| | Clinician versus potential acuity test predictions of visual outcome after cataract surgeryAbstract BackgroundThe aim of this study was to compare the ability of potential vision tests and clinical judgement to predict postoperative visual acuity after uneventful cataract surgery. MethodsSixty-two subjects (median, 74.5 years) were included in the study. Preoperative measurements included a clinical judgement prediction (based on case history and ocular examination alone), 2 super-illuminated pinhole techniques (distance and near), Potential Acuity Meter and interferometer. Postoperative visual acuity was used as the outcome measure to evaluate the accuracy of the preoperative predictions. ResultsSubjects were categorized as follows: (a) moderate cataract (N = 25); (b) moderate cataract and comorbidity (N = 18), and (c) advanced cataract (N = 19). Preoperative predictions within 2 lines of the postoperative visual acuity were as follows (a, b, and c respectively): clinical judgement (92%, 72%, 58%), super-illuminated pinhole distance (96%, 100%, 21%), super-illuminated pinhole near (92%, 78%, 26%), Potential Acuity Meter (72%, 67%, 21%), and interferometer (56%, 61%, 37%). ConclusionsBased on the preoperative predictions above, none of the potential vision tests was useful compared with the clinical judgement in the advanced cataract group. The super-illuminated pinhole (distance) provided additional information beyond clinical judgement in the moderate cataract subgroup. The Potential Acuity Meter and interferometer were inaccurate even in the presence of moderate cataract, and this and other recent findings suggest they should no longer be considered adequate for potential vision assessment. Clinicians usually predict the likely visual outcome to be achieved after cataract surgery based on history and ocular examination. However, it is not always easy to establish the contribution of ocular comorbidity to the subject's decreased sight, particularly when both cataract and retinal/neural disease coexist. Schein et al. reported that 63% of subjects predicted by ophthalmologic judgement to obtain a visual acuity (VA) of 20/40 or worse after cataract surgery (the level at which surgery is often considered to be “unsuccessful”),1 actually achieved a VA of 20/30 or better.2 Conversely, overestimation of the visual outcome will undoubtedly result in patient disappointment and should be avoided whenever possible. Mavroforou and Michalodimitrakis3 reported that the most common cause of patient litigation after cataract surgery (in the United States) was poor visual outcome in patients who had cataract and macular disease before cataract surgery. Potential vision tests (PVTs) were developed initially in the early 1980s in an attempt to improve the prediction of the visual performance after cataract surgery.4, 5 However, a major review conducted by the Agency for Health Care Policy and Research in 1993 concluded that there was insufficient evidence to establish whether PVTs increased the accuracy of the preoperative visual outcome prediction over and above history and ocular examination alone.6 As a result, clinical guidelines for the management of adult cataracts typically do not include PVTs as part of the preoperative ophthalmic evaluation.7, 8 Since this major review, several newer techniques have been developed.9, 10, 11, 12, 13, 14, 15, 16 In most cases, developers of PVTs have reported the value of newer techniques by comparing them with standard PVTs, such as the Potential Acuity Meter.12, 17 In addition, it is important to compare the results of PVTs with clinical judgement to determine whether they provide any additional useful information. Pinhole tests have been suggested previously as PVTs, given their resistance to moderate/dense cataract and sensitivity to macular disease.18 However, there is variation in the design of these tests ranging from the simple pinhole,19 to the illuminated pinhole at near12, 18, 20 and retro-illuminated pinhole at distance18, 10 (either at 3.2 m or at 1 m). Techniques have also varied in the type of VA charts used (including reversed contrast polarity,10, 18 Snellen12, 20 and logMAR designs10, 18) and the luminance levels used10, 20 (ranging from 1200 cd/m2 at 1 m to 1464 cd/m2 at 40 cm). Perhaps, not surprisingly, Potential Acuity Meter predictions were found to be more accurate than a conventional pinhole (81% versus 40% within 2 lines of best-corrected VA).19 The most likely explanation for this is the lack of decreased retinal illumination with the Potential Acuity Meter. Conversely, the predictions obtained with an illuminated pinhole at near were found to be more accurate than the Potential Acuity Meter for a range of cataract severities associated with a VA of better than 20/50 to worse than 20/200 (for example, 100% versus 47% for the 20/60 to 20/100 subgroup).12 This study was undertaken to compare the predictive ability of 2 versions of the super-illuminated pinhole (distance and near), the standard PVTs of the Potential Acuity Meter and interferometer, and clinical judgement based on history and ocular examination alone. The aim was to assess whether PVTs should be used in clinical practice to guide clinicians when there is uncertainty over the likely visual benefit of cataract surgery. Methods  Subjects An unselected sample of 74 subjects with age-related cataract was recruited from the cataract surgery waiting list at the Leeds Teaching Hospitals Trust, Eye Department, Leeds, United Kingdom. The exclusion criteria for this study included: •Subjects unable to speak English •Subjects with any physical or mental disability that would make it arduous to perform the tests •Upper age limit 90 years Three subjects had postoperative complications (including malposition of intraocular lens, intraocular lens exchange, and central retinal vein occlusion) and were excluded from the study because the preoperative predictions only apply to the visual result of an uneventful surgery. One subject decided not to undertake the surgical procedure, and 8 subjects were lost at the follow-up visit. Thus, 62 subjects (median age, 74.5 years; range, 50 to 89 years) were included in this study. A total of 38 subjects were listed for first-eye cataract surgery. Informed consent was obtained in each case, and the study gained approval from the Hospital Ethical Committee and followed the Declaration of Helsinki for research involving human subjects. The decision to perform cataract surgery was independent of the findings of this study. The 62 cataract subjects were divided into 3 groups as suggested by the Agency for Health Care Policy and Research:6 25 subjects with moderate cataract, 19 with advanced cataract, and 18 with moderate cataract and comorbid eye disease (see Table 1). Advanced cataract was defined as a Lens Opacity Classification System (LOCS) III21 grading for nuclear opalescence, nuclear color, and cortical opacity ≥5.0 and/or a posterior subcapsular opacity ≥3.0. All other cataracts listed for cataract surgery were classified as moderate and had nuclear opalescence ≥2.0 (range, 2.0 to 4.8), nuclear color ≥1.7 (range, 1.7 to 4.9), and/or cortical opacity ≥0.1 (range, 0.1 to 4.2), and/or a posterior subcapsular opacity ≥0.1 (range, 0.1 to 2.5). Subjects in the moderate cataract and comorbidity subgroup presented with the following ocular comorbidities: 9 with dry age-related macular degeneration, 6 with glaucoma, and 1 each with amblyopia, wet age-related macular degeneration, and an epiretinal membrane. All clinical diagnoses were made before surgical intervention and were confirmed postoperatively when a clear view of the fundus could be obtained. The clinical diagnoses of 8 subjects in the advanced cataract included dry age-related macular disease (3 cases), glaucoma (2 cases), amblyopia (2 cases) and epi-retinal membrane (1 case). The predictive ability of PVTs and clinical judgement in the advanced cataract only and advanced cataract with comorbidity subjects provided very similar results, and so the 2 groups were combined. | ∗ The mean of the predictions of postoperative VA was calculated for those subjects able to obtain a score with all PVTs (25 in the moderate, 17 in the moderate and comorbidity, and 13 in the advanced cataract subgroup). |
Procedures Subjects were examined a median of 3 weeks (range, 1 to 13 weeks) before surgical intervention and a median of 11 weeks (range, 10 to 20 weeks) after the cataract surgery. In the preoperative visit, PVT measurements were taken in a random order in the surgical eye after instillation of 1.0% tropicamide and 2.5% phenylephrine. The cataracts were graded using the Lens Opacity Classification System III.21 The LOCS III is a widely used classification system based on a set of standard photographs that are used as a reference to classify lens opacities at the slit lamp or in standardized lens photographs. Pupil dilation is required before LOCS III grading of the lens opacities. Grading using LOCS III involves the assessment and estimation of 4 features: nuclear opacification (i.e., brightness of scatter from the nuclear region), nuclear color (i.e., brunescence), and the extent of cortical and posterior subcapsular opacities. Nuclear opalescence and nuclear color are graded against 6 photographs on a decimal scale of 0.1 to 6.9 (in 0.1 steps), and cortical and posterior subcapsular opacity are each graded against 5 photographs on a scale of 0.1 to 5.9 (in 0.1 steps). The final LOCS III scale comprises the values given to each of these 4 features. Higher grade scores indicate greater severity of opacification. Subjective refraction, measurement of optimal VA, and slit lamp biomicroscopy of the fundus were performed in the pre- and postoperative visits. The postoperative VA represented the visual performance measurement against which the preoperative predictions could be compared. All PVT tests, pre- and postoperative VAS, and LOCS III assessment were made by one clinician. Information from PVT results was not available at the postoperative visits to limit potential bias. Distance VA was measured at 3.2 m under monocular conditions using an early treatment diabetic retinopathy study (ETDRS) logMAR chart (mean luminance 200 cd/m2), using a by-letter scoring system (0.02 log units per letter) and a termination rule of no letters called correctly on a line.22 The standard Potential Acuity Meter (Mentor Inc., Norwell, Massachusetts) procedure5 was used, and Snellen VA was determined as the smallest line at which the majority of letters were correctly identified. The Rodenstock Retinometer (Rodenstock, London, United Kingdom) was the interferometer used following the standard procedure23 with the gratings presented at 4 random orientations: horizontal, vertical, or oblique (45° to the right or the left). The highest spatial frequency at which the orientation of the fringe pattern could be correctly identified on 2 separate occasions gave a measure of the retinal/neural resolution. Oblique orientations were not used at threshold level. The super-illuminated pinhole at near was based on the test described by Melki et al.12 The test measured logMAR near VA using an ETDRS logMAR reading card held at 40 cm and illuminated by an external light source with the subject looking through a multiperforated pinhole (5 apertures of 1 mm). The external light source was moved by the examiner onto the section of the chart that was being read by the subject to give a luminance around 1,300 cd/m2. A super-illuminated pinhole at distance was also used. It consisted of measuring distance VA using a reversed polarity (white letters on a black background) ETDRS logMAR chart, with the subject looking through a multiperforated pinhole. The letters were seen by retroillumination (luminance 500 cd/m2) in a darkened room at a working distance of 3.2 m. To evaluate whether any of the PVTs provided information beyond that obtained by history and ocular examination alone, the PVT predictions were compared with a clinical judgement. The clinical judgement required the ophthalmologist to choose a predicted postoperative VA from a range, which followed a logMAR line progression (20/13, 20/17, 20/20, 20/25, 20/30, 20/40, 20/50, 20/60, 20/80, 20/100, 20/120, 20/160, 20/200, 20/250, and 20/400). The clinical judgement was performed prospectively by the ophthalmic surgeon undertaking the operation on the day of the surgery using information from the case history and ocular examination alone and with no input from the PVT results. In total, the clinical judgement was completed by 8 experienced cataract surgeons. Results Table 1 presents LOCS III categories and mean (±SD) data for age, pre- and postoperative VA and PVT, and clinical judgement predictions of postoperative VA in the 3 ocular subgroups. Only those subjects able to obtain a result with each of the PVT were included in the calculation of the means (±SD). The accuracy of the preoperative clinical judgement prediction was further compared with the 4 PVT predictions in terms of the percentage of subjects who achieved the postoperative VA result within 10 letters (i.e., 2 logMAR lines) of the predicted VA (see Table 2). Table 2 indicates that the predictive ability of all PVTs under investigation was severely diminished in the advanced cataract subgroup where clinical judgement offered the most accurate predictions. However, some of the PVTs provide predictions as good as or better than clinical judgement with moderate cataracts (see Table 2). The question is whether any PVT provides additional information beyond that provided by clinical judgement alone. Hierarchical stepwise regression analysis was used to assess the value of the 4 PVTs over and above clinical judgment in subjects with moderate cataract (with and without comorbidity). PVTs were used as predictors, and the postoperative VA measurement was used as the outcome variable. Clinical judgement was used as a forced first step, as it is the standard judgement of potential vision in the decision-making process for cataract surgery assessment. Subsequent to clinical judgement being forced as a first step, all PVTs were considered for inclusion into the regression model. Thus, for a PVT to be of clinical value, it must provide significant additional information about postoperative visual acuity beyond clinical judgement. Stepwise regression indicated that 46% of the postoperative VA data could be correctly predicted by clinical judgement alone. The hierarchical stepwise regression then indicated that 74% of the postoperative VA data could be predicted by the super-illuminated pinhole distance procedure combined with the clinical judgement. This means that super-illuminated pinhole distance provides extra information beyond clinical judgement to help predict the postoperative VA. However, the hierarchical stepwise regression then indicated that none of the other PVTs provided significant additional information beyond that provided by the clinical judgement alone in subjects with moderate cataract (with or without ocular comorbidity). Clinically, one may expect that PVTs may be used particularly in the preoperative assessment of cataract patients when clinicians suspect the presence of retinal/neural abnormalities. Thus, we repeated the hierarchical regression analysis in subjects with moderate cataract and ocular comorbidity only. In this scenario, the clinical judgement accounted for 52% of the postoperative VA data and clinical judgment, and super-illuminated pinhole distance accounted for 90% of the postoperative VA data. None of the others PVTs gave significant additional information to that provided by clinical judgment. Discussion A comparison of the means (±SD) obtained with the clinical judgement and the PVTs against the postoperative VA result indicates that with the exception of the interferometer, all PVTs and the clinical judgement underestimate the postoperative VA by less than 1.5 lines of letters in the presence of moderate cataract. Table 1 also indicates a larger underestimation of postoperative VA with all PVTs and the clinical judgement in the presence of advanced cataract. It is worth noting that, despite poor penetration of even moderate cataract, the interferometer increased its predictive ability in the presence of moderate cataract and comorbidity. It has been shown previously that the interferometer (and to a lesser extent Potential Acuity Meter) overestimate the visual result in the presence of clear media and macular abnormalities. This suggests that the overoptimistic predictions obtained in the presence of retinal abnormalities can compensate for the poor cataract penetration in some cases.18, 24, 25 Table 2 illustrates the percentage of preoperative PVT predictions and clinical judgement predictions that fell within 2 logMAR lines of the postoperative VA for the 62 subjects. It can be seen that the super-illuminated pinhole distance test provided a similar prediction to clinical judgement in the presence of moderate cataract and a better prediction than clinical judgement in the presence of moderate cataract with comorbidity. Hierarchical regression analysis confirmed that the super-illuminated pinhole distance test provided additional improvement in VA prediction compared with the clinical judgement alone in the moderate cataract and moderate cataract with comorbidity groups. This suggests that super-illuminated pinhole distance may be used as a confirmatory test when the clinician is uncertain of the contribution of retinal/neural disease to the existing disability in moderate cataracts. del Romo et al.10 also noted that an enhanced pinhole technique provided information beyond that obtained by clinical judgement in the presence of moderate cataract and ocular comorbidity in 12 subjects attending for first eye cataract surgery (83% versus 50% within 2 logMAR lines). In contrast, in the presence of advanced cataract, the predictions obtained with the clinical judgement were superior to those found using any of the PVTs (see Table 2). Previous investigators have also reported less accurate predictions in the presence of increasingly advanced media opacities with the Potential Acuity Meter,6, 26, 27 the laser interferometer,6, 23, 28, 29, 30 and enhanced pinhole techniques.12, 20 Recent reports suggest that the critical flicker/fusion frequency technique shows promising capabilities as a PVT in the presence of advanced cataract.10, 14, 31 In this investigation, the super-illuminated pinhole distance predictions were superior to the ones obtained with the super-illuminated pinhole near. The factors influencing the pinhole measurement are pinhole diameter, test chart illuminance, and the refractive status of the eye. Given that the same multiperforated pinhole and optimal refractive correction for the viewing distance was used in both tests, the chart illuminance and chart contrast polarity remain as the only factors responsible for the difference in predictive ability between the tests. External illumination of the letter chart may be less satisfactory than the retroillumination used in the super-illuminated pinhole distance test. It would also appear that a chart in reversed contrast polarity (white letters on a black background) is preferable. Ten subjects (6 moderate cataract and comorbidity and 4 advanced cataract) were predicted by clinical judgement to achieve a postoperative VA of 20/40 or worse (the level of outcome often deemed “unsuccessful”), but 50% of them achieved a postoperative VA of 20/30 or better after the surgery, similar to the findings of Schein et al.2 Underestimations of the retinal/neural function may result in surgical delays or even discouragement toward undertaking the surgery. The latter is supported by the high prevalence (∼19%) of patients found in low-vision clinic populations presenting with both age-related macular degeneration and cataracts.32 The clinical information provided by the VA measurements and clinical examination after first-eye surgery may have contributed to the correct clinical predictions for second-eye cataract in this study. A higher percentage of correct clinical judgment predictions were found after second-eye surgery compared with first eye: 100% versus 88% (moderate cataract group), 88% versus 60% (moderate cataract and comorbidity) and 71% versus 50% (advanced cataract). This indicates that PVTs may be more beneficial in the decision-making process of cataract surgery in subjects presenting for first-eye cataract surgery. In view of these results, future studies of PVTs are encouraged to focus their investigations primarily in first-eye cataract surgery subjects with and without ocular comorbidity. Conclusions and clinical implications All the evaluated PVTs were found to be adversely affected by advanced cataract with no additional information beyond clinical judgement. These results and others from several other studies18, 23, 24, 25, 26, 27, 28, 30, 33 also suggest that the standard techniques of the Potential Acuity Meter and interferometer should no longer be considered appropriate for potential vision because of their low predictive ability and inability to bypass moderate/advanced cataract. Clinical judgement on its own provides a good prediction of postoperative VA if a clear view of the fundus can be gained. Currently, most patients undergoing cataract surgery in developed countries are likely to present with early to moderate cataracts. Thus, according to our findings, clinical judgement on its own should provide reasonably accurate prediction of the likely outcome to be achieved after cataract surgery, particularly if the macula appears normal for the patient's age. During the presurgical assessment of cataract patients, clinicians are encouraged to consider the results of a variety of tests as predictors of visual performance. For example, a dilated fundus examination with fundus biomicroscopy provides a superior view of the posterior pole through a cataract than direct ophthalmoscopy and is much preferred.34 The swinging flashlight test (also known as relative afferent pupillary defect test, RAPD) may also be of significant relevance in the detection of abnormalities of the retina or optic nerve even in the presence of a dense cataract.34 Note that patients with unilateral cataract may show an RAPD in the noncataractous eye that is not reflective of visual pathway disease.35 Subtle pigmentary changes with the occasional drusen may be normal in patients older than 65 years of age, but these patients can still retain very good VA. The average VA for elderly subjects (i.e., about 75 years of age) with normal healthy eyes is actually 20/20+.34 Another useful indicator for patients undergoing second eye surgery is to compare the appearance of the maculae in the pseudophakic eye with that in the cataractous eye using the relative appearance plus the VA in the pseudophakic eye to predict the postoperative VA in the cataractous eye. When uncertain of the effect of any retinal/neural changes in the presence of moderate cataracts, our results suggest that the super-illuminated pinhole distance technique may provide additional information beyond the clinical judgement. Finally, and based on the outputs of this study, we encourage those involved in the development of computerized eye charts to further develop a simple super-illuminated pinhole distance strategy that, combined with a pinhole, could be used to provide accurate predictions of postoperative visual outcome. Acknowledgments The authors thank the consultants and staff of the Eye Department of Leeds Teaching Hospitals Trust for their assistance. References 1. 1Norregaard JC, Bernth-Petersen P, Alonso J, et al. Visual functional outcomes of cataract surgery in the United States, Canada, Denmark, and Spain: report of the International Cataract Surgery Outcomes Study. J Cataract Refract Surg. 2003;29:2135–2142. Abstract | Full Text |
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32. 32Elliott DB, Trukoloilic M, Strong JG, et al. Demographic characteristics of the vision-disabled elderly. Invest Ophthalmol Vis Sci. 1997;38:2566–2575. MEDLINE 33. 33Guyton DL. Preoperative visual acuity evaluation. Int Ophthalmol Clin. 1987;27:140–148. MEDLINE 34. 34Elliott DB. Clinical procedures in primary eye care. 3rd ed. Edinburgh: Butterworth-Heinemann; 2007;. 35. 35Lam BL, Thompson HS. A unilateral cataract produces a relative afferent pupillary defect in the contralateral eye. Ophthalmology. 1990;97:334–338. Abstract a University of Bradford, Department of Optometry, West Yorkshire, United Kingdom b Leeds Teaching Hospitals Trust, Ophthalmology Department, St. James's University Hospital, West Yorkshire, United Kingdom  Corresponding author: Marta Vianya-Estopa, Ph.D., University of Bradford, Department of Optometry, Bradford BD7 1DP, West Yorkshire, United Kingdom.
Conflict of interest: None of the authors have a financial or proprietary interest in any method or material mentioned in this study. PII: S1529-1839(09)00299-1 doi:10.1016/j.optm.2008.11.011 © 2009 American Optometric Association. Published by Elsevier Inc. All rights reserved. | |
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