|
|
|
Appendix A - Results
The following section consists of a small sample of PRK and LASIK studies since these two techniques continue to dominate the field refractive surgery. It should be noted that studies vary considerably in terms of the lasers employed and the average follow up time. The number of eyes examined in each study tends to reduce with follow up time, as a certain number of patients will discharge themselves once they feel their eyes have stabilised. Time undoubtedly gives a better outcome but in some studies the results may be distorted by the small number of eyes considered. Ablation zone diameters vary, with more recent studies tending towards the use of larger treatment zones. It is therefore impossible to state a single value for the predictability and accuracy of a particular technique. Results in chronological order analysed by degree of pre-operative myopia - PRK
|
Authors
|
Number of eyes
|
Follow up period Months
|
Predictability 6/12
|
Predictability 6/6
|
Accuracy ± 1.00D
|
Loss of corrected visual acuity
|
Comments
|
(Gartry et al., 1992)
|
Number of eyes per group 20 9 17 8 8 4
|
Results at 12 months Treatment given: -2.00D -3.00D -4.00D -5.00D -6.00D -7.00D
|
90% 78% 59% 63% 63% 25%
|
55% 56% 47% 50% 25% 0%
|
95% 70% 40% 50% 40% 20%
|
18% overall
15% lost 0.5 or 1 line. 3% lost 2 lines, all from –6D or –7D group
|
Very early study of PRK. Stable refraction by 4 months. Night halos reported by 78% in the early post-operative period due to very small ablation zone (4mm zone) |
Refractive surgery treatments have changed significantly since this early study but it does demonstrate that the treatment of low myopia gives better results.
Results in chronological order analysed by degree of pre-operative myopia - PRK
|
Authors |
Number of eyes |
Follow up period Months |
Predictability 6/12 |
Predictability 6/6 |
Accuracy ± 1.00D |
Loss of corrected visual acuity |
Comments |
||||
|
(Shah et al., 1998) |
3218 eyes
(-1.00D to –11.88D) |
12 months |
94% |
59% |
91% |
0.9% lost 0.3 or more of logMAR acuity |
Very large study. Predictability reduces with increasing myopia |
||||
|
(Tuunanen and Tervo, 1998) Ablation zone: 6mm |
52 eyes
34 eyes
24 eyes |
12 months
-1.50 to -6.00D
-6.10 to -8.00D
8.10 to -11.50D |
88%
68%
68% |
58%
26%
33% |
± 1D ± 0.5D
87% 58%
79% 50%
67% 29% |
Overall 6% lost and 4% gained two or more lines of best-corrected visual acuity. |
Stabilisation of refraction by 3 months
6 months
24 months |
||||
|
(Nagy et al., 2002) |
-1.5 to -6D (90 eyes)
-6.1 to –9D (31 eyes)
-9.1 to –14D (9 eyes) |
12 months |
96%
74%
22% |
78%
26%
0% |
99%
84%
67% |
2.2%
3.2%
22% |
PRK confirmed as unsuitable for the treatment of high myopia |
||||
Results in chronological order for low myopia - PRK
|
Authors |
Number of eyes |
Follow up period (months) |
Predictability 6/12 |
Predictability 6/6 |
Accuracy ± 1.00D |
Loss of corrected visual acuity |
Comments |
|
(McDonald et al., 1999) 6mm zone |
414 spherical <-6.00D)
175 <-6.00D with astigmatism |
12 months |
98%
97% |
72%
62% |
± 0.5: 76% ± 1.0: 94%
± 0.5: 74% ± 1.0: 95% |
1.8% lost 2 lines of visual acuity, 0.3% lost > 2 lines
2.5% lost 2 lines |
Stability of refractive error within 3-6 months. Slightly greater risk of losing visual acuity with astigmatic PRK |
|
(Pallikaris et al., 1999) 6mm zone |
93 eyes
-1.50 to -6.25D
|
12 months |
99% |
70% |
± 0.5: 75% ± 1.0: 93% |
1.0% lost 2 lines of corrected visual acuity |
Stability 3-6 months No significant reduction in contrast sensitivity detected |
Results for the treatment of astigmatism - PARK
|
Author |
Number of eyes |
Follow up time (months) |
% reduction in astigmatism |
Predictability |
Accuracy of mean spherical error ± 1.00D |
|
(Zadok et al., 1998) |
128 eyes -1.0 to –1.5DC -1.75 to –2.5DC -2.75 to –6.0DC |
18 months |
84± 37% 91± 21% 75± 25% |
6/12 or better in 84%
6/6 or better in 49% |
97% overall |
Results in chronological order for hyperopic PRK
|
Authors |
Number of eyes |
Follow up period months |
Predictability 6/12 |
Predictability 6/6 |
Accuracy
|
Loss of corrected visual acuity |
Comments |
|
(Jackson et al., 1998) |
65 +1.00 to +4.00D |
12 months |
72% reached 6/7.5 |
- |
± 0.5: 80% ± 1.0: 98% |
Stabilised between 1-6 months |
|
|
(Nagy et al., 2001) |
800 eyes
<+3.5D
>+3.75D |
12 months |
88%
48% |
76%
34% |
85%
47% |
2 lines lost
2.1%
19% (12% lost 3 lines) |
Stability - 6 months Night glare 18%
41% Hyperopic PRK not as successful as myopic PRK |
|
(Stevens and Ficker, 2002) |
32 eyes
+1.75 to +5.0D
|
12 months |
93% |
70% |
± 0.50D
65%
|
0% |
Contrast sensitivity measured using the Pelli-Robson chart was significant reduced at 12 months post-PRK |
Results in chronological order for myopic LASIK
|
Authors |
Number of eyes |
Follow up period |
Predictability 6/12 |
Predictability 6/6 |
Accuracy ± 1.00D |
Loss of corrected visual acuity |
Comments |
|
(Montes et al., 1999) |
Pre-op MSE -1.5 to -6.0D 168 eyes |
6 months |
100% |
81% |
± 0.50 ± 1D 94% 100% |
1.2% lost 1 line of BCVA (decentred ablation) |
|
|
(Siganos et al., 1999) |
-5 to –10D
-10 to –16D
>-16D |
12 months |
84%
72%
43% |
||||
|
(Balazsi et al., 2001) |
236 eyes -0.5 to –7.0D astig<2.5DC |
6 months |
95% |
82% |
± 0.50 ± 1.0 73% 91% |
0% lost 2 lines 11% lost 1 line
|
Refraction stable by 1 month |
|
(Yang et al., 2001) |
Myopia (-8D) 69 eyes
Myopia astig (9.7D) 74 eyes |
6 months |
94%
93% |
-
- |
88%
85% (90% ± 1DC) |
-
- |
Results for myopic LASEK
|
Authors |
Number of eyes |
Follow up period |
Predictability 6/12 |
Predictability 6/6 |
Accuracy ± 1.00D |
Loss of corrected visual acuity |
Comments |
|
Claringbold 2002 |
222 eyes -1.25D to –11.25D |
4 days 2 weeks 12 months |
84% 98% - |
- - 6/4.5 19% 6/6 63% 6/7.5 18% |
- - - |
- - 0% |
LASIK results for hyperopia
|
Authors |
Number of eyes |
Follow up months |
Predictability 6/12 |
Predictability 6/6 |
Accuracy
|
Loss of BCVA |
Comments |
|
(Goker et al., 1998) |
54 eyes
+4.25 to +8.00
|
18 months |
67% |
15% |
± 1D ± 0.5D 76% 39% |
2 lines or more
6.8% |
At 2 months, 44 % had glare. 9% by 9 months |
|
(Lindstrom et al., 1999) Hyperopia and astigmatism |
Primary hyperopia 46 eyes (+2.5± 0.9D)
Secondary hyperopia 29 eyes (+1.7± 0.8D) |
6 months |
79%
83% |
-
- |
± 1.00D 63%
74%
|
1 eye lost 2 lines of BCVA at 1 month
0% |
Comparative studies between PRK and LASIK
|
Authors |
Pre-operative mean spherical error |
Follow up period |
Predictability 6/6 |
Accuracy
|
Loss of BCVA |
Comments |
|
(Wang et al., 1997)
|
-1.25D to -6.00D
PRK (307 eyes)
LASIK (103 eyes) |
12 months |
72%
83% |
± 1D ± 0.50D
83% 61% 89% 71% |
2 or more lines
4%
1% |
Contrast sensitivity normal by
6-12 months
3 months |
Comparative studies between PRK and LASIK
|
Authors |
Pre-operative mean spherical error |
Follow up period |
Predictability 6/6 |
Accuracy
|
Loss of BCVA / Stability |
|
|
(El-Maghraby et al., 1999) |
30 patients PRK (-4.8± 1.6D)
LASIK (-4.7± 1.5D) |
2 years
|
36%
61% |
-
- |
Within 1 line of pre-operative corrected vision at 3 days 45%
80% |
|
|
(Pop and Payette, 2000) |
PRK (107)
LASIK (107) Range -1.0 to –9.50D |
12 months
|
86%
83% |
Within ± 0.50D 83%
78% |
No eyes in either group lost 2 or more lines of acuity |
|
|
(Stojanovic and Nitter, 2001) |
Myopic astig. 4DC PRK (87) (-4.7± 2.8D)
LASIK (110) (5.4± 2.5D) |
12 months
|
77%
78% |
Within ± 1D 97%
98% |
Loss of 2 or more lines BCVA 0%
0% |
Stable 3 months
1 month
|
|
(Tole et al., 2001) |
Low myopia (-0.5 to –3.0D) PRK (155 eyes) LASIK (97 eyes)
Moderate myopia (-3.1 to -6.0D) PRK (153 eyes) LASIK (217 eyes) |
6 months |
69% 89%
61% 77% |
± 0.5D
87% 94%
78% 73% |
Loss of 2 or more lines BCVA 0% 0%
1.8% 1.0% |
Stable
3 months 1 month
3 months 1 month |