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Reading performance after pseudoaccommodating IOLs
LETTERS
Reading performance after pseudoaccommodating IOLs Hu¨tz et al.1 assessed the reading performance of patients implanted with 3 different pseudoaccommodating intraocular lenses (IOLs) by evaluating reading acuity and reading speed tests. The article invites an analysis of the concept of reading and how ophthalmologists should use objective reading measures for clinical purposes. When we assess near-vision performance, we measure the capability of the patient to recognize a series of letters on a near-vision chart. However, a legitimate question is whether this is the correct way to evaluate near vision and whether this has value in measuring the success of presbyopic refractive surgery. It is reasonable to conclude that a more functional activity, such as reading, may be more useful. Reading is an important everyday task, but the lack of a concise definition makes it difficult to apply objective criteria to any measure of reading. It is not easy to define what reading means, as it is a generic term subject to interpretation. For example, some may consider working on a computer, perusing a map, or checking the newspaper for the latest sports results to be reading, but these activities may not be reading in the strictest sense.2 Reading involves complicated mental processes activated in the interpretation of concepts and meanings that are stimulated by the recognition of printed symbols. There is universal agreement among experts in the field that the best definition of reading is the ability to derive meaning from text.3,4 Carver5 reported 5 rates of reading: scanning, skimming, rauding, learning, and memorizing. Scanning is the fastest rate and usually involves the reader searching for a target word by looking at each consecutive word of a prose passage. Skimming is the second fastest rate or process; the reader is searching a prose passage to find 2 adjacent words whose order has been reversed or transposed. Rauding, a relatively new word defined as reading with comprehension,5 is usually adopted while reading a prose passage. Learning is slower than rauding but more powerful; the aim of the reader is to understand the information contained in the passage. Memorizing is the slowest rate of reading. The reading performance of an individual can be measured simply and objectively by using 2 variables: reading speed and reading rate. Reading speed is a measure of the number of words one can read per minute or per second; it assesses only the speed with which one reads. Reading rate is measured by determining the correctly read words per minute and requires accuracy from the reader. The reading speed Q 2008 ASCRS and ESCRS Published by Elsevier Inc.
refers to how fast words can be read, whereas reading rate is used when accuracy is the main goal or aim. As such, reading rate seems to be a more valid measure of one’s reading performance. The advantage of using these metrics in the assessment of reading performance is the easy measurement, avoiding special instructions for the patient and requiring a minimum of equipment (ie, a timer). The major disadvantage is that neither provides an indicator of understanding as both measurements focus on the number of words read per minute. In light of the above, as well as more general considerations of testing near vision, one must reevaluate the study by Hu¨tz et al.1 with the following concerns: 1. Reading speed is not a completely objective or absolute measurement of reading ability. Different patients may read at different speeds irrespective of what multifocal IOL has been implanted and randomizing such a patient population would be difficult in the extreme. The only defensible measure of reading speed in this regard would be an analysis before and after clear lens extraction surgery, in which the patient would serve as his or her own control. This is clearly not feasible in the case of cataract patients in whom preoperative acuity will significantly degrade performance. 2. Reading speed is reported, but not reading rate. With no indication of whether reading is accurate, the speed may be irrelevant. 3. The residual refractive error of all patients is mentioned only briefly. No ranges for residual sphere or cylinder are provided, giving no context for making comparisons of uncorrected reading ability between IOLs. There is a systematic mean residual cylinder reported for one IOL but for not the others. This is likely to affect reading ability. 4. There is no discussion of the procedure for testing reading ability. For instance, when measuring uncorrected reading, patients should be instructed to hold the reading chart at the distance that provides their best near vision (influenced by the IOL near add). Calculations can then be applied to standardize results between patients based on their various preferred reading distances. A defocused reading chart is likely to significantly reduce reading speed. 5. The near test distance is never specified. The use of a 2.5 diopter (D) addition for the ‘‘corrected’’ condition suggests a standard near distance of 40 cm, an inappropriate distance if the multifocal IOL has a different near focal length. The corrected condition should have provided patients the best near acuity at a distance they preferred, after which appropriate calculations could be performed to standardize results between patients. 0886-3350/08/$dsee front matter doi:10.1016/j.jcrs.2007.09.034
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LETTERS
6. Pupil measurements in light and dark conditions were carefully measured, but only in distance gaze. The authors neglect the natural pupil constriction that will occur with the ‘‘near triad.’’ The near pupil sizes in light and dark cannot be assumed to be the same as for distance. Some IOLs, such as the ReSTOR (Alcon), have a light energy distribution based on changes in pupil size. Checking the study groups for similarity of distance pupil size may have missed between-group size differences at near. 7. In some instances in the study, the best corrected visual acuity resulted in slower reading speeds. This is counterintuitive and suggests that the best corrected acuity was inappropriate; in general, if a best near refractive correction impedes performance, no correction is the best corrected state for near. 8. Several images are included in the article, but the test distances are not indicated. As such, the figures have no value. Since all the IOLs in the study have different near foci, there is no one appropriate test distance. 9. The ranges of reading speed and reading acuity are not indicated in the tables. With standard deviations that are in some cases almost as high as the values being measured, this should be considered critical to interpreting results. Excessive ranges would suggest a poor ability to match groups, even if randomized, and a poor ability to attribute differences between groups to anything but chance. In summary, there are 2 fundamental problems that may compromise the conclusions of this study. First is that there are significant challenges to using reading speed and or reading acuity as objective functional measures in the absence of controls. (As noted, such a study of clear lens extraction patients may be a more appropriate test population because they can serve as their own controls.) Second, and no less important, is the appearance that the study lacked customization. For instance, there is no description of test distances, which should have varied by IOL. The authors also appear to have used a standardized rather than an individually determined best near correction (C2.50 D, with no astigmatism correction despite a significant amount of astigmatism in 1 subgroup). In light of the limitations of reading speed and reading acuity described above and the limitations of the study design, it is apparent that the conclusions the authors reach may not be corroborated in the real world. We would respectfully suggest that a more IOL-specific study design and an improved objective measure of reading would yield conclusions that will be more reflective of multifocal IOL performance in the real world.
Robert Monte´s-Mico´, PhD Valencia, Spain Jose´ F. Alfonso, MD, PhD Oviedo, Spain REFERENCES 1. Hu¨tz WW, Eckhardt HB, Ro¨hrig B, Grolmus R. Reading ability with 3 multifocal intraocular lens models. J Cataract Refract Surg 2006; 32:2015–2021 2. Rayner K, Pollatsek A. The Psychology of Reading. Englewood Cliffs, NJ, Prentice-Hall, 1989 3. Legge GE, Pelli DG, Rubin GS, Schleske MM. Psychophysics of reading.dI. Normal vision. Vision Res 1985; 25:239–252 4. Whittaker SG, Lovie-Kitchin J. Visual requirements for reading. Optom Vis Sci 1993; 70:54–65 5. Carver RP. Reading Rate: A Review of Research and Theory. San Diego, CA, Academic Press, 1990
REPLY: We welcome the opportunity to respond to the concerns that Monte´s-Mico and Alfonso have raised. It is legitimate to question the relevance and objectivity of reading measures for clinical purposes since reading is a complex cognitive and linguistic process and therefore, by definition, difficult to define and assess. Nonetheless, as pointed out by Monte´sMico and Alfonso, there is common agreement among the experts in the field that the best definition of reading is the ability to derive meaning from text.1,2 Therefore, successful reading would depend on having available a repertoire of decoding and comprehension skills and strategies, which would imply that the reader has a certain level of education. However, our primary goal as ophthalmologists is to find out what affects patient reading abilities disregarding the intellectual level of the person tested. For this purpose, Radner et al.3 have developed a new type of reading chart for the simultaneous evaluation of reading acuity and reading speed. This chart is the result of cooperation with linguists, psychologists, and computer scientists and is in accord with the current international standards for visual acuity measurements and psychophysical requirements for controlling optical item interactions.4–6 The Radner reading charts consist of 24 very simple sentences, developed to be highly comparable in grammatical difficulty as well as number of words and length and position of the words. The phrases have been created to perform reading acuity and reading speed measurements without regard for the intellectual level of the reader. Everyone who is able to read can read these phrases and can derive meaning from text.1,2 This approach was validated in a study in which Radner et al.3 compared reading acuity and speed of 80 university students and 80 blue collar apprentices and found no statistical difference between
J CATARACT REFRACT SURG - VOL 34, FEBRUARY 2008
Reading performance after pseudoaccommodating IOLs Hu¨tz et al.1 assessed the reading performance of patients implanted with 3 different pseudoaccommodating intraocular lenses (IOLs) by evaluating reading acuity and reading speed tests. The article invites an analysis of the concept of reading and how ophthalmologists should use objective reading measures for clinical purposes. When we assess near-vision performance, we measure the capability of the patient to recognize a series of letters on a near-vision chart. However, a legitimate question is whether this is the correct way to evaluate near vision and whether this has value in measuring the success of presbyopic refractive surgery. It is reasonable to conclude that a more functional activity, such as reading, may be more useful. Reading is an important everyday task, but the lack of a concise definition makes it difficult to apply objective criteria to any measure of reading. It is not easy to define what reading means, as it is a generic term subject to interpretation. For example, some may consider working on a computer, perusing a map, or checking the newspaper for the latest sports results to be reading, but these activities may not be reading in the strictest sense.2 Reading involves complicated mental processes activated in the interpretation of concepts and meanings that are stimulated by the recognition of printed symbols. There is universal agreement among experts in the field that the best definition of reading is the ability to derive meaning from text.3,4 Carver5 reported 5 rates of reading: scanning, skimming, rauding, learning, and memorizing. Scanning is the fastest rate and usually involves the reader searching for a target word by looking at each consecutive word of a prose passage. Skimming is the second fastest rate or process; the reader is searching a prose passage to find 2 adjacent words whose order has been reversed or transposed. Rauding, a relatively new word defined as reading with comprehension,5 is usually adopted while reading a prose passage. Learning is slower than rauding but more powerful; the aim of the reader is to understand the information contained in the passage. Memorizing is the slowest rate of reading. The reading performance of an individual can be measured simply and objectively by using 2 variables: reading speed and reading rate. Reading speed is a measure of the number of words one can read per minute or per second; it assesses only the speed with which one reads. Reading rate is measured by determining the correctly read words per minute and requires accuracy from the reader. The reading speed Q 2008 ASCRS and ESCRS Published by Elsevier Inc.
refers to how fast words can be read, whereas reading rate is used when accuracy is the main goal or aim. As such, reading rate seems to be a more valid measure of one’s reading performance. The advantage of using these metrics in the assessment of reading performance is the easy measurement, avoiding special instructions for the patient and requiring a minimum of equipment (ie, a timer). The major disadvantage is that neither provides an indicator of understanding as both measurements focus on the number of words read per minute. In light of the above, as well as more general considerations of testing near vision, one must reevaluate the study by Hu¨tz et al.1 with the following concerns: 1. Reading speed is not a completely objective or absolute measurement of reading ability. Different patients may read at different speeds irrespective of what multifocal IOL has been implanted and randomizing such a patient population would be difficult in the extreme. The only defensible measure of reading speed in this regard would be an analysis before and after clear lens extraction surgery, in which the patient would serve as his or her own control. This is clearly not feasible in the case of cataract patients in whom preoperative acuity will significantly degrade performance. 2. Reading speed is reported, but not reading rate. With no indication of whether reading is accurate, the speed may be irrelevant. 3. The residual refractive error of all patients is mentioned only briefly. No ranges for residual sphere or cylinder are provided, giving no context for making comparisons of uncorrected reading ability between IOLs. There is a systematic mean residual cylinder reported for one IOL but for not the others. This is likely to affect reading ability. 4. There is no discussion of the procedure for testing reading ability. For instance, when measuring uncorrected reading, patients should be instructed to hold the reading chart at the distance that provides their best near vision (influenced by the IOL near add). Calculations can then be applied to standardize results between patients based on their various preferred reading distances. A defocused reading chart is likely to significantly reduce reading speed. 5. The near test distance is never specified. The use of a 2.5 diopter (D) addition for the ‘‘corrected’’ condition suggests a standard near distance of 40 cm, an inappropriate distance if the multifocal IOL has a different near focal length. The corrected condition should have provided patients the best near acuity at a distance they preferred, after which appropriate calculations could be performed to standardize results between patients. 0886-3350/08/$dsee front matter doi:10.1016/j.jcrs.2007.09.034
177
178
LETTERS
6. Pupil measurements in light and dark conditions were carefully measured, but only in distance gaze. The authors neglect the natural pupil constriction that will occur with the ‘‘near triad.’’ The near pupil sizes in light and dark cannot be assumed to be the same as for distance. Some IOLs, such as the ReSTOR (Alcon), have a light energy distribution based on changes in pupil size. Checking the study groups for similarity of distance pupil size may have missed between-group size differences at near. 7. In some instances in the study, the best corrected visual acuity resulted in slower reading speeds. This is counterintuitive and suggests that the best corrected acuity was inappropriate; in general, if a best near refractive correction impedes performance, no correction is the best corrected state for near. 8. Several images are included in the article, but the test distances are not indicated. As such, the figures have no value. Since all the IOLs in the study have different near foci, there is no one appropriate test distance. 9. The ranges of reading speed and reading acuity are not indicated in the tables. With standard deviations that are in some cases almost as high as the values being measured, this should be considered critical to interpreting results. Excessive ranges would suggest a poor ability to match groups, even if randomized, and a poor ability to attribute differences between groups to anything but chance. In summary, there are 2 fundamental problems that may compromise the conclusions of this study. First is that there are significant challenges to using reading speed and or reading acuity as objective functional measures in the absence of controls. (As noted, such a study of clear lens extraction patients may be a more appropriate test population because they can serve as their own controls.) Second, and no less important, is the appearance that the study lacked customization. For instance, there is no description of test distances, which should have varied by IOL. The authors also appear to have used a standardized rather than an individually determined best near correction (C2.50 D, with no astigmatism correction despite a significant amount of astigmatism in 1 subgroup). In light of the limitations of reading speed and reading acuity described above and the limitations of the study design, it is apparent that the conclusions the authors reach may not be corroborated in the real world. We would respectfully suggest that a more IOL-specific study design and an improved objective measure of reading would yield conclusions that will be more reflective of multifocal IOL performance in the real world.
Robert Monte´s-Mico´, PhD Valencia, Spain Jose´ F. Alfonso, MD, PhD Oviedo, Spain REFERENCES 1. Hu¨tz WW, Eckhardt HB, Ro¨hrig B, Grolmus R. Reading ability with 3 multifocal intraocular lens models. J Cataract Refract Surg 2006; 32:2015–2021 2. Rayner K, Pollatsek A. The Psychology of Reading. Englewood Cliffs, NJ, Prentice-Hall, 1989 3. Legge GE, Pelli DG, Rubin GS, Schleske MM. Psychophysics of reading.dI. Normal vision. Vision Res 1985; 25:239–252 4. Whittaker SG, Lovie-Kitchin J. Visual requirements for reading. Optom Vis Sci 1993; 70:54–65 5. Carver RP. Reading Rate: A Review of Research and Theory. San Diego, CA, Academic Press, 1990
REPLY: We welcome the opportunity to respond to the concerns that Monte´s-Mico and Alfonso have raised. It is legitimate to question the relevance and objectivity of reading measures for clinical purposes since reading is a complex cognitive and linguistic process and therefore, by definition, difficult to define and assess. Nonetheless, as pointed out by Monte´sMico and Alfonso, there is common agreement among the experts in the field that the best definition of reading is the ability to derive meaning from text.1,2 Therefore, successful reading would depend on having available a repertoire of decoding and comprehension skills and strategies, which would imply that the reader has a certain level of education. However, our primary goal as ophthalmologists is to find out what affects patient reading abilities disregarding the intellectual level of the person tested. For this purpose, Radner et al.3 have developed a new type of reading chart for the simultaneous evaluation of reading acuity and reading speed. This chart is the result of cooperation with linguists, psychologists, and computer scientists and is in accord with the current international standards for visual acuity measurements and psychophysical requirements for controlling optical item interactions.4–6 The Radner reading charts consist of 24 very simple sentences, developed to be highly comparable in grammatical difficulty as well as number of words and length and position of the words. The phrases have been created to perform reading acuity and reading speed measurements without regard for the intellectual level of the reader. Everyone who is able to read can read these phrases and can derive meaning from text.1,2 This approach was validated in a study in which Radner et al.3 compared reading acuity and speed of 80 university students and 80 blue collar apprentices and found no statistical difference between
J CATARACT REFRACT SURG - VOL 34, FEBRUARY 2008