Stages Of Cataract Research Articles

Real-time intraocular pressure measurement in standard and microcoaxial phacoemulsification

To evaluate intraocular pressure (IOP) in the vitreous cavity during various stages of cataract surgery. University Eye Hospital, Ludwig-Maximilians University, Munich, Germany. In consecutive eyes having combined phacoemulsification, intraocular lens implantation, and pars plana vitrectomy, IOP was monitored in real time through a 25-gauge pars plana cannula connected to an external pressure transducer. Surgery was performed by standard clear corneal phacoemulsification with a 2.5 mm incision and a Mega-Tip (1.26 mm aperture) (Group 1) or by microcoaxial phacoemulsification with a CMP-Tip (0.80 mm aperture) (Group 2). The 2 groups had 5 eyes each. The mean IOP in Group 1 and in Group 2, respectively, was 15.9 mm Hg +/- 9.5 (SD) and 17.0 +/- 13.5 mm Hg preoperatively (P = .442), 40.1 +/- 12.7 mm Hg and 36.5 +/- 17.2 mm Hg during lens removal (P<.001), 17.6 +/- 14.2 mm Hg and 22.6 +/- 8.6 mm Hg during irrigation/aspiration (P<.001), 13.3 +/- 13.2 mm Hg and 16.3 +/- 13.1 mm Hg during IOL implantation (P = .005), and 22.9 +/- 7.0 mm Hg and 21.5 +/- 10.0 mm Hg after IOL implantation through the end of surgery (P = .329). Although the IOP levels were significantly lower than those in previous studies, both phacoemulsification techniques had safe IOP profiles during various steps of surgery. Real-time IOP monitoring may prevent the surgeon from inducing excessive IOP elevation during intraocular manipulation. No author has a financial or proprietary interest in any material or method mentioned.

Potentiation of Intraocular Absorption and Drug Metabolism of N-Acetylcarnosine Lubricant Eye Drops: Drug Interaction with Sight Threatening Lipid Peroxides in the Treatment for Age-Related Eye Diseases

Cataract is the dominant cause of blindness worldwide. Studies of the morphological structure and biophysical changes of the lens in human senile cataracts have demonstrated the disappearance of normal fiber structure in the opaque region of the lens and the disintegration of the lens fiber plasma membrane in the lens tissue. Morphological and biochemical techniques have revealed the regions in human cataractous lenses in which the plasma membrane derangement occurs as the primary light scattering centers which cause the observed lens opacity. Human cataract formation is mostly considered to be a multifactorial disease; however, oxidative stress might be one of the leading causes for both nuclear and cortical cataract. Phospholipid molecules modified with oxygen, accumulating in the lipid bilayer, change its geometry and impair lipid-lipid and protein-lipid interactions in lenticular fiber membranes. Electron microscopy data of human lenses at various stages of age-related cataract document that these disruptions were globules, vacuoles, multilamellar membranes, and clusters of highly undulating membranes. The opaque shades of cortical cataracts represent cohorts of locally affected fibres segregated from unaffected neighbouring fibres by plasma membranes. Other potential scattering centers found throughout the mature cataract nucleus included variations in staining density between adjacent cells, enlarged extracellular spaces between undulating membrane pairs, and protein-like deposits in the extracellular space. These affected parts had membranes with a fine globular aspect and in cross-section proved to be filled with medium to large globular elements. Lipid peroxidation (LPO) is a pathogenetic and causative factor of cataract. Increased concentrations of primary molecular LPO products (diene conjugates, lipid hydroperoxides, fatty acid oxy-derivatives) and end fluorescent LPO products were detected in the lipid moieties of the aqueous humor samples and human lenses obtained from patients with senile and complicated cataracts as compared to normal donors. Utilizing the pharmacokinetic studies and the specific purity N-acetylcarnosine (NAC) ingredient as a source of pharmacological principal L-carnosine, we have created an ophthalmic time-release prodrug form combined with a muco-adhesive lubricant compound carboxymethylcellulose and other essential corneal absorption promoter excipients tailoring the increased intraocular absorption of L-carnosine in the aqueous humor and optimizing its specific effect in producing the basic antioxidant activity in vivo and reducing toxic effects of lipid peroxides to the crystalline lens. L-Carnosine that finds its way into the aqueous humor can accumulate in the lens tissue for a reasonable period of time. However, administration of pure L-carnosine (1% solution) to the rabbit eye (instillation, subconjunctival injection) does not lead to accumulation of this natural compound in the aqueous humor over 30 min in concentration exceeding that in the placebo-treated matched eyes, and its effective concentration is exhausted more rapidly. The NAC prodrug eye drops optimize the clinical effects for the treatment of ophthalmic disorders (such as prevention and reversal of cataracts in human and animal [canine] eyes). The data provided predict a particular NAC ophthalmic prodrug's clinical effect; the suitable magnitude and duration of this effect suggest dose-related bioavailability of L-camosine released from NAC in the aqueous humor of the anterior eye segment. The ophthalmic NAC drug shows promise in the treatment of a range of ophthalmic disorders which have a component of oxidative stress in their genesis (including cataract and after-cataract, glaucoma, dry eye, vitreous floaters, inflammatory disorders, corneal, retinal and systemic diseases [such as diabetes mellitus and its ophthalmic complications]). The clinical efficacy of N-acetylcarnosine lubricant eye drops in ripe cataracts and retinal disorders can be enhanced in combined treatment with a patented oral formulation (Can-C Plus) of non-hydrolyzed carnosine including synergistic compounds (histidine, D-panthethine) with chaperone activity towards lens crystallins and oral supplementation with N-acetylcysteine providing an alternate means of boosting reduced glutathione (GSH) synthesis in the lens.

Ultrasound biomicroscopy of the iridocorneal angle of the eye before and after phacoemulsification and intraocular lens implantation in dogs

To compare the iridocorneal angle (ICA) and angle opening distance (AOD) in dogs with cataractous and noncataractous lenses; evaluate cataractous eyes ultrasono-graphically for association of postoperative ocular hypertension (POH) with the ICA, AOD, and postoperative echogenic anterior chamber debris; and evaluate intraobserver reliability associated with ICA and AOD measurements. 56 dogs with 102 cataracts, and 23 clinically normal dogs. Ultrasound biomicroscopy was performed on 102 eyes of 56 dogs before and after cataract surgery and on 46 nondilated and dilated eyes of 23 clinically normal dogs. Cataract stage, ICA, AOD, and association with POH were assessed. Cataract stage and ICA or AOD were not significantly associated; however, ICA and AOD typically decreased with increasing cataract maturity. Before and after pupillary dilation, AODs were significantly smaller in cataractous eyes than in noncataractous eyes. Before surgery, ICA and AOD in eyes without pupillary dilation were significantly associated with POH. At > 13 degrees , odds of developing POH increased by 11% for each degree increase in the ICA. Postoperative anterior chamber debris was not associated with POH. Coefficient of variation for repeated measurements was 10% for the ICA and 9.5% for the AOD, suggesting good intraobserver reliability. In this study, dogs with larger ICA and AOD measurements before surgery were at greater risk of developing POH. This information may be useful for future studies to determine whether preventative treatment for POH administered prior to surgery may be beneficial.

Prevention of selenite-induced cataractogenesis in Wistar rats by the polyphenol, ellagic acid

The present study sought to evaluate the efficacy of the naturally-occurring polyphenol, ellagic acid, in preventing selenite-induced cataractogenesis. In the present study, Wistar rat pups were divided into 3 groups of 15 each. Group I (normal) rats received an intraperitoneal (i.p.) injection of normal saline on postpartum day 10; group II (cataract-untreated) rats received a single subcutaneous (s.c.) injection of sodium selenite (19μmol/kg body weight) on postpartum day 10; group III (cataract-treated) pups received a single s.c. injection of sodium selenite on postpartum day 10 and intraperitoneal injections of ellagic acid (200mg/kg body weight) on postpartum days 9–14. At the end of the study period (30th postpartum day), slit-lamp examination of both eyes of each rat pup revealed no lenticular opacification (cataract stage 0) in all eyes of group I pups, definite nuclear cataracts (stages 4–6) in the eyes of all (100%) group II rat pups and no lenticular opacification in eight (53%) and mild lenticular opacification (cataract stages 1–3) in seven (47%) of group III rats (changes in group II vs group III, P<0.01). The mean activities of the antioxidant enzymes catalase, glutathione peroxidase, superoxide dismutase and glutathione-S-transferase were significantly lower in lenses of Group II rats than in Group I or Group III rat lenses. In addition, the mean levels of GSH in lenses and erythrocytes were also significantly lower in Group II rats than in Group I or Group III rats. Conversely, the mean concentration of MDA (an indicator of lipid peroxidation) in lenses and erythrocytes was found to be significantly higher in Group II rats than that in Group I or Group III rats. Also, the mean concentration of calcium was found to be significantly higher in lenses of Group II rats than in those of Group I and Group III rats. The results suggest that ellagic acid can prevent or retard experimental selenite-induced cataractogenesis in Wistar rats. This protective effect in rat lenses appears to occur by maintaining the antioxidant defense system and inhibition of lipid peroxidation.

The effects of cataract stage, lens‐induced uveitis and cataract removal on ERG in dogs with cataract

The purpose of this study was to determine the effects of cataract stage, lens-induced uveitis and cataract removal on the electroretinogram (ERG) of dogs with cataract. Fifty-seven dogs diagnosed with unilateral or bilateral cataract whose ERG was recorded at Rakuno Gakuen University Teaching Animal Hospital from 2001 to 2004. Four responses were recorded during the ERG: rod ERG, standard combined ERG, single-flash cone ERG and 30-Hz flicker ERG. Cataracts were divided into four stages: incipient, immature, mature and hypermature, and with or without lens induced uveitis (LIU). Noncataractous eyes of dogs with unilateral cataract were used as the control. We compared ERG amplitude, implicit time, and the b- to a-wave amplitude ratio of cataractous vs. noncataractous eyes, preoperative vs. postoperative cataractous eyes, and cataractous eyes with and without LIU. No significant difference was found in ERG amplitude between incipient, immature and hypermature cataractous eyes, while in mature cataractous eyes decreased amplitude was confirmed in all responses compared with control eyes. However, no significant difference in b/a ratio was found at any stage of cataract. In postoperative eyes, increased amplitude was recorded in all responses compared to preoperative values. In eyes with LIU a decreased amplitude in the rod ERG and b-wave of standard combined ERG was recorded and, furthermore, a significant decline was confirmed in b/a ratio. ERG values were influenced by cataract stage and LIU. LIU was associated with a reduction in the b/a ratio.

Histological examination of primary posterior capsule plaques

To understand the source and evolution of the cellular elements of posterior capsule plaques. Department of Ophthalmology, University of Sciences, Faculty of Medicine, Pécs, Hungary. In 24 eyes of 24 patients, the primary fibrotic plaques were carefully peeled off the posterior capsule with forceps and sent for histological examination. The samples were stained with hematoxylin-eosin and with picrosirius to demonstrate collagen content. Most plaques were found in elderly patients with mature cataracts. However, one was found in a patient with congenital cataract. The histological examination revealed different stages of plaques, permitting discrimination of early (cellular), transitional, and late (fibrotic) stages. The plaques in the early stage contained cuboidal cells with nuclei; collagen deposition led to the development of the transitional stage; and further collagen deposition led to the fibrotic stage. There was no significant correlation between the maturity of the cataract and the plaque stage, but other factors such as previous eye surgery (vitrectomy, glaucoma surgery), long-standing diabetes mellitus (DM), and a high degree of myopia appeared to contribute to the development of plaques. Primary posterior capsule plaques were found primarily in elderly patients with mature cataracts but were also present post vitrectomy in those who had DM from a young age and had early stages of cataract. In the early plaque stage, cells with nuclei were found. It follows that plaques are capable of proliferation at this stage, aggravating visual disturbance. Therefore, removing the plaques by peeling from the posterior capsule or by posterior capsulorhexis during surgery is suggested.

Posterior capsular opacification in diabetic and nondiabetic canine patients following cataract surgery

Posterior capsular opacification (PCO) is the most common postoperative complication of contemporary cataract surgery. Limited information is available regarding PCO formation and factors that influence PCO development in the dog. Two hundred sixty-five eyes (144 from diabetic dogs and 121 from dogs with breed-related cataracts) were prospectively evaluated for PCO formation for up to 12 months postoperatively. The mean age of all dogs in the study was 7.77 years and diabetic dogs were significantly older than dogs with breed-related cataracts. There were 73 males (61 neutered, 12 intact) and 74 females (70 neutered, 4 intact) in the study. Statistical analysis was performed based on age, breed/size, gender, stage of cataract at the time of surgery, PCO score at each time point, breed-related vs. diabetic cataract, right eyes compared to left eyes, and presence/absence of uveitis. Age and gender did not significantly influence PCO formation. Small and medium-sized breeds developed significantly more PCO in comparison to the large/giant breeds at 2 weeks and 2-4 months postoperatively, but the differences were not significant at later time points. There was an overall significant increase in PCO formation in eyes with early immature cataracts when compared to other stages of cataract up to 4 months postoperatively but not at later time points. There were no statistical differences in PCO score at 6 months or at 1 year postoperatively in eyes with breed-related and diabetic cataracts. Right eyes did not differ from left eyes in PCO score. PCO score significantly increased over time in breed-related and diabetic groups and in the overall population. No difference was found in the degree of PCO formation in eyes with inflammation prior to or after surgery compared with those without inflammation. In summary, age, gender, presence of inflammation, and cause of cataract (breed-related vs. diabetes mellitus) do not influence the development of PCO in canine cataract dogs. Small and medium-sized breeds develop significant PCO earlier than larger breeds. It is important to note that all eyes from all dogs in this study developed PCO in a time dependent manner.

Clinical features and outcomes of phacoemulsification in 39 horses: a retrospective study (1993–2003)

To identify visual outcome and postoperative complications following phacoemulsification of equine cataracts. Records of 39 horses (55 eyes) with cataracts were reviewed. Eyes with cataracts removed by phacoemulsification were included in the study. Data collected included age, breed, sex, stage and etiology of cataract, unilateral vs. bilateral involvement, and ultrasound findings. Horses were grouped by etiology of the cataract. Visual outcome and complications were evaluated for each group and the overall population. Immediately postoperatively 46 out of 47 eyes (98%) were sighted. Four weeks postoperatively 23 of 29 operated eyes (79%) were sighted [13/18 (72%) eyes with congenital/juvenile onset, 6/6 (100%) eyes with traumatic and 4/5 (90%) eyes with uveitis-induced cataracts], with 18 eyes lost to follow-up. The most common postoperative complications included corneal edema (19 eyes/40%), fibrin in the anterior chamber (11 eyes/23%), postoperative ocular hypertension (9 eyes/19%), synechia/dyscoria (9 eyes/19%), and hyphema (7 eyes/15%). Prognosis for vision is favorable for horses following phacoemulsification and planned posterior continuous tear circular capsulorrhexis. Success rates depend on age of patient, cause of cataract and pre-existing intraocular disease. The highest success rate occurred in eyes with traumatic cataracts.

Biochemical changes in selenite cataract model measured by high‐resolution MAS 1H NMR spectroscopy

To correlate certain levels of lens opacification with high-resolution magic-angle spinning proton nuclear magnetic resonance (HR-MAS (1)H NMR) spectroscopy analysis of the biochemical changes in rat lenses in a selenite cataract model. Selenite cataract was induced by injecting 13-day-old Sprague-Dawley rat pups with a single subcutaneous dose of sodium selenite (3.28 mg/kg in 0.9% sodium chloride solution). Lens opacification was observed using a photographic slit-lamp microscope at selected time-points 3, 6 and 9 days after selenite injection and was then graded (levels 0, 1 and 2). The animals were killed after the slit-lamp microscopy, lenses were removed and HR-MAS (1)H NMR spectra from intact lenses were obtained. Relative changes in metabolite concentrations were determined after comparison with matched lenses from untreated animals. Photographic slit-lamp microscopy revealed different stages of cataract in all animals treated with selenite. In the high quality HR-MAS (1)H NMR spectra of the lenses, more than 30 different metabolites were identified in each lens. With the exception of taurine, the concentrations of all amino acids showed a significant increase (p < 0.05) in the second level of cataract. By contrast, glutathione (GSH), succinate and phosphocholine concentrations were significantly reduced. For the first time, this study demonstrates the potential to correlate the level of lens opacification with the biochemical changes obtained with HR-MAS (1)H NMR spectroscopy analysis in a selenite cataract model.

Ingestion of IH636 grape seed proanthocyanidin extract to prevent selenite-induced oxidative stress in experimental cataract

To investigate whether dietary supplementation with IH636 grape seed proanthocyanidin extract (GSPE) prevents selenite-induced cataract. Department of Ophthalmology, Gulhane Military Medical Academy, Ankara, Turkey. Thirty Spraque-Dawley rat litters were put randomly into 3 groups. In group 1 (n = 10), sodium selenite (30 nmol/g body weight) was injected subcutaneously on postpartum day 10. In group 2 (n = 10), sodium selenite (30 nmol/g body weight) was injected on postpartum day 10 and oral GSPE (100 mg/kg body weight) was given for 1 week after sodium selenite injection. Only subcutaneous saline was injected in group 3 (control, n = 10). The development of cataract was assessed for 3 weeks, and its density was graded and photographed with a slitlamp. Removed rat lenses were analyzed for glutathione (GSH) and malondialdehyde (MDA). All of the rats in group 1 had cataract between stage 6 and stage 3. In group 2, only 5 of 10 eyes had cataract between stage 3 and stage 2 and no cataract occurred in the remaining 5 rats. The difference between mean cataract stages in group 1 and group 2 was significant (P<.05). The mean GSH level in group 1 was significantly lower than in group 2 and controls (P<.05). The mean MDA level in group 1 was significantly higher than in group 2 and controls (P<.05). IH636 grape seed proanthocyanidin extract effectively suppressed cataract formation in rats. Routine consumption of grape seed proanthocyanidin extract in the form of food or dietary supplement may offer a prophylactic measure against onset and progression of cataract.

Evaluation of client perceptions concerning outcome of cataract surgery in dogs

To compare client perception of outcome of phacoemulsification in dogs with information obtained from medical records. Retrospective cohort study. 108 dogs (203 eyes) undergoing phacoemulsification from May 1999 through April 2004. Data obtained from medical records included signalment, presence of diabetes mellitus, cataract stage, whether surgery was unilateral or bilateral, intraocular lens (IOL) placement, and postoperative complications. Owners completed a survey concerning outcome of phacoemulsification in their dog. Survey responses from owners classified as satisfied or dissatisfied with the outcome of phacoemulsification on the basis of their willingness, in retrospect, to have the surgery performed again were compared. Data from medical records and survey responses were available for 108 dogs (203 eyes). Median follow-up was 3 months via medical record review and 12 months via owner survey responses. Most (81%) owners were satisfied with outcome. The most common reason for dissatisfaction was loss of vision after surgery; however, most dissatisfied owners did not return their dog for examinations. Owner perception of success was not associated with patient age, sex, presence of diabetes mellitus, cataract stage, or IOL placement in at least 1 eye but was associated with perceived improvement of their pet's vision and activity level. Dissatisfied owners were significantly more likely to report that explanation of risks and complications before surgery was inadequate. Owner perception of outcome after phacoemulsification in dogs was highly favorable. However, surgical risks and the importance of postoperative examinations, particularly in dogs undergoing visual deterioration, must be conveyed to clients.

Presbyopia: The First Stage of Nuclear Cataract?

Presbyopia, the inability to accommodate, affects almost everyone at middle age. Recently, it has been shown that there is a massive increase in the stiffness<footref rid="foot01">¹</footref> of the lens with age and, since the shape of the lens must change during accommodation, this could provide an explanation for presbyopia. In this review, we propose that presbyopia may be the earliest observable symptom of age-related nuclear (ARN) cataract. ARN cataract is a major cause of world blindness. The genesis of ARN cataract can be traced to the onset of a barrier within the lens at middle age. This barrier restricts the ability of small molecules, such as antioxidants, to penetrate into the centre of the lens leaving the proteins in this region susceptible to oxidation and post-translational modification. Major protein oxidation and colouration are the hallmarks of ARN cataract. We postulate that the onset of the barrier, and the hardening of the nucleus, are intimately linked. Specifically, we propose that progressive age-dependent hardening of the lens nucleus may be responsible for both presbyopia and ARN cataract.

Revival of the Lens Transparency with N-Acetylcarnosine

The risk, cost and social requirement factors drive the investigation of pharmaceutical approaches to the management of cataracts. The role of free-radical-induced lipid oxidation (LPO) in the development of cataracts has been identified. Initial stages of cataract are characterized by the accumulation of primary (diene conjugates, cetodienes) LPO products,while in later stages there is a prevalence of LPO fluorescent end products. Reliable increase in oxiproducts of fatty acyl content of lenticular lipids was shown by a direct gas chromatography technique producing fatty acid fluorine- substituted derivatives. The lens opacity degree correlates with the level of the LPO fluorescent end product accumulation in its tissue, accompanied by SH group oxidation of lens proteins due to a decrease of reduced glutathione concentration in the lens. The injection of LPO products into the vitreous was shown to induce cataract. Peroxide damage of the lens fiber membranes may be the initial cause of cataract formation. The authors developed N-Acetylcarnosine ophthalmic drug with lubricant carboxymethylcellulose in eye drops (NAC, Can-C TM , Nu-Eyes TM ) suitable for the non-surgical prevention and treatment of age-related cataracts. The NAC ophthalmic drug protects the crystalline lens from oxidative stress-induced damages and in a recent clinical trial it was shown to produce an effective, safe and long-term improvement in sight. When administered topically to the eye, NAC drug functions as a time-release prodrug form of L- carnosine resistant to hydrolysis with carnosinase and significantly increases the intraocular uptake of L-carnosine in the aqueous humor. The mechanisms of prevention and reversal of cataracts with NAC ophthalmic drug are considered which include prevention by the intraocular released carnosine of free-radical-induced inactivation of proprietary lens antioxidant enzymes (superoxide dismutase), prevention of carbohydrate and metal-catalysed autooxidation of ascorbic acid -induced cross-linking glycation reactions to the lens proteins, universal antioxidant and scavenging activity towards lipid hydroperoxides, aldehydes and oxygen radicals, activation with L-carnosine ingredient of proteasome activity in the lens. In this study the clinical effects of a topical solution of NAC ophthalmic drug on lens opacities were examined in patients with cataracts and canines with age-related cataracts. The positive effect on lens clarity and clarifying modification of opacification zones is demonstrated. The data suggest a potential and show the efficacy of developed NAC ophthalmic drug for a positive effect of treatment (both reversal and prevention) of age-related cataracts. Innovative Vision Products, Inc. is a holder of the worldwide patent (including PCT International Publication Number WO 2004/028536 A1) for the application of N-acetylcarnosine for the treatment of ophthalmic disorders including cataracts.

Temporal relationship between lens protein oxidation and cataract development in streptozotocin-induced diabetic rats

We compared the progression of lens opacification with the time course of oxidation of lens proteins under conditions of streptozotocin-induced experimental diabetes in rats. By the end of the 17th week, approx. 50% of the diabetic animals developed mature cataracts. During the following month, 95% of the eyes in the diabetic group became cataractous. In the course of lens opacification we observed a time-dependent increase in the content of protein carbonyls and decrease in the concentration of protein sulfhydryls in the lenses of diabetic animals. Significantly higher protein carbonyl (p<0.01) and lower protein sulfhydryl (p<0.001) content was found in lenses with the advanced stage of cataract when compared with the diabetic lenses still transparent. We showed that the values of protein carbonyls exceeding 1.2 nmol/mg protein and of sulfhydryls falling below 60 nmol/mg protein corresponded to an approximately 50% incidence of mature cataract development. At the end of the 34th week, when all lenses of diabetic rats became cataractous, the corresponding values of protein carbonyls and sulfhydryls were 2.5 nmol/mg protein and 27 nmol/mg protein, respectively. The main finding of this study is the disclosure of quantitative relationship between the degree of protein oxidation and the rate of advanced cataract development in the widely used model of streptozotocin-induced experimental diabetes in rats.

Modificación de la flora conjuntival por el empleo de soluciones de higiene palpebral

The aim of the present study is to evaluate the effectiveness of a solution of palpebral hygiene during the preoperative stage of cataract surgery. We studied 286 patients divided in 5 groups. One control group that did not use the product, and the remaining 4, that used the product during 3, 4, 5 and 6 days. The design of the study was prospective, randomize and masked. We took a sample of the conjunctival fundus in the morning of the day of the surgery, before commencing treatment with eye drops. This sample was sown according to microbiological techniques and analyzed by the microbiology department. The best time for using palpebral hygiene solutions prior to cataract surgery is four to five days. If it is used at less than three days, it does not decrease the rate of positive cultures and if the solution is applied more than six days, microorganisms that are not part of the common conjunctival flora may appear. Palpebral hygiene products should not be used more than five consecutive days previous to surgery.

Modeling utility of second-eye cataract surgery.

To study the impact on public health in terms of utility of various proportions of first-eye and second-eye cataract surgery. A model was used to study the impact on a population of a fixed cataract surgical rate (9,250 operations/1,000,000 people) with varying proportions of first-eye and second-eye cataract operations. The study population was the County of Blekinge with a known incidence of previous cataract surgery. The prevalence of cataract, the estimated need for cataract surgery, and the utility values were taken from the literature. The population was grouped by disability stage of cataract and previous cataract surgery in accordance with prevalence studies and data from a large national database on cataract surgery and patients' self-assessed visual function. The mortality rate was taken from real data for the study population. Given a fixed cataract surgical rate over a period of five years, a high percentage of second-eye cataract surgery (42 percent) resulted in a mean utility of 0.82239 in the population forty years of age and older and the corresponding number for a low percentage of second-eye cataract surgery (25 percent) was 0.82253. A high percentage of second-eye surgeries resulted in 421 more individuals who were well compared with a low percentage of second-eye surgeries. On the other hand, a low percentage of second-eye surgeries resulted in 152 fewer individuals with disability and 118 fewer individuals with dependence compared with a high percentage of second-eye surgeries. A high frequency of first-eye cataract surgeries instead of second-eye surgeries affects more individuals and means an optimized improvement of utility in a population. This should be recommended if the cataract surgical rate is very insufficient. If the cataract surgical rate is high, more second-eye surgeries should be performed to optimize quality of life to as many as possible.

Cataract prevalence, cataract surgical coverage and its contribution to the reduction of visual disability in Oman

aim To estimate the magnitude and determinants of cataract prevalence and cataract surgical coverage and to evaluate their role in visual disability in Oman.methods A cross-sectional study was conducted on 11,413 subjects in Oman in 1997. The presence and stage of cataract was noted on the basis of the history and an examination. The patient's phakic, pseudophakic or aphakic status and visual status were determined. The prevalence of cataract and the cataract surgical coverage were estimated. A causal relation was assumed between a backlog of cataract and age, gender and area of residence. The Attributable Risk (AR) and Population Attributable Risk (PAR) for these factors were estimated.results The prevalence of cataract was 29.3/1000 (95% CI: 27.76 to 30.84). This was 4.97/1000 (95% CI: 3.68 to 6.26) for blinding cataract (vision <3/60). The cataract surgery services covered 70.18% (95% CI: 69.52 to 70.84) of the blinding cataracts and 28.76% (95% CI: 28.11 to 29.41) of all cataracts. The AR and PAR of female gender in the cataract backlog were 35.5% and 1.06%, respectively. The AR and PAR of the residents of ‘Group B’ regions were 40.5% and 1.26%, respectively. The AR and PAR of subjects ‘less than 60 years old’ were 55.6% and 1.66%, respectively. If the gaps in cataract surgery due to gender, regions and age groups were to be filled, the prevalence of cataract could be reduced by 1.06%, 1.21% and 1.66%, respectively.conclusion The health program should identify and address the barriers to cataract surgery among identified high-risk groups.

Eye Cataract Simulation Using Polymer Dispersed Liquid Crystal Scattering Obstacles

Polymer dispersed liquid crystals with electrically induced variations of light scattering extent similar to that of transparent PLZT ceramics are used for simulation of different development stages of eye cataract. Wavelength dependencies of scattering are determined in the visible spectral range, and human visual response looking through the scattering obstacle to the onset of various spatial frequency stimuli is determined psychophysically and electrophysiologically in order to find correlation between the scattering extent, visual acuity and visual evoked potential VEP chromatic characteristics.

Phacoemulsification for Anisometropia Associated with Presenile Cataracts in Patients with High Myopia

The conventional treatment for anisometropia brought on by asymmetric cataracts in presenile patients with high myopia is still controversial. In this report, we evaluate treatment results by chart review. We reviewed the records of four patients under the age of 55 with high myopia and anisometropia associated with asymmetric lens opacity between fellow eyes. A four-step procedure was followed to confirm anisometropia induced by different degrees of lens opacity between the eyes. The eye with poorer best-corrected visual acuity (BCVA) in each patient underwent phacoemulsification with implantation of an intraocular lens. Different methods were used for vision correction in the fellow eyes, depending on the patient's lifestyle. All eyes that underwent cataract surgery achieved a BCVA of at least 6/6. Contact lenses were fitted in the fellow eyes of two patients and laser in situ keratomileusis (LASIK) was performed in the other two patients. Except for one of the eyes that underwent LASIK, each of the fellow eyes had satisfactory vision after correction. Improved postoperative visual acuity was obtained in myopic eyes with presenile cataracts. LASIK may not be suitable for correcting refractive errors in fellow high myopic eyes in the early stages of cataracts.

Lipid peroxidation and cataracts: N-acetylcarnosine as a therapeutic tool to manage age-related cataracts in human and in canine eyes.

Cataract formation represents a serious problem in the elderly, with approximately 25% of the population aged >65 years and about 50% aged >80 years experiencing a serious loss of vision as a result of this condition. Not only do cataracts diminish quality of life, they also impose a severe strain on global healthcare budgets. In the US, 43% of all visits to ophthalmologists by Medicare patients are associated with cataract. Surgery represents the standard treatment of this condition, and 1.35 million cataract operations are performed annually in the US, costing 3.5 billion US dollars (year of costing, 1998). Unfortunately, the costs of surgical treatment and the fact that the number of patients exceeds surgical capacities result in many patients being blinded by cataracts worldwide. This situation is particularly serious in developing countries; worldwide 17 million people are blind because of cataract formation, and the problem will grow in parallel with aging of the population. In any event, surgical removal of cataracts may not represent the optimal solution. Although generally recognised as being one of the safest operations, there is a significant complication rate associated with this surgical procedure. Opacification of the posterior lens capsule occurs in 30-50% of patients within 2 years of cataract removal and requires laser treatment, a further 0.8% experience retinal detachments, approximately 1% are rehospitalised for corneal problems, and about 0.1% develop endophthalmitis. Although the risks are small, the large number of procedures performed means that 26,000 individuals develop serious complications as a result of cataract surgery annually in the US alone. Thus, risk and cost factors drive the investigation of pharmaceutical approaches to the maintenance of lens transparency. The role of free radical-induced lipid oxidation in the development of cataracts has been identified. Initial stages of cataract are characterised by the accumulation of primary (diene conjugates, cetodienes) lipid peroxidation (LPO) products, while in later stages there is a prevalence of LPO fluorescent end-products. A reliable increase in oxiproducts of fatty acyl content of lenticular lipids was shown by a direct gas chromatography technique producing fatty acid fluorine-substituted derivatives. The lens opacity degree correlates with the level of the LPO fluorescent end-product accumulation in its tissue, accompanied by sulfhydryl group oxidation of lens proteins due to a decrease of reduced glutathione concentration in the lens. The injection of LPO products into the vitreous has been shown to induce cataract. It is concluded that peroxide damage of the lens fibre membranes may be the initial cause of cataract development. N-acetylcarnosine (as the ophthalmic drug Can-C), has been found to be suitable for the nonsurgical prevention and treatment of age-related cataracts. This molecule protects the crystalline lens from oxidative stress-induced damage, and in a recent clinical trial it was shown to produce an effective, safe and long-term improvement in sight. When administered topically to the eye in the form of Can-C, N-acetylcarnosine functions as a time-release prodrug form of L-carnosine resistant to hydrolysis with carnosinase. N-acetylcarnosine has potential as an in vivo universal antioxidant because of its ability to protect against oxidative stress in the lipid phase of biological cellular membranes and in the aqueous environment by a gradual intraocular turnover into L-carnosine. In our study the clinical effects of a topical solution of N-acetylcarnosine (Can-C) on lens opacities were examined in patients with cataracts and in canines with age-related cataracts. These data showed that N-acetylcarnosine is effective in the management of age-related cataract reversal and prevention both in human and in canine eyes.