Correlation of lens density measured using the Pentacam Scheimpflug system with the Lens Opacities Classification System III grading score and visual acuity in age-related nuclear cataract

Quantitative Scheimpflug camera study of the lens density in healthy Turkish population

The purpose of this study is to evaluate the association between the age and the density of anterior, posterior, and nuclear parts of lens and detect the normal lens density (LD) values in different age groups. 370 eyes of 370 voluntary healthy Turkish subjects were included. These were divided in four groups according to their age. These were Group 1 (51-65 years), Group 2 (41-50 years), Group 3 (31-40 years) and Group 4 (20-30 years). LD values of anterior, nuclear, posterior, and total (average) were measured using Pentacam HR Scheimpflug camera system. Both eyes of each subject were scanned twice in automatic release and 50-picture 3-dimensional (3D) scan modes by one experienced observer. 207 of the participants were females and 163 were males, with a mean age of 40.57 ± 13.06 years. The differences between groups in terms of nuclear area, posterior area, and average LD measurements were significant but anterior area was not. The nuclear area and average LD had high positive correlation with age (r = 0.72, p < 0.001, r = 0.63, p < 0.001, respectively); posterior area LD had a weak negative correlation with age (r = -0.16, p = 0.001). The mean LD values between female and male subjects showed no significant difference. The anterior region of the lens has the highest and nuclear area has the lowest value of LD in young people. In older people, the anterior area did not show a significant change, nuclear and total areas showed a significant increase but posterior area showed a significant decrease.

Objective Assessment of Nuclear and Cortical Cataracts through Scheimpflug Images: Agreement with the LOCS III Scale

PURPOSE

To assess nuclear and cortical opacities through the objective analysis of Scheimpflug images, and to check the correlation with the Lens Opacity Classification System III (LOCS III).

METHODS

Nuclear and cortical opacities were graded according to the LOCS III rules after pupil dilation. The maximum and average pixel intensity values along an elliptical mask within the lens nucleus were taken to analyse nuclear cataracts. A new metric based on the percentage of opaque pixels within a region of interest was used to analyse cortical cataracts. The percentage of opaque pixels was also calculated for half, third and quarter areas from the region of interest's periphery.

RESULTS

The maximum and average intensity values along the nucleus were directly proportional to the LOCS III grade: The larger the LOCS III value, the larger maximum and average intensity ones. These metrics showed a positive and significant correlation with the LOCS grade: The larger the LOCS grade, the higher was percentage of opaque pixels along the cortex within the same mask's size. This metric showed a significant correlation to the LOCS grade.

CONCLUSION

The metrics used to assess nuclear opacities showed good correlation with the LOCS III. The percentage of opaque pixels showed to be a useful metric to measure objectively the severity of the cortical opacity. These metrics could be implemented in an algorithm to detect and grade lens opacities automatically and objectively.

Objective assessment of nuclear cataract: comparison of double-pass and Scheimpflug systems

PURPOSE

To compare the objective assessment of lens density by 2 systems (double-pass Optical Quality Analysis System and Pentacam Scheimpflug) in eyes with age-related nuclear cataract.

SETTING

Department of Ophthalmology and Visual Science, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, South Korea.

DESIGN

Cross-sectional study.

METHODS

In eyes with age-related nuclear cataract, the objective lens density (0 to 100 points) was determined using the Scheimpflug system while subjective grading was achieved using the Lens Opacities Classification System III (LOCS III). The objective scatter index (OSI) (0 to 25) was assessed using the double-pass system.

RESULTS

This study enrolled 47 patients (70 eyes). The mean OSI was 4.08 ± 2.22 (SD), and the mean Scheimpflug-measured lens density was 16.44 ± 4.36; the 2 parameters were correlated (r = 0.764, P<.01). There was a positive linear correlation between the OSI and LOCS III grading scores for nuclear opalescence and nuclear color (r = 0.772 and r = 0.752, respectively; P<.01). The cumulated dissipated energy (CDE) was strongly correlated with the OSI (r = 0.768) and Scheimpflug-measured lens density (r = 0.753).

CONCLUSIONS

The OSI based on the double-pass system was correlated with the Scheimpflug-measured lens density, subjective lens grading, and CDE. The OSI may improve the preoperative evaluation of nuclear cataract and help predict phacodynamics in cataract surgery.

Repeatability of lens densitometry using Scheimpflug imaging

PURPOSE

To evaluate the repeatability of different lens densitometry analysis modes performed with Scheimpflug imaging using the Pentacam HR device.

SETTING

University eye hospital, Frankfurt am Main, Germany.

DESIGN

Cross-sectional study.

METHODS

Eyes were analyzed under mydriasis during 2 examinations performed by the same examiner. Three single measurements were taken to assess lens densitometry via 3 modes as follows: peak (maximum), linear (vertical axis), and 3-dimensional (3-D). Measurements were also taken using 3 cylindrical reference blocks (P) with different diameters (2.0 mm, 4.0 mm, 6.00 mm) composing the whole lens depth. Repeatability was tested using Bland-Altman analysis. As statistical parameters, the coefficient of repeatability (CoR) and the relative repeatability (RR) were applied.

RESULTS

The study analyzed 105 eyes. The CoR of the peak modus was 5.6 (RR, 29.8%); of the linear modus, 0.9 (RR, 8.8%); and of the 3-D modus, 0.36 (RR, 3.6%). The values of the P mode were lower, with a CoR between 0.19 and 0.30 (RR, 2.1%-3.3%).

CONCLUSIONS

Lens densitometry using Scheimpflug imaging was highly repeatable. However, repeatability was dependent on the analysis mode used. Repeatability decreased with increasing opacification.

Evaluation of a 345 nm Femtosecond Laser for Corneal Surgery with Respect to Intraocular Radiation Hazard

PURPOSE

We report our findings from a preclinical safety study designed to assess potential side effects of corneal ultraviolet femtosecond laser treatment on lens and retina.

METHODS

Refractive lenticules (-5 dpt) with a diameter of 6 mm were created in the right cornea of eight Dutch Belted rabbits. Radiant exposure was 0.5 J/cm² in two animals and 18 J/cm² in six animals. The presence of lens opacities was assessed prior to and up to six months following laser application using Scheimpflug images (Pentacam, Oculus) and backscatter analysis (Opacity Lensmeter 702, Interzeag). Ganzfeld flash and flicker electroretinogram (ERG) recordings were obtained from both eyes prior to and up to six weeks following laser application. At the study endpoint, retinas were examined by light microscopy.

RESULTS

Independent of energy dose applied, no cataract formation could be observed clinically or with either of the two objective methods used. No changes in ERG recordings over time and no difference between treated and untreated eye were detected. Histologically, retinal morphology was preserved and retinal pigment epithelium as well as photoreceptor inner and outer segments appeared undamaged. Quantitative digital image analysis did not reveal cell loss in inner or outer nuclear layers.

CONCLUSIONS

Our analysis confirms theoretical considerations suggesting that ultraviolet femtosecond laser treatment of the cornea is safe for intraocular tissues. Transmitted light including stray light induces no photochemical effects in lens or retina at energy levels much higher than required for the clinical purpose. These conclusions cannot be applied to eyes with pre-existing retinal damage, as these may be more vulnerable to light.

Correlation among lens opacities classification system III grading, visual function index-14, pentacam nucleus staging, and objective scatter index for cataract assessment

PURPOSE

To investigate the relationship among Lens Opacities Classification System III (LOCS III) grading score, Visual Function Index-14 (VF-14) score, average lens density by the Pentacam Nucleus Staging system, and the objective scatter index measured by the Optical Quality Analysis System in age-related cataract patients.

DESIGN

Prospective, single-center, cross-sectional study.

METHODS

Thirty-six subjects (60 eyes) with age-related cataract were recruited. Subjects with any corneal anomaly potentially affecting intraocular scatter were excluded. The best-corrected visual acuity (BCVA), LOCS III nuclear opalescence score and cortical cataract score, VF-14 score, average lens density, and objective scatter index were obtained. Correlations among these parameters were analyzed.

RESULTS

The LOCS III nuclear opalescence score was correlated with the BCVA (r = 0.438; P = .001), objective scatter index (r = 0.543; P < .001), and average lens density (r = 0.621; P < .001). The objective scatter index was also correlated with the BCVA (r = 0.779; P < .001) and the average lens density (r = 0.320; P = .013). The VF-14 score had the strongest correlation with the objective scatter index (r = -0.712; P < .001). The difference between groups with objective scatter index<3.0 and ≥3.0 was significant with regard to BCVA, average lens density, LOCS III nuclear opalescence score, and VF-14 score.

CONCLUSIONS

LOCS III grading remains an economical and effective method to assess lens opacities, especially in the formation of early cortex cataracts. The objective scatter index can be a useful parameter to objectively analyze the correlation between ocular examination findings and patient concerns. Furthermore, the objective scatter index scores ≥3.0 can be a possible objective cut-off for preoperative decision making.

Factors influencing contrast sensitivity function in myopic eyes

Purpose

To evaluate the factors affecting the area under the log contrast sensitivity function (AULCSF) in healthy myopic eyes.

Methods

We retrospectively examined 201 eyes of 201 consecutive subjects (age, 31.8±7.4 years (mean ± standard deviation)) with myopic refractive errors of −1.25 to −8.25 diopters (D). From the contrast sensitivity data, the area under the log contrast sensitivity function (AULCSF) was calculated. Stepwise multiple regression analysis was used to assess the factors affecting the AULCSF.

Results

The mean AULSCF was 1.09±0.09 (0.89 to 1.55). Explanatory variables relevant to the AULCSF were, in order of influence, the objective scattering index (OSI) (p = 0.018, partial regression coefficient B = –0.032) and logMAR CDVA (p = 0.022, B = –0.209) (adjusted R² = 0.231). No significant correlation was seen with other clinical factors such as gender, manifest refraction, pupil size, lens density, corneal HOAs, or ocular HOAs.

Conclusions

Although the great majority of the variance remains unexplained, eyes with lower OSI and better CDVA are more predisposed to show higher contrast sensitivity function. These results indicate that not only CDVA but also intraocular forward scattering may play some role in predicting the contrast sensitivity function in myopic subjects.

Measurement of lens density using Scheimpflug imaging system as a screening test in the field of health examination for age-related cataract

PURPOSE

To assess Pentacam (Oculus, Wetzlar, Germany) Scheimpflug quantitative images in evaluating lens density and providing objective measurements to suggest optimal time of cataract surgery in the field of health examination.

METHODS

Two hundred and twenty-nine eyes with age-related cataract were enrolled. Lens density was measured using Pentacam. All Pentacam images were exported to ImageJ (NIH, Bethesda, Maryland, USA) for quantitative analysis. Average lens density (ALD) and nuclear lens density (NLD) were calculated. Lens density was also evaluated by built-in Pentacam Nucleus Staging (PNS) software. Slit-lamp microscopy was performed for cataract grading according to Lens Opacification Classification System III (LOCS III). The best-corrected visual acuity (BCVA) was measured. All measurements were compared between the cataract surgery and non-cataract surgery groups.

RESULTS

The measurements of Pentacam images significantly correlated with LOCS III for nuclear opalescence (NO) and nuclear colour (NC) grading (p<0.01). Pentacam ImageJ showed higher correlation than PNS. The mean NLD was most highly correlated with NO (r=0.8833) and NC (r=0.6815). The maximum ALD was most highly correlated with cortical opacity (r=0.5381). All Pentacam measurements of lens density and BCVA were significantly different between the cataract surgery and non-surgery groups (p<0.01). The optimised cut-off values to perform cataract surgery for mean NLD and maximum ALD were 26 and 74, respectively (p<0.01).

CONCLUSIONS

The Pentacam ImageJ method provided objective measurements to evaluate cataracts needing surgery. The method has the potential to be generally applied in the field of health examination and is effective in screening patients with cataract.

Factors influencing long-term regression after posterior chamber phakic intraocular lens implantation for moderate to high myopia

PURPOSE

To evaluate the factors affecting the long-term regression after posterior chamber phakic intraocular lens (Visian ICL; STAAR Surgical) implantation for myopia.

DESIGN

Retrospective observational case series.

METHODS

We retrospectively examined 60 eyes of 35 consecutive patients (age, 38.4 ± 9.3 years [mean ± standard deviation]) with myopic refractive errors of -4.00 to -15.25 diopters (D) undergoing ICL implantation. We assessed the amount of myopic regression from 1 month to 6 years after surgery. Stepwise multiple regression analysis was used to assess the factors affecting the amount of myopic regression.

RESULTS

The mean myopic regression from 1 month to 6 years after surgery was -0.33 ± 0.71 D (0.75 to -3.00 D). Explanatory variables relevant to the myopic regression were, in order of influence, patient age (partial regression coefficient B = -0.042, P < .0001) and preoperative axial length (B = -0.186, P = .013) (adjusted R(2) = 0.300). No significant correlation was seen with other clinical factors such as sex, preoperative refraction, intraocular pressure, white-to-white distance, anterior chamber depth, central corneal thickness, or mean keratometric readings.

CONCLUSIONS

Although the great majority of the variance remains unexplained, eyes of older patients and eyes with longer axial length are more predisposed to show greater myopic regression after ICL implantation. These results indicate that not only patient age but also axial length may play some role in predicting the long-term refractive outcomes of this surgical procedure.

The Effect of Chronic Smoking on Lens Density in Young Adults

Purpose

To investigate the effect of chronic cigarette smoking on lens density by Pentacam HR lens densitometry in young adults.

Methods

Sixty chronic smokers who smoked at least 10 cigarettes per day for at least 2 years and 60 age- and sex-matched healthy control subjects were included in this prospective cross-sectional, comparative study. Presence of an ocular or systemic disease that might affect lens were determined as exclusion criteria. All individuals underwent complete ocular examination. Lens densitometry (LD) measurements were performed with Pentacam HR (Oculus, Wetzlar, Germany), dividing the lens into 3 areas: anterior area (anterior subcapsular and anterior cortical), nuclear area, and posterior area (posterior subcapsular and posterior cortical). Three-dimensional scan modes were used for measurements.

Results

The mean ages of group 1 and 2 were 25.85 ± 4.32 and 25.60 ± 5.14 years, respectively. The mean LD values in the 3 areas were higher in group 1 than group 2. However, only the mean LD value at the anterior area of group 1 was found to be statistically significantly higher (p = 0.047). There was no statistically significant difference in the mean LD measurements at the nuclear and posterior areas between the groups.

Conclusions

Our study demonstrated that the mean LD value of the anterior area was significantly higher in group 1, suggesting that chronic smoking may contribute to anterior cortical and subcapsular cataract development in young adults.

Clinical applications of Scheimpflug imaging in cataract surgery

Since the Scheimpflug principle was first described over a century ago, there has been a great interest among ophthalmologists for the use of Scheimpflug camera in anterior segment imaging. Scheimpflug imaging has since advanced significantly and modern day instruments provide comprehensive imaging and topographic data of the anterior segment. In this article the clinical applications and limitations of Scheimpflug imaging in modern cataract surgery patients are discussed. This article reviews recent work on assessment of lens transparency for cataract grading and integrity, using preoperative lens density measurements to help predict phacoemulsification parameters, its utility in challenging situations like capsular bag distension syndrome and traumatic cataract and assessment of density of the posterior capsule for objectively quantifying posterior-capsule opacification.

Correlation between cataract grading by Scheimpflug imaging and phaco time in phacoemulsification using peristaltic and venturi pumps

PURPOSE

To study the correlation among cataract grading system by Scheimpflug imaging (Oculus Pentacam® Nucleus Grading System [PNS]), effective phaco time (EPT), and surgical time (ST) using peristaltic and venturi pumps on the Whitestar Signature Phaco System (Abbott Medical Optics, Inc., Santa Ana, California, USA). 


METHODS

Patients scheduled to have bimanual microincision phacoemulsification by the same surgeon (T.F.) had Pentacam® Scheimpflug assessment using PNS and were randomly distributed into 
2 groups. In group 1, surgery was performed using peristaltic pump, and in group 2, using venturi pump. Parameters assessed in both groups included EPT and ST. 


RESULTS

Sixty eyes that had uneventful clear cornea phacoemulsification with implantation of foldable intraocular lens (IOL) were evaluated, 30 in each group. The EPT was statistically superior with higher nuclear density grades for both groups 1 and 2 (group 1 Spearman R = 0.739, p<0.001; group 2 Spearman R = 0.924, p<0.001). The ST statistically increased with nucleus density for both groups 1 and 2 (group 
1 Spearman R = 0.620, p<0.001; group 2 Spearman R = 0.643, p<0.001). Group 2 presented statistically significant reduction on median ST compared with group 1 for nucleus grading 2, 3, 4, and 5.

CONCLUSIONS

The PNS is an objective and reproducible method of grading nuclear cataract density and had a correlation with EPT. Peristaltic and venturi pumps in Signature Phaco System were similar in EPT but venturi pump reduced the median ST in nucleus with higher PNS, without repercussion on complications or anterior chamber stability.

The eye as a model of ageing in translational research--molecular, epigenetic and clinical aspects

The eye and visual system are valuable in many areas of translational research such as stem cell therapy, transplantation research and gene therapy. Changes in many ocular tissues can be measured directly, easily and objectively in vivo (e.g. lens transparency; retinal blood vessel calibre; corneal endothelial cell counts) and so the eye may also be a uniquely useful site as a model of ageing. This review details cellular, molecular and epigenetic mechanisms related to ageing within the eye, and describes ocular parameters that can be directly measured clinically and which might be of value in ageing research as the translational "window to the rest of the body". The eye is likely to provide a valuable model for validating biomarkers of ageing at molecular, epigenetic, cellular and clinical levels. A research agenda to definitively establish the relationship between biomarkers of ageing and ocular parameters is proposed.

Comprehensive assessment of nuclear and cortical backscatter metrics derived from rotating Scheimpflug images

PURPOSE

To quantify cataract in lens-backscatter metrics derived from Pentacam Scheimpflug photographs and determine the most predictive metrics for lens grading and visual performance measures.

SETTING

Large tertiary referral hospital in South Australia.

DESIGN

Evaluation of diagnostic test or technology.

METHODS

In patients attending a cataract clinic between 2005 and 2008, standardized clinical assessments were performed and Scheimpflug photographs taken. Thirteen measures of cataract backscatter were drawn from the images of nuclear and cortical cataract, including new metrics for cortical cataract. The relationships between lens-scatter metrics, visual performance, and lens grades were determined with stepwise multiple linear regression.

RESULTS

The study enrolled 342 eyes (177 patients). The Lens Opacities Classification System III (LOCS III) nuclear opalescence was best predicted by the average backscatter in the anterior half of the nucleus and the whole nucleus average (r(2) = 0.59). The LOCS III cortical grade was best predicted by the number of slices with significant cortical cataract (r(2) = 0.52), as was Pelli-Robson contrast sensitivity (r(2) = 0.16). Visual acuity was best predicted by the combined anterior half and whole nucleus averages (r(2) = 0.20). Pelli-Robson contrast sensitivity under glare was best predicted by a combination of the anterior half and whole nucleus averages and the calculated percentage of cortical cataract (r(2) = 0.16).

CONCLUSIONS

Scheimpflug image-derived metrics of nuclear scatter were predictive of visual acuity and contrast sensitivity, whereas metrics of cortical cataract were predictive of visual performance under glare. Automated reporting of cataract severity from Scheimpflug images could be useful clinically and should include measurements of cortical cataract.

FINANCIAL DISCLOSURE

Neither author has a financial or proprietary interest in any material or method mentioned.

Cataract progression in macular hole cases: results with vitrectomy or with observation

PURPOSE

To quantify the difference in progression of nuclear sclerotic cataract using Scheimpflug image analysis in patients with idiopathic full-thickness macular hole who were randomized to have vitrectomy and gas tamponade or to be observed.

SETTING

Moorfields Eye Hospital, London, United Kingdom.

DESIGN

Prospective randomized placebo-controlled masked clinical trial.

METHODS

As part of the Moorfields Macular Hole Study, patients with full-thickness macular hole who were randomized to have vitrectomy and gas tamponade or who were observed were compared. Patients had Scheimpflug image analysis of the crystalline lens to evaluate nuclear sclerosis progression by the single-masked observer at baseline and 3, 6, 9, and 12 months postoperatively.

RESULTS

Ninety-eight patients had sufficient baseline data for analysis. At 3 months and 6 months, vitrectomy patients had significant increases in nuclear density compared with baseline (16.6% and 33.9%, respectively) (both P<.0001). In the observation group, nuclear density increased by 1.4% between baseline and 6 months (P = .92). At 6 months, the increase in nuclear density from baseline was 24 times greater in the surgical group than in the observation group (P<.0001). No correlation between the rate of nuclear sclerosis progression and age or baseline nuclear density was found.

CONCLUSIONS

Rapid nuclear sclerosis progression was quantifiable by Scheimpflug image analysis in patients having surgery for idiopathic full-thickness macular hole.There was no [corrected] evidence of a correlation between age groups and the rate of cataract progression.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Psychophysical impact and optical and morphological characteristics of symptomatic non-advanced cataract

PURPOSE

To investigate whether psychophysical, morphological, and/or optical characteristics of symptomatic non-advanced cataract are complementary to, or more appropriate than, visual acuity (VA) for the purposes of recording visual data that reflect subjective visual difficulty in patients with cataract that exhibit relative sparing of high contrast acuity (0.4 logarithm of minimal angle of resolution (logMAR) scale or better).

METHODS

Eighty-two patients with symptomatic non-advanced cataract and no other ocular pathology were asked to complete a validated questionnaire, and to perform a series of visual function assessments including: corrected distance VA (CDVA); photopic and mesopic contrast sensitivity; photopic and mesopic glare disability (GD); reading acuity and reading speed; stereoacuity; and retinal sensitivity. Optical and morphological characteristics of the cataract were evaluated by lens optical density and by the Lens Opacities Classification System III, respectively. Correlations between questionnaire score and each of these measures were calculated.

RESULTS

Statistically significant negative correlations were observed between the Rasch-scaled questionnaire score and mesopic GD (at 3 and 6 cycles per degree (cpd); r=-0.396 (P<0.01) and -0.451 (P<0.05), respectively) and between the Rasch-scaled questionnaire score and photopic GD (at 3 and 6 cpd; r=-0.328 (P<0.01) and -0.440 (P<0.01), respectively).

CONCLUSION

Symptomatic non-advanced cataract, in the presence of good CDVA, is associated with measurable subjective visual difficulty, best reflected in a decrease in mesopic and photopic GD (at medium spatial frequencies). CDVA does not reflect the patient's visual dissatisfaction in such cases.

Morphologic changes in the anterior chamber in patients with cortical or nuclear age-related cataract

PURPOSE

To assess and compare the morphologic changes in the anterior segment in eyes with nuclear or cortical age-related cataract using Scheimpflug imaging.

SETTING

Peking University People's Hospital, Beijing, China.

DESIGN

Case-control study.

METHODS

Patients with nuclear or cortical age-related cataract were recruited. The grade of nuclear opalescence or cortical opacity was assessed using the Lens Opacities Classification System III (LOCS III). A group of elderly subjects with a clear lens and normal vision served as the control group. Anterior chamber depth (ACD), anterior chamber volume (ACV), and lens thickness were evaluated using Scheimpflug imaging (Pentacam).

RESULTS

Two hundred sixty-nine patients (330 eyes) were recruited. Thirty eyes were enrolled for each nuclear opalescence and cortical grade. The control group comprised 30 eyes (19 subjects). In eyes with age-related cataract, lens thickness increased with an increase in cortical opacity, whereas the ACD and ACV values decreased. The ACD was inversely correlated with LOCS III grades for nuclear opalescence (r = -0.197, P = .004), nuclear color (r = -0.195, P = .005), and cortical opacity (r = -0.508, P<.005). There were significant differences in lens thickness, ACD, and ACV between nuclear color, nuclear opalescence, and cortical opacity for LOCS III grades 3, 4, and 5, respectively.

CONCLUSIONS

There were significant differences in lens thickness, ACD, and ACV between nuclear and cortical age-related cataracts. The ACD decreased more in eyes with cortical cataract, suggesting that the risk for angle-closure glaucoma may be greater in cases of cortical opacity in which lens expansion is greater.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Objective evaluation of the changes in the crystalline lens during accommodation in young and presbyopic populations using Pentacam HR system

AIM

To quantify the changes in the lens profile with accommodation in different age groups.

METHODS

The Pentacam HR system was used to obtain the images of the anterior eye segment from 23 young and 15 presbyopic emmetropic subjects in unaccommodated (with an accommodation stimulus of 0.0D) and accommodated (with an accommodation stimulus of 5.0D for the young group and 1.0D for the presbyopic group) states. The phakic crystalline lens shape, including curvature of crystalline lens and central lens thickness (CLT), and the measurements of anterior segment length (ASL), central anterior chamber depth (CACD) were investigated. The anterior chamber volume (ACV) was also measured.

RESULTS

The reduction of CACD and ACV were significant in both groups after accommodation stimulus. From the profile of anterior eye segment, a significant decrease in anterior crystalline lens radii of curvature (-2.52mm) and a mean increase in CLT (0.222mm) and ASL (0.108mm) were found in the young group with an accommodation stimulus of 5.0D. However, no statistically significant changes of CLT, ASL, or crystalline lens radii of curvature were found in the presbyopic group.

CONCLUSION

Our data showed that the shallowing of anterior chamber during accommodation was caused by the forward bulging of the anterior lens surface, rather than by anterior shifting of lens position in either young or presbyopic subjects.

Anterior segment parameters using Pentacam and prediction of corneal endothelial cell loss after cataract surgery

Purpose

We evaluated various preoperative anterior segment parameters measured with a Pentacam rotating Scheimpflug camera and compared them with those of conventional methods. We also evaluated the effect of different parameters on corneal endothelial cells after cataract surgery.

Methods

Pentacam examination was performed in 88 eyes from 88 patients to evaluate central anterior chamber depth (ACD_pentacam), nuclear density (Densitometry_pentacam), anterior chamber volume (ACV), and lens thickness (LT_pentacam). We compared values of ACD_pentacam with those of ultrasound (ACD_sono) and also compared Densitometry_pentacam values with those of Lens Opacities Classification System (LOCS III) classification. We evaluated the effect of the following preoperative values measured with Pentacam on postoperative endothelial cell loss: pupil size measured both preoperatively and before capsulorrhexsis (Pupil_CCC), amount of viscoelastics, and LT measured by ultrasound (LT_sono).

Results

A significant concordance was found between the two grading methods of nuclear opacity: Densitometry_pentacam and LOCS III classification (τ_b = 0.414, p = 0.000). We also found a positive correlation between ACD_pentacam and ACD_sono (r = 0.823, p = 0.000) and between ACD_pentacam and ACV (r = 0.650, p = 0.000). There were significant differences between the results of LT_pentacam and LT_sono. The final regression model identified Densitometry_pentacam, viscoelastics and Pupil_CCC as independent predictors of decreased postoperative corneal endothelial cell density (CD) at postoperative day 3, and Densitometry_pentacam, viscoelastics, and ACV as independent predictors of decreased CD two months postoperatively (p<0.05).

Conclusions

Good agreement was found between all results obtained with the Pentacam and conventional methods except LT. Analyzing anterior chamber parameters preoperatively using Pentacam could be helpful to predict postoperative endothelial cell loss.

Repeatability and validity of lens densitometry measured with Scheimpflug imaging

PURPOSE

To assess the repeatability and validity of lens densitometry derived from the Pentacam Scheimpflug imaging system.

SETTING

Eye Clinic, Queensland University of Technology, Brisbane, Australia.

METHODS

This prospective cross-sectional study evaluated 1 eye of subjects with or without cataract. Scheimpflug measurements and slitlamp and retroillumination photographs were taken through a dilated pupil. Lenses were graded with the Lens Opacities Classification System III. Intraobserver and interobserver reliability of 3 observers performing 3 repeated Scheimpflug lens densitometry measurements each was assessed. Three lens densitometry metrics were evaluated: linear, for which a line was drawn through the visual axis and a mean lens densitometry value given; peak, which is the point at which lens densitometry is greatest on the densitogram; 3-dimensional (3D), in which a fixed, circular 3.0 mm area of the lens is selected and a mean lens densitometry value given. Bland and Altman analysis of repeatability for multiple measures was applied; results were reported as the repeatability coefficient and relative repeatability (RR).

RESULTS

Twenty eyes were evaluated. Repeatability was high. Overall, interobserver repeatability was marginally lower than intraobserver repeatability. The peak was the least reliable metric (RR 37.31%) and 3D, the most reliable (RR 5.88%). Intraobserver and interobserver lens densitometry values in the cataract group were slightly less repeatable than in the noncataract group.

CONCLUSION

The intraobserver and interobserver repeatability of Scheimpflug lens densitometry was high in eyes with cataract and eyes without cataract, which supports the use of automated lens density scoring using the Scheimpflug system evaluated in the study.

Clinical application of a Scheimpflug system for lens density measurements in phacoemulsification

PURPOSE

To evaluate the relationship between lens density measured using the Pentacam Scheimpflug system and phacodynamics (phacoemulsification time, phacoemulsification energy, and balanced salt solution [BSS] use) in patients with age-related nuclear cataract.

SETTING

Department of Ophthalmology and Visual Science, Kangnam St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.

METHODS

This prospective observer-masked study was of eyes with age-related nuclear cataract. Objective lens density (0 to 100 points) was determined using the Scheimpflug system. Subjective grading was by the Lens Opacities Classification System III (LOCS III). The correlations between lens density values and phacoemulsification time, phacoemulsification energy, and BSS use were analyzed prospectively.

RESULTS

Fifty-three patients (60 eyes) were evaluated. The mean Scheimpflug-measured lens nuclear density was 14.71 +/- 6.12 (SD). There was a positive linear correlation between the Scheimpflug-measured lens nuclear density and the LOCS III grading scores for nuclear opalescence (NO) and nuclear color (NC) (r = 0.734 and 0.719, respectively; both P<.05). The Scheimpflug-measured lens nuclear density correlated with torsional amplitude, time, and cumulated dissipated energy (CDE) (P<.05), but not with BSS use (P = .195). The CDE was more strongly correlated with Scheimpflug-measured lens nuclear density (r = 0.797) than with LOCS III NO or NC scores (r = 0.614 and r = 0.637, respectively).

CONCLUSIONS

Scheimpflug-measured lens nuclear density correlated with phacoemulsification time and energy. The Scheimpflug system enabled quantitative cataract grading and may help predict phacodynamics in cataract surgery.

Radiation cataractogenesis: a review of recent studies

The lens of the eye is recognized as one of the most radiosensitive tissues in the human body, and it is known that cataracts can be induced by acute doses of less than 2 Gy of low-LET ionizing radiation and less than 5 Gy of protracted radiation. Although much work has been carried out in this area, the exact mechanisms of radiation cataractogenesis are still not fully understood. In particular, the question of the threshold dose for cataract development is not resolved. Cataracts have been classified as a deterministic effect of radiation exposure with a threshold of approximately 2 Gy. Here we review the combined results of recent mechanistic and human studies regarding induction of cataracts by ionizing radiation. These studies indicate that the threshold for cataract development is certainly less than was previously estimated, of the order of 0.5 Gy, or that radiation cataractogenesis may in fact be more accurately described by a linear, no-threshold model.

Correlation of nuclear cataract lens density using Scheimpflug images with Lens Opacities Classification System III and visual function

PURPOSE

To calculate the average lens density (ALD) and nuclear lens density (NLD) using Scheimpflug images and to determine their correlation with logarithmic minimal angle resolution (logMAR) best-corrected visual acuity (BCVA), contrast sensitivity (CS), and lens grading based on the Lens Opacities Classification System (LOCS) III.

DESIGN

Cross-sectional observational study.

PARTICIPANTS

One hundred ten patients with age-related nuclear cataract.

METHODS

The logMAR BCVA was recorded using Early Treatment Diabetic Retinopathy Study charts and photopic contrast-sensitivity using CSV-1000LV (Vector Vision, Greeneville, OH). Fifty Scheimpflug images (Pentacam, Oculus, Germany) covering 360 degrees of the lens were obtained for 1 eye of each patient after dilation. All Scheimpflug images were exported to ImageJ software (NIH, Bethesda, MD) for analysis wherein the ALD and NLD (using a mask applied to the lens nuclear area) were calculated in pixel-intensity units. Repeatability was determined using coefficient of variation (CoV) and intraclass correlation coefficient (ICC). Lens opacity on slit-lamp images was graded using LOCS III for nuclear opalescence (NO) and nuclear color (NC).

MAIN OUTCOME MEASURES

We evaluated ALD and NLD on Scheimpflug images and their correlation with NO and NC LOCS III grading, BCVA, and photopic CS.

RESULTS

The ICC for ALD and NLD were 0.983 and 0.99, respectively; the CoV were 3.92+/-1.76% and 2.57+/-0.74%, respectively. The ALD correlated with NO (r = .774; P<0.001), NC (r = .732; P<0.001), BCVA (r = 0.696; P<0.001), and CS at 3 cycles per degree CPD (P = 0.011), 6, 12, and 18 CPD (P<0.001). The NLD correlated with NO (r = .859; P<0.001), NC (r = .81; P<0.001), BCVA (r = .760; P<0.001), CS at 3 CPD (P = 0.002), 6, 12, and 18 CPD (P<0.001). The NLD had a significantly stronger correlation with BCVA (P<0.05), NO (P<0.01), NC (P<0.01), and CS at 6 CPD (P<0.01) and 12 CPD (P<0.005) compared with ALD.

CONCLUSIONS

Repeatable 360 degrees lens density measurements were obtained using Scheimpflug imaging. A stronger correlation was observed between NLD and LOCS III grading, BCVA, and photopic CS than with ALD. The NLD is an objective and repeatable method for assessment of lens density, which could be helpful in longitudinal studies monitoring nuclear cataracts.