• Internal Limiting Membrane Peeling in Macular Hole Surgery
• Perifoveal Capillary Blood Flow Velocity in Diabetic Macular Edema
• Deep Lamellar Keratoplasty With Intracorneal Dissection
• Relative Afferent Pupillary Defect in Optic Tract Lesions
July’s American Journal of Ophthalmology:
• Comparison of Auto Refraction and Subjective Refraction in Schoolchildren
• Intravitreal Bevacizumab for Choroidal Neovascularization
• Artisan Phakic Intraocular Lens Implantation for the Correction of Myopia
June’s Archives of Ophthalmology:
• Racial and Ethnic Differences in Vision Care Among Children With Special Needs
• Lesion Morphology in AMD and Its Therapeutic Significance
• Study of Fuchs’ Corneal Endothelial Dystrophy Leading to PK
Roundup of Other Journals:
• Using Nanotechnology for Brain Repair and Axon Regeneration
• Switchable Electro-Optic Diffractive Lenses for Presbyopia
• Assessing of Telemedicine
• Clarifying Linear Patterns of Chorioretinitis Associated With West Nile Virus
Internal Limiting Membrane Peeling in Macular Hole Surgery
Tognetto et al. reviewed 1,627 records of patients with idiopathic macular holes who underwent a single pars plana vitrectomy and were divided into two groups, with and without internal limiting membrane (ILM) peeling.
The researchers found 89 percent of patients had hole closures in the ILM non-peeled group and 94.1 percent in the ILM peeling group. While ILM peeling appeared to improve hole closure for stage 3 and 4 macular holes and for long-lasting holes, risk factors for surgical failure included higher-stage macular holes and holes with longer duration of symptoms. In patients where hole closure was achieved, no difference in functional results was seen between pseudophakic peeled and not-peeled patients. In contrast, phakic patients experienced a better functional result when not peeled. In the peeling group, anatomical success was more frequent when indocyanine green was not used.
Patients with stage 3 and 4 holes, and those with holes lasting for more than 24 months, may benefit from ILM peeling.
Perifoveal Capillary Blood Flow Velocity in Diabetic Macular Edema
In an effort to elucidate the pathogenesis of DME, Sakata et al. examined the relationship between blood flow velocity (BFV) in perifoveal capillaries and retinal thickness at the central fovea in 22 diabetic patients with clinically significant macular edema (CSME). Also included in the study were 22 matched diabetic patients without CSME and 16 healthy volunteers.
The researchers found that BFV in the diabetic patients with CSME was significantly slower than the diabetic patients without CSME and the healthy volunteers. In addition, BFV reduction negatively correlated with retinal thickness at the central fovea. Interestingly, capillary BFV varied widely in the diabetic patients without CSME, ranging from a nearly normal capillary network to abnormalities in the capillary vessels such as enlargement and destruction of the foveal avascular zone.
Given these results, the authors conclude that measurement of perifoveal capillary BFV could help shed light on the pathogenesis of diabetic macular edema and its progression.
Deep Lamellar Keratoplasty With Intracorneal Dissection
Marchini et al. utilized confocal microscopy to document a surgical technique for manual deep lamellar keratoplasty (DLKP) that involves intentional sparing of the most posterior stroma.
The prospective, 12-month study involved 46 eyes of 45 patients who had corneal pathologic features without endothelial abnormalities and required corneal graft surgery. They were treated with a surgical technique that involved an intracorneal deep manual stromal dissection through a 4-mm limbal incision at 50 µm from Descemet’s membrane. An endothelial free graft was sutured after trephination. The morphologic characteristics of the donor-host interface after DLKP significantly correlated with visual performance following surgery. In addition, the technique resulted in good visual improvement with a limited incidence of intraoperative complications. Visual recovery took up to one year; progressive reduction of interface reflectivity correlated with increases in subsequent best-corrected visual acuity.
The findings suggest that in vivo confocal microscopy may be used quantitatively to assess how interface reflectivity affects visual acuity in lamellar grafts.
Relative Afferent Pupillary Defect in Optic Tract Lesions
Patients with optic tract lesions provide an opportunity to understand the hemifield organization of the afferent pupillomotor system.
Kardon et al. studied five patients with a unilateral optic tract lesion to show how the number of intact retinal ganglion cells corresponds to their maximal firing rate, which in turn is reflected by their maximal pupil light response. In all patients, the pupil response from the intact functional temporal hemifield was greater than that from the functioning contralateral nasal hemifield. The percentage of decussating pupil fibers did not correlate with the relative afferent pupillary defect (RAPD), which corresponded more to the difference in shape of the stimulus-response function between the two eyes.
The findings illustrate that estimation of light sensitivity, such as with RAPD, may not be helpful for estimating the number of functioning neurons. The results also help explain the dissociations observed between measures of light sensitivity and axon number in optic nerve disorders such as glaucoma.
Comparison of Auto Refraction and Subjective Refraction in Schoolchildren
American Journal of Ophthalmology
Obtaining accurate refractions in children and even some adults can be a challenge. Choong et al. evaluated the accuracy of auto refraction using three auto refractors and compared this with the subjective refraction in diagnosing refractive error in children.
In this cross-sectional, community-based sample study, 117 children underwent auto refraction using three auto refractors and subjective refraction with and without cycloplegia. Spherical power, cylindrical power and spherical equivalence (SE) were measured.
Without cycloplegia, the mean SE was significantly different for Retinomax K plus 2 (P < 0.0001) and Canon RF10 (P = 0.0023) compared with monocular subjective refraction. Mean SE was significantly different for Grand Seiko WR- 5100K (P = 0.0002) compared with binocular subjective refraction. With cycloplegia, there was no significant difference between refraction methods.
Sensitivity and specificity results for the diagnosis of myopia without cycloplegia: Retinomax K plus 2 (sensitivity 1.0, specificity 0.51); Canon RF10 (sensitivity 0.92, specificity 0.81) and Grand Seiko WR5100K (sensitivity 0.91, specificity 0.98). And with cycloplegia: Retinomax K plus 2 (sensitivity 0.97, specificity 0.99); Canon RF10 (sensitivity 0.97, specificity 0.96) and Grand Seiko WR- 5100K (sensitivity 1.0, specificity 0.97).
Under noncycloplegic conditions, all three auto refractors have a tendency toward minus overcorrection in children resulting in overdiagnosis of myopia. However, auto refractors seem accurate under cycloplegic conditions.
Intravitreal Bevacizumab for Choroidal Neovascularization
American Journal of Ophthalmology
Intravitreal bevacizumab (Avastin) is frequently used off-label. Bashshur et al. investigated the efficacy and safety of intravitreal bevacizumab for choroidal neovascularization due to AMD.
In a prospective, interventional case series, 17 eyes of 17 patients with subfoveal CNV due to AMD were treated. All patients had failed, refused or were not eligible for photodynamic therapy. All eyes received a baseline eye examination, which included best-corrected visual acuity, dilated fundus examination, ocular coherence tomography and fluorescein angiography. An intravitreal injection of bevacizumab (2.5 mg/0.1 mL) was given at baseline and followed by two additional injections at four-week intervals. BCVA, OCT and fluorescein angiography were repeated four weeks after each injection. Main outcome measures were improvement in BCVA and central retinal thickness (CRT).
Mean baseline BCVA was 20/252 (median 20/200), and baseline CRT was 362 µm (median 350 µm). Improvement in VA and CRT occurred by the fourth week. At 12 weeks, mean BCVA was 20/76 (P < 0.001) and median BCVA was 20/50 (P < 0.001). Both mean and median CRT decreased to 211 µm (P < 0.001). Thirteen (76 percent) of 17 eyes had total resolution of subretinal fluid, and four eyes (24 percent) had BCVA better than 20/50. No systemic or ocular side effects were noted at any time.
Eyes with CNV due to AMD treated with intravitreal bevacizumab had significant anatomic and visual improvement. The authors caution that further studies are necessary to confirm the long-term efficacy and safety of this treatment.
Artisan Phakic Intraocular Lens Implantation for the Correction of Myopia
Archives of Ophthalmology
Phakic IOLs are an alternative therapy for correction of myopia. Tahzib et al. determined patient satisfaction after Artisan phakic intraocular lens (IOL) implantation to correct myopia.
In a noncomparative, prospective case series 120 eyes of 60 patients who had undergone Artisan phakic IOL implantation to correct myopia were analyzed. A validated questionnaire that consisted of 66 satisfaction items was self-administered by patients 12 months after surgery. Clinical parameters (phakic IOL decentration, the difference between pupil size and phakic IOL optical zone, and optical aberrations) were measured. Main outcome measures of satisfaction scale scores (global satisfaction, quality of uncorrected and corrected vision, night vision, glare, and day and night driving) were analyzed. Correlations with clinical parameters were obtained.
After surgery, 98 percent of patients were satisfied, and 73 percent considered their night vision to be the same or better; 44 percent of patients reported more bothersome glare. The night vision score correlated with spherical aberration. The glare score correlated with the difference between scotopic pupil size and phakic IOL optical zone and vertical coma. The night driving score correlated with postoperative spherical equivalent, total root mean square aberrations, higher- order root mean square aberrations and vertical coma. Overall satisfaction after Artisan phakic IOL implantation for myopia seems to be good. The quality of night vision and night driving were related to scotopic pupil size, individual higher-order aberrations and residual refractive error.
Racial and Ethnic Differences in Vision Care Among Children With Special Needs
Archives of Ophthalmology
Heslin et al. examined racial/ethnic differences in unmet need for vision care among 14,070 children in the National Survey of Children with Special Healthcare Needs. Because children with special health care needs (CSHCN) are often unable to report what they can see during conventional eye examinations, they may require more extensive and individually tailored treatment of their vision than children without special needs. It is critical to examine unmet need for vision care among CSHCN, because poor access to vision care early in life places them at increased risk of delays in long-term educational and social development.
In this cross-sectional telephone survey, a random-digit-dial sample of households with children under 18 was selected from the 50 states and the District of Columbia. Respondents were adults who knew the most about the child’s health. Children who did not receive all the eyeglasses or vision care they needed in the previous 12 months were considered to have “unmet need for vision care.”
Results showed that 6 percent of children with special health care needs in the United States had unmet need for vision care. Compared with whites, children of African-American, Latino and multiracial backgrounds had approximately twice the adjusted risk of unmet need, whereas American Indian/Alaskan Native children had lower adjusted risk. Health care providers, school personnel and insurance coverage also contributed to differences in the risk of unmet need, independently of child race/ethnicity. Of particular policy relevance is the finding that children covered by Medicaid or the State Children’s Health Insurance Program had lower risk of unmet need than did children with private insurance.
The authors note that differences persisted even after accounting for school and health care provider characteristics, which suggests that these resources should be leveraged to increase the availability of vision care for all CSHCN.
Lesion Morphology in AMD and Its Therapeutic Significance
Archives of Ophthalmology
Beaumont and Kang retrospectively examined the lesion morphology in 3,580 consecutive cases of neovascular age-related macular degeneration presenting over a 25-year period in nontrial clinical settings.
A significant proportion of this series (26.2 percent) presented with juxtafoveal or extrafoveal lesions. After 792 cases with disciform lesions were excluded, 72.2 percent of the subfoveal, 88.1 percent of the juxtafoveal and 87.7 percent of the extrafoveal lesions were found to consist of at least 50 percent CNV. At all locations, 90 percent or more of the lesions in which CNV occupied at least 50 percent of the lesion area contained either classic or occult CNV but not both. Mixed CNV lesions, which included predominantly classic CNV with occult and minimally classic lesions, accounted for 10.2 percent of subfoveal, 5 percent of the juxtafoveal and 4.5 percent of the extrafoveal lesions.
Subfoveal lesions were significantly larger than juxtafoveal or extrafoveal lesions. Mixed CNV lesions tended to be larger than lesions containing only one type of CNV. The mean lesion sizes in this series were significantly smaller than those reported in TAP and VIP trials. Overall, photodynamic therapy or photocoagulation could be offered to 53 percent to 69 percent of the nondisciform lesions, depending on how strictly eligibility guidelines were applied.
The authors conclude that the lesion composition found in clinical settings differed significantly from that found in major trials. The low proportion of mixed CNV lesions and smaller lesion size suggest that treatments such as photodynamic therapy are likely to be more effective in clinical settings.
Study of Fuchs’ Corneal Endothelial Dystrophy Leading to PK
Archives of Ophthalmology
Afshari et al. studied features of patients with Fuchs’ corneal endothelial dystrophy leading to penetrating keratoplasty over 30 years.
Four hundred twenty-four patients (546 eyes) were diagnosed histopathologically as having Fuchs’ and underwent corneal transplantation. Mean age at the time of PK was 69.2 years. Women represented 77.6 percent of patients. Bilateral PK was performed in 28.8 percent of the eyes, and the mean interval between keratoplasties was 3.2 years. Patients with positive family history underwent corneal transplantation a mean of five years earlier and were more likely to require bilateral transplantation. Patients with bilateral transplants were twice as likely to have a positive family history compared with those who had unilateral transplant. Pachymetry did not correlate with visual acuity. The mean time from cataract extraction to transplant was 2.2 years.
The authors conclude that Fuchs’ corneal dystrophy predominantly affects women and is often familial. Pachymetry-determined corneal thickness was a poor predictor of visual acuity until extreme levels of corneal edema were reached. Cataract extraction in an eye with Fuchs’ dystrophy leads to earlier PK.
Ophthalmology summaries are written by Lori Baker Schena and edited by John Kerrison, MD. American Journal of Ophthalmology summaries are edited by Thomas J. Liesegang, MD. Archives of Ophthalmology summaries are written by the lead authors.
Roundup of Other Journals
Using Nanotechnology for Brain Repair and Axon Regeneration
Proceedings of the National Academy of Sciences
Nanotechnology has been used successfully in materials fabrication, microelectronics and microfluidics. Ellis-Behnke et al. have extended this concept to biomedicine in an effort to repair injured brain structures.
In this study, the researchers describe their successful attempt to design a peptide nanofiber scaffold to create a permissive environment for axons not only to regrow through the site of an acute injury but also to knit the brain tissue together. To test this self-assembling peptide nanofiber scaffold (SAPNS) treatment, the researchers used a severed optic tract in a hamster model. They found that the SAPNS allowed significant axonal regrowth through the site of the lesion, and a return of functional vision.
The key advance is the fact that the researchers were able to create an environment for axonal regeneration that allowed growth through the center of a lesion, an objective that had not been possible in other experimental approaches. Their work has shown that with a single SAPNS treatment at the site of injury, it is, in fact, possible to overcome a major barrier to CNS regeneration in the optic tract of hamsters. Eventually, this finding may lead to effective treatment of CNS and other trauma.
Switchable Electro-Optic Diffractive Lenses for Presbyopia
Proceedings of the National Academy of Sciences
For ophthalmologists helping patients better cope with the frustrating effects of presbyopia has been an elusive goal. The current state-of-the-art, bifocal lenses are suboptimal, providing limited view, causing the reader to gaze down to accomplish near-vision tasks and sometimes causing dizziness.
Li et al. report on switchable, flat, liquid-crystal diffractive lenses that can adaptively change their focusing power. These lenses incorporate electrical control of the refractive index of a 5-µm-thick layer of nematic liquid crystal using a circular array of photolithographically defined transparent electrodes. The lenses operate with high transmission, low voltage, fast response, diffraction efficiency, small aberrations and a power-failure-safe design.
The researchers assert that these advanced liquid-crystal diffractive lenses could potentially “revolutionize” presbyopia correction when combined with automatic adjustable focusing power.
Assessing of Telemedicine
British Journal of Ophthalmology
Published online May 1, 2006
Diagnosing retinopathy of prematurity (ROP) can be challenging given the dearth of ophthalmic expertise in many neonatal intensive care units across the country and worldwide. The emerging field of telemedicine using computer-based transmission of patient data interpreted by remote experts holds great promise in ROP detection, but is it feasible?
In this study by Chiang et al., three trained ophthalmologist readers reviewed 410 images from 64 hospitalized infants who met ROP examination criteria. The readers classified the images into one of four categories: no ROP, mild ROP, type-2 prethreshold ROP, or treatment-requiring ROP. Once the images were categorized, they were compared with a reference standard of dilated ophthalmoscopy.
The researchers found that the accuracy of remote ROP detection was dependent on diagnostic cutoff values. Remote interpretation was highly accurate for the detection of treatment-requiring ROP, but less so for detection of mild or worse ROP, a finding consistent with results from previous studies. They conclude that while telemedicine ROP screening is currently technically feasible, areas of improvement include standardization of the image capture process, and examination of cost-benefit trade-offs of unnecessary overreferrals or failure to detect disease.
Clarifying Linear Patterns of Chorioretinitis Associated With West Nile Virus
Published online April 21, 2006
One of the early and frequent findings in West Nile virus (WNV) infection is multifocal chorioretinitis with typical funduscopic and fluorescent angiographic appearance of chorioretinal lesions. In this study, Khairallah et al. set out to clarify the reason for the linear clustering of chorioretinal lesions, a prominent feature occurring in more than 80 percent of eyes with WNV-associated chorioretinitis.
The researchers conducted a complete ophthalmic evaluation of 12 patients with bilateral WNV-associated multifocal chorioretinitis. They found that the course of the lesions in all cases appeared to closely follow the course of the retinal nerve fibers, rather than the course of retinal or choroidal vessels. The authors contend that this finding suggests a contiguous spread of WNV from the central nerve system via the optic nerve fibers to the outer retina, retinal pigment epithelium and choroid, rather than a hematogenous dissemination to the choriocapillaris.
In conclusion, the investigators put forth a neural hypothesis for the WNV-associated chorioretinitis patterns, and they call for further investigation, which could contribute to a better understanding of the pathogenesis of ocular involvement in WNV infection. Roundup of Other Journals is written by Lori Baker Schena and edited by Deepak P. Edward, MD.
Roundup of Other Journals is written by Lori Baker Schena and edited by Deepak P. Edward, MD.