LOCS III versus the Oxford Clinical Cataract Classification and Grading System for the assessment of nuclear, cortical and posterior subcapsular cataract

Innovative utilization of ultra-wide field fundus images and deep learning algorithms for screening high-risk posterior polar cataract

PURPOSE

To test a cataract shadow projection theory and validate it by developing a deep learning algorithm that enables automatic and stable posterior polar cataract (PPC) screening using fundus images.

SETTING

Department of Ophthalmology, Far Eastern Memorial Hospital, New Taipei, Taiwan.

DESIGN

Retrospective chart review.

METHODS

A deep learning algorithm to automatically detect PPC was developed based on the cataract shadow projection theory. Retrospective data (n = 546) with ultra-wide field fundus images were collected, and various model architectures and fields of view were tested for optimization.

RESULTS

The final model achieved 80% overall accuracy, with 88.2% sensitivity and 93.4% specificity in PPC screening on a clinical validation dataset (n = 103).

CONCLUSIONS

This study established a significant relationship between PPC and the projected shadow, which may help surgeons to identify potential PPC risks preoperatively and reduce the incidence of posterior capsular rupture during cataract surgery.

Cataract Classification Systems: A Review

Cataract is among the leading causes of visual impairment worldwide. Innovations in treatment have drastically improved patient outcomes, but to be properly implemented, it is necessary to have the right diagnostic tools. This review explores the cataract grading systems developed by researchers in recent decades and provides insight into both merits and limitations. To this day, the gold standard for cataract classification is the Lens Opacity Classification System III. Different cataract features are graded according to standard photographs during slit lamp examination. Although widely used in research, its clinical application is rare, and it is limited by its subjective nature. Meanwhile, recent advancements in imaging technology, notably Scheimpflug imaging and optical coherence tomography, have opened the possibility of objective assessment of lens structure. With the use of automatic lens anatomy detection software, researchers demonstrated a good correlation to functional and surgical metrics such as visual acuity, phacoemulsification energy, and surgical time. The development of deep learning networks has further increased the capability of these grading systems by improving interpretability and increasing robustness when applied to norm-deviating cases. These classification systems, which can be used for both screening and preoperative diagnostics, are of value for targeted prospective studies, but still require implementation and validation in everyday clinical practice.

Anterior Segment Biometry in Primary Angle Closure Glaucoma Patients with Visual Field Progression: Comparison between Malays and Chinese

Objective

To compare anterior segment biometry parameters in progress and non-progress primary angle closure glaucoma (PACG) among Malay and Chinese patients.

Materials and methods

A cross-sectional study was conducted between November 2015 and December 2016 involving 75 patients with PACG (43 Malays and 32 Chinese) who were recruited from a single glaucoma center in Malaysia. Ocular examination included anterior segment biometry measurements on the selected eye. Axial length (AL) and anterior chamber depth (ACD) measurement was done using a noncontact partial coherence interferometer (IOL Master, Carl Zeiss, Germany). Anterior chamber angle (ACA) was measured by Anterior Segment-OCT (Spectralis Heidelberg, Germany). Humphrey visual field (HVF) 24-2 analysis of the same eye was conducted and compared with the HVF when diagnosis was made. Progression of PACG patients was assessed according to the Hodapp, Parrish and Anderson's (HPA) classification, they were then divided into progress and non-progress groups. Comparison of anterior segment biometry parameters between Malay and Chinese PACG patients with and without progression was analyzed using independent T test. Multivariate ANOVA analysis was used to compare the anterior segment parameters between progress and non-progress PACG patients, with adjustment for age, gender, lens status, family history and presence of diabetes mellitus.

Results

Chinese PACG patients have significant shorter AL (22.18 mm ± 0.76) and narrower ACA (11.96° ± 6.00) compared to Malay PACG patients. Among the progress group, Chinese PACG patients have significant shorter AL, shallower ACD and narrower ACA compared to Malays. However, after controlling for confounding factors, there was significant difference in ACA between Malay and Chinese PACG. There was also no significant difference of ocular biometry measurement between Chinese and Malay patients in progress and non-progress group.

Conclusion

There was racial influence in ocular biometry measurement in PACG patients. Chinese have significant narrower ACA compared to Malays. Serial AS-OCT monitoring is important in management of PACG.

How to cite this article

Neoh FP, Azhany Y, Siti-Azrin AH, et al. Anterior Segment Biometry in Primary Angle Closure Glaucoma Patients with Visual Field Progression: Comparison between Malays and Chinese. J Curr Glaucoma Pract 2023;17(1):3-8.

Deep Learning-Based Cataract Detection and Grading from Slit-Lamp and Retro-Illumination Photographs

Purpose

To develop and validate an automated deep learning (DL)-based artificial intelligence (AI) platform for diagnosing and grading cataracts using slit-lamp and retroillumination lens photographs based on the Lens Opacities Classification System (LOCS) III.

Design

Cross-sectional study in which a convolutional neural network was trained and tested using photographs of slit-lamp and retroillumination lens photographs.

Participants

One thousand three hundred thirty-five slit-lamp images and 637 retroillumination lens images from 596 patients.

Methods

Slit-lamp and retroillumination lens photographs were graded by 2 trained graders using LOCS III. Image datasets were labeled and divided into training, validation, and test datasets. We trained and validated AI platforms with 4 key strategies in the AI domain: (1) region detection network for redundant information inside data, (2) data augmentation and transfer learning for the small dataset size problem, (3) generalized cross-entropy loss for dataset bias, and (4) class balanced loss for class imbalance problems. The performance of the AI platform was reinforced with an ensemble of 3 AI algorithms: ResNet18, WideResNet50-2, and ResNext50.

Main Outcome Measures

Diagnostic and LOCS III-based grading prediction performance of AI platforms.

Results

The AI platform showed robust diagnostic performance (area under the receiver operating characteristic curve [AUC], 0.9992 [95% confidence interval (CI), 0.9986–0.9998] and 0.9994 [95% CI, 0.9989–0.9998]; accuracy, 98.82% [95% CI, 97.7%–99.9%] and 98.51% [95% CI, 97.4%–99.6%]) and LOCS III-based grading prediction performance (AUC, 0.9567 [95% CI, 0.9501–0.9633] and 0.9650 [95% CI, 0.9509–0.9792]; accuracy, 91.22% [95% CI, 89.4%–93.0%] and 90.26% [95% CI, 88.6%–91.9%]) for nuclear opalescence (NO) and nuclear color (NC) using slit-lamp photographs, respectively. For cortical opacity (CO) and posterior subcapsular opacity (PSC), the system achieved high diagnostic performance (AUC, 0.9680 [95% CI, 0.9579–0.9781] and 0.9465 [95% CI, 0.9348–0.9582]; accuracy, 96.21% [95% CI, 94.4%–98.0%] and 92.17% [95% CI, 88.6%–95.8%]) and good LOCS III-based grading prediction performance (AUC, 0.9044 [95% CI, 0.8958–0.9129] and 0.9174 [95% CI, 0.9055–0.9295]; accuracy, 91.33% [95% CI, 89.7%–93.0%] and 87.89% [95% CI, 85.6%–90.2%]) using retroillumination images.

Conclusions

Our DL-based AI platform successfully yielded accurate and precise detection and grading of NO and NC in 7-level classification and CO and PSC in 6-level classification, overcoming the limitations of medical databases such as few training data or biased label distribution.

Phakic intraocular lenses: An overview

Phakic intraocular lenses (pIOLs) are a common solution for the surgical correction of high myopia and myopia in thin corneas. Global trends result in increasing rates of patients with high myopia which will result in increased rates of pIOL implantation. Three types of lenses can be distinguished: anterior chamber angle-supported, anterior chamber iris-fixated, and posterior chamber phakic IOLs. The efficacy of phakic intraocular lenses is generally very good, but pIOLs have undergone many changes over the years to improve the safety profile and decrease pIOL-related complications such as endothelial cell loss, corneal decompensation and cataract formation. This article describes the efficacy and safety profiles of the most recent pIOLs, as well as suggests gaps of knowledge that are deserve additional research to optimize the results of pIOLs.

Effect of high-vacuum setting on phacoemulsification efficiency

PURPOSE

To evaluate the effect of a high-vacuum setting versus a low-vacuum setting on the efficiency of phacoemulsification.

SETTING

Sunderland Eye Infirmary, Sunderland, United Kingdom.

DESIGN

Prospective clinical trial.

METHODS

Consecutive patients having cataract surgery in 2014 were recruited. Cataract surgery was performed by 2 experienced surgeons using a phacoemulsification machine with monitored forced infusion. The cataractous lens was split into 2 heminuclei using the stop-and-chop technique; in 1 heminucleus, phacoemulsification and aspiration used a high-vacuum setting (600 mm Hg; treatment group) and in the other heminucleus, a low-vacuum setting (350 mm Hg; control group). The high and low settings were alternated by case per the operating list to reduce surgeon bias. The main outcome measures were cumulative dissipated energy (CDE) and active heminucleus removal time.

RESULTS

One hundred sixty patients (160 eyes) were enrolled in the study, and 158 were included in the analysis. The CDE per heminucleus was significantly lower with the high-vacuum setting than with the low-vacuum setting (mean 2.81 percent-seconds; 95% confidence interval (CI), 2.44-3.21 versus 3.81 percent-seconds; 95% CI, 3.38-4.20; P < .001). The active heminucleus removal time was significantly shorter in the high-vacuum group than the low-vacuum group (mean 27.77 seconds; 95% CI, 25.26-30.19 versus 33.59 seconds; 95% CI, 31.07-35.92; P < .001). The observed differences were independent of the surgeon, patient age and sex, incision size, and nucleus density. No intraoperative complications were observed in either group.

CONCLUSION

A high-vacuum setting improved phacoemulsification efficiency using an active fluidics system and torsional phacoemulsification.

Cataract frequency and subtypes involved in workers assessed for their solar radiation exposure: a systematic review

Cataract is currently the primary cause of blindness worldwide, and one of its main risk factors is solar ultraviolet radiation exposure. According to the localization of lens opacities, three main subtypes of cataract are recognized: nuclear, cortical and posterior subcapsular cataract. One of the main determinants of individual long-term solar radiation exposure is outdoor work. We systematically reviewed scientific literature from the last 20 years to update the recent development of research on the risk of cataract in outdoor workers and on the specific subtypes involved, also investigating the methods applied to evaluate the occupational risk. A total of 15 studies were included in the review, of which 12 showed a positive association. The studies confirm the relationship of long-term occupational solar radiation exposure with cortical cataract and give new support for nuclear cataract, although no substantial new data were available to support a relation with the posterior subcapsular subtype. In most of the studies, the exposure assessment was not adequate to support a representative evaluation of the ocular risk; however, outdoor work is clearly a relevant risk factor for cataract. Further research providing a better evaluation of the relation between solar radiation exposure levels and lens damage in workers is needed and aimed to establish adequate occupational exposure limits and better preventive measures, studying also their effectiveness.

Solar Radiation Exposure and Outdoor Work: An Underestimated Occupational Risk

A considerably high number of outdoor workers worldwide are constantly exposed for the majority of their working life to solar radiation (SR); this exposure is known to induce various adverse health effects, mainly related to its ultraviolet (UV) component. The skin and the eye are the principal target organs for both acute and long-term exposure. Actinic keratosis, non-melanoma skin cancers, and malignant melanoma are the main long-term adverse skin effects, whereas in the eye pterygium, cataracts, and according to an increasing body of evidence, macular degeneration may be induced. Despite this, SR exposure risk is currently undervalued, if not neglected, as an occupational risk factor for outdoor workers. SR exposure is influenced by various environmental and individual factors, and occupation is one of the most relevant. For a better understanding of this risk and for the development of more effective prevention strategies, one of the main problems is the lack of available and adequate methods to estimate SR worker exposure, especially long-term exposure. The main aims of this review were to provide a comprehensive overview of SR exposure risk of outdoor workers, including the UV exposure levels and the main methods recently proposed for short-term and cumulative exposure, and to provide an update of knowledge on the main adverse eye and skin effects. Finally, we also outline here preventive interventions to reduce occupational risk.

Methodology of the ZOC-BHVI High Myopia Cohort Study: The Onset and Progression of Myopic Pathologies and Associated Risk Factors in Highly Myopic Chinese

PURPOSE

The increasing prevalence of high myopia and its associated pathologies has raised challenges to ophthalmic services. This project aims to explore the onset and progression of myopic pathologies in highly myopic eyes through a prospective research cohort established in South China.

METHODS

Patients with high myopia (sphere ≤ -6.00 D) visiting the optometric clinic of Zhongshan Ophthalmic Center (ZOC) were invited to participate in the baseline examinations and follow-up visit over a 10-year period. People having secondary myopia, history of any refractive surgery, significant ocular media opacity, or other severe health problems were excluded. The measurements included visual acuity, ocular biometry, visual function, cycloplegic refraction, fundus imaging, ocular shape by MRI, blood tests and questionnaires.

RESULTS

A total of 890 participants completed the baseline examinations, with a mean age at baseline of 22.7 ± 12.4 years. The mean spherical equivalent at baseline was 10.13 ± 3.65 D, and the mean axial length (AL) was 27.52 ± 1.63 mm. The older subjects tended to have more severe myopia and longer ALs.

CONCLUSION

The study will provide new knowledge on the relationship between high myopia and pathological changes such as myopic macular degeneration and staphyloma.

[Phacoemulsification versus manual small incision cataract surgery: Anatomic and functional results]

PURPOSE

Prospective randomised study to compare the impact of phacoemusification (PHACO) and small incision cataract surgery (SICS) on endothelial structure (cell density and morphology) and refractive results (visual acuity, induced astigmatism).

METHODS

Prospective study of 57 patients (63 eyes) over 20 months (May 2012-January 2014) undergoing surgery by 2 experienced surgeons. We included patients with senile or presenile cataracts, LOCS III class 2, 3 and 4. Patients were randomized into 2 groups based on their birth month (group 1: PHACO [33]; group 2: SICS [30]). All pre- intra- and postoperative data were collected prospectively. The minimum follow-up was 6 months. We used the SPSS 18.0 for statistical analysis. Statistical tests used included the test-t Student, the Anova test, the Mann-Witney non-parametric test and the Khi² test. A threshold of significance was set at 0.05.

RESULTS

The mean preoperative endothelial cell density was 2447.5±225 c/mm² with no significant difference between the two groups (P=0.207). The mean percentage of hexagonality was 55.5±8.2% in groups 1 and 2. The most significant cell loss was during the first immediate postoperative period for both groups. At Day 15 postoperative, the decrease in cell loss was significant (P<0.001) with a mean loss of 312.9±208.9 c/mm² (P<10^-2). Postoperatively, the mean best-corrected visual acuity was 0.057 log MAR for all of our patients (P=0.170); no patient had an acuity ≤1/10. The mean astigmatism at the conclusion of follow-up was 1.08±0.42 D in group 1 and 1.51±0.55 D in group 2, with a significant difference (P=0.001).

CONCLUSION

Both SICS and PHACO give excellent results, both anatomical and refractive. However, SICS appears to be more advantageous than PHACO in terms of speed, cost, and independence from technology, and appears to be better suited to dense cataracts and mass surgery.

An evaluation of intraoperative and postoperative outcomes of torsional mode versus longitudinal ultrasound mode phacoemulsification: a Meta-analysis

AIM

To evaluate and compare the intraoperative parameters and postoperative outcomes of torsional mode and longitudinal mode of phacoemulsification.

METHODS

Pertinent studies were identified by a computerized MEDLINE search from January 2002 to September 2013. The Meta-analysis is composed of two parts. In the first part the intraoperative parameters were considered: ultrasound time (UST) and cumulative dissipated energy (CDE). The intraoperative values were also distinctly considered for two categories (moderate and hard cataract group) depending on the nuclear opacity grade. In the second part of the study the postoperative outcomes as the best corrected visual acuity (BCVA) and the endothelial cell loss (ECL) were taken in consideration.

RESULTS

The UST and CDE values proved statistically significant in support of torsional mode for both moderate and hard cataract group. The analysis of BCVA did not present statistically significant difference between the two surgical modalities. The ECL count was statistically significant in support of torsional mode (P<0.001).

CONCLUSION

The Meta-analysis shows the superiority of the torsional mode for intraoperative parameters (UST, CDE) and postoperative ECL outcomes.

Emerging issues in radiogenic cataracts and cardiovascular disease

In 2011, the International Commission on Radiological Protection issued a statement on tissue reactions (formerly termed non-stochastic or deterministic effects) to recommend lowering the threshold for cataracts and the occupational equivalent dose limit for the crystalline lens of the eye. Furthermore, this statement was the first to list circulatory disease (cardiovascular and cerebrovascular disease) as a health hazard of radiation exposure and to assign its threshold for the heart and brain. These changes have stimulated various discussions and may have impacts on some radiation workers, such as those in the medical sector. This paper considers emerging issues associated with cataracts and cardiovascular disease. For cataracts, topics dealt with herein include (i) the progressive nature, stochastic nature, target cells and trigger events of lens opacification, (ii) roles of lens protein denaturation, oxidative stress, calcium ions, tumor suppressors and DNA repair factors in cataractogenesis, (iii) dose rate effect, radiation weighting factor, and classification systems for cataracts, and (iv) estimation of the lens dose in clinical settings. Topics for cardiovascular disease include experimental animal models, relevant surrogate markers, latency period, target tissues, and roles of inflammation and cellular senescence. Future research needs are also discussed.

Gender and cataract--the role of estrogen

There is evidence from epidemiologic data that cataract is more common in women than men. This is not solely due to a higher rate of cataract extraction in women, as is the case in the western world, but several population-based studies show that females have a higher prevalence of lens opacities, especially cortical. There is no firm evidence that lifestyle-related factors are the cause of this gender discrepancy. Focus has therefore been directed towards the role of estrogen in cataract formation. Although data on endogenous and exogenous estrogen involvement in cataractogenesis are conflicting, some studies have indicated that hormone therapy may decrease the risk of cataract and thus be protective. It has been hypothesized that the decrease in estrogen at menopause cause increased risk of cataract in women, i.e. not strictly the concentration of estrogen, but more the withdrawal effect. Estrogens are known to exert several anti-aging effects that may explain the longer lifespan in women, including metabolically beneficial effects, neuroprotection, preservation of telomeres and anti-oxidative properties. Since oxidative stress is considered important in cataractogenesis, studies have investigated the effects of estrogens on lens epithelial cells in culture or in animal models. Several investigators have found protection by physiological concentrations of 17β-estradiol against oxidative stress induced by H2O2 in cultured lens epithelial cells. Although both main types of estrogen receptors, ERα and ERβ, have been demonstrated in lens epithelium, most studies so far indicate that the estrogen-mediated protection in the lens is exerted through non-genomic, i.e. receptor-independent mechanisms, possibly through phosphorylation of extracellular signal-regulated kinase (ERK1/ERK2), a member of the mitogen-activated protein kinase (MAPK)-signaling pathway. Further studies are needed, both epidemiologic as to the role of hormone therapies, and laboratory studies regarding molecular estrogen-mediated mechanisms, in order to comprehend the role of estrogens on cataract formation.

23-Gauge Pars Plana Vitrectomy Versus Scleral Buckling Versus Combined Pars Plana Vitrectomy-Scleral Buckling for Medium-Complexity Retinal Detachment Repair

PURPOSE

To compare the anatomic and visual outcomes of 23-gauge pars plana vitrectomy (PPV), scleral buckling (SB), and combined 23-gauge PPV/SB in the treatment of primary medium-complexity rhegmatogenous retinal detachment (RRD).

DESIGN

A retrospective, consecutive case series.

METHODS

A consecutive chart review of patients with medium-complexity RRD treated with PPV, SB, and combined PPV/SB was conducted. The primary outcome measure was retinal reattachment at 6 months' follow-up. The secondary outcome measure was Snellen best-corrected visual acuity (BCVA) of 20/40 or better at 6 months' follow-up.

RESULTS

Five hundred sixty-five cases met inclusion criteria. The overall primary anatomic success rate was 83.6% (95% confidence interval, 80.3%-86.5%). Logistic regression analysis did not demonstrate a significant difference between the 3 techniques in terms of likelihood of anatomic success or likelihood of achieving a Snellen BCVA of 20/40 or better. Patients with multiple breaks in 2 or more quadrants or inferior breaks were more likely to undergo SB/PPV, whereas patients with phakic lens status with breaks confined to 1 quadrant were more likely to undergo SB. Patients with macula-off detachments and those with postoperative proliferative vitreoretinopathy were less likely to achieve a Snellen BCVA of 20/40 or better.

CONCLUSIONS

Although there was not a statistically significant difference in the anatomic and visual outcomes between the repair techniques analyzed, SB/PPV was performed on the more complicated spectrum of medium-complexity RRDs with the overall highest anatomic success rate and therefore may be the most effective repair technique for this patient population.

An increase in phosphorylation and truncation of crystallin with the progression of cataracts

Background

Cataracts are the leading cause of blindness worldwide; however, there is no evidence regarding the direct formation of cataracts. At present, there is no treatment method other than surgery to prevent the formation or progression of cataracts.

Objective

Understanding the protein changes during various stages of cataracts might help realize the mechanism of the formation and progression of cataracts.

Methods

Lens materials were collected from cataract surgery. Cataracts were classified according to lens opacity using the gradation of the Lens Opacities Classification System. Lens proteins were separated by 2-dimensional polyacrylamide gel electrophoresis. Protein spots were visualized by Coomassie blue staining, and expression patterns were analyzed. Protein spots of interest were excised from 2-dimensional polyacrylamide gel electrophoresis gels, digested in situ with trypsin, and analyzed by mass spectrometry and liquid chromatographic tandem mass spectrometry.

Results

Crystallin was the major protein in the cataract lens, and αA, βB1, αB, and βA4 were the dominant types. Crystallin αB and βA4 increased with the formation of lens opacity. Moreover, phosphorylation and truncation of these proteins increased with the progression of cataracts.

Conclusion

Crystallin αB and βA4 and phosphorylation and truncation of crystallin in the lens might contribute to the formation of cataracts. In contrast, acetylation was not dominant in the progression of cataracts and did not play major role in the formation of cataracts.

New light for old eyes: comparing melanopsin-mediated non-visual benefits of blue-light and UV-blocking intraocular lenses

BACKGROUND/AIMS

Melanopsin-expressing photosensitive retinal ganglion cells form a blue-light-sensitive non-visual system mediating diverse physiological effects including circadian entrainment and cognitive alertness. Reduced blue wavelength retinal illumination through cataract formation is thought to blunt these responses while cataract surgery and intraocular lens (IOL) implantation have been shown to have beneficial effects on sleep and cognition. We aimed to use the reaction time (RT) task and the Epworth Sleepiness Score (ESS) as a validated objective platform to compare non-visual benefits of UV- and blue-blocking IOLs.

METHODS

Patients were prospectively randomised to receive either a UV- or blue-blocking IOL, performing an RT test and ESS questionnaire before and after surgery. Optical blurring at the second test controlled for visual improvement. Non-operative age-matched controls were recruited for comparison.

RESULTS

80 participants completed the study. Those undergoing first-eye phacoemulsification demonstrated significant improvements in RT over control (p=0.001) and second-eye surgery patients (p=0.03). Moreover, reduced daytime sleepiness was measured by ESS for the first-eye surgery group (p=0.008) but not for the second-eye group (p=0.09). Choice of UV- or blue-blocking IOL made no significant difference to magnitude of cognitive improvement (p=0.272).

CONCLUSIONS

Phacoemulsification, particularly first-eye surgery, has a strong positive effect on cognition and daytime alertness, regardless of IOL type.

All biometric components are important in anisometropia, not just axial length

BACKGROUND

No study to date has looked into the relationship between ocular biometrics with anisometropia exclusively; therefore, the purpose of this study was to determine the relationship between anisometropia and ocular biometrics.

METHODS

In a cross-sectional study with multistage cluster sampling, 6311 people in the 40-64-year-old age group from the population of Shahroud, Iran, were selected. Of these, 5190 people participated in the study. For all participants, tests for visual acuity, cycloplegic and non-cycloplegic refraction, slit lamp test and fundoscopy were performed. All participants underwent biometric examinations using the Allegro Biograph (WaveLight AG, Erlangen, Germany).

RESULTS

Asymmetry of axial length, corneal power, vitreous chamber depth, anterior chamber depth, lens thickness and lens power were significantly more among participants who were anisometropic than those who were non-anisometropic. The correlation of anisometropia with axial length asymmetry was 0.735, 0.273 with corneal power, 0.183 with anterior chamber depth and 0.311 with lens power (p<0.001). In a multiple linear regression model, anisometropia was found to have significant associations with axial length asymmetry (standard coefficient (SC)=0.905), corneal power asymmetry (SC=0.350), lens power asymmetry (SC=0.454), nuclear opacity asymmetry (SC=0.074) and age (SC=0.28) (R(2)=85.1%). According to the linear regression model, corneal power had the strongest association with anisoastigmatism.

CONCLUSIONS

Axial length asymmetry has the strongest correlation with anisometropia; nonetheless, other components of ocular biometrics such as corneal power, lens opacity, lens power and anterior chamber depth are related to anisometropia as well. More than 10% of changes in anisometropia can be explained with changes in factors other than asymmetry of ocular biometrics and lens opacity.

The association of cataract with leukocyte telomere length in older adults: defining a new marker of aging

Lens transparency, or the magnitude of cataract severity, is a potential in vivo marker of aging distinguishable from diagnosed cataract. To explore lens transparency as a marker of aging, we determined its association with leukocyte telomere length (LTL) measured with quantitative polymerase chain reaction. Cataract severity was directly measured in 259 participants, and prevalent cataract and incident cataract surgery were ascertained in 2,750 participants of the Health, Aging, and Body Composition Study. LTL was unassociated with clinical cataract outcomes. Six of 259 had successfully aged lenses and a mean LTL of 5,700 bp, whereas 253/259 with poorly aged lenses had a mean LTL of 4,770 bp. Participants with a 1,000 bp greater mean LTL had nearly half the odds of any cataract (odds ratio = 0.47, 95% confidence interval 0.22-1.02) after adjustment. Lens transparency might be associated with longer LTL in community-dwelling older adults and should be investigated further as a possible biomarker of aging.

LOCS III examination at the slit lamp, do settings matter?

PURPOSE

To explore whether slit lamp settings may influence measurements made with the LOCS III grading system. The following were tested using a total of 221 subjects: 1. Test-retest variability (with and without the neutral density filter). 2. Readings with and then without the neutral density filter. 3. Readings with maximum and minimum illumination (filter and rheostat). 4. Examinations with different slit beam width. 5. Light output from 10 slit lamps (Haag-Streit 900BM) was measured using a lightmeter.

RESULTS

The 95% limits of agreement (test-retest examination) for nuclear opacity (NO), nuclear colour (NC), cortical opacity (C), and posterior subcapsular lens opacity (P) were 0.66, 0.60, 0.62 and 0.39, respectively, using standard settings. Corresponding results with the neutral density filter were similar. Examinations performed with and without the neutral density filter showed that the 95% limits of agreement increased by a factor of at least 1.7 compared with test retest data (NO and NC) and 2.2 for (C and P) (p < 0.001 (f test)). Maximum vs. minimum brightness settings increased variability by a factor of at least 2.1 (NO and NC) and 3 (C and P) (p < 0.001 (f test)). Changing beam width measurements produced a significant systematic measurement bias of 0.3 for NO and 0.4 for NC (P < 0.01 (t test)), a wider beam giving a higher score. Individual slit lamps may vary by a factor of four in their light output levels for apparently identical settings. The range of illumination produced by a slit lamp is 46-fold.

CONCLUSIONS

For nuclear opacity and nuclear colour measurements, changing settings between examinations increases variability without evidence of systematic bias. However, using a thicker slit beam induced a systematic bias. For cortical and posterior subcapsular lens opacity, varying the illumination had more marked effects on reproducibility without a systematic bias.

Towards automatic grading of nuclear cataract

Objective quantification of lens images is essential for cataract assessment and treatment. In this paper, bottom-up and top-down strategies are combined to detect the lens contour from the slit-lamp images. The center of the lens is localized by horizontal and vertical intensity profile clustering and the lens contour is estimated by fitting an ellipse. A modified active shape model (ASM) is further applied to detect the contour of the lens. The average intensity inside the lens is employed as the indicator of nuclear opacity. The relationship between our automated nuclear cataract assessment and the clinical grading is analyzed. The preliminary study of forty images shows that the difference between automatic grading and clinical grading is acceptable.

Low-intensity ultraviolet A irradiation of the lens capsule to remove lens epithelial cells during cataract surgery

PURPOSE

To assess the effectiveness and safety of low-intensity ultraviolet A (UVA) irradiation in removing lens epithelial cells (LECs) during cataract surgery and compare them with those of mechanical polishing and no treatment.

SETTING

Eyecove Ophthalmology Clinics, Pune, India.

METHODS

This prospective randomized double-masked study consisted of preoperative screening of 36 patients, of which 30 met the inclusion criteria and were recruited. The patients had routine cataract surgery. A bean-shaped capsulorhexis was performed. After the nucleus and cortex were removed, the capsular bag was irradiated from inside with low-intensity UVA in 1 group. A second group had mechanical polishing, and a third group was not treated. A small flap of the anterior capsule was removed in each patient. The flap was stained and mounted in a Fuchs-Rosenthal chamber. For estimation of effectiveness, the area of capsule covered with epithelial cells was estimated by examination under a light microscope. One day postoperatively, an examination was performed to assess the safety of each technique.

RESULTS

The area of the capsule from which the LECs were removed was significantly larger in the UVA-irradiation group than in the mechanical-polishing group (P = .001) and the no-treatment group (P = .001). There was no significant difference between the mechanical-polishing and no-treatment groups (P>.05). The area of the capsule flap that was covered with LECs was significantly less in the UVA-irradiation group than in the mechanical-polishing group (P = .017) and the no-treatment group (P = .001). The mechanical-polishing group and no-treatment group were not significantly different from each other (P>.05). Corneal edema was significantly less in the UVA-irradiation group than in the mechanical-polishing group (P<.001) and no-treatment group (P = .012). No patient in the UVA-irradiation group had postoperative lid edema; 8 patients in each of the other 2 groups had lid edema. The difference was statistically significant (P<.0001). Pupil size was significantly larger in the UVA-irradiation group than in the mechanical-polishing group and no-treatment group; the difference was significant (both P = .0001). There was no significant difference in pupil size in the mechanical-polishing group and no-treatment group. No significant difference was observed between the 3 groups in visual acuity, conjunctival edema, anterior chamber flare, and intraocular pressure.

CONCLUSION

Ultraviolet A irradiation of the capsular bag was effective and safe in removing LECs from the anterior capsule during cataract surgery.

Expression of TGF-β2 mRNA and PCNA, FN protein in lens epithelial cells in age-related nuclear and cortex cataract

By using RT-PCR and immunohistochemistry, the expressions of transforming growth factor beta2 (TGF-beta2) mRNA, proliferating cell nuclear antigen (PCNA) and fibronection (FN) protein in lens epithelial cells (LECs) of age-related nuclear and cortex cataract were detected and compared. The results of RT-PCR revealed that the expression of TGF-beta2 mRNA was higher in cortex cataract than in nuclear cataract. Immunohistochemistry demonstrated that the expression of PCNA protein was lower and the expression of FN protein was higher in cortex cataract than in nuclear cataract. It was suggested that TGF-beta2, PCNA and FN might take important parts in the process of age-related cataract. Cortex cataract was related to the transdifferentiation of LECs, and nuclear cataract to the proliferation of LECs.

A randomised controlled feasibility trial of vitrectomy versus laser for diabetic macular oedema

AIM

(1) To evaluate whether vitrectomy is preferable to further macular laser in improving visual acuity and resolving retinal thickening in patients with diabetic macular oedema (DMO) despite previous laser and no macular traction. (2) To determine the feasibility of further trials in this population in terms of magnitude of comparative clinical effect, rate of recruitment, and loss to follow up.

METHODS

A randomised controlled feasibility study. Patients with DMO and a visual acuity of 0.3 logMAR (6/12) or worse after one or more macular laser treatments were randomised on a 1:1 basis to either pars plana vitrectomy (PPV) with internal limiting membrane (ILM) peeling or further macular laser. Patients with a posterior vitreous detachment, biomicroscopic evidence of retinal traction, or a taut thickened posterior hyaloid (TTPH) were excluded. Primary outcome measures were (1) best corrected logMAR visual acuity, (2) mean central macular thickness on optical coherence tomography, and (3) rate of recruitment and loss to follow up. Analysis was on an intention to treat basis.

RESULTS

19 patients were randomised to PPV and 21 to further macular laser. The mean baseline logMAR visual acuity was 0.65 (SD 0.28) for the group randomised to PPV and 0.60 (0.23) for the group randomised to laser. The mean change in best corrected visual acuity of the vitrectomy group was deterioration by 0.05 logMAR, while in the control group the mean change was an improvement of 0.03 logMAR. The median (interquartile range) baseline central macular thickness was 403 (337, 492) for the group randomised to PPV and 387 (298, 491) for the controls randomised to laser. The median change in central macular thickness from baseline to review in the vitrectomy group was a thinning by 73 mum (20%) and by 29 mum (10.7%) in the control laser group. This single centre was able to recruit 40 patients in 18 months with follow up of 82% at 1 year.

CONCLUSION

A randomised controlled trial was found to be potentially feasible in this population, the rate of recruitment was however slow and one in five patients were lost to follow up because of death and ill health. These data provide little evidence in terms of visual acuity and macular thickness of any benefit of vitrectomy over further macular laser in patients with an attached hyaloid, DMO despite previous laser, and no clinically evident macular traction or TTPH.

Prevalence of canine cataract: preliminary results of a cross-sectional study

OBJECTIVE

In this study 2000 dogs were examined ophthalmoscopically to determine presence of cataract.

MATERIALS AND METHODS

The dogs examined were predominantly from veterinary hospital populations but also from the Waltham Center For Pet Nutrition, rehoming charities and breeding kennels. Prevalence of cataract was thus determined for different age groups (year cohorts). The age at which prevalence of cataract was 50% (C50) was determined indirectly from a fitted prevalence curve.

RESULTS

The mean +/- standard deviation of C50 for all dogs in the study was 9.4 +/- 3.3 years. All dogs over 13.5 years were affected by some degree of lens opacity. C50 was determined for animals of different genders and different breeds. For dogs of six breeds sufficient data were available for calculation of breed-specific C50. In these dogs C50 was positively correlated with longevity with a least squares correlation coefficient of 0.74.

CONCLUSION

The study yields novel findings regarding the prevalence and incidence of cataract in the dog and forms the basis for considerable further work on the epidemiology and pathophysiology of age-related cataract in the dog.

The relationship between nuclear colour and opalescence on the LOCSIII scale and physical characteristics of cataract nuclei

PURPOSE

To evaluate the compression characteristics of the human lens nucleocortex in relation to its LOCSIII clinical grading.

METHODS

Sixteen subjects undergoing planned extracapsular cataract surgery had pre-operative slit-lamp examination and assessment of cataract LOCSIII grade followed by postoperative in vitro evaluation of the nucleus with measurement of 'linear compressibility' by a purpose-designed caliper incorporating a strain gauge, enabling the derivation of a graph of nuclear compression (D (mm) against applied force (F (N)).

RESULTS

Nuclear colour correlates with the force required to compress a lens to 75% of its original depth (F75) (R = 0.625, P = 0.017). Nuclear opalescence correlates with the force required to compress a lens to 75% of its original depth (R = 0.651, P = 0.012) and inversely with linear compressibility (DeltaD/DeltaF, the slope of the graph of nuclear compression against applied force) (R = -0.610, P = 0.014). F75 is a direct and linear compressibility is an inverse related parameter of lens nucleus 'hardness'.

CONCLUSION

A new instrument is described which allows measurement of 'hardness'-related compression characteristics of the human cataract in vitro. There is a relationship between the LOCSIII clinical classification of nuclear cataracts and mechanical compression characteristics of the cataractous lens. LOCSIII classification may aid the preoperative planning of an appropriate surgical approach to an individual cataract.

Genetic and environmental factors in age-related nuclear cataracts in monozygotic and dizygotic twins

BACKGROUND

Age-related cataracts are a major public health problem. The relative importance of genes and environment in the causation of nuclear cataracts, the most common form of age-related cataracts, is not known.

METHODS

We studied 506 pairs of female twins (226 monozygotic and 280 dizygotic) who were 50 to 79 years old (mean, 62). The amount of nuclear cataract in the right and left eyes was determined objectively by analysis of Scheimpflug lens photographs (yielding three measures) and subjectively with use of the Oxford Clinical Cataract Classification and Grading System (yielding one measure). All eight measures (four in each eye) were subsequently combined in one summary measure of nuclear cataract for each woman. A univariate maximum-likelihood model was used to estimate the variance of the genetic and environmental contributions to each of the measures.

RESULTS

The different measures of cataract formation were highly correlated (correlation coefficients, 0.71 to 0.94). The mean scores were similar for the right and left eyes and for monozygotic and dizygotic twins. Quantitative genetic modeling of each of the nuclear-cataract scores invariably resulted in a best-fitting model that involved additive genetic effects, unique environmental effects, and age. The common environmental and dominant genetic effects could be removed from the models without significant loss of fit. The overall heritability in the combined nuclear-cataract score (the proportion of the variance explained by genetic factors) was 48 percent (95 percent confidence interval, 42 to 54 percent); age accounted for 38 percent of the variance (95 percent confidence interval, 31 to 44 percent) and unique environmental effects for 14 percent (95 percent confidence interval, 12 to 18 percent).

CONCLUSIONS

Genetic effects are important even in such a clearly age-related disease as nuclear cataract, explaining almost 50 percent of the variation in the severity of this disease.

Associations between lens features assessed in the Oxford Clinical Cataract Classification and Grading System

PURPOSE

To study the associations between eleven lens features graded according to the Oxford Clinical Cataract Classification and Grading System (OCCCGS).

METHOD

560 subjects taking part in the Melton Eye Study had their lenses graded according to the OCCCGS by one of two examiners. Associations between features were examined using log-linear models for categorised grades. Adjustment was made for age, sex and grader.

RESULTS

Within subjects, the two nuclear features, white nuclear scatter and brunescence, are closely related with one another, as are coronary flakes and focal-dots, but these two groupings are negatively associated. Cortical spoke, fibrefolds and waterclefts are all associated with one another and this group is positively associated with coronary flakes and focal-dots. Posterior subcapsular and anterior subcapsular opacity are associated with one another and with cortical spokes. A within-eye analysis gives similar results.

CONCLUSION

These associations may be important in defining cataract subtypes and in identifying minor features that indicate early cataract development.