Contrast (Modulation) Sensitivity Functions measured in patients with high refractive error with emphasis on aphakia: II. Determinations on patients

Measurements of Contrast Sensitivity Functions (CSF) were made on normal observers made artificially highly ametropic with spectacle lenses (with high back vertex) distance in order to determine the effect of retinal image size alterations upon CSF measures. While not an exact model for high ametropia per se, this experiment served to familiarize the experimenters with problems associated with the task.Image size alterations occur normally in aphakic patients and highly myopic patients. As a clinical trial, a series of aphakic observers were tested using an interferometric acuity device. CSF measures were made with the patient's spectacle corrections in place and again with correcting contact lenses substituted. The contact lenses reduce induced image size alterations in these cases. The use of contact lenses in such measures allows differentiation between artifactual low frequency fall off in aphakia due to lens effects and possible low frequency fall-off due to other causes.On temporary leave from Department of Ophthalmology, University of Florida College of Medicine, Gainesville, Florida, USA. Reprint request to Professor H. Ohzu, Waseda University.This work has been supported in part by a grant from the Japanese Society for the Promotion of Science and in part by National Eye Institute Grant No. EY 01418 (to JME), NIH, Bethesda, Maryland, USA.     

Early surgery and visual correction of an infant born with unilateral eye lens opacity

A healthy neonate born with unilateral cataract was operated upon on Life Day 4. Visual correction and testing were initiated promptly. Resolution showed continuous improvement in the normal eye, with no improvement noted in the operated eye until adequate visual correction was provided. Following correction there was prompt marked improvement of visual resolution.Department of Ophthalmology, University of Florida College of Medicine, Gainesville, Florida 32610, USA.This research has been supported in part by Research Grant No. EY 01418 (to JME), National Eye Institue, NIH, Bethesda, Md.This research has been supported in part by a research grant from the National Eye Institute (EY-01418, to JME) National Institutes of Health, Bethesda, MD. The authors also wish to express their appreciation to Soft Lenses, Inc., of San Diego and the Bausch and Lomb Corp., Rochester, NY for their cooperation in supplying the necessary lens materials.     

Ectopia lentis,chorioretinal dystrophy and myopia

Four of five siblings born of a consanguineous marriage demonstrated abnormalities of the lens (ectopia lentis and dense cataracts) and retina (generalized tapetoretinal dystrophy and total retinal detachment) associated with myopia. This association in an autosomal recessive pedigree has not been previously noted.Presented in part at the Annual Meeting of the Association for Research in Vision and Ophthalmology, Sarasota, Florida, USA, 28 April to 3 May 1991.     

A tribute to Charles David Kelman MD: ophthalmologist, inventor and pioneer of phacoemulsification surgery

Charles David Kelman was born in Brooklyn, New York, USA, on 23 May 1930 and passed away in Boca Raton, Florida, USA, on 1 June 2004 at the age of 74 years after a long battle with cancer. He received a Bachelor of Science degree from Tufts University in 1950 and completed medical studies at the University of Geneva, Switzerland, in 1956. He was Clinical Professor of Ophthalmology at New York Medical College and an Attending Surgeon at New York Eye and Ear Infirmary and Manhattan Eye, Ear and Throat Hospital. Although a prolific inventor, he will be best remembered for developing phacoemulsification, following his realization while sitting in a dentist's chair, that ultrasonic vibrations could be used to emulsify the aged crystalline lens through a very small incision. His pioneering work revolutionized cataract surgery. He also pioneered cryo-extraction of cataracts, the use of freezing for the repair of retinal detachments and designed numerous ophthalmic instruments and intraocular lenses. Dr Kelman received numerous awards, including the American Academy of Ophthalmology Achievement Award (1970), the Ridley Medal from the International Congress of Ophthalmology (1990), and the Inventor of the Year Award from The New York Patent, Trademark and Copyright Law Association (1992). Most recently (2003), Dr Kelman was honoured by the American Academy of Ophthalmology with the Laureate Recognition award. Dr Kelman was also an accomplished Broadway producer, composer and jazz saxophonist. With his demise, the ophthalmic and medical community lost a famed inventor with multifaceted talents and one of the great ophthalmologists of the twentieth century.     

Scotopic sensitivity and color vision with a blue-light-absorbing intraocular lens

PURPOSE: To investigate possible adverse effects of a yellow-tinted intraocular lens (IOL) on scotopic sensitivity and hue discrimination. SETTING: Departments of Ophthalmology, Columbia University and New York University School of Medicine, New York, New York, USA. METHODS: Nine patients with a yellow-tinted IOL in 1 eye and a colorless ultraviolet IOL in the fellow eye and 9 young phakic subjects with and without a yellow-tinted clip-on lens were tested. Hue discrimination was measured with the Farnsworth-Munsell (FM) 100-hue test. Dark-adapted thresholds to 440 nm, 500 nm, and 650 nm lights were measured at 23 locations using a modified Humphrey perimeter, and dark-adapted thresholds to white light were measured at 15 degrees temporal retina. RESULTS: In the 9 patients, there were no significant differences in dark-adapted sensitivities to 440, 500, 650 nm, or white-light stimuli and no differences in FM 100-hue error scores between eyes with yellow-tinted IOLs and those with colorless IOLs. Similarly, in young phakic subjects, there were no significant differences in FM 100-hue error scores or dark-adapted sensitivity to the white light with and without the yellow-tinted clip-on lens. However, with the clip-on lens, mean sensitivities to the 440 nm, 500 nm, and 650 nm stimuli were significantly decreased by 2.7 to 2.8 dB, 0.7 to 1.0 dB, and 0 to 1.2 dB, respectively. CONCLUSION: Results suggest that implantation of a yellow-tinted IOL has non-significant effect on scotopic sensitivity and hue discrimination.     

Effect of ophthalmic viscosurgical devices on lens epithelial cells: a morphological study

PURPOSE: To investigate the morphological effects of Viscoat (sodium hyaluronate 3.0%-chondroitin sulfate 4.0%) on lens epithelial cells (LECs). SETTING: Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA, and the Laboratory of Ultrastructural Morphology, Zoological Institute, University of Liège, Liège, Belgium. METHODS: Human LECs collected via capsulorhexis were examined by light microscopy (LM) and transmission electron microscopy (TEM). Lens epithelial cells from rabbit capsulorhexis samples were studied by LM and TEM following exposure to Provisc (sodium hyaluronate 1.0%) or Viscoat ophthalmic viscoelastic device (OVD). Since Viscoat is hypertonic (340 mOsm), hypertonic, isotonic, and hypotonic solutions were compared to investigate a possible mechanism for the observed effects. The effects of Provisc and Viscoat on rabbit LECs in the intact lens were also compared. RESULTS: Human LECs gathered via capsulorhexis following exposure to Viscoat were generally thinner than control samples and often had condensed nuclei and increased intracellular vacuolization. Rabbit capsular tissue exposed in situ to Viscoat demonstrated changes similar to those seen in humans. Cells exposed to Provisc were similar to cells in untreated controls in humans and rabbits. Corneal endothelial cells exposed to either agent were unaffected. Experiments with hypertonic and hypotonic buffers induced some of the changes noted with Viscoat, but the effects were less severe. Lens epithelial cells in intact rabbit lenses exposed to Viscoat appeared similar to LECs in the control samples. CONCLUSIONS: Light microscopy and TEM of human lens capsule tissue suggest that Viscoat induces significant morphological changes in LECs during cataract surgery. The changes may underlie the improved visualization of these cells that has been reported during cataract surgery. Corneal endothelial cells were unaffected by exposure to Viscoat. Studies in a rabbit model suggest that the hyperosmolarity of Viscoat may play a partial role in the LEC changes.     

Intraocular diathermy coagulation

Previously used transvitreal diathermy systems were found to be less than adequate. A new, safer 1.25 MHz medium frequency bipolar instrument is presented, which obviates most of the earlier drawbacks. Coagulation at the retinal surface can be obtained with as little as 0.15 J.This investigation was supported in part by the Florida Lions Eye Bank, Miami, Florida; the Veterans Administration Medical Center (Project No. 5421-01), Miami, Florida; Public Health Research Grants EY-02180 and EY-02903, from the National Eye Institute, National Institutes of Health, Bethesda, Maryland 21205; and Research to Prevent Blindness, Inc., New York, New York, USA     

Correction of hyperopia with intracorneal implants

PURPOSE: To evaluate the safety and efficacy of intracorneal lenses as a surgical alternative for the correction of hyperopia. SETTING: Al-Azhar University, Cairo, Egypt, and Louisiana State University Eye Center, New Orleans, Louisiana, USA. METHODS: PermaVision lenses (Anamed Inc.) were implanted in the left eye of 20 albino rabbits that were followed for 6 months by confocal microscopy. The lenses are made of a highly permeable hydrogel with 70% water content and a refractive index close to that of corneal tissue (1.376). The Carriazo-Barraquer microkeratome (Moria) was used to create a 150 microm corneal flap with a diameter of 8.5 mm or larger. The intracorneal lens was placed under the flap after minimal interface irrigation. RESULTS: At 3 days, confocal microscopy showed interface edema that resolved after 1 week. No flap melting or excursion of the lens was noted. In 1 eye, a deep lamellar keratitis was seen. At 6 months, the edge of the lens showed excellent compatibility, with no keratocytic activity or intrastromal fibrosis. CONCLUSIONS: Intracorneal hydrogel lenses were well tolerated by stromal tissue in rabbits. They are potentially safe and can be considered as an alternative for the correction of hyperopia. Further clinical studies are required to confirm their safety in humans.     

Effects of diabetes on anterior ocular structure and function

Diabetes is a systemic disease that affects multiple organs including the entire eye. Although diabetic retinopathy is the main cause for vision loss in patients with diabetes, many anterior segment abnormalities have been described, including structural changes in the tear film, the conjunctiva, and the corneal epithelial and endothelial cells. Functional alterations in corneal wound healing, corneal sensitivity, and recovery from contact lens-induced edema also accompany diabetes, and this raises the issue of whether contact lens wear may be contraindicated in these patients. To address this issue, eye care providers must be able to recognize the effects of diabetes on the anterior ocular surface, understand the biochemical mechanism(s) believed to be responsible for these alterations, and determine the relevance of observed changes with respect to contact lens wear.     

Lens epithelial cell response to isoforms of platelet-derived growth factor

It has been reported previously that platelet derived growth factor (PDGF) may play an important role in the regulation of lens growth and differentiation. To evaluate PDGF-induced effects at the cellular level, we investigated the response of cultured bovine lens epithelial cells (BLEC) to PDGF-AB, -AA, and -BB isoforms at the cellular level. Stimulation of BLEC with PDGF isoforms showed no increase in cell proliferation under the culture conditions of this study. In contrast, measurement of cytosolic free calcium concentration ([Ca²⁺]_i), which has been shown to be an important second messenger for controlling multiple cellular processes in the lens, revealed a dose-dependent rise in [Ca²⁺]_i upon stimulation with PDGF-AB and -BB isoforms. PDGF-AA used in similar concentrations was not effective. Our data suggest that PDGF-AB and -BB may play a role in the regulation of cellular functions in BLEC via modulation of intracellular calcium homeostasis.Presented in part at the annual meeting of the Association for Research in Vision and Ophthalmology, Sarasota, Florida, May 1991     

A Comparison of a Monofocal Acrysoft IOL Using the “Blended Monovision” Formula with the Multifocal Array IOL for Glasses Independence After Cataract Surgery

We compared the Acrysoft monofocal intraocular lens (IOL) in the mini monovision formula (n = 20) with the Array multifocal intraocular lens (n = 20) for glasses independence after cataract surgery. The Acrysoft monofocal IOL group showed similar and even slightly better results than the Array multifocal IOL group. The monofocal Acrysoft IOL using the mini monovision (blended vision) formula is a good alternative for providing post-cataract surgery glasses independence. Drs. Chen, Clinical Assistant Professor of Ophthalmology and Neal H. Atebara are at University of Hawaii School of Medicine, Honolulu, Hawaii, USA. Dr. Te Tsaw Chen, Past Professor & Director, was at Department of Ophthalmology, Taipei Medical University, Taipei, ROC. The authors have stated that they do not have a significant financial interest or other relationship with any product manufacturer or provider of services discussed in this article. The authors also do not discuss the use of off-label products, which includes unlabeled, unapproved, or investigative products or devices. The authors compared the Acrysoft monofocal intraocular lens in the mini monovision formula to the Array multifocal intraocular lens for glasses independence after cataract surgery.     

Combined toric intraocular lens implantation and relaxing incisions to reduce high preexisting astigmatism

PURPOSE: To evaluate whether combining toric intraocular lens (IOL) implantation with astigmatic keratotomy (AK) can correct higher levels of astigmatism while minimizing undue effects on the optical qualities of the cornea. SETTING: St. Luke's Cataract and Laser Institute, Tarpon Springs, Florida, USA. METHODS: Thirteen eyes with corneal astigmatism greater than 2.50 diopters (D) (mean 5.54 D) had implantation of a Staar toric IOL combined with AK. RESULTS: All eyes had less than 1.00 D of refractive astigmatism postoperatively. Sixty-nine percent achieved an uncorrected visual acuity of 20/40 or better, and no patient lost best corrected visual acuity. CONCLUSIONS: Implanting a toric IOL in patients with high astigmatism reduced the amount of incisional surgery required. Combining techniques can correct all or most of even very high astigmatism (>5.00 D) while avoiding induced corneal irregularities.     

Development of a repeatedly adjustable intraocular lens

PURPOSE: To provide a variable-focus intraocular lens (IOL) that is able to adjust repeatedly and reversibly. SETTING: University of Missouri-Rolla, Rolla, and Eggleston Adjustable Lens, St. Louis, Missouri, USA. METHODS: An adjustable IOL based on a mechanically adjustable design has been developed. Prototypes were fabricated from traditional Perspex CQ poly(methyl methacrylate) (PMMA) provided off the shelf by a current IOL manufacturer. The prototypes have undergone proof-of-concept testing per the requirements of National Institutes of Health grant 1 R41 EY13482-01, with specific attention to the feasibility and safety of continuing development of the lens with in vivo trials. The experimental results presented focus on operational force measurements. RESULTS: Prototype lenses were produced consistently. Operational force measurements indicated that use of the mechanical adjustment mechanism is viable for an adjustable IOL and provides repeated adjustments over time. Turning forces exhibited by the prototypes were low enough to suggest that operation of this adjustable IOL will not damage the capsular bag or ciliary body of the eye, a potential concern in using this design. Biocompatibility and optical quality of the prototype lenses are ensured by use of traditional Perspex CQ PMMA. CONCLUSIONS: The mechanically adjustable IOL provides a feasible and promising means of confronting postoperative refractive errors and the changing desires of patients. The viability of this IOL design has been proven, and results suggest that operation of the lens is safe enough to pursue in vivo trials. Evaluation of the biocompatibility of the lens architecture as well as the ultimate goal of noninvasive adjustment using this model are reported in a companion article.     

Corneal pathophysiology with contact lens wear

Contact lens wear induces a wide spectrum of changes in the appearance and function of the cornea. The most salient effect of lens wear is the hypoxically induced reduction in the rate of metabolic activity of the corneal epithelium and its sequellae. Other important alterations to corneal health associated with contact lens wear may be caused by antigenic and toxic stimuli, mechanical forces, osmotic effects and carbon dioxide retention. Perhaps the most important task facing the contact lens clinician is to distinguish between an acceptable state of physiological modification and an anomalous or pathological state of hypofunction. In this article, we review the assortment of corneal changes primarily on the basis of the causative agents and time scale with reference to the physical and chemical processes leading to the observed signs or symptoms. This procedure allows a strong foundation for understanding the etiology and management principles for the variety of effects that contact lenses may have on the cornea.     

In vivo redirection of retinal blood flow into borosilicate micro-cannulas in rabbits

Background Microvascular manipulation is one application in the emerging field of retinal vascular surgery that could lead to new therapeutic approaches for retinal disease. Research in this field has largely focused on vessel cannulation and injection of vasoactive substances. This study expands on applications for retinal vessel manipulation by demonstrating that redirection of retinal blood flow in vivo can be achieved through retinal vessel cannulation in a rabbit model.Methods Dutch-belted rabbits were anesthetized, and a sectoral peritomy and sclerotomy 1 mm from the superotemporal limbus were performed. Borosilicate glass microtips with external diameters of 10–20 μm were introduced into the vitreous through the sclerotomy site. Using an operating microscope and a direct contact lens for visualization, we cannulated the rabbits’ retinal vessels, and blood flow was redirected through the microtips.Results Retinal vessels approximately 30–60 μm in size were cannulated, and controlled blood flow through the microcannula was demonstrated with minimal or no vitreous hemorrhage. Though still achievable, flow after arterial cannulation was more difficult to demonstrate.Conclusions This study demonstrates that partial diversion of blood flow from a native vessel lumen could be successfully accomplished by retinal vessel cannulation. This early work indicates that more advanced retinal vascular procedures, such as vessel bypass around a thrombus or shunting blood towards an area of ischemic retina, may be feasible in the future.A portion of this work was presented at ARVO 2005, Fort Lauderdale, Florida, USA. Supported in part by the Vitreoretinal Research Fund (Dr. D’Amico) and the Iacocca Foundation     

Biochemical analysis of young rats homozygous for the cataract mutation cat

Cataractogenesis was studied in young rats homozygous for the radiation-induced recessive cataract mutation cat. Homozygous cat/cat rats have reduced body weight (about two-thirds of the wild type) when 3 weeks old. The litter size is also diminished to about two-thirds of the wild type. For lens-specific parameters, as compared with homozygous wild type, the wet weight of the cataractous lenses is reduced, although the concentration of water-soluble lens proteins per wet weight is the same. No major alterations could be detected in the pattern of the water-soluble lens proteins separated by isoelectric focusing or gel electrophoresis run with or without mercaptoethanol. Additionally, no statistically significant alterations could be detected in the biochemical parameters of the lens used as indicators for osmotic stress (water content of the lens and the Na+-K+-dependent ATPase), for the energy state (ATP) and for the redox state (oxidized glutathione and superoxide dismutase). In contrast, the activity of transglutaminase is significantly enhanced in lenses as well as in the liver of young cat-rats, which might be understood as a biochemical marker for alterations in the developmental program. Cataractogenesis in the cat-rat is, therefore, suggested to be part of a syndrome including dwarfism and reduced litter size.     

Phaco-Ersatz: Cataract surgery designed to preserve accommodation

Phaco-Ersatz represents a new approach to cataract surgery and the correction of aphakia. The procedure involves the removal of the cataractous cortex and nucleus while preserving the lens capsule and its zonular attachments. The empty lens capsule is then refilled with biocompatible and optically suitable clear gel. A physiologic lens is recreated in situ. Experimental work with human cadaver eyes and rabbit and cat eyes in vivo demonstrates this surgical feasibility. A review of the literature reveals contradicting theories regarding the physical laws and lens properties governing accommodation. The accommodative potential of the ersatz lens has not been tested, but it may be speculated that this recreated lens may, in fact, possess some accommodative properties. Experimental investigations in this area represent the logical extension of intraocular lens implant development.Presented in part at the Eighty-sixth Annual Meeting of the American Academy of Ophthalmology, Atlanta, November 1–6, 1981; at the 126th Annual Meeting of the Dutch Ophthalmological Society, The Netherlands, March 18–20, 1982; at the Annual Spring Meeting of the Association for Research in Vision and Ophthalmology, Sarasota, May 2–7, 1982; and at the American Intraocular Implant Society, San Francisco, October 30, 1982This investigation was supported in part by the Florida Lions Eye Bank, Miami; the Veterans Administration Medical Center, Miami; Public Health research grant EY02180 from the National Eye Institute; and Research to Prevent Blindness, Inc., New York, New York     

Dense opacification of the optical component of a hydrophilic acrylic intraocular lens: a clinicopathological analysis of 9 explanted lenses

PURPOSE: To report clinical, pathological, histochemical, ultrastructural, and spectrographic analyses of explanted hydrophilic acrylic intraocular lenses (IOLs) obtained from patients who had visual disturbances caused by postoperative opacification of the lens optic. SETTING: Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA, and Ege University, Alsancak Izmir, Turkey. METHODS: Nine hydrophilic IOLs (SC60B-OUV, MDR Inc.) were explanted from 9 patients with decreased visual acuity. Most patients became symptomatic approximately 24 months after uneventful phacoemulsification and IOL implantation. Opacification was noted and appeared clinically to be associated with a fine granularity within the substance of the IOL optic. The IOLs were forwarded to the center and examined by gross and light microscopy. Full-thickness cut sections of the optics were stained with 1% alizarin red and the von Kossa method (special stains for calcium). Some were submitted for scanning electron microscopy and energy dispersive x-ray spectroscopy. RESULTS: Microscopic analyses revealed multiple fine, granular deposits of variable sizes within the lens optics, usually distributed in a line parallel to the anterior and posterior curvatures of the optic, with a clear zone just beneath the optic surface. The deposits stained positive with alizarin red and the von Kossa method. Energy dispersive x-ray spectroscopy of the internal substance of sectioned IOLs demonstrated the presence of calcium within the deposits. CONCLUSION: This is the first clinicopathological report of optic opacification occurring with this hydrophilic acrylic IOL model. Studies of similar cases with this lens should be done to determine the incidence and possible mechanisms of the phenomenon.     

Effect of surgical technique on in vitro posterior capsule opacification

PURPOSE: To compare the effect of different cataract extraction surgical techniques on residual lens epithelial cell (LEC) density and cell regrowth rates using an in vitro model of posterior capsule opacification (PCO). SETTING: Comparative Ophthalmology Research Laboratories, North Carolina State University, Raleigh, North Carolina, USA. METHODS: Lens capsule explants were prepared from freshly enucleated canine globes after extracapsular cataract extraction (ECCE), phacoemulsification, or phacoemulsification followed by capsule vacuuming. Initial cell density on the capsule and cell proliferation were determined by phase contrast microscopy. The effects of the surgical technique on time to confluent growth of the cells across the posterior lens capsule were determined. RESULTS: Residual cell density on the remaining anterior capsule immediately after lens removal was 31.6% +/- 19.3%, 16.1% +/- 8.9%, and 7.7% +/- 5.7% in the ECCE, phacoemulsification, and phacoemulsification/capsule-vacuuming groups, respectively. Time to confluence (range 5.0 to 6.3 days) was not significantly different among the 3 groups when the lens capsules were cultured in serum-supplemented media. The confluence rate was significantly longer (by approximately 5 to 7 days) in the phacoemulsification/capsule-vacuuming group than in the other 2 groups when the capsules were cultured in serum-free media. CONCLUSIONS: Phacoemulsification with and without anterior and equatorial capsular vacuuming led to less initial LEC density in the capsular bag than ECCE. However, because cell proliferation rates among the 3 groups were only marginally affected, near 100% removal of LEC at the time of cataract extraction may be necessary to prevent PCO.     

Study of spatial function using the contrast sensitivity function. Cases of presbyopic subjects fitted with progressive glasses

The spatial properties of the global visual system were measured on the basis of the contrast sensitivity function, in three presbyopic observers. Shape alterations of the contrast sensitivity curves were found depending on the experimental conditions: foveal vision, in far, intermediary and near vision, along central, 13 degrees nasal and 13 degrees temporal meridians (according to three parallels and three meridians), peripheral vision, in far and near vision, at 13 degrees and 26 degrees retinal eccentricities using the central or nasal part of the lens. The central meridian was found to be the most efficient part of the progressive lenses. These results strengthen the observations reported by ophthalmologists and progressive lens wearers.