular stimulation in normals and by suprachoroidal-transretinal stimulation in patients with retinitis pigmentosa.

BackgroundTo determine the efficient parameters to evoke electrical phosphenes is essential for the development of a retinal prosthesis. We studied the efficient parameters in normal subjects and investigated if suprachoroidal-transretinal stimulation (STS) is effective in patients with advanced retinitis pigmentosa (RP) using these efficient parameters.MethodsThe amplitude of pupillary reflex (PR) evoked by transcorneal electrical stimulation (TcES) was determined at different frequencies in eight normal subjects. The relationship between localized phosphenes elicited by transscleral electrical stimulation (TsES) and the pulse parameters was also examined in six normal subjects. The phosphenes evoked by STS were examined in two patients with RP with bare light perception. Biphasic pulses (cathodic first, duration: 0.5 or 1.0xa0ms, frequency: 20xa0Hz) were applied through selected channel(s). The size and shape of the phosphenes perceived by the patients were recorded.ResultsThe maximum PR was evoked by TcES with a frequency of 20xa0Hz. The brightest phosphene was elicited by TsES with a pulse train of more than 10 pulses, duration of 0.5–1.0xa0ms and a frequency of 20 to 50xa0Hz. In RP patients, localized phosphenes were elicited with a current of 0.3–0.5xa0mA (0.5xa0ms) in patient 1 and 0.4xa0mA (1.0xa0ms) in patient 2. Two isolated or dumbbell-shaped phosphenes were perceived when the stimulus was delivered through two adjacent channels.ConclusionBiphasic pulse trains (≥10 pulses) with a duration of 0.5–1.0xa0ms and a frequency of 20–50xa0Hz were efficient for evoking phosphenes by localized extraocular stimulation in normal subjects. With these parameters, STS is a feasible method to use with a retinal prosthesis even in advanced stages of RPs.

Wavefront analysis of higher-order aberrations in patients with cataract ☆

Purpose: To determine local refractive changes and higher‐order aberrations in patients with nuclear or cortical cataract. Setting: Osaka University Medical School, Osaka, Japan. Methods: Wavefront analysis of both ocular and corneal aberrations was performed with the Hartmann‐Shack aberrometer in 2 patients, a 22‐year‐old woman with bilateral developmental nuclear cataract and a 68‐year‐old woman with mild bilateral cortical cataract. Results: Case 1 showed a delay in the wavefront that caused a myopic shift in the central pupillary area in both eyes, associated with the nuclear cataract. The spherical‐like aberration (right eye, 36%; left eye, 21%) was greater than the coma‐like aberration in both eyes. Case 2 showed an advancement of the wavefront that caused a hyperopic shift, especially in the lower temporal pupillary area, that was associated with the cortical cataract. The coma‐like aberration (right eye, 63%; left eye, 52%) was greater than the spherical‐like aberration in both eyes. The polarity of the third‐order spherical aberration was negative in Case 1 and positive in Case 2. Corneal higher‐order aberrations were small and had a different distribution than ocular higher‐order aberrations in both patients. Conclusions: The Hartmann‐Shack aberrometer was useful in detecting local refractive changes and higher‐order aberrations in patients with mild cataract. The polarity and the absolute value of ocular higher‐order aberrations may be useful parameters to characterize eyes with cataract.

Optical coherence tomographic findings of Macular holes and retinal detachment after vitrectomy in highly myopic eyes

PURPOSEnMacular holes cause retinal detachments in highly myopic eyes. Because degenerative macular changes often coexist, biomicroscopic evaluation of macular hole status after retinal reattachment is sometimes difficult. We studied macular holes with retinal detachment after vitrectomy using optical coherence tomography and evaluated the anatomic status of the hole and factors associated with anatomic success.nnnDESIGNnRetrospective, nonrandomized, comparative study.nnnPATIENTSnSixteen eyes that underwent vitrectomy for retinal detachment associated with a macular hole were included. Internal limiting membrane peeling with indocyanine green was performed in 14 eyes; the epiretinal membrane was peeled with a diamond-dusted membrane scraper alone in two eyes. All retinas reattached postoperatively. The follow-up period at the optical coherence tomography examination was at least 6 months.nnnMETHODSnOptical coherence tomography was performed vertically and horizontally, and the presence of a persistent macular hole was determined. Other information was obtained from patient records.nnnRESULTSnThe macular holes closed in seven of 16 eyes (44%). Age, sex, axial length, preoperative best-corrected visual acuity, duration of symptoms, preoperative refractive error, and the preoperative area of the retinal detachment were not significantly correlated with hole closure. Improved postoperative best-corrected visual acuity (P <.05) was significantly associated with macular hole closure, and more frequent visual improvement (P =.06) was of borderline significance.nnnCONCLUSIONSnThe success rate was lower than those obtained in eyes without myopia or in myopic macular holes without retinal detachments. Macular hole closure may predict improved visual outcome for patients with retinal detachment and macular holes. Optical coherence tomography detects persistent macular holes in highly myopic eyes with retinal detachment.

Transretinal electrical stimulation by an intrascleral multichannel electrode array in rabbit eyes.

BackgroundA new method of stimulating the retina electrically, called suprachoroidal transretinal stimulation (STS), was shown to be effective in eliciting electrically evoked cortical potentials (EEPs) in Royal College of Surgeons (RCS) rats. Before extending this technique to patients, it is important to determine its safety and feasibility in eliciting EEPs from medium-size animal (rabbits). The purpose of this study was to determine the safety and efficacy of the surgical procedures used to implant an multichannel electrode array into a scleral pocket, and to determine whether the implanted electrodes can stimulate the retina effectively.MethodsThese acute experiments were conducted on six rabbits. An array of eight gold microelectrodes, embedded in polyimide, was implanted into a scleral pocket over the visual streak area. The size of the microarray was 2×4×0.180xa0mm. The reference electrode was implanted into the vitreous. The electrode array and reference electrodes were connected to a stimulator to deliver monophasic current pulses. Cortical responses were recorded with a stainless steel electrode implanted into each rabbit’s skull over the visual cortex. After the experiment, the eyes and electrodes were examined histologically.ResultsThe surgical procedures for electrode implantation were accomplished without serious complications. EEPs were recorded after monophasic electrical pulse stimulation from each electrode. The mean threshold for EEPs was 55.0±10.0xa0μA with a 0.5-ms duration inward current pulse. The charge delivered at threshold was about 27.5xa0nC, and the charge density was about 56.0xa0μC/cm2. Histopathological examination of the retinal tissue around the area of stimulation did not show damage at the light microscope level with the electrical parameters used.ConclusionsOur technique for STS with an intrascleral microelectrode array is safe in rabbit eyes, and EEPs were elicited by current densities that did not induce tissue damage. These results suggest that STS via intrascleral multichannel electrodes is a feasible method for stimulating the retina.

Transretinal Electrical Stimulation with a Suprachoroidal Multichannel Electrode in Rabbit Eyes

PurposeSeveral approaches for placing an electrode device for visual prosthesis have been previously proposed. In this study, we investigated if transretinal stimulation from the suprachoroidal space can elicit an electrical evoked potential (EEP) in albino rabbits.MethodsA flat electrode array (polyimide plate, platinum electrode) was developed and used for this study. After performing a scleral incision at 2–2.5 mm from the limbus and placing an anchoring suture, the array was inserted into the suprachoroidal space in the posterior portion of the eye by direct observation under a microscope. A platinum wire was implanted into the vitreous space as a reference electrode. For electrical stimulation, a biphasic pulse was used. When the electrode was stimulated, the EEP was recorded.ResultsWhen the electrical stimulation from the suprachoroidal space was applied, the EEP could be recorded with an epidural electrode, and the threshold was 66.0 ± 32.1μA (42.0μC/cm2). Histological examination indicated the absence of major damage to the retina and choroid from the insertion and placement of the array and the electrical stimulation.ConclusionsTransretinal electrical stimulation from the suprachoroidal space could elicit EEP, suggesting that this approach may be useful for a retinal prosthesis system.

Light scattering and optical aberrations as objective parameters to predict visual deterioration in eyes with cataracts

Purpose: To predict the visual deterioration of eyes with cortical (CC) or nuclear (NC) cataract from objective data on ocular higher‐order aberration (HOA) and forward (FLS) and backward light scattering (BLS). Setting: Osaka University Medical School, Osaka, Japan. Methods: Twenty‐two eyes with mild NC, 41 eyes with mild CC, and 11 normal eyes were examined. Higher‐order aberrations were calculated with the Zernike polynomials up to the fourth order from the values obtained by wavefront analysis using the Hartmann‐Shack aberrometer. Forward light scattering was calculated from the size of the aberrometer spot images for the central 4 mm, and backward light scattering (BLS) was calculated from the optical density of the Scheimpflug images. The relationship between the area under the log contrast sensitivity function (AULCSF) curve and HOAs, FLS, and BLS was examined. Results: Area under the log contrast sensitivity function was moderately correlated with the HOAs, FLS, and BLS. Multiple linear regression analysis revealed that the AULCSF was predicted by the linear combination of these variables (R2=.484, P<.001). Area under the log contrast sensitivity was predicted by BLS and HOA (R2=.555) in the NC group and by FLS and HOAs (R2=.540) in the CC group. Conclusions: Loss of contrast sensitivity was predominantly due to BLS and HOA in eyes with NC and FLS and HOA in eyes with CC. Higher‐order aberrations, FLS, and BLS, variables that are obtained objectively, can be used to predict quantitatively the visual deterioration in cataractous eyes.

Evaluation of residual retinal function by pupillary constrictions and phosphenes using transcorneal electrical stimulation in patients with retinal degeneration

BackgroundTo evaluate inner-retinal function by pupillary constrictions and phosphenes evoked by transcorneal electrical stimulation (TES) in patients with hereditary retinal degeneration.MethodsConsecutive 20 eyes of 20 patients (16 with retinitis pigmentosa (RP); and four with cone-rod dystrophy (CRD)) whose visual acuity was equal to or worse than 20/2000 at Osaka University Hospital and eight eyes of eight healthy subjects were enrolled. TES was performed on with a contact lens stimulating electrode. The electrically evoked pupillary response (EEPR) was recorded by a pupillometer, and the phosphenes by the subjective responses. Three electrical current thresholds were determined: T1, threshold current for initial phosphene; T2, threshold for eliciting a phosphene extending into the central field; and P, threshold for a relative pupillary constriction ≥3%.The EEPR and phosphene thresholds were compared with the visual acuity or the visual field.ResultsAll T1, T2 and P were significantly higher in patients than in normals (Mann-Whitney, P<0.001). Both T1 and T2 were not correlated with visual acuity but depended on the area and location of the residual visual field. T1 and T2 in RP eyes with a EEPR was significantly lower than that in RP eyes without an EEPR. During TES, all subjects and patients had no pain, and no complications except for a slight corneal superficial punctuate keratopathy.ConclusionsThe safety and the efficacy of TES to estimate the residual inner-retinal function in patients with retinal degeneration indicate that TES can be used as one of the most important test to select candidates for retinal prostheses.

Electrophysiological and histological studies of chronically implanted intrapapillary microelectrodes in rabbit eyes

PurposeTo determine the safety and efficacy of transsclerally placed intrapapillary wire microelectrodes implanted chronically into the optic nerve head of rabbit eyes.MethodsFour platinum wire microelectrodes were passed through the sclera and implanted into the optic nerve head of five rabbit eyes for 4–6 months. Color fundus photography, fluorescein angiography, electroretinograms (ERGs), and visually evoked potentials (VEPs) were used to monitor the retina. Electrically evoked potentials (EEPs) were elicited by bipolar electrical stimulation of the optic nerve axons by different combinations of the four electrodes immediately after the implantation and at 1-month intervals thereafter. The effects of the chronic implantation of the electrodes on the morphology of the optic nerve were evaluated by histological and immunohistochemical examinations at 4 and 6 months after the implantation.ResultsAll of the electrodes remained stable in the implanted sites throughout the post-implantation period, except for one electrode that had pulled out of the optic nerve head at 1 month after implantation. No intraocular infection, inflammation, or vitreoretinal proliferation was observed in any eye. EEPs could be elicited from each pair of electrodes at all testing times. The mean threshold currents (charge densities) to evoke EEPs increased from 19.3±9.2xa0μA (6.0±2.9xa0μC/cm2) on the implantation day to 78.8±31.9xa0μA (24.6±10.0xa0μC/cm2) at 1 month after implantation, but did not change significantly thereafter. The implicit time and amplitude of the a- and b-waves of the ERGs and of P1 of the VEPs did not change significantly throughout the post-implantation period. Histological evaluation of the optic nerve head revealed slight tissue encapsulations surrounding the electrode and increased expression of glial fibrillary acidic protein near the surface of the optic nerve.ConclusionsImplantation of transscleral intrapapillary microelectrodes appears to be safe and effective. These findings indicate that the implantation of microelectrodes in the optic nerve head should be considered for an optic nerve-based prosthesis.

Comparison of ocular higher-order aberrations and visual performance between photorefractive keratectomy and laser in situ keratomileusis for myopia

The purpose was to compare the ocular higher-order aberrations and the visual performance between photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Ocular aberrations and visual performance were measured after PRK in 26 eyes, after LASIK in 39 eyes, and in 29 normal myopic control eyes. Ocular aberrations were measured with a Hartmann-Shack aberrometer. Visual performance was evaluated with grating contrast sensitivity, high and low contrast visual acuity, and letter contrast sensitivity under full correction with spectacles. The results were that the root mean square (RMS) values of ocular higher-order aberrations after PRK or LASIK were significantly greater than that of normal controls for both 4-mm and 6-mm zones (PRK; 0.22 ± 0.09 and 0.85 ± 0.24µm, LASIK; 0.20 ± 0.06 and 0.82 ± 0.24µm, normal; 0.10 ± 0.03 and 0.33 ± 0.11µm. P < 0.05 between PRK and normal, LASIK and normal, One Way ANOVA on Ranks). There were no significant differences between PRK and LASIK. The ocular higher-order aberrations increased in proportion with the attempted refractive correction by PRK and LASIK. The ocular higherorder aberrations correlated better with grating contrast sensitivity, low contrast visual acuity, and letter contrast sensitivity than with high contrast visual acuity. There was no difference among normal, PRK and LASIK in all the visual function tests, except between normal and PRK, or between normal and LASIK with letter contrast sensitivity. In conclusion, there was no difference in both ocular higher-order aberrations and visual performance between PRK and LASIK. The result suggests that surgeons can choose refractive procedures according to the corneal conditions or daily activities of patients.