Morphology of and visual performance with posterior subcapsular cataract Abhay R. Vasavada, MS, FRCS, Praveen R. Mamidipudi, DOMS, Preeti S. Sharma, MS Purpose: To study the prevalence and clinical profile of etiologically diverse posterior subcapsular cataracts (PSCs) and their effect on visual performance. Setting: Iladevi Cataract & IOL Research Centre, Ahmedabad, India. Methods: This prospective observational study comprised 160 eyes of 100 consecutive patients with PSC. Exclusion criteria included cortical opacities, cataract other than PSC, and a nondilating pupil. Lenticular changes such as gross appearance, density of opacity in the central 7.0 mm, and location and approximate area of cataract involvement were noted. The uncorrected distance and near acuities, best corrected visual acuity (BCVA), contrast sensitivity with BCVA, and history of glare were recorded Results: Sixty patients had bilateral PSC. The most prevalent cataracts were of unknown etiology (32.5%). The most common coexisting disease or factor was atopy (30.6%). Others were myopia, steroid use, diabetes, uveitis, retinitis pigmentosa (RP), glaucoma, and trauma. Most patients (47.0%) were 41 to 50 years old. The PSC was vacuolar in 45.0% of eyes, solid in 15.6%, and mixed in 39.4%. Vacuolar PSC was the most common type in the myopia, diabetes, RP, and trauma groups. Solid PSC was seen with myopia, diabetes, and glaucoma. Mixed PSC was the most common type in the steroid, atopy, uveitis, and idiopathic groups. Eighty-seven percent of patients had reduced visual acuity; 76%, glare; and 46%, decreased contrast sensitivity. More eyes with vacuolar PSC had decreased visual acuity and contrast sensitivity, followed by eyes with solid PSC and eyes with mixed PSC. Conclusions: Most PSCs were of unknown etiology; a significant number of eyes had more than 1 etiology. Vacuolar PSC was the most common type, with more eyes in this group having significantly reduced visual acuity and contrast sensitivity. Specific morphological patterns occurred with some conditions (eg, RP, myopia, diabetes). J Cataract Refract Surg 2004; 30:2097–2104 2004 ASCRS and ESCRS
C
ataract falls into 3 basic morphologic categories1: cortical, nuclear, and posterior subcapsular (PSC). Posterior subcapsular cataracts in persons with neurodermatitis or atopy usually comprise dense plaque in
Accepted for publication February 13, 2004. From Iladevi Cataract & IOL Research Centre, Ahmedabad, India. None of the authors has a financial or proprietary interest in any material or method mentioned. Reprint requests to Dr. Abhay R. Vasavada, Iladevi Cataract & IOL Research Centre, Gurukul Road, Memnagar, Ahmedabad 380 052, India. E-mail:
[email protected]. 2004 ASCRS and ESCRS Published by Elsevier Inc.
the anterior or posterior cortex and striae in the anterior cortex.2 Corticosteroid-induced cataracts are characteristically granular opacities that occupy the polar region of the posterior cortex, just within the posterior capsule.2 There is little information on the detailed morphology of PSCs of diverse etiologies. This paper describes the morphologic patterns of PSCs of different etiologies and their effect on visual performance.
Patients and Methods This prospective single observational study comprised 100 consecutive patients (160 eyes) with PSC presenting to 0886-3350/04/$–see front matter doi:10.1016/j.jcrs.2004.02.076
PSC: MORPHOLOGY AND VISUAL PERFORMANCE
the Iladevi Cataract & IOL Research Centre clinic from October 1, 1999, to June 30, 2000. Patients with PSC and a history of diseases and other factors that could lead to PSC (eg, atopy, diabetes mellitus, skin disorders, drug intake, ocular disease) were identified and included in the study. The presence of atopy was confirmed by factors such as personal and family history. Other skin disorders were confirmed by a dermatologist. Patients with cortical opacities, mixed cataract detected with the pupil dilated, nondilating pupils, and fully dilated pupils smaller than 7.0 mm were excluded from the study. All patients had a thorough slitlamp examination. Only patients who had PSC had further, detailed examination. Eyes were dilated with tropicamide drops 1% 3 times at 15-minute intervals or until the pupil was 7.0 mm or larger. This was followed by detailed slitlamp assessment of lenticular changes. A video camera attached to a Zeiss slitlamp was used to record the PSC’s location, the density within a 7.0 mm diameter circle of the lens, and the approximate area involved. The slitlamp beam was fixed at a width of 1.0 mm, height of 14.0 mm, and magnification of ⫻8 at 100% illumination. A fixation light offset by 15 degrees to the illuminating beam was used. This system allowed replication of results. The image was seen on the screen at ⫻20.5 magnification. Thus, a 7.0 mm diameter pupil measured through the slitlamp appeared to be 143.5 mm on the screen.
Area and Location of the Cataract A circle with a radius of 71.75 mm (7/2 ⫻ 20.5), or 7.175 cm, located approximately in the center of the lens on the screen was evaluated. The total area was divided into 6 concentric circle. Each circle was divided into 16 sectors; thereby, the area of the circle was divided into 96 equal parts. The number of segments with opacity was counted to calculate the approximate area of involvement. The area occupied by the cataract was calculated by the area off the screen, accounting for the magnification. The location of the cataract was determined by dividing the area of interest into 3 equal zones: central, midperipheral, and peripheral.
Classification and Density of PSC The PSCs were classified into 3 types according to clinical evaluation: vacuolar, solid (plaque like), and mixed. The density of the cataract was assessed subjectively and graded clinically on retroillumination as follows: 0 ⫽ no cataract; 1⫽ minimal/mild (bubble-like transparency); 2 ⫽ moderate (translucent); and 3 ⫽ severe (opaque).
Other Measurements A slitlamp examination of the anterior vitreous face was performed to determine whether there were fibrillar strands or vitreous degeneration in the form of a broken or intact vitreous face. The uncorrected distance and near visual acuities and 2098
Table 1. Age distribution. Age (Y)
Patients, n
21–30
8
31–40
16
41–50
47
51–60
22
61–70
7
best corrected visual acuity (BCVA) using Snellen and Jaeger charts were recorded, as was contrast sensitivity with BCVA using Cambridge low-contrast gratings. Also noted was whether the patient had a history of glare; no specific objective testing was done to elicit glare. The lens thickness and axial length were determined with an A-scan biometer.
Results Demographics Of the 160 eyes (100 patients), 79 were right and 81 were left. Sixty patients had bilateral PSCs. Only 1 eye of the remaining 40 patients was included in the study because the other eye was pseudophakic, lost, or had mixed cataract. Sixty-four percent of patients were men. Table 1 shows the patients grouped into 10-year age categories. The 41- to 50-year group had the most patients (47) and the youngest (21 to 30 years) and oldest (61 to 70 years) groups, the fewest. Type, Distribution, and Extent of PSC Seventy-two eyes (45%) had vacuolar PSC, 25 (16%) had solid PSC, and 63 (39%) had mixed PSC. Vacuolar PSC was the most common type in cases of myopia, diabetes, retinitis pigmentosa (RP), and trauma and mixed PSC, in cases of steroid, atopy, uveitis, and idiopathic etiology. Solid PSC was seen in cases of myopia, diabetes, and glaucoma. The central zone was involved in all 160 eyes, the central and midperipheral zones in 91 eyes (57%), and all 3 zones in 48 eyes (30%). Etiology The most prevalent cataract (52 eyes) was of unknown etiology (Table 2). The most common coexisting disease or factor that could predispose to PSC was atopy (49 eyes). This was determined by tabulating and dividing patients into categories, taking 1 inciting factor
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Table 2. Etiology of cataracts. Atopy Personal & Parameter Idiopathic Dermatitis Family History Asthma Myopia Steroid Diabetes Uveitis RP Glaucoma Trauma Patients, n
32
15
10
6
22
20
14
10
4
3
1
Eyes, n
52
25
15
9
32
32
22
15
8
5
1
n ⫽ number; RP ⫽ retinitis pigmentosa
(ie, atopy) common to the entire group. The other groups are shown in Table 2. Unknown (Idiopathic). In this group, the PSC was mixed in 40 eyes, vacuolar in 8 eyes, and solid in 4 eyes. Most cataracts were small, of grade 2 or 3 opacity, and densest in the central area (Figure 1). The cataract was in the central zone in 42 eyes, midperipheral zone in 6 eyes, and peripheral zone in 4 eyes. The pattern of the opacities had no distinct shape or distribution. The axial length was less than 24.0 mm in 48 eyes, and the mean lens thickness was 4.5 mm (range 3.5 to 5.0 mm). Six eyes had anterior vitreous degeneration. Atopy. In this group, the PSC was mixed in 32 eyes, vacuolar in 10 eyes, and solid in 7 eyes. In 20 eyes, the cataracts had a dense center (grade 3) surrounded by grade 1 or 2 opacities that, in general, had a petalloidor star-shaped pattern (Figure 2). The cataract was in the central zone in 44 eyes and midperipheral zone in 5 eyes. The axial length was less than 24.0 mm in 12 eyes. Myopia. In this group, the PSC was vacuolar in 25 eyes, solid in 5 eyes, and mixed in 5 eyes. The cataracts occupied a small area of the lens. The cataract was in
the central zone in 31 eyes and midperipheral zone in 1 eye. The well-developed cataracts (22 eyes) had a spidery configuration with a main central opacity and radiating thin limbs extending toward the periphery (Figure 3). The central opacities comprised a combination of all 3 grades of opacities and were peppered with shiny dots. The opacities in the limbs appeared as transparent to translucent loosely attached bubbles. The early forms of cataract (10 eyes) appeared as loosely attached shiny bubbles in the posterior subcapsular region that were discretely scattered or linearly arranged. The axial length was greater than 25.0 mm in 21 eyes, and the lens was thicker than 4.6 mm in 8 eyes. Twenty eyes had signs of anterior vitreous degeneration. Steroid Induced. In this group, the PSC was mixed in 18 eyes, vacuolar in 11 eyes, and solid in 3 eyes. The cataract was in the midperipheral zone in 10 eyes, central zone in 8 eyes, and peripheral zone in 4 eyes. Twentyfour eyes had eccentric PSC and denser centers with interspersed vacuoles, which together formed a granular conglomerate (Figure 4). These were surrounded by
Figure 1. (Vasavada) A mixed, idiopathic PSC with different
Figure 2. (Vasavada) An atopic PSC with a pettaloid- or star-
grades of opacities.
shaped pattern.
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Figure 3. (Vasavada) A PSC in the myopia group with a spider-
Figure 4. (Vasavada) A steroid-induced PSC with an eccen-
like configuration and radiating limbs.
tric position and well-demarcated margins forming a granular conglomerate.
grade 1 and 2 opacities. The margins, which were usually well defined, consisted mainly of grade 3 opacities. The axial length was less than 24.0 mm in 24 eyes. Four eyes had anterior vitreous degeneration. Diabetes Mellitus. In this group, the PSC was mixed in 14 eyes, vacuolar in 7 eyes, and solid in 1 eye. The cataract was in the central zone in 17 eyes, midperipheral zone in 3 eyes, and peripheral zone in 2 eyes. Twelve cataracts resembled a rosette, with the leaves formed by sutures. The sutures served as a backbone from which streak-like, fine, feathery opacities radiated toward the periphery (Figure 5). All eyes had an axial length greater than 25.0 mm and a lens thickness from 4.1 to 4.5 mm. Four eyes had signs of anterior vitreous degeneration.
Intraocular Inflammation. In this group, 9 eyes had pars planitis and 6 had anterior uveitis. The cataract was vacuolar in 7 eyes and mixed in 8 eyes. The cataract was in the central zone in 11 eyes, midperipheral zone in 2 eyes, and peripheral zone in 2 eyes. The cataracts had dense centers surrounded by lighter opacities (Figure 6). In the vacuolar group, all 3 grades of opacities were diffusely spread over the posterior subcapsular region. Eyes with mixed PSC had grade 1 and 2 opacities, with some having dark borders. The axial length and lens thickness were consistent with the patient’s age. Eight eyes had anterior vitreous degeneration. Retinitis Pigmentosa. In this group, the cataract was vacuolar in 7 eyes and mixed in 1 eye. The cataract
Figure 5. (Vasavada) A PSC in the diabetes mellitus group forms
Figure 6. (Vasavada) A mixed PSC in the intraocular inflammation
a rosette from which streak-like, feathery opacities radiate.
group is diffusely spread over the posterior capsule.
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Figure 7. (Vasavada) A PSC in the RP group with an amoeboid
Figure 8. (Vasavada) Visual complaints, overall (dotted bars) and
pattern and projections.
within 6 months (black bars) of presentation (DOM ⫽ diminuation of vision; Red. CS ⫽ reduced contrast sensitivity).
was in the central zone in all 8 eyes. In 7 eyes, the cataract appeared to be glazed and had an amoeboid shape with the body centrally located; the projections occupied the midperiphery in most cases and the periphery in the other cases (Figure 7). The opacities were grade 1 or 2. Four eyes had an axial length from 24.00 to 24.99 mm, and 6 had a lens thickness between 3.6 mm and 4.0 mm. Five eyes had anterior vitreous degeneration. Antiglaucoma Medication and Surgery. In this group, the cataract was vacuolar in 3 eyes and mixed in 2 eyes. The cataracts were small and limited to the central zone. The distribution of the opacities had no specific pattern. The axial length was less than 24.0 mm and the lens thickness between 4.1 mm and 5.0 mm in all eyes. One eye had signs of anterior vitreous degeneration. Trauma. The 1 eye with traumatic cataract had a mixed PSC. Most opacities were grade 1 and a few, grade 3. The cataract was in the central zone. The gross morphologic picture was of an asymmetric rosette occupying the posterior subcapsular region, with a backbone of suture lines from which feathery opacities radiated.
Thirty eyes had a BCVA of 20/80 or worse; 100 eyes, between 20/60 and 20/30; and 30 eyes, 20/20 or better. Most patients in all groups had a BCVA between 20/30 and 20/60. The idiopathic group had the most eyes (12) with a BCVA of 20/20 or better. Distance acuity was worst in the RP and trauma groups. Thirtythree eyes had a best corrected near acuity of N24 or worse; 46 eyes, between N18 and N10; and 81 eyes, N8 or better. Although reduced contrast sensitivity was not a top visual complaint, most patients in all cataract categories had a significant reduction in contrast sensitivity; the RP and trauma groups had the worst sensitivity. The best visual acuity and least reduction in contrast were in eyes with vacuolar PSC, followed by solid PSC and mixed PSC.
Visual Acuity and Contrast Sensitivity Of the 100 patients, 87 reported diminished visual acuity, with 36 presenting within 6 months of the complaint. Seventy-six patients reported glare, with 33 presenting within 6 months. Forty-six patients had reduced contrast sensitivity, with 21 reporting within 6 months (Figure 8). In all patients, decreased vision was the chief complaint, followed by glare.
Discussion Posterior subcapsular cataracts are characterized by dysplasia of the equatorial epithelial proliferating zone. Morphologically, they appear as a proliferation of dysplastic bladder-like fibers or Wedl cells in the meridional region of the lens that subsequently migrate and aggregate at the posterior pole.3 The etiology of PSC is varied. However, the resemblance between certain types of PSC is sufficient to allow pathological differentiation merely by examining the lens. For example, traumatic cataracts commonly follow the suture lines in a feather-like arrangement.4
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Forman and coauthors5 suggest that genetic factors are important determinants in PSC formation. Laredo and coauthors 6 and Rooklin et al.7 suggest that individual and ethnic characteristics predispose to PSC; both studies found that Hispanic people are more predisposed to PSC than white or black people.6,7 In our study, multiple risk factors were responsible for the pathological conditions of the lens; hence, the cataract was obviously the end result of all those factors. Such cataracts are morphologically different from those with only 1 known causative factor. To simplify categorization, we grouped patients with a risk factor common to all, such as atopy, and studied the clinical profile of the cataracts in the various categories. Etiology Unknown (Idiopathic). All patients with a PSC of unknown etiology were younger than 50 years. None had a significant family history of cataract, although some of the cataracts could have been genetic or presenile in origin. Atopy. Two types of cataracts have been reported in atopic patients, complicated and shield-like anterior plaque.8 Atopic cataract occurs more often in young people.9 In our study, 58.2% patients with atopic cataracts were younger than 50 years. Myopia. Among the categories with known etiological factors, myopia is the largest. Studies show that subcapsular cataract is the first type of cataract to appear,10 presenting in patients between 41 years and 44 years. In our study, the largest proportion of patients was in the 41- to 50-year age group. Our finding of a high incidence of PSC in young patients is similar to the findings of Brown and Hill.10 The large proportion of women in the myopia group in our study reflects the findings in a study by Perkins.11 In myopic patients, Perkins11 recorded a higher incidence of PSC (40%), while Brown and Hill10 report an incidence of 24%. Other studies12,13 report a lower incidence of PSC (1.8% to 6.0%). The association between high myopia and cataract is well established. Patients with myopia have a higher probability of developing nuclear sclerotic cataract, with 1 study reporting an incidence of 41%.10 Cross-sectional data indicate an association between myopia and nuclear cataract10,14–16 and PSC.14 However, 1 of these studies14 found a stronger association between baseline refractive status and the incidence of PSC. The 2102
presence of any type of myopia more than doubles the risk for PSC. Lim and coauthors14 conclude that earlyonset myopia (before age 20 years) may be a strong and independent risk factor for PSC. Steroid Induced. The appearance of steroid-induced cataracts in our series was similar to that reported by Oglesby and coauthors.17 Greiner and Chylack18 observed well-demarcated margins similar to those in our study. We did not find a difference in the morphology of steroid-induced cataracts with the use of systemic or local steroids. Other studies report similar results.18 Diabetes Mellitus. Cataracts in diabetic patients have been reported to be nuclear, cortical spoke, and posterior subcapsular.19 However, in a case-control study of lens opacity,19 diabetes increased the risk for posterior subcapsular, cortical, and mixed cataract. Prchal and coauthors20 found that PSC was specifically associated with diabetes. Typical features of cataract in diabetes are posterior subcapsular, cortical snowflakes, polychromatic opacities, and vacuoles.21 We did not see a polychromatic luster to any cataract in this group. Intraocular Inflammation (Uveitis). Cataract development in most cases of uveitis is the result of several factors including the inflammation itself and the use of steroids.22 Smith and coauthors23 report that in 40% of patients with pars planitis, lens opacities first developed in the posterior subcapsular region. In our study, the cataracts in this group were diffusely spread over the posterior subcapsular region. Smith and coauthors also observed this pattern in patients with chronic iridocyclitis. Retinitis Pigmentosa. The overall frequency of PSC associated with progressive panretinal degeneration has been reported to be 41% and to be most common in autosomal dominant RP.24 Pruett25 found cataract in 46.4% of 384 eyes with typical RP and a mean age of 39.1 years; 93.6% were PSC. He ascribed the increased incidence of cataract in these eyes to age. Dilley and coauthors26 and Heckenlively27 point out that the cataract in RP is focal in nature and less opacified. Similarly, we also found the cataracts were less opacified in this group. It has also been reported that cataractous changes in cases of RP typically occur in the posterior subcapsular region.28–31 Antiglaucoma Medication and Surgery and Trauma. Cataracts in these groups had no characteristic features.
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Visual Acuity and Contrast Sensitivity Visual acuity has traditionally been the primary visual function test used to determine the need for cataract surgery.33 The degree of visual impairment depends on the extent of PSC formation. The assessment of a patient’s visual disability is not easy.32 In our study, most eyes in all PSC groups (ie, vacuolar, solid, and mixed) had a BCVA between 20/30 and 20/60 and good near vision (N8 or better). Few studies have documented that visual acuity loss proportionately correlates with nuclear and cortical cataract but causes disproportionately more disability in patients with PSC.33,34 We attribute the poor performance in RP, glaucoma, diabetes, and trauma to the presence of some retinal pathology. In our study, the primary complaint of patients was decreased vision, not glare. This is interesting because even minor degrees of cataract cause glare by forward scattering of light.35 Elliott and coauthors36 documented that glare disability is more prelevant in eyes with PSC than in eyes with nuclear and cortical cataract. Although reduced contrast sensitivity was not a main presenting complaint in our study, examinations showed it was significantly decreased. Although all cataracts lower contrast sensitivity, PSCs decrease it the most.35 In our study, visual acuity and contrast sensitivity were lower in eyes with vacuolar PSC than in eyes with solid PSC. Cheng et al.37 found worse visual acuity and contrast sensitivity in eyes with the pearl type of posterior capsule opacification (PCO) than in eyes with the solid (fibrous) type of PCO. In a review of PCO, Apple and coauthors38 documented that the equatorial cells of the germinative zone tend to migrate along the posterior capsule to form PSC and pearl-type PCO. We speculate that the origins of PSC and PCO are the same; thus, one can hypothesize that the mechanisms that affect vision and contrast sensitivity are similar. Axial length and lens thickness were within normal limits and were consistent with age in all groups in our study. In some cases, it was very difficult to differentiate the specific etiology of PSC. To simplify categorization of patients with more than 1 risk factor, we based the differentiation on the morphologic characterization of the PSC. For example, in patients with uveitis on steroid treatment, the cataract was categorized as uveitic cataract if the PSC was diffuse in the posterior subcapsular region. However, if the patient had granular conglomer-
ate PSC typical of steroid use, the cataract was categorized as steroid induced. A major limitation of our study was that many patients had more than 1 risk factor for PSC. Thus, we could not make a sufficiently accurate morphologic characterization. The size of the pupil after instillation of dilating drops was beyond our control, which could have affected the amount of reflected light, altering the subjective perception of cataract density. In addition, anterior vitreous degeneration was subjectively assessed and thus could have been inaccurate. The sample size was also too small to establish the definitive pattern and characterization of PSC in all categories. In conclusion, PSCs of unknown etiology were the most prevalent in our study, and many eyes had more than 1 etiology. Vacuolar PSCs were the most common. Specific morphologic patterns were seen in patients with RP, myopia, and diabetes.
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