Factors Affecting Long Term Results of Successfully Treated Amblyopia

British Journal of Ophthalmology 1995; 79: 225-228 225

Factors affecting long term results of successfully

treated amblyopia: initial visual acuity and type of Br J Ophthalmol: first published as 10.1136/bjo.79.3.225 on 1 March 1995. Downloaded from amblyopia

Shmuel Levartovsky, Moshe Oliver, Nava Gottesman, Michael Shimshoni

Abstract that is, the visual acuity of the amblyopic eye Aims-The study aimed to assess the before the occlusive treatment was started, and effect of initial visual acuity and type of the type of amblyopia. amblyopia on the long term results of successfully treated amblyopia. Methods-The visual acuity of94 patients, Patients and methods who had been successfully treated for uni- Between 1974 and 1979, 350 children with lateral amblyopia by occlusion ofthe good unilateral amblyopia were diagnosed and eye and foliowed up to the age of 9 years, treated at the outpatient eye clinic of Kaplan was examined 6'4 years, on average, after Hospital, Rehovot. Our earlier report on that cessation of treatment. Patients were study' contains a detailed description of the divided into two groups according to the patients and methods, which is also applicable depth of amblyopia before occlusion to the present work. Treatment consisted only therapy was started: those with visual of occlusion ofthe good eye. In each case, after acuity between 20/60 and 20/100 and those the best visual acuity in the amblyopic eye was with visual acuity of 20/100 or worse. attained, we continued to monitor vision at Results-Deterioration of visual acuity intervals of at least every 3 months for a year. was observed in 42% ofpatients in the first Thereafter, visual acuity was checked during group and in 63% ofpatients in the second the course of a complete eye examination per- group. Their average deterioration, as formed at least once a year until the child was measured by the Snellen chart, was 0 58 9 years old. Whenever necessary - that is, if and 1-54 lines, respectively. The results visual acuity had deteriorated, occlusion of the were also assessed by the division of good eye was reintroduced for as long is it took patients into three groups according to to restore vision to the level previously the type ofamblyopia: strabismic, strabis- attained. mic anisometropic, and anisometropic. Inclusion of a patient in the present long Deterioration of visual acuity occurred in term follow up study was contingent on the fol- http://bjo.bmj.com/ 46%, 79%, and 36% of patients in these lowing criteria being met at the time that three groups, with an average deteriora- amblyopia was diagnosed and during the sub- tion on the Snelilen chart of 0-70, 2-04, and sequent period of treatment and monitoring. 0-64 lines, respectively. (1) Compliance of the child with an age Conclusion-It is concluded that low suitable Snellen chart for the initial visual acu- and strabismic aniso- ity examination. As an exception to this crite- initial visual acuity on October 1, 2021 by guest. Protected copyright. metropic amblyopia are risk factors for rion there were 12 children with unilateral deterioration of visual acuity in the long strabismus who were too young (under 3 years term, following the successful earlier old) at the beginning of the study to be tested treatment of eyes with amblyopia. in this way. We estimated the visual acuity of Department of (BrJ Ophthalmol 1995; 79: 225-228) the amblyopic eye in these children by deter- Ophthalmology, mining the density of the filter required to Kaplan Hospital, Rehovot, affiliated induce a shift of fixation to the squinting or with The Hebrew Occlusion of the good eye is the most widely presumed amblyopic eye. University-Hadassah accepted and probably the most effective (2) An initial visual acuity of 20/60 or worse Medical School, Jerusalem method of treatment for amblyopia. After the in the amblyopic eye. S Levartovsky treatment ends, however, the improved visual (3) Full compliance with the instructions of M Oliver acuity in the amblyopic eye tends to deter- the medical staff during the period of therapy N Gottesman iorate. In an earlier study,' we showed that and follow up. Department ofApplied visual deterioration had occurred in 55°/O of (4) Cessation of occlusion therapy at least Mathematics and successfully treated eyes when measured at the 1 year before the present study. Computer Science, The We;nn long term follow up examination. We also On the basis of these criteria, 157 children Institute of Science, found that the age at which treatment was were eligible for inclusion in this study. Of Rehovot, Israel started did not significantly affect the mean these, 104 (66%) responded to our invitation M Shimshoni extent of deterioration or the mean visual and presented themselves for the long term Correspondence to: acuity in the long term. In the present study we follow up examination. Ninety four children Moshe Oliver, MD, Department of considered two additional variables as possible who were monitored for visual acuity up to at Ophthalmology, Kaplan risk factors and examined their long term least the age of 9 years were included in the Hospital, Rehovot 76100, effects on the deterioration of visual acuity in study. Israel. that had earlier been treated At the term follow the Accepted for publication eyes successfully long up examination, 16 November 1994 for amblyopia: the initial depth of amblyopia - best corrected visual acuity on the Snellen 226 Levartovsky, Oliver, Gottesman, Shimshoni

Table 1 Number (%o) ofchildren in each initial visual attained by the child upon termination of acuity group showing deterioration in visual acuity at the long term follow up examination occlusive therapy. The difference between them was the 'deterioration score', which Br J Ophthalmol: first published as 10.1136/bjo.79.3.225 on 1 March 1995. Downloaded from Initial visual Number of Number ofchildren with reflects the amount of deterioration in visual acuity group children visual deterioration acuity acuity. For each of the groups defined above, 20/60-20/100 45 19 (42) the average amount of deterioration was calcu- 20/100 or less 49 31 (63) Total 94 50 (53) lated by dividing the sum of the deterioration scores by the number of children in the group. The data for each child, including visual chart after refraction was recorded. acuity before occlusion was started, refraction Cycloplegic refraction, when necessary, was ofboth eyes and cover test findings at the com- performed 1 hour after administration of mencement of treatment, best visual acuity at cyclopentolate 1%, twice over a 10 minute termination of treatment, and best visual interval, followed by subjective refraction 1 acuity at the long term follow up examination, week later. Orthoptic and fundal examinations were prepared for computer analysis. The were also performed. Student's t test and the x2 test were used for In order to evaluate the influence of initial statistical evaluation. Results were assumed to visual acuity (the visual acuity before any treat- be significant if p<0 05. ment) or the type of amblyopia on the long term results, the following variables were analysed. Results Of the 94 patients who presented themselves for the long term follow up examination, 45 INITIAL VISUAL ACUITY were male and 49 were female. Their ages at Two groups of amblyopic eyes were defined. the time of the examination ranged from 9'0 to The initial visual acuity was between 20/60 and 20X0 years (mean 13X8 (SD 2A4) years). The 20/100 in the first group (45 patients), 20/200 examination was performed between 1H1 and or worse in the second (49 patients). 9-8 years (average 6-4 (1-8) years) after discontinuation of occlusive treatment. Most of the children (84%) were examined between 4 and TYPE OF AMBLYOPIA 9 years after the treatment was discontinued. Three groups were defined: strabismic ambly- Forty four (47%) of the examinees were opia, where a cover test at the initial examina- found to have maintained the visual acuity tion had demonstrated strabismus of the achieved when occlusion treatment was termi- amblyopic eye, and the spherical equivalent nated, while in 50 (53%) the visual acuity had difference between the eyes was less than 1 00 deteriorated. dioptre (56 patients); strabismic anisometropic where a cover test at the initial

amblyopia, http://bjo.bmj.com/ examination had demonstrated strabismus of INITIAL VISUAL ACUITY AND LONG TERM the amblyopic eye, and the spherical equiva- VISUAL ACUITY DETERIORATION lent difference between the eyes was 1 00 In both groups, some of the patients showed dioptre or more (24 patients); anisometropic deterioration of visual acuity at the long term amblyopia, where a cover test at the initial follow up examination. As shown in Table 1, examination had demonstrated no strabismus of the 45 patients with initial visual acuity

and the spherical equivalent difference between 20/60 and 20/100, 19 (42%) showed on October 1, 2021 by guest. Protected copyright. between the eyes was 1 00 dioptre or more (14 visual deterioration. Of the 49 patients with an patients). initial visual acuity of 20/100 or worse, 31 (63%) showed visual deterioration. This difference between the findings in the two groups is Data analysis and calculation ofvisual statistically significant. acuity deterioration Table 2 presents the mean visual acuity Each line on the Snellen chart was assigned a scores at the beginning and end of occlusive score, as follows: <20/200, 1; 20/200, 2; treatment and at the long term follow up exam- 20/100, 3; 20/80, 4; 20/70, 5; 20/60, 6; 20/50, ination, and the mean deterioration scores of 7; 20/40, 8; 20/30, 9; 20/25, 10; 20/20, 11. We the two groups. Obviously the mean visual used this Snellen score rather than the acuity was initially much higher in the logMAR score; we did so because throughout 20/60-20/100 group, the mean visual acuity the study the visual acuity of the patients was scores of the two groups at the end of the treat- determined by using Snellen charts rather than ment were not statistically different. At the logMAR ones. long term follow up examination, however, the The visual acuity score at the long term mean deterioration score as measured on the follow up examination was compared with that Snellen chart was only 0-58 lines in the

Table 2 Mean visual acuity score (SE) for each initial visual acuity group at the beginning and end ofocclusive treatment and at the long term follow up examination, and mean deterioration scores Mean visual acuity score Mean visual acuity score Mean visual acuity score at the Mean deterioration Initial visual acuity before the start oftreatment at the end oftreatment long term follow up examination score 20/60-20/100 (n=45) 4-51 (0-17) 8-33 (0-16) 7-76 (0 28) 0-58 (0 25) 20/100 or less (n=49) 1-45 (0 07) 8-20 (0-19) 6-76 (0 32) 1-45 (0 30) Factors affecting long term results ofsuccessfully treated amblyopia: initial visual acuity and type ofamblyopia 227

Table 3 Number ofchildren in each type ofamblyopia accordance with the results of other authors,2-8 group showing deterioration in visual acuity at the long term follow up examination who reported that 10-44% of treated eyes maintain their visual acuity at examinations Br J Ophthalmol: first published as 10.1136/bjo.79.3.225 on 1 March 1995. Downloaded from Type ofamblyopia No ofchildren (%) performed 1-10 years after cessation of occlu- (No ofchildren) with visual deterioration sive therapy. Our success rate was high Strabismic amblyopia (n=56) 26 (46) because we included in our study only those Strabismic and anisometropic amblyopia (n=24) 19 (79) children who had shown full compliance with Anisometropic amblyopia (n= 14) 5 (36) the instructions of the medical staff during the Total (n=94) 50 (53) period of therapy and the follow up. In the previous study' we also found that the 20/60-20/100 group compared with 1-45 lines age at which therapy was initiated did not in the other group. Thus, the amount of significantly affect the visual acuity results or deterioration was significantly higher in chil- the extent of deterioration of visual acuity dren who had started treatment with a visual measured at the long term follow up examina- acuity of 20/100 or worse in the amblyopic eye. tion. In the present study we analysed the influence of two additional variables, initial TYPE OF AMBLYOPIA AND LONG TERM VISUAL visual acuity and type of amblyopia, on the ACUITY DETERIORATION extent of long term deterioration of visual Deterioration in visual acuity was seen in all acuity in successfully treated eyes. We found three groups at the long term follow up that in children with an initial visual acuity of examination (Table 3). Of the 56 patients in 20/100 or worse, the mean visual acuity the strabismic amblyopic group, 26 (46%) achieved at the end of occlusive therapy was showed deterioration in vision from that virtually identical with that of children with an attained at termination of treatment. Of the initial visual acuity between 20/60 and 20/100. 24 patients in the strabismic anisometropic Thus, the depth of amblyopia before the start amblyopia group, 19 (79%) patients showed of occlusive therapy had little effect on the deterioration. Of the 14 patients in the aniso- visual acuity results at the end of treatment. metropic amblyopia group, five (36%) showed Thereafter, however, more children whose deterioration. The percentage of patients initial visual acuity was 20/100 or worse tended showing deterioration in visual acuity was to deteriorate and the mean amount of deteri- significantly higher in the strabismic aniso- oration in that group was greater than in metropic amblyopia group than in the other children whose initial visual acuity was two groups (p<0-01). 20/60-20/100. Table 4 presents the mean visual acuity Ching and colleagues9 studied 116 strabis- scores ofthe three groups at the beginning and mic patients with amblyopia treated by occlu- end of treatment and at the long term follow sion of the preferred eye. In 48% of their

up examination. The mean visual acuity scores patients, amblyopia did not recur after cessa- http://bjo.bmj.com/ measured on each of these occasions did not tion of occlusive therapy, while the rest differ significantly among the three groups. required reinstitution of part time occlusion However, the amount of deterioration at the therapy because the amblyopia had recurred. long term follow up examination was signifi- The mean initial visual acuity before the start cantly higher in the strabismic anisometropic of treatment was found to have been signifi- group than in the strabismic group (p<0-01). cantly lower in the group that needed further

Although the anisometropic group also showed treatment. Although the influence of the initial on October 1, 2021 by guest. Protected copyright. less deterioration than the strabismic aniso- visual acuity on the long term visual acuity metropic group, the results are not statistically results was not evaluated in that study, the significant because of the small sample size. authors suggest that the more profoundly amblyopic patients should be followed more closely after therapy is discontinued, since they Discussion are at greater risk of developing recurrent In our previous report,1 which included all of amblyopia. In the present study we showed the patients in the present study, the long term that in patients with deep amblyopia at the results of occlusive treatment for amblyopia beginning of occlusion therapy, the visual were analysed 6-4 years, on average, after the acuity can be expected to deteriorate even treatment was discontinued. We found that the years after discontinuation of therapy. visual acuity attained at the end of occlusive In order to evaluate the influence ofdifferent therapy was maintained in 45% of the success- types of amblyopia on the long term visual fully treated amblyopic eyes. This finding is in acuity results, we defined three groups of

Table 4 Mean visual acuity score (SE) for each type ofamblyopia at the beginning and end ofocclusive treatment and at the long term follow up examination, and mean deterioration scores Type ofamblyopia Mean visual acuity score Mean visual acuity score Mean visual acuity score at the Mean deterioration (No ofchildren) before the start oftreatment at the end of treatment long term follow up examination score Strabismic amblyopia (n=56) 2-91 (0-23) 8-13 (0-18) 7-43 (0-28) 0 70 (0 22) Strabismic-anisometropic amblyopia (n=24) 2-83 (0 37) 8-71 (0-13) 6-67 (0 50) 2-04 (0 46) Anisometropic amblyopia (n=14) 3 07 (0-53) 8-07 (0 37) 7-43 (0-49) 0-64 (0-51) 228 Levartovsky, Oliver, Gottesman, Shimshoni

patients according to the type of amblyopia - strabismus, or strabismic anisometropia were that is, strabismic, strabismic anisometropic, treated by primary occlusion. After termina-

and anisometropic. We found a greater tion ofthe occlusion therapy 85 patients (47%) Br J Ophthalmol: first published as 10.1136/bjo.79.3.225 on 1 March 1995. Downloaded from tendency towards deterioration ofvisual acuity maintained their visual acuity, while in 97 in the strabismic anisometropic group; the patients (53%) the visual acuity deteriorated mean deterioration in that group was about and 'maintenance occlusion' had to be reinsti- three times higher than in the other two tuted. On the basis of the short term visual groups. acuity results, the authors did not find any sig- In a study of 89 patients treated for nificant difference between the two groups strabismic amblyopia and followed to at least 9 with respect to the type of amblyopia. years of age, Scott and Flabetich Dickeyl' The results ofthe present study indicate that reported deterioration of visual acuity in 25% low initial visual acuity and strabismic aniso- ofthe patients by the time they reached a mean metropic amblyopia may significantly affect age of 16 years. In our series, deterioration of the long term of visual acuity results in eyes visual acuity at the long term follow up exami- that earlier were successfully treated for nation was found in 46% of the patients with amblyopia. We suggest that patients with these strabismic amblyopia. The difference between risk factors should be closely monitored for the two sets of results might be explained by visual acuity up to the age of 9 years and the fact that in the former series only 19% of repeatedly treated by patching whenever visual the patients had pretreatment visual acuity of acuity shows deterioration. 20/100 or worse, compared with 52% of the patients in our series. As mentioned above, 1 Levartovsky S, Gottesman N, Shimshoni M, Oliver M. Factors affecting long-term results of successfully treated patients with this low level of pretreatment amblyopia. J Pediatr Ophthalmol Strabismus 1992; 29: visual acuity tend to show greater deterioration 219-23. 2 Sparrow JC, Flynn JT. Amblyopia: a long-term follow-up. in visual acuity at the long term follow up Jf Pediatr Ophthalmol 1977; 141: 333-6. examination. 3 Gregersen E, Rindziunski OT. Conventional occlusion in the treatment of squint amblyopia. A 10-year follow-up. Kutschke et al described visual acuity Acta Ophthalmol 1965; 43: 462-74. results in 124 children with anisometropic 4 Malik SRK, Virdi PS, Goel BK. Follow-up results of occlusion and pleoptic treatment. Acta Ophthalmol 1975; amblyopia."' Only 66 patients had completed 53: 620-5. occlusion therapy; of these, 16 (24%) sub- 5 Aichmair H, Frey RG. Late results in the treatment of amblyopia. Klin Monatsbl Augenheilkd 1968; 153: 214-8. sequently regressed by two or more Snellen 6 Schropfer HD, Meinert K. Late results in amblyopia treat- chart lines. The length ofthe follow up and the ment. Kin MonatsblAugenheilkd 1972; 166: 315-20. 7 Leydecker W, Ricklefs G, Ruhling R. Late results of number of patients who regressed by only one amblyopia treatment. Kin Monatsbl Augenheilkd 1967; line are not recorded. In our study, 14 children 151: 373-6. 8 FlynnJT, CassadyJC. Current trends in amblyopia therapy. with anisometropic amblyopia were evaluated. Trans Am Acad Ophthalmol Otolaryngol 1978; 85: 428-50. Of these, five (36%) showed deterioration of 9 Ching FC, Parks MM, Friendly DS. Practical management of amblyopia. J Pediatr Ophthalmol Strabismus 1986; 23: visual acuity at the long term follow up exami- 12-6.

nation. However, only three of these five 10 Scott WE, Flabetich Dickey C. Stability of visual acuity in http://bjo.bmj.com/ amblyopic patients after visual maturity. Graefes Arch Clin children (21%) showed a deterioration of two Exp Ophthalmol 1988; 226: 154-7. or more Snellen chart lines. 11 Kutschke PJ, Scott WE, Keech RV. Anisometropic amblyopia. Ophthalmology 1991; 98: 258-63. Oster et al12 described a series in which 182 12 Oster JG, Simon JW, Jenkins P. When is it safe to stop patients with amblyopia due to anisometropia, patching? BrJ Ophthalmol 1990; 74: 709-11. on October 1, 2021 by guest. Protected copyright.