Patricia M. Khu

Evaluation of lens opacities classification system III applied at the slitlamp.

The Lens Opacities Classification Systems (LOCS III) was developed and standardized using photograding. The purpose of this study was to assess the validity of LOCS III at the slitlamp and to compare slitlamp with photograding. To do so, two independent observers graded cataract at the slitlamp and in photographs from two sets of patients; the first set consisted of 205 eyes (193 acceptable photographs) and the second set of 51 eyes (51 photographs). The 95% tolerance limits (TL) for grading at the slitlamp ranged from 0.9 to 1.8 for the first set and 0.6 to 1.2 for the second (intraclass correlation coefficients 0.79 to 0.91 vs. 0.70 to 0.97, respectively). Specifically, there was a significant decrease in 95% TL for cortical and nuclear color. For the first set of photograding, the 95% TL were 0.3 to 0.6 between the two observers and 0.6 to 0.8 for the same observer at two different sessions. Similar results were found for photograding the second set. The 95% TL for comparing slitlamp and photograding were generally > 1.0. The results suggest that (1) LOCS III at the slitlamp has 95% TL only slightly worse than those for LOCS III photogradings; (2) LOCS III slitlamp grading for cortical and nuclear color improves with practice; and (3) the slitlamp and photographic gradings cannot be used interchangeably.

Quantitating Cataract and Nuclear Brunescence, The Harvard and LOCS Systems

Subjective and objective systems are used to quantify cataract at The Center for Clinical Cataract Research. We have described each system and its use, presented data on reproducibility and validity, and for objective systems, demonstrated the correlation to the subjective grade of the cataract as defined by the Lens Opacities Classification Systems, Versions II and III (LOCS II and III). The subjective systems are used to classify nuclear color, nuclear opalescence, cortical cataract, and posterior subcapsular cataract. Reported kappa scores for LOCS II range from 0.85 to 1.0. Intraclass correlation coefficients for LOCS III (r1) range from 0.67 to 0.94. The computerized objective system are: (1) fast spectral scanning colorimetry (FSSC) for assessment of nuclear color (r1 = 0.96 to 0.98); (2) nuclear mean density (NMD) for assessment of nuclear opalescence (r1 = 0.97); and (3) percent area opacity (anterior = a; posterior = p) (OPAC-a and OPAC-p) for assessment of cortical and posterior subcapsular cataract (r1 = 0.92 to 0.96).

Contrast sensitivity and visual acuity in patients with early cataracts

ABSTRACT In a population of 188 nondiabetic patients with early cataracts or nuclear brunescence, we assessed the degree to which contrast sensitivity function (CSF) provided more information about a patients visual disability than high contrast visual acuity measurements. Data collected included LOCS II cataract classification, Bailey‐Lovie visual acuity (LogMAR score), Lotmar interferometric visual acuity (LI VA), and distance contrast sensitivity function (CSF) using the Vistech 6500. Generalized least squares regression models in which CS was the dependent variable and either LogMAR score or LI VA was among the independent variables were used to ascertain whether CSF provided additional information about visual disability to that provided by LogMAR score or LI VA. Contrast sensitivity function was decreased only by nuclear opalescence at high frequencies (12 to 18 cpd); for all other cataract types and nuclear color, CSF testing provided no more information about cataract‐related visual loss than LI VA or LogMAR score. Measurement of CSF using the Vistech 6500 system in patients with early cataracts provides information on visual dysfunction beyond that provided by LogMAR score or LI VA only in patients with nuclear opalescence, and that may not be clinically significant.

Loss of contrast sensitivity in diabetic patients with LOCS II classified cataracts.

Contrast sensitivity function (CSF) was assessed in a population of diabetics with moderate cataracts to determine if CSF testing provides more information about visual dysfunction than Snellen or Lotmar interferometric visual acuity. With the Lens Opacities Classification Systems Version II (LOCS II) of cataract classification it was possible to grade accurately the type and severity of cataract and nuclear brunescence. The presence of statistically significant relationships between increasing LOCS II classification (worsening cataract) and diminished function, even when the regression model was controlled for Snellen visual acuity, supports the thesis that CSF measurements do provide more information about cataract related visual loss than Snellen acuity alone. Statistically significant (p < or = 0.05) relationships existed between different morphological types of cataract, nuclear colour, and CSF at specific frequencies. The frequencies affected differed with cataract type or nuclear colour, and with distance and near CSF.

New Method of Measuring Nuclear Cataract in Color Scheimpflug Photographs

Based on the differential equation, a new method of measuring nuclear cataract in color Scheimpflug photographs was introduced. The densitometries for red, green and blue color were conducted simultaneously along the anteroposterior axis of the lens within the nuclear region. The 3 color components were subtracted from each other, yielding blue-red, green-red and blue-green curves which were linear within the nuclear region. The tangent values were calculated from the curves that correlate well with the degrees of nuclear cataract.

Subjective (LOCS II) versus Objective (BGS) Measures of Cortical and Subcapsular Cataracts in Retroillumination Photographs

96 black-and-white Neitz retroillumination photographs were graded subjectively using the Lens Opacities Classification System Version II (LOCS II). They were also measured objectively using the background subtraction (BGS) analysis. Subjective and objective BGS gradings were compared and showed good agreement (kappa = 0.78 for cortical and 0.78 for posterior subcapsular cataracts) and good correlation (correlation coefficient = 0.82 for cortical and 0.84 for posterior subcapsular cataracts; Spearman rank analysis).

Effect of Cataract Type and Severity on Lens Grading

Two sets of lens photogradings were used to investigate the effect of cataract type and severity on the intra- and interob-server agreement between two graders using the Lens Opacities Classification System III (LOCS III). The first set consisted of 193 eyes, largely of mild-to-moderate opacities for all cataract types. The second set consisted of a similar number of cataracts in each group subdivided into mild, moderate, and severe, a total of 159 lens photographs. Intraclass correlation coefficient (r1) was used to measure the intra- and interobserver reproducibility and 95% tolerance limit the intra- and interobserver variability. Results showed that more variability was seen in intra- and interobserver agreement when grading increasing posterior subcapsular opacities. Decreased reproducibility and increased variability in interobserver agreement were seen in increasing cortical gradings, and decreased reproducibility in interobserver agreement in more severe nuclear opacities. No difference was seen in nuclear color gradings. The results suggest that the effect of cataract severity on interobserver agreement should be taken into consideration in longitudinal studies requiring several photograders.