Reversal of glare disability after cataract surgery

Reversal of glare disability after cataract surgery Samuel Masket, M.D.

TR. war n f th Iimitati n. of nell n VI 'lon t .ting and th fav rabl rioIe-to-beneflt ratio ~ r atara t sur ry hav han~ d th indicati n ~ r at ra t rehabilit tion. Int re ·t in fun tional i ion nal i generated th pre nt tud ', whi h wa de i~n d to id ntify at ra t- pe ifl di abling ~Iare and it r V r. al with be t- a e atara t ur i al t chniqu . Thirt} e with ) mptomatic catura t w re \.uluated by . till r- 'udler ~Iare nd no oth r ular di ' a t ting prior to and . i \.\. k. aft r ur~ery. II urgi al ca • w re un omplicated and w r fr of mucular di ea e. The hud \\.ellntered po terior hamber intraocular len. e, leun po trior cap ul , and were r turned t 2 120 n lien a uit. ar ·ful pati nt Ie tion a . ur d that preur~ical glare di abilit) wa du to catara t ~ rmation. Pre urgi al . fill r-, Tadl'r ore \\ murk dly I vat d and c rrelatcd well with s mpt mati glat", \ 'herea I toperativ ore w r indi tingui. habl from normal u~e tin~ that 'atara tindu d mptomati lare i di rnibl, r mediable, and\. 'arrant urgi al int nenti n, but r
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Recent decades have brought marked advances in cataract rehabilitative techniques, which have reduced the surgical risks and alleviated the prognostic fears of cataract patients. As a result of the favorable risk-tobenefit ratio for cataract removal, symptomatic patients often request surgery before a major reduction in their Snellen acuity results. Moreover, subjective visual complaints, such as disabling glare, have become indications for cataract surgery. 1 ,2 However, appropriate surgical guidelines for glare disability symptoms have not been established. Glare may be considered as the reduction in visual performance associated with intraocular scattering of light; light scatter within the eye results in a reduced contrast sensitivity of the visual system. 3 While glare

symptoms may be induced by any but complete opacification of the ocular media, such as corneal scars or vitreous opacities, cortical cataract formation is the most common cause of disabling glare. Contrast sensitivity may also be reduced by organic macular disease 4 and optic nerve disorders such as glaucoma. 5 Interest in quantifying glare symptoms in cataract and other ocular diseases has fostered clinically useful devices for detecting and measuring glare disability.6 ,7 The Miller-Nadler glare testing system (Figure 1) uses a modified table-top slide projector and a slide series with a 20/400 Landolt ring in black superimposed on a 40 mm gray circular background (Figure 2). Contrast between the gray circle and black Landolt ring varies progressively from 2.5% to 80.0% with each slide.

Presented in part at the Symposium on Cataract, IOL and Refractive Surgery, Los Angeles, March 1988. The author has no financial interest in the product or manufacturer mentioned. Elizabeth Jane Little assisted with the clinical testing and Karen Berk assisted with manuscript preparation. Reprint requests to Samuel Masket, M.D., Suite 204, 7230 Medical Center Drive, Canoga Park, California 91307-1957.

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Fig. 3.

Fig.. 1.

(Masket) Clinical model of the Miller-Nadler glare tester. The unit is a modified table-top projector. Glare is induced by the background illumination of the projector. The chin rest support system maintains consistent testing distance (courtesy of Titmus Optical, Inc.)

Fig. 2.

(Masket) A representative slide of the testing series. The black 20/400 sized Landolt ring is superimposed upon a 40 mm gray circle. Contrast between the circle and the Landolt ring varies progressively between 2.,5% and 80.0% in the series of slides. The background may be masked to reduce the glare source in order to distinguish between media opacity and neurosensory contrast sensitivity loss.

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(Masket) Graph supplied by manufacturer to estimate outdoor Snellen acuity in glare disabled eyes (courtesy of Titmus Optical, Inc.)

Glare is induced by the background illumination of the slide projector. In the glare-disabled subject the ability to discern the open position of the Landolt ring is affected by a reduction in contrast sensitivity caused by intraocular light scatter (assuming there is no macular or optic nerve disease), The smallest percentage of contrast that the subject eye can perceive is recorded as the score for the glare disability test. A graph estimating the outdoor Snellen acuity from the glare disability score is supplied by the manufacturer (Figure 3). The test has been modified by an additional subseries of glare-masked slides to allow a distinction between the glare disability due to opaque media and that induced by macular or optic nerve disease. 8 This study focused on the nonmasked slide series. Because cataract surgical rehabilitation may be indicated by glare symptoms without a major reduction in Snellen visual acuity,1.2 it is necessary to determine that glare testing devices yield results that match well with the patients' visual symptoms. Moreover, it must be established that cataract surgery effectively reduces measurable preoperative glare to a predictable level, similar to the return of Snellen visual acuity after successful rehabilitative surgery. This study evaluated a device for determining cataract-specific glare disability and the reversal of glare disability with current surgical management.

SUBJECTS AND METHODS Patients with visually symptomatic cataracts were selected for study if their preoperative evaluation indicated no other ocular pathology, e.g., corneal scarring, vitreous opacification, organic macular disease, or optic neuropathy.

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Preoperative examination included, but was not limited to, optically corrected distance Snellen visual acuity measured in the refracting lane, non masked Miller-Nadler glare score without pupillary mydriasis, slitlamp biomicroscopy, and direct and indirect ophthalmoscopy. Glare testing was performed by a technician unaware of the conduct of the study. Cataract surgery was performed uniformly for all eyes by phacoemulsification with posterior chamber intraocular lens (IOL) implantation through a scleral pocket incision. 9 Implants were from several manufacturers. They were 6.0 mm or 6 .5 mm in diameter, convex-plano, and had two or four full-thickness positioning holes in the periphery of the optic; 6.5 mm lenses had laser spacing devices. All cases received topical corticosteroids for four weeks after surgery. Patients were then included in the study if surgery was uncomplicated, the postsurgical course routine, and if the six week postoperative examination revealed a distance Snellen visual acuity correctable to 20/20, clear ocular media including an intact and clean posterior capsule, a well-centered IOL, and a clinically normal macular region. Only best-case eyes were studied so an evaluation of cataract specific glare and its remediation could be attained. Thirty eyes of 26 patients were included in the study. Postoperative examination at six weeks after surgery included, but was not limited to, optically corrected distance Snellen visual acuity, nonmasked Miller-Nadler glare testing without pupillary mydriasis, slitlamp biomicroscopy, and direct and indirect ophthalmoscopy. Glare testing was performed by a technician unaware of the conduct of the study. RESULTS The study population (Table 1) included a heterogeneous group of patients that ranged from 43 to 87 years of age with a mean of 66.3 years. Preoperative corrected distance Snellen acuity was between 20/30 and hand movements and averaged 20/122. (Snellen scores worse than 20/400 were assigned a value of 20/400.) Preoperative non masked Miller-Nadler glare disability scores varied with the type of cataract formation and ranged between 25% and 80% with a mean of 55.2%. Cortical and posterior subcapsular cataracts tended to be associated with greater glare

Table 1. Preoperative data on the study population (N = 30).

Age Snellen acuity Glare score

Range

Mean

43-87

66.3

20/30 - hand motion

20/122

25% - 80%

55.2%

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Table 2. Postoperative data on the study population (N = 30).

Snellen acuity Glare score

Range

Mean

20/20

20/20

2.5% - 15.0%

7.6%

Table 3. Preoperative and postoperative data on the subgroup population (n 11).

=

Preoperative

Postoperative

Mean Snellen acuity

20/46

20/20

Mean glare score

45%

6.4%

disability and showed greater disparity from Snellen acuity than did nuclear sclerotic cataracts. For example, two patients with posterior subcapsular cataracts had preoperative Snellen acuity scores of 20/30 but demonstrated high glare disability scores of 75% and 65%, respectively; postoperative glare scores were 5% for both patients. One patient with a nuclear sclerotic cataract and Snellen acuity of less than 20/400 demonstrated a presurgical glare disability score of 40%. Postoperative evaluations (Table 2) were performed six weeks after surgery. Snellen visual acuity was corrected to 20/20 in all cases. Postsurgical nonmasked Miller-Nadler glare disability scores varied from 2.5% to 1.5.0% with a mean of 7.6%. Statistical differences between preoperative and postoperative Snellen visual acuities and preoperative and postoperative nonmasked Miller-Nadler glare scores were highly significant (P <.00001). Student's paired t-test was used for statistical correlation . A subgroup of the study population, which consisted of 11 eyes with 20/60 or better preoperative optically corrected Snellen visual acuity, was evaluated similarly (Table 3). The mean age of these patients was 67.7 years, the mean preoperative corrected Snellen acuity, 20/46 (range 20/30 to 20/60), and the mean presurgical nonmasked M iller- Nadler glare disability score, 45%; postoperative mean glare score was 6.4%. Statistical differences for preoperative and postoperative visual acuity and glare scores were also highly significant (P<.OOl) for this subgroup. DISCUSSION Contrast sensitivity function testing and glare disability evaluation have become accepted means of functional vision analysis; the latter stresses the importance of determining visual performance under conditions that simulate casual seeing rather than the controlled illumination and visual conditions of the refracting lane. lO Snellen testing presents a lOQ% contrast between the black letters and the white

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background of the screen or chart. However, casual seeing presents an ever-changing series of contrast levels for our visual system to discern and it has become clear that traditional static visual acuity testing cannot determine the patient's visual function under the varied conditions presented in daily life. 11 Contrast sensitivity is affected by the clarity of the ocular media, by macular function, and by optic nerve transmission. Cataract-induced glare reduces the eye's ability to perceive contrasts as a result of intraocular light scattering. 3 The results of the present study demonstrate that cataract-specific disabling glare was discerned by the nonmasked Miller-Nadler glare testing system since no other ocular pathology was present in the study group. The study also revealed that current cataract surgical technology remediated the abnormal glare score since the mean presurgical glare disability (contrast sensitivity) score was 55.2% and the postoperative score was 7.6%. The data of the present study match well with the expected range of contrast sensitivity for normal eyes, which has been reported to be 2.5% to 20.0%,12 and the average 10% contrast sensitivity level expected for the seventh decade of life. 6 The postsurgical disability glare scores for the current study are slightly better than the postoperative Miller-Nadler scores for 45 cases reported by Koch and associates 13 (range 9.6% to 10.8%); however, in that study some cases had mild central capsular clouding and postoperative Snellen visual acuity of 20/30 was acceptable for inclusion. Conversely, the postoperative mean glare disability of 7.6% for the pseudophakic eyes of the present study was markedly better than the figures reported by Jaffe 2 and Nadler et al. 14 This difference may have occurred because the present study was limited to best-case surgery in eyes with no pathology other than symptomatic cataract. Moreover, postoperative testing was performed six weeks after surgery, earlier than posterior capsular opacification would likely be found. Jaffe 2 reported a 23% postoperative mean glare disability score for 81 patients with posterior chamber IOLs and intact posterior capsules measured between six and 14 months after surgery. Knighton and associates 1.5 reported a mean postoperative glare disability score of 12% after laser posterior capsulotomy in a heterogeneous series of 32 pseudophakic eyes. Until recently, the subgroup with 20/60 or better indoor acuity (Table 3) would have been denied cataract surgery because 20170 or worse Snellen acuity has long been considered the necessary visual deficit. However, that group demonstrated a mean glare disability commensurate with worse than 20/100 acuity in sunlight as determined by the equivalence chart supplied with the Miller-Nadler glare testing system (Figure 3). In the present study, surgery reversed the mean preoperative glare score for the 20/60 or better subgroup to that of 168

the normal population, as was the case for the entire patient population. The results of this investigation therefore reveal that cataract-specific glare disability is discernible and is remediable with current surgical methods under best-case conditions. The present study did not investigate reversal of glare disability in patients with concurrent ocular conditions, such as macular degeneration. Presurgical patient evaluation must carefully distinguish cataracts from other ocular causes of decreased contrast sensitivity or glare disability. Moreover, when glare is the indication, cataract surgery must be carefully performed since less than ideal surgery may worsen the preoperative glare disability; new corneal scars, iris defects, pupillary irregularities, and implant decentration 16 may induce glare symptoms·. REFERENCES 1. Cinotti AA: Evaluation of indications for cataract surgery. Ophthalmic Surg 10(12):25-31, 1979 2. Jaffe NS: Glare and contrast: Indications for cataract surgery. ] Cataract Refract Surg 12:372-375, 1986 3. Abrahamsson M, Sjostrand J: Impairment of contrast sensitivity function (CSF) as a measure of disability glare. Invest Ophthalmol Vis Sci 27:1131-1136, 1986 4. Sjostrand J, Frisen L: Contrast sensitivity in macular disease; a preliminary report. Acta Ophthalmo155:507-514, 1977 5. Arden GB, Jacobson JJ: A simple grating test for contrast sensitivity; preliminary results indicate value in screening for glaucoma. Invest Ophthalmol Vis Sci 17:23-32, 1978 6. LeClaire J, Nadler MP, Weiss S, Miller D: A new glare tester for clinical testing; results comparing normal subjects and variously corrected aphakic patients. Arch Ophthalmol 100:153-158, 1982 7. Holladay JT, Trujillo J, Prager TC, Ruiz RS: Brightness acuity test and outdoor visual acuity in cataract patients. ] Cataract Refract Surg 13:67-69, 1987 8. Hirsch RP, Nadler MP, Miller D: Clinical performance of a disability glare tester. Arch Ophthalmol102:1633-1636, 1984 9. Masket S: Nonkeratometric control of postoperative astigmatism. Am Intra-Ocular Implant Soc] 11:134-137, 1985 10. Arden GB: The importance of measuring contrast sensitivity in cases of visual disturbance. BrJ Ophthalmol62:198-209, 1978 11. Neumann AC, McCarty GR, Steedle TO, Sanders DR, et al: The relationship between indoor and outdoor Snellen visual acuity in cataract patients. ] Cataract Refract Surg 14:35-39, 1988 12. Hirsch RP, Nadler MP, Miller D: Glare measurement as a predictor of outdoor vision among cataract patients. Ann Ophthalmol 16:965-968. 1984 13. Koch DD, Jardeleza TL, Emery JM, Franklin D: Glare following posterior chamber intraocular lens implantation. ] Cataract Refract Surg 12:480-484, 1986 14. Nadler DJ, Jaffe NS, Clayman HM, Jaffe MS, et al: Glare disability in eyes with intraocular lenses. Am ] Ophthalmol 97:43-47, 1984 15. Knighton RW, Slomovic AR, Parrish RK II: Glare measurements before and after neodymium-YAG laser posterior capsulotomy. Am] Ophthalmol 100:708-713, 1985 16. Brems RN, Apple DJ, Pfeffer BR, Park SB, et al: Posterior chamber intraocular lenses in a series of 75 autopsy eyes. Part III: Correlation of positioning holes and optic edges with the pupillary aperture and visual axis. ] Cataract Refract Surg 12:367-371. 1986

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