Of 76 patients, 16 were excluded from the study (2 patients – due to the impossibility of identifying the scleral spur at AS-OCT, and 14 patients could not come for examination within 4 weeks after treatment). The remaining 60 PAC patients were examined. The comparative characteristics of the results of LPI and LE are shown in Table 1.
The results showed that after the treatment there was a significant difference in IOP decrease in both groups, but the decrease was greater after LE (Table 1). There was no significant decrease in the number of topical hypotensive drops after LPI, while after LE there was a statistically significant difference compared to the baseline.
Verification of similarity of groups 1 and 2
Verification of similarity was performed via testing of two hypothecs. The first one is that group LPI_pre is similar to group LE_pre, and the second one that group LE_pre is similar to group LPI_pre. The tests were conducted using the DD-SIMCA classifier [28] under significance value 0.01. The tests yielded the following values of power of test.
LE_pre versus LPI_pre, empirical = 1; theoretical = 0.99
LPI_pre versus LE_pre, empirical = 1; theoretical = 0.98
These outcomes truly confirm the groups’ similarity.
Building of prediction models for LPI and LE hypotensive effect (ΔIOP)
For both treatment methods, PCR models were built to predict ΔIOP value based on 37 clinical and anatomical parameters described in the METHODS section.
To predict the results of lensectomy, LE-model was built, which uses 2 Principal Components (PC), where the calibration tolerance RMSEC = 0.79, and the validation tolerance RMSECV = 0.87.
Using the model built for group 1, it is possible to predict the outcome of LE to patients in group 2 and compare it with the actual result obtained with LPI.
Figure 1. Result of predicting IOP change in the LPI group if these patients had undergone LE; blue marks are actual delta intraocular pressure (ΔIOP) in the LPI; LPI - laser peripheral iridotomy; red marks - predicted ΔIOP in the LPI group in case of lens extraction taking into account the possible modeling error. Intervals-±3*RMSEP
Figure 1 shows that ΔIOP would be hypothetically significantly higher, except for the patients with goniosynechia, in case of treating LPI patients with LE.
The results of LPI can be predicted in the same way. For this purpose, a PCR model, LPI-model, with 2 PCs is used, where the calibration tolerance RMSEC = 0.39, and the validation tolerance RMSECV = 0.41.
Using this model, it is possible to predict the IOP change that group 1 would have if treated with LPI (Fig. 2).
Figure 2 shows that for most patients in the LE group IOP decrease would be less in LPI, except for some patients with goniosynechia. Figure 3 shows an example of a patient before and after LE, which differed from others in the lensectomy group by the presence of goniosynechia of 60° length in the upper sector. Despite an increase in ACD by 1.166 mm, a decrease in iris curvature by 0.089 mm in the temporal sector and by 0.063 mm in the nasal sector, in IT750 by 0.016 mm and 0.06 mm, respectively, IOP decreased from 24 mmHg to 21 mmHg, and this required the prescription of topical hypotensive therapy (1 drop of Brimonidine 0.2% 2 times a day).
Predicting the results of treatment using LE-model and LPI-model, it is possible to estimate the IOP decrease in each particular case using both methods and then decide whether this is enough for a particular patient.
Choice of a treatment method
Using the methodology presented in section Materials and Methods, the full, Eq. (1) and short, Eq. (2), indicator variables were developed.
The selection of variables was carried out in a standard way [59], in which the importance of a variable was determined by the change in RMSEC and RMSECV values before and after the removal of the variable under study. If both values changed slightly (Fisher's test, p = 0.05), then this variable was removed, otherwise it was retained.
Table 2 shows the coefficients obtained for the short indicator, Ind_Short.
Table 2
Coefficients for Ind_Short
B0 | Gender | IOP | AL | ACD |
16.80 | -0.28 | 0.24 | -0.65 | -2.36 |
Figure 4. Correlation between the full and short indicators, and confirms that the simplified formula given in Eq. (2) can be used in practice. The 0.95 confidence intervals shown in Fig. 4 correspond to the doubled error obtained at the replacement of Ind_Full with Ind_Short. The error value is about 1 that confirms applicability of the simplified criterion Ind_Short in practice
The Ind_Short result shows the quantitative advantage of one method over the other. For example, if Ind_Short = 3, then the IOP decrease in LE will be 3 mm Hg higher than in LPI. If Ind_Short=-3, then it is recommended to use LPI, because the IOP decrease in LE will be 3 mm Hg less than in LPI. The accuracy of estimation of Ind_Short is 1 mm Hg, so the area Ind_Short < 1 is recommended to be considered as a "gray zone", where no method has an advantage.
Conclusions, expert recommendations and outlook in the framework of 3PM
The presented study has confirmed the working hypothesis. The proposed approach follows principles of the paradigm change from reactive medical services (applied to clinically established glaucomatous damage) to predictive, preventive, and personalized medicine (3PM/PPPM) applied to vulnerable groups in the population. Great impacts are expected by improving individual outcomes of preventable glaucomatous damage (concretely PACG) accompanied by positive cost-efficacy of advanced medical services to the population (e.g. in form of innovative screening programs) utilizing predictive disease modelling and treatment algorithms tailored to the personalized patient profile. Essential multi-parametric analysis is implementable by utilizing artificial intelligence (machine learning) in the area.
In the present study, we applied for the first time the quantitative prediction of hypotensive effect of LE and LPI in PAC based on the machine learning methods using two PCR regression models, LE-model and LPI-model. We also proposed an innovative workflow based on Eq. (2) that allows creating an individual treatment plan for each patient taking into account the clinical and anatomical parameters.
Moreover, we proposed a short model for choosing a treatment method, which is not inferior to the workflow in terms of its accuracy. This short model is based only on 4 parameters instead of 37, selected with account of the availability of measurements in routine clinical practice: gender, IOP, AL, and ACD (see Table 2).
Comparing the hypothetical ΔIOP in LE in patients in the LPI group with the actual one, we came to the conclusion that most patients would have a greater IOP decrease (Fig. 1). But comparing the hypothetical ΔIOP in LPI in the LE group, in most cases, a less hypotensive effect would be achieved (Fig. 2). However, in the patients with goniosynechia, both LPI and LE are less effective in reducing IOP (Fig. 3). It is known that lens extraction in the presence of goniosynechia does not lead to a decrease in iridotrabecular contact; therefore, in such cases, lensectomy with goniosinechiolysis is necessary [64].
Thus, the use of the proposed workflow based on machine learning allows choosing a treatment method for an individual patient. In addition, the method gives new possibilities for studying the pathogenesis of IOP increase in primary anterior chamber angle closure. Summarized parameters are presented in the Table 1.
The limitation of the study is that the presented mathematical models are based on relatively small datasets (60 eyes), which can affect the accuracy of modeling. For further application, it is required to increase the sample size and refine the models.
A multi-parametric analysis to predict glaucomatous damage is an essential approach as demonstrated by several studies [65–66]. Moreover, an advanced PPPM approach applied to affected individuals has been proposed for some types of glaucoma such as the normal-tension glaucoma which otherwise healthy vasospastic individuals are predisposed to [67–68]. The key-tool proposed is the multi-level diagnostics. To this end, for the future application of AI in the area it is strongly recommended to consider
-
clinically relevant phenotyping applicable to advanced population screening [69]
-
systemic effects causing suboptimal health conditions considered in order to cost-effectively protect affected individuals against health-to-disease transition [70–73]
-
Clinically relevant health risk assessment utilizing health/disease-specific molecular patterns detectable in body fluids with high predictive power such as a comprehensive tear fluid analysis [74].