OPTOMETRY ORIGINAL PAPER. Post-capsulotomy dysphotopsia in monofocal versus multifocal lenses

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1 C L I N I C A L A N D E X P E R I M E N T A L OPTOMETRY ORIGINAL PAPER Post-capsulotomy dysphotopsia in monofocal versus multifocal lenses Clin Exp Optom 2009; 92: 2: Richard Allen* FCOptom Gregory O Ho-Yen MRCOphth Adrian B Beckingsale* FRCOphth Fred W Fitzke PhD Andrea G Sciscio* FRCOphth George M Saleh MRCOphth * Department of Ophthalmology, Essex County Hospital (Colchester, UK) Department of Ophthalmology, Frimley Park Hospital (Surrey, UK) Department of Psychophysics, Institute of Ophthalmology (London, UK) Richardallen_@btopenworld.com Submitted: 2 July 2008 Revised: 26 September 2008 Accepted for publication: 7 October 2008 DOI: /j x Purpose: To compare the photic symptoms experienced by patients with the monofocal SI30 intraocular lens (IOL) with the refractive multifocal SA40 Array IOL after capsulotomy. Methods: In this prospective cohort study, 49 eyes of 49 patients (20 multifocal, 29 monofocal IOLs) were assessed following uncomplicated cataract extraction and Nd:YAG capsulotomy equal to the scotopic pupillary diameter. Subjects with post-operative refraction of 1.00 or more DS, 1.00 or more DC, concurrent ocular pathology, LogMAR acuity of worse than 0.3 for distance or 1.0 for near were excluded. Glare and halo were assessed objectively with computer-generated psychophysical tests (Glare and Halo) and subjective dysphotopic symptoms were evaluated with Tester, Javitt, Winther-Neilsen and Sedgewick questionnaires. Results: No significant difference was found for mean halo size (square degrees) between monofocals (121.33) and multifocals (97.32, p = 0.207) or for mean glare (percentage contrast), monofocals (7.881) and multifocals (7.353, p = 0.812). No significant differences in the subjective appreciation of dysphotopsia were found: Tester (p = 0.358), Javitt (p = 0.29), Winther-Neilson (p = 0.54) and Sedgewick questionnaires (p = 0.134). Conclusion: The posterior capsule is an important optical medium, which has not been fully considered in other comparative studies and its complete removal eliminates any confounding contribution. The results suggest that after capsulotomy, there is no significant difference in objective or subjective photic phenomena between monofocal and multifocal silicone lenses. Dysphotopic symptoms in patients with refractive multifocal IOLs were comparable to monofocal IOL patients after capsulotomy. Key words: capsulotomy, dysphotopsia, glare, haloes, multifocal IOLs, YAG Multifocal intraocular lenses (MIOL) have been implanted since 1986, improving the quality of vision following cataract surgery by providing a clear optical medium and focus with pseudo-accommodation. This allows better near and intermediate unaided vision, reducing spectacle dependence 1,2 with comparable distance vision to monofocals. 3 The acuity measurements do not reflect the full extent of visual function, with some MIOL patients reporting good visual acuity but also complaining of photic phenomena, which include glare and halo. 2,4,5 Glare is caused by interference by stray or scattered light within the refractive or ocular media and generally denotes a reduction in contrast of observed objects due to a strong glare source somewhere in the visual field (for example, low sun, head lights) causing a reduction in Clinical and Experimental Optometry 92.2 March The Authors 104 Journal compilation 2008 Optometrists Association Australia

2 Figure 1. AMO Array SA40N multifocal lens contrast and visibility of target objects. Halos are dim discs of light or blurred circles surrounding the images of a light source and are commonly perceived when looking at a bright light source in the dark, such as when looking at street lamps on a foggy night. 6,7 They are formed by light rays that are deviated or scattered outside the focused image. Both of these phenomena are caused by the same underlying effect: stray light. Both lens geometry and physiological factors contribute to these photic phenomena. Having less abrupt transitions in the form of a series of repeatable, continual aspheric power distributions on the anterior surface, the AMO Array refractive multifocal intraocular lens has lower potential for halo and glare than some other MIOLs and there have been reports of comparable photic phenomena to monofocal lenses. 8 Previous studies did not fully account for the posterior capsule, 9 an important optical medium, which has been shown to significantly influence contrast sensitivity and glare disability measurements 10,11 and may have been significant in previous comparative studies. Furthermore, it has been shown that glare and halo can be significantly reduced by performing a Nd:YAG capsulotomy. 11,12 Consequently, this study was designed to evaluate glare and halo in multifocal compared to monofocal lenses postcapsulotomy, once the additional potential source of stray light has been removed. In addition to the objective evaluation, extensive subjective assessment of photic phenomena using previously published questionnaires 1,13 16 was undertaken. METHODS Patients Subjects were recruited consecutively following uncomplicated clear corneal phacoemulsification cataract extraction and Nd:YAG capsulotomy for clinically significant levels of posterior capsular opacification by one surgeon (ABB). Sample size planning (power calculation) was performed and a sample size of 20 in each group was deemed to have 90 per cent predictive power to detect a difference, with a 95% confidence level. This high predictive power for the relatively small sample size is a result of merging a large number of specific data streams for each patient. There were 49 patients (49 eyes) recruited, 29 patients having received the monofocal AMO SI30 foldable silicone intraocular lens and 20 having received the refractive multifocal AMO Array SA40N foldable silicone lens. No patient had a multifocal lens in one eye and a monofocal lens in the other. The lenses were implanted via an injector into the capsular bag with sutureless closure. Nd:YAG capsulotomy was carried out on all patients on the basis of clinicallyevident posterior capsule opacification at a minimum time of six months postoperatively. An Alcon YAG 2500 was used to create a capsulotomy equal to or greater in diameter than the scotopic pupillary diameter, as determined by ruler measurement in a darkened psychophysical laboratory. Any lens with pitting following capsulotomy was excluded. Patients received a full slitlamp examination to rule out any concurrent pathology before being enrolled into the study. Full ethical approval was obtained and informed consent was elicited from all patients. LogMAR visual acuity for near and distance was measured at least two months post-operatively. All patients included in the study had acuities better than 0.3 for distance and 1.0 for near and a postoperative refraction of equal to or less than 1.00 D sphere with no more that 1.00 D cylinder. The Array is a distance dominant zonalprogressive multifocal lens that has five annular aspheric zones, each containing continuous curves of refractive power up to 3.5 D. The central two millimetres is used mainly for the distance focus (Figure 1). The less abrupt transitions in the form of repeatable, continuous aspheric power distributions on the anterior surface are designed to reduce the potential for halo and glare. Glare and halo assessment A modified version of the Van den Berg test was used to assess glare and halo using a computerised testing method (Glare and Halo) in a completely darkened, dedicated psychophysics laboratory. By surrounding a central test light stimulus with an annulus of background illumination, the test evaluates any decrease in contrast between the two elements caused by light scatter. A central circle subtending one degree was displayed at the centre of the video display unit (VDU) screen, which was surrounded by an annulus up to 2.5 degrees and then a third annulus up to five degrees (Figure 2). The first and outer annuli were set to a luminance of 86.8 cd/m 2, while the middle annulus and background levels were set to 10.1 cd/m 2. Luminance of the central circle flickered between the background level and the 2008 The Authors Clinical and Experimental Optometry 92.2 March 2009 Journal compilation 2008 Optometrists Association Australia 105

3 Central flickering circle Fixation point Illuminated annulus Outer limit of halo Flickering stray light source Figure 2. Glare test: VDU screen displaying the concentric annuli of the glare test Figure 3. Halo test: VDU screen displaying the halo source and the marker for the halo test subject controlled match level at a frequency of 7.5 Hz. The test was performed monocularly at 28 cm from the video screen, thereby using all optical zones in the multifocal lens subjects. The viewing distance was indicated by a distance marker and strictly enforced by an observer. The eye not being assessed was occluded. The subject varied the match luminance of the central stimuli using two buttons on the computer to minimise the flicker with the background. The program calculated the difference between the patient-set match level and the background luminance and then converted the value to contrast using the Michelson contrast definition. 6 The value provided is for critical flicker frequency without a stray light source. This process was repeated a further nine times and on each occasion the match level was reset to a randomly selected new luminance of between 20 and 40 per cent brighter or darker than the background. A flickering annulus stray light-source was then added and the matching test repeated a further 10 times. Once the glare source had been added, the difference in the contrast values gives the value of the effect of glare. Halo was measured using a red fixation cross within a white ring (luminance of 86.6 cd/m 2 ), which generated the halo source on a black background. At a fixation distance of 1,000 mm, the subject positions a marker at the outer limit of the halo using a computer mouse, recording the size of halo around the ring at 30-degree intervals around the halo source. The area of halo was then calculated in square degrees (Figure 3). Patient questionnaires Subjective evaluation of photic phenomena was performed using four previously published questionnaires: the Tester, 14 Javitt, 1 Winther-Neilson 15 and the Sedgewick 16 instruments. The Tester questionnaire was published by Tester and colleagues 14 and was designed to determine whether a patient was experiencing any form of dysphotopsia. Patients who do experience dysphotopsia are then asked more about the nature of the symptoms. The questionnaire is structured around six stems, with the first three questions on dysphotopic symptoms being graded on a scale of zero to three. Overall satisfaction with vision is scored on a scale of zero to five. In this study, the Tester questionnaire was conducted in interview rather than by telephone. The Javitt questionnaire 1 is a detailed quality of life questionnaire, with respect to dysphotopic symptoms. It involves questions related to spectacle wearing habits, self-reported rating of vision (zero to 10) and eight further sets of questions related to symptoms of glare and halo occurring during activities of daily life, scored on a scale of zero to four. The Winther-Nielson questionnaire 15 involves questions relating to necessity for wearing sunglasses, a comparison of preand post-operative vision, and some very specific questions pertaining to the type of dysphotopic symptoms that were originally volunteered with the early multifocal lens types. The answers were weighted and given a score on a scale of zero to 10 for their relative importance. The Sedgewick instrument 16 is a questionnaire with detailed questions relating to frequency of near and distance spectacle wear, satisfaction with vision and problems with unwanted visual phenomena such as glare, halo and rings. The sections of the questionnaires relating to photic phenomena were used in this study. Statistical analysis The comparison of between-group variables with the subjective data set was performed using the Wilcoxon Mann- Whitney test and for objective data a two tailed t-test was used. Statistical significance was set at p < Clinical and Experimental Optometry 92.2 March The Authors 106 Journal compilation 2008 Optometrists Association Australia

4 120 Mean glare /contrast to add Mean halo size/square degrees Score Monofocal Multifocal 0 Monofocal Multifocal 0 Monofocal Multifocal Figure 4. Glare size: mean glare in monofocal and multifocal groups Figure 5. Halo size: mean halo size in monofocal and multifocal groups Figure 6. Javitt questionnaire scores: Javitt scores in the monofocal and multifocal groups RESULTS The average age in the monofocal group was (SD) years and years in the multifocal group. No statistically significant difference was found between the two groups (p = 0.15). Average recorded pupil diameter in the monofocal group was mm and in the multifocal group it was found to be mm. No statistically significant difference was found between the two groups (p = 0.36). Visual acuity The mean distance VA for the monofocal (mono) group was and in the multifocal (multi) group was At near, the mean logmar VA was in the mono group and in the multifocal group. Glare The mean glare (in percentage contrast) was for mono and for multifocal. No statistically significant difference between the two groups was found for glare (p = 0.812) (Figure 4). The inter-subject variation in results was from 0.15 to in mono and 1.69 to in multifocals. Halo The mean halo size (square degrees) was for mono and (sd 43.38) for multifocals. No statistically significant difference between the two groups was found for halo (p = 0.207) (Figure 5). The inter-subject variation in halo size was to in the monofocal group and to in the multifocal group. Questionnaire results The Tester questionnaire was broken down individually and analysed question by question. The first question addresses glare. The multifocal group had a mean score of 0.63 (less bothered by glare) than the monofocal group with a mean score of 1.06, however, this was found to be not statistically significant (p = 0.36). The question addressing unwanted images also returned a statistically insignificant result (p = 0.98). There were no statistically significant differences in subject satisfaction with vision (p = 0.41) nor was there any statistical difference between the two groups in any dissatisfaction being linked with photic phenomena (p = 0.67). The Javitt questionnaire, which generates one single score, produced a mean score of in the monofocal group and in the multifocal group, however, there was no significant difference between the two groups (p = 0.29), even when focusing on photic phenomena (Figure 6). The Winther-Nielson questionnaire, which assesses vision and ability to see critical detail in everyday settings and compares this with vision before the cataract extraction, did not reveal any statistically significant difference between the two groups (p = 0.54). The Sedgewick Survey Instrument did not reveal any significant difference between the two groups in their reporting of being bothered by glare, halos, or rings around lights (p = 0.134). DISCUSSION Photic phenomena are a recognised consequence of pseudophakia. 17 Increased glare and halo have been demonstrated with all types of IOL compared with phakic subjects 17 and they are influenced by the specific design of the IOL. 8 Multifocal lenses have been identified as having a higher incidence of these photic phenomena compared to monofocal lenses, however, this effect appears to be more marked with the early diffractive lenses 2008 The Authors Clinical and Experimental Optometry 92.2 March 2009 Journal compilation 2008 Optometrists Association Australia 107

5 than the refractive types 6,18 and the posterior capsule, an important optical medium, has not been fully considered in these other comparative studies. The complete removal of the capsule from the optical axis in the subjects of this study eliminates the possibility of this contributory and confounding factor. This study was specifically designed to evaluate photic phenomena from two important perspectives: objectively with photic testing and subjectively with multiple questionnaires. The questionnaire results show no statistically significant difference in the subjective experience of photic phenomena between subjects with multifocal and monofocal lenses compared with some previous subjective assessments with the capsule still intact. 19 This comprehensive evaluation of the subjective perception of dysphotopsia and quality of vision adds significant weight to the objective results found in the same cohorts. It is a significant finding that the initial problems that were raised with multifocal IOLs, that is, disabling subjective photic phenomena, were not found to be of concern in the subjects of this study who have had capsulotomies. The objective glare and halo measurements also show no statistically significant difference between subjects with multifocal and monofocal lenses. This is in contrast to previous studies that have shown a significant difference in glare especially at low and high-end spatial frequencies 20 and others reporting a greater incidence of photic phenomena in subjects with the multifocal lens. 4,8 Again subjects in these studies had not undergone capsulotomy. However, a study by Dick and associates 8 in patients without capsulotomies found no difference in dysphotopsia between the two groups. It may be that glare and halo are not the only photic phenomena that MIOLs induce contributing to the results. Other studies have failed to find a difference in dysphotopsia between multifocal and monofocal lenses, 6 suggesting that both testing modality and variability of dysphotopic appreciation contribute to the outcome. It is apparent that as a result of its design, the Array multifocal lens has both the potential benefit of good unaided vision for near and distance 9 and the potential disadvantage of dysphotopsia in part through its innate optical properties. The best results with the Array will always be accomplished with careful patient selection. With the increasing popularity of presbyopic lens exchange (PreLEX) in a younger and more optically dynamic population, capsulotomies may help treat difficulties experienced by some of these patients. Although complications associated with posterior capsulotomy are rare, each case should be considered on an individual basis. 21,22 It should also be considered that the functional optical area of the MIOL relates to the diameter of the anterior and posterior capsular opening. Further studies of dysphotopsia are needed, to define the precise effect the posterior capsule has with these IOLs but capsular opacity may have an especially detrimental effect on visual quality in patients with these lenses. It is possible that removal of the posterior capsule may help alleviate some of the optical side effects in patients with the Array. DISCLOSURE None of the six authors has any proprietary or financial interest in these products. REFERENCES 1. Javitt JC, Wang F, Trentacost DJ, Rowe M, Tarantino N. Outcomes of cataract extraction with multifocal intraocular lens implantation; functional status and quality of life. 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6 photic phenomena with refractive multifocal and monofocal intraocular lenses. J Cataract Refract Surg 2001; 27: Weghaupt H, Pieh S, Skorpik C. Visual properties of the foldable Array multifocal intraocular lens. J Cataract Refract Surg 1996; 22: Dick B, Schwenn O, Eisenmann D. Reflections on Nd:YAG capsulotomy in lens opacity after multifocal lens implantation Klin Monatsbl Augenheilkd. 1997; 211: Jahn CE, Richter J, Jahn AH, Kremer G, Kron M. Pseudophakic retinal detachment after uneventful phacoemulsification and subsequent neodymium: YAG capsulotomy for capsule opacification. J Cataract Refract Surg. 2003; 29: Corresponding author: Richard Allen Ophthalmology Department Essex County Hospital Colchester, Essex UNITED KINGDOM Richardallen_@btopenworld.com 2008 The Authors Clinical and Experimental Optometry 92.2 March 2009 Journal compilation 2008 Optometrists Association Australia 109